Elliptical Tubing

[BenB]

Does anybody know a good source to buy elliptical tubing? I saw somebody recommended aircraft spruce in an earlier thread, but they only have actual "aero" tubing. I believe it's an airfoil section and also pretty expensive.

[exFSAE]

Yea airfoil profile tubing isn't too hard to come by. It is expensive.

I have never seen eliptical tubing before. What is the application? Why would you want it, especially over an aero profile?

Of course, if it were thin enough and you didn't need long lengths you could hot form your own eliptical tubing from round tube.

Edit - A 5 minute google search produced..

http://www.asti-nc.com/

[BenB]

Sorry, I should have been more specific. I am looking for 4130 elliptical tubing. This (surprisingly) seems harder to find. I am using it to make A-Arms. I actually thought this was more common for A-Arms than aero tube.

[Buckingham]

We used to make our own:

-Purchase round tube
-Machine two die halves of the end profile you desire
- place dies over tube and use a hydraulic shop press to squish round into oval.

The process is extremely simple.

We went away from it because it was inefficient with respect to weight vs. buckling stiffness.

[RiNaZ]

BenB, what type of car are you making this for? Im guessing it's not for FSAE since you already graduated.

[exFSAE]

I have never seen a-arms made from elliptical tube. Aero tube, yes. Round tube with carbon aero "fairing" on it, yes. Carbon aero arms, yes.

Why would you want eliptical over aero?

Or either over round? If you're building a high speed car, certainly go for the solution with the least amount of drag. Otherwise, keep it simple.

[SusProg3D]

The '87 Spice Group C-2 (Pontiac GTP) used elliptical tubing for all the wishbones.

The front upper were made in two halves from flat steel formed over aluminium forming blocks and then welded together.

The other wishbones were made from round tube. Quoting the manual "Round steel tubing is pressed flat in a special jig and then cut and notched as required to accept various fittings."

[BenB]

Thanks for the replys. I think I will go with the aero tubing as ex-fsae sugested. I had the misconception that elliptical tubing would be easier to find and cheaper than the aero tubing.

This is a fairly high-speed application. An elipse is not as good as an airfoil section, but it is way better than a circular section.(easier to analyze and manufacture mating components too) That is why I was looking at the ellipse.

Bob, That method you just mentioned is pretty interesting though. Do you just "tap" the sheet over the die to make the shape you want? Might be a cheap alternative to making a stamped-sheet metal-type of part.

[exFSAE]

The real trick is figuring out how to make rod-end or spherical bearing "ends" for the a-arms.

Well not that much of a trick, but takes a little thought as to how to make what you want, with it being able to fit nicely in that inside tube profile

[SusProg3D]

Ben,

Yes.
Unfortunately the Spice manual is a photocopy and the pictures aren't very clear.

See if you can get a copy of Metal Fabricator's Handbook, HPBooks, Ron Fournier. Mine is a very old copy (1982) but he describes all the basic fabrication processes including using hammerforms.

[Randy]

Just spotted this thread after a search on the web... I'm after a manual for a Spice, don't suppose there would be any chance of getting hold of a photocopy of yours?

[Chris Lane]

Originally posted by exFSAE:
The real trick is figuring out how to make rod-end or spherical bearing "ends" for the a-arms.

Well not that much of a trick, but takes a little thought as to how to make what you want, with it being able to fit nicely in that inside tube profile

Look at any Formula Ford to see a really neat and strong way to do it. I'll dig up a pic if I can find a good one