72 Duster 3 point seat belts
no matter where you mount the belt, if you run a belt thru the existing mopar a-body package tray, the tray will not support the forward/downward stresses placed on the belt under accident conditions. This is known as dynamic loading. The tray metal will either collaps, kink or actually severe the belt...probably all 3.
The metal there is strictly to support the cosmetic tray, rear speakers and the like. Its thin, weak, spot welded in and not up to the task. Even if you think the metal there isnt sharp enough to cut a belt, under the extreme stresses encountered in an accident, it can & will. I am assuming you want 3 point belts for passenger protection and not simpy looks?
Look at the lower rear seat belt mountings already in your car, they all have plates on the underside of the car. These are backer plates, big, heavy gauge, stress relieved, hardened metal, welded in place. They are this way not just to provide the seat belt mount bolts with sufficient thread material the DOT has mandated, but also to prevent tear out of the mount/bolt in an accident. I would try to copy that as closely as possible, its a proven design that meets minimum standards to retain the belt mounting point to the car, in the event of a collision.
I still think a custom harness bar of sorts is the better option. The pic shows a modern one and how it is used for front seat shoulder belt mounting. This is what they are used for. They mount to the structural sides of the car and have loading support bars vertically. This is all by specific design, not by accident, for good reason. The shoulder belts have to support the loading and in order to do that, they must be mounted correctly, otherwise very bad things happen, and youd be liable for that legally speaking. Good luck.
no matter where you mount the belt, if you run a belt thru the existing mopar a-body package tray, the tray will not support the forward/downward stresses placed on the belt under accident conditions. This is known as dynamic loading. The tray metal will either collaps, kink or actually severe the belt...probably all 3.
The metal there is strictly to support the cosmetic tray, rear speakers and the like. Its thin, weak, spot welded in and not up to the task. Even if you think the metal there isnt sharp enough to cut a belt, under the extreme stresses encountered in an accident, it can & will. I am assuming you want 3 point belts for passenger protection and not simpy looks?
Look at the lower rear seat belt mountings already in your car, they all have plates on the underside of the car. These are backer plates, big, heavy gauge, stress relieved, hardened metal, welded in place. They are this way not just to provide the seat belt mount bolts with sufficient thread material the DOT has mandated, but also to prevent tear out of the mount/bolt in an accident. I would try to copy that as closely as possible, its a proven design that meets minimum standards to retain the belt mounting point to the car, in the event of a collision.
I still think a custom harness bar of sorts is the better option. The pic shows a modern one and how it is used for front seat shoulder belt mounting. This is what they are used for. They mount to the structural sides of the car and have loading support bars vertically. This is all by specific design, not by accident, for good reason. The shoulder belts have to support the loading and in order to do that, they must be mounted correctly, otherwise very bad things happen, and youd be liable for that legally speaking. Good luck.