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07-12-08, 08:50 PM
I just bought a IPS (independent Pedaling System) stoker crank made for tandem bikes to allow the stoker and captain to freewheel so they don't always have to be in cadence. It allows the pedal crank to freewheel and has an extra gear that will allow me to run a chain from a motor to power the cranks on my Xtracycle. The cranks don't turn when the motor is powering the bike but the motor will be in line so when I am in low gear the motor will be in low gear and I can go up these hills easier. Now for the motor. I could use a hub motor like Stokemonkey does, the advantage to that is they are narrower than the other two motors I have here. (electroportal and ecospeed). Any suggestions?
07-12-08, 09:20 PM
Well, i'm not 100% on this, but I believe Stokemonkey was a Crystalyte. At any rate, it used a larger brushless direct drive hub motor. Getting a direct drive motor like a crystalyte would be quite quiet, but heavy - I think that Stokemonkey used a 5-series motor in particular, which would've weighed in excess of 20+lbs! The larger Crystalyte motors like the 5-series are also very energy intensive. As a benefit though, they're quite powerful, you would have no problems finding that the power is probably excessive for the need (vroomvroom)
Personally, I find that my 408 (a smaller Crystalyte) is just fine as a hub motor @ 48v for Xtracycle use, so it would probably be more than adequate run through a drivetrain ala stokemonkey style. You can get Crystalyte 4-series hubs at ebikes.ca as a "project motor" which is basically just the motor on an unfinished axle, sans wheel - perfect for your project if you're able to find someone to machine the axle to your needs or do it yourself.
Pound for pound, motors which run gear reduction like your ecospeed provide the most power by quite a bit. Some are available as a hub motor though, like the BMC - and conveniently enough, the BMC is also available sans wheel, and is quite light (I think they're 8-9lbs, opposed to Crystalyte's 15) with an excellent torque output. It would also be a good one to look into, for sure! They do output a bit more noise than the direct drive hub motors though (which I believe is the reason that the creator of stokemonkey chose direct drive)
So, my two cents are to look at the project motors at ebikes.ca and possibly see if you can find a source for a BMC motor as well! Either of those would probably be nice choices.
07-13-08, 11:29 PM
This guy had the same kind of idea, only problem, you need a reverse freewheel, or a regular freewheel, reversed, with some way to keep it from unthreading.