Further thoughts on custom ferrules and seat-belt bolts

The side seat belt harnesses are attached to brackets that are completely hidden from view and emerge from slots in the upholstery. So there is little freedom for movement, and a 180 flip of a free-rotating harness out of sight would be very undesirable. Under tension it could flip back suddenly loosening the belt.

So the side seatbelt mounts MUST be clamped.

Further the final washer under a AN nut serves to transition from the grip region to the threaded region - it should not itself be included in the calculation of the required grip range. So revisiting the use of an AN4-6A bolt with grip range 0.3125" = 7.93mm, taking away the mounting bracket = 3.2mm, one AN970 washer = 1.58mm, and the clamped seat belt harness = 2.5mm leaves 0.658mm of grip range. This is fully absorbed by a thin AN960 washer = 0.79mm under the bolt head.

So the prescription for the side seatbelt mounts is:

AN4-6A bolt with AN960-4L washer under the head. 2x AN970 washers separated by 1 machined AN960-4 and 1 machined AN960-4L washer. The AN4 nut is clamped directly on the outer AN970 washer

So I can commit to using the AN4-6A bolt and appropriate AN960-4L washer which are both trapped behind the seatbelt mounting bracket at assembly of the centre console rib, and complete the latter.

For the rear seatbelt mount, it is intended to use the free rotating ferrule arrangement. The bulkhead tab is 2.4mm thick. So assuming the use again of an AN4-6A bolt with grip range 7.93mm, taking away the bulkhead tab = 2.4mm, one AN970 washer = 1.58mm, and two machined AN960 washers = 3.18mm leaves 0.77mm grip range. This remaining grip range is similarly absorbed by a thin AN960 washer = 0.79mm under the bolt head.

So the prescription for the rear bulkhead seatbelt mount is:

AN4-6A bolt with AN960-4L washer under the head, the bulkhead tab, then two AN970 washers separated by 2 machined AN960-4 washers. The AN4 nut is clamped directly on the outer AN970 washer. If one chooses a clamped seatbelt bracket then the washer under the bolt head should be a normal thickness AN960-4, exactly as per the plans