Roll cage- Weld in Vs Bolt in

Roll cage- Weld in Vs Bolt in

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Henry Fiddleton

Original Poster:

1,545 posts

111 months

Tuesday 20th December 2011
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Hi Chaps,

Not sure if this should be in the UK Motorsort section or not.

Looking at getting a race car soon, and obviously a weld in cage (to the front struts) is proper job but a lot of the converted road stuff use bolt in.

Does the weld in cage make the car signigicantly stiff and better on the corners etc?

For example, a 1.8 Fiesta road converted with bolt in, Vs a 1.4 with a factory weld in- same price ish. Once is better on the straights, the other on the corners.

Also hoping I wont need to use the actual roll cage..ever!

Thanks,
HF

FWDRacer

3,532 posts

158 months

Tuesday 20th December 2011
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I've tested the structural integrity of a good weld in cage. I'm glad it wasn't bolt in only. The torsional stiffness is much improved - but the biggest improvement is being able to walk away...

Henry Fiddleton

Original Poster:

1,545 posts

111 months

Tuesday 20th December 2011
quotequote all
FWDRacer said:
I've tested the structural integrity of a good weld in cage. I'm glad it wasn't bolt in only. The torsional stiffness is much improved - but the biggest improvement is being able to walk away...
Good to hear you walked away. I have seen plenty of crashes with bolt in and they appear to safe, right? I mean the MSA dont require weld in. Agreed they would be safer, but a safety wise I imagine a bolt in being enough.

Its a shame proper race cars with weld in cages cost a fair bit more than I can afford!

MrKipling43

5,788 posts

150 months

Tuesday 20th December 2011
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If you do go bolt in, make sure you check the mounts. I've seen a pic of a rolled car where the bolt in cage punched through the floor pan - imagine pushing a fork through a piece of cheese - and essentially did sod all in terms of protecting the occupant.

jamescodriver

356 posts

127 months

Tuesday 20th December 2011
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Having crashed in both (as a codriver) the weld in cages create (this is going to sound stupid) much more of a safety cage, but they also add far more rigidity to the shell, most are welded through to suspension pick up points and of course the pillars.

The bolt in cages all have to meet RACMSA saftey requirements and will do the job.

If you are going racing i would be looking for a weld in cage particularly one with the X-type door bars. Race cars seem to suffer from being T-boned quite a bit and i'd want as much between me and the t-boner!
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Henry Fiddleton

Original Poster:

1,545 posts

111 months

Tuesday 20th December 2011
quotequote all
Thanks for the advice chaps- looking at buying a preparred race car so wont be doing the work myself.

Will do my best to pick up a welded in cage.

Regarding the door bars- I think its MSA requirments to have a two bar cage, the one bar type look weak at best!

Max_Torque

12,744 posts

151 months

Tuesday 20th December 2011
quotequote all
The only advantage a bolt in cage offers (other than a very slightly lower inital purchase cost) is that if you have a little biff (say a take a front corner off into the barriers etc) a then you can take the cage out and stick it in a new shell easily. So if you have a mass produced bodyshell which you can source cheaply and easily, and a race in a lightly modified class, then it becomes a simple and cheap option to reshell the car in the event of an off. Otherwise, there are so many man hrs in a proper welded in cage, that you will pretty much either be repairing the shell you have or replacing both shell and cage after a crash.

Of course, if you do the job properly, then you might well be replacing both anyway in the event of a larger accident.

Personally, i wouldn't race or rally with a bolt in cage due to the inferior side impact capabilites of the less well interconnected bolt in cage types.

thunderbelmont

2,981 posts

158 months

Tuesday 20th December 2011
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Weld-in most definitely. Unless your series regs don't allow it.

This mallarky about doorbars would be much better if they mandated a bar linking the legs of the main hoop at about 6" above the floor (or tunnel height) tied to the tunnel. It would give more resistance to side impacts than just the double door bar.

Having seen the affect of two very serious side impacts - one rendering the driver of one incident in hospital with a broken pelvis - a lateral bar would have saved him a lot of pain!


N24

1,107 posts

173 months

Tuesday 20th December 2011
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I wouldn't let a bolt in cage put you off entirely - these can also have welding added to strengthen the bolts - however I'd certainly agree with the comments above - welded in gives you added protection, as do cross braces & 'gussets' between the bars.

JontyR

1,707 posts

101 months

Wednesday 21st December 2011
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Max_Torque said:
The only advantage a bolt in cage offers (other than a very slightly lower inital purchase cost) is that if you have a little biff (say a take a front corner off into the barriers etc) a then you can take the cage out and stick it in a new shell easily. So if you have a mass produced bodyshell which you can source cheaply and easily, and a race in a lightly modified class, then it becomes a simple and cheap option to reshell the car in the event of an off. Otherwise, there are so many man hrs in a proper welded in cage, that you will pretty much either be repairing the shell you have or replacing both shell and cage after a crash.

Of course, if you do the job properly, then you might well be replacing both anyway in the event of a larger accident.

Personally, i wouldn't race or rally with a bolt in cage due to the inferior side impact capabilites of the less well interconnected bolt in cage types.
Personally, I would treat a rollcage in the same way as you would treat a helmet. If it has done its job, throw it away! There may well be cracks you can't see that would flair up in the event of a further crash! Obviously you wouldn't do this in a minor impact, otherwise where do you stop on the throwing away?? Chassis??

I have seen some horrendous installation jobs with cages, but not only that, seat rails and harness mounts. People forget that the area around the bolt needs strengthening. If you bolt through cheese, then you may as well be using bolts made from cheese! So the same can be said about the bolt in cages. If you weld in plates around the chassis points then bolt through those, then the cage will be good to go. Ferrari challenge cars all use bolt in cages, as do a good number of other cars. That said....I would rather have the car put on a jig, and a welded cage put in. That way you know the car is straight, and it will stiffen the entire car so yodon'tnt get chassis flex.

CNHSS1

938 posts

151 months

Wednesday 21st December 2011
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the grade or quality of a bolt is a known quantity (its stamped on its head!), whereas DIY welding is of infinitely variable quality. Im sure youve all seen welds that looked OK, esepcially when painted over, but will fail with almost no load or effort (just my welding then rolleyesbiggrin).
Given that the regs are a 'one size fits all' attempt, better a known quantity than one thats questionable, albeit likely to be better when done correctly. A scrute can check a bolt with a visual check and a spanner if he wishes, can check the true integrity of a weld as easily in the scutineering bay imho


onomatopoeia

3,464 posts

151 months

Wednesday 21st December 2011
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It should perhaps be pointed out that not all cars can be welded to wink

The cage in my Clan is bolt in. The cage in my Davrian, I don't know. It's all glassed in and you can't even see the feet and the only bar you can see is the diagonal (the shell was built around the cage, rather than the cage being added after).

JontyR

1,707 posts

101 months

Friday 23rd December 2011
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onomatopoeia said:
It should perhaps be pointed out that not all cars can be welded to wink

The cage in my Clan is bolt in. The cage in my Davrian, I don't know. It's all glassed in and you can't even see the feet and the only bar you can see is the diagonal (the shell was built around the cage, rather than the cage being added after).
Have you looked at all of the settings on your mig welder? There is a setting on there for welding CDS to Fibreglass


deviant

4,316 posts

144 months

Friday 23rd December 2011
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A chap I know had a bingle in a car with a bolt in cage. It was a very big impact backwards in to the barriers with enough force to break the seat back, he struck his head on a bolt in the cage which punched a hole in his helmet just behind his hear, thankfully he got away without injury but a new found respect for safety on track.

I would ask the owner of any car you look at exactly who did the design of the cage and who welded it. Would an amateur builder go to the effort of getting welds to go the full circumference of the tubing between the cage and the roof or pillars? There are only really two ways to do this...build a cage and then build the body shell on to it or the cage is constructed inside the car, holes cut in the floor to the entire lot can drop down low enough to do the welds and then it is all lifted back up and the floor patched up. A good cage will take hundreds of hourse to design and install.

Did the builder investigate any inherent weakness in the type of car?

Having said all of this...if the car did not need the added stiffness of a weld in cage I would be happy to run with a bolt in cage. The strength comes in the traingulation and bracing, a cheap bolt in 6 point cage might only have a single cross in the main hoop where the more expensive one has door bars, roof brace and a main hoop brace.

JontyR

1,707 posts

101 months

Friday 23rd December 2011
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Custom Cages require a sample of the welding prior to issuing the certificate.