Seat belt anchorages

[DaveyB]

Hi guys,
Just looking at some harnesses for my build the bolts are grade 8.8 and I suddenly realised that the nuts that I have welded to my chassis are nuts i made on a lathe 19mmA/F BDMS x12mm long hexagon bar should they really be nuts of the same grade as the bolts I looked at IVA book it's not very clear unless I have mis-read it.

Any ideas
Thanks

DaveyB

[K4KEV]

Davey ....I have used M12 nuts for my build.... as I see it M12 is at least the equivalent of 7/16" UNF that normal seat belts use.

[DaveyB]

Are they nuts of a particular grade 8.8 or just mild steel ?


DaveyB

[Stot]

The upper ones on the roll bar are generally mild steel tubes. The bolts are working in shear trying to snap the bolt rather than trying to pull directly out of the threads so you should still get the full strength of the bolt.

Cheers
Stot

[Short]

This is the guide for use on minibuses and coaches - ive gone for 7/16

D. Where seat belts, other than looped belts, are anchored to the seat frame or the vehicle floor they must be secured with mounting bolts in accordance with the following:

Minimum Acceptable Size and Grade of Bolts for Seat Belt Anchorage’s


Type of Anchorage


Single Anchorage


M8 High Tensile Steel, M10 Standard Material


Double Anchorage

7/16" Standard Material, M10 High Tensile Steel


Note: Bolt head marks

Standard Material = P, 4.6 or SAE equivalent

High Tensile Steel = S, 8.8 or SAE equivalent

No Markings = Standard Material

If the examiner cannot determine the grade of bolt it must be assumed to be of Standard Grade.


From memory, nuts are not stamped with a grade anyway. M12 is well above the recommendation, and they really have no way of checking the strength of the nut anyway. As long as the bolt head is stamped, I wouldn't worry!

[flyerncle]

They go to all this trouble for seat belt mountings in buses,coaches and minibuses etc and the bolt to a mickey mouse floor.

[alga]

The bolt is the part that gets stressed in shear and in tension. As long as the nut is not made of cheese, it will hold.

[DaveyB]

Thanks guys thats great advice, I had fears I was going to have to get the grinder out !

Thanks again.

DaveyB

[flyerncle]

Make the plate longer and fold edges onto chassis rails to make it stronger.