11 replies to this topic

[mini-gti]

right i have always wondered some something!!!
do you have to use cds for roll cages/ space frames??
or can the same diameter tube with a larger wall thickness be used?

what are the advantages or using cds?
anyone got any specs or charts for what should be used where????

cheers
gaz

[ed4ran]

I think you could get away with same size normal tubing, but i couldnt find any with same thickness or thicker walls so i just went with CDS.
CDS will be stronger than the equivalent sized normal tube, so its like having larger / thicker tubing but without the weight.

[Pavel]

Is 1" (1.6mm thickness) box section steel fine for spaceframing?
If so, here's a question to all you weldors out there: What's the best setting/electrode thickness to use when welding 2 and 3 mil brackets to 1.6mm thick box section?

[ed4ran]

hmm dont know, i guess it depends how much your using (i.e. how many diagnals and braces you put in. Lots of triangles for strength).

[mini-gti]

you using an arc welder?????????????????? you really want to be using mig

and about the box section it all depends on how your using it?????
loading, stresses but i would have said no

its not very strong over longer lengths!! its a pain in the bottom at work when its in the racks or on the saw bench because it bends and flex's all over the place, but then were talking 7.5m lengths, even still it is ver flexible

gaz

[ed4ran]

the weaker it is the more your going to need so you might end up spending the same amount as it would be to get some CDS which might end up being stronger for the same weight of metal. But then if you've already got the metal or get it free then i guess its cheaper just to use it.

[pikey7]

CDS is used as it has the "best" mix of properties for roll cages in terms of bending/welding/strength/weight. Of course others can be used to create a similar effect....

The question is, what are you expecting from this rollcage? If you want to build an FIA spec cage, you can do, but you'll never get it FIA approved (I believe you have to be an accredited roll cage manufacturer for that). You could build one and have it MSA nationally approved for motorsport, but you'll need an MSA blue book to verify the sizes and materials you need to meet the requirements for your class. Then there's a road cage. Basically you can do what you want as long as it isn't dangerous to you, your passengers or pedestrians......

[mini-gti]

just basically a race style cage, but will also support the engine in a craddle

i will copy the one in the race fiesta that i built (pics in my project page) but obviously adapted to fit my mini

just abit cun-fuzed about which tubing i should be using

the car will be used for track days mainly, but also some fast road, possibly sprinting and time trials

gaz

[pikey7]

Beings as you're going sprinting, I'd get your hands on a copy of the MSA blue book then.....

[mini-gti]

Beings as you're going sprinting, I'd get your hands on a copy of the MSA blue book then.....

so if i dont do sprinting then can just use normal tubing?

gaz

[pikey7]

Theres no reason why not., but I wouldn't base your choice of material on that fact alone.

Any form of organised motorsport will have rules for the construction of the car and it's safety equipment. The equivalent of which for the road is the SVA and MOT tests and handbooks.

Regardless of whether you decide to take it into MSA run events, you need to be sure that the car is safely constructed and won't be dangerous. The reason that the FIA/MSA has certain standards is not just to be pedanatic, but to ensure that in the event of accidents the constuction of the cage (be it the material, welding, design or whatever) is left as intact as possible, and those parts that do "give" don't pose threats to you, your passenger or anyone else.

For me, the MSA blue book will give you an excellent guide of what the minumum standards are for british motorsport. There's no particular reason that they should be different to the FIA or even the MOT/SVA specs, but they probably are in the details! however, it will give you a good base for a proper safe design no matter what tubing you use.

CDS is ususally specced for the reason that it is very hard to burst (the tube secion to open up) due to it's manufactuing process. Other tube processes may not have those properties, and as such you will need to go up on wall thickness to compensate for those losses, which will then compromise you on weight. You'll also find that although CDS is relatively expensive, by the time you've paid for a "lower spec" but thicker tube, you're not too far away!

I'm also a little unsure on the availability of tubing in different specs these days. I now last year, I was doing some stuff for Volvo which included getting some decent spec tubing. We had great difficulties in getting our hands on the stuff we wanted due to the fact that the manufactuiring plants in Asia wer geared up for running off scaffolding tube In preparation for the Shanghai Olympics! Crazy!

Anyhow, I digress. Summing up, yes you can use different tube, but be aware of its capabilities before you use it. And remember this: CDS is used by FIA approved cage suppliers for a reason.....

[Pavel]

Don't want to guide you away from TMF but I suggest you go to www.locostbuilders.co.uk PLENTY of people there that build spaceframes and roll bars etc. etc. so they know what they're talking about. Post your specific needs etc. and chances are they'll help you out.