Mounting seat & harness off same point?

[Damo]

I'm currently mounting seats & harnesses into my car at the moment, and have struck a slight hitch - In road form, the car had the inner seatbelt bit mounted off the seat itself, meaning that there is only one threaded hole available on the trans tunnel to mount the seat and harness to.

So, rather than drilling new holes and making a new mounting point, I'm planning on using the single factory hole and will bolt the seat mount down using the 'eye' bolt that the harness then clips into. Two quick questions -

1) The factory mounting point should be strong enough to cope with the forces generated by both the seat & harness in an accident......shouldnt it?

2) Does anyone know if the standard harness eye-bolts (as found at Revolution ect) are an appropriate grade to be mounting a seat with?

Ta
Damo

[Bogan]

From the CAMS Manual (Schedule I-3):

On series production cars, some or all of the original seat belt mounting points may be satisfactory. Where the original seat belts are affixed to the seat, such mounting points may be used only:
(i) where the original unmodified mounting points on the seat are retained; and
(ii) the vehicle is being used for non-FIA International events.
Where the original mounting points are not used, additional floor mounting points must be reinforced with a 3mm steel plate of at least 75mm x 50mm on the underside of the body.
(b) Full harness (Type A and B) rear mounting points must be to a substantial part of the vehicle’s structure, reinforced as for floor mounts above, or to the safety cage.
(c) Under no circumstances may a safety harness mounting bolt be used to affix a safety cage to the bodyshell.

So you can't mount a cage with a harness bolt but it doesn't say anything about a seat.

FWIW the Lancer has the seat mounted in the factory mount points and the outside lap strap eye bolts are mounted in the factory lower seat belt mounts. From what I can remember the buckle is mounted to the top of the transmission tunnel so the inside lap bolts are through the side of the tunnel with the plates mentioned above.

Is there enough length to get the adjusters so that they won't be fouled by something mounting the harness that close to (onto) the seat?

[flat04]

I am fairly sure from memory that scrutineers here in SA for state level events have been totally against mounting harnesses and seats using the same bolts.

I would strongly recommend against doing it and if you have a good think about it I'm sure you'll come to the conclusion that it might be better for your own safety to drill and new hole, plate it up strongly and affix your harness to it instead.

Andrew

[Damo]

Thanks Bogan - yep, the factory mounting point is a fair way outside where the seat and sidemounts sit, so the harness adjusters are pretty much clear of everything.

I think it satisfies the above, regs, so it should be OK.

[Damo]

Originally Posted by flat04

I am fairly sure from memory that scrutineers here in SA for state level events have been totally against mounting harnesses and seats using the same bolts.

I would strongly recommend against doing it and if you have a good think about it I'm sure you'll come to the conclusion that it might be better for your own safety to drill and new hole, plate it up strongly and affix your harness to it instead.

Andrew

Ok, thanks Andrew. I was originally going with that line of thinking too, but then thought that - a) the factory point in the floor is obviously strong enough, as its designed to take the load of the seat with the normal seat belt attached to it, and b) the harness mounting bolts would most likely be an approprtiate grade if they are desgined to withstand the forces generated by a harness & body, and the seat is only another 7kg or so.

I didint think it was such a bad idea, but now I'm not so sure.....
Any scrutineers out there that can give me your thoughts?

[Ben Wilson]

I can't see any reason why it's a bad idea, but it just feels wrong.

[Spac]

Damo, your logic is fine - if it worked for the factory, it'll work for you.
One harness mounting bolt is so much stronger than you are....

Remember that if you hit with the front, rear or top, either the seat or the harness will be taking the load - not both at once.
Sideways into something solid is the main exception, but in this case, you've probably got bigger problems AND there's merit in keeping the seat and harness mounting points together (ref: Rodger Freeth).

[zero45]

I have always avoided using seat mounts for harness mounts. As Ben Wilson said -it just does feel wrong, But then again technicaly I can't see a real issue.

If you hit something hard enough to break that mount -I think its going to be the least of your problems.