Garen

Hi all,

What do you think of the two options on this diagram for mounting seats & 6 point harnesses in a 1987 930? I am unsure of mounting the eye bolt in a horizontal abgle, but if you use the factory lower belt anchor, you are doing exactly that anyway. I would end up duplicating the harness mount to the outboard side as well, giving me more control over the lap belt angle in relation to my seat location. I just didn't draw the other side to keep the diagram simple. Any opinions, pros, cons, etc?

Much appreciated...

-Garen (87 930 CS)

Flying Finn

I'm not sure if I understand your sketch fully (are you mounting lap belts?). I assume the option B has the belts going to the same direction as in option A, in which case option B is not good. That "L" will bend in an chrash. Option A looks better.

Garen

Thanks. What if the eyebolt was mounted so that it faces the seat in option B? Do you think tht would work better?

fatbillybob

Double shear your seatbelt mounting points. You can either make them or buy them from someone like stockcar products. This will allow bolt in or snap in harness and reduce twisting on the eye bolt that can result in extra belt movement in a crash.

Garen

More like this?

smlporsche

^^^^
That certainly looks better. Just make sure the bolts are at least grade 6 or better.

Nice drawings BTW !

chrisp

Is your seat so narrow that it can drop inside the rails like that? It must be 13" at the hips. The only first hand experience I have is with Sparco EVO2, COBRA GT and COBRA Monaco seats. All have been wider than the rails.

RedlineMan

Hmmmm....

Someone got good grades in their technical drawing classes!

Option B is a dud. Not with an eye bolt, mate. A standard flat end plate and a shoulder bolt would be decent, even better if the bracket is chunky material. You're on a much better track in Post #5. MUCH stronger, but as Stacy said, you'll be lucky to have that much room.


Check the recent "Sean's Cage" thread for how I did one recently.

https://rennlist.com/forums/showthread.php?t=336902

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Reporting Live from Brockville, Ont. CA.

fatbillybob

If you go like post 5 make sure you delete the eyebolt for proper hardware like an AN bolt with a grip length the same as the width of the double shear. You do not what threads of a bolt in shear. Look at the Aircraft Sruce and Specialty website's hardware. You can also get them predrilled so you can run safety wire through them. This is very cheap yet reliable quality hardware.

SeaCay

Excellent points all (IOW, you beat me to it).

Garen

Thanks for all the input, as well as the compliments on the sketches. I am in the process of rethinking the mounts. It's no small task, to keep everything relatively bolt-in, and safe at the same time. I'll post a new sketch or two as soon as they're complete.

I'm also looking up the suggested websites. I'm using Sparco harnesses, which have sewn-in clip&eyebolt attachments on the lap belts, thus my need to use the eye bolts. I think I might have to exchange the lap belts for bolt-in ones, if I were to use the double shear vertical bracket design.

Looking forward to your future comments and suggestions...

-Garen (87 930 CS)

Garen

After some measurement and re-thinking, here's what I've come up with.

The distnce between the two vertical harness brackets is set at 0.5", since the eyebolt inner hole has a DIA of 0.5". I figured that the clip-in style lap belts are designed to have that amount of play. The bolts that I am planning to use are AN6 -13, with a grip (shoulder?) length of 13/16. The bolt diameter is 3/8", selected to match the taurus DIA of 3/8" on the Sparco eyebolt. There is room on both sides for all of this, and I'm in the process of making a mock-up to be sure. The lap belts would use these mounts on both sides of the seat. The tunnel side bracket would be different, to allow for a second hole, for attaching the factory 3 point latch using OEM hardware.

Comments? Thanks in advance

-Garen (87 930 CS)

chrisp

Sorry I didn't think of this earlier. The only concern I would have is that you're, in effect, mounting the belts to the seats. I think that's prohibited in some sanctioning bodies.

Also, why not use bolt in hardware for the harness...since that's what you're doing?

chrisp

Also, you've got beefy lap belt mounts and hardware but then you run two lap belts and the seat itself through the factory rail mounting hardware. I believe those are M6's. Not even up to snuff for mounting a race seat let alone mounting harnesses and a seat.

Put three M8's on either side and you'll be in business. You could even run one M10 on each near the lap belt mounting point since that bolt sees the majority of the load.

I wish I could draw like you.

Garen

I guess you can say that the harnesses are mounted to the seat OR, the seats are mounted to the frame that shares the loads with the harnesses

DE only, but that shouldn't matter to safety. I'm trying to keep things as close to being bolt-on as possible. I would be curious if this works for PCA DE with the new rules.

I will be looking into exchanging the lap belts for bolt-in styles, since these buckles are sewn in, and thus non-removable. Do you think using the shoulder bolts would be wrong with my lap belts? In effect, all I have done is straighten the eyebolt. If I do exchange the lap belts, the distance "A" in the diagram will be reduced for less play.

-edit-

thanks for the compliment! Good point, I will upgrade the factory bolts...