Harness bolt thread?

[mattstead]

Hi, just about to locate my harnesses but think the best option would be to obtain some solid mild steel and weld it to the chassis and tap it to the correct thread. Am I right in thinking Haness bolts are 7/16 UNF? and is it standard UNF thread or Fine? Also, if I was to go through a chassis tube and put a nut on the other side instead, I presume Mr IVA would want me to weld in an insert tube to the chassis?

Thanks.

[Steve_D]

mattstead said:

Hi, just about to locate my harnesses but think the best option would be to obtain some solid mild steel and weld it to the chassis and tap it to the correct thread. Am I right in thinking Haness bolts are 7/16 UNF? and is it standard UNF thread or Fine? Also, if I was to go through a chassis tube and put a nut on the other side instead, I presume Mr IVA would want me to weld in an insert tube to the chassis?

Thanks.

They are 7/16 UNF the F meaning fine.
If you use the standard seat belt bolts with the shallow head IVA will accept. Any other bolt will have to be marked as high tensile ie 8.8 or better.
Section 19 of the IVA manual has all the info you need on how to do the mount but safe to say simply welding a nut to the chassis will not be acceptable.

Steve

[mattstead]

thanks for the info, I was planning on welding a long threaded tube to behind the chassis near my shoulders to put my 8.8 rated harness bolts through (the same as on a westfield)... I just expected to have to tap my own tube, Didn't know what the F on UNF stood for, so any 7/16 tap that says 7/16 UNF will do?

[kennyrayandersen]

or tapping into a relatively thin plate. I'm stateside, but a structural engineer (aerospace). I'm taking an educated guess (you should get the official documentation of course), but the likely configuration is probably a welded plate, with a washer on the back, or underside and a tension bolt and nut. Check the nut -- many are meant to be in shear applications. I've seen many an engineer specify a really strong bolt with a nut that had only half the bolt strength... oops, ping!

[magpies]

Hi

what you will probably find is that there needs to be a threaded tube welded into the roll cage from both ends (the welds to be of good standard and not dressed)so that in an accident the cage will not crush. The threaded tube to be at 90deg to the force acted by the seatbelt.
This is what I needed to do to pass the SVA and I cannot see why the IVA would change it.

[GreenV8S]

Do you have the harness yet? Sometimes they come with small mounting plates suitable to be welded on the back of your mounting plates. If not, I'd rather see a full nut welded on (to make it captive) rather than a tapped hole in mild steel. It'll be better material and rather stronger.

[mattstead]

Hi, yes I have the Harnesses, I also have the eyelet bolts and I bought some Fia captive nuts on big fat plates, but as I don't have anywhere on the chassis to mount them and my Chassis tubing is too big for even the longest of eylet bolts to pass through i figured on ditching the captive nuts on plates for the upper mounts and welding on some solid steel bar and tapping it as Westfield do.

[robcollingridge]

These are the (lower) six point harness mounts in the Fisher Fury. They need to be very robust for pass SVA/IVA.