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v twin crank pin damage

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Re: v twin crank pin damage

Postby Kevin Johnson » Sun Sep 22, 2013 7:25 am

Dan Timberlake wrote:the Hertzian stresses when curved surfaces are forced together (as in rolling element bearings or gear teeth) are highest just below the surface. I think This spells trouble for any plating or coating applied to a hard working roller bearing or gear, since the bond strength of the coating to the substrate will be severely tested, and is likely not more than a few thousand psi.



I wonder if there is an isostatic pressure means of uniformly (and economically?) compressing a circular outer surface to overyield so as to have the surface work continuously in resisting subsequent loading. Shot peening is incremental rather than continuous, for example. Perhaps the compression of a kernel in some types of devices is an example.

When gun barrel bores are pushed to overyield is the outer cylinder surface constrained and also in overyield?
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Re: v twin crank pin damage

Postby Dutchman » Sun Sep 22, 2013 8:37 am

Who's flywheel are you using ? Are you still using a steel rod,pressed in crank pin?
I worked on t/f Harley's years ago and this was our limiting factor. 5 inch arm is the norm up To 5.250 we went.
Our solution wasn't op and lastly did you Rockwell any components you may be surprised if they are from a leading mc manufacturer.
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Re: v twin crank pin damage

Postby motionper » Sun Sep 22, 2013 2:14 pm

have tried s&s crank with push in pin,now running a thundercrank with hexed shaft the rockwell idea sounds like a good idea. tried carillo top fuel steel rods and mclure steel rods, also thinking about a 4 inch stroke to take some of the rotating pressure off the pin.it turns the needle bearings into dust i have thought about contacting a bearing company and having a caged bearing made with more rollers never thought about zero clerance
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Re: v twin crank pin damage

Postby Baprace » Sun Sep 22, 2013 3:54 pm

Is it possible to put a full floater bearing insert in the application? It seems you are clearly past the limits of a roller type bearing.
Sounds to me like the rollers are skidding , from too much load. I think an insert type bearing would distribute the load over a bigger area. When I see crank pin wear on most race engines it is always the bottom side of the pin that is wearing first, I attributed the wear to the most load/power on the pin was on the down stroke not on the top of the pin. JMO
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Re: v twin crank pin damage

Postby Dutchman » Sun Sep 22, 2013 5:26 pm

What is the dia. Of the pin ?
Is that Paul mateyka's stuff if it is ,he is a real sharp guy. We were running s&s s press stuff with McClure rods as well,but it was cryogenics that kept it together.same thing,would peel the pin and shortly after window the cases.
Couldn't finish past the semis before.sent it to swain tech or 300 below I believe and would last two races before we had to go through the bottom end.
A larger dia crank pin would allow more rollers to stay in contact at one time.or you can switch to a side by side rod with a insert bearing.
I am still in touch with the race guys at s&s did you discuss your problems you were having with them ? Mike rominski is very knowledgeable guy .
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Re: v twin crank pin damage

Postby Truckedup » Sun Sep 22, 2013 5:44 pm

I'm not the smartest guy here ,but tearing up stuff like you are might also be partially caused by detonation.
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Re: v twin crank pin damage

Postby panic » Sun Sep 22, 2013 6:18 pm

Bigger pin, smaller needles.
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Re: v twin crank pin damage

Postby motionper » Sun Sep 22, 2013 6:24 pm

tried ignition timing from 32 degrees to 20 degrees pulling out a degree per lb of boost up to 12 degrees, last time out is was so rich it blubberd and still ate the pin, if it was detonation why the bottom of the crankpin?? i like the cyro idea did you do the rods,pins and bearings????
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Re: v twin crank pin damage

Postby motionper » Sun Sep 22, 2013 6:55 pm

anyone know where i can find the pressure applied to the crankpin
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Re: v twin crank pin damage

Postby hondo » Mon Sep 23, 2013 10:07 am

the bottom of the pin is "the top of the pin" when the pistons at bottom dead center[bdc], check cyl bore with a dial bore gage , see if the rings or anything else is getting pinched when the crank is trying to push the piston "up" from BDC, pistons dwell a long time at bdc with long stroke and can create "hammering " on the crankpin,
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Re: v twin crank pin damage

Postby Kevin Johnson » Mon Sep 23, 2013 8:38 pm

http://www.google.com/patents/US4002380

If available, try preloaded hollow roller bearings. Follow the background discussion that references their anti-skid properties as well.
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Re: v twin crank pin damage

Postby ParDeus » Mon Sep 23, 2013 11:22 pm

This is a bit off the wall, but has anyone ever put the bearing on the crank and have it spin inside the rod?
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Re: v twin crank pin damage

Postby lorax » Mon Sep 23, 2013 11:58 pm

ParDeus wrote:This is a bit off the wall, but has anyone ever put the bearing on the crank and have it spin inside the rod?


Needle bearings float, and the needles migrate around the pin. There is no such thing as "on" the crank, or "in" the rod.

If you mean plain bearings, they ran "full floating" plain bearings for years up to about the 50s. Particularly flat heads. There were even guys that converted SBC the first years they were out, over to full floating bearing. Neither is a "fix" for anything.
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Re: v twin crank pin damage

Postby Dan Timberlake » Tue Sep 24, 2013 7:40 pm

Kevin Johnson wrote:http://www.google.com/patents/US4002380

If available, try preloaded hollow roller bearings. Follow the background discussion that references their anti-skid properties as well.


==========================

There were industrial versions of hollow roller bearings available in the early 2000s. They had a nominal load capacity that was a fraction of solid rollers and low stiffness too. Roller flex was behind both those limitations. There were limits to how small the rollers could be made. Harley big end rollers of the 70s and 80s were nominally 3/16" diameter.
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Re: v twin crank pin damage

Postby Dan Timberlake » Tue Sep 24, 2013 7:49 pm

Baprace wrote:Is it possible to put a full floater bearing insert in the application? It seems you are clearly past the limits of a roller type bearing.
Sounds to me like the rollers are skidding , from too much load. I think an insert type bearing would distribute the load over a bigger area. When I see crank pin wear on most race engines it is always the bottom side of the pin that is wearing first, I attributed the wear to the most load/power on the pin was on the down stroke not on the top of the pin. JMO


For simply loaded ball and roller bearings a minimum load is specified to minimize skidding. When a roller skids rather than rolls it can damage the exotically mahined surfaces, and things go to hell quickly.
http://www.skf.com/group/products/beari ... index.html
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