G'day Rick,
The method I used in my FB sedan was a little different. The NCOP guidance on reinforcing plates doesn't mandate a shape, but requires:
a) the plates to be made of mild steel,
b) the surface area of the plates must not be less than 3750mm2 and have a thickness of 3-4.5mm (1/8-3/16”). VSB5B allows not less than 75mm x 50mm x 3mm (3750mm2), but requires the plates to be no thicker than 4mm,
c) the plates must be contoured to fit the vehicle body,
d) the plates must have a minimum 5mm corner radius with the plate edges closest to the body chamfered.
e) the bolts used must be 7/16” UNF SAE Grade 8.
I used this guidance to select long, skinny reinforcing plates (about 6"x1") with the UNF nut already tack welded to them, all cad plated. These were available from an engineering company that specialises in installing seatbelts.
I used a hole saw to cut a hole (26mm from memory) into the B-pillar (inside the car) at about shoulder height. I drilled two 1/8" holes in the reinforcing plate, one at either end, and made similar holes in the B-pillar (one above the 23mm hole, one below). I put a piece of fishing line on the plate and dropped it into the hole (catch it with the fishing line). Use the fishing line to pull it up, then put the seatbelt bolt into the plate (can't fall down now). Hold it in place with the bolt, and put a pop-rivet through the B-pillar hole into the plate. Repeat the pop-rivet for the other hole. The connection for the lower part of the seatbelt bolts through the floorpan, using the typical off-the-shelf 4"x6" reinforcing plates from Hemco.
You end up with a hole in the pillar with the plate behind it - can cover the hole with a plastic cap, though the seatbelt top sash guide covers most of the hole once it is bolted in place. Seems a bit funny leaving a hole there, but the surface area of the plate is a shitload bigger than the surface area of the bolt-head used in "Frankenstein" set-ups (much less likely to pull through in an impact). This is the same process reccomended by one US seatbelt manufacturer to refit old cars.
The trick to it all is to work out who your certifying body will be. For me it was an NSW RMS Authorised Restraint Fitting Station (
http://www.rta.nsw.gov.au/cgi-bin/index ... tting.form). This is not an engineers certificate, just an inspection and basic form to sign off and fairly cheap (>$100). I checked with the particular Restraint Fitting Station that they were OK with the method... a wise move before letting loose with a holesaw.
It is a good idea to also check how fussy the certifying body wants to be about belt location. The Restraint Fitting Station was not too fussed about where I put the bolts, as long as they "looked right". However, for my EK wagon I need to use an automotive engineer as the certifying body. The engineer is more fussy, and wants full NCOP compliance (he also didnt like the holesaw trick). NCOP is virtually identical to the requirements of ADR4 and ADR5 for seatbelt mounts. The requirements from NCOP start with a really techo drawing, and uses language that is almost impossible to understand for anyone other than a rocket scientist... words like “torso reference line” and “pelvis reference locus” sound like fluent gibberish. Because I had no choice but to comply, I worked my way through NCOP. It involved lots of measurements, protractors and spirit levels. I took lots of photos as I went, and have written it up (in plain English) as a Guide. The Guide text is still a little rough, but was OK by my engineer. If you end up needing to comply, shoot me your email address and I can send you a draft copy of the Guide.
Cheers,
Harv
