Chromoly Chassis HEAT Treating

[Nigel Lavers]

For the teams that have experience heat treating their chromo chassis, I have a question:

What kind of jig/clamping did you use in order to preserve the alignment of your suspension/steering mounts during the heat treating process? i.e. How much deflection did you see?

What about for team's a-arms?

We are going to be treating our chassis in the next week or so, and we want don't really want to "guess and test."

Any suggestions would be appreciated.

Nigel
www.ualberta.ca/~formula (http://www.ualberta.ca/~formula)

[Nigel Lavers]

For the teams that have experience heat treating their chromo chassis, I have a question:

What kind of jig/clamping did you use in order to preserve the alignment of your suspension/steering mounts during the heat treating process? i.e. How much deflection did you see?

What about for team's a-arms?

We are going to be treating our chassis in the next week or so, and we want don't really want to "guess and test."

Any suggestions would be appreciated.

Nigel
www.ualberta.ca/~formula (http://www.ualberta.ca/~formula)

[Frank]

http://www.lincolnelectric.com/knowledge/articles/content/chrome-moly.asp

use an oxy flame

after the whole chassis is built

one weld at a time

you shouldnt see much distortion at all http://fsae.com/groupee_common/emoticons/icon_smile.gif

I believe, after reading, that this is the exact advice Carroll Smith gives in "Engineer To Win".

Frank

"These cars feel great.. SIDEWAYS"

[Nigel Lavers]

Does everyone do it this way?

We were planning on getting together with a local train-car manufacturing facility. They make the train cars out of 4130 and have a massive oven to heat treat them with that we could easy throw our chassis into.

Does anyone follow this procedure? Or is a torch the most common method?

Nigel

[UofM Matt]

For any 4130 that we heat treat, we always use a pretty solid jig plate.

In the case of our chassis, this is the steel jig plate that we build our chassis from. We don't take the chassis off of the jig until it is completely stress relieved. Didn't notice much warping of any of the important points at all as they were jigged throughout.

For A-arms, we also jigged these with a steel plate, but since there are fewer points of constraint and they are farther apart we did notice some slight "spring-back". (Less than .03" though)

[Erik C]

Do you mean heat treat or normalize? Unless you have some very very thin tubing, which is subjected to high bending loads or buckling loads I don't think heat treating is really necessary. I did a stress analysis on our chassis last year and the peak stresses in the main frame members was low. I think the lowest M.S. was 2.2 on a .75" x .035 wall tube. Now, normalizing is always a good practice, it removes some of the internal stresses in areas that have been welded. and as long as the tubes are thin you can use a torch and make the assumption that the temperature difference from the OD to the ID is negligible.

www.adamaircraft.com (http://www.adamaircraft.com)

[Nigel Lavers]

Yeah, that's what I meant... my bad. Those are really two different terms.

The normalizing that we want to do is for stress relieving... nothing else.

I see that a torch would be a simple method... but my worry is that you're not relieving the stress from the chassis at every point at the same time and at the same rate---the level of control is limited. This is what I guess the advantage would be when using an oven.

Thanks for the help... I think I know what we're going to do....