M37 Restoration Project - Revived

[ab705]

As mentioned earlier, I want the front and rear turn signal/stop lights to retain their original 'outward' appearance, but I want to increase their visibility when in use. One thing that I plan to do is substitute LED lamps for the original incandescent bulbs. The other thing that I want to experiment with is to repurpose the blackout marker light slot of each light to serve as an additional amber or red light. As you already know, when the original blackout light was in use, it only displayed a pair of small, dim, modified triangles.



I removed the parts from the blackout marker light slot, as shown below:



My experiment will be to replace the above parts with a section of a modern red stop light lens for the rear lights and an amber turn signal light lens for the front lights. But before doing that, I wanted to paint the light 'doors' the correct color. The two light doors shown below are for the front turn signal lights. The blackout marker light parts have been removed, and the glass lenses have been masked using a liquid "frisket" instead of masking tape, which was much easier to use than tape because of the shape of the lenses. It's important to allow the masking frisket to dry thoroughly before painting.



After spraying the light doors with Marine Corps green and allowing the paint to dry for a couple of days, it was easy to peel off the masking frisket:



Here are the doors after removing the frisket:



The next step will be to cut rectangular red and amber pieces out of some modern tail light and turn signal lenses for installation in the blackout marker light slots, and then try some different LED lamps to see how they compare.

 

[ab705]

More work on the lights. I cut two rectangular pieces out of an amber turn signal lens for a late-80s Toyota pickup. I also cut two rectangular pieces from a red brake light lens (not shown) for some kind of Honda all-terrain vehicle.



I just installed the amber and red pieces in what were originally the blackout marker light slots in the front and rear light doors. One of the photos below also shows a couple of new square-cross-section O-rings used to seal the light doors to the light bodies. I got the O-rings from McMaster-Carr.





So, just to clarify: The parking and turn signal lamp positions haven't changed from their original positions. The only change is that what used to be the blackout marker light will become an additional turn signal light, which should make the turn signals more visible. It will be the same with the rear lights: The tail light and stop/signal light positions haven't changed from their original positions, but the former blackout marker light will become an additional stop/signal light.

Below is a photo of the interior of one of the front lights with LEDs installed. These aren't the final LEDs, as I'm still experimenting with different types to see what works best. I have a feeling that I won't be making a final decision until I can try them out on the truck in typical day and night viewing conditions., but it's a start, anyway.



These are a few of the LED lamp types that I'm messing about with. So far, for my M37 lights I'm leaning toward the ones without the built-in projector lenses.

 

[ab705]

The original ID data plate for my 1954 M37 was missing, so I used Adobe InDesign to create what I think is a pretty accurate facsimile of the original ID data plate design that is appropriate for my truck, as shown below:



There were several steps involved in creating a new etched-aluminum data plate like the original.

First, I printed a mirror image of the design on a special kind of inkjet transparency film. These sheets have a slightly frosted coating on one side, which apparently allows them to accept more ink than an ordinary transparency film. I maxed out the CMYK channels for the black areas in InDesign and set the ink density higher in the printer control app in order to achieve pretty decent opacity.



I then adhered a sheet of photoresist film to a carefully cleaned aluminum sheet, working under subdued incandescent light (the film is UV sensitive). It's hard to get this stuff on without trapping bubbles. There is a 'floating it on' technique for doing it with water, but I tried it and didn't like that method, so I just had to refine my pressing and rolling technique on a few practice pieces until I managed to adhere some sheets without bubbles. Here's one of them:



I placed the printed film image emulsion side down on the photoresist film, placed a sheet of plain window glass (not sun-blocking glass) over it, with a piece of foam rubber behind it to keep it pressed tightly against the glass, and exposed it to direct noon sunlight for about 30 seconds.

After exposure I removed the thin plastic protective layer from the photoresist film and 'developed' the photoresist in a mild solution of washing soda, which removed the unexposed (unhardened) portions of the photoresist. I then etched the aluminum with an acid solution (I'm still working on figuring out the optimum formulation, so I won't list it here yet). I had a few trial and error (mostly error) runs before I got a couple of decent results. Here's one of them:



Next, I chemically darkened the etched area with Aluminum Black from Birchwood Casey.



Soaking the plate in acetone for a few minutes loosened the photoresist and allowed it to be brushed off easily with a soft brush. I then trimmed the edges to the cut lines with a shear.

Here's the end result so far. You can see some reflection from the protective coat of satin urethane that I sprayed on, but the background is actually a nice solid black.



The etching leaves the letters slightly raised, like the original data plates. I think I'll punch the rivet holes with my Roper-Whitney punch instead of drilling them. I plan to use a 3/32" number and letter punch set to add the serial number and other data. I'll probably make a couple of extra plates in case I mess things up when I'm punching the data onto the plate. In hindsight, I probably should have waited to spray the urethane coating on until after I punch the data onto the plate. I suppose I can dissolve the coating and then re-spray it after punching.

There are a lot of variables involved, and it took about eight attempts before I got a couple of plates that I was satisfied with. I'm sure that with practice I could streamline the process and improve my success rate, but that can wait. On to other tasks...

 

[Mullaney]

The original ID data plate for my 1954 M37 was missing, so I used Adobe InDesign to create what I think is a pretty accurate facsimile of the original ID data plate design that is appropriate for my truck, as shown below:

View attachment 929458

There were several steps involved in creating a new etched-aluminum data plate like the original.

First, I printed a mirror image of the design on a special kind of inkjet transparency film. These sheets have a slightly frosted coating on one side, which apparently allows them to accept more ink than an ordinary transparency film. I maxed out the CMYK channels for the black areas in InDesign and set the ink density higher in the printer control app in order to achieve pretty decent opacity.

View attachment 929459

I then adhered a sheet of photoresist film to a carefully cleaned aluminum sheet, working under subdued incandescent light (the film is UV sensitive). It's hard to get this stuff on without trapping bubbles. There is a 'floating it on' technique for doing it with water, but I tried it and didn't like that method, so I just had to refine my pressing and rolling technique on a few practice pieces until I managed to adhere some sheets without bubbles. Here's one of them:

View attachment 929460

I placed the printed film image emulsion side down on the photoresist film, placed a sheet of plain window glass (not sun-blocking glass) over it, with a piece of foam rubber behind it to keep it pressed tightly against the glass, and exposed it to direct noon sunlight for about 30 seconds.

After exposure I removed the thin plastic protective layer from the photoresist film and 'developed' the photoresist in a mild solution of washing soda, which removed the unexposed (unhardened) portions of the photoresist. I then etched the aluminum with an acid solution (I'm still working on figuring out the optimum formulation, so I won't list it here yet). I had a few trial and error (mostly error) runs before I got a couple of decent results. Here's one of them:

View attachment 929461

Next, I chemically darkened the etched area with Aluminum Black from Birchwood Casey.

View attachment 929462

Soaking the plate in acetone for a few minutes loosened the photoresist and allowed it to be brushed off easily with a soft brush. I then trimmed the edges to the cut lines with a shear.

Here's the end result so far. You can see some reflection from the protective coat of satin urethane that I sprayed on, but the background is actually a nice solid black.

View attachment 929464

The etching leaves the letters slightly raised, like the original data plates. I think I'll punch the rivet holes with my Roper-Whitney punch instead of drilling them. I plan to use a 3/32" number and letter punch set to add the serial number and other data. I'll probably make a couple of extra plates in case I mess things up when I'm punching the data onto the plate. In hindsight, I probably should have waited to spray the urethane coating on until after I punch the data onto the plate. I suppose I can dissolve the coating and then re-spray it after punching.

There are a lot of variables involved, and it took about eight attempts before I got a couple of plates that I was satisfied with. I'm sure that with practice I could streamline the process and improve my success rate, but that can wait. On to other tasks...

.
Wow...
That is an amazing process.

.

 

[ab705]

Wow...
That is an amazing process.

To be honest, it's a rather tedious process, but as long as I'm learning something and getting a decent result, it's worth a bit of fuss.

 

[M813rc]

Very impressive work!

I did something similar with the front blackout marker lights on my Mighty Mite, since they didn't come from the factory with turn signals.
I cut amber reflector lenses with the focus circle in the middle to fit the holes, using that type because the light holes were small and the circle intensifies the light output.
I used amber LED bulbs with a built in resistor so the flasher "senses" them as regular bulbs and flashes them.
They are amazingly bright, and very visible in sunlight.

I used Gama Goat style lenses on the back, but having seen how you did the smaller aperture lights, I may have to rethink that and follow your example.

Cheers

 

[ab705]

I used amber LED bulbs with a built in resistor so the flasher "senses" them as regular bulbs and flashes them.
They are amazingly bright, and very visible in sunlight.

I used Gama Goat style lenses on the back, but having seen how you did the smaller aperture lights, I may have to rethink that and follow your example.

Thanks Rory. I probably won't know exactly how well my modified lights will work until I try them in real-world conditions, but on the workbench, they seem to be very bright, with a major, attention-getting increase in brightness between the parking/tail light and the signal light. I tried making a video showing the signal lights going off and on, but the brightness range of the lights is so much greater than the dynamic range of the camera that it really didn't demonstrate how it actually appears to the human eye.

I tried using some amber lens pieces that had a concentric Fresnel pattern, but IIRC, I could see a bright spot from a wider viewing angle with the rounded-rib style pieces that you saw in my post. Of course, there are so many different lens pattern variations, as well as LED shapes/lengths/configurations, that it's hard to make any kind of generalization, but so far, so good. I also have a set of Gama Goat lenses that I can play with when that time comes.

I think the turn signal flasher that I purchased should work with LEDs without having to install a resistor to create a load, although I haven't tried it yet.

Al

 

[M813rc]

I was stuck using the really small bullet blackout lights, which is why I went with the the lenses I did after some experimentation. Your lenses definitely look like they'll work better for that slightly larger light. They look really good and "stock" with the lights off too, which is important.

I used the resistor LEDs because of the standard military flasher I went with, it is so very obvious under the hood I wanted it to look stock.

Cheers

 

[ab705]

I was stuck using the really small bullet blackout lights, which is why I went with the the lenses I did after some experimentation.

Those small modified blackout lights look like they will do a good job for you.