roll cage

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Keith 'Supaimpy' Laming
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roll cage

Post by Keith 'Supaimpy' Laming »

if you want to use a cage in competition it needs to meet msa regs.

you'll find the diagrams and specs in the blue book
Keith
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imull
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Post by imull »

no offense but that is quite possibly the most horrifying piece of advice i have ever seen passed out :shock:

the Blue Book sates either 45x2.5 or 50x2mm tubing. Go for the larger on at least the main hoop and if possible the rest too. It provides far more resitance to deformation than the smaller size due to second moments of area and is also lighter per unit from memory. If you have any spare cash get T45. You can (with mathematical proofs to the MSA) go below the minimum dimensions and so long as the design passes the tests, you will be allowed to use it. Several members on a Focus WRC are 30x1mm!!!

Never ever ever use something like exhaust tubing for a stress resisting function as it will split along the weld and deform at a very very low impace force which will in turn affect the abiolity of the rest of the cage to perform to its best and also provide a huge danger to the occupants, especially bearing in mid that the bars you have been advised to use this for are right about the occupants head!!!!!!!

If you are going to do it, do it proper!
imull
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Post by imull »

If you have access to trade rates, I would go for T45 if you seriously intend to do the job properly. Its the choice of all WRC teams and is marginally better than the Amerincan 4310 Chome Moly tubing...

Investigate heat treating issues, but I know that is why the European teams use it over 4310 as it (4310) has to be relieved after welding...

Not as cheap but a benefit in every way.
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rootes
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Post by rootes »

do scrutineers require some sort of test cert?

Si
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imull
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Post by imull »

Chromoly and T45 are totally different materials with different behaviuors. It just happens that they are almost the same when it come to yield stress. I dont think that you need to stress relieve a T45 cage and you can definitely weld them up in the car. Most cage makers either cut holes in the roof to weld round the top of the bars or in teh floor to drop the cage and weld round!!!

If you choose to go smaller (in diameter or wall size) than the blur book states in Q1, then you must provide engineers calculations! John Ryan is the person to speak to at the MSA. If using T45, then you will naturally be doing this and also probably using a lot more triangulation than normal.

FIA test loads are 7.5g + 150kg vertically distributed over the main hoop (might be a point load but dont think so - too tired) and a point load of 3.5g + 150kg on the top of the front leg at a certain angle. You can download the test data off the FIA site. Its safety factor (150kg) is marginally higher than the MSA one...

If making it, take a V up to the centre of the main hoop and aV across the roof. much stronger and resistatn to deformation than the common 'X' design, though you need to think a wee bit about the front half of the cage

pic will follow in technical gallery (excuse teh crappy quality of eh sketch :P
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