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Rollcage back stays 
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Post Rollcage back stays
Hello everyone
I have just taken delivery of the parts to biuld my rollcage from Hambly Sportscars. The MSA have updated the rules on backstays (a problem area for Coupes) as below:
1.3.3. Backstays.
These are compulsory and must be attached near the roofline and near the top outer bends
of the main rollbar on both sides of the car. They must make an angle of at least 30° with the vertical, must run rearwards and be straight and as close as possible to the interior side panels of the bodyshell. Their materials specification, diameter and thickness must be as defined in 1.4.1. Forward facing stays are permitted if
an angle of 30° cannot be achieved with Backstays, providing they do not unduly impede Driver and
Co-Driver access to the vehicle. Their mountings must be reinforced by plates. Each backstay should be secured by bolts having a cumulative section area at least two thirds of that recommended for each rollbar leg mounting in 1.3.2
above, and with identical reinforcement plates of a least 60cm2 area (see drawing K19).
A single bolt in double shear is permitted, providing it is
of adequate section and strength (see drawing K20) and provided that a bush is welded into the backstay.
The mounting feet may alternatively be welded direct to the reinforcement plate.


The thing that I think will be hard to achieve is this what they talk about diagonals:

The lower end of the diagonal must join the main rollbar or back-stay not further than 100mm from
the mounting foot. The upper end must join the main rollbar not further than 100mm from the junction of the
backstay joint, or the backstay not more than 100mm from its junction with the main rollbar


I have decided to use pivots at either end of the backstays to make it easier to get them in and out. The problem is getting them high enough up the main bar to be 100mm from the diagonal and still maintaining the 30 degrees.

Anybody looked at backstays and have any clever ideas? Any help/thoughts would be appreciated.

Cheers
Simon


Tue Jul 25, 2017 10:50 am
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Joined: Fri Sep 14, 2007 10:34 pm
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Post Re: Rollcage back stays
Do not get too stuck in with the fine details of the MSA book. My thoughts.

Its a general guide I have seen cars with cages that do not conform to the MSA blue book to the letter, and even reading the blue book can give you different answers.

The best advice is to digest the blue book. Then check the rules of your race series and see how they refer to the blue book. Then best go and talk to a scrutineer/organisers. As I say I have seen cars that do not seem to comply at first, but if you read the sections differently they do.

The blue book covers all racing series and not all sections are relevant. A rally car cage is very different to formula ford. Neither complies too all sections of the blue book, but if you separate the rules out then you can see how they do.

Neil

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Tue Jul 25, 2017 9:26 pm
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Part built GTM

Joined: Fri Aug 15, 2014 4:49 pm
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Post Re: Rollcage back stays
The cage from PPC comes with a front diagonal which goes from the main hoop to the passenger footwell, I'm not sure if this would be acceptable?


grizzler73 wrote:
1.4.1. Forward facing stays are permitted if
an angle of 30° cannot be achieved with Backstays, providing they do not unduly impede Driver and
Co-Driver access to the vehicle. Their mountings must be reinforced by plates. Each backstay should be secured by bolts having a cumulative section area at least two thirds of that recommended for each rollbar leg mounting in 1.3.2
above, and with identical reinforcement plates of a least 60cm2 area (see drawing K19).
A single bolt in double shear is permitted, providing it is
of adequate section and strength (see drawing K20) and provided that a bush is welded into the backstay.
The mounting feet may alternatively be welded direct to the reinforcement plate.[/i]


Tue Jul 25, 2017 9:29 pm
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Looking like a GTM

Joined: Wed Sep 30, 2015 8:25 pm
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Post Re: Rollcage back stays
The regs say I need a rollbar and no matter which one I put in it will need back stays, I want a 6 point cage because it is safer and it is my neck it is saving if anything goes wrong. I thought about the diagonal but don't want one in the cabin with me. I have looked at the Lotus Europa for example and that does not comply with the MSA rules but because of the original chassis layout it can't. I see no reason mine wouldn't be ok. I was just interested to see what others had done.


Tue Jul 25, 2017 11:25 pm
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Joined: Fri Sep 28, 2007 7:39 pm
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Post Re: Rollcage back stays
My back stays go thru the bodywork to the rear subframe mounts, down the flying butresses.

Not at home, so on phone, but sure I have pics on here somewhere.

Found one

Image

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Thu Jul 27, 2017 3:56 am
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Looking like a GTM

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Post Re: Rollcage back stays
Thanks Ken
Does yours have a kink in it? the Bluebook says no kinks which means I have to run further down the main bar to get 30 degrees, then I could fall foul of the 100mm from the diagonal rule... Ahhhh!
In the meantime I have contacted the Championship chairman to ask if they can point me towards a MSA technical officer who can give me some advice.


Thu Jul 27, 2017 12:26 pm
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Post Re: Rollcage back stays
There is a pinned joint just at window level.

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Thu Jul 27, 2017 5:40 pm
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