New seats - questions...

[GarryM]

Two questions for the engineers/sensible people out there!

I am trying to fit some Sparco seats to my Griff. The only way I can get the seats low enough is to fit them directly to the floor i.e. with neither base frame nor side mount brackets.

Athough the seat is FIA compliant, I don’t need it to be as I’m not racing. I will however have some plates welded to the chassis underneath the seats so that they are securely mounted. The actual fixing will therefore go up through the new welded plates, through the glass fibre floor, through the carpet and into the seat’s captive nuts

Is it sensible to fit the seat directly in this way without the extra support of the mounting frame/brackets?

Also, is it a problem if I am unable to tighten the bolts sufficiently to compress all of those layers together? The floor and carpet is very uneven – I’ll just do it as tightly as possible hopefully without ripping the captive nuts out of the seat or twisting it. I can imagine an engineer being unhappy not being able to snug everything up tightly together. What do you think?

Many thanks in advance!

[griffter]

GarryM said:

Two questions for the engineers/sensible people out there! I am trying to fit some Sparco seats to my Griff. The only way I can get the seats low enough is to fit them directly to the floor i.e. with neither base frame nor side mount brackets. Athough the seat is FIA compliant, I don’t need it to be as I’m not racing. I will however have some plates welded to the chassis underneath the seats so that they are securely mounted. The actual fixing will therefore go up through the new welded plates, through the glass fibre floor, through the carpet and into the seat’s captive nuts Is it sensible to fit the seat directly in this way without the extra support of the mounting frame/brackets? Also, is it a problem if I am unable to tighten the bolts sufficiently to compress all of those layers together? The floor and carpet is very uneven – I’ll just do it as tightly as possible hopefully without ripping the captive nuts out of the seat or twisting it. I can imagine an engineer being unhappy not being able to snug everything up tightly together. What do you think? Many thanks in advance!

Garry, are you saying that the bolts may not do right up such that there may be some exposed bolt thread between the bolt head and the captive nut?

So that if " - " = bolt thread, " B " = bolt head, " N " = captive nut and x = floor/plates/seat, the bolt may look like this?:

Bxx----xN---

If so I would suggest having some spacers made up to ensure there is no exposed bolt thread between " B " and " N ", so that the seat is positively located by the bolts, and that the seat effectively sits on the 'compressed' spacers, rather than by the bolts merely pulling the seat onto the floor as far as you dare tighten them. So if the spacer is " SSSS ":

BxxSSSSxN---

You'd only need mm clearance between the seat and the floor so the seat height shouldn't change appreciably. It would be important to ensure the spacers were short and wide rather than tall and thin though (think 'washer' rather than 'tube') as otherwise the the spacers may 'topple' under lateral load causing the seat to move about.

Please note that this suggestion is based on gut feeling rather than a rigorous engineering analysis! I guess the best advice is to try to get the car to a motorsport outfit for them to fabricate a solution.

[GarryM]

Thanks Griffter - funnily enough I had you in mind when I said engineer!

Yes that is what I meant and your suggestion makes perfect sense. I'll call in to Dulford later today to see what they can do.

[griffter]

I was worried someone else would say it was BollloXxxx