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MB-1-E Part Nineteen: Synchronous Belt Drive
Submitted by MB-1-E on Sat, 07/07/2007 - 23:42
I spent the day at Kent's machine shop. Kent has been a friend of the family over the last 50 years or so. He's not only a very interesting person but has,by far, the most interesting machine shop you could possibly imagine.
As I worked on trying to figure out what was wrong with a 1250W inverter that had recently died (Kent lives off grid and has another shop at home, which uses the inverter), he bored my two grooved pulleys so they would fit the 5/8" motor shaft and the 5/8" jack shaft on the MB-1-E.
Per Chuck's suggestion, a hole was drilled off center for the key way before boring. I filed the top two edges of the key to accommodate the rounded key way and the pulley went snuggly onto the shaft. The larger grooved pulley had a large boss with setscrews, so no key way was necessary on this one.
I put the toothed, synchronous belt over the pulleys and low and behold it was the perfect length.
I made a belt adjustment then re-tensioned the chain adjustment and gave the bike a try.
Now I previously had two V-belt pulleys that made my ratio a 12:1.
The new toothed belt made the overall ratio 9.22:1.
I expected the bike to be a bit sluggish in comparison and perhaps slightly faster at top end.
I'm not sure whether the toothed belt is just so much less friction than the V-belt or that the positive connection via the pulley grooves made the difference, but I was pleasantly surprised the the bike was very peppy and about 5 mph faster than before.
The bike seems to pull hills about the same as it did with the 12:1 ratio and now tops out at 24-25 mph.
The new belt and pulleys look nice on the bike. I'll get some pics in the next day or three to show you.
Anyway, it was a fun day and we both got some riding in on the MB-1-E. Kent went down a very steep street then stopped at the bottom, started out and was going 18 mph by the time he got to the top. I went up and down some horse trails and hilly terrain and we both were terrorizing the neighborhood zooming around on the bike.
I'm very surprised at the difference. I may never go back the the V-belt again.
Until we meet again ...