Harness mounting points

[Mark Stanton]

Could we possibly continue these posts and note at beginning of each one whether you are referring to inertia belts or MSA type harnesses            

I'm thinking there is quite a difference between the two  

For me I can see the need for inertia belt fixing to be higher    

and similarly harnesses lower    

don't forget Newton   "every action has an opposite and equal reaction"........ thingy          

[BuGsBuNnY]

With a seat belt mounting level or above shoulder height there is less pulling down on shoulders in an event of a head on collision than on a seatbelt that is mounted below shoulder line. This is because as the body moves forward in a collision with a seat belt mounted to low it as a pulling down effect on shoulders due to the mount be being below shoulder height ,this cannot happen if the mounting is level or above shoulder height.

This is my point; the seat belt DOES NOT DO ANY PULLING WHATSOEVER (Unless it has active tensioners). If your shoulders are travelling foward the seat belt applies the same force as your shoulders but in exactly the opposite direction.

All it does is restrain you; and this is done best with the mounts at or lower than shoulder height.

The seatbelt does not pull indeed. It just applies a same and equal (opposite direction) force to your body.

I apologise for trying to make it more understandable. It seemed to have had the opposite effect and confused rather than make the situation clearer. I would love to talk physics and do a force diagram but too much to do, too little time.

mat1800 and miker nailed exactly what I wanted to say.

I have been in the UK for 9 years and English is NOT my mother tongue. Terminology on different subjects is very hard to get right for me sometimes, so if I seem to not be able to use the right words sometimes, do excuse me.   I would love to explain in my mother tongue, but it will seem all Greek to most of you...  

[nikpro]

let me phrase it another way.

The belt is soft and will take the easiest shape it can. Push something squishy into it and it will form a round shape as thats the most efficient.

You're body is squishy (ish). push into the belt and it will try to form a round shape. If the belt mounting if below your shoulders think how round that shape is going to be, there goes your back. Mount above the shoulders and the round squishy shape isn't that accute, there go your shoulders / ribs / other bits the belts are holding and it hurts like hell (mate broke his in a crash).

(just made this up as i had a sudden flash or inspiration and it seemed to fit)

I'm guessing the 10% business is a leway as your body can squish a bit and not break.

Last post on this subject for me - but again this is not right.

A properly adjusted harness holds you tight in the seat which is rigid. In an accident your body should not move never mind form any round shape - the seat you are rigidly straped into provides the support. Your guts inside will move and it is the G-force that often kills in a racing accident.

A harness mounted at or below shoulder level can be adjusted better to RESTRAIN you than one mounted higher. It's simple and logical. Plus shoulder straps slip off much easier if mounted to high.

AS Mark said - this applies to Hrnesses as per the original post and not seat belts.

As an aside - F1 belts are mounted at shoulder or below shoulder level; I've never heard of spinal compression caused by the belts - just concusion from the brain hitting the inside of the skull and that's why the haans device was developed as well as neck injuries

[MikeR]

ok i'm well out of my depth here but i wanted to add a couple of points and see if anyone thinks they make a difference.

[race harnesses]

You're harness isn't 100% tight otherwise you wouldn't be able to breath / move your arms etc / would be in constant pain. Yeah, it is tight, but not totally restraining.

2ndly, youre belts are designed to give a little in a crash to reduce some of the impact. Therefore you can move a little more.

So you're not totally rigidly strapped in.

Now ...... having said that, i understand and find it hard to disagree with your post bugs. But perhaps the thing to remember is the SVA manual is designed to cover all cars, so perhaps in this instance they are refering to 3 point 'car' belts and race harnesses are just having to comply with the requirements.

Either way, my aim is to have my harness around 1" lower than my shoulder which complies with the very comprensive Austrailain rules which as i recall do cover race harnesses, will keep the belts on my shoulder, gives minimal scrunching / back breaking in a crash and meets RAC guidelines ...... oh and should fit my car

Oh F1.... i've just found the FIA rules and they all seem to be in french. My french is cra.... not very good. Seems to imply to me that ..... the F1 harness are over the drivers shoulder and mounted in the seat itself (so they can remove the driver in his seat if he's in a really bad way).

edited again to say the second half of the document is in English!

edited again to say "bum, found out how to test a harness, not mount one!

[Mark Stanton]

SVA manual is designed to cover all cars, so perhaps in this instance they are refering to 3 point 'car' belts

Well spotted ................ and I think that is where some of the confusion has been caused with folks interpretation of this thread      

SVA is more commonly applicable for standard 3 point inertia seat belts      

Harness fitments need to refer to MSA safety points.

However if you do intend to fit harnesses for SVA purposes - then to pass, ensure you fit them to SVA rules and change after if necessary.

If you are using harnesses then they should be pulled very very tight so you are unable to move your torso or slide and submarine  

[MikeR]

of course the assumption is that the MSA is correct.

This is soooo going to cause trouble now, please understand i'm quoting someone else and am likely to be COMPLETELY wrong.

Mate works in the car industry on fuel systems and the rules he has to stick to seem to exceed the MSA on safety. His quote was, "what might have been good enough to race in 1970 isn't good enough for the car you drive down the road in today".

Now I appreciate that is an exageration on the dates etc but some things like copper pipe for fuel lines, non return flaps on the fuel fillers and vents, how to vent the tank all seem to exceed the MSA spec with my limited knowledge of the MSA spec. Now if that is the case of fuel systems, maybe its also true on seat belts.

anyone got a large rock, flame proof suit and spare identy i can borrow for a while?

[Mark Stanton]

of course the assumption is that the MSA is correct.

ROFLAO                  

[MikeR]

what you trying to say mark    

You agree with me that there is the possibility (i'm not saying that it is) that the MSA spec could be a smidgen out of date and have room for improvement?

Or

Whooohooo what a statement, thats going to cause some interesting discussion i'd better get a fresh cup of tea and some chocolate hobnobs.

Time for me to get some dinner, seems to be a bbq starting somewhere.  

[Mark Stanton]

You agree with me that there is the possibility (i'm not saying that it is) that the MSA spec could be a smidgen out of date and have room for improvement?

Weeeeeeeeelllllllllllllllllllllllllllllllll ................ perhaps only the slightest of things need nominally updating and amending    obviously the MSA being the governing body of all Motorsport activities regularly address these matters alongside all aspects of club motorsport, I'm sure, maybe, almost, once in a while    

[Flat Eric]

The consensus of opinion appears to favour, mounting harnesses positions, higher than shoulders.

The problem that I now have, is that my shoulders are higher than the holes in seat. Therefore if I do so, the belt will not follow a straight line (ie it will be down from mounting point to seat hole - up to shoulders - then down to buckle).

Although it is a carbon seat, in the event of an accident I  would assume the force of me (82kg) moving foward would break seat, thus creating a slackness in shoulder harness, with obvious consequences. Or am I not understanding strength of carbon fibre? - which I am also happy to accept.

I could mount it lower, so that belt follows an uninterupted flow, to avoid this.

I have read the previous posts, but what is the lesser of my two evils.

Or

If I have an accident in the Westfield creating this amount of energy, am I b*******ed what ever I choose to do.

[nikpro]

The consensus of opinion appears to favour, mounting harnesses positions, higher than shoulders.

Really!

I can only find two contributors that favour higher mounting, the rest of us say lower; all rally cars are lower/level and all other race cars I can think of are lower/level with shoulders.

Previous post states MSA blue book reccomends 10% in either direction with an acceptable range upto 45 deg LOWER.(Not Higher)

Funny consensus of opinion that!

[Peter M]

Take a look at this documentation from a harness manufacturer.

fitting of harness

Extract

Proper Installation is Important

The effectiveness of a restraint assembly is also influenced by attachment techniques. The principal precaution for installing the mounting hardware to the vehicle is to minimize bending stress in the fitting. This is achieved by making sure the belts pull from a straight angle against the hardware. The assembly should be installed so that the straps do not rub against any surface that can cause the webbing to fray. The anchoring mechanisms should also periodically be checked so that they don't become loose or weakened.

Proper installation of the restraint assembly also means achieving the correct fit to the driver. Belts should be as short as possible to reduce stretching for better control of occupant movement.

The attachment points must provide the optimum geometry to minimize movement of the belts. Lap belts perform best when they act at an angle between 45° and 55° relative to the longitudinal axis of the vehicle as illustrated in part A of the Figure. This angle permits the lap belt to react to the upward pull of the shoulder harness. A system installed with a shallow belt angle, as shown in part B of the Figure, permits the shoulder harness to pull the lap belt up off the pelvic area and into the abdominal region with the likelihood of injury to internal organs.

The end attachments of the shoulder harness must also be installed at appropriate angles. The ideal position is anywhere between 5° below and 30° above the driver's shoulder, as seen in part C of the Figure.

If the upper attachment point falls significantly below the driver's shoulder, then a spinal compression injury is likely to occur. In an accident situation, the shoulder belts pull down and back on the torso as they resist the forward motion of the driver. The resultant restraint force compresses the spinal column and will add to the stresses in the spine already caused by the force of the crash impact.

[simple]

It strikes me that a compression injury to the spine would be caused only if the Lap belt of whichever type of restraints were used was not tight enough to stop your backside lifting off the seat. if your backside is held entirely still then your upper body would merely rotate providing no compression force to your back.

[MikeR]

I think this is a case of everyone having there own opinion. I've got mine, its inline with what a manufacture states. I'm sticking to that.

Just out of curiosity, if a manufacture said your cylinder head bolts should be done up to 100lbs, would you do them up to 45 because you think you know better?

i know thats harsh but we're talking about the difference potentially between walking and not here! I'm going to butt out now.