MikeR
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| posted on 21/7/10 at 04:40 PM |
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Adjustable 4 point upper harness mount - IVA OK?
Folks,
An idea ...... instead of welding in my harness mounts on the top chassis rail, i want them higher up due to being 6'3" tall.
I'd rather not weld a bar across the roll hoop as it will either interfere with the diagonal and my potentially MSA approved roll bar (blue book
design) or the passenger harness mounts will be in funny places and potentially not safe.
SO ........ the ideal.
Take a tube / bar and weld in the seat belt mounts at the correct spacings. Now hold this at the correct height against the back of your roll bar.
Drill a hole either side of the roll bar upright. Fit a u-clamp (exhaust clamp) and you've got the seat belts held in place at what ever height
you want.
Ok, needs a little modification, the holes in the tube should really be a boss but, can anyone think of a reason why this won't be legal for the
IVA / MSA?
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Bluemoon
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| posted on 21/7/10 at 04:51 PM |
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I don't think exhaust clamps are 8.8 rated...
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matt_claydon
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| posted on 21/7/10 at 05:59 PM |
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There's a major irony in saying you don't want to compromise the roll bar and then suggesting using an exhaust clamp as part of your seat
belt mountings!
You can get roll-cage clamps to use as part of a bolt-together cage that may be suitable.
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MikeR
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| posted on 21/7/10 at 06:13 PM |
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Why is the exhaust clamp an issue? the seat belt mounting goes behind the roll bar therefore isn't all force in an accident taken up by that.
The u clamp is only stopping upwards / downwards motion and allows adjust-ability.
The bolt together cage bits have welded tabs that fix the location. (ok with just me in the drivers seat this isn't a problem - but if thats
what i'm doing i could just weld the bar in place, I wanted to get peoples views if the adjust-ability was feasible / safe).
(if the clamp itself is an issue, i could fabricate something from 5mm steel and 12.8 grade bolts).
[Edited on 21/7/10 by MikeR]
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norfolkluego
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| posted on 21/7/10 at 07:04 PM |
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Sort of with this now, so the bar/clamps are not part of the mounting, just an adjuster/tensioner - yes.
Couple of things spring to mind, the bar and clamp would have to be as strong as the mount otherwise if they failed the belts would be nicely anchored
but you'd be loose inside the belt.
You're talking about an MSA rollbar diagonal, does that mean you're going racing/sprinting or something, if so I'm not sure your
adjuster would get MSA scrutineer approval, if there are any of those nice scrutineer chaps on here I'm sure they'd let you know one way
or the other.
[Edited on 21/7/10 by norfolkluego]
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Bluemoon
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| posted on 21/7/10 at 09:10 PM |
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One more thought, without a drawing of what your thinking of doing I'm not quite sure, but you may get some force along the camp direction as
the belts pull down on the upper mounts as well as forwards in an accident. I suspect the IVA tester might be concerned, it maybe worth ringing VOSA
to discuss.
Not sure how the vertical adjustment works in a production car, might be possible to copy/use the idea?
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matt_claydon
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| posted on 21/7/10 at 09:33 PM |
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Is there any reason why you want it adjustable? As long as the anchorage is above the height of the shoulder it will be safe and effective. Within
reason it doesn't matter if it's quite a lot above.
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MikeR
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| posted on 21/7/10 at 09:50 PM |
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The issue is that when ever i've drawn out the rear belt upper mountings, i've found that they clash with the diagonal for the
passenger.
the simple solution is not to put the mountings in the same plane as the roll over bar but to weld a bar behind the roll over bar and fit the
mountings to the back of that.
If i'm doing that, i wondered why not make the seat belt mountings bar adjustable therefore if a smaller driver got in for a long drive / i
changed seats / sold the car, it could be adjusted for them (with some spanners and about 10 minutes).
Wouldn't the upwards force of the belts only be on the lap belts, the shoulder belts being to stop you going forwards. If they're level
with your shoulders they just pull in a horizontal line - or am i not understanding the physics involved.
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