jambojeef
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| posted on 6/10/05 at 09:38 AM |
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Aluminium Rollbar
Hi all,
Any ideas as to whether this has been done and if not why not?
Im trying to avoid having the weight penalty of steel particularly where a roll bar is.
I know ally is softer and it yields less progressively than steel but if it was properly braced could it be the way forward?
Cheers for you thoughts.....!
Geoff
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mookaloid
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| posted on 6/10/05 at 09:41 AM |
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I think if you use something called T45 steel tubing you will be happy with the lack of weight and it will be very strong.
Have a word with Marc at MNR about it.
Cheers
Mark
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BKLOCO
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| posted on 6/10/05 at 09:45 AM |
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If all you are after is the aesthetics then ally or even painted balsa wood (even lighter) could be used. If however you value your life I would
suggest you stick with the steel
Experience is what you get when you don't get what you want!!! 
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zilspeed
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| posted on 6/10/05 at 10:45 AM |
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Aluminium roll bars were banned for MSA purposes some years ago. I know you may never use your car in competition, but maybe that should tell you
something anyway.
I hope that came out the right way.
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jambojeef
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| posted on 6/10/05 at 12:13 PM |
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Cheers for the replies everyone!
In answer to your question BKLOKO Im not looking for aesthetics! I really would like my head to stay on my body in a crash! Just wondered whether
there was any reason for not using Ally based on how it yields or how the actual material behaves when epxosed to the kind of stresses in question.
If Ally can be used architecturally for load bearing sections then why not for a roll bar?
I was wondering if, in order to get it as safe as steel, the gauge and O/D of the ally offset any major weight saving advantage?
Had seen MNR's T45 roll bars mentioned whats the deal with tis stuff? Is it just very strong and you can therefore run a thinner gauge on the
tubing?
Cheers!
Geoff
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mookaloid
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| posted on 6/10/05 at 12:21 PM |
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quote:
Had seen MNR's T45 roll bars mentioned whats the deal with tis stuff? Is it just very strong and you can therefore run a thinner gauge on the
tubing?
Cheers!
Yep that's about right.
Cheers
Mark
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derf
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| posted on 6/10/05 at 02:09 PM |
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What about chromemoly, much stronger with less weight.
I don't thin that you are looking in the right place to shave weight, the rollbar, if you are looking at protection, is definatly not the place.
Try using thinner aluminum side pannels, and lighter bodywork. Ultralight wheels should help alot, so will using a dedion vs a solid rear. An aluminum
floor vs a steel one will shave lots of weight, and so will going bec....
[Edited on 6/10/05 by derf]
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chrisg
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| posted on 6/10/05 at 05:38 PM |
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And cutting out the pies.
This saving weight thing is getting very close to the threads on the sevens list, where people with necks like birthday cakes talk about drilling the
middle out of bolts to save half an ounce.
Very strange.
Cheers
Chris
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JoelP
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| posted on 6/10/05 at 06:54 PM |
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i had a similar problem recently whilst sketching a chassis design, it was finished and feeling 'intergrated', with everything working
well together, but there was no rollbar and no smooth way to add one. I had to bite the bullet and redesign it, including some side impact protection,
and it did add a fair bit of weight. But theres only so far you can go with weight saving, you cant remove the basics 
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MikeR
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| posted on 7/10/05 at 12:09 PM |
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One thing i've heard about T45 is that it can only sustain 1 impact before it loses its strength. normal steel can sustain many inpacts.
Ok, you're thinking that after your first accident you'll be replacing the bar and most of the car but ..... what if you roll? in the .27
of a second between the first and second inpact are you really going to be able to replace that roll bar??????
I'm sticking with good, old fashioned, heavy steel. Like the way my ugly mug sits on the end of my gawky neck too much.
(as usual, someone who actually knows what they are on about and not quoting part of a converstion please post the facts )
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NS Dev
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| posted on 7/10/05 at 12:53 PM |
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I can only quote conversation as well Mike, but it was with Martin Short at rollcentre!
He said that he preferred normal carbon steel cages to alloy steel (T45/Chrome moly, the same thing) because in a multiple roll, the welds in alloy
steel work harden very rapidly during the first impact and then tend to fracture in a brittle mode during subsequent impacts.
Apparently (he didn't tell me this but I read it somewhere) he lost an employee (i think) in a race crash under these circumstances.
Personally, having said that, a multiple roll in a 7 is something not worth thinking about unless you have a full cage anyway. A roll bar would not be
enough, you would still be in very deep sh1t if you went over a few times, the chassis would struggle to stay in one piece to be honest.
As was mentioned, technically ally could be used, but there are several problems. The first is that to get the strength of each section up to an
appropriate level, the section thickness would have to be raised so that the weight was comparable to steel anyway. Secondly, ally (most alloys of it
anyway) also work harden very rapidly and would have problems in multiple rolls. I think it was the multiple impact scenario and several horrendous
crashes that made the MSA ban alloy cages.
[Edited on 7/10/05 by NS Dev]
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jambojeef
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| posted on 10/10/05 at 09:48 AM |
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Thanks for that,
It hadnt really occured to me that during a multiple roll the roll bar would would work harden but I guess there's no way of knowing for
sure...
Cheers
Geoff
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quattromike
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| posted on 22/10/05 at 12:51 PM |
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If money was no object you could give Ron Dennis a call at McLaren and get him to design a carbon fiber one for you .
But let's all hope we never have to test the roll bar 
Mike.
I'll get me coat(?)
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peterriley2
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| posted on 31/10/05 at 09:21 PM |
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i will take that last reply as a joke i think??? i have the recources to make a carbon fibre roll bar, but im not sure that it would take anything
close to the weight of a car rolling, as its a very brittle. titanium could be an opyion with an open budget, but so would a titanium engine!!
if you dont respect yourself, dont expect respect, from anyone else.
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