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Oversize Cox crankshaft

Old 01-17-2008, 03:48 PM
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jeffie8696
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Default Oversize Cox crankshaft

OK here is one for you perfessional moter guys. I have a Cox crankshaft and case that are Significantly larger than normal. Where did they come from. Can't be the famous Venom?
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Old 01-17-2008, 03:55 PM
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Default RE: Oversize Cox crankshaft

I think some of the car engines used an oversize crankshaft. Not sure about the Venom.

George
Old 01-17-2008, 04:16 PM
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Default RE: Oversize Cox crankshaft

That is definitely a car crankcase and crankshaft. The Venom used a conventional crankcase with Cox's version of the kind of Heavy Duty crank that Davis developed for diesel conversions.
Old 01-17-2008, 05:00 PM
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Default RE: Oversize Cox crankshaft

So this would be a good crank to use for a diesel? I think I will be selling it. JOE you out there listening?[sm=lol.gif]
Old 01-17-2008, 05:13 PM
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Default RE: Oversize Cox crankshaft

Oh, you never sell me anything that I'm interested in - so I give up!

Wait, I take that back, once, a very long time ago... Little Norbert.



Old 01-17-2008, 05:15 PM
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Default RE: Oversize Cox crankshaft

Have you checked the mail today?
Old 01-17-2008, 05:31 PM
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Default RE: Oversize Cox crankshaft

I think this is the same style engine that your crankcase/crankshaft is from.... ePay item# 250206166317


Old 01-17-2008, 05:36 PM
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Default RE: Oversize Cox crankshaft

If Joe doesn't want it I would like to try it out for one of my diesel conversions... Let me know..
Old 01-17-2008, 05:45 PM
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Default RE: Oversize Cox crankshaft

I'll have to pass on it - I have enough "project engines" at the moment....

Old 01-17-2008, 07:21 PM
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Default RE: Oversize Cox crankshaft

If you use this for an airplane engine you're going to need to make a new prop driver that fits the splines at the end of the heavy duty crankshaft -- the diameter at the nose of the car crank is larger than that on the airplane crank. This would make a great bottom end for a diesel conversion, especially if you could find one of the heavy duty connecting rods that were an aftermarket item in the 70s and 80s. I vaguely remember the magazine ad: Kal's Kustom Engineering or something like that. Somebody else here ought to remember accurately.



ORIGINAL: chevy43

If Joe doesn't want it I would like to try it out for one of my diesel conversions... Let me know..
Old 01-17-2008, 07:39 PM
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Default RE: Oversize Cox crankshaft

Hey hows about one of those OK cub aluminum rods ( could be bushed I bet) and a piston with a wrist pin instead of the sloppy ball and socket. Joe how can YOU have too many project engines?
Old 01-17-2008, 08:33 PM
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Default RE: Oversize Cox crankshaft

ORIGINAL: jeffie8696

So this would be a good crank to use for a diesel? I think I will be selling it. JOE you out there listening?[sm=lol.gif]

yes indeed, it is from one of the versions of car engines. there where two that I am aware of, the one shown with the splined end for a drive washer and the other was the same size but had a tapered end rather than the spline.

I have used both to build plane engines and the ones I run on glow run rather well. I wouldn't say better or worse than ones using the smaller shaft however. The larger shaft cranks are a bit more robust.

As a crank in a diesel conversion, I thought they would be better than the standard size cranks. They are but only a bit. I managed to break 2. Better off using the Davis Diesel crank for that applicaton.

attached is a picture of one of the broken cranks, in this case it was one with the spline on the front.


cheers, Graham
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Old 01-17-2008, 11:04 PM
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Default RE: Oversize Cox crankshaft


Ever thought of having them cryogenically stress relieved? I heard it works wonders. [8D]
Old 01-17-2008, 11:53 PM
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Default RE: Oversize Cox crankshaft

Worked for me, but now my teeth are chipped from shivering so much. Sorry just could resist its late .....
Old 01-18-2008, 07:28 AM
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Default RE: Oversize Cox crankshaft


ORIGINAL: jeffie8696


Ever thought of having them cryogenically stress relieved? I heard it works wonders. [8D]

interesting topic. I did a bit of research some time ago prompted by an article in the NASS Speed Times newsletter. Reported results where very positive. There seems to be those who believe quite strongly in the process and others that believe quite the opposite, eash with their own facts and figures. I'm still stitting on the fence over this one.

The broken crank in the picture I posted was also tempered (baked in an overn at 450 degrees F for an hour with a very slow cool down to room temperature - I treat all the cranks in my cox engines that way). Still broke.

If anyone has some good reference sites/material on cyro processing (an nitriding) please post them. I am always curious of new and better ways of doing things.

cheers, Graham
Old 01-18-2008, 02:38 PM
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Default RE: Oversize Cox crankshaft

Now if I remember correctly the slow cooling process is called annealing and softens the metal. Perhaps it was too soft and flexed at the break? Maybe?
Old 01-18-2008, 04:38 PM
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Default RE: Oversize Cox crankshaft

The low temp in the oven annealing only drops the hardness a few points , but the long time allows the crystal structure to reestablish itself to some degree , ie the crystals grow in size, this makes the metal tougher and also helps releive stresses imposed by the machineing and hardening.
The breakages are dur to the fact the crank web is just not thick enough to handle the bending loads imposed.
Stewart
Old 01-18-2008, 09:44 PM
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Default RE: Oversize Cox crankshaft

ORIGINAL: SGC

The low temp in the oven annealing only drops the hardness a few points , but the long time allows the crystal structure to reestablish itself to some degree , ie the crystals grow in size, this makes the metal tougher and also helps releive stresses imposed by the machineing and hardening.
The breakages are dur to the fact the crank web is just not thick enough to handle the bending loads imposed.
Stewart
Well put Stewart, that is exactly the whys and what fors.

The common reedy cranks are just not up the task of running as diesel. They will work for a while and you may get quite a lot of use of the engine but the risk is always right there just waiting to show itself.


cheers, Graham

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