I did not know that they made a cracked rod for the 40-44 inch motors. I thought they were all nut and bolt type with machined mating surfaces.
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I did not know that they made a cracked rod for the 40-44 inch motors. I thought they were all nut and bolt type with machined mating surfaces.
Very late 44's were cracked rods, Not sure what year they went to it, but most of them were the machined rods.
Maybe high speed wasn't what broke it. This engine he built is something different and there is no telling what kind of power and load that's happening with the rotating assembly. It could be packing 300++ hp for anyone knows, maybe able to go beyond 400hp as the twister-2 made over 200+hp. This looper is far beyond the twister in performance design and those rods might not be able to handle the shear force of load at acceleration. I'm sure that rods can be made for this engine. Titanium would be nice!! If I had the machinery I would sure go for it.
As I understand it, the motor was not at full throttle when it blew. Correct?
Jeff
Quote:
Originally Posted by Yellowjacket
Your are correct. I Googled the 44XS and found a thread right here on BRF "44XS Secrets", and found the specs listed for the rod torque. As you posted 18 ft lbs,216 inch pounds. I went to the parts books for the last of the 4 cylinder Classic motors and found the rod and it was a cracked rod which has the same bolt part number as the 115 cracked rod. I have also bought a rod bolt measure gauge and will test a couple of bolts to find the stretch and failure point.
Did you do a closeup inspection of the broken parts and look for "beach marks" on the rod bolt breakage surfaces? I used to do failure analysis on jet motors and most of the time we could find the origin of the failure by looking carefully at the fracture surfaces of the parts that failed (when we could find them). Pure tensile failures (as your broken end caps probably exhibit) are very different than the surfaces that fail from fatigue. Fatigue failures are smoother (until you get to the point of overload) and you can often see the fatigue striation pattern in the failure. Use at least a 10X magnifying glass or eye loop and look carefully at what's left. It may be very enlightening. You won't see much in the bolts, since they will break from tensile overload shortly after the fatigue a small amount, but if you look carefully and if that part of the fracture surface hasn't been hammered (that's very possible too) and suffered secondary damage you might be able to see the fatigue damage. If the rods didn't have enough torque on them then there should be some fatigue evidence just before they let go.Quote:
Originally Posted by R Austin
Another thing you might do is call or send a note to Jerry Wiendant at Trident racing. Jerry is the person who wrote the "44 Secrets" paper, has probably built about a thousand racing motors (or more) and he is not only extremely knowledgeable but is more than willing to share his knowledge and experience. I'm sure he would know how fast this rotating assembly can be spun safely, at least as far as the rods are concerned. He responds to emails and his email address is in the "secrets" thread.
The repair work has been completed and now starting the reassembly. Had to find a new crank as the number 1 journal had taken quite a beating.
The following is just a few pics of the repair results.
The sleeve was marked on both ends relative to the bridge between the exhaust ports for alignment. The marks on the sleeve are radial lines while the block has lines parallel to bore center lines at the bridge edges. The trick is eyeball the 4 lines so the 2 block lines are centered between the 2 sleeve lines for the transfer port alignment. One of the lines on the sleeve is hard to see in this picture. If you were to extend the block lines they would near align with the bore side of the radial line. The exhaust ports were cut after sleeve installation on the mill.
Attachment 59970
Sleeve has been installed and trimming of the bottom of the sleeve and the JB weld filler.
Attachment 59971
The finished right hand side of the transfers. The side least damaged.
Attachment 59972
This the left side finished that had the rod split in the side of the cylinder.
Attachment 59973
Finished porting as viewed from the head end of the block. The port mapping, center alignment and finishing, worked out well.
Attachment 59974
And from the bottom of the cylinder.
Attachment 59975
This is the outside view of the only visual evidence of any damage.
Attachment 59976
The out side view of the cover looking at the distributor mount ear, is evidence that the corner of the case was not broken off. It just cracked the mating flange around the bolt boss and into the reed pocket. The most massive part of the casting.
Attachment 59977
The top end of the block and case assembly were refaced to insure a true surface after the welding and rework. The turning was done on the same machine that the line boring was done on. It has a pair of sleeves that slide onto and pin to the bar. They reflect the main bearing body size. At the beginning of the thread you will see the same setup used to face the ends of the rotary valve motor.
Attachment 59978
While the setup was in place I took the assembly and turned around and faced the bottom to know that it was true to the crank bore. The mill that I had used was tough to set up and was close but slightly off, so the turn was worth the time.
Attachment 59979
As always, very impressive, good luck with the repairs and looking forward to hearing this beast run again.
I was looking at rod torque numbers and in my Chilton manual for the 44's it has the same 15 foot pound (180 inch pound) number that you had found previously and used on your last build.
Jerry recommends 18 foot pounds and builds a ton of motors that way and I don't think he's ever had a rod failure.
I found a reference where Harry Brinkman helped a guy build a 22 inch mod motor (same rods) and he was using 17 foot pounds.
I happened to take apart a "virgin" Merc 44 this weekend that still had the factory seals on it. It was the older style machined rod motor, but those have the same e size bolt as in the cracked rods so the torque should be the same. As I took apart each rod I first tried to tighten them and see what it took to get them to move at all.
I stepped up on each nut in 5 inch pound increments with a clicker and if the nut didn't move I tried again with another 5 inch pounds. I found that to get them to move a tiny bit it took between 200 to 205 inch pounds, which is about 17 foot pounds. One can argue that static friction is higher but I don't think the factory ever used 180 inch pounds. The 200 to 205 inch pounds doesn't seem like a lot more, but 13% more is actually a good bit more, and 18 foot pounds is 20% more than 15 which is a heck of a lot.
I don't know what the yield strength is of these bolts. You would have to pull one to see what the yield and ultimate strength are, but I would expect that these bolts are probably good for about 180 ksi (typical of chrome molly rod bolts). If you look at torque charts for lubricated bolts with a friction factor of .17 (assuming you are using Loctite) a torque of 210 inch pounds would equate to a 75% load factor for a 180 ksi bolt.
Anyway that's probably pretty close to what is right. Something north of 200 inch pounds is more like what Mercury used.