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Correct procedure for unbending a bent wing car?


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#1 Highnoon

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Posted 23 May 2019 - 08:10 PM

Back in the 80s when I used to bend a wing car chassis I didnt have the luxury of tossing it and buying new.
I used to heat it up with my neighbors acetylene torch all over a section at a time till it was cherry red and then let it cool. Then I would start bending until I got it flat. Then heat it up again till blue and quench in water. We used to buy spring steel blanks, at least thats what they were called.

Questions:

What kind of steel are todays wing cars made of?

Will this procedure still work.

Can a propane torch work or do I need bigger.

Thanks.
Gary Cooper




#2 idare2bdul

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Posted 23 May 2019 - 10:48 PM

It works better to not hit things or just buy used ones from the guys that quit.


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#3 MSwiss

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Posted 23 May 2019 - 11:12 PM

Between my own racing, pitting friends, and just wandering through the raceway, while random races were going on, I straightened a lot of chassis.

We raced a lot in Chicago, and I traveled a lot (I ran in 41 G7 races in 1988)

And with usually not racing until the last race of the day, or the weekend, I was inside raceways during races, probably more than anyone else.

So from 1982 to 2006, probably no one on the planet had worked more at straightening chassis. Lol

I don't remember doing anything that wasn't logical.

I mostly just used my hands.

I had pliers, but used them mostly with Dremel notches cut on the outside of the jaws, as a spreader, to straighten out caved in, side rails.

I never used heat, even back at the shop, nor did my boss, Stu Koford, suggest I/we try it.

That said, at $29.95, for one of my Group F chassis, it can't hurt trying your old method.

Maybe you'll stumble onto something great.

Here's some info you may or may not find helpful.

https://www.research...e_than_one_time
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#4 Dave Crevie

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Posted 24 May 2019 - 11:59 AM

That site has some valuable info, but you should have a basic understanding of metallurgy to really understand it.

Generally speaking, you should never heat previously hardened or tempered spring steel red hot. That goes for

tool steels, and any alloy steel for that matter, as well. To straighten a perimeter style wing car chassis bending 

it cold is usually best. But if you are experiencing an unacceptable amount of spring-back, you need only to

anneal the metal in the bent area slightly. To anneal the metal, polish it until it is very shiny, then heat it with a

propane or butane mini-torch until it begins to turn blue. Stop heating immediately when you begin to see the

color change, it will continue to get darker even after heating has stopped. Polish it again after the area cools.

Then heat the area until it begins to turn black, and cool it with a very wet rag wrapped evenly around the area.

This will bring some of the temper back, but will not be as hard as it originally was. Normally spring steel is oil

quenched in hardening, but for the guy doing this at home I don't recommend it. Plus re-hardening the frame

in uncontrolled conditions by quench can result in the frame being distorted even worse that it was before. I 

suspect that most wing car chassis are made from 1066 steel, which is easiest to work with and harden. 

Normal hardening temp is 1450 to 1550 degrees F., tempering, or drawing back as we old timers call it, is done

at about 1200 to 1300 degrees. Total anneal comes at 1450. For those of you who want to do some of this at

home, and don't know how to judge temps without fancier instruments, there is a product called Tempel-Sticks

that can be bought from industrial supplies. These are crayons that you mark the metal with, and the mark will

change color at designated temperatures. Takes the guesswork out of it, although well practiced heat treators

can judge pretty closely the temp by the color of the metal. So, have I got everyone thoroughly confused?      


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#5 Dallas Racer

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Posted 24 May 2019 - 04:21 PM

The chassis got bent out of shape while it was at room temp, so you would think it could be bent back into shape while it's at room temp. 


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#6 Highnoon

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Posted 24 May 2019 - 10:21 PM

That site has some valuable info, but you should have a basic understanding of metallurgy to really understand it.
Generally speaking, you should never heat previously hardened or tempered spring steel red hot. That goes for
tool steels, and any alloy steel for that matter, as well. To straighten a perimeter style wing car chassis bending 
it cold is usually best. But if you are experiencing an unacceptable amount of spring-back, you need only to
anneal the metal in the bent area slightly. To anneal the metal, polish it until it is very shiny, then heat it with a
propane or butane mini-torch until it begins to turn blue. Stop heating immediately when you begin to see the
color change, it will continue to get darker even after heating has stopped. Polish it again after the area cools.
Then heat the area until it begins to turn black, and cool it with a very wet rag wrapped evenly around the area.
This will bring some of the temper back, but will not be as hard as it originally was. Normally spring steel is oil
quenched in hardening, but for the guy doing this at home I don't recommend it. Plus re-hardening the frame
in uncontrolled conditions by quench can result in the frame being distorted even worse that it was before. I 
suspect that most wing car chassis are made from 1066 steel, which is easiest to work with and harden. 
Normal hardening temp is 1450 to 1550 degrees F., tempering, or drawing back as we old timers call it, is done
at about 1200 to 1300 degrees. Total anneal comes at 1450. For those of you who want to do some of this at
home, and don't know how to judge temps without fancier instruments, there is a product called Tempel-Sticks
that can be bought from industrial supplies. These are crayons that you mark the metal with, and the mark will
change color at designated temperatures. Takes the guesswork out of it, although well practiced heat treators
can judge pretty closely the temp by the color of the metal. So, have I got everyone thoroughly confused?


Thanks Dave. How about regular non spring steel like flexi cars. Would heating them work or just bend them back by hand.
Gary Cooper

#7 Dave Crevie

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Posted 25 May 2019 - 09:11 AM

I just straighten them cold, by hand. I use a granite surface plate to get them flat when I first build the car, and use

the same proceedure if it gets bent. To bend the chassis I sometimes use a dowel pin chucked in the drill press

and lay the chassis in a drill vise with the jaws opened an inch or two. Lay it bent side up, with the center of the

bend centered between the jaws. It may take a bit of practice to perfect this method, but it works better than any

other way I have tried. Just bring the chuck with the dowel pin down on the center of the bend, and use light

pressure to push the bent area back down.  


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#8 Phil Hackett

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Posted 25 May 2019 - 01:30 PM

Straightening bends with selective heating:

 


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#9 Dave Crevie

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Posted 25 May 2019 - 03:37 PM

That's a bit bigger than what we are doing. Not sure the proceedure scales down to something only .047 thick.



#10 ThunderThumb

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Posted 25 May 2019 - 05:00 PM

No heat as mentioned , bend it cold
Earl Anderson

#11 Phil Hackett

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Posted 25 May 2019 - 11:14 PM

That's a bit bigger than what we are doing. Not sure the proceedure scales down to something only .047 thick.

 

Yeah... it's the method not the scale. What he mentions is where to apply the "fix" is more important than the amount of heat. 

 

Heating 1070 or 1090 spring steel  to red hot only does bad things to the steel. The flexi chassis aren't made of spring steel: they're probably 1018 or something similar so heating them doesn't take the heat treat out of it but the heat can relax the work-hardened bends and edges made by the stamping of the chassis.


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#12 Dave Crevie

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Posted 26 May 2019 - 09:04 AM

The JK Cheetahs are, or were, made from the Chinese equivalent of 400 series stainless steel. Since JK Products

changed hands I can't guarantee that is still the case. Jerry used to have me do a Brinnell hardness test on each

shipment to make sure he was getting what he ordered.



#13 Phil Hackett

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Posted 28 May 2019 - 02:07 PM

The JK Cheetahs are, or were, made from the Chinese equivalent of 400 series stainless steel. Since JK Products

changed hands I can't guarantee that is still the case. Jerry used to have me do a Brinnell hardness test on each

shipment to make sure he was getting what he ordered.

 

Nice to know good metal is used.


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