seat belts and safety harnesses

[Jim Rosenthal]

Got a call from Kerry last week inquiring as to what sort of anchors for safety harnesses should they put into my monocoque. This got me thinking...I know very little about this. This car will mainly be driven on the street with occasional track days....I suspect there is a great deal of expertise out there on the Forum and would like to get opinions on what to buy, how to install it, and, most of all, how to make sure that when I DO get to that "occasional track day" that I don't get sent home because the belts don't meet spec. There's a lot of difference between 'street belts' and racing 'seat belts'- anyone care to enlighten me....incidentally I could not find a thread that dealt with this in our FAQs or old posts. I thought I recalled seeing it, but maybe I didn't look hard enough.

 

[Rick Muck- Mark IV]

On P1116, a Safir car, Peter Thorpe has installed a three point street type of belt on the chassis when we got it. We then installed an additional four point (should do a 5 point now) harness for the track. you could wear either one according to the occaision.

Rick /ubbthreads/images/graemlins/smile.gif

 

[Malcolm]

For the lap straps of a 4 point harness these should be in the same position as for a regular lap belt system ie low down behind your butt to the sides of the seat. The threads needed should be the same for either system used.

The differences come when you go up the back of the seat to the top holes. A lap belt system ie 3 point system will need a threaded hole to the side of the shoulder whereas a 4 point harness system needs two holes directly behind the shoulders. Look at the rally seats with the belt holes in the back etc and you can envisage where the belts go.

5 or 6 point systems need bolt holes under the seat but behind where your butt hits the floor as otherwise you will feel the bolt heads.

I hope this is all obvious as it is actully harder to describe than I first thought!

However on a mono chassis the critical thing for me would be spreading the load in an impact situation. You don't want the threaded holes just pulling out of the sheet metal. I don't have expertise in that side of things but would look to see some large spreader plates to share the forces of a crash. a space frame cahssis has lots of steel to thread and bracket too reasonably easily.

I use a 6 point system on road and track. Harnesses are legal in UK for road use as far as I am aware. When on the road I don't bother with the crutch straps and just use it as a 4 point system.

Not sure if this is the help you were after but here it is anyway!

Malcolm

 

[Lee]

I think that the situation in the UK is that for the road, the belts should be E marked.

For racing the usual mark to go for is the FIA marking.

The problem (in the UK) is that to meet FIA spec, it has to have a rotary buckle, which will not meet the E standard, while for the E spec you need a push button buckle which will not meet the FIA spec.

Therefore in the UK, unless you plan on competing in serious events, the E marked belts will meet all the requirements, (but may not be as strong as the FIA belts)

For SVA, I understand they will look for the E marking. For MOT they probably won't.

Regulations eh, don't you just love 'em.

 

[Howard Jones]

Here's the deal, when you buy a new harness set, NEVER buy a used set, they will come with a installation instruction sheet. Install your harness exactly as the manufacture wants them done. As far as mounting points go, I would use either NHRA or SCCA regulations. You can get this information directly from them. Start online at their websites.

All this can be a hassel but do it right anyway and put in a fire system while your at it. You can do a 5lb system for about $300-$400 nowadays. You don't want to be standing on the side of the road watching you car burn to the pavement and be thinking about the $350 you saved!

 

[Chris E]

[ QUOTE ]
For the lap straps of a 4 point harness these should be in the same position as for a regular lap belt system ie low down behind your butt to the sides of the seat. Malcolm

[/ QUOTE ]


Malcolm
Far be it from me to doubt your expertise, but I visited Stockbridge Racing ( the manufacturers of Willans Harnesses) on Wednesday this week, and they advised that it was NOT right to use the normal lap belt mountings ( the ones down to the sides and to the rear of the seat) for 4, 5, or 6 point harnesses.

Their advice, and it is shown in a diagram in their fitting instructions, is that the lap belt mounting should be more or less level with your hips. I sat in my seat, which is mounted as far back as possible, to check this and the new mountings will need to be about 9" forward of the standard fittings.

Anyone else have experience of this ?

 

[ChrisL]

Chris E,

I believe that you are correct. The main difference between a harness and a lap/sash is that, in a collision, the harness would "ride up" (as the shoulder straps pull up) if it were located back of the hip position. Depending on whether you have a 5 or 6 point, you would then either slide under the harness or cause compression of the body/spine which is bad.

There have been lots of studies done on this topic and the advice has been fine tuned regularly over time. I expect that any new harness you buy will have full instructions, but it may still pay to contact the manufacturer for the latest word.

Incidentally, the biggest factor in a front on collision in a GT40 would be to avoid "submarining" (that’s, where you end up in the footwell) due to the lay-back position. .

 

[ChrisL]

Oops... the previous post should have read "4 or 5 point", not "5 or 6 point" /ubbthreads/images/graemlins/grin.gif

 

[Malcolm]

To be sure, I don't claim expertise in this area but answering the question with regard to a GTD, everyone I know who has harnesses uses the lap belt anchor points as built into the chassis by the factory for the hip belts. Maybe it is just coincidence that they work for both types of system?

Whilst my car has never had to go through SVA it has passed MOT's aplenty and the 6 point FIA belts never caused it to fail yet.

If you do end up putting in a harness system into a GTD, you will need a harness bar to run across the car behind the seats. This bolts to the lap belt top bolt holes and then you have to drill and bolt through the rear bulkhead to the angle chassis member underneath the rear internal window. Do not over tighten the bolts under this window as you can break the glass if not carefull. The main anchor points are the outer bolts.

Malcolm

PS in track and competition work over the last 12 years I have had two front end impacts. I whole heartedly agree with the comments on submarining. You don't want to go there! With one high speed and one low speed impact all bolt points have held up well.

 

[ChrisL]

I hope I didn't lead Jim astray with my advice. If Jim's main consideration is to meet regulation requirements, then that may be quite different to determining the "best" location. The 2003 Confederation of Australian Motor Sport regulation handbook recommends that the hip straps be placed at an angle greater than 85deg to a horizontal line drawn back of the center buckle. This is only a recomendation, and they would almost certainly accept a reasonable variation.

My personal opinion is based on an article that I read recently (which unfortunately I can't currently locate). The theory is that the hip strap should remain at hip level in a collision situation if it is to do its job properly. To test that it is likely to do this, I do the following…

If, while I am tightening my shoulder strap (which you should do as tightly as you can and still be able to breath) my hip strap rises above my hip, then I would conclude that either the hip straps are not adjusted correctly, or the lower mounting points are mounted too far back.

 

[Julian West]

FWIW, I've contacted Stockbridge racing (as mentioned by Chris) & they have been extreemely helpful with advice on the type of Harnesses & how to fit them.

Fitting them correctly is a science and a very important safety issue. There is a really strong case for fitting crotch straps to stop the 'submarining' (ie slipping under the harnesses').

If you can get hold of a copy of the RACMSA 'Blue book' it has a section & diagrams on the various type of approved harnesses. Let me know if you want me to scan & sned some pages to you.

Hope this helps!