Can someone help me out with the minimum regs for local MSA events such as hill climbs.

I have a new roll bar made in seamless tube which is just under 50mm dia and approx 3mm thick wall. Its not welded in yet so I want to get some details correct.

Is it correct to take a line from the front upper "hard"point to 50mm over the top of the drivers head to get minimum height of the bar???

I want to put in 2 rear braces back to the lower chassis, I believe these can be in smaller dia. Is this true and what Dia and do they still have to be seamless?

I also want a diagonal on the main bar, again what diameter?

Any help greatly appreciated as I want to get this welded in this weekend.

Sure you are right about the height bit and i am sure to meet msa regs the tube has to be cds for the rear stays and be the same size if you don't want to get into having it certified.......i might be wrong though

For main hoop; currently 45mm x 2.5mm thickness or 50mm x 2mm thickness or 38mm x 2.5mm thickness

Diagonal should be the same material as are the stay bars. 2" above your helmeted head for height.

You really need to consult the MSA year book to be 100% correct.

Diagonal should go from top corner to foot plate on main hoop.

Regards Mark

Welded or bolted onto the chassis?

Pat...

My MSA book says

50x2 or 45x2.5 - or if you can prove its strength with certification , u can make it out of anything you want .

your head(top of helmet) needs to be 5cm from the roll bar and 20 cm min from the inside of the upright.

buying a roll hoop which is certified will be easy , turning up without an rac msa log book on the day , is upto the scrutineers to pass it .

I've got a 2000 MSA book and I think that I interpret it correctly where it says 1 diagonal stay would have to be of the asme diameter but 2 stays could be of reduced diameter.

You'r pretty much right in what you're saying. Especially the bit about the structure of the car. So your line has to start from the front of the chassis - not the top of the nosecone.

Perversely, I have done sprints and hillclimbs in the GTM without any rollbar or hoop of any sort. I did kept the hard top on, but that was only because it handled better like that. As Volvorsport has said, ultimately it's up to the scrute on the day. First impressions go a longggggg way.
Next year it'll just be the 145 for me, so I won't be able to go fast enough to roll

Called MSA scrutineer

My bar is fine and 38mm back stays are fine with the same dia for the cross brace.

The only problem being that the bolt on plates would be too big for the chassis mounts. So I will weld directly to the chassis, problem solved.

For MSA, don't you still have to have plates on the cage bar ends even if you are welding?

Pat...

Heh heh that's a funny one Pat!

I read the rule that way when I did the weld-in cage for my rally car, and it looked silly with feet welded to the cage and then to bigger plates on the car.

I checked with the scrutes and it was ok to weld the cage tube directly to the 3mm pad. Obviously the pad still has to be of the min area required. Whether the pad is part of the car or part of the cage is anyones guess, but the scrutes would have to be pretty silly to fail it!

re the tube sizes, as far as I know there is no rule on the combination of different sizes in the cage/bar etc, as long as they are all from the 3 choices given in the book and detailed above (38 x 2.5, 45 x 2.5 or 50 x 2)

These are really heavy anyway and most certified manufacturers use much thinner tube than this, but you or I cannot.