93 replies to this topic

[dstevens]

The construction of a NASCAR car is different from ours. We have a real car, with real strength, with a cage inside it. They have a roll cage, with a car "body" (with zero strength) stuck on the outside. In addition, since their cars are much bigger, it could be several feet to reach the nearest "body" panel. Their rule makes perfect sense in their context, but not in ours.

Not exactly. Tube based cars like a late models and above are much more substantial than a Miata without the body panels. The body panels do very little for impact. I'd bet either my 83 Delta 88, '80 Impala or any of the late '70s Montes I'm working with now are much, much more robust than that Miata tub that me and one of my helpers can move completely stripped. The mini stocks don't have to welded to the cage but the hobby stocks and street/super stocks do and they are based on production cars. I wouldn't build or work on a stock car cage where the seat wasn't tied to the cage. I've looked at do it in my 90 SM but it's tight with me in there. Were I not so tall it would work and now that I'm down to 250 (from 310) it's easier to get in and out. FWIW I raced stocks at about 280. Anyway, I'd strongly recommend that any race car guilder, regardless of make or class in a saloon type vehicle make the seat mounts part of the cage structure.

[KentCarter]

The construction of a NASCAR car is different from ours. We have a real car, with real strength, with a cage inside it. They have a roll cage, with a car "body" (with zero strength) stuck on the outside. In addition, since their cars are much bigger, it could be several feet to reach the nearest "body" panel. Their rule makes perfect sense in their context, but not in ours.

Jim, they require this in nearly every class, including unibody, production-based classes. I agree that the COLA (car of long ago) is different from a Miata, but the rest of the cars are pretty similar.

The question is... how to implement this in a Miata?

[dstevens]

The question is... how to implement this in a Miata?

It's more of a question of driver size/seat placement. Typically the mounts hang down off of the crossbar with extra tubing connecting to a lower door or in cars that have them, a floor bar. Some guys run a bar down along the rocker panel. I have an idea for using 1"x.120 DOM (can get 1" DOM up to .313 wall if needed) using some of the same ideas we just used in the #13 Chevelle. A combination of 1.75x.095 (normal circle track cage material) and 1" x.095 for the seat mounts. Turned out nice. Since this class is so competitive here no pics of the cars, I'll post a model later tonight or tomorrow. The idea for the SM is to use the smallest, thickest DOM you can get for the seat mounts and still fit the driver and tie into the cage in a few places not counting the main bracket/loop. My only concern might be that since it's tied to the cage, some inspector might call for it to be the same size as the cage tubing and that would throw a wrench in the works though perhaps nothing some letters to the CRB couldn't fix.

[Jim Boemler]

The question is... how to implement this in a Miata?

"Good luck!"

[KentCarter]

It's more of a question of driver size/seat placement. Typically the mounts hang down off of the crossbar with extra tubing connecting to a lower door or in cars that have them, a floor bar. Some guys run a bar down along the rocker panel. I have an idea for using 1"x.120 DOM (can get 1" DOM up to .313 wall if needed) using some of the same ideas we just used in the #13 Chevelle. A combination of 1.75x.095 (normal circle track cage material) and 1" x.095 for the seat mounts. Turned out nice. Since this class is so competitive here no pics of the cars, I'll post a model later tonight or tomorrow. The idea for the SM is to use the smallest, thickest DOM you can get for the seat mounts and still fit the driver and tie into the cage in a few places not counting the main bracket/loop. My only concern might be that since it's tied to the cage, some inspector might call for it to be the same size as the cage tubing and that would throw a wrench in the works though perhaps nothing some letters to the CRB couldn't fix.

Great input. I think the GCR is crystal clear that non-required elements of the cage can be whatever size we want. In addition, we would be allowed to tie the seat mounting tubes to the tunnel structure, if we so desired. It would be perfectly legal to run a brace from the door sill to the tunnel or even to run one from the pinch weld underneath to the the tunnel or even the pinch weld on the other side.

[Jim Boemler]

You keep talking about "would be", Kent -- are you suggesting that all these extra connections from cage to various places, and other places to other places, are NOW legal?

[KentCarter]

You keep talking about "would be", Kent -- are you suggesting that all these extra connections from cage to various places, and other places to other places, are NOW legal?

Yes, it is written in the GCR.
9.3.41. SEATS:
"....Mounting structures for racing seats may attach to the floor, cage and or
center tunnel. Seat mounting points forward of the main hoop, between
the center line of the car and the driver’s side door bar and rearward of
the front edge of the seat bottom are not considered cage attachment
points in classes with limitations on the number of attachments."

[Jim Boemler]

Thanks Kent -- I've obviously been away from my GCR for too long.

[KentCarter]

It's fairly new and in response to concerns that seat mountings in cars like ours depend too much on rather thin sheet metal rather than robust structures like the cage. As I lamented earlier, the question is how to implement. With the latitude of this rule, we could even consider adding structure on the bottom-side of the pan in order to get us as low as we need to be for helmet clearance. I can envision two to four tubes that penetrate the pan attaching to the lower door bar and to a plate welded to the exterior of the tunnel. The seat could then be mounted flush to the floor pan but still to robust structures.

[dstevens]

There you go. 9.3.41. I poked around mocking up last night (actually early this morning 2am...) and I think some of the smaller guys can make it with 1.5x.095. My problem now is I sold my 20* Kirky to the 00 earlier to get a containment seat. So I have no seat at the moment to test. There is a used LaJoie in town that supposedly Steve Park ran but even when I get to 220 (the goal) no way in hale I'll fit and the halo looked a bit too wide for the chick car. He wants 500 but I think he'll settle for 300.

When I get a chance I'll put the 9.3.41 specs in Bendtech and see what I can come up with. In my case and other taller drivers it's going to need to be as closr to the floor as possible so we make our torso to hoop/roof clearance. Even though with a top it doesn't call out the 2" rule you'll need to have your head under the hoop as the fiberglass top isn't going to do much. I'm thinking 1/8" flat stock under the seat, also tied to the floor and a frame of 1.5x.095 and 1x.120 DOM with large 3/16" plate on the trans tunnel for mount points.

[KentCarter]

Mr Stevens, what are your thoughts on placing the seat framing on the underside of the floor pan? We are not allowed to move the pan, but we can penetrate it.

[Keith Novak]

The first thing I'd think is it would be a tight fit the way the SD exhaust routes.

[dstevens]

I'd be concerned with the tub flex and floor pan deformity compromising the seat mount attachements to the frame during a hard shunt. After thinking about it some more, I don't know that I'd attach my flat stock to the floor either. Someone like Alan Blaine would be much more informed for such a question. If you get a chance, check out http://blainefab.com/ . He does some great work and he's a regular contributor in the corner-carvers forum.

[fishguyaz]

my 99 car has the ultrsheild SM seat in it. the one with the rib supports that is lacking in many areas IMO
I read this thread, and then went shopping online to make some decisions on which direction to go for the seat.
I dont like the idea of replacing a perfectly good composite seat every five years, so i think i want to stick with aluminum.
I picked the ultrashield VS halo to go with. I then re-read this thread again and was pleased to see several others had made the same choice.

that said, in my 99, with a standard miatacage installed are the any fitment issues with this choice of seat?
http://www.racedaysa...-halo-seat.html

i see it is offered with the left halo shorter for ease of entry/exit.
to find the size of my current seat, exactly where is the measurment taken from to determine seat size. i.e at the top rail near my waist, or at the base, or at its widest point in the hip area?

thanks,
Josh