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Friday, November 30, 2007

I can't believe it actually WORKED!

A new version of this kludged together electric bike actually WORKED today! Of course, an important part of it came apart less than a mile into the ride, but it WORKED! And of course I could still pedal the rest of the way, after tying the broken bits out of the way. :)

And I had started over again from scratch, too, so it was something I did and thought of in less than a day. Probably about six hours of work, maybe seven. I guess it's not bad for what would essentially still be an alpha-test version of it, certainly not ready for extended use. I guess this one is version 1.2.0. :-)

Remember that non-working electric scooter which had a burned out controller and a bad-smelling motor that read as a direct short circuit? I'd presumed the motor had gotten too hot, melted the enamel on the windings, and shorted out, blowing the controller in the process. Actually, the only part that melted was the power leads just inside the motor, because the Chinese factory that made it used regular low-temp thin-insulation wiring, which they very tightly zip-tied together just inside the opening, so when the motor got hot for whatever reason (too heavy a load? I'll never know, it happened before I got it), the wires' insulation melted together (red and black make a wierd color when mixed), and of course that let the power leads inside the motor touch, which makes a dead short. That's what blew the controller out.

It took only a bit of work with some tubing and some teflon shims (courtesy of the leftover ends of my old Slime Tire Liners) between the wires at the entrance, and a little silicone around them and all the seams of the motor casing before putting it together again, and now I have a "250 Watt" water-resistant motor that actually works. It's fairly quiet, though definitely wasting energy via noise/friction (probably in the brushes). I don't really get how they rate it as 250 Watt, given that it is also marked as 24 Volts DC @ 14 Amps (168 Watts), but it might mean that it *could* dissipate up to 250 under it's heaviest load. I haven't actually tested it's no-load current or it's full-load current.

The actual part that broke was of course the hastily-JBWelded-on sprocket for the motor chain. I'd had no other choice with the materials available to me, because the hole in the sprocket for mounting is actually larger in diameter than the entire rear axle, including spoke mounting ring! So I carefully centered it on the rear wheel's left side after applying as much JBWeld as I could get to stay on it there (obviously not enough), to hold it to the spokes themselves and the very rim of the spoke mounting ring, which is all that would reach the sprocket--there's about a 2mm gap between the ring and the inside edge of the mounting hole for the sprocket.

I'd wanted to use the actual mounting ring and coasting ratchet from the scooter's rear wheel, but there's no way for me to get it off of there without damaging it, since I don't have the special tools it requires to take it off--it's different from any of the bike versions of the same thing, and doesn't go on the same way. If I could, I'd just drill out the bearings in the middle of it that the scooter wheel axle would rest on, since I don't need them for my purpose, but I have no drill press, and that's what it would take to do it and still leave the ratchet intact. actually sells the mounting ring with ratchet separately, but I am trying not to spend any money that I don't have to, partly because I don't *have* enough even for rent/bills past the holidays, and partly because I simply want to make this bike project a continuing symbol of recycling usable bits of otherwise broken things no one else wants (especially things others threw away!).

Tonite it was pouring rain on my way home from work, including a second trip out to go to the store for essentials, so I'm drying out now, and warming up, and will probably try working out a way to get that ring off the scooter wheel later tonite or tomorrow. If I can't, it's time for lots more JBWeld. ;-)

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