Door Armrest Reinforcement

[martincom]

While re-assembling my '71 D100 after a complete paint, I was just marveled by the fact the door interior trim panels were still in one piece and not cracked apart. This is because the armrest is solely attached to this trim panel. As such the trim panel not only carries the load of the arm, but more significantly, all the force to close the door, as the armrest also serves as the grab handle for closing. So I decided to fabricate a reinforcement plate so the the trim panel would no longer carry either of those forces.

I was expecting to find posts by other on this topic, as I know it has been done before by others, However, a search revealed nothing.

I started with a steel plate that would enclose the opening in the door inner shell from the latch mechanism to the rear of the opening. I utilized the same gauge of steel as the opening mechanism mount, #12. The plate dimensions are 8-5/8 x 6-1/8".

I mounted the plate to the door utilizing the same size of fasteners as the door opening mechanism,, #10 x 1/2" pan head sheet metal screws.

Next, I removed the armrest from the inner trim panel and mounted the panel. I found a yellow grease pencil was nearly the same diameter as the armrest fastener opening in the panel. I inserted the pencil through the panel fastener opening at the same angle as the fasteners would (by dead reckoning) and marked the steel plate previously mounted.

At the grease pencil markings, I drilled the mounted steel plate at the same angle of the armrest fasteners, again by dead reckoning, to a diameter that would accept a threaded rod coupler.

I removed the inner trim panel and the steel plate. On the bench, I laid out the trim panel on a protective towel face down. I snugly mounted the threaded rod couplers in the armrest mounting holes. I actually placed a 1/4 flat washer between the threaded rod coupler and the trim panel, to prevent it from becoming cocked in the overly large armrest hole, but I neglected to do so when mocking up for the photo.

I placed the steel plate over the threaded rod couplers,aligning the previously drilled holes with the threaded rod couplers. I allowed the steel plate to rest on the back side of the inner trim panel. I then tack welded the couplers to the steel plate. I utilized the MIG welder for the tack welds to minimize the amount of heat and not damage the inner trim panel.

Once tacked, I re-installed the steel plate and trim panel and checked the fit. The threaded rod coupler faces were approximately a 1/4" from the back side of the inner trim panel. I removed the inner trim panel. I cut a couple of 3" lengths of 1/4" threaded rod stock and threaded them into the threaded rod couplers. I then threaded a 1/4 nut down over them until snug against the threaded rod couplers. I re-installed the trim panel and checked the fit. The backside of the trim panel was nearly against the face of the nut.

I removed the trim panel and the steel plate. I placed a 1/4 USS flat washer over the threaded rod and snugged it down against the previously installed nut with another nut. I then welded the nut and washer to the threaded rod coupler. Again, I removed and checked the fit with the steel plate and inner trim panel installed-OK. I then finalized the welds. I probably should have utilized the acetylene welder, rather than the MIG, for everything but the initial tack. It would have yielded a much more appealing, in appearance, welds. However, I was concerned about welding the threaded rod I left in place, to prevent heat distortion of the threaded rod coupler and nut, to each of them---in which I did so anyway in 1 of the 4. So I had to drill the rod out and re-tap one. I also chased a tap through the threaded rod couplers after each weld. While the welds were as not as pretty as I would have liked, they do have more than adequate structural integrity.

The 1/4 flat washer on the face of the threaded rod coupler & nut stack also provides a securing surface for the inner trim panel to be drawn up against, when the armrest is installed. This prevents the inner trim panel from rattling/squeaking. I also added 1/4 USS flat washers to the armrest attaching holes, which were also overly large. The armrest foam holds them in place until the fasteners are installed. I utilized 1/4 x 1" Phillips pan head bolts with 1/4" internal tooth washers to mount the armrests.

[Wildergarten]

Good job, and certainly solid. For me, having a lathe, it would be easier just to tap the end of a piece of 3/4 bar, cut it to length at an angle, and weld it to the plate. Can you get dimensions of the length from the washer to the center of the coupler nut at the outer plate surface and the angle of the installed face?

To locate the cutoff bar for the weld, I'm thinking I could grind a point on a piece of 1/4 all thread and use it as a transfer punch, drill the hole at the angle and use the threaded in rod to locate the part for welding.

Thanks,

Mark

[Wildergarten]

Good job, and certainly solid. For me, having a lathe, it would be easier just to tap the end of a piece of 3/4 bar, cut it to length at an angle, and weld it to the plate. Can you get dimensions of the length from the washer to the center of the coupler nut at the outer plate surface and the angle of the installed face?

To locate the cutoff bar for the weld, I'm thinking I could grind a point on a piece of 1/4 all thread and use it as a transfer punch, drill the hole at the angle and use the threaded-in rod protruding into the hole to locate the part for welding.

Thanks,

Mark

[Wildergarten]

Good job, and certainly solid. For me, having a lathe, it would be easier just to tap the end of a piece of 3/4 bar, cut it to length at an angle, and weld it to the plate. Can you get dimensions of the length from the washer to the center of the coupler nut at the outer plate surface and the angle of the installed face?

To locate the cutoff bar for the weld, I'm thinking I could grind a point on a piece of 1/4 all thread and use it as a transfer punch, drill the hole at the angle and use the threaded-in rod protruding into the hole to locate the part for welding.

Thanks,

Mark

[soopernaut]

I don't recall anybody doing anything like this on this site before. Maybe that is why your search came up empty. The factory pieces seem to hold up pretty well considering they aren't reinforced. I've seen more issues like this in 80s vehicles.

[Wildergarten]

I don't recall anybody doing anything like this on this site before. Maybe that is why your search came up empty. The factory pieces seem to hold up pretty well considering they aren't reinforced. I've seen more issues like this in 80s vehicles.

A completely different approach would be to build up some matt-roving and fiiberglass resin on the back side with encapsulated washers and nuts. There would still be big forces on the panel screws, but it would still be stiffer and a lot easier to execute.

[martincom]

Can you get dimensions of the length from the washer to the center of the coupler nut at the outer plate surface and the angle of the installed face?

I'm green with envy. I'd love to have a lathe, mill, break, shear, english wheel, etc. It is not so much the cost, which is always a factor, but space to set them up. Here, in the frozen tundra, it not only costs more per square foot to construct, but that additional cubic feet also has to be heated--which isn't cheap. We only stay here for the low taxes....and if you believe that, I have a bridge or two you should buy.

I had already assembled the door. I disassembled it again as far as the trim panel. I had applied 4 mil plastic behind the trim panel w/black duct tape. I would need to remove all that, which would have destroyed it, to remove the reinforcement plate and measure the angle by placing a protractor against the surfaces. As such, I "eyeballed it" and it appears to be 28 degrees. I also "eyeballed measured" the angle of the armrest mounting pad, in the trim panel, and it also appears to be 28 degrees, as well.

It would have been impossible to obtain an accurate measurement of the length of the angled projection, from the steel mounting plate, as the welds would have obstructed the measurement. I would suggest you install the steel plate and the inner trim panel, cut a length of 3/8 bar at 28 degrees,insert that in the armrest mounting hole until it squarely against the steel plate and then mark the required length as best as you can along the center line axis.

[Wildergarten]

I'm green with envy. I'd love to have a lathe, mill, break, shear, english wheel, etc. It is not so much the cost, which is always a factor, but space to set them up. Here, in the frozen tundra, it not only costs more per square foot to construct, but that additional cubic feet also has to be heated--which isn't cheap. We only stay here for the low taxes....and if you believe that, I have a bridge or two you should buy.

If you think construction is cheap in the Santa Cruz Mountains above Silicon Valley is cheap, I'll buy that bridge.

I too have a problem with space. The shop is a two car garage. I have a lathe, space for a mill, a blast cabinet, a 6' welding table, and a table saw with a catch table in it already. Space was so tight I put the compressor in the rafters, separating the tank and the pump (all kinds of fun was had with the dump valve, the condenser, and the drain lines). Yet there is still room for the truck, at least once there's a body on it, and I get the bumper out of here, and I get the trans resealed, along with the t-case...

I had a neighbor who has a machine shop and inherited another he had to get rid of or I wouldn't have bought it. This was his father-in-law's 7' South Bend 13. I cleaned it up and rebuilt the whole thing, but it's a dog for accuracy. The ways are shot, the cross-slide gib is all the way in, and it still moves around. I'd have been money ahead if I'd bought a new Grizzly, but it does look cool.

I had already assembled the door. I disassembled it again as far as the trim panel. I had applied 4 mil plastic behind the trim panel w/black duct tape. I would need to remove all that, which would have destroyed it, to remove the reinforcement plate and measure the angle by placing a protractor against the surfaces. As such, I "eyeballed it" and it appears to be 28 degrees. I also "eyeballed measured" the angle of the armrest mounting pad, in the trim panel, and it also appears to be 28 degrees, as well.

Thank you muchly! I'll go from there.