anti-sub straps

[fve]

I have gone through postings on rennlist, here on teh RTR forum, the instructions for harness mounting from the Schroth web site and even the rules from PCA club racing. and, perhaps i am dumb, but i am still not sure about the recommended mode of securing the anti-sub straps.

situation. 996 gt3, had it for a year now, new to DE (did a little last year). Want to do more this year. Goal for the winter for focus on safety equipment. Obtained gt3 seats, DAS sport roll bar. I am also getting some used schroth profi III harnesses.

first, i know, i know, used harnesses are not ideal. the giver is going to new harnesses that work better with the HANS and they are a good starting point. I may opt to also go for a HANS in the future (i am sure that broken cervical vertebrae are no fun) so this will allow me a place to start before i buy my own (new) harnesses.

The big question is about securing the anti-sub straps. All the stuff that i have read (listed above) indicates (to paraphrase): install according to manufacture recommendations. Ok. i understand the 0-20 degree angle, the separation of the straps. the seats come with (i think OEM) a subbar. Is if ok to secure the anti-sub straps to the sub-bar or do i need to drill/weld backing plate, eye-bolt, etc to the sheet metal.

I would love to ask in person, but i worked last night during the meeting and i have to work (again) on Saturday.

cheers, and thanks in advance.

fve (frank)

[JeffConklin]

Frank,

Best bet is to shoot  an e-mail to Paul Walsack - Track Safety Chair. ( safety@rtr-pca.org ). That way you'll know that what you choose to do will pass tech inspection. 

Jeff

[smankow]

Frank, we're having an "unofficial" tech session tomorrow (2/28/09) at Dougherty Automotive in West Chester.  I know that Paul is planning on being there around 9 or so.

[KennyB]

I think the Schroth website has the (approx) 60 PAGE pdf file for install instructions, showing the sub straps wrapped (in a specified fashion) around the subbar.  However, a previous Der Gasser article by a well-respected tuner suggestes bolting through the floor IIRC.

Probably either way will do.  I will ask Wally on Sat for you.

[fve]

Thanks all. I did send an email to paul today, still waiting to hear back.

Yes I am aware of the tech session. However...i work from 7 am until god knows what hour. That is the glamourous life that i lead to be able afford all this good fun.

If someone could ask for me or ask Paul to email me, that would be great. I would like to do it once and do it right. And...if the answer is floor, then what the heck purpose does the sub-bar have save for be being dead weight?

thanks, fve

[fve]

KennyB wrote:

I think the Schroth website has the (approx) 60 PAGE pdf file for install instructions, showing the sub straps wrapped (in a specified fashion) around the subbar. However, a previous Der Gasser article by a well-respected tuner suggestes bolting through the floor IIRC.

Probably either way will do. I will ask Wally on Sat for you.

Yes, I see that in the Schroth document (have in on the computer, and read through it several times). How much superior is the floor mounting, or is it just busy work that does not increase safety significantly.

I would appreciate, greatly, clarification. Again, i want to do this correctly but...not something that is going to mangle the car quite yet to no real purpose.

tahnks

[bobt993]

Great to hear your installing a harness system.  I am not comfortable instructing in a high HP car without them.  Used harnesses are fine, but make sure the manufacturing date complies with the current guidelines.  Old harnesses need to be re-webbed if they are to long gone (4 to 5 years is typical).  Just check the rules.  As far as the sub strap, get the most proper fitment you can.  A sub belt that is forward of vertical really  does little to protect you in case of a big accident.    I have experienced hitting walls while racing and as a DE passenger, so I am unfortunately experienced on this one.  Adding the proper mounts under the seat we do little to mess up the car aesthetically.  Check on the Brey Krause website for possible options that may make this even easier.   There are several RTR DE instructors that own GT3's and can also help with your options.  One person to contact is Larry Herman as he ran a GT3 for a season or two.

Good Luck

[Terry]

I think there are two schools of thought, neither supported by data, so take your pick. The old, tried and true racer approach is for the harnesses to be anchored to the car, not the seat, necessitating eyebolts through the floor for the lap belts and the sub belt. The other approach is to trust Porsche and the USDoT that the seats are anchored with sufficient strength to hold the harnesses. Standard three point belts, which are crash tested, mount to the seats. The question is whether the higher forces which are possible in a racetrack wreck could cause the seat or rails to fail. Personally, I doubt it but it's a personal decision. All of the Brey Krause stuff for these seats attaches to the seats, not the floor.

[fve]

Terry wrote:

I think there are two schools of thought, neither supported by data, so take your pick. The old, tried and true racer approach is for the harnesses to be anchored to the car, not the seat, necessitating eyebolts through the floor for the lap belts and the sub belt. The other approach is to trust Porsche and the USDoT that the seats are anchored with sufficient strength to hold the harnesses. Standard three point belts, which are crash tested, mount to the seats. The question is whether the higher forces which are possible in a racetrack wreck could cause the seat or rails to fail. Personally, I doubt it but it's a personal decision. All of the Brey Krause stuff for these seats attaches to the seats, not the floor.

About the B-K stuff, that is a very good point. the lap belts are supposed to attach to the seat (based on the porsche material, mounting points available from BK and others). In a frontal crash (or rollover) arent the lap and shoulder belts supposed to absorb the majority of force and the ant-sub belts are primarily there to keep you in place and make sure the other belts do their job? thus, why is it so important to mount the sub-belts to the floor when the lap belts are mounted to the seat. inquiring minds would like to know.

I know that BK (and others) also offer a mounting point for the door-side that attaches to the OEM seat belt attachment point instead of the of the seat. Is this superior to the seat. Or is it worse since one side is to the chassis (door side) and one side is mounted to the seat (tunnel side). I imagine that it could create some interesting torque forces on the seat and driver in a crash.

And that gets into seat-back braces. I have brackets already welded to the bar (based on design, would guess BK). Wouldnt that be more import than floor mounting the sub-straps.

Please understand, i am not trying to be argumentative. I love playing Devil's advocate. I would like to understand what the region requirements are and what is a safe set-up without getting into unneeded modifications that do not have any real-world benefits.

[bobt993]

The seat back brace is important in the case of a rear impact.  eg, car spins at high speed backs into a solid barrier.  The seat can slide or break lose sending the driver under the roll bar or cage folding you in half (seat sandwich).  The seat guides the harness and shelters the driver, but does not restrict your movement by staying completely in the seat.  The harnesses are designed to give with elasticity reducing the initial gforce (somewhere around 30%).  My data logger showed how intense this delta can be after reviewing a crash at the Glen.  The pulse exceeded my DAS logging scale (off the charts) and the car was still driveable.  A car spun in front of me sending me off the track to avoid him, coming back on my car had no more traction (rain race).  I hit the inside wall with both feet in still going between 70 and 80mph.   I was not hurt by the impact, just pissed off by a sloppy racer trusting PSM to save him. 

Harness roll bar or full cage with a seat back brace is an important component.  Treat the harness system the same.  The sub belt does hold the movement of the other straps, but must also reduce the risk of sliding under the lap belt.  Seems improbable, but actually can happen very easily.    BTW,  Terry has a lot of knowledge on the GT3 and can offer some options on belt locations.