Roll cage checks at Snetterton

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Roll cage checks at Snetterton

Postby RichardJ » Wed Nov 04, 2020 10:02 pm

Did anyone else get pulled up for not having a 50mm gap between the straight edge and top of the helmet?

I’ve looked in the Blue Book but can’t find anything about this dimension. Drawing K31 shows there should be 50mm between the bottom of the rear hoop and the top of the helmet, and drawing K60(ii) shows a line from the rear hoop to a front structure and no part of the helmet should be above that line.

I can adjust my seat position so my helmet is below the K60(ii) line but I can’t get a 50mm gap without replacing the rear hoop. Would prefer not to have to spend the time & expense if I can help it, and don’t feel it’s correct that I have to do something which isn’t in the regs.
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Re: Roll cage checks at Snetterton

Postby Dave Robson » Thu Nov 05, 2020 7:51 am

My understanding is as you describe from the Blue Book. I assume that there was a misinterpretation of the requirement for a 50mm clearance. Mind you it would be a good idea to maximise the clearance between your helmet and the straight line from the roll hoop to a front structure.

I'm one of the few who has rolled a 750 car and found that whilst upside down the car was supported by the roll bar and the 'tops' of the front tyres. The tyres turned out to be the 'highest' 'structure' at the front of the car (the chassis was a bit lower at the front). As it turned out this was very handy since I could slow down whilst skidding upside down by applying the brakes to the front wheels! I'm not sure that this benefit will ever be written into the Blue Book.

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Re: Roll cage checks at Snetterton

Postby pbove » Thu Nov 05, 2020 8:14 am

Email Bob Blackmore and ask him. His email is in the Blue Book.
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Re: Roll cage checks at Snetterton

Postby RichardJ » Thu Nov 05, 2020 3:15 pm

Yes I can do that, but I just wondered if anyone else had the same comment?
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Re: Roll cage checks at Snetterton

Postby pbove » Thu Nov 05, 2020 3:49 pm

I was checked twice, once from the highest part of the roll cage to the highest part of the car - the front body over the carb in my case - which is incorrect IMHO, it should be from the front roll hoop to the roll cage which is what they measured on Sunday which I believe to be correct. However, having checked the Blue Book, I too can only find the dimensions that you reference, ie from the helmet to the roll cage.
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Re: Roll cage checks at Snetterton

Postby Dave Robson » Thu Nov 05, 2020 4:36 pm

Taken from page 193 0f the 2018 paper copy of the Blue Book
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Helmet clearance001.jpg
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Re: Roll cage checks at Snetterton

Postby Martin Kemp » Thu Nov 12, 2020 12:11 pm

It is worth checking that your roll hoop and head restraint conform to regulation K 13. Basically, so your head cannot get stuck in the roll hoop.

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Re: Roll cage checks at Snetterton

Postby RichardJ » Thu Nov 12, 2020 6:37 pm

I’ve had a reply from Bob and he confirmed drawing K60ii is correct for us.
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Re: Roll cage checks at Snetterton

Postby max » Mon Nov 16, 2020 5:11 pm

If you slouch down enough then that's exactly how the MS750/01 was designed to be. The green ring is not my halo but intended to represent the 50mm gap for the horizontal helmet clearance check.
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MS750-01 Roll Bar.jpg
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MS750/01
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Re: Roll cage checks at Snetterton

Postby dopdog » Sun Dec 27, 2020 9:34 pm

I have just been reading this post again and I just wondered if anyone has taken into account cars that have roll hoop extensions fitted to give extra height. From my sprinting days there was a lot of discussion about this and the final answer from the MSA was that the extension was never certified and all measurements were taken form the original hoop. They do allow extensions to be fitted but again they are not taken into consideration when measuring for clearence.

I think its worth double checking as we know we are all going to be checked next season that we comply to ROPS regs.
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