Rorty
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| posted on 18/10/05 at 09:56 PM |
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The shape does look pleasing IMHO, but it's not a practical shape.
Making bends that tight is impossible even with NC benders. As a rule of thumb, the minimum achieveable radius is 3.5 times the tube's OD.
The only way you could make those hoops is by cutting and shutting straight lengths of tube and donuts.
AFAIK, that's how some of the flash looking alloy glam bars are constructed for the back of utes/pickups. The welds are sanded down and buffed
up so they're virtually invisible.
That method of constructing a roll bar is something I wouldn't like to stake my life on though.
Composite roll bars are banned in many classes of motorsport.
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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Avoneer
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| posted on 18/10/05 at 10:36 PM |
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And of all the people to listen to, I'd go with whatever Rorty says (99% of the time - the 1% is when I need convincing).
Pat...
No trees were killed in the sending of this message.
However a large number of electrons were terribly inconvenienced.
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andygtt
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| posted on 19/10/05 at 05:08 AM |
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quote:
Originally posted by Avoneer
And of all the people to listen to, I'd go with whatever Rorty says (99% of the time - the 1% is when I need convincing).
Pat...
be hounest... its the thigh length boots that convince you
Andy
please redefine your limits.
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andygtt
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| posted on 19/10/05 at 05:20 AM |
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Having designed and had my own roll bar made recently for my GT project with rolls and bends, I'd say that those hoops are going to be
impossible to make from one length.
Doesn't mean its not worth asking first though.
As for srength, I'd consider what type of car you are building... the heavier the car the more bracing you need to add.
However I also think a cut and shut roll bar would be a bad idea (regardless of weight)
Andy
please redefine your limits.
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NS Dev
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| posted on 19/10/05 at 11:30 PM |
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my advice, for what it's worth, is a mixture of the above.
1) yep it looks nice
2) it will be heavier than a "normal" bar
3) you can't make it in one piece per "hoop"
4) don't even consider butt welding pieces of tube together to make it
5) the roll bar, though important, is still connected to the chassis under it, which on most sevens is pathetically under engineered for the task of
roll bar support.
placing the inner ends of the hoops into the "middle" of a tube as per the drawing makes this even worse, i.e. the chassis will just
crumple even if the bars hold up on top of it!
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NS Dev
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| posted on 19/10/05 at 11:32 PM |
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PS, at least yours has rear diagonal bracing, just looked at the Donkervoort one!!! Ha Ha Ha now that really is a chocolate teapot!!! Go upside down
in that and the bars will just be like a mousetrap over your neck!
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marc n
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| posted on 20/10/05 at 07:54 AM |
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my two pence worth
1. the bends may be possible we bend 2 x od of tube depends on distance between bends
2. the rear brace is better going to the bottom chassis rail as per your original drawing
3. would go slightly larger on the od tube for the rear stay
4. quite like the shape ( something different )
hope this helps
best regards
marc
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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Avoneer
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| posted on 20/10/05 at 11:04 AM |
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We'll be seeing them on the Vort X next
Pat...
No trees were killed in the sending of this message.
However a large number of electrons were terribly inconvenienced.
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Hellfire
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| posted on 20/10/05 at 12:19 PM |
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So, with roll-bar sorted, now lets consider the side impact protection.
[Edited on 20-10-05 by Hellfire]
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NS Dev
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| posted on 20/10/05 at 12:34 PM |
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heh heh!!
folding pelvis?
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David Jenkins
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| posted on 20/10/05 at 12:37 PM |
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I'm more concerned about rear-impact protection (ooer!).
There's not much between the petrol tank and the outside world, and not much between me and the petrol in the tank, if a following car smashes
into it - even a minor impact. 
Anyone fancy fitting a bumper?
David
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NS Dev
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| posted on 20/10/05 at 12:39 PM |
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nah, not really cos the chassis that it would be attached to would still fold up and burst the tank anyway!.
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David Jenkins
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| posted on 20/10/05 at 12:40 PM |
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Shame - all I need now is a few hundred Pounds for a racing-style fuel cell...
DJ
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NS Dev
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| posted on 20/10/05 at 01:03 PM |
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that's the one!!
just make sure you don't get rear-ended!
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CommanderAce
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| posted on 20/10/05 at 08:05 PM |
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Thanks for all the comments guys, you've definitely cleared up a lot of things for me, I have a new idea forming at the moment that I may share
with you later if it pans out, but for now Hellfire, David J and NS Dev, maybe you lot should be building
one of these if your concerns are side and rear impact protection!!
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paul v6
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| posted on 20/10/05 at 08:13 PM |
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What about machining roll bars/hoops from billet aluminium??
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andygtt
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| posted on 20/10/05 at 08:43 PM |
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quote:
Originally posted by NS Dev
5) the roll bar, though important, is still connected to the chassis under it, which on most sevens is pathetically under engineered for the task of
roll bar support.
I was thinking this but keeping my mouth shut.... there is almost nothing to a 7 style chassis, its nor likelly the chassis will crumple below the
roll bars.
If your really worried and want the look, buy T45 CDS (twice strength of std tube).
Would need anealing to get the bends though so you'd have to heat treat the chassis afterwards.
Andy
please redefine your limits.
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NS Dev
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| posted on 21/10/05 at 10:27 AM |
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I have an RAC approved bar on mine and will be sticking with the illusion of safety that it gives, unless I go road rallying in it, in which case I
guess I will really have to fit a full cage!
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lexi
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| posted on 21/10/05 at 01:21 PM |
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That lady in your Avatar.....There`s no need to suffer PMT now with the new drugs available..
Alex
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