After viewing this page, you might agree it would be more accurate to title it, “Creating a Digital/Analog Speedometer From Scratch“. The only parts I ended up using from the original Stewart-Warner unit are the chrome bezel, glass window, and the metal case.
This somewhat impractical idea turned into quite a long, drawn out sub-project that I nearly gave up on when I came into some extra funds and went ahead and purchased a new electronic speedo unit from Speedway Motors. After fiddling with the imported Speedway unit for nearly a year trying to make it work, and still not having a reliable speedometer with recorded miles that didn’t self-erase, I concluded this purchased unit was going to work for me and my conversion project got dusted off and revived.
A little more background
Back in 1976, when I first assembled this Valkyrie, I installed a nice new Stewart-Warner mechanical speedometer next to a tachometer of matching design, if not manufacturer. They looked great together, but I never got around to getting a long speedometer cable and figuring out how to make the German built ZF transaxle work with the American made Stewart-Warner speedometer. It was one of those details I kept putting off because there were so many more important issues that needed solving. Thirty-five years later, during the second major rebuild, I decided I really needed a working speedometer. I also noticed that electronic speedometers, having been used by OEMs for years in new cars, were becoming popular in the aftermarket. My thinking was, an electronic speedo could pick up pulses from a hall-effect sensor mounted near the output shaft flange of the ZF transaxle and I wouldn’t have to be concerned with adapting long mechanical speedometer cables and figuring out gear ratios, and all that stuff. After seeing how relatively expensive new electronic speedometers were at the time, I got the great idea that I was going to figure out how to convert my existing SW speedo unit to work with a stepper motor. Many years earlier, I had done some programming of microcomputers in the industrial control environment, and this sounded like it could be a fun project, even though I already had other ongoing tasks related the the Valkyrie restoration.
Software:
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