Cage questions

[woodc]

A couple more quick cage questions:

The GCR states "a maximum of two gussets per rollcage joint are allowed". What is the definition of a rollcage joint? If 3 tubes come together in one spot how many joints is that?

The GCR states in 9.4.2 J "In order to provide a secure seat back support a section of tubing equal to the rollbar shall be installed horizontally from the main hood upright to the diagonal brace. This tube shall be no higher than shoulder height."

In cages such as the miatacage dot com that only have one horizontal bar what is the optimal/legal height to install it so it can satisfy the seat back support *and* harness bar rules? The bar needs to be below shoulder height for the seat but how far below...since lower = more chance of compression injuries I don't want a cage that a taller person than me cannot be safe in either....

Also...if you run an FIA seat and thus do not use the cage for any seat bracing does this rule even apply?

[Greg Amy]

First, before you even THINK of cutting a tube, you should spend some time with a local tech inspector to ENSURE your ideas are copacetic. Nothing sucks more for me as a tech inspector to have to send someone home from their first driver's school because of a misunderstanding of the rules.

Second, if you're having someone else do the cage, ensure THEY have experience with the rulers. If not, have THEM spend some time with an inspector.

Third, make sure to get your car's initial logbook done in ADVANCE of your first event. This way you'll have time to fix things.

Fourth, opinions on the Internet - including mine - are wholly irrelevant when you're staring down someone who's about to send you home from your first event.

That said...

The GCR states "a maximum of two gussets per rollcage joint are allowed". What is the definition of a rollcage joint?

Any place two tubes come together. The purpose of this rule is to ensure you don't misuse the rules to an unapproved use, such as wild-assed stiffening. The cage's intent is for safety; how far you go towards performance is arguable among reasonable people (I personally push it to the max).

If 3 tubes come together in one spot how many joints is that?

Depends on HOW they come together, but generally that two joints.

...what is the optimal/legal height to install [a horizontal brace] so it can satisfy the seat back support *and* harness bar rules?

That's your decision to make, as long as it meets those limits. Typically, people will do it somewhere between mid-back and shoulder heights.

...if you run an FIA seat and thus do not use the cage for any seat bracing does this rule even apply?

Yes. That rule originally came about in the 80's when Showroom Stock cars ran stock seats; its purpose was to keep the driver's head away from the rollcage if the seatback mechanisms broke. Later, it was added all the way across to the passenger side to support the planar integrity of the main hoop, to keep the diagonal from displacing from that plane during a vertical load. As such, it is required regardless of your seat design.

GA

[woodc]

Thanks for the input...it is appreciated!

This will be my third logbook/race car but the first cage that was not either already mostly done (converted an ITA MR2 to an FP car) or a bolt in affair thus the first one I have any input on.

Steve Eckrich (spelling?) is the local tech inspector and is a pleasure to work with. He was a godsend when I was working on the FP car...but I try to consider him a "magic bullet" that I don't use unless all else fails...he is a busy man

I will get the logbook and run several time trials to shake the car down before heading to school. Going to school with a flaky car you have no faith/seat time in just plain sucks...been there done that ...

[jimmyc]

the harness bar has to be within a vertical 10 to 15 degree space of your shoulders.

This is dectated by the rules/direction/proper way to mount your harness.

[woodc]

So the bar must be between even with your shoulders and 10-15 degrees below to satisfy both rules. Since I am not very tall I should shoot for almost dead even with my shoulders...that way taller drivers could still be legal in it...

Got it!

Thanks