7 replies to this topic

[Tom Hampton]

I Drove down to Ultrashield yesterday, and picked up a VS Road Race Halo seat, 16"/20* (nice folks, btw). I test fit the seat in the car today, which resulted in a little hammering to the trans-tunnel.

Looking in the GCR 9.4.B.1 (a-c) helmet clearance is only specified for open cockpit cars. Paragraph (a) only states that the main hoop must be as close as possible to the roof and B pillars. Paragraphs (B ) and (c ) start with "On Open cars..", and therefore would seem not to apply to SM (with hard top). Nevertheless, I'm assuming the the 2" is a recommended clearance for safety reasons...even if not strictly required by the GCR.

I'm 5' 11", and mounting the seat to the stock humps leaves me about 2" to the roof from the top of my helmet. Given that the cage won't actually touch the roof, that means that there will be less than 2" to the top of the roll-cage.

So, is this enough clearance, or should I remove the humps and mount closer to the floor?

I've been perusing the old archives on seat mounting options. I think I'm good with the various methods, but...how much total layback is typical? Or more directly, how much do people typically elevate the front of a 20* seat (assuming a compomise isn't being made for freakishly tall folks )?

Given a choice: is more layback or less preferred (for safety in a crash)?

Maybe I should remove the rear humps, which would give me a little more layback, and clearance?

[Greg Kimble]

Tom,

You are right the 2" applies to open cockpit cars. You want to sit as low as possible in the car, so I would agree that removing the humps to lower your seat is a good idea. Seat mounting angle is going to be dependent on making you comforatble in the car. I know that taller drivers (I am 6'3") tend to recline the seat more to get some additional head room. You may also want to refer to the installation instructions for the harness that you are going to use to make sure that the recommended angles are met when the seat and harness are installed.

Greg

[Tom Hampton]

Thanks, Greg. I'm waiting on the arrival of the Harness. Bought a Crow 6-pt. Also going with the Dave Wheeler cage. Dave's cage has a separately mounted harness bar...which is custom mounted. Crow recommends 0-10* down, but I'm using a defnder...which recommends 0-20* up. Anyway, point being that I will weld the harness bar at just the right height once the seat height and angles "just so".

[dstevens]

I'm just getting ready to cut my seat mounts out. It's going to be a tight squeeze for me and I want to fit 3 door bars on my side. I'm using a 20* Kirkey.

[NV Racer]

Luckily for most of the tall drivers like me there is no minimum clearance with hardtop in place. Myself I have less than 1" with helmet on and seat as low as possible.

Dennis

[Keith Novak]

Luckily for most of the tall drivers like me there is no minimum clearance with hardtop in place. Myself I have less than 1" with helmet on and seat as low as possible.

Dennis

I'm about 5'11" also and have a 16" 20* Ultrashield seat. When we installed my seat with the cage and sat in the car with the rear humps removed, the angle wasn't very good. With the extra recline, I had more clearance to the hard top but less to the main hoop which I think I'd like to avoid smacking into my helmet even more. The rear humps were welded back on and a piece of 3/16" flat bar made the some rails to attach the seat. There's clearance for my head from the top, the main hoop is comfortably away, and there is a bit of room between my butt, and the floor.

Getting good clearance for your helmet is important, but if I can avoid it, I don't want to sit on the floor either. From a safety pespective, I think it's good to also consider the force of hard impacts going through the floor and into me from the ass up. Unlike in little formula cars where you essentially lay on the floor, with production based cars your spine is alot more upright so I think spinal compressions should be a safety consideration in cockpit layout. If you need a gurney bubble in your hardtop just for head clearance though, your choices are limited.

[Tom Hampton]

I'm about 5'11" also and have a 16" 20* Ultrashield seat. When we installed my seat with the cage and sat in the car with the rear humps removed, the angle wasn't very good. With the extra recline, I had more clearance to the hard top but less to the main hoop which I think I'd like to avoid smacking into my helmet even more. The rear humps were welded back on and a piece of 3/16" flat bar made the some rails to attach the seat. There's clearance for my head from the top, the main hoop is comfortably away, and there is a bit of room between my butt, and the floor.

Getting good clearance for your helmet is important, but if I can avoid it, I don't want to sit on the floor either. From a safety pespective, I think it's good to also consider the force of hard impacts going through the floor and into me from the ass up. Unlike in little formula cars where you essentially lay on the floor, with production based cars your spine is alot more upright so I think spinal compressions should be a safety consideration in cockpit layout. If you need a gurney bubble in your hardtop just for head clearance though, your choices are limited.

Thanks, kieth. that's what I was getting at. Wasn't sure where the balance between helmet clearance and butt clearance was. Sounds like your opinion is "equal". Iow, 1" top and bottom is better that 2" on top...if you have to sit on the floor.

[Keith Novak]

I don't know that there's a magic number but I definately think it's safer having some room above and below as opposed to all above and none below. The most common scenarios involve high forces entering your body from the butt up so I wouldn't put all my eggs in one basket and ONLY worry about the dreaded roll-over.