Straightening a bent chassis......

XXX#40

2A supporter
I agree harrym, I straighten 3-4 chassis a week euro or American they all bend. They can all be straightened. I have a 2500#steel plate table can do anything I want with a chassis.

I too have a 4'x8'x1in steel plate table, also have a 360 degree rotating adjustable frame jig.
If you race just for fun, or a local saturday night track have at it, I never said it couldnt be done, but the chassis changes after all that bending and flexing over its life and no one can deny that
 

GoFast

Member
So what you're saying is when I bend a piece of 4130 tubing in my bender that that piece is now work hardened and won't flex?

It won't flex the same.
That's why some car/cycle chassis/frame builders used to put their work into a large oven, and anneal them before they went to the track.
Probably a lost art now that most serious road race chassis are now monocoque aluminum, or carbon fiber these days.

Hm, why isn't someone making CF kart chassis yet ?
 

harrym

Member
I too have a 4'x8'x1in steel plate table, also have a 360 degree rotating adjustable frame jig.
If you race just for fun, or a local saturday night track have at it, I never said it couldnt be done, but the chassis changes after all that bending and flexing over its life and no one can deny that

How much does 4130 flex on a kart chassis to make it work harden.....does it flex in the same spot every time......probably not. When you bend a piece of 4130 in a bender, how much farther do you have to bend it to get your exact bend.....how much spring back do you have.....say on a 90 degree bend? Unless you are in a crash, normal racing is not going to bend a 4130 chassis....you are not going to put that much of a load on it. Now mild steel or what ever the Euro's use.....maybe.
 

harrym

Member
It won't flex the same.
That's why some car/cycle chassis/frame builders used to put their work into a large oven, and anneal them before they went to the track.
Probably a lost art now that most serious road race chassis are now monocoque aluminum, or carbon fiber these days.

Hm, why isn't someone making CF kart chassis yet ?

Annealing doesn't make it harder, it makes it softer.
 

XXX#40

2A supporter
How much does 4130 flex on a kart chassis to make it work harden.....does it flex in the same spot every time......probably not. When you bend a piece of 4130 in a bender, how much farther do you have to bend it to get your exact bend.....how much spring back do you have.....say on a 90 degree bend? Unless you are in a crash, normal racing is not going to bend a 4130 chassis....you are not going to put that much of a load on it. Now mild steel or what ever the Euro's use.....maybe.

Your kidding right? You can't bend an American oval chassis?
I can prove you can, let me see if I can find the pics of our xxx that wrapped around a fence post.
We go about 7 degrees past the the angle we want with the hand bender, but you forget the bender we use is a cnc bender.
Chassis are designed to flex in the same spot, if it didn't it would be so inconsistent no one would want one.
As a chassis flexes it does work harden and the flex point keeps moving til the point it becomes Un responsive to adjustments "flexed out"
 

GoFast

Member
Exactly.
I never found any hard numbers on what temp they were using, as 50 years ago that was tricks of the trade, and not put into print.
 

XXX#40

2A supporter
1. Is there a difference between 4130 from one source to another?
2. If the OD and ID is the same in a Margay or a Coyote is the steel the same?

I'll say yes there are differences from different manufacturers, or there was during the last 8 years (tariffs) for awhile we were getting tubing from all over the world.
We cut up a bunch of pieces to build chassis, and we mic random pieces and have seen differences in thickness in the wall.
 

XXX#40

2A supporter
In the early 2000s some karting manufacturer's used the term military spec 4130, which was a bold face lie
 

Jimbo

You can fool some of the people some of the time
The tubing is advertised to be 4130 but i'm guessing some could be 4129, 4131 or even farther from the actual 4130.
Please share your thoughts about this and it's effect on the way the chassis works?
 

harrym

Member
Your kidding right? You can't bend an American oval chassis?
I can prove you can, let me see if I can find the pics of our xxx that wrapped around a fence post.
We go about 7 degrees past the the angle we want with the hand bender, but you forget the bender we use is a cnc bender.
Chassis are designed to flex in the same spot, if it didn't it would be so inconsistent no one would want one.
As a chassis flexes it does work harden and the flex point keeps moving til the point it becomes Un responsive to adjustments "flexed out"

read my post, I said unless you crash..... I have 2 laydown coyotes that run very high corner speeds. One is a 2000, and one is a 2001. I have raced these all over the country. Some tight tracks and some wide open tracks. Both of these are as sensitive to adjustments as they were new.
 

harrym

Member
In the early 2000s some karting manufacturer's used the term military spec 4130, which was a bold face lie

There is some junk tubing out there. I only use Plymouth Tubing. It is truely Mil-Spec. I had purchased some supposely 4130, and it had a course finish to it. The wall was inconsistant and when bending a 180.....it snapped in two. And it welded awful. You would be running a bead and it would go up like a Fizzy.
 

XXX#40

2A supporter
There is some junk tubing out there. I only use Plymouth Tubing. It is truely Mil-Spec. I had purchased some supposely 4130, and it had a course finish to it. The wall was inconsistant and when bending a 180.....it snapped in two. And it welded awful. You would be running a bead and it would go up like a Fizzy.

I'd like to have a few different thicknesses of their ProMoly to build a couple of chassis, one for Saturday night racing and the other for day racing.
True Mil spec is expensive.
 

Freezeman

Premium User
I have been straightening frames for 11 years now. But I am located out side of the Denver Colorado area.
 
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