high backed seats and seatbelts

[oaktree11]

Hi all,
This is probably a stupid question but I am probably going to fit MX5 seats. They come in various guises and some are high backed with no seatbelt holes like these:
http://www.ebay.co.uk/itm/MAZDA-MX5-...item256d765d74

Question, can 3 or 4 point mounting full harness belts be used with these and if so, how?

Thanks, John

[timbo]

The IVA manual says:

Note 9: The seat belt must be capable of effectively restraining the occupant
ƒ in the case of a harness belt or three point belt, by being positioned across the shoulder so that it does not slip off the shoulder of the
occupant.
Note 10: Where the seat is adjustable, this check must be carried out with the seat secured in the rearmost position and with the back rest in the normal driving position, in any case at a rearward angle of not more than approximately 25˚ from the vertical.
Note 11: The effective belt anchorage is the actual anchorage point to the vehicle unless a change of direction of the belt to the wearer is produced by a fixed intermediate device, for example, a belt guide fitted to the upper part of a seat back.
Note 12: Where a seat incorporates a belt guide that creates the “effective belt anchorage” consideration must be given to the strength of the seat back in relation to the loading to which it may be subject, (this being dependent on the position of the actual anchorage). The requirements Section 19 RS 3 should be applied to the effective anchorage location

I found this solution worked:
http://www.flickr.com/photos/3310545...in/photostream
My IVA inspector didn't see the need for an anchorage bar, unlike others experiences.
Tim

[oaktree11]

Tim, Thanks for the comprehensive reply.
So, If I want to use a high back seat with no slots I have to have a "fixed intermediate device" which has to be strong enough. I am surmising that this would be devices for the belt to pass through on each side of the seat at shoulder height or above?
This sounds like trouble in the making so I think a seat with a removeable headrest (with or without a bar) or seats with pukka slots is the way to go?
John

[MartinClan]

The earlier MX5 seats (as I used) have removable headrests - which may prove more suitable.

Robin

[oaktree11]

Thanks Robin, I really fancied the speakers in the headrest which I dont think are available in the removeable ones but I do like the seats with the removeable headrests so that is the way I will go. The MX5 seats look like a good buy.

[morris]

You beat me to it, I was going to ask this very same question as I fancy the MX5 ones to though the traditional style ones like these (though leather)

http://www.ebay.co.uk/itm/Mazda-MX5-...item1c247f4417

I would actually prefer a normal everyday over one shoulder and lap belt to a racing harness though I'm not sure how I'd mount the top runner without it cutting across the neck

[peterux]

The Marlin Facebook page pictures shows their latest car with diagonal inertia reel seat belts and seats without seatbelt slots.


Marlin built Sportster by marlinpeter, on Flickr


Marlin built Sportster by marlinpeter, on Flickr

You can download the pictures from their Facebook page so I have put a couple on my Flickr to disply here.

I think Ian's chassis is designed for these but I'm guessing John will need to get some brackets welded if you want to go that route. (And I think the IVA has some specific rules about seat belt mounting points.)

Hope that helps?

Add: Just looked again at Ian's pictures and it doesn't look like he has the seatbelt top mounting points either.

[morris]

No, that's the problem. I have the lower threaded holes either side of each seat I guess for the main end mount point on the belt depending on which way you want to fasten it. The cross bar on my roll over bar is plain with no obvious mount point for the runner.

It's not clear from the Marlin pics how they are fixed on.

Terry told me the other day that they had total kit car magazine down this week so hopefully some more photos of the demo car will be available in the press soon for scrutiny

[denniswpearce]

My seats are the same cobra type with the slots and can be seen in the accompanying pic :-
http://www.flickr.com/photos/5897937...in/photostream

[Chris Cussen]

I used Cobra 7 seats and they got through IVA, but only just as the height of the harness slots was very close to the limit...