Rollbar Stays / Cross Member

[SeriesLandy]

I need to order the steel for my roll bar (i have the rollbar, thanks Ash). What diameter cds - seamless should I be using and also the thickness ( the book just says 33.7mm)? Also how much have other people paid (roughly)?

Many thanks

[brainbug007]

I'm in the same boat, been trying to find it but the 33.7mm seems to be an odd measurement that no one near me carries. Is it some sort of imperial measurement? I'm wondering if it's ok to just use 35mm as I can at least get that off fleabay (http://cgi.ebay.co.uk/35mm-Seamless-CDS-Steel-Tube-x-722mm-long-3mm-wall-NBK-/150552098319?pt=UK_BOI_Metalworking_Milling_Weldin g_Metalworking_Supplies_ET&hash=item230d9ab60f)

[Talonmotorsport]

When the car was mocked up as a prototype I'm guessing that the materials used where what Martin Keenan had laying in the steel rack at the time. The roll bar in the book is 33.7mm with a 3mm wall as it's the same size as the suspension bush tube material so I'm guessing he had alot of it at the time.
You don't need CDS for the roll bar stays ERW or even HRS will be good enough as it's the roll bar hoop that takes all the punishment.
The roll bar material can be any thing from 30mm dia. 5mm wall up to 75mm dia 2mm wall, it's your car you can make it out of what ever you want. You could use a scaffold pole if you have a way of bending it, mind you there is nothing to stop you making it 5 bits, welding all together and lobbster backing it.
You don't need to use CDS unless you intend on racing the car as bare in mind the chassis is only 1.6-2mm any way , I would say 2.5mm wall min. would be the thinest I would go.
I've built fully space framed grass track cars from 32mm 2.5mm wall ERW and they hit telegraph poles at 70mph and are still drivable afterwards.
The book is a guide to building a car not the absolute rules.

[brainbug007]

Thats good info, thanks alot. I've got a proper roll hoop from ash and it's just the stays and the bit that goes across for the seat belts to mount on that I need. Would the 19mm stuff the rear end is made out of be ok the for stays? Also do you think i'll need the bar that goes across the roll hoop if I'm planning on using the seat belts out the donor and making the additional back stays with the 3mm triangle plate for the belts to mount to?

[SeriesLandy]

Many thanks guys, I'll be talking to my local eng firm tomorrow and see what I can get. I had a look on Parker steel and a 33.7mm x 3mm wall was £36inc vat for 7m.
If I have to buy a full length (or more) I'll sell the rest. Btw you need 3m if you have a fibre glass tub.


Also what size / length tube do you need for the steering column extension.
Would 3mm wall be about right?

[Richard Dryden]

sorry where did you get your roll hoop itself from

[brainbug007]

I was lucky and AshG was doing a group buy here on the forum. Saturn sell them too: http://www.saturnsportscars.co.uk/store/index.php?_a=viewProd&productId=71

[SeriesLandy]

I also got mine from Ash, his were erw not CDs though.

[flyerncle]

If you look on the MSA website for roll cages suited to the roadster style of car an interesting point is that the highest part of the engine and the roll hoop top are the contact points.

Functional,strong and puposefull for me with some rear protection.


Bear in mind height of the cross bar for seat belt mountings as there are specs for IVA.