Danozeman
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| posted on 7/3/05 at 08:02 PM |
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Roll bar thickness.
Whats the recomended wall thickness of the tube for the roll bar? I bought one off ebay and it looks a tad thin..
Dan
Built the purple peril!! Let the modifications begin!!
http://www.eastangliankitcars.co.uk
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Mark Allanson
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| posted on 7/3/05 at 08:14 PM |
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Mine is 3.25mm (1/8" , works for me
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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britishtrident
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| posted on 7/3/05 at 08:48 PM |
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I saw them on ebay --- thought it looked a bit too much like exhaust tube.
I suspect the seller has posted on the forum but only to advertise under the name ARA RACING, the fabrication quality of the other bits advertised
looked fine but I am not sure how much Locost car building experience he really has.
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MikeR
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| posted on 7/3/05 at 08:51 PM |
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I think the blue book (RAC guide) says it should be x mm for y tube. I've done a deal with a mate for some x+.5mm tube.........
worked out for the total lot at something like 10kg extra - but for the protection it brings i think its worth it.
(i did quote x and y but wasn't sure and didnt' want to get it wrong)
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craig1410
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| posted on 7/3/05 at 09:42 PM |
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I think it is 2mm wall for 50mm diameter and 2.5mm wall for 45mm diameter and it must be seamless. I think you would also need to provide proof of the
material used if asked and for motorsport you need some inspection holes drilled in it for wall thickness measurement. Oh, and you also need to ensure
that you don't get any significant ovality when bending. There is a spec for this also which I think is something like the minor diameter at the
bend must be no less than 90% of the major diameter.
Usual disclaimers, check for yourself in the MSA manual.
Hope this helps,
Craig.
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clbarclay
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| posted on 7/3/05 at 10:00 PM |
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For road use any peice of metal will do (legally) as long as SVA don't catch thier ball on an edge etc.
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MikeR
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| posted on 7/3/05 at 10:09 PM |
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for road use no metal will do legally - its not a requirement!
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marc n
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| posted on 7/3/05 at 10:36 PM |
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the minimum we use on our cars is 1 3/4 17 g t45 or 1 3/4 14g cds
we use this even on all road cars as we work on the theory better to be safe than sorry ( after all this is the only protection you have if you turn
the car over ) also has the added bonus of extra rigidity for the rear shock mounts / rear of the car
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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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kb58
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| posted on 8/3/05 at 12:08 AM |
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In the US, for the weight catagory of a Locost, I believe the SCCA requires 1.5", 0.125" wall tubing.
Forget passing SVA and worry about your head, it's just plain good sense to have one.
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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NS Dev
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| posted on 8/3/05 at 08:39 AM |
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quote:
Originally posted by MikeR
I think the blue book (RAC guide) says it should be x mm for y tube. I've done a deal with a mate for some x+.5mm tube.........
worked out for the total lot at something like 10kg extra - but for the protection it brings i think its worth it.
(i did quote x and y but wasn't sure and didnt' want to get it wrong)
Would that be me then!?
Yes, the Rac spec minimum is 2.5mm CDS if you are not an "approved manufacturer" (they can use less as they are judged to have the know
how) and the bar that I will be making for you will be the same as Mark Allanson's, at 3.2mm.
Just checked the weights, the RAC spec min, 45 x 2.5 (or imperial equiv) is 2.62 Kg/m and the 45 x 3.2 is 3.3 kg/m. If you (over) estimate thr qty of
tube needed at 4m, (incl backstays) then its only 2.7 Kg heavier than the RAC tube would be. The total rollbar will weigh around 10 Kg.
As you say, a tad heavier than necessary, but pretty strong, but then as you have said in the past, the bar needs decent backstays anyway, if anything
these are more important as on many 7's, the bars will just fold over in a roll situation, this is where (just to cite two of many!) the MNR and
Stuart Taylor chassis are quite nice, in that they both do decent rollbars "as std"
[Edited on 8/3/05 by NS Dev]
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andyharding
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| posted on 8/3/05 at 09:35 AM |
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I've used 50mm dia 3mm wall for the roll bar and back braced it with the same.
I'm rather attached to my head.
 
Standing under it's own steam
[Edited on 8/3/05 by andyharding]
Are you a Mac user or a retard?
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Danozeman
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| posted on 8/3/05 at 05:56 PM |
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The roll bar i got looks to me like it is made of exhaust tube.. I got it cos it was cheap.. Not from ARA racing i must add all his stuff looks
very good.. Il make the decision to use it when the time comes. Dont think iwill..
Dan
Built the purple peril!! Let the modifications begin!!
http://www.eastangliankitcars.co.uk
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MikeR
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| posted on 8/3/05 at 06:22 PM |
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quote:
Originally posted by NS Dev
quote:
Originally posted by MikeR
I've done a deal with a mate for some x+.5mm tube.........
Would that be me then!?
Just checked the weights, the RAC spec min, 45 x 2.5 (or imperial equiv) is 2.62 Kg/m and the 45 x 3.2 is 3.3 kg/m. If you (over) estimate thr qty of
tube needed at 4m, (incl backstays) then its only 2.7 Kg heavier than the RAC tube would be. The total rollbar will weigh around 10 Kg.
[Edited on 8/3/05 by NS Dev]
Yep - didn't want to mention you again as i seem to keep talking about you!
sure we'd figured out the weight difference was more than a couple kg's.  even happier now. Should be getting round to the roll bar
really soon 
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scutter
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| posted on 8/3/05 at 06:33 PM |
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So the 54mm *5.4mm i've used could be classed as overkill.
ATB Dan.
[Edited on 8/3/05 by scutter]
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britishtrident
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| posted on 8/3/05 at 07:14 PM |
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quote:
Originally posted by andyharding
I've used 50mm dia 3mm wall for the roll bar and back braced it with the same.
I'm rather attached to my head.
Standing under it's own steam
[Edited on 8/3/05 by andyharding]
classy but makes the chassis look puny :-)
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kb58
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| posted on 8/3/05 at 07:28 PM |
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A roll bar is no stronger then the tubing it's attached to. If the car rolls and the small supporting tubes collapse, a big roll-bar
won't work. In the picture, the forward mounts look fine since they're triangulated and paneled. Are the rear-most bottom mounts also
triangulated and paneled? Hard to see.
From a geometry standpoint, having such steeply angled rear supports greatly diminish how well they strengthen the main hoop from bending over
backwards.
Of course in a 7, there's simply no where to go with those rear braces. While they don't hurt any, their effectiveness greatly depends
how well the rear paneling stiffens up those lower rear mounting points.
[Edited on 3/8/05 by kb58]
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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craig1410
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| posted on 8/3/05 at 09:39 PM |
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I'd advise you to be careful and not go overboard on the wall thickness of the rollbar as I think that there is a requirement for the chassis
plate onto which the rollbar attaches to be thicker than the bar itself to avoid punch-through. This may be an MSA requirement rather than a general
requirement but I'm sure I've read it somewhere...
My rollbar is 48mm x 3.2mm wall and I have doubled up the 3mm turret plates to give me 6mm for this reason.
I agree with the comments that the rollbar may not be the weakest link, especially when talking about backstays, and would expect tubes W1 and W2 to
take a battering in a rollover situation. Note that W1 and W2 are specified as 3/4" in the book which is what I used but they really should be
at least 1" and ideally 1"x2" if you are going to use proper MSA spec backstays. My own backstays are Caterham style and are made
from 38mm x 16swg tubing, attaching to the rear luggage tubes. They will add some strength to the rollbar but are mainly cosmetic and to help support
the backend of the chassis in the absence of sturdier W1 and W2 tubes.
Cheers,
Craig.
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clbarclay
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| posted on 8/3/05 at 09:55 PM |
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Page 53 of the second edition book, start of the text on the page goes and I quote
'Cut tubes W1 and W2 fron 1in (25mm) RHS to fit, as shown in drawing, and fully weld in place'
The size of tube is wrong compared to cutting lists/diagrams. I used 1" any way, because I want a good strong chassis, light weight is second on
my list as its a road car.
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craig1410
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| posted on 8/3/05 at 11:17 PM |
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Yes I remember seeing the contradictory specification for W1 and W2 after I had already built the chassis from the cutting list... I would imagine
that most folk would go by the cutting list unless the contradiction was pointed out in advance. Even the McSorley plans which I switched to after
setting out the base-rails specifies 3/4" for these tubes.
However, I am not at all concerned at this as my chassis is all built from 2mm thick steel instead of 1.6mm which pretty much makes up for the smaller
tubing (not quite but very nearly). Also, the rollbar and backstays will add a fair bit of strength.
Cheers,
Craig.
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MikeRJ
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| posted on 10/3/05 at 11:05 PM |
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How are people attaching the roll hoops to the suspension mounting plates, welding them directly on top?
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craig1410
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| posted on 10/3/05 at 11:39 PM |
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Mike,
I welded a second suspension plate on top of the original one to make the material thickness up to 6mm. I seam welded this all round and did a few
plug welds to attach the plates to each other in the middle as well. I then welded the rollbar onto the top of the plates.
HTH,
Craig.
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britishtrident
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| posted on 11/3/05 at 09:03 AM |
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quote:
Originally posted by craig1410
Yes I remember seeing the contradictory specification for W1 and W2 after I had already built the chassis from the cutting list... I would imagine
that most folk would go by the cutting list unless the contradiction was pointed out in advance. Even the McSorley plans which I switched to after
setting out the base-rails specifies 3/4" for these tubes.
However, I am not at all concerned at this as my chassis is all built from 2mm thick steel instead of 1.6mm which pretty much makes up for the smaller
tubing (not quite but very nearly). Also, the rollbar and backstays will add a fair bit of strength.
Cheers,
Craig.
I originally used 25x25x1.2 for W1 and W2 but have cut it out and used 18x18x2 instead mainly because I wasn't happy with the weld design at
the same time I also changed O to 25x25x2 to provide more beam stiffness for the upper seat belt mounts and I hope a little more torsional stiffness
for the spring pad.
If re-starting from scratch I would use 30x30x2 for O as this would make better designed weld at the junctions with K1 and K2.
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