Has anyone ever tried using 1 inch round DOM Tubing for a chassis? I was thinking that by the time you add a proper roll cage into the structure that most of the car would be round tubing anyways. Or is it just to much extra work to cut the fishmouths and weld?

You would have to use larger section round tube to compensate for the inherrent weaker round tube. Try counting the number of joints (I have better thing to do)but it must run into the hundereds, you could extend the chassis building part or the build from 5% to 50% - bugger that - 25mm ERW works fine - why change it?

also dom tube is more expensive than erw and the bodywork would be a complete bitch to fit.

There is a locost built from round tube - I was talking to the builder/driver when he was competing at Harewood Hillclimb this year. He used round tube because he got it free, but he did comment that it took a long time to make soem of the joints and that square would have been easier.....

[Edited on 19/9/03 by andyps]

Kind of related to this thread - Has anyone tried using Oval section tube for thier wishbones ? - I'm not even sure how easy this is to get hold of.......

There was quite a lot of talk about oval section for wishbones earlier in the year/last year.

Believe MK sells/uses it on Indy

Others may know of alternative sources.

ATB

Simon

I've made 6 of eight out of oval tube. The top fronts aren't as the width of it causes issues with mating to the threaded bar for the top BJ.

It does add some difficulties to making the wishbones but none that are insurmountable!

Cheers,

James

Any chance of putting a couple of pics in your archive James? - more of the TVR woman would be nice but your wishbones will do I spose....

quote:

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Originally posted by protofj
Any chance of putting a couple of pics in your archive James? - more of the TVR woman would be nice but your wishbones will do I spose....

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i got a length of oval goin spare

Didn't you make a set of wishbones out of some of that john ???

Square inherently stronger?

Got to disagree here....there are many ways of comparing one to the other and round wins more of the categories.

In tension, weight for weight...identical
In tension, size for size square wins but is also heavier.

Same goes for pure compression.

Pure compression failure of thin tubes is unlikey and buckling would occur first.
Round is better in buckling (weight for weight)

As for ease of manufacture, yes the fishmouths are a pain until you have a tool...then they are easy.

Ever tried a compound angle joint of same size square tube?.......it cant be done without getting ugly, whereas round will always word and look right.

I do agree to use round on a book locost would be a pain...it would need a redesgn really...so isn't practical.

I've made dozens of chassis both round and square/rect so I'm not biased...just offering my observations....

The Coram has used both Round and Oval tubing for wishbones, I will ask Steve to post a picture for u all to have a decko, I suspect however he will be posting a couple of shots of the uprights for Alan B to have a looksee at them, I suspect the wishbones will show up on them.
Whenever I find time (Ha ha) I will be building the +4 McSorley chassis in CDS, What design changes do u have in mind Alan, if ya dont mind swapping notes u2u or e-mail your suggestions, I was however going to beef up the front by putting more triangulation in it, still pondering the rear end a bit as well, but that will depend on the pick-up points for the IRS, that may or may not be based on BMW running gear? Thoughts anyone!
Shug.

Shug,

My redesign comment was a more general remark rather than any specific suggestions..I'm not really familiar enough with the locost/seven frame to be constructive without studying it more.

In general like with many material change exercises, you don't just do a straight swap if you want the best results.....you redesign to suit material properties, and square to round is no exception.

The round tube choice offers many new options and new challenges, and often can work well combined with square/rectangular sections (caterham?)....

About 20 years ago I worked on many chassis designs with a great ex.TVR guy (who afterwards went back there) I learned a lot from him (Hi Terry if you are reading..)

He showed me many simple, elegant bracket and joint designs which were very safe and reliable....example: for brackets that have bolts running parallel to the tube axis (front wishbones ) you simply make pear shaped brackets with two holes...one hole for the bolt and the other to slip over the tube...so even if a weld failed (very unlikely because there was lots of it) your bracket would not fall off.

We used quite a blend of round, square, rectangular and flat sided oval.....and that can help..using square where helpful (panel mounts) using round where helpful (compound angles etc.)....

I'm rabbiting on bit, but I hope that helps somewhat...

Alan, interesting stuff, I have a friend who was at TVR too, not sure if he still is, but have his number and keep meaning to give him a buzz, good pointers though cheers.
Shug.