Race seat mounting

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SteveNZ

Race seat mounting

Post by SteveNZ »

Hi, this is not an engine related question, but I think it may be a good place to ask. :)

I have a Momo Cup fibreglass seat that has side mounts. I have the side mount brackets for them. Apparently, according to this website

http://sportscar-parts.com/spseatbr.htm

these can't be used with sliding rails. Does anyone know why? Is it unsafe for some reason? I have an OMP seat mount and a set of rails that would work great. NZ Motorsport manual does not say anything about side mounted seats and sliding rails specifically. Any help welcome.
Guy Croft
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Post by Guy Croft »

Good true race car seats are always bespoke- sized to the driver and hard bolted right through the floor. This is for safety, because if the seat breaks free in a rollover you're in real trouble. Rails don't give any protection in rollover.
That said if you want to use rails, accepting it's less safe - it is totally your call.

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Julian
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Post by Julian »

I don't know what your motorsport regulations manual states but the one for the UK goes something like this:

You can (for most series) retain your original seats and mountings (on rails) but as soon as you fit an aftermarket seat it has to be

1) FIA approved (which means it cannot include a reclining mechansim and meets their fairly rigorous strength requirements)

2) Has to be solid mounted - the mountings can accomodate adjustments provided that once locked in place it is very firmly and cannot move. This is normally achieved with multiple bolt holes.

It isn't stated in the regulations but the preferred method is weld in reinforced bars across the floor between sills and central tunnel on which to mount the seat. This makes sure that the seat is secured in all accidents (rather than just head on) and cannot easily rip itself out of the floor.
Last edited by Julian on July 23rd, 2006, 3:34 pm, edited 1 time in total.
Cousin Cleotis
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Post by Cousin Cleotis »

In rallying it is prefered to mount the seat to the sills and tunnel because the shock of something hitting the floor would through the seat if it were bolted to it.

You dont say what the car is going to be used for, do you really need adjustment?

Paul
SteveNZ

Post by SteveNZ »

Thanks for the replies. I accept that using sliding rails are less safe than bolting the seat straight to the floor or mounts.

The website states side mount seats can not be used with sliding rails. It directs you to FIA approved mounts that can be used if you want adjustment. However it implies that bottom mount seats can be used with sliding rails and this would be FIA approved.

I assume from that, side mount seats have a specific problem with sliding rails that bottom mount seats do not. Anybody know why?

Given the risks, I would like to use rails if I can. But not if its going to intefer with the safety of the seat itself.
Guy Croft
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Post by Guy Croft »

Steve,
I admit to having fitted the Sparco seats I fitted in my 124CSA using rails. I just did not any better in those days (1984).

What I will say - is that insofar as the seat itself is concerned there are good and bad, you have to look carefully at the seat body/chassis design. Take expert advice before buying or bolting, from a rally/race prep expert who is familiar with the seats you have bought or are contemplating buying. Like helmets - good ones cost more. A good seat can mean 'no broken legs' in situations that - when you're putting the car together - you could never imagine might happen.
Few things worse than being upside down tied into a race car by a 6 pt harness with the seat cavorting around on top of you. Or so I understand.

GC
SteveNZ

Post by SteveNZ »

I have the seat test fitted now. The OMP mount placed the seat way too high and too far forward so I didnt use it. I decided against the sliders too. I was surprised to see how nicely the seat fitted straight on the factory Tipo seat mount (part of the floor) :lol:
Attachments
Momo seat fitted directly to Tipo floor. I made a simple bracket from 3mm plate for more strength.
Momo seat fitted directly to Tipo floor. I made a simple bracket from 3mm plate for more strength.
Seat in mount.jpg (42.2 KiB) Viewed 10034 times
ronan
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Post by ronan »

Hi Steve.
I just recently custom made my own side mount seat brackets for mounting my fibreglass race seats into my car. I used the original mounting bolts/holes where the seat runners used to bolt onto because they are fairly strong. After dummy fitting the seats into the car and then taking measurements (including sitting in them to see if I could still reach the pedals properly) It was just a case of drawing up the mounts and then getting the local metalsmiths to fabricate them. The seats fit like a glove and despite what people say about fixed buckets I have found them to be the most comfortable seats I have ever driven in.
I could get some pictures of them to you if you need inspiration.
Hope this helps.

Ronan.
Julian
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Post by Julian »

ronan wrote:Hi Steve.
I just recently custom made my own side mount seat brackets for mounting my fibreglass race seats into my car. I used the original mounting bolts/holes where the seat runners used to bolt onto because they are fairly strong. After dummy fitting the seats into the car and then taking measurements (including sitting in them to see if I could still reach the pedals properly) It was just a case of drawing up the mounts and then getting the local metalsmiths to fabricate them. The seats fit like a glove and despite what people say about fixed buckets I have found them to be the most comfortable seats I have ever driven in.
I could get some pictures of them to you if you need inspiration.
Hope this helps.
Is this for road use or competition use?

For road use it isn't so much of an issue (but still relevant) but for competition purposes (and forgive me if I am wrong here as I don't have a blue book to hand) the mountings need to be a but more than cobbled together - for serious competiton use this means properly approved. The problem is that not all materials are suitable and even the ones that are suitable you have to make sure the strength and toughness is sufficient.

The big difficulty is that you can take almost any metal (of adequate thickness) and turn it into a mounting plate - it will look and feel strong but without some suitable testing equipment (or modelling software) it is very hard to tell if it will take the punishment in the event of a crash. A common problem is welds - if you look at competition mounting brackets you will find them to be made out of pressed sheet metal and not a weld in sight. You will also find them to be fairly hefty (in terms of thickness) which is why people are willing to pay over the odds for lightweight magnesium alloy mountings to keep weight down.

In a road car the problem is reduced somewhat by the much lower rigidity in the chassis - the odds of experiencing a serious impact where the car doesn't massively deform (and absorb a lot of energy) is very low. Competition cars by comparison have very rigid safety cells in the centre while the extremities tend to be very flimsy due to removal of excess material and the adoption of light weight panels.

Another point to consider (as mentioned above) is that road car seat mountings are designed to hold the seat firmly in place in frontal impacts. An impact to the rear of the car is likely to see the mountings fail (or at least fail to do their job properly). When a rigid seat and mountings are fitted it is important to reinforce the mountings as the problem is excentuated. The usual way of doing this is to run tubing across the car between the sills rather than relying on the floorpan itself to hold the seats securely.
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Post by Guy Croft »

MODEL POST

Well done Julian for contributing such pertinent knowledge to this important and often neglected issue.

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ronan
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Post by ronan »

I will clarify that my install is in a road car. Although I have no intentions of competing it I would like to be able to take it to the track. Also I am confident that the parts I made up are stronger than alloy ones that you can buy.(just to be on the safe side there were some big hammers and a bit of jumping) One point I would like to make is if anyone goes down the route that I followed is to be VERY clear with your instructions for whoever is doing the work as my man forgot that I was actually going to put seats between my mounts and made the support plate too high which I had to remove.

Ronan.
Attachments
Seats go here...
Seats go here...
seats 008 copy.jpg (112.65 KiB) Viewed 9946 times
dido
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Post by dido »

Looks good - I would only suggest avoiding sharp edges as hey could be really dangerous in a crash.
Guy Croft
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Post by Guy Croft »

OK

So far there has been published here a mixture of expert advice and an open & honest display of work done by individuals. That's fine.

However at this juncture I will say that sufficient has been said that those wishing to learn something will have done so by now and further reference on the subject should be via your relevant Motorsport Governing Body or good source books on competition car building.

There is a lesson here.
This site is actually read by some people who are motosport industry leaders in many spheres, one or two are members, some are not. A number of them have written to me today expressing their concerns regarding the way this topic is going.

Although he has NOT written to me I happen to regard, for example, Julian - who has written here, as expert on seat placement, certainly more expert than I - and I have done my fair share of race and rally car prep.
In respect of a thing like seats, or harnesses, or brakes, balancing cranks and so forth - anything potentially life saving/threatening - if an expert says on GCRE.com 'do it this way' and there is then disagreement as to the effectiveness of that method, then the onus is firmly on the reader to demonstrate - by means of properly constituted technical argument why he is correct and the expert is not. And it had better be good.

Do not allow yourself to get upset about this! Lord knows, I myself am more at risk of being taken to task for what I write than anyone else here - which is why I try to be most thorough and well-briefed before I post! But this forum cannot ever become a respected reference archive on proper 'how to' methods unless all members accept that.

Ultimately, anyway, this is a race engine website not a race car prepararation site, although I certainly don't have a problem with the topic being posted in the first place. But I am locking it at this time - and it is not to be re-opened somewhere else without my express permission.


GC
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