Back to the future Voltage Gauge

[vintage6t]

I’m modifying my 50 Desoto with a MOPAR 383/727 Auto combo. Part of the mod is a change to a 12 volt electrical system with an alternator. One of my project goals is to keep the Desoto dash looking stock even with the more modern upgrades. With a 12 volt alternator system the factory Amp gauge is not really that useful as compared to a Volt gauge. With this in mind, I set out to create a modern Volt gauge that fits in place of the original Amp gauge and with a face plate that matches the stock gauges from 1950. This is a companion post to my previous PRND21 display post where after many attempts I determined how to closely match the original gauge faces:

 

Step 1 – Get a voltage gauge.

I didn’t want to spend a lot of money on a new gauge that I was basically going to disassemble, and possibly destroy, right out of the box.  Still, I wanted something that seemed to have decent quality. A Bosch Style Line gauge seemed to be a good choice based on size, price, and product reviews.

As dumb luck would have it, it turned out to be a good choice. Mainly because of its overall size, electrical terminal spacing, size of the needle, ease of disassembly, screw-on faceplate, and electrical adjustability via a built in trim pot.

[vintage6t]

Step 2 – Create a face plate blank

The task here is to create a face plate with the same dimensions as the stock gauge. It has to fit the old gauge bezel but also the face plate has to mount to the new gauge’s via its screw holes. To do that I first made a template out of manilla folder material. I then mounted it to the gauge to refine the fit.

Next I laid out sample numbering and printed it on paper. This let me determine exactly where the finished hash marks and numbers should go. To determine the exact layout, I hooked the gauge up to a variable voltage supply and marked where the needle landed across the full range of the desired gauge markings:  8, 10, 12, 14, 16, 18 volts. This took a number of tries to get the layout to my liking.

Once I was sure the gauge would layout as I wanted, I created the blank gauge face out of brass. The stock gauge faces are not flat, they have a slight radius to them and also have a small lip on the left and right edges. To shape my blank the same I made a buck out of wood. Basically I cut a 2x4 in half with the desired radius on a band saw. I then pressed the flat blank stock between the two pieces of the buck with a vise. While still clamped, I peened over the edges on each side to create the lips.

[vintage6t]

Step 3 –Create the gauge back plate

The stock gauges mount into a four position (Amp, Temp, Oil and Fuel) bezel assembly. Each gauge is held in place by two mounting screws that go through the gauge’s back plate. I was originally going to make the back plate out of metal but that would need some type of internal spacer on the gauge’s terminal posts to set the face at the proper depth in the bezel. The terminal posts also have to be electrically insulated from the back plate where they go through it.   To simply things, I decided to 3D print a one piece ABS back plate with built-in spacer. Being ABS it doesn’t need to be insulated from the wire posts either.  Very simple design but it still took me a few iterations to get everything just right.

 

Edited June 15, 2023 by vintage6t

[vintage6t]

Step 4 – Gauge face graphics

I took the gauge face layout created in step 2 and used it to create a paint stencil. Same as my PRND21 project, the stencil was cut on a Cricut machine. Given the size of the numbers and hash marks for the volt gauge this pretty much pushed the limits of the Cricut in terms of the size and precision of the required cuts. Overall it came out acceptable though.

Once I had a stencil, I painted the gauge background using the same tinted clear I used in my PRND21 project. I then used the Cricut stencil to air brush the numbers and hash marks onto the face. The last step was to hand paint over the numbers in phosphorescent paint. The phosphorescent paint makes them glow in the dark when lit, same as the stock gauges.

Overall this came out with acceptable results, not a perfect match with the stock gauges but good enough for my purposes.  If you want to do something similar, hopefully this will give some ideas on how to go about it.

[Sam Buchanan]

Impressive! Great mix of traditional and modern tech.

[Saskwatch]

Well done ! 
 Thank you for posting ?

[Plymouthy Adams]

a cottage industry is born, find these at many select Walmart stores or CVS pharmacies.......?

 

 

[soth122003]

Impressive outside the box engineering and graphics. Looks like it belongs in the dash from the factory. 

 

Joe Lee