Another myth put out to pasture

[itslow]

Originally Posted by 37 Coupe

How does this put the myth to rest? If properly stored they should have no run out. I wouldn't be happy checking for run out on a shaft of any type and finding .003.

Everything will have some amount of run-out to one degree or another. It is next to impossible to machine any turned shaft, whether it be a crankshaft or not, with absolutely zero run-out.

The real question is: What amount of run-out is acceptable for a Flathead crankshaft?

Lots of speculation on this subject by folk (both here and elsewhere) that have little to no background in mechanics of materials and are instead solely relying on hearsay.

[tubman]

OK. I have been looking all over the internet trying to find what the acceptable run-out should be for a flathead crankshaft. Very surprisingly, there seems to be no information on this. Just about everything I looked at said that proper bearing clearances are much more important than run-out. The one place I did find some actual numbers were on snowmobile forums. This is typical of what I found :

"I have heard between 2.5-3 thousands are factory spec so the question is how far does one let the crank get out of spec before repair? 4-5-6? What is a good measure to tell when the crank is on its last legs or could benefit from some preventative maintenance."

I have owned a few snowmobiles, and all of them had a red-line of over 10,000 RPM. From this, I have to believe that "less than .003" would be more than adequate for a flathead. Therefore, I stand by my initial statements.

I have spent some time and money determining these facts, which I believe will benefit the majority of members here.

I hate to have to say this, but unless you guys can come up with some solid, verifiable numbers, "37 Coupe" and "Kube": stay out of this thread; you have nothing to add but negativity, and that hurts everyone.

[Alaska Jim]

you guy's crack me up.

[Charlie ny]

Run out, I'm lucky if I can crawl out some mornings, yikes
Charlie ny

[40 Deluxe]

Thinking more about this alleged run-out issue: So we have a crank laying horizontally on a shelf for years. Since it is supported in several places by the counterweights no matter how you turn it, just where does this distortion occur? At the front main? Center main? Rear? At one of the crank throws?

[Old Henry]

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Why don't y'all just keep your crankshafts in your engines like I do? Haven't had mine sag in there.

[bbrocksr]

Originally Posted by tubman

OK. I have been looking all over the internet trying to find what the acceptable run-out should be for a flathead crankshaft. Very surprisingly, there seems to be no information on this. Just about everything I looked at said that proper bearing clearances are much more important than run-out. The one place I did find some actual numbers were on snowmobile forums. This is typical of what I found :

"I have heard between 2.5-3 thousands are factory spec so the question is how far does one let the crank get out of spec before repair? 4-5-6? What is a good measure to tell when the crank is on its last legs or could benefit from some preventative maintenance."

I have owned a few snowmobiles, and all of them had a red-line of over 10,000 RPM. From this, I have to believe that "less than .003" would be more than adequate for a flathead. Therefore, I stand by my initial statements.

I have spent some time and money determining these facts, which I believe will benefit the majority of members here.

I hate to have to say this, but unless you guys can come up with some solid, verifiable numbers, "37 Coupe" and "Kube": stay out of this thread; you have nothing to add but negativity, and that hurts everyone.

Are you saying that only posters that agree with you can post on your thread?
Bill

[tubman]

Originally Posted by bbrocksr

Are you saying that only posters that agree with you can post on your thread?
Bill

Not at all. Read my post again; If they have any proven, verifiable hard information, they are very welcome to post. We don't need any unverified opinions or off the wall theories. I spent a bunch of time and money determining what I did; I only ask that they do the same.

[Jim in Wisconsin]

In science it's very hard (maybe impossible) to prove a negative.
Having an example of something not happening only shows that it sometimes doesn't happen.
Having an example of something happening shows that it sometimes does happen.

Does anyone have an example of a crankshaft that was known to be perfectly straight (or of a known amount of runout and just where the runout was), and then stored it for a number of years on it's side and then re-measured it, and it had warped?
The burden of proof is usually on the person making the claim.

[rheltzel]

Molly suggests that those of you who still want to debate the point do a search on "gravity bends a crank", where the subject was exhaustively discussed: https://www.fordbarn.com/forum/showth...ty+bends+crank

[Mike in AZ]

tubman....what were your initial reading of runout on those cranks before your stored them?.....Mike

[oldford2]

Come on guys,
Too many guys on here that apparently have doctorates in metallurgy. If you have .003 runout that means the center journal is .0015 off center. Bolt that center cap and button it up. jmho
John

[tubman]

Originally Posted by Mike in AZ

tubman....what were your initial reading of runout on those cranks before your stored them?.....Mike

Boy, I wish I knew; it would explain a lot of things. At the time (about 25 years ago), a friend of a friend (a Mopar guy) asked me if I wanted 3 8BA's for $100. I said "Sure!" and took them home. I pulled them apart (they all came apart easily), and I covered them with oil, wrapped them in plastic, and stored them away.

If anyone can come up with Fords specifications on acceptable run-out, I'd really appreciate it. The thing to keep in mind however, is that even a run-out measurement of up to .005" would be eliminated by turning the mains .010 under.

[tubman]

Originally Posted by Jim in Wisconsin

In science it's very hard (maybe impossible) to prove a negative.
Having an example of something not happening only shows that it sometimes doesn't happen.
Having an example of something happening shows that it sometimes does happen.

Does anyone have an example of a crankshaft that was known to be perfectly straight (or of a known amount of runout and just where the runout was), and then stored it for a number of years on it's side and then re-measured it, and it had warped?
The burden of proof is usually on the person making the claim.

This is the sort of information I'd like to see, not unverified speculation.

Thanks, Jim

[Tinker]

Originally Posted by Mike in AZ

tubman....what were your initial reading of runout on those cranks before your stored them?.....Mike

Okay disclaimer. I don't know crap about nothing. But what was Henry factory specs. Were they perfect specimens of a thousands or 10 thou of a inch?

I don't know?

[countrysquire]

Sadly age is what really bends a crank...


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[Ronnie]

Time to sweep this thread under the bench way too many wannabee crank specialists here must be something in the drinking water. "LOL"

Here is the same argument from 5 years ago https://www.fordbarn.com/forum/showthread.php?t=5509


R

[Karl]

I have a scientific mind but am not a metals specialist . My scientific mind tells me (with a little help from Harold Sharon) that the elastic range must be exceeded before plastic deformation. The elastic range of metal is huge and hence I believe that the force of gravity is not enough to cause cold creep. If the crank was made of something with a low elastic range eg peanut butter then we would see cold creep. If a crank will cold creep then surely all the camshafts in the world would be bent due to the force of the open valve springs on the cam-not to mention all the axles on parked cars in the world due to their orientation and the weight they are carrying. Again I can't prove this but applying common sense would suggest that cold creep in metal is not true .

[tubman]

Originally Posted by Ronnie

Time to sweep this thread under the bench way too many wannabee crank specialists here must be something in the drinking water. "LOL"

Here is the same argument from 5 years ago https://www.fordbarn.com/forum/showthread.php?t=5509

R

Ronnie,

You are absolutely right about "kicking this thread under the bench". I am very familiar with the thread you are referencing here, which is why I started this one because I had absolute, definitive information on the subject, which was not present in the thread you referenced. Unless someone has solid information to the contrary, I'm done.

Tubman

[Kube]

Originally Posted by bbrocksr

There are now two posters that understand metals and metal working.
Bill

Bill, I have an extensive background in tool & die. State indentured. I also have a degree in metallurgy. Spent many years as a tool maker, in charge of quality control of the tooling produced and requisite laboratory inspections of steel, etc.
That being understood (I hope) I can say with certainty that standing a crankshaft on end is the best way to store them.

Ya know, lots of different ways 'work". However, there is only one "best" way.
I try to keep in mind that not everyone graduated at the top of their class. Heck, judging by many of the posts herein, I have to wonder just how many actually graduated.