Crankshaft problems

[DLM]

I made a crankshaft for my Holt engine out of cold roll and it has sprung out of true. it is not that bad but not good enough to run in 5 brgs. Is there a way to relive the stress in it, will heating it do any good ? What is the best steel to use the plans for the holt call for cold roll . I followed the steps as close as i could that George B had on a another form and every thing went real well Thanks for any help

Don In pueblo Co

 

[ozzie46]

Seems I remember someone on here saying to heat cold rolled to red hot then let it cool slowly to relieve the stress. I have read also that hot rolled is better to use as a crank.

Ron

 

[DaveRC]

I asked a similar question on here a while back. Was told, and have been by a fried of mine who is a model engine builder, to stay away from cold rolled steel for cranks for the very problem you have now.

The stuff I was told to use was black steel, not sure if this is rolled or not. Not tried it yet but I now have a lump of black steel sitting on the bench waiting for me. (not sure why it's called black as it far from black)

Dave

 

[cfellows]

I made a crankshaft for my Holt engine out of cold roll and it has sprung out of true. it is not that bad but not good enough to run in 5 brgs. Is there a way to relive the stress in it, will heating it do any good ? What is the best steel to use the plans for the holt call for cold roll . I followed the steps as close as i could that George B had on a another form and every thing went real well Thanks for any help

Don In pueblo Co

The problem is, you have already relieved the stress by cutting away a lot of the material. The stress relief process has to be done before you work the material. I think your best bet at this point is to try to straighten the crankshaft with a press.

Chuck

 

[putputman]

I don't know how to recover the crank you have, but if you are forced to make a new one, you might consider using 1144 stress free steel. I have made many single throw cranks using this steel and it is very nice machining and very stable. Cost is slightly more than CRS. As far as I know it is only available in round stock.

 

[Jasonb]

The stuff I was told to use was black steel, not sure if this is rolled or not. Not tried it yet but I now have a lump of black steel sitting on the bench waiting for me. (not sure why it's called black as it far from black)

Black is hot rolled and should still have a distinctive blue/black scale on the surface. It does not move as much but the down sid eis it harder to get a decent finish on it.

J

 

[Dave G]

I'm with putputman, 1144 stressproof is the best I have found for crankshafts. It is normally hardened to around 20-24
rockwell "C" scale, which gives it much better wear properties, and it will polish better. It's a free machining steel that
cuts very easily, but has very little stress. I once machined a crankshaft for a CHALLENGER V-8 and when finished before grinding, it only had .0015 TIR (total indicator reading) runout at the center main journal. The only downfall is, as he states,
it only is supplied in round stock but it is well worth the extra work. Dave

 

[el gringo]

Add my vote for 1144 stressproof...also makes nice little cams and lifters (flame hardenable).
El Gringo

 

[GOOFY063]

I've seen a old timer in a engine machine shop once take a lite tap with a hammer in the right place on a steel crank for a big block chevy, bang turn it with two fingers. Thm:

 

[gbritnell]

Hi Don,
I did in fact make a crank for my Holt but it wasn't from CRS. I found out years ago that working with cold rolled can be very frustrating when making thinks like multi-throw cranks. As has been stated the best thing to use is 1144 stressproof steel. If you want a rectangular section crank you will have to machine it down as it only comes in round section.
gbritnell

 

[kf2qd]

As you have seen, cold rolled is a highly stressed material. If you are turning it, you will have very few problems, as long as you are not trying to turn eccentrics and such. When you try to do an operation where you are not removing material evenly around the stock it will move, and sometimes quite a bit. For example - take a piece of cold rolled flat and put it on a surface grinder, you may find that after a few thousnadths it is no longer flat on the mag chuck as enough material has been removed from the one side to cause the piece to warp. Even worse results on a milling machine.

Cold Rolled disks would probably do for a built up crank when cut to disks, but even there there would be a good chance of warping withthe application of heat.