OK, sort of off topic.
I'm fabricating a rollbar for a non-locost project. A friend whose opinion I respect highly (but builds cars using OPM) has suggested I go with
4130 as he's seen instances where mild steel folds up and dies when put to the test.
I called round to the local steel place and they want, gulp, $25.00ft for the 4130 (1 3/4", .083" wall).
I can pick up seamless or erw hydraulic tubing quite reasonably, or special order 1018 seamless. Would these be suitable for a simple rollover bar
(single hoop, two backstays as per Locost) in a 1200lb car? Or should I suck it up and shell out for the "good stuff".
Thanks, Ted
IMHO - it depends very much on the design. Stainless of most descriptions is more suitable for your project as it is less corrosive, and generally
stronger. It's also slightly heavier and as you have discovered very expensive in comparison. I think it's a bit OTT myself... but the
choice (as they say) is up to you.
Dunno what you have at your disposal for bending, but chrome moly takes some shifting.
personally unless weight is a big issue i'd stick with CDS. IMHO a single hoop affair even with cross brace and down tubes, is only a nod in the
right direction as far as saving you in the event of a roll over. If you think there is a high likelyhood of rolling this project, i'd go for the
full cage in CDS.
Al.
Ted,
I built an off-road racing buggy to whatever the sanctioning bodies specs were.(here in the US)
Basically the structure on a sub 1200 pound car was 1.5" x 0.090 wall DOM tubing...regular mild steel...nothing fancy.
Personally I would avoid the Chromoly for many reasons...extra skill/care in welding...cost...etc.
Also, I'd avoid the stainless too....for most of the same reasons, and also have doubts about it's superior strength unless the fabrication
was executed by the book.
Thanks guys, I was really leaning toward the mild steel but needed some outside confirmation.
I don't have any real fear that the car will roll but open cars require a roll hoop to autocross.
If 1.5" would be suitable that would make life much easier as the bender I have access to already has a 1.5" die set.
Thanks, Ted
go for the mild steel. If te worst shoud happen, it can actually be better than high strength grades after multiple rolls. Here the high grades steels
can crack and separate at the welds, whereas although the mild steel cage may bend and distort, it shouldn't crack after multiple impacts.
A leading British Rollcage manufacturer subscribes to this way of thinking for his own cars.
quote:
Originally posted by NS Dev ...it can actually be better than high strength grades after multiple rolls.
quote:
Originally posted by andkilde
quote:
Originally posted by NS Dev ...it can actually be better than high strength grades after multiple rolls.
Oh! (shudder) Dear!
I think after multiple rolls in a Moke they'd have to lock me in the funny farm if I were unfortunate enough to survive.
Autocross is just zipping about a cone filled parking lot, speeds under 40 mph -- a bit like AutoTest but not nearly as cool.
Cheers, Ted
quote:
I've seen more then one car roll at an autocross. They were stock ride height cars on very sticky tires.
I have seen a car rolled Autotesting ;-0
My moneys on low carbon steel also --- I think some of the competition reg requirements for some classes regarding roll cage materials are crazy,
just asking for brittle fracture but I guess they are really scared of wally's who build cages with exhaust tubing.
[Edited on 18/2/05 by britishtrident]
quote:
Originally posted by andkilde
quote:
I've seen more then one car roll at an autocross. They were stock ride height cars on very sticky tires.
Hey! You're not helping at all Kurt
I'd honestly have thought it impossible to roll at autocross speeds without whacking a curb.
Perhaps I just don't drive fast enough...
OK, this is for Land Rovers....
However a lot of the info is common sense, and can be applied to other vehicles.
Have a look at this page Association of Rover Clubs Roll bar info
There is a lot of practical info on making your own roll cage and the sort of info you should consider.
As I said, its for Land Rovers, its the national regulations for Competition Landies. There should be some useful snippets in there. Like bracing, and
gussetting, seatbelt mounts etc.
Its worth a read.
Final word: If you are not exactly sure of what you are trying to do or how to do it, then you must consult a professionally trained expert in this
area. Its a "Mission Critical" safety item, and you cannot afford to make any mistakes.
