Shanghai Scrambler

I think the best would be a 24" rim but you may have to notck the stays for clearance, Simple is to use 3/16" flat weld in for extension, and just bend the stays out, to clear the shieve kind of like this.
1765041754663.png
 
Thanks for the tip, Curt, but my frame is aluminum so I'm hoping the stretch I did with the scissor jack will clear. And the 20" rim might make the gearing a little high, but I don't have a 24. Here's the first mockup to make my marks for the fender washers. The 2.50 tire is too wide, will drop down to a 2.0.

sheave mockup.jpeg
 
I think I have a 24" I could ship you. yours should work, a Wizzer shieve is 16". Probably need a jack shaft to get the gearing right, best drive it with a serpintine pulley as the 5/6 grove is the same as 5/6 pulleys. be a lot les slipage, I got one free frome a alternator rebuild shop.........Curt
 
I could be mistaken, Curt, but it seems my old Whizzer sheave was 15" which would give my 20" rim a 25% advantage. The friction drive gearing was way too low, so I might be able to slide by without a jackshaft. What was the diameter of the serpentine pulley you got from the alternator? I might be able to fabricate a serpentine-size pulley from my friction drive spindle.
 
Ya, you may be right, but close. I don't remember the rims size of the 20" rims either with the tire off. I measured my pulley it is 23/4", but they had a box full and very in size, with either 5 or 6 grove, I took a 6 grove as it would give less slipage maybe. Find a electrical/machinal shop and see what they have. The hole size is bigger than 5/8, so I had to turn some shim stock, and weld it right to the 5/8 shaft. Keep in mind that friction drive turned into belt is turning backwards, so you have to turn the motor around also..........Curt
 
You make a good point so I measured and the 20" rim is actually 16" in the groove with an outside diameter of 17", not that different from a Whizzer. If I can come up with a 1" drive pulley, the 16:1 ratio might work. If that's too high for takeoff, I'll add a simple jackshaft. I live in the sticks so repair shops with spare parts are few and far between.
 
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