Making a roll cage.

[Timrxmotors]

Having the fastest street rx7 in the UK,that is my 12A turbo gen 1,I am considering making a roll cage for it.Bit of a dilemma,because it is still a street car,I use it almost every day.There is a huge thread on RX7club.com arguing that you should never drive a rollcaged car on the street,because of the increased danger of bars everywhere,especially near your head.That is unless you wear a helmet all the time.Any thoughts?
I have bought some chromemoly 4130 tubing,and a hydraulic pipe \'bender\',and found it is very good at folding the tubing!
Then I got a copy of the MSA rule book,which states that min spec for a roll cage is 45mm tubing,2.5mm thick,what I have is 44.5mm,2.4mm thick.
What to do next?

[MikeLMR]

Its best to stick to what the MSA specify otherwise its a total ball ache to ever get it approved by them.

What state is the tubing in ? if its still in the as drawn condition it will be very hard. The usual method of bending the tubing is to heat the tubes to normalise the section to be bent and then bend them which should in theory work harden the bends again.

I\'m not sure what the score is with chromoly though ... its apparently strange stuff to work with.

you have to be wary of how distorted the tubing is after bending too, the MSA specify a limit on how much distortion is allowed. A mandrel bender is the best way to bend them, but then they cost a fortune!

[Timrxmotors]

Oh,looks like I need some more tube then,or a thick coat of paint!
Not sure about heating the tube,it may never be as strong again.Think I\'ll get some tube that is easier to bend,and if that doesn\'t work,make a pattern and have the bending professionally done.

[oldone]

There is a shop in Stratford upon Avon,owned by Mr.Rathbone...he just makes the ultimate rollcages....being a serious drag racer he know the specs wanted by MSA....he mainly builds beetles.His work is real good,in actaual fact a state of art.
If the rollcage looks professional and in good nick,will MSA scrutineers really have a bother ?.Taking it, I held a National Scrutineer License up to 2002/3...looking at a car you just know which ones are safe and which ones are unsafe. :Typing

[MikeLMR]

Era, I\'m going on the experiences of John Beardmore (check this out //www.beardmorebros.co.uk ) because his roll cage was not an MSA approved design he had to prove it was adequate before they would log book the car. The MSA are starting to get a bit twitchy about home builds which is a shame

Tim, anealing the tubing if it is in the as drawn condition before bending is common practice as far as I can work out. It is most likely the reason why your tubing is folding rather than bending. As I said before I\'m not totally sure on Chromoly but I know this is the case with the standard issue CDS roll cage tube.

I\'m sure a roll cage place would bend the tubes if you made them some templates.

[Gman]

I had a half cage that was covered in padding, it protected ok if you accidentally hit your head on it but not sure about a full impact (luckily never rolled it)  If might me worth while seeing what kinds of padding are available.

[MikeLMR]

some interesting discussions on here ... http://66.102.9.104/search?q=cache:TpVkglqIgmEJ:www.nsra.org.uk/forum/topic.asp%3Fwhichpage%3D-1%26TOPIC_ID%3D3242%26REPLY_ID%3D15531+bending+cds+tubing&hl=en

its looking more and more like a non DIY job.

The way I look at it is, would you rather hit your head on a padded roll cage or have the roof come down and hit you on the head ?

[zevans]

Rollcage implies harness too, right? In which case, the main problem you will have is visibility at T-junctions, especially in 60\'s-shaped coupes with long bonnets and low floorpan, like wot we have got.

Could you weld in bolting points and take it in and out for events or road use?

[bin liner]

Chromoly is tricky to work with and needs the correct heat cycling when being welded.
Best bet is to use t45 or DOM tube, although DOM is not readily available in the UK.I had some imported over from the states which worked out ok.
Pipe benders are very crude and not suited for tube bending, a decent tube bender cost 1500+ i just invested in one.Lovely tool.

[BlitzBoy]

Having the fastest street rx7 in the UK,that is my 12A turbo gen 1

Not for long lol

Ok here are some MSA specs for roll cages

tube diameters (for main hoop; currently 45mm x 2.5mm thickness or 50mm x 2mm thickness or 38mm x 2.5mm thickness or 40mm x 2.00mm thickness for bars tested and approved by MSA prior to 1/1/1995) and
material type (Cold Drawn Steel).

the MSA advise (for very good reasons!) that the top of a fitted roll over bar must not be less than 5cm above the helmet of a normally seated driver.

[oldone]

Another person to make contact with is Andy Robinson Motors....he builds those ultra radical 7 sec v8 dragsters.Was once the Euro record holder,his cars must be MSA legit....just a thought.

Mike: i hear what you say...that means i will have to redo the cage in the lil 2 at some pro builder to get MSA approval ?

There was another comment on this thread about banging yer head on the cage......had a 210 kph accident in a road car,played ping pong of the road barriers..had harness on but bashed my head on the door pillars.....
Had a 230 kph crash on the race circuit,bashed my helmet on the padded roll cage......result severe concussion,bleeding from the ears etc....so the point is adhere to MSA specifications !!!!!!!!! :Typing

[MikeLMR]

Era, not sure on the RX2. When I bought the cage for my 323 it came with a certificate to say it complied with certain regs. I guess thats what an MSA scrutineer is after ? It hints about it in the clipping from the blur book above

"for bars tested and approved by the MSA" i.e the rules for scratch builds are different to the pro made cages that have been tested by the msa (not an option for a one off!!)

[oldone]

I see the point Mike... :Typing

[Timrxmotors]

some interesting discussions on here ... http://66.102.9.104/search?q=cache:TpVkglqIgmEJ:www.nsra.org.uk/forum/topic.asp%3Fwhichpage%3D-1%26TOPIC_ID%3D3242%26REPLY_ID%3D15531+bending+cds+tubing&hl=en

its looking more and more like a non DIY job.

The way I look at it is, would you rather hit your head on a padded roll cage or have the roof come down and hit you on the head ?

Mike,thanks for that link,some really useful info.
I have found my pipe crusher bends 1" tubing really well,so I think I will make a pattern of the front and rear roll bars,then have the chromemoly tubing bent properly,at \'Technical tubes\'.All the other bars are straight ones.
My concern is the bar running past my head is way too close,so somehow it will be within the roof,but won\'t really know how until I strip the car out.

[MattR]

I am going to use a custom cages kit... with the help of my friend.. in fairness its a bit ott or everyday use lol... i dont have any issues running a cage everyday long as its well padded... good look tim... pic attached is an example of the cage going in mine..

Cheers

Matt