cymtriks
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| posted on 20/6/03 at 08:21 PM |
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TR tubes are too flimsy!
The title says it all. I'm mainly talking about TR1 and TR2 but they all could do with being 1 inch square 16gauge or 1 inch round 14 gauge. The
book TR1 and 2 tubes are the most slender tubes in the chassis (this has a technical meaning to do with the cross section and the tube length) and
therefore the most prone to buckle. They only hold up the front of the car Ron!
I'm now looking at the stresses in each tube with my new analysis whereas previously I was concentrating on increasing stiffness.
Stiffer chassis actually put a bit more load on TR1 and TR2 so if you've done something to reinforce the chassis this is something that you
might want to think about.
I'm aiming to post a list of the most highly stressed tubes soon.
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Northy
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| posted on 20/6/03 at 08:41 PM |
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Sorry, a bit off topic, but would it be possible for you to do some analysis on the Avon chassis? What sort of a diagram would you need?
From looking at the chassis, I think the sides are good (well triagulated), but not so sure the back end is that brilliant, and this is the bit people
are 'grafting' onto a book chassis for IRS!
Thanks
Graham
Website under construction. Help greatfully received as I don't really know what I'm doing! 
"If a man says something in the woods and there are no women there, is he still wrong?"
Built 2L 8 Valve Vx Powered Avon
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Mark Allanson
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| posted on 20/6/03 at 08:55 PM |
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I don't think Ron was considering crash survival when he chose the tube thicknes and size.
But in my trade, you get to see where major manufacturers put the 'fuzible link' in their chassis. In an accident something has got to
give first to absorb the energy of a crash. I think the TR's will buckle either in or out dependant on the angle of impact allowing the front
tubes to collapse onto the engine. Let them smash up rather than your legs
Can your software simulate a massive loading to the front end? it would be interesting to see how it would behave
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cymtriks
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| posted on 21/6/03 at 07:41 PM |
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Crash analysis
Crash analysis is possible but way beyond lunch break and coffee break time limits. The reason is that stress and stiffness can be determined in one
go whereas deformation followed by more deformation as in a crash requires analysis to be done in steps, each step being a bit more deformation. This
sends the complication of analysis up sharply as there can be a lot of steps to work through to get to a suitably dented shape.
I would expect that the nose cone, radiator and front suspension region would deform first and beefing up tube TR1 and TR2 won't change this.
You have got me thinking though and it isn't too much trouble to add a case for a big load applied to the front of the chassis and see where
things start to go. Where they end up however may be different but at least we will have some knowledge of where the first dent goes.
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cymtriks
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| posted on 21/6/03 at 07:58 PM |
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Avon analysis
The Avon is probably very similar to the Lowcost. I think that the Avon employs two engine bay diagonals from the footwell ends to about half way
along the engine bay. Short diagonals like this, short R tubes in Lowcost terminology, are not as good as one Lowcost style R tube. On the lowcost
going from one R full length diagonal as in the book to two short ones causes a significant drop in chassis stiffness.
In an earlier post I reffered to tube R variations which gives the effect of several different engine bay brace arrangements.
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DaveFJ
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| posted on 23/6/03 at 07:53 AM |
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can you then recomend a few 'impovements' to the off the shelf AVON chassis ?
I shall hopefully be recieving mine soon and, once I have corrected any minor manufacturing 'errors', would like to see if i can't
improve it a bit before I start my build proper.....
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stephen_gusterson
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| posted on 23/6/03 at 09:21 AM |
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The TR tubes are those that go diagonal on the sides of the engine bay?
To me, they always looked way too weak - and in my minds eye I could see them as the only wat to stop the chassis 'banana-ing' at the
front. As I have a heavy V6 they concerned me.
I found a way of getting inch section - same as rest of chassis - to fit. I used TWO bits each side, forming an X shape. As they cross, I welded a
short section between them (as one passes behind other) to give a join at the x-over.
The only downside is that the outer of the two tubes does put a 'curve' in the alu panel, as it no longer allows the tube to sit within
the 'flat' sides of the engine bay.
I also added an 'X' in the side section behind the bulkhead, in the footwell area sides.
Id be interested to know how much this improves things.
atb
steve
[Edited on 23/6/03 by stephen_gusterson]
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MikeRJ
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| posted on 26/6/03 at 08:06 AM |
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quote:
Originally posted by Northy
Sorry, a bit off topic, but would it be possible for you to do some analysis on the Avon chassis? What sort of a diagram would you need?
From looking at the chassis, I think the sides are good (well triagulated), but not so sure the back end is that brilliant, and this is the bit people
are 'grafting' onto a book chassis for IRS!
Thanks
I reckon you are 100% correct. I have an avon rear on a (4" wider) locost chassis, and I think it's probably the least stiff part of the
whole chassis as it has minimal triangulation (something I intend to change!).
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