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Old 14 Jan 2004, 16:14 (Ref:838100)   #1
zefarelly
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roll cages . . . .bolts VS welds

just following on from onlookers post in the seat fixing thread.

Historics, certainly to FiA spec have bolted cages, it would appear many people weld their cars and cages to within an inch of their lives . . . .presuming you can make a shell for example stiffer by welding, its also likely to rattle to bits in the long run,

a well prepped and bolted cage should tighten it up significantly, but considerable less than welding ?

what do people have? use? prefer?

for arguments sake lets just assume a 6 point cage with door bars (about average I guess on track cars)
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Old 15 Jan 2004, 04:04 (Ref:838834)   #2
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Welded steel is the practically strongest - that's what the pro teams use - but either welded or bolted, the cage is only as good as the mounting points. It seems that bolted cages don't always have the same care and attention put into their 'feet', which could be what lets them down (not the means of attachment per se)

Am currently investigating cages for my Alfa. Current thinking is not to bother with a cage until I can afford to go the whole hog and have a proper welded cro-moly cage installed.
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Old 15 Jan 2004, 04:32 (Ref:838849)   #3
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Originally posted by GTV27

Am currently investigating cages for my Alfa. Current thinking is not to bother with a cage until I can afford to go the whole hog and have a proper welded cro-moly cage installed.
Far better off in the long run,the other upside to a welded cage is that you don't get as bad damage in big accidents to the floor and rail area of the car,as the load spreads over the whole car.You may not even get the same load transfer at joints as a weled cage.Those clamps don't look to be rocket science stuff so maybe there are losses and gains a varius points ( some one with a better idea of 3D statics than me may know )This may effect the handeling of the car,just like bar placement does,by bolting you are somewhat limited in where and at what angle you can put bars and so thus you are not going to be attached at the exact point that the forces are acting.
The big plus for the bolt in is the removablility of it should the car be sold to make way for another of similiar model for instance.
If you are serious you weld and if you are doing it for fun and don't want to be stuck with a caged car at the end you bolt
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Old 15 Jan 2004, 09:25 (Ref:838999)   #4
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welded cages do tend to be multi point affairs, although for bolted you can weld parts together such as the rear end . . .as long as you can get it in the car !

I spent quite a bit of time making sure my cage mounting points where spot on, the main hoop has 3mm thick fabricated sections welded to the inner sill, floor and cross member behind the seat, this actually came with the cage (thanks to a certain Mr Short) and just needed a minor amount of tweaking and some careful prep to fit.

some of the bolt in cages Ive seen, I believe, would tear away from the car at the slightest provocation, so not only unsafe but not doing the shell rigidity any favours either.
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Old 16 Jan 2004, 01:27 (Ref:839878)   #5
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zefarelly, what do you think of your rollcentre cage? I hear widely rangine mixed report over thier prodect, but they are the only people that list a cage for my car...

There are good arguments each way. Welding is stronger but makes the surroundings brittle. Bolting can be as strong, if not stronger, but in a large impact is more likely to fail (from what I have read)

weld in cages need not be multi point. they are quite often the standard 6pt cage. as GTV said, any cage is only as good as its mounting points which are generally going to be thier weakest point.

I would weld mine in but the car is fibreglass (no matter what the rollcentre site says!)
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Old 16 Jan 2004, 02:56 (Ref:839922)   #6
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Welded cages are effectively just as removeable as bolted cages - just use an angle grinder instead of a spanner. Refitting to another car is not as easy though.

You'd probably get away with a bolted cage if you were just after a safety device, but for performance (ie stiff chassis), welded really is the go.

I know of some "cheap" bolt in cages that have been welded and extra bracing added to good effect. This may be the route that I take, depending on the quality of fit for the prefab bolted variety. There's not a lot of room inside a GTV and I can't afford to have an illfitting cage or I wouldn't fit in the bluddy thing (actually, given the cost of the cage, at the moment I can't afford ANY sort of cage ). Anybody want to sponsor a fast GTV in the Alfa Club Series?

I drove a GTV with a "proper" cage and effectively the same spec suspension as mine and it felt HEAPS better. It could carry much more corner speed and didn't move around under brakes as much (I guess my chassis is flexing more than I'd realised ). I'll have to rely on a horsepower advantage again this year and hope nobody has been to see the engine doctor for a dose of the good stuff
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Old 20 Jan 2004, 12:03 (Ref:843911)   #7
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imull . . .Id recommend the roll centre, they where good to deal with, most importantly it fitted and the car certainly seems stiffer all round

I had a TVR Vixen with a cage that went through the body, and bolted to the chassis, that was by far the best way to do it for that type of car, I guess if you have a FG monocoque like an elite for example, or an early TVR with bonded chassis its a different matter, perhaps bonding the cage to the body, and your seat is the safest thing to do ?
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Old 20 Jan 2004, 18:11 (Ref:844333)   #8
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I hav a Clan.

The front legs seem to bolt in on a right angle plate to the floor and another panel with a reinforcing plate on the underside. The rear legs bolt down on to the strut top for the reat dampers and main hoop on the subframe. At least tahts how it worked on my old Aley bars cage...

There very little height to play with in a Clan so raising the seat is not really an option. Fortunately, for stage rallying, the entire floor pan has to be skidded in Duralumin or similar so there will be a very larde supporting plate...
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Old 26 Jan 2004, 10:09 (Ref:850775)   #9
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We built our cage into the car. Any floor plates are both bolted and welded, the bolts helped to locate the plates in the correct position before welding. Additional strengthening has been added by fitting small plates from hoop to original upper seatbelt mounting point, etc.
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Old 29 Jan 2004, 10:55 (Ref:854926)   #10
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another twist . . . . . .bolting the cage in to welded reinforcements . . . .then welding additional sections into the cage, should help stiffen things up a bit more, without breaking the rules, obviously if you needed to remove the cage you'd have to cut these out though.
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