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Author: Subject: How to position upper harness mounts
jps

posted on 23/1/21 at 04:38 PM Reply With Quote
How to position upper harness mounts

For those who've used 4point harnesses and had to add the fixing points for them, what was your approach to positioning your upper harness mounts, laterally across whatever tube they're anchored to?

In my case I'm mounting them off a horizontal tube across the rollhoop (already checked for the appropriate height from the seat base).
I've mocked up one so far, simply by running the belts through the seat slots with someone Insitu, trying to keep the belts as straight as possible as they come up the torso. The end result is for the mounting points to be more closely spaced than the Haynes Book shows, but the belts feel right: not too close to the neck but sitting nicely on the collarbone.

My seat is slightly angled (so it fits in) and so it's not easy for me to measure back from the seat centre line, then space the belts evenly off that, which was how I initially tried to set it all up...

My belts have no definitive mounting instructions in this respect and a Google shows neither Sabelt or Willians belt instruction cover this either...

[Edited on 23/1/21 by jps]

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ianhurley20

posted on 24/1/21 at 10:13 AM Reply With Quote
If you look at the latest IVA manual from the DSA it shows angles etc for belt mounting when viewed from the side, this is tested at IVA. The dimensions for spacing in the Haynes book are incorrect and will be offset a little,, getting someone to sit in the seat and choosing the best positions seems the best way perhaps with the gap shown in the Haynes manual as well as a guide. If you are using a horizontal across a hop similar to the Haynes most IVA centers require two braces fitted from the top of the hoop to the rear of the car as well.





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snapper

posted on 24/1/21 at 09:37 PM Reply With Quote
The key thing here is that if the belts through the seat belt holes the seat is then connect with the seat, the seat is considered a stressed item, counterintuitively if you run the belts either side of the seat that is fine for IVA.
As you can legitimately mount both upper rear belt mounts off 1 mount then spacing is immaterial.





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jps

posted on 25/1/21 at 06:50 PM Reply With Quote
Thanks both - looking at the IVA manual I can't find anything about belt angles - but my belts came with instructions that somewhere between horizontal or 20 degrees below was acceptable for the run from the shoulder to the mounting point, which I can achieve. Clearance on the seat cut outs OK for a reasonable 'average' sized person.

quote:
Originally posted by snapper
As you can legitimately mount both upper rear belt mounts off 1 mount then spacing is immaterial.


That's a good point - in looking at fitting instructions from the big harness manufacturers I see some produce 3 point harness, where the two chest straps join behind the driver - and a single strap then bolts in...

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