Anyone ever straighten a twisted FEL?

[SPYDERLK]

I spent over 30 years straightening frames, among other things, in the auto body repair business.

So trust me, I know exactly what, when, where, and how much heat it takes, when it won't move, because I have done it thousands of times.

So, are you saying 300 wont do it regardless of stress level, or that under certain conditions it will?
larry

 

[ray66v]

So, are you saying 300 wont do it regardless of stress level, or that under certain conditions it will?
larry

I am saying, countless times, I was standing there, with many tons of force applied and it wouldn't budge. So, I'd heat it with a big torch. I could see how hot it got before it started to matter. And I have never seen the first 300 degrees matter. Only the last 300 does.

 

[tungularafishcamp]

Good Job Blueriver:thumbsup:
Rick

 

[Car Doc]

the first 300 degrees matter. Only the last 300 does.

Amen to that well put! :thumbsup:

 

[SPYDERLK]

I spent over 30 years straightening frames, among other things, in the auto body repair business.

So trust me, I know exactly what, when, where, and how much heat it takes, when it won't move, because I have done it thousands of times.

I am saying, countless times, I was standing there, with many tons of force applied and it wouldn't budge. So, I'd heat it with a big torch. I could see how hot it got before it started to matter. And I have never seen the first 300 degrees matter. Only the last 300 does.

Well, quite a few years back I wanted to make the front fork springs on my motorcycle a progressive rate rather than the standard constant rate that came with the bike. I checked them as installed a did some figuring to find that they were not being near fully compressed so there was more performance available. So I made a washer nut bolt arrangement that would allow me to compress a number of coils at one end of the spring. I then took careful measurement of the spring length and went down a dozen coils [about 5"] into it and squeezed those coils tight shut with my device. When allowed to reextend the total spring was about 1/16" shorter. From this I knew that fully compressing the spring [coil binding] in its as wound pitch caused it to exceed its plastic stress limit - but just a little bit. I had to get them to give a lot more so that when in use these coils would work for only part of fork travel before coil binding and causing spring rate to rise. I re-bound the 12 end coils and cooked them in 250F motor oil. When the spring was allowed to relax it was now 1-1/2 inch shorter. Not enuf I didnt think based on my figurin, so I upped the oil to 300 and did it again. Now 2-1/4 shorter. Seemed about right since I wanted a gradual rate increase rather than a single step and planned to work some more on the very end coils to give them a tighter pitch. I compressed the 5 end coils of the 12 and then cooked them in 400 ... then had to step up to around 450 to get a close enuf pitch set. [ Did I mention I was outside? Had some flameup and had to cover the oil except for room to dip the spring.] 450 got the endcoils down to about 3/32 spacing. I now had a spring that would act exactly like the old spring until the 5 end coils bound ... then be around 5% stiffer until the remaining 7 of the 12 bound to become about 20% stiffer than the original. Got the second spring done a lot faster. That oil was ruined!

The message here is that if you are having to heat metal a lot to move it you are not pre stressing it to anywhere near its elastic limit before heating. It is best to heat less if you can manage the forces needed. Metal properties are safe to about 500, but degrade above that and then youve got it straight, but weakened it. Darn it anyway.
larry

 

[ray66v]

The message here is that if you are having to heat metal a lot to move it you are not pre stressing it to anywhere near its elastic limit before heating.

Okay, Imagine when 20 tons of pulling force. Half of which, is sometimes more than enough to rip the area your attached to, right off the vehicle, does not get the job done. I don't know how much more pre stress than that you can get.

There are often incredible forces applied during a collision.

It's easier to put Humpty Dumpty back together again, than fix some of these vehicles.

 

[ray66v]

Amen to that well put! :thumbsup:

 

[SPYDERLK]

Okay, Imagine when 20 tons of pulling force. Half of which, is sometimes more than enough to rip the area your attached to, right off the vehicle, does not get the job done. I don't know how much more pre stress than that you can get.

There are often incredible forces applied during a collision.

It's easier to put Humpty Dumpty back together again, than fix some of these vehicles.

Yeah, when large areas are affected the corrective forces cannot be applied to all the right points and in the all the right directions simultaneously. The parts can end up fighting each other and a big amply heated zone gets the result you need quickly.
larry

 

[mostly_gas]

I have never seen a situation were something that basically would not move cold, is going to suddenly become submissive, after you heat it to just 300 degrees.

the frames you are straightening are stamped cold ie. room temperature.
In fact all the stampings on the car start at room temp. I have seen stampings hit 150F from drawing but still started at room temp.

 

[ray66v]

the frames you are straightening are stamped cold ie. room temperature.
In fact all the stampings on the car start at room temp. I have seen stampings hit 150F from drawing but still started at room temp.

Sure, you can stamp metal cold, with a 100+ ton press.

That has nothing to do with what I'm talking about.