Wiper Conversion: How To convert vacuum to electric with opposable wipers

I think I finally have a solution for converting my 57 Scotsman wagon from vacuum wipers to a 12V electric system. I've seen a lot of post on wiper conversion, so I though I would take some pictures and show you how I did it, and maybe get some critique on my first attempt. I have a state inspection hopefully in the next week, so I just needed to get something working fairly quick.

The hardest part is doing this was absolutely the wiper linkages. On a system where both wipers rotate in the same direction, I assume this would be an easy task. However, on this car and other Champions the wipers are opposable, they travel in opposite directions. The driver side pivots from the bottom left, the passenger pivots from the bottom right. To get them to raise you need to push out on both linkages, and to get them to lower you need to pull both linkages torwards the center.

So what I did.. 1) I took out the old vacuum motor and mounting plate.

2) I bought a cheap 12v electric motor (I think it came off a Chrysler, it was a good fit, though not perfect) https://www.amazon.com/Cardone-40-387...cardone+40-387. (I also pulled a standard 4 connector wiper connector off a random car at a salvage yard to help with wiring later)

3) Most wiper motors have a 3-bolt system to mount it. I just drilled 3 holes into the firewall where the old vacuum motor was and mounted it there. 4) The electric motor arm is usually keyed by a rectangle. I bought some aluminum and made myself a small strip with a notch in the center that fit the key on the motor. This locked the aluminum strip to rotate with the motor.

5) About 1 1/2" away from the key hole in the aluminum strip I drilled another hole, enough for a 1/4" bolt to go through. *This is a key adjustment, a 1 1/2" distance will pull/push a wiper arm 3" when the motor makes a full revolution.

6) On a second aluminum strip, I drilled two 1/4" holes about 3" apart.

7) I took a long 1/4" bolt (about 2", enough for some clearance), and bolted one end tight to the first aluminum strip, then I added some spacers & washers, then the left wiper linkage arm, then more spaces & washers. At the other end of the bolt, I attached the 2nd aluminum strip, so it turns with the full assembly.

8) I attached the 2nd wiper arm to the second plate through the remaining hole.

I'll worry about the electrics tomorrow, but it seems to work. Hope this helps someone.
-David

Rigorous proof of concept