drmike54
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| posted on 17/9/03 at 09:43 PM |
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Tubing Selection
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?
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Mark Allanson
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| posted on 17/9/03 at 10:04 PM |
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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?
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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timf
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| posted on 18/9/03 at 10:39 AM |
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also dom tube is more expensive than erw and the bodywork would be a complete bitch to fit.
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andyps
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| posted on 19/9/03 at 09:41 AM |
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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]
Andy
An expert is someone who knows more and more about less and less
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DaveFJ
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| posted on 19/9/03 at 10:31 AM |
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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.......
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Simon
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| posted on 19/9/03 at 11:06 AM |
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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
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James
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| posted on 19/9/03 at 02:51 PM |
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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
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DaveFJ
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| posted on 19/9/03 at 03:10 PM |
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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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James
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| posted on 19/9/03 at 04:16 PM |
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quote:
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....
Yeah, no probs, I'll take some pictures- as soon as I find the damn camera!**
She only wears the lycra when I ask nicely tho- normally she insists on the PVC catsuit! 
I bought my metal from chap on here- he couldn't buy less than 60metres or something so 3 of us agreed to split it.
MK certainly used to sell it aswell. I know I bought my outer bush tubing, bushes and crush tubes from them. Just wish I asked them to cut up the bush
tubing- would have saved a lot of filing!
HTH,
James
** For some reason, having sold it to my father he seems to think I shouldn't have free use of it whenever I want!
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theconrodkid
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| posted on 19/9/03 at 04:34 PM |
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i got a length of oval goin spare
who cares who wins
pass the pork pies
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Ben_Copeland
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| posted on 19/9/03 at 05:25 PM |
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Didn't you make a set of wishbones out of some of that john ???
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Alan B
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| posted on 19/9/03 at 05:51 PM |
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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....
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Hugh Paterson
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| posted on 19/9/03 at 08:36 PM |
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Round/Oval tubing
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.
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Alan B
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| posted on 19/9/03 at 09:13 PM |
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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...
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Hugh Paterson
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| posted on 19/9/03 at 10:27 PM |
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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.
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