Announcing the Merc 888

[Tim Kurcz]

To all Mercury enthusiasts, engine builders, racers, and collectors,

This site has been to quiet lately, so it's time to liven it up. Following the AOMCI show at Mark Suter's, I decided to pull out the stops for 2016. 60372

Feast your eyes and explain what's going on.......

Tim

[Tim Weber]

Ok, I'll bite. You have two blocks opposed. Now the fun begins. Where do the carbs go? How do you get 8 rods on a 44 crank? Interesting!

Tim

[Tim Kurcz]

Ok, I'll bite. You have two blocks opposed. Now the fun begins. Where do the carbs go? How do you get 8 rods on a 44 crank? Interesting!

Tim

One carb (not shown) in front of the turbo. Custom rods, two per journal, for the prototype enables directly opposed cylinders.

Tim60373

[R Austin]

How will you start it. You have no pumping action from the pistons which cancel each other out. No fuel air flow until turbo up.

PS, You could do like the old GMC Diesels and run a positive displacement blower. However I think you will have a problem with 2 rods articulating in opposite directions on the same roller bearings. I think they tried to resolve that same problem in the 30's on the flat head V8's with a full floating shared bearing and it worked so well (not) that they went to individual rod bearings.

[Tim Kurcz]

How will you start it. You have no pumping action from the pistons which cancel each other out. No fuel air flow until turbo up.

PS, You could do like the old GMC Diesels and run a positive displacement blower. However I think you will have a problem with 2 rods articulating in opposite directions on the same roller bearings. I think they tried to resolve that same problem in the 30's on the flat head V8's with a full floating shared bearing and it worked so well (not) that they went to individual rod bearings.

A SeaDoo blower was considered, but not large enough to provide for 88 cubic inches. Also, there was no reasonable way to install a gear drive to deliver the needed 1:7.25 step up.

For the purposes of the proof-of-concept prototype, custom .250" thick rods will be made of 954 aluminum bronze or bronze plated 4140 steel running directly on the crank (with 8:1 fuel/oil ratio.

For starting, two potential methods are envisioned:

1) Lucky: Crank the engine with the electric starter, inject prime through the starboard side (aft bank) port covers, and hope the exhaust gust is enough to spin-up the (undersized) turbo and provide scavenge flow.

2) Not so lucky: Crank the engine with the electric starter, apply airflow through the carb with a leaf blower, and prime the aft bank. This will most certainly provide enough flow to spin-up the turbo and provide scavenge flow.

[Fastjeff57]

I was going to ask how are the needle bearings at each journal kept separate from each other, but they are rolling the same way for each bank, so...

Assembly has gonna be a b*tch!

Jeff

PS: Another fascinating project.

[Tim Kurcz]

I was going to ask how are the needle bearings at each journal kept separate from each other, but they are rolling the same way for each bank, so...

Assembly has gonna be a b*tch!

Jeff

PS: Another fascinating project.

For the prototype, no needle bearings will be used. If they were, there's assembly grease. The crank will be assembled vertically with all 8 pistons and rods, lowered into the aft bank, then the fore bank will be lowered onto it. It will take two people and/or a counterbalanced jib crane.

[Fastjeff57]

Love to watch that being done. Watch it, now, not participate!

You sure have some interesting projects.

Jeff

PS: Could you needle bearings that are captured in the cage (like the later Mercs and some OMCs)? Using sleeve bearings with that violent pull-push action going on would scare me. I appreciate what a Chinese Fire Drill it would be to attempt to use the stock needles in this case.

[Tim Kurcz]

Love to watch that being done. Watch it, now, not participate!

You sure have some interesting projects.

Jeff

PS: Could you needle bearings that are captured in the cage (like the later Mercs and some OMCs)? Using sleeve bearings with that violent pull-push action going on would scare me. I appreciate what a Chinese Fire Drill it would be to attempt to use the stock needles in this case.


Hi Jeff,

Images will be posted as work is completed so all can follow along. This one will look especially cool because of the plugs forward and aft.

There are no sleeve bearings, only bronze on steel and lots of oil. The objective is to learn if the turbo scavenged concept (no reed cages) will even work. My guess is it will.......

Tim

[Fastjeff57]

It works fine with EMD two strokes, You'll have to be careful backfires, however; they would be very violent.

Jeff

[daveswaves]

Looks like fun Tim, at one point I laid two inline 6 blocks together like that and considered the challenges. Fun to think about. Agreed, starting will be a challenge, gonna have to spin it up pretty good to get going. Maybe very retarded timing till it kicks. Be nice to roll up a high rpm starter to the prop end and spin from there.

[Tim Kurcz]

It works fine with EMD two strokes, You'll have to be careful backfires, however; they would be very violent.

Jeff

Of course, consideration was given to the potential for backfires: Consider that two exhaust ports are open at any given time. Having more cross sectional area then the carb venturi, the path of least resistance is likely through the turbo. With the butterfly is open, the beast would likely belch flame from both ends, regardless! If the butterfly is closed, a crankcase explosion would be split between the turbo and intake. In that case it might blow off the silicone elbow connecting the compressor to the diffuser. As operational behavior cannot be determined until actual testing, I decided the complexity and restriction of reed cages in the prototype could wait.

[Tim Kurcz]

Hay Dave,

It's great to hear you considered the 12 cylinder opposed. If the 888 works, go for it!

It is expected the starter should deliver 350 RPM, which should be plenty fast. If not, the circuit will see 24V for some added punch. It's a fun mental and mechanical challenge, all with mostly stock Merc parts (well at least some stock parts).....

[R Austin]

A SeaDoo blower was considered, but not large enough to provide for 88 cubic inches. Also, there was no reasonable way to install a gear drive to deliver the needed 1:7.25 step up.

For the purposes of the proof-of-concept prototype, custom .250" thick rods will be made of 954 aluminum bronze or bronze plated 4140 steel running directly on the crank (with 8:1 fuel/oil ratio.

For starting, two potential methods are envisioned:

1) Lucky: Crank the engine with the electric starter, inject prime through the starboard side (aft bank) port covers, and hope the exhaust gust is enough to spin-up the (undersized) turbo and provide scavenge flow.

2) Not so lucky: Crank the engine with the electric starter, apply airflow through the carb with a leaf blower, and prime the aft bank. This will most certainly provide enough flow to spin-up the turbo and provide scavenge flow.

Tim

I am afraid that the #1 Lucky option will not work.. No matter how hard you spin with the starter you are not pumping fresh air into the cylinders for combustion. The air is just still moving back and forth between pistons.

As far as a common roller or any bearing shared by both rods, unless a floating bearing, will be a problem because the roller will have to skid in one rod. Even though the rods are moving in the same direction their angular relationship to the crank pin is opposite of each other.

Dick

[Tim Kurcz]

Tim

I am afraid that the #1 Lucky option will not work.. No matter how hard you spin with the starter you are not pumping fresh air into the cylinders for combustion. The air is just still moving back and forth between pistons.

As far as a common roller or any bearing shared by both rods, unless a floating bearing, will be a problem because the roller will have to skid in one rod. Even though the rods are moving in the same direction their angular relationship to the crank pin is opposite of each other.

Dick

The chances of the "lucky" solution are slim, but possible. Consider there will be exactly four "pops" from on bank responding to the prime shot. You're correct there is no air motion to recharge the cylinder. However, the turbo was intentionally undersized to allow quicker response to exhaust flow. Won't know until tested.

You might have missed this, but there will be no rollers for the rods for several reasons, one of which is the obvious conflict in motion. Bronze on steel with oil will have to do; long enough to prove the concept.

[R Austin]

I did catch the proto rods, I was just noting for those that thought that a shared roller would work and did not understand the conflict of rod motion.

An interesting concept. There has been numerous time that I have stood 2 blocks face to face and wondered what if. In the mid 80's I was invited to the Merc research building in Oshkosh for a meeting and while there I was asked if I wanted to see a 12 cylinder engine. I though, finally, someone had figured out a way. Only to learn it was 2 1000 or 1250's side by side with a common gear box.

Good luck with the project. I will have a dyno done shortly, should I put a four cylinder bolt pattern on the mounting plate?

Dick

[daveswaves]

Tim

I am afraid that the #1 Lucky option will not work.. No matter how hard you spin with the starter you are not pumping fresh air into the cylinders for combustion. The air is just still moving back and forth between pistons.

As far as a common roller or any bearing shared by both rods, unless a floating bearing, will be a problem because the roller will have to skid in one rod. Even though the rods are moving in the same direction their angular relationship to the crank pin is opposite of each other.

Dick

Dick, I agree that the air in the crankcase will just be shuffling back and forth, however, there will be an intake suction and an exhaust pulse from the non firing piston, not as large as a cylinder that has fired naturally, however , there will be air (and hence the opportunity for fuel) being "pumped" across the top of the piston. If Tim can get it spinning fast enough and light a cyl up the rest should follow. The "air" in question might shuttle in and out of the combustion chamber as well, creating an ever richening mixture until it fires. I will be really lean at the get go unless there is fuel squirted in there to start. The source of the air will be the exhaust side until it fires. Yup lots of opportunity to backfire till it gets going.

[R Austin]

I totally agree that the engine will run once started.

Back in the day, there were many stationary constant RPM power units that ran on just that principle. There were no turbos, blowers or valves of any kind. They were spun and fueled thru intake ports until the depression of the rapid expansion of the escaping gaseous thru the exhaust ports created a depression that allowed the atmospheric pressure to place a new charge in the cylinder. Although very RPM sensitive with just atmospheric pressure.

Again it goes back to staring and keeping it firing long enough to build the exhaust pressure. Back fire is a real problem because on a dead cylinder there is no expansion to create the low pressure on the intake side. The exhaust port opens first and the low pressure point is at the face of the exhaust ports pulling in air from the exhaust side minus any fresh fuel, just the exhaust of an adjacent cylinder.

Like staring a turbine engine, spinning to the right pressures to prevent back fire and over temp.

Again, go for it. Sounds like a fun project to me.

[Tim Kurcz]

It's interesting that the Merc Boxer concept tickled the fancy of others before me. The challenges are many, but with a little luck, the 888 might actually run. If all goes well, it will be fired in February or March. Meanwhile, a few more images for your enjoyment.

The spacer behind the turbo allows for the rear water bypass, and the diffuser covers are taped in place. Both items will be completed this weekend. Stay tuned and keep those ideas coming!
Tim

6037460375

[daveswaves]

Nice little turbo Tim, you might have to split that intake manifold.

[champ20B]

Forget the turbo......you don't need it. Having years of experience around 18 wheelers, and having owned and fixed up a classic International 9670, I can tell you that the venerable Detroit 6v and 8v series two stroke diesels were pressurized by a gear driven roots style blower. Later on the silver series models, a turbo was added, though it only added to the pressurization. It wasn't really necessary to make those engines work well. By that time, an 8V-92 Detroit diesel at 736 cubic inches would make from 435-600++ HP at 2100 RPM. It was a giant V-8 at 92 cubes per cylinder. Just some interesting stuff......

Basically, what you can use is a roots style mini compressor/blower for a motorcycle engine. I think they exist if I'm not mistaken. That will give compression in the crank case without valves and is immediate and mechanically direct.

[Tim Kurcz]

Forget the turbo......you don't need it. Having years of experience around 18 wheelers, and having owned and fixed up a classic International 9670, I can tell you that the venerable Detroit 6v and 8v series two stroke diesels were pressurized by a gear driven roots style blower. Later on the silver series models, a turbo was added, though it only added to the pressurization. It wasn't really necessary to make those engines work well. By that time, an 8V-92 Detroit diesel at 736 cubic inches would make from 435-600++ HP at 2100 RPM. It was a giant V-8 at 92 cubes per cylinder. Just some interesting stuff......

Basically, what you can use is a roots style mini compressor/blower for a motorcycle engine. I think they exist if I'm not mistaken. That will give compression in the crank case without valves and is immediate and mechanically direct.

Indeed, there are many challenges and potential improvements for the opposed 888. As an engine of this type may never have been built before, a tall learning curve curve is expected. But, you've got to start somewhere. My thoughts are to start simple (and inexpensive), to determine if further investment is warranted.

Among the many interesting comments: Dicks recollection about valveless generator engines (presumably 2-stroke) is very interesting: I've never heard of such a thing. And, Detroit Diesel 2-strokes are near/dear to my heart. As a suppler to DD in the 70's and 80's I became very familiar with the 53, 71, 92, and 149 series engines (cubic inches per cylinder for those who don't know). In fact, I built a two stroke, four valve Cosworth-Johnson using a similar principle (with crankcase scavenging) in the 1990's.

So far as splitting the diffuser and intake tract, this may be needed in the future, IF the engine behaves itself. And while a blower would be preferred for its volumetric scavenging, I had a spare small frame Garrett on the shelf.

All super-trick ideas aside, my larger concerns are survivability of the skinny little rods and lightweight crankshaft. Success is defined as successful/repeatable starting and idle performance, with light tank time on a test wheel to follow. My dream is that operation will be stable enough to push a boat around for 10-15 minutes without blowing chunks.

Tim

[Fastjeff57]

I too have 'history' with Detroit Diesels; EMD railroad engines in my case. And they aren't puny 92 cube per cylinder, glorified 'lawn mower' engines: Think 645 and 710 cubes PER cylinder, and up to 20 cylinders! Now, that's an engine!

Turbocharging a two stroke has a hidden benefit in that the exhaust back pressure it creates keeps the inlet charge from blowing out the exhaust system. Supercharging doesn't do that.

Jeff

PS: The thought of that crankcase, without vacuum/ pressure pulses going on all the time, is fascinating!

[Tim Kurcz]

I too have 'history' with Detroit Diesels; EMD railroad engines in my case. And they aren't puny 92 cube per cylinder, glorified 'lawn mower' engines: Think 645 and 710 cubes PER cylinder, and up to 20 cylinders! Now, that's an engine!

Turbocharging a two stroke has a hidden benefit in that the exhaust back pressure it creates keeps the inlet charge from blowing out the exhaust system. Supercharging doesn't do that.

Jeff

PS: The thought of that crankcase, without vacuum/ pressure pulses going on all the time, is fascinating!


Now those are some BIG engines! Were they two strokes like the Detroit?

[daveswaves]

Hook your shop vac to the turbo exhaust while you are cranking it, the shop vac will get out of the way as soon as it starts (lol) Seriously though, it would be nice to be able to have a two stage starting process, dc motor coupled to the turbo shaft, spin it up throttle closed, then crank and open throttle. Just thinking out of the box.

[Tim Kurcz]

Hook your shop vac to the turbo exhaust while you are cranking it, the shop vac will get out of the way as soon as it starts (lol) Seriously though, it would be nice to be able to have a two stage starting process, dc motor coupled to the turbo shaft, spin it up throttle closed, then crank and open throttle. Just thinking out of the box.

Hi Dave,

Yes, the shop vac is always possible. Actually, my leaf blower has a suction adapter, and may be used - LOL! Also, electric turbos were researched first (see videos on youtube). Generally, a high power electric motor replaces the exhaust turbine. Aside from the obvious problem marinizing electric motors on outboard engines, compressor output is limited. I'd given thought to adding one to the fore bank for starting only, but the weight, complexity, and cost ruled out the exercise for the prototype.

What I really need help with is an ignition system, preferably battery CD or HEI (for reasonable $$$). The least cost method is twin, conventional, belt driven, (petite) VW Type 1 distributors & two coils. The next method is an under the flywheel crank trigger battery CD system based on readily available marine parts (available but pricey). Finally, I'm considering building my own with four inductive sensors, coupled to four GM HEI ignition modules, firing four Siamese ignition coils.

Do any of you engine or ignition guru's have any experience with an inductive HEI?

Tim

[R Austin]

Tim

As long as you are considering building new rods, think about the rod configuration in the Allison and the radial engine with a master rod and a link rod.

Dick

[Tim Kurcz]

Tim

As long as you are considering building new rods, think about the rod configuration in the Allison and the radial engine with a master rod and a link rod.

Dick

You mean like this?

[Tim Kurcz]

Tim

As long as you are considering building new rods, think about the rod configuration in the Allison and the radial engine with a master rod and a link rod.

Dick


Regarding ignition: How do you fire the twin plugs on your Looper Beast?

[R Austin]

That's the setup on the rod. Obviously with a little more pin and a bearing in the rod link.

The beast is just the standard ADI ignition with the primary coil feed connecting 2 standard coils in series. Not sure yet if that may be the problem with the ignition/fuel issue. I do not think it is but will not know for sure until I get it on the dyno.

[Tim Kurcz]

That's the setup on the rod. Obviously with a little more pin and a bearing in the rod link.

The beast is just the standard ADI ignition with the primary coil feed connecting 2 standard coils in series. Not sure yet if that may be the problem with the ignition/fuel issue. I do not think it is but will not know for sure until I get it on the dyno.

The standard Mercury rod throws offer precious little room for a master/link or blade/fork con rod setup. Top guided .450" thick rods fit between .535" counter-weight cheeks. It's attractive to use a larger pivot pin for the master/link, and it allows retention of crank pin needle bearings, but precious width must be consumed by some form of pin retention (possibly C- or E-rings).

Because of the space limitation, I'm leaning toward separate .250" thick "knife blade" rods, eliminating the bearings in favor of more beef, even though offset loading will induce bending stress.

All said, rod design is not yet determined. A few prototype designs will be built over the weekend.

Thanks for your thoughts on the ignition as well. Good luck sorting out the Looper Beast!

[daveswaves]

Dick, you may be better off firing the two coils in parallell rather than in series. The scr in the switch box is more than capable of providing current to the new lower resistance. Both in series is limiting your current flow to 1/2 of what the coil normally sees, that means smaller magnetic field and much smaller spark. Just a thought. Tim, the GM hei modules will work well, they use an inductive type trigger using reluctance. Assign some numbers to the main and secondary bank so we can think about firing order on both sides. Waste spark is one way to go, 4 coils sparking every 180 degrees. You could use a merc 4 cyl trigger and related linkage to fire the GM HEI module, just have to figure out how to sequence the modules. Normally the rotor looks after that for you. A standard GM 8 cyl hei with coil in cap would do everything for you, Good up to 10000 rpm, nicely matched. All you would have to do is adapt a merc pulley to the end of the distributor where the oil pump drive is, not too hard. The vehicle ones have a fairly chunky cap, Malory makes a narrower version that is pretty slick. I am willing to expand further as questions arise.

[R Austin]

Dick, you may be better off firing the two coils in parallell rather than in series. The scr in the switch box is more than capable of providing current to the new lower resistance. Both in series is limiting your current flow to 1/2 of what the coil normally sees, that means smaller magnetic field and much smaller spark. Just a thought. Tim, the GM hei modules will work well, they use an inductive type trigger using reluctance. Assign some numbers to the main and secondary bank so we can think about firing order on both sides. Waste spark is one way to go, 4 coils sparking every 180 degrees. You could use a merc 4 cyl trigger and related linkage to fire the GM HEI module, just have to figure out how to sequence the modules. Normally the rotor looks after that for you. A standard GM 8 cyl hei with coil in cap would do everything for you, Good up to 10000 rpm, nicely matched. All you would have to do is adapt a merc pulley to the end of the distributor where the oil pump drive is, not too hard. The vehicle ones have a fairly chunky cap, Malory makes a narrower version that is pretty slick. I am willing to expand further as questions arise.

Dave you may be right. That has been my concern since the first test run as it acted like an ignition problem, fouled plugs or way to rich. The testing on the ignition indicated that in parallel that only the plug, coil, or condition with less resistance would fire. Could then the lower voltage from the coil in series be cured with conventional and smaller gaps be a solution.

Tim
Do you have a new email address. If yes email me so I can return on your email.

Thanks.

[daveswaves]

Dave you may be right. That has been my concern since the first test run as it acted like an ignition problem, fouled plugs or way to rich. The testing on the ignition indicated that in parallel that only the plug, coil, or condition with less resistance would fire. Could then the lower voltage from the coil in series be cured with conventional and smaller gaps be a solution.



Thanks.

In theory, all of the coil(s) primaries should be the same resistance so should not favor one over the other, poor connections may be a problem. Agreed if the secondary resistances are different due to condition then you might loose a spark, smaller gaps might sort it out. Cant remember which coils you used on the looper beast. If was the stock merc coils with rubber jacket there are two things that could be messing you up. The ceramic core shoe tends to crack, causing weak spark, also, the other end of the coil wire is simply squished by the rubber to make contact with the mounting plate. Poor contact is the death of high voltage systems.

[Tim Kurcz]

Dick, you may be better off firing the two coils in parallell rather than in series. The scr in the switch box is more than capable of providing current to the new lower resistance. Both in series is limiting your current flow to 1/2 of what the coil normally sees, that means smaller magnetic field and much smaller spark. Just a thought. Tim, the GM hei modules will work well, they use an inductive type trigger using reluctance. Assign some numbers to the main and secondary bank so we can think about firing order on both sides. Waste spark is one way to go, 4 coils sparking every 180 degrees. You could use a merc 4 cyl trigger and related linkage to fire the GM HEI module, just have to figure out how to sequence the modules. Normally the rotor looks after that for you. A standard GM 8 cyl hei with coil in cap would do everything for you, Good up to 10000 rpm, nicely matched. All you would have to do is adapt a merc pulley to the end of the distributor where the oil pump drive is, not too hard. The vehicle ones have a fairly chunky cap, Malory makes a narrower version that is pretty slick. I am willing to expand further as questions arise.

Thanks Dave; here we go:

The front bank is numbers 1-2-3-4, and the rear bank is 5-6-7-8 from top to bottom, respectively. The Mercury firing order is 1-3-2-4 (alternating pairs spaced 90 degrees apart). So, cylinders 1 and 6 fire, then 3 and 8, then 2 and 5, and finally 4 and 7.

The issues are the same as Dick's Looper Beast. The need to fire two plugs, full power, simultaneously. http://www.superchevy.com/how-to/45618-inductive-cd-ignitions-basics/ explains where the twin (Siamese) coils designed for wasted spark systems fire one plug positive to negative and consumes 85% of the energy, while the wasted spark plug fires negative to positive and gets only 15% available energy, but fires fires only in a rarified atmosphere (not firing under compression). This solidifies the argument for twin indendent ignition systems. Your thoughts?

[daveswaves]

Something else to think about, coils have polarity, when you put them in series you should do it like batteries, +-+- etc/ If you are putting them in parallel then both positives should be joined and both negatives should be joined. If you mix up the polarity the coils will fight each other.

[Aeroliner]

Nice project Tim,
Well getting fuel and lube around might be a bit of an issue. One thing you might consider is to make a regular dry sump lube system with an oil pump. Reed block could stay in without the reeds and stops. The center main bearing carrier could be machined to allow the oil to drain down where it cam be pumped our. Exterior oil line to spray nozzle's should due the trick to keep the rotating system and the back side of the piston lubricated. For starting you can install a primer system to spray fuel into the intakes. With an electric pump this would be easy. This assumes that the carb will be in a pressure box.

Good luck,
Alan

[GHMiller]

Tim, check out Electromotive Ignitions. I run a V8 HPV-1 model on my mod 44 merc and I ground one post on each of the four coils for my four cylinder set up. But for your eight cylinder setup it might just work. I power it with a 5ah trailer breakaway battery all weekend on one charge. (14vdc).

[champ20B]

Here is a feasible suggestion for rod design.....

Just machine a gully through one rod end. Then narrow down the other rod end to fit and ride in between the other rod's gully or valley, whatever to call it. This way you will have complete circle end rods. You could also machine the space between the crank arms to make the crank pin longer to use two narrowed rods side by side. You will have to fill in and re-thread the rod bolt holes for something smaller and placed differently. It could work for a low output or medium performance set up.

[Fastjeff57]

..."(On the EMD railroad locomptive engines) Now those are some BIG engines! Were they two strokes like the Detroit? "

Yes, but they use a 4 poppet valve head with OHV for the exhaust. Make roughy 4,000 hp. at 900 rpm.


Aircraft engines (like the Rolls Royce Merlin V-12) used the blade and fork design rods successfully (obviously!) They had the room for it on the journal, however. Gonna be a tough deal to make work reliably.

Jeff

[Tim Kurcz]

Nice project Tim,
Well getting fuel and lube around might be a bit of an issue. One thing you might consider is to make a regular dry sump lube system with an oil pump. Reed block could stay in without the reeds and stops. The center main bearing carrier could be machined to allow the oil to drain down where it cam be pumped our. Exterior oil line to spray nozzle's should due the trick to keep the rotating system and the back side of the piston lubricated. For starting you can install a primer system to spray fuel into the intakes. With an electric pump this would be easy. This assumes that the carb will be in a pressure box.

Good luck,
Alan

Hi Alan, et al,

Here goes on Q&A:

1) Great thought was given to crank/rod oiling. For this reason, single point mixture entry was chosen. This forces mixture to travel from the front bank diagonally through the crankcase to feed the rear bank. An 8:1 fuel-oil ratio will slobber the internals. As noted, reed cages (bronze) will be installed without reeds, and the center main will be perforated to encourage further inter-cavity mixture migration.

2) Automotive crank trigger inductive (or capacitive discharge) systems are designed to fire one coil each, in sequence. Discussion with MSD and Pertronix (so far) suggests that firing two different cylinders simultaneously requires twin parallel systems (like aircraft or top fuel engines). Both are fine solutions, but bulky and expensive. Instead, a test rig will determine if four simple prox. sensors will fire four GM HEI modules through eight coils, or eight HEI modules firing eight coils, etc. I not successful, twin belt-driven VW Type I distributors will be considered.

3) As pointed out, RR Merlin-style blade and fork style rods are far and away the most elegant solution to support directly opposed cylinders. Yes, the existing Mercury crank can be altered at great trouble and expense to accommodate custom rods, only to compromise balance and torsional rigidity. Better yet, a press-pin crank could be assembled with beefier journals, and one-piece fork & blade rods running on separate needle bearings.

This is an experiment to determine if a turbo scavenged, open crankcase two-stroke will behave sufficiently well to consider future development. It's convenient that 60+ year old Mercury are plentiful to use as a base (they also happen to look bad-***!). If the engine actually runs and behaves itself, my thoughts are offset rods, separate pumping chambers, and loop scavenging........


6038860389

Tim

[Tim Kurcz]

Better images for examination & comment.603916039260393603946039560396

[hydroplay]

I remember seeing a pic of experimental Merc opposed 4 built with 2 cylinder KG-Mark 20 type blocks when they were contemplating 40 hp engines types. I can't remember where it was- maybe in the Kiekhaefer book. No details on the internal details but obviously the in-line 4 became preferable.

[Tim Kurcz]

I remember seeing a pic of experimental Merc opposed 4 built with 2 cylinder KG-Mark 20 type blocks when they were contemplating 40 hp engines types. I can't remember where it was- maybe in the Kiekhaefer book. No details on the internal details but obviously the in-line 4 became preferable.

Actually, Karl wrote a patent app. in 1948 (granted in April 3, 1951) for an opposed four based on two KF-7 (pre-MK 20) blocks. A somewhat crude cutaway sketch shows offset blocks with a four throw crank providing crankcase compression, all wrapped under a "green pumpkin" cowling. Claims granted were for modular assembly designed to reduce the cost of manufacturing. Google "Kiekhaefer opposed 4 cylinder" and you'll find a pdf for interesting reading.

My guess is packaging challenges made the in-line more practical.

[Fastjeff57]

You mean this one? One assumes there were four separate crank throws hiding in there, but...

Jeff

[Tim Kurcz]

You mean this one? One assumes there were four separate crank throws hiding in there, but...

Jeff

Very cool: It's great to see that at least one copy was built! Do you know there the engine is now?

Tim

[Fastjeff57]

Sorry, but I have no other info on this other than it was called a KE-9.

Jeff

[Bill Van Steenwyk]

FastJeff:

Do you have any info on the motor in the second photo down on the left side?

Looks to be a different motor. Another way to get 4 cyls, but a different motor.

[Fastjeff57]

Gonna have to disappoint you again. Been collecting 'experimental' Mercs for years, but all I have are these photos.

Jeff

[Fastjeff57]

Then there's a Merc V-8...

Jeff

[Aeroliner]

Hi Tim,
I have been looking at my Electromotive ignition system we developed and run on our 4 cylinder Mercs and I believe you can use the box with the dual output coils. It should be very easy to setup in that 2 cylinders will fire at the same time. If you need info let me know and I will E mail the Tec Manual to you. Doug has done a number of them.

Alan

[Tim Kurcz]

Hi Tim,
I have been looking at my Electromotive ignition system we developed and run on our 4 cylinder Mercs and I believe you can use the box with the dual output coils. It should be very easy to setup in that 2 cylinders will fire at the same time. If you need info let me know and I will E mail the Tec Manual to you. Doug has done a number of them.

Alan

Thanks for the input everybody. The 888 project has captured the imaginations of many, with great suggestions to overcome specific problems, and a fantastic array of Mercury prototype images. Please keep them coming.

This week the master & link rod concept will be developed further in hopes of using factory needle bearings and centerline loading for the slave piston. You're questions/recommendations will be answered in turn.

Tim

[Krazy Karl]

I think the master/link rod arrangement would be the best way to go. I worked on radial aircraft engines when I retired. I worked in a shop that overhauled/restored all makes of radial engines. A very practical solution to compact multi cylinder engine. The biggest negative factor is a very large frontal area, not at all aerodynamic. Not a factor here. Very durable but may not be suitable for high horsepower/rpm applications.

We had one come in that had a piston seize which caused the rod to break taking out the two adjacent cylinders. The owner was able to fly it several miles back to the airport. He had a hard time seeing through the oil on the windshield.
kk

[Tim Kurcz]

I think the master/link rod arrangement would be the best way to go. I worked on radial aircraft engines when I retired. I worked in a shop that overhauled/restored all makes of radial engines. A very practical solution to compact multi cylinder engine. The biggest negative factor is a very large frontal area, not at all aerodynamic. Not a factor here. Very durable but may not be suitable for high horsepower/rpm applications.

We had one come in that had a piston seize which caused the rod to break taking out the two adjacent cylinders. The owner was able to fly it several miles back to the airport. He had a hard time seeing through the oil on the windshield.
kk

Thanks Karl,

The radial engine master/link concept is truly an elegant solution, and my personal favorite (as a fellow pilot). However, to fit the link between .535" counterweights on a .450" thick rod means the link "blade" will be only .120" thick. This translates to 64,500 psi loading in a .500" diameter pin (if it will fit the package space) using 40% surface contact. Of course, counterweights might be removed to allow use of a wider/larger diameter pivot, but at the expense of crankshaft balance.

By comparison, individual .250" thick rods transfer only 17,000 psi to the crank journal at 40% contact. The downside here is lack of roller bearings, offset loading on the rod, and small cap retention fasteners. Clearly, there's more development to go.......

Decisions, decisions.

[Krazy Karl]

I know this part was going to be a major problem using a master/link rod design. It seems all options have some kind of weak point. Certainly an interesting project to say the least. I will be following this project as it progresses. Gives me something to think about during brain idle times.
kk

[Fastjeff57]

This is totally irrelevant (but some might find it interesting): Years ago I was working on converting RR loco diesels to run on liquefied natural gas. We did 4 locos: two EMD two strokes, and two GE four strokes. The way the gas was injected into the four strokes eventually caused 7 of its 16 cylinders to self destruct: 6 on one side and one on the other bank. It puzzled the HELL out of us why it happened like that until someone mentioned the obvious: The motor used a master and slave rod system. I forget which side lost the 6 cylinders, but I'll bet it was the slave rod side that had slightly different action at TDC.

Jeff

[Tim Kurcz]

Hi Tim,
I have been looking at my Electromotive ignition system we developed and run on our 4 cylinder Mercs and I believe you can use the box with the dual output coils. It should be very easy to setup in that 2 cylinders will fire at the same time. If you need info let me know and I will E mail the Tec Manual to you. Doug has done a number of them.

Alan
Apologies to all as memory suggested that the ignition concept
was published, but a review of posts found it was not! See the sketch below:60411

BRF didn't like the ignition upload, so here it is explained: The Mercury firing order is 1-3-4-2. The 888 is comprised of two banks of MK58A cylinder blocks; situated fore and aft. The front bank cylinders are 1-2-3-4, the rear bank cylinders are 5-6-7-8. With all eight cylinders tied to the same four pin crank, cylinders fire in pairs as follows: 1 & 6, then 3 & 8, then 2 & 5, then 4 & 7.

Does this make more sense now?

Tim

[John Schubert T*A*R*T]

Hi Tim,

Using the MK58/Merc 500 crank, did you fabricate new rods; did you just grind the originals to fit within the journal & then re-harden them;what do you plan to put between the crank pin area of the rods, some sort of thrust bearing? These questions probably are secret at this time but I'm very curious

[Tim Kurcz]

Hi Tim,

Using the MK58/Merc 500 crank, did you fabricate new rods; did you just grind the originals to fit within the journal & then re-harden them;what do you plan to put between the crank pin area of the rods, some sort of thrust bearing? These questions probably are secret at this time but I'm very curious

Hi John,

No secrets - I need all the help I can get with this one. The rods will most likely be machined from centrifugally cast 954 aluminum bronze (about 85,000 PSI), riding directly on the crank journal with lotsa oil. IF 4140 steel is selected (about 95,000 PSI), it will be bronze plated for lubrication, again with lotsa oil. My concern is that when the bronze wears through, it's steel on steel. Bronze is my choice because it's very close to steel in tensile and can't wear through.

Rod images shown on prior posts shows a 4-screw aluminum prototype with an .884" bore (.002" clearance to the crank .882" journal). It took three tries to develop a shape that would swing without hitting structure. In fact, cap end screws have to be placed inboard for swing clearance. Rod end screws are only .090" away to maintain the same 2.000" Mercury rod width. Though hard to see, screw heads overlap.

The limiting factor of these "knife blade" rods is the .250" section which limits screw size to #8-32. In fact, the standard #8-32 head is .270" diameter and must be ground to .240" to allow a little clearance!

Tim

[89HST]

Why not send the crank out to dave eden, have him machine the crank pin area wider and re heat treat it? That would allow you a little more area for bearing surfaces on the dual rod idea.

[Tim Kurcz]

Why not send the crank out to dave eden, have him machine the crank pin area wider and re heat treat it? That would allow you a little more area for bearing surfaces on the dual rod idea.

Modifying the crank is certainly possible, along with staggering the blocks 1/4" to negate the offset. But, the objective is to assemble with the least invasive change to learn if the engine will start easily (enough) and behave itself. If it does, further expense is warranted. Remember there is zero cylinder pumping........

[Yellowjacket]

Not to throw cold water on the approach, but you need to think seriously about some kind of bearing and a much bigger area for the pin on the master rod. The stress in the pin is high and the contact stress is high even for something that isn't moving. No lubrication is going to stand up to that kind of pressure. You are going to bottom out the joint and it's going to gall and wear in no time at all. Cut away part of the counter weights to get some width and you can support proper size pin and bearing. You can make a new rod cap and make it out of high strength material (a high strength steel or nickel alloy like Inco 718). The full complement bearings that are used by Mercury are obsolete in many ways, but they can take really high loading and in this case that's not a bad thing. The stock wrist pins are good for over 9000 rpm in modified motors when proper lubricated so there is the capability to take a lot more load so I'd start with the stock small wrist pins and needle bearings and look at that kind of sizing if you want to run this at any speed over idle.

[Tim Kurcz]

Not to throw cold water on the approach, but you need to think seriously about some kind of bearing and a much bigger area for the pin on the master rod. The stress in the pin is high and the contact stress is high even for something that isn't moving. No lubrication is going to stand up to that kind of pressure. You are going to bottom out the joint and it's going to gall and wear in no time at all. Cut away part of the counter weights to get some width and you can support proper size pin and bearing. You can make a new rod cap and make it out of high strength material (a high strength steel or nickel alloy like Inco 718). The full complement bearings that are used by Mercury are obsolete in many ways, but they can take really high loading and in this case that's not a bad thing. The stock wrist pins are good for over 9000 rpm in modified motors when proper lubricated so there is the capability to take a lot more load so I'd start with the stock small wrist pins and needle bearings and look at that kind of sizing if you want to run this at any speed over idle.

Agreed.

While the radial engine master/link concept is truly an elegant solution, it simply won't work because of excessive loads as stated. If the crank journal were to be widened, balance is adversely affected and worse, crank rigidity is compromised. The only decision, without investing boatloads of cash, is to use two narrow rods running in the same journal. They will be adequate for proof of concept. I'll be very pleased if this engine lasts one hour.

Tim

[Fastjeff57]

Let us remember that the downward (towards BDC) force of one piston is being offset by the compression force working on the other (going to TDC). Now, if the master/ slave rod concept is used, these forces will go through the rod, from one piston to the other, instead of through the rod bearing to get there.

A vote for the master/ slave rod concept!

Jeff

PS: Damn but this is an interesting project!

[Krazy Karl]

PS: Damn but this is an interesting project![/QUOTE]

I agree, totally.
kk

[Tim Kurcz]

PS: Damn but this is an interesting project!

I agree, totally.
kk[/QUOTE]


Not to worry, rod options are still open. Saturday I'm mocking-up another master-link combo to determine if it will swing with a 1/2" diameter pin.

[F-12]

Tim.......Why couldn't you take 2 mercury rods, toss the end caps and bolt them together on one journal of the crankshaft? Seems that since you already have bearings to fit the rods, it would be a much simpler fix than redesigning an already good part.

[Tim Kurcz]

Tim.......Why couldn't you take 2 mercury rods, toss the end caps and bolt them together on one journal of the crankshaft? Seems that since you already have bearings to fit the rods, it would be a much simpler fix than redesigning an already good part.

Anything that easy can't possibly work..... or it would have been done before. Back to back rods cannot be made to assemble, let alone rotate.

[F-12]

After thinking about what I wrote, that thought entered my mind. Sorry about that.......

[Tim Kurcz]

After thinking about what I wrote, that thought entered my mind. Sorry about that.......

No problemo...... It was my first thought, too. LOL!

[Fastjeff57]

Didn't think that out to clearly, eh Charley!

Jeff

[Yellowjacket]

The "forked" rod approach won't work with long needels. The angular rotation is different between the two rods and that would cause skidding on the more lightly loaded bearing. To make the forked rod approach work you'd need separate needles for each rod. Not impossible but pretty messy to try to put together unless there was a caged bearing set (you would need 3) one for each of the 'outside" forks and one for the middle rod.

I think the master rod approach is probably the best, but as I said above you've got to get the contact pressure down to somewhere near reality for the bearings to work.

Remember too, that if you make a new rod cap you need to make it out of a high strength steel that can be hardened to RC of more than 58 or so if you want the bearing races to last for more than a few minutes. Not a big deal, but certainly part of the process.

To make this work you need to take the front cover off of a 44 and with the crank in place see how much room there is between the rods and the sides of the bores at their closest position. That sets the size you can have in that area and so long as you stay within that dimension (or plan on modifying the block with the slave rods in it so that what you come up with will fit.

[Yellowjacket]

I'm sure way back when that Mercury would have done something like this if it would have been workable. If there was a way to make this work they wouldn't have made "double" 6's with gearing just below the engines....

Oh yea, and if you get it to work why stop with a 8,,, just think about what a flat 12 would sound like making about 300 hp.... Makes my ears perk up just to think about it...

[Tim Kurcz]

The "forked" rod approach won't work with long needels. The angular rotation is different between the two rods and that would cause skidding on the more lightly loaded bearing. To make the forked rod approach work you'd need separate needles for each rod. Not impossible but pretty messy to try to put together unless there was a caged bearing set (you would need 3) one for each of the 'outside" forks and one for the middle rod.

I think the master rod approach is probably the best, but as I said above you've got to get the contact pressure down to somewhere near reality for the bearings to work.

Remember too, that if you make a new rod cap you need to make it out of a high strength steel that can be hardened to RC of more than 58 or so if you want the bearing races to last for more than a few minutes. Not a big deal, but certainly part of the process.

To make this work you need to take the front cover off of a 44 and with the crank in place see how much room there is between the rods and the sides of the bores at their closest position. That sets the size you can have in that area and so long as you stay within that dimension (or plan on modifying the block with the slave rods in it so that what you come up with will fit.


Yellowjacket and others correctly point out the problem with two rods on one set of journal bearings - the differential skidding issue was recognized immediately. As there is insufficient space between the counterweights to allow two sets of needles and divider, the backup plan was to use two bronze rods per journal riding directly on the crank (well oiled). Not an ideal solution, but would have lasted sufficiently long to prove the engine concept.

Given the obvious flaws with the "skinny" rods, and overwhelming interest in the aircraft like master-link rod (my first choice), the concept was re-visited. To make the design more compact, the joint was inverted: The blade will now be integral to the rod cap; a matching fork rod will straddle the blade. Swing tests conducted last night prove the interference zones are rod slots on intake and exhaust side of the aft block (block with the master-link).

Crude dimensions taken from the modeling clay indicate there should be sufficient swing room with some careful grinding. Even better, subsequent layout math suggests there is room for a .312" wide caged needle bearing in the blade section if counterweights are machined for clearance. A hardened steel cross-pin, possibly as large as .500" Dia. would become the link rod bearing surface.

Beginning tonight, a revised rod cap (blade) an link rod (fork) will be machined, and assembled for fitment in the blocks. Cross fingers! 60445

[F-12]

Didn't think that out to clearly, eh Charley!

Jeff

Just thought it out too quickly............working on a John Deere..........anything can enter your mind........

[Ron Hill]

I'm not "HIGH JACKING" this tread, but it reminds of Chad's Yama-Merc. Chad ran P.R.O.P. Tour 1997 and with the death of Jim Hauenstein we quit boating racing at the end of that season.....Funny, I dreamed about Jimmy last night. He and I did our fair share of beer drinking over the years. In my dream, Jimmy WAS supposed to go buy some beers...but he never came back. I think there could be some symbolism here, then again, Jimmy frequently disappeared when it was his turn to buy beers.

It was either 1999 or 2000 that Chad got the idea to build a V-6 Yamaha using a Mercury crankshaft. .055 oversize Mercury pistons fit the Yamaha V-6 bore perfectly. Ted Zahorski, who was Yamaha's National Service Master gave use two blocks. Chad line bored the block and put two powerheads together. He bought the Overton's old Hoffman that Fred Bowden owned. We had ever thing ready and it would not start. I called Randy Pierson, in Avon, Minnesota to ask for help. Randy was leaving the next day to come help us at San Diego.

Randy said, "The gad damn thing is never going to work, as a Yamaha is 90 degree block and a Mercury is a 60 degree."

So, I call Ted at Yamaha. He hangs on the line for a LONG TIME......He finally said, "It won't work as it will go Rum, bum, bum Rum."

I call Randy, he says, "I've got a brand new S-3000, powerhead, I'll bring it with me and I trade you some props...."

We had fun at the race, but that was our last P.R.O.P Tour effort.

Where is this 888 Project going to run? Or is it just a "PROJECT"?

[Tim Kurcz]

I'm not "HIGH JACKING" this tread, but it reminds of Chad's Yama-Merc. Chad ran P.R.O.P. Tour 1997 and with the death of Jim Hauenstein we quit boating racing at the end of that season.....Funny, I dreamed about Jimmy last night. He and I did our fair share of beer drinking over the years. In my dream, Jimmy WAS supposed to go buy some beers...but he never came back. I think there could be some symbolism here, then again, Jimmy frequently disappeared when it was his turn to buy beers.

It was either 1999 or 2000 that Chad got the idea to build a V-6 Yamaha using a Mercury crankshaft. .055 oversize Mercury pistons fit the Yamaha V-6 bore perfectly. Ted Zahorski, who was Yamaha's National Service Master gave use two blocks. Chad line bored the block and put two powerheads together. He bought the Overton's old Hoffman that Fred Bowden owned. We had ever thing ready and it would not start. I called Randy Pierson, in Avon, Minnesota to ask for help. Randy was leaving the next day to come help us at San Diego.

Randy said, "The gad damn thing is never going to work, as a Yamaha is 90 degree block and a Mercury is a 60 degree."



So, I call Ted at Yamaha. He hangs on the line for a LONG TIME......He finally said, "It won't work as it will go Rum, bum, bum Rum."

I call Randy, he says, "I've got a brand new S-3000, powerhead, I'll bring it with me and I trade you some props...."

We had fun at the race, but that was our last P.R.O.P Tour effort.

Where is this 888 Project going to run? Or is it just a "PROJECT"?


Hi Ron,

Just like my Cosworth Johnson, OMC six-packs, OMC turbos, Merc 444 & 666, the Merc 888 Turbo will be build just for fun.... With any luck at all, it will power a hydro next summer, then be shown at Mark Suter's next fall.

60446

Please keep your ideas and stories coming.

Tim

[Tim Kurcz]

604476044860449
I'm sure way back when that Mercury would have done something like this if it would have been workable. If there was a way to make this work they wouldn't have made "double" 6's with gearing just below the engines....

Oh yea, and if you get it to work why stop with a 8,,, just think about what a flat 12 would sound like making about 300 hp.... Makes my ears perk up just to think about it...

Eight cylinders is plenty enough to start. If the prototype behaves itself, an opposed 12 would be even more of awesome....

Meanwhile, images show four contact points on the "slave" block. There is less room available than thought available for swing, unless the block is modified - a possibility. I'm attempting to design a 3/8" minimum, possibly a 1/2" pivot pin. The cutaway cap shown required eight round trip assemblies before clear rotation was achieved. Now that maximum dimensions have been determined, engineering can begin.

[GHMiller]

Tim, this project is quite interesting to say the least. Are you planning to leave the ports stock or are there plans for them later down the road?

[Tim Kurcz]

Tim, this project is quite interesting to the least. Are you planning to leave the ports stock or are there plans for them later down the road?

Thanks for your interest. The plan is to run stock porting. Raising exhaust ports reduces total volume available for combustion. And though widening is possible, forced induction makes up for lots of porting ills.

Rods and crank will be weak links. Kiekhaefer did a great job of optimizing these engines: Nothing is beefier than needed. Should the rods make it, double duty on the crank journals will likely take them the crank out quickly.

Even so, it's a very cool project.

[Yellowjacket]

Rods and crank will be weak links. Kiekhaefer did a great job of optimizing these engines: Nothing is beefier than needed. Should the rods make it, double duty on the crank journals will likely take them the crank out quickly.

Even so, it's a very cool project.

Actually the rods and bearing have a good bit of margin. In modified motors these parts are spun to much higher speeds than a stock motor. When you realize that stress and loads are a speed squared function, where a 20% increase in speed is a 44% increase in stress and loads, then the stock rods and bearings are actually pretty robust. In addition the big end forces peak at bottom dead center, and these are actually lower with a piston pushing the other way, so big end forces are higher, but they aren't twice as high. If big end bearing forces were a problem you could always go to titanium rods.

At some point you're going to have to get rid of the stock rod bolts and get something just a bit longer so that the area on the cap is a bit bigger in the area between the head of the rod bolt and the bearing area. That's a nasty stress concentration area and that's a failure location for sure.

Also think about making mods or getting rid of the stock crank. You need more area to hold onto the slave rod and I fear that there just isn't enough room to fit in what you need to do with thin area between the counterweights.

[Tim Kurcz]

Actually the rods and bearing have a good bit of margin. In modified motors these parts are spun to much higher speeds than a stock motor. When you realize that stress and loads are a speed squared function, where a 20% increase in speed is a 44% increase in stress and loads, then the stock rods and bearings are actually pretty robust. In addition the big end forces peak at bottom dead center, and these are actually lower with a piston pushing the other way, so big end forces are higher, but they aren't twice as high. If big end bearing forces were a problem you could always go to titanium rods.

At some point you're going to have to get rid of the stock rod bolts and get something just a bit longer so that the area on the cap is a bit bigger in the area between the head of the rod bolt and the bearing area. That's a nasty stress concentration area and that's a failure location for sure.

Also think about making mods or getting rid of the stock crank. You need more area to hold onto the slave rod and I fear that there just isn't enough room to fit in what you need to do with thin area between the counterweights.

Indeed, the Merc crank and rods have performed well in naturally aspirated stock, mod, and even alky applications for decades. Compared to stock however, the forced induction 888 offers the potential for a quadrupling of power. Load and heat dissipation become big issues. Obviously, the stock Merc crank wouldn't last long under those conditions regardless of rod configuration.

Your last paragraph sums up the issue: There isn't enough room to build a robust master-slave rod system without removing counterweight material. This is what is I meant by design optimization. Mercury engineers did an astounding job minimizing space, weight, and materials, all on paper without calculators or computers. That they didn't leave enough space to build the 888 must have been and oversight - LOL!

Given architecture limitations yet to be fully explored for the master-link concept, the question becomes: Which rod/crankshaft configuration offers the greatest chance for proof of concept success in the 888?

The "skinny" aluminum-bronze rods fit within existing architecture and require no modification to the crankshaft. They are limited by (four) #8-32 cap retention screws, offset loading, and lack of needle bearing support. Simplicity is gained at the expense of centerline thrust, cap retention, and friction reduction.

The "master-link" Mercury based rods, bearings, and bolts maintain integrity of the time-proven design. They will require machining .090" (+/-) from each counterweight, and machining and/or adding material to allow swing clearance. Centerline thrust and roller bearing support is retained at the expense of crankshaft balance and strength.

Given these parameters; which would you choose?

[Fastjeff57]

Then there's the balance issue. Those counterweights were designed for one rod and piston, not two. Furthermore, unlike a true opposed piston engine, the 888's pistons move together instead of in opposite directions. That means the 888's rods and pistons will experience DOUBLE the 'throwing forces' (had to call it something). This could be trouble as well.

But it's sure worth trying! Love to be there when she fires up!

Jeff

[Yellowjacket]

Hmmm

Quadruplng the power by FI is probably not the best idea... When I was in high school 40 years ago I read the book "The Sports Car, it's Design and Performance" by a Brit named Colin Campbell. One line in that book stuck in my head and it's been there ever since...

"As a means of finding the weakest point in an engine, supercharging has no equal..."

True then, even truer today with the advent of "turn the screw" boost and turbochargers that any fool can crank in more boost than is prudent...

Crank and rod forces are primarily speed driven and I think that you can live with that, but in order to get more power cylinder pressures are going way up and these engines are close to detonation as they sit. If you go to higher cylinder pressures you're going to have to reduce compression ratio and really, a deflector arrangement isn't the best thing since it is not only heavy, it results in a big chunk of hot metal sticking up into the combustion chamber that is a detonation anchor...

Gordon Gecko is quoted as saying that "Greed is Good", but if you get too greedy you're going to find lots of things that are going to lead to a trail of broken bits and that tends to take the fun out it....

If you get to maybe 150 hp total you've done as much as the basic architecture is good for. More than that and you're going to start breaking lots of things and sticking pistons and that takes the fun out of it.

I think you will probably have to bite the bullet and make a new crank. These cranks aren't that robust in the first place for reasons I'll discuss below, so it may be something that you will have to do in the long run anyway, and doing it up front may be the price of doing business... These cranks can bend and it would be an advantage to better support them with additional bearings in what was the reed blocks. Jeff was concerned about offset imbalance, but remember that the two cylinder pairs would actually not need counterweights if the crank was robust enough to transfer the forces between the two adjacent cylinders. Another way of saying it is that each crank pair is a mirror image of each other and the forces balance, but the forces are huge. Racers have for years trimmed the counterweights in the mod classes without issues, but as noted, the unbalanced forces in the crank goes up and that's something that you could readily calculate and see how much bending you have in the crank.

What I was thinking about was the fact that the reeds are now unnecessary and the area that was used for the reed blocks and for reed travel is now open for crank counterweights. This would also help address the issue that Jeff brought up in that the offset weight is increased. I don't know how you were going to get the charge into the case, but the reeds are unnecessary now so you can use that area for a new crank. Similarly for the middle bearing, while you don't want to reduce the bearing itself, there is area off of the centerline that could be trimmed back. Reed travel (per the APBA tech manual) is .185 (max) which when added to the thickness of the reed stop is close to a quarter of an inch. With the reed blocks gone you could replace them with a bearing support that is bigger in diameter than what is there now. The stock crank diameter was minimized in that area to minimize leakage and get intake area. You want the opposite, a bigger diameter and a bearing support there so that's another reason to make a new crank.

You'll have to look at the existing cases and see what you can fit inside and how it can all work with an additional bearing between the cylinders, but by using the space were the reeds were you may be able to get the area you need to fit a decent design of master/slave rod arrangement and that may get you over the biggest hurdle and let you break it in other areas sooner.

[daveswaves]

Anything that easy can't possibly work..... or it would have been done before. Back to back rods cannot be made to assemble, let alone rotate.

Tim, I still have trouble visualizing why they wont rotate if the cyls are directly opposed. Pretend its just a two cyl opposed with a single throw and common rod joined at the journal, why wont it rotate.??

[Tim Kurcz]

Hmmm

Quadruplng the power by FI is probably not the best idea... When I was in high school 40 years ago I read the book "The Sports Car, it's Design and Performance" by a Brit named Colin Campbell. One line in that book stuck in my head and it's been there ever since...

"As a means of finding the weakest point in an engine, supercharging has no equal..."

True then, even truer today with the advent of "turn the screw" boost and turbochargers that any fool can crank in more boost than is prudent...

Crank and rod forces are primarily speed driven and I think that you can live with that, but in order to get more power cylinder pressures are going way up and these engines are close to detonation as they sit. If you go to higher cylinder pressures you're going to have to reduce compression ratio and really, a deflector arrangement isn't the best thing since it is not only heavy, it results in a big chunk of hot metal sticking up into the combustion chamber that is a detonation anchor...

Gordon Gecko is quoted as saying that "Greed is Good", but if you get too greedy you're going to find lots of things that are going to lead to a trail of broken bits and that tends to take the fun out it....

If you get to maybe 150 hp total you've done as much as the basic architecture is good for. More than that and you're going to start breaking lots of things and sticking pistons and that takes the fun out of it.

I think you will probably have to bite the bullet and make a new crank. These cranks aren't that robust in the first place for reasons I'll discuss below, so it may be something that you will have to do in the long run anyway, and doing it up front may be the price of doing business... These cranks can bend and it would be an advantage to better support them with additional bearings in what was the reed blocks. Jeff was concerned about offset imbalance, but remember that the two cylinder pairs would actually not need counterweights if the crank was robust enough to transfer the forces between the two adjacent cylinders. Another way of saying it is that each crank pair is a mirror image of each other and the forces balance, but the forces are huge. Racers have for years trimmed the counterweights in the mod classes without issues, but as noted, the unbalanced forces in the crank goes up and that's something that you could readily calculate and see how much bending you have in the crank.

What I was thinking about was the fact that the reeds are now unnecessary and the area that was used for the reed blocks and for reed travel is now open for crank counterweights. This would also help address the issue that Jeff brought up in that the offset weight is increased. I don't know how you were going to get the charge into the case, but the reeds are unnecessary now so you can use that area for a new crank. Similarly for the middle bearing, while you don't want to reduce the bearing itself, there is area off of the centerline that could be trimmed back. Reed travel (per the APBA tech manual) is .185 (max) which when added to the thickness of the reed stop is close to a quarter of an inch. With the reed blocks gone you could replace them with a bearing support that is bigger in diameter than what is there now. The stock crank diameter was minimized in that area to minimize leakage and get intake area. You want the opposite, a bigger diameter and a bearing support there so that's another reason to make a new crank.

You'll have to look at the existing cases and see what you can fit inside and how it can all work with an additional bearing between the cylinders, but by using the space were the reeds were you may be able to get the area you need to fit a decent design of master/slave rod arrangement and that may get you over the biggest hurdle and let you break it in other areas sooner.

Fear not, Yellowjacket; I realize the crank train would never stand up to the 150-200 HP that the turbo is capable of delivering, and don't intend to run the engine anywhere near that hard. The factory crank & rods aren't strong enough (let alone the modified master-link pieces), the deflector pistons & combustion chamber would simply melt, and the lack of cylinder pumping may severely limit power anyway. Remember that the objective is to build a running proof of concept, zero crankcase pumping engine from Mercury parts. Given the obvious limitations, and those yet to be discovered, the project may not be overly practical, but it's still bad ***!

Tim

PS: You are correct that space now occupied by reed cages and center main could most certainly be used for a custom crankshaft & rods. I'm just not willing to chunk out $10K for something that might not work..........

[Tim Kurcz]

Tim, I still have trouble visualizing why they wont rotate if the cyls are directly opposed. Pretend its just a two cyl opposed with a single throw and common rod joined at the journal, why wont it rotate.??

Hi Dave,

Considerer that he Merc 4-cyl crank is two pairs of opposed crankpins spaced 90 degrees apart. So, two of the piston/rod combinations will actually assemble in-line (but not rotate). As you're lowering the upper block while attempting to stuff the second pair, you realize pistons are hanging way outside the blocks because the opposed rods don't swing because of the solid beam rod. Does this help?

Tim

[hydroplay]

Tim, I still have trouble visualizing why they wont rotate if the cyls are directly opposed. Pretend its just a two cyl opposed with a single throw and common rod joined at the journal, why wont it rotate.??

Its pretty easily to visualize why this wouldn't work. Imagine just two opposed cylinders with the rod you desire. It will fit together when the cylinder pair is at TDC-BDC and the rod is straight between both piston wrist pins. Now imagine it at some intermediate position where the rod would be at some angle to the cylinder bore. That works fine for a single cylinder but then add an opposing cylinder and a straight rod and you see the 2nd rod wrist pin would be pointing thru the cylinder wall instead of at the piston wrist pin. You could assemble an opposed twin like this but it wouldn't rotate. Two 4 cylinder opposed Mercs couldn't be assembled.

[Fastjeff57]

Ah, horse feathers! Slap the thing together, using your most favorable design (without breaking your budget)m and see what happens. Use a leaf blower to supply the air, the master rod design, and really modest power settings. If it runs, fine; if not, well... It sure was an interesting idea!

In engineering, it's called "Proof of concept".

Jeff

[Tim Kurcz]

Ah, horse feathers! Slap the thing together, using your most favorable design (without breaking your budget)m and see what happens. Use a leaf blower to supply the air, the master rod design, and really modest power settings. If it runs, fine; if not, well... It sure was an interesting idea!

In engineering, it's called "Proof of concept".

Jeff

Hi Jeff,

By Jove, you've got it. After about 12 hours design, mockup, and re-design work, I've settled on the master-link rod concept. Now it's a tussle between pivot joint options: 1) A .375" steel pin riding in a tiny full complement drawn cup needle bearing, 2) A .500" steel pin riding on a bronze plated bore, or 3) A .500" bronze pin riding in steel bore. I'm leaning toward a 1/2" pin.....

Assuming the proof of concept actually runs, only moderate power/RPM would be used: It would be fun to drive the little beast just to see the looks on peoples faces (and get a few pics, of course). If it behaves itself, a more robust version might follow.

Tim

[Fastjeff57]

And video, Tim, video!

Jeff

[Tim Kurcz]

And video, Tim, video!

Jeff

You betcha the will be video......

Tim

[Yellowjacket]

Hi Jeff,

By Jove, you've got it. After about 12 hours design, mockup, and re-design work, I've settled on the master-link rod concept. Now it's a tussle between pivot joint options: 1) A .375" steel pin riding in a tiny full complement drawn cup needle bearing, 2) A .500" steel pin riding on a bronze plated bore, or 3) A .500" bronze pin riding in steel bore. I'm leaning toward a 1/2" pin.....

Assuming the proof of concept actually runs, only moderate power/RPM would be used: It would be fun to drive the little beast just to see the looks on peoples faces (and get a few pics, of course). If it behaves itself, a more robust version might follow.

Tim

Go with the rolling element brg.. With a half inch pin and not much length you'll seize it in no time without full pressure lubrication (or even with full pressure lubrication). If you keep the speed down you may not have a long bearing life, but it won't seize up after a few minutes... Remember that the angular rotation is all you have to deal with and the full complement bearing can take a good bit of load.

[Tim Kurcz]

Go with the rolling element brg.. With a half inch pin and not much length you'll seize it in no time without full pressure lubrication (or even with full pressure lubrication). If you keep the speed down you may not have a long bearing life, but it won't seize up after a few minutes... Remember that the angular rotation is all you have to deal with and the full complement bearing can take a good bit of load.

Your proposal makes sense: It's the relatively small .375" pin that has be nervous. But then again, it only needs to run an hour under light power.....

[daveswaves]

Hi Dave,

Considerer that he Merc 4-cyl crank is two pairs of opposed crankpins spaced 90 degrees apart. So, two of the piston/rod combinations will actually assemble in-line (but not rotate). As you're lowering the upper block while attempting to stuff the second pair, you realize pistons are hanging way outside the blocks because the opposed rods don't swing because of the solid beam rod. Does this help?

Tim

Thanks Tim and Hydroplay, that got my brain working.

[daveswaves]

http://thekneeslider.com/the-hossack-engine-a-square-piston-two-stroke/

As long as we are talking about out of the box thinking Mr Hossack has an idea too.

[Tim Kurcz]

http://thekneeslider.com/the-hossack-engine-a-square-piston-two-stroke/

As long as we are talking about out of the box thinking Mr Hossack has an idea too.

Kinda cute; a cross between a Wankel and reciprocating two stroke.

[daveswaves]

Novel port blocking with the rocking piston.

[Techteam]

Tim what you need to get some pumping for starting is one of these



electrically driven supercharger. link that to the exhaust turbine side h
as a built in clutch so as the exhaust pressure rises the electric motor is disconnected.

[Techteam]

the nice thing about the merlin or other aero engine conrod arrangement is the master rod creates a bearing journal for the second rod.

[daveswaves]

Tech Team your attachments are not showing up.

[Tim Kurcz]

the nice thing about the merlin or other aero engine conrod arrangement is the master rod creates a bearing journal for the second rod.

Answering a few questions:

1) I looked at the electric turbo right until the price tag appeared, then, thought about building one myself. Not knowing if the engine would even run, I opted for the leaf blower option.

2) The Merlin/Allison blade & fork rods run on a common crank pin; nice pics - thanks. If money were no object, I'd have built a custom crankshaft and used a true blade & fork to keep the cylinders directly opposed.

3) The design I'm using is very similar to a radial engine master and link. For those not familiar, the radial engine has only one crank pin. The "master" rod rides on the single pin; "link" rods are connected to the master.

4) Unfortunately, there is no room for a conventional radial master- link design. The custom pieces are identified as "blade" and "fork" for convenience only.

[Techteam]

3) The design I'm using is very similar to a radial engine master and link. For those not familiar, the radial engine has only one crank pin. The "master" rod rides on the single pin; "link" rods are connected to the master.

Yes sorry I forget that I don't worry about the cost of things because our customers have deep pockets.

[Tim Kurcz]

Yes sorry I forget that I don't worry about the cost of things because our customers have deep pockets.

If/when the concept is proven, a more robust design might be built.

Nice pics of the corn cob! Are the Merlin and R-4360 your pieces?

[Techteam]

My pictures but not my engines, guess we were just interested in the same way of doing things. If anybody is ever in Munich the Deutsch museum has a fantastic collection of cutaways. I've learned when designing engines you can learn a lot from the past. Trying to convince people to buy something new or revolutionary is almost impossible.

[Fastjeff57]

Been there! Fantastic museum!

Jeff

[Tim Kurcz]

It's been hectic lately, and progress has been slow. Critical parts acquisition includes a Merc 1000 flywheel with 9-1/2" ring gear from Steve Wheeler, and a Merc 500 starter motor from Doug Kay. You may notice the BRF demonstrating bugs again entering text right to left, so it's unlikely images will upload. If not, you'll soon see the starter motor and flywheel fitted. Work will be slow during the Christmas period, but next will be the rods.

6047660477

[Fastjeff57]

Hose clamped in place! Sure, why not.

Jeff

[Tim Kurcz]

The hose clamp is an excellent fixturing device that enabled easy bracket mockup. Once the spanner is welded, a cross bolted support will be added to the starters inner bottom stud. The clamp will likely remain to provide additional clamping. Oh yeah; it's very convenient there's an extra set of fuel pump pads....

60478

[Fastjeff57]

Very clever, as is this entire project!

Jeff

[Krazy Karl]

60486

Master Rod

60488

Crank Shaft


60487

Continental 220 Radial Engine

Some pictures to show those who have never seen the insides of a 40's radial engine. These are still used commercially in crop dusters.

kk

[smittythewelder]

Tim, the part of this link that might be of immediate interest is halfway down the page, on the left:

http://crosleyautoclub.com/EngineTree/Crosley_Eng_Tree-3.html

[Tim Kurcz]

Tim, the part of this link that might be of immediate interest is halfway down the page, on the left:

http://crosleyautoclub.com/EngineTree/Crosley_Eng_Tree-3.html

Fantastic! The concept has been built before; at least in 4-stroke form.

Excellent image contributions, all. Please keep them coming!

Tim

[Powerabout]

Tim, the part of this link that might be of immediate interest is halfway down the page, on the left:

http://crosleyautoclub.com/EngineTree/Crosley_Eng_Tree-3.html
I like that, a stock rod with new cap and one custom rod.

[Tim Kurcz]

I like that, a stock rod with new cap and one custom rod.

Basically, that's what is planned for the 888. A prototype will be built welding a "blade" to the existing Mercury rod cap. The matching "fork" will be machined into a custom link rod. These will be constructed to complete swing testing and clearancing of the opposing block.

[Powerabout]

Basically, that's what is planned for the 888. A prototype will be built welding a "blade" to the existing Mercury rod cap. The matching "fork" will be machined into a custom link rod. These will be constructed to complete swing testing and clearancing of the opposing block.
Merry Christmas Tim
how hard is it to make a rod for an outboard?
I have never seen the process?
Thinking of the 8 rare rods in my v8

[Yellowjacket]

Basically, that's what is planned for the 888. A prototype will be built welding a "blade" to the existing Mercury rod cap. The matching "fork" will be machined into a custom link rod. These will be constructed to complete swing testing and clearancing of the opposing block.

Careful with welding on the rod cap. If you weld on it make sure that it is round when you are done. Welding will distort the cap and also anneal the rod cap (that is a forged part) so it will be softer than it was before the welding. Also the inner surface of the rod cap is hardened to work as a bearing surface. Grinding too much on that surface will also soften it and it won't last long under the contact stress... These rod caps are generally opened up for clearance but doing that only takes about a half thousandths off of the bore (or about a quarter of a thousandth off of each side) so there isn't much of a problem with taking too much of. But if you take off three thousandth's from a surface you are likely to be getting through the hardened surface and the surface will spalling off in short order.

If you change the bearing clearance by a half a thousandth then that's a lot, so you will probably have to clean it up when you are done welding.

[Tim Kurcz]

Careful with welding on the rod cap. If you weld on it make sure that it is round when you are done. Welding will distort the cap and also anneal the rod cap (that is a forged part) so it will be softer than it was before the welding. Also the inner surface of the rod cap is hardened to work as a bearing surface. Grinding too much on that surface will also soften it and it won't last long under the contact stress... These rod caps are generally opened up for clearance but doing that only takes about a half thousandths off of the bore (or about a quarter of a thousandth off of each side) so there isn't much of a problem with taking too much of. But if you take off three thousandth's from a surface you are likely to be getting through the hardened surface and the surface will spalling off in short order.

If you change the bearing clearance by a half a thousandth then that's a lot, so you will probably have to clean it up when you are done welding.

Most outboard rods are forged steel, copper plated (carburize mask), rough machined (removes copper plate from intended surfaces), assembled, carburized, then finish machined (ground/honed). Copper plated areas are soft, only the bearing/wearing surfaces are hardened. To prove this to yourself, clamp a spare rod in a vice, apply torsion with a pipe wrench, and watch it twist without shattering.

For the proto rod, copper will be removed from the cap, the extension blade tig welded in place with the rod assembled and fully torqued. Following, the journal bore will be honed round and to size, and the pivot bore will be machined.

After swing fitting, the proto rod and cap bearing surfaces will be Brinnell tested. If there is no significant difference, the 888 might be run with welded rods. If the difference is unacceptable, custom rod caps will be machined, and the bearing surface will be carburized, honed, etc.

Side note: It might surprise you to know that mod outboard racers have been honing .002" - .0025" from the big end bores for many years. This procedure followed Mercury's change from .880" to .882" crank pins. It allowed rods to survive race conditions without overheating (bluing).

[Powerabout]

why do they copper plate?
Do you need to freeze them to break the cracked cap types?
does the big end need to be harder to do this?

[smittythewelder]

After welding and BEFORE re-machining, you might consider shot-peening and even cryo-treating the rod . . .

[Yellowjacket]

Most outboard rods are forged steel, copper plated (carburize mask), rough machined (removes copper plate from intended surfaces), assembled, carburized, then finish machined (ground/honed). Copper plated areas are soft, only the bearing/wearing surfaces are hardened. To prove this to yourself, clamp a spare rod in a vice, apply torsion with a pipe wrench, and watch it twist without shattering.

For the proto rod, copper will be removed from the cap, the extension blade tig welded in place with the rod assembled and fully torqued. Following, the journal bore will be honed round and to size, and the pivot bore will be machined.

After swing fitting, the proto rod and cap bearing surfaces will be Brinnell tested. If there is no significant difference, the 888 might be run with welded rods. If the difference is unacceptable, custom rod caps will be machined, and the bearing surface will be carburized, honed, etc.

Side note: It might surprise you to know that mod outboard racers have been honing .002" - .0025" from the big end bores for many years. This procedure followed Mercury's change from .880" to .882" crank pins. It allowed rods to survive race conditions without overheating (bluing).

While the outer surfaces of the rod are copper plated to mask the carburizing process (so that the rod isn't hard and brittle on the surfaces that are under tension) and only allow the bearing surfaces to be carburized, the rods aren't in the fully annealed condition. The rods are strong due to the forging process and subsequent heat treat, but not brittle, as they would be if they were carburized all over. Doing a Brinell test on a regular (unwelded) rod and comparing the hardness with the modified end cap is a good plan. If you knew the alloy you could heat treat the cap after welding and it would be as strong as it could be.

I'm well aware that these rods are commonly honed out to increase the bearing clearance. I had a set done when I built my 44 in motor to APBA stock specs. But when you hone these rods to take about .001 inches off of the surface (x 2 to open the diameter up by .002). That doesn't go through the carburized hard surface. I don't know how deep the carburization is taken in these rods. Since the purpose of carburizing is done to make the surface hard enough to be a bearing surface it most likely isn't deep. Deeper carburizing wouldn't serve any purpose so I doubt it's very deep. The only way to know is to grind the rod and then do a hardness test on it, or get a copy of the rod print where it is probably noted on the drawing. My point was that you don't want to grind off too much of the bearing surface or you will risk having a soft bearing surface and that will deteriorate quickly under the contact stress of a rolling element bearing. If you only have to take off .003 from a surface (3 x what you take off in the process of loosening up the rod clearance) you are probably fine.

[smittythewelder]

Lots of rods get re-sized not to change the clearance dim but just because they get stretched to an oval shape after lots of running; for instance, the rods in a lot of 20H and 55H engines are out-of-round, if the rebuilder happens to mike the big ends. A good auto machine shop can probably save them, if you bring a specification.

[Tim Kurcz]

Lots of rods get re-sized not to change the clearance dim but just because they get stretched to an oval shape after lots of running; for instance, the rods in a lot of 20H and 55H engines are out-of-round, if the rebuilder happens to mike the big ends. A good auto machine shop can probably save them, if you bring a specification.

Thanks all for your thoughts on rods. Welder extraordinaire Chris Razor suggests clamping the rod to a 6"-8" long cylindrical aluminum heat sink. He says it will absorb heat from the blade welding process, which will reduce the annealing affect on case hardened bearing surfaces. The plan is to:

Turn the heat sink, build a blade, and weld. Once complete, the cap and rod will be Rockwell tested. If C-scale hardness is mid-50's, welded rods may be used for the prototype. As pointed out, grinding of surfaces and precision honing the bore round and to size must be accomplished following. A local machine shop uses a piston pin hone to accomplish the task.

A couple more weeks will have data. Cross fingers!

Tim

[Fastjeff57]

Was reading about the Napier-Halford aircraft engines used in WW II. The first one--a 16 cylinder H type with four opposed banks of four cylinders and two crankshafts--used the master/ slave rod concept. With a square 3.5 inch bore and stroke, their rated rpm was 4,000--very high for a continuous duty aircraft engine. After suffering rod failures at the crank end, the following engines (24 cylinder H type) went to blade and fork design and were trouble free.

Jeff

[Tim Kurcz]

Was reading about the Napier-Halford aircraft engines used in WW II. The first one--a 16 cylinder H type with four opposed banks of four cylinders and two crankshafts--used the master/ slave rod concept. With a square 3.5 inch bore and stroke, their rated rpm was 4,000--very high for a continuous duty aircraft engine. After suffering rod failures at the crank end, the following engines (24 cylinder H type) went to blade and fork design and were trouble free.

Jeff

Great research! It's always great to learn from the experience of others. While the blade and fork rod would most certainly be a stronger and more elegant arrangement, there is no room for luxury on the petite Merc crankshaft.

[Fastjeff57]

I understand. I'm hoping blade and forks won't be necessary, at least for the trial motor.

(Rubbing hands together with glee) I can't wait to see her run!

Jerf

[Tim Kurcz]

Expert welder Chris Razor suggested a conforming aluminum heat sink might allow welding of the blade/cap joint with little or no damage to the hardened case. An aluminum bar was turned to .003" larger than the big end bore, and the rod was bolted/torqued into position. Our first attempt saw minor heat soak through the cap section, only at the ends - not bad! Rockwell testing will be conducted at the burn sites and between to determine hardness. During the next attempt, peripheral welds will be allowed to cool before the end welds are made. If RC hardness is in the low-mid 50's, the rods will be honed round and to size, and run. More soon! Tim

[Powerabout]

Nice one....
love to see the actual process of making an outboard rod

[Tim Kurcz]

Nice one....
love to see the actual process of making an outboard rod

It took over twenty trial fittings and adjustments to make this one (note beginning shape). It was necessary to cut intake and exhaust side rod reliefs deeper, and remove 3/8" of the intake side piston skirt to allow interference-free swing: The link rod was striking the intake side skirt! That's how the umteenth prototype link rod was made.....

[Tim Kurcz]

At long last, Rockwell C hardness test results are in. Interestingly, the area between oxidation marks showed the lowest surface hardness(?) Evidently, discoloration is not necessarily an indicator of a change in metallurgy. The un-welded upper rod section tested at 59C, the cap is 54-55 in the discoloration circles, and 49-50 between the circles, dead square in the center of the cap.
Plans are to rifle drill the heat sink and pump water through the bore to draw more heat during the welding operation. It is expected that hardness will be maintained in the mid-50's in the center position. Back to the lab! 60702607016070360704

[Powerabout]

what rockwell do you actually need to run rollers?

[Tim Kurcz]

what rockwell do you actually need to run rollers?

Industry sources report that 60-64 Rc is used for roller bearing support today. It's entirely possible there was some degradation in location #4, as the entire rod did experience heat soak during the welding operation. Water cooling of the heat sink will improve results, so the mid-50's is likely achievable. Welded rods will be used for the prototype.

[Tim Kurcz]

After two months work constructing a customer powerhead dyno (a Stuska water brake), it's back to work on the 888.....
A fixturing jig was machined, rods prepped, and new copper heat sinks were turned. Chris Razor did a masterful job as usual; the welded pieces are beautiful. Machining of the pivot bearing bores will be next weekend. Then it's upper links.

[Tim Kurcz]

At last, a few hours in the shop, and voila! Today the masters, tomorrow the links. Another couple weeks and assembly is possible.....608266082760828608296083060831

[proprider01us]

Nice work Tim!!

[GHMiller]

Very nice, looking forward to every step in this process.

[Tim Kurcz]

Amongst other projects today, a few hours were devoted to the link rods. The first is always the slowest. Hoping to fit the first production rod this week.608376083860839608406084160842

[Al Lang]

As usual, Tim, looking great. Looking forward to see and hear it run when done. You and Dick Austin are the Michigan mad machine masters. All the best on the finished project.

[Yellowjacket]

Looking a lot more realistic. I like the bearing, that should work a lot better. If you look at the area outside the bearing, it needs to be greater than the area of the bolts. That is because the bolts don't see cyclic loading, they are in tension all the time and the area outside the bearings are seeing a cyclic loading. Also the material that you welded on needs to be something that is really tough. Not sure what you used, but hope you've used a high strength steel for that piece. At the same time new rod might be over kill in the area around the pin because it has a much smaller hole and a good bit more material to work with. The point being that the system will fail at the weakest point, which corresponds in this case to the smallest area.

Finally the new rod needs to be lightened as much as you can. The amount of stress in the system and the loads are due to reciprocating weight and the new rod has a lot more area than it needs. Machining the new rod into an I beam would remove a lot of weight and reduce the stress in the all of the places where the system has limited area. Also assuming that you're making the rod out of something that is really high strength, like 4130 and then heat treat it to high strength. Another way to do that would be do mill out the center of the rod and make it hollow and then cut some reliefs in the outside. Because you have access to the inside of the rod from the clevis end you do have an opportunity to structurally optimize the rod. With that in mind there's a pretty chance you could reduce the reciprocating mass a lot and still have a good cross section left that would get you closer to a system that could work to real speed as opposed to just getting to idle or mid range speed.

[Tim Kurcz]

Looking a lot more realistic. I like the bearing, that should work a lot better. If you look at the area outside the bearing, it needs to be greater than the area of the bolts. That is because the bolts don't see cyclic loading, they are in tension all the time and the area outside the bearings are seeing a cyclic loading. Also the material that you welded on needs to be something that is really tough. Not sure what you used, but hope you've used a high strength steel for that piece. At the same time new rod might be over kill in the area around the pin because it has a much smaller hole and a good bit more material to work with. The point being that the system will fail at the weakest point, which corresponds in this case to the smallest area.

Finally the new rod needs to be lightened as much as you can. The amount of stress in the system and the loads are due to reciprocating weight and the new rod has a lot more area than it needs. Machining the new rod into an I beam would remove a lot of weight and reduce the stress in the all of the places where the system has limited area. Also assuming that you're making the rod out of something that is really high strength, like 4130 and then heat treat it to high strength. Another way to do that would be do mill out the center of the rod and make it hollow and then cut some reliefs in the outside. Because you have access to the inside of the rod from the clevis end you do have an opportunity to structurally optimize the rod. With that in mind there's a pretty chance you could reduce the reciprocating mass a lot and still have a good cross section left that would get you closer to a system that could work to real speed as opposed to just getting to idle or mid range speed.

The first production link is only about 50% machined as shown. The pivot end must be slabbed from .625" to .585" to increase clearance from the crank cheeks (.640" between cheeks). Then, the wrist pin end will be cut further to .500" to B98 bearing width. Factory .060" hardened spacers will be used; the boss spacing needs to be opened .050" to accommodate (Merc rods are .446"). The beam itself will be narrowed to appx. .550" to make clearance for the intake side piston skirt (already cut away flush with the scallop). Finally the beam section will be milled with a ball end cutter to provide a modified I-beam shape and reduce weight.

Rods, links, and pins will be matched/balanced before the pins are tack welded in place. Alignment between blocks is critical, because Merc rods are top guided. Opposing pistons will suspend the rod/link on the crank pin, hopefully in the center, and perfectly perpendicular to the cylinder bores. BTW: Material selection is 1018 cold rolled steel. Welder Chris Razor selected a high nickel rod. Drawn cup bearings provide the hardened bearing surfaces, no heat treatment is planned.

[Fastjeff57]

Remember that the load on a 2 stroke connecting rod is primarily TOWARDS the crank. Very little force is used to pull the piston towards the rod (ie; the rod is primarily in compression, not tension).

Check out a con rod from an EMD 2 stroke railroad diesel and you'll see what I mean: There's virtually no bearing material on the bottom of the rod.

Jeff

[Yellowjacket]

1018 is a low carbon steel, the only thing you could do with it would be to carburize it anyway, not worth the trouble. I saw the drawn cup and yes that's a good way to do it, that gives you a good bearing surface without any unknowns. The strength of the weld zone isn't very good, about 53ksi is what you can expect from normalized 1018, the area above the heat effected zone is good for about 70 ksi and that's probably ok given, as Jeff noted the loads are compressive anyway. If the bearing can handle the load then it should work pretty well. Not sure what the bearing loads are, but that's probably the life limiting factor on it right now. Within the limitations of the stock crank cases you've done about as well as could be done.

[R Austin]

Tim

Would it not be better to use a drawn cup bearing in the wrist pin end of the new rod without washers and let the OEM rod control the rod centering on the crank. Let the link rod piston float. If I remember correctly, the wrist pin is 9/16 and a bearing should be available.

[BJuby]

How does the pin with the needle bearing that connects the two rods stay in its hole?

[Yellowjacket]

How does the pin with the needle bearing that connects the two rods stay in its hole?

He mentioned that he's going to tack weld the pin. Tack welding on things with bearings is dangerous. I know they do it with cranks all the time, but one needs to be careful since one can ruin a bearing doing it. The capacitance in the system can cause an arc to jump across the bearing even if that is not the primary path (ground clamp is on the same part as the pin. Good practice is to provide a good ground strap around the bearing to make sure that there is no potential across the bearing ever.

[Fastjeff57]

Lubing the roller bearings helps as well.

Jeff

[Tim Kurcz]

Thanks to all for your input. An update with images was attempted, but an internal server error precluded the post. I'm hoping this quick reply gets through. Another attempt will be made later today.

[Fastjeff57]

Can't wait, as usual!

Jeff

[MErkMAniak]

Need my fix of info from this thread. Hard to wait for an update. Such amazing work..........

[Tim Kurcz]

Need my fix of info from this thread. Hard to wait for an update. Such amazing work..........

Several attempts to update failed. This one is by iPhone in hopes of getting through. Thanks all for your interest and patience. Master and link rods are complete. Crank train fitting begins this week. If this update gets through, images will follow. Tim

[Tim Kurcz]

Several attempts to update failed. This one is by iPhone in hopes of getting through. Thanks all for your interest and patience. Master and link rods are complete. Crank train fitting begins this week. If this update gets through, images will follow. Tim


Tried again with upload failure, both from computer and iPhone. Will attempt to start another thread next week, or ask one of you to post for me. Any volunteers? Email nav27k at Comcast.net
Thanks!

[R Austin]

Tim

Email to me and I will try. I have found lately, past month after the site went down, that it very size critical. I have to convert the size of all my pic now.

[Jippe]

This forum softaware needs fixing and updating. I see errors everytime when posting or uploading.

[Krazy Karl]

Another forum I visit does not allow pictures to be posted. Instead we put our pictures on web hosting site and post a link to the picture. Would that work here? In fact I will give it a try.

http://i67.tinypic.com/2ypnamp.jpg

There it is.
kk

[Ron Hill]

This forum soft ware needs fixing and updating. I see errors every time when posting or uploading.

Try posting one picture, then go to edit and try again. That's how I post. I wish I knew of better soft ware for sale, but I don't.

AU, 1957, test picture.

[25XS]

The only way my last four pictures would post was after I used Microsoft "Paint" program to reduce the width & height to 25% of the original picture, which put my pictures just under 100 kilobytes... Then it worked.

Tom

[R Austin]

I will now try to uoad Tims narrative.

Many thanks to all readers for your kind input. It's a great demonstration of the power of this forum! As a result, the links will be grounded carefully for tack welding to protect the little B65 pivot pin roller bearing (.375" pin dia.). Also, as you'll see in the images below, a B97 roller bearing (.562" pin dia.) is used for the wrist pin end of the link. As noted, this eliminates the need to heat treat, and guarantees a hardened roller surface.

The pivot bearing selected is large as possible given space constraints. The wrist pin bearing is .437" wide pressed into in a .446" rod (same width as factory). Factory thrust washers are retained; they are the top-guided rod bearing surfaces. Unless the cylinder bore spacing is off (unlikely),


From a weight and balance perspective, the factory rods selected were all 164.5 grams (+/- 0.5 g). The 888 modified rods with tab and bearing are 182.0 (+/- .5 g). The first link is 111.0 with wrist pin bearing, and the pin is 18.0 g. So, the combined weight of the tab, link, and pin is 146.5 g (+/-). This is 18 grams less than the factory rod. The question is: Should it be lightened?

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[R Austin]

The balance of the 2nd paragraph. These are uploads for Tim.

the plan is to support the rod from each end such as not to induce diagonal loading through the journal bearings, and to maintain alignment between the counterweight cheeks. 888 fork rod width is .575", and the space between cheeks is .640", which leaves only .032" clearance per side (crank end play is .010").

There are serious issues with uploading. Seems to be size issues of text or pics.

[Jippe]

Try posting one picture, then go to edit and try again. That's how I post. I wish I knew of better soft ware for sale, but I don't.

AU, 1957, test picture.
PhpBB or Simple machines forum (SMF). Both free.

[Yellowjacket]

Your biggest issue is going to bucking of the new rod. The good thing is that the rod is shorter, and bucking failure is a square of the length so you won't require as much of a section as the OE rods. In looking at the pictures a few pages back you've got a lot more meat in this rod than you will likely need. Remember that bucking is a function of moment of inertia and modulus and not strength. That is the strength isn't an issue for bucking, it's modulus and steel is steel. You could calculate the bucking force necessary for the stock rod and then do the same calculation for your rod and that should tell you the story. If you maintain the same bucking capability you should be fine. If you've still got the rod that is in the picture you can clearly make it into an I beam on one direction or the other. Be careful though, the stock rod increases section near the bottom and that changes the section in the areas where the bending stress is the highest, so that's an issue too.

[Tim Kurcz]

6098860987Thanks to Dick for posting the text. Hopefully this image posts.

[Yellowjacket]

Definitely could make a cut on the sides of the rods to reduce weight. Lower is always better. Do some calculations and you'll see that cutting a notch on each side of the rod won't reduce the I value much but you can probably take 30% of the weight out of the middle of the rod.

[Tim Kurcz]

Rods have been honed round to 1.137", pins were cut & fitted to links. Block clearancing and test assembly is planned for this weekend. If all goes well, pins might be tack welded early as Monday. Watch for pics through the weekend.

Tim

[Tim Kurcz]

A couple hours were spent making room for the rods, basically duplicating the prototype cutout. Fitting this weekend will include making weld bosses for the bottom end cap, and slotting back-to-back crankcase take up bolt holes: The Mercury bolt pattern is not quite symmetrical. Provided there are no surprises, the plan is to complete first full-assembly mockup next weekend (complete except piston rings). Now we're cooking with gas - Avgas, that is!
BTW: Now that BRF is somewhat behaving, you'll see more images. Tim6100961008

[Tim Kurcz]

Tight turbo packaging made internal block watering risky, so bypass channels are fed externally. Two bolt bosses were removed from the bottom end cap, and a new one will be welded into place: There will be only two spaced 180 degrees apart. Finally, the carb to turbo adapter was machined. It's off to the welding shop tomorrow. Images of fitted accessories will be posted later this week. Tim61010

[Tim Kurcz]

While the carb adapter and bottom end cap are at the weld shop, it was time to complete the cooling system, locate the ECU and methanol tank. Watering will be as Mercury designed it except the rear bank will be fed externally. There are too many fasteners in the turbo mount area to provide a sufficient water channel. Inlet side rear bank port covers will be drilled and tapped for primer nozzles, and ignition coils mount to the rear cover flange, so the only remaining spaces for the ECU are on top of the front bank, or over the upper exhaust cover on the front bank (not smart to position the methanol injection tank over the ECU and/or starter solenoid). Hard to believe, but I'm starting to run out of real estate!6101761018

[GHMiller]

What a really neat project this is turning out to be. Thanks for sharing and I'm looking forward to the completion of this motor.

[Tim Kurcz]

Ignition will be provided by Matt Richardson who developed the "Firefly" capacitive discharge system for the Oregon river racers. He bench tested a version modified specifically for the 888 that fires in pairs (remember only four firing events per revolution, two cylinders at a time). To learn more, go to: http://southsidelabs.com/ignition.html
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[Fastjeff57]

Glad to see you opted for a more powerful starter. The stock one would have burnt up!

Jeff

[Tim Kurcz]

Glad to see you opted for a more powerful starter. The stock one would have burnt up!

Jeff

Actually, the flywheel is a 9-1/2" Merc 1000 compliments of Steve Wheeler at Wheeler's Marine. The larger diameter was needed: With the standard front cover gone the starter couldn't be mounted close enough for the 8" Merc 500 piece.

[Tim Kurcz]

Ignition will be provided by Matt Richardson who developed the "Firefly" capacitive discharge system for the Oregon river racers. He bench tested a version modified specifically for the 888 that fires in pairs (remember only four firing events per revolution, two cylinders at a time). To learn more, go to: http://southsidelabs.com/ignition.html
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Apologies all; The Firefly ignition is an inductive ignition system (not CD).

[Tim Kurcz]

The carb adapter and end cap welding is done. Parts are en route; machining of the cap and trial assembly will happen memorial wee61023kend.

[Tim Kurcz]

The top end cap was machined and now sports the Firefly pickup stator installed. Images also show the rotor that includes 5 magnets. On the bottom end cap, the two original front mounting bosses were removed, and a new one welded in place to match the second block. This week, the ignition coils and rotor will be fitted. It turns out, Firefly creator Matt Richardson recommends the ECU be mounted in the boat to avoid vibrating critical components.61030610296103261031

[Techteam]

Gotta love RP

[Tim Kurcz]

Gotta love RP

That would be rapid prototyping for those unaware...... Absolutely!

[Al Lang]

Hi Tim, is it the Michigan air that brings out the MAD MACHINEST in you and Dick Austin ? Looking forward to the results of both of you.

[Tim Kurcz]

Hi Tim, is it the Michigan air that brings out the MAD MACHINEST in you and Dick Austin ? Looking forward to the results of both of you.

Hi Al, Pretty sure Dick and I have the corner on the radical outboard projects business lately. The site is not letting me load images, but the oil pump & methanol tank have been fitted, and the rod pivot pins tack welded. Tim

[Tim Kurcz]

If BRF is behaving itself, images of the 888 mockup are attached; looking vicious! This is the extent of my work until fall due to an impending move. Look for updates in September. If all goes according to plan, the completed 888 will be displayed at Mark Suter's October 2016 AOMCI meet. Thanks for your many helpful comments and suggestions. Best regards to all, Tim

BRF not behaving today....... I'll try different methods for posting over the next few days. Stay tuned.

[Fastjeff57]

..."This is the extent of my work until fall due to an impending move."

God help you! I'm in the process of completing one myself (after 36 years in the same place). A nightmare!

Jeff

[Tim Kurcz]

..."This is the extent of my work until fall due to an impending move."

God help you! I'm in the process of completing one myself (after 36 years in the same place). A nightmare!

Jeff

Likewise..... 28 years here. Moving the machine tools, fixtures, engines, and parts is way worse than the house!

Tim

[Al Lang]

Hi Tim, staying in MI ? I miss attending Mark's AOMC meet, so much racing history displayed. Have missed many of your MAD machinest displays at Mark's.

[R Austin]

In as much as Tim is having trouble uploading pictures, I will upload the engine mock up photos that he has forwarded to me by email.

It is a really nice looking package looking forward to seeing it run.


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[Fastjeff57]

In a word WOW!

Thanks for helping him out.

Jeff

[Tim Kurcz]

Many thanks to Dick Austin for posting images. The 888 looks fearsome, and will run early fall; a move will delay completion. More images and detail will be posted as progress occurs. Have a fun summer, and always remember: The throttle works both ways! Tim

[Powerabout]

Can you give us a precis on how it works, crankcase compression ratio zero, so boost overcomes that, is that it?

[Tim Kurcz]

Can you give us a precis on how it works, crankcase compression ratio zero, so boost overcomes that, is that it?

Precisely: The crankcase is an open plenum; the crankshaft is supported by reed cages with no reeds. Cylinders are fed with air-fuel mixture supplied by the turbocharger.

[Al Lang]

Hi Tim, are you staying in MI ? That MI air seems to keep the creative juice flowing. Between our old friend, the late Bud Parker, you and Dick showing the way to the future. Hope everything goes well in the move.

[Tim Kurcz]

Hi Tim, are you staying in MI ? That MI air seems to keep the creative juice flowing. Between our old friend, the late Bud Parker, you and Dick showing the way to the future. Hope everything goes well in the move.

Hi Al,
Actually departing Michigan for the mountains, lakes, and rivers of Idaho. The shop will be down for a few months; but you'll see updates in September if BRF behaves itself! Have a great summer, all!
Tim

[Al Lang]

Tim, looks like you will be missed at both Top O marathon and Mark's AOMC meet. All the best in your move. Al

[Ron Hill]

Nothing has been deleted, just some stuff got merged together!

[Powerabout]

Nothing has been deleted, just some stuff got merged together!

where did all the stuff from the sst45 thread go, I thought it was lost in the last faulty backup?

[Master Oil Racing Team]

I've looked around for stuff too Powerabout. Search doesn't really do much. I found that the "sticky" stuff didn't always stick with age nowadays. If it's not active enough, it kind of falls down and not stuck where it once was. It's all kind of random and you have to look at everything until you find it. SST45 was one of the most active so it's kind of surprising that you can't pull it right up, but take some time, and when you find it, post something, then it should pop back up to the top. At least, that's what I have found to happen.