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sinbad said:
Have any of you ever put an electric motor on a bike? I have an old steel frame Trek bike that I was thinking of putting a motor on. Do you have an opinion about what motor would be best? My bike has 700cm wheels, which I guess might pose a problem. Thanks for your opinions.
I used to be the lead engineer at Charger Electric Bikes, so I guess I've done this a time or two.

If you are in decent shape you probably won't get much benefit out of putting the motor on the bike. The extra weight of the motor and batteries will slow you down almost as much as the extra power will speed you up. You could probably see a 2-5mph increase in speed if you gear your setup correctly.

If you are looking for a moped, then there is some logic in putting on the electric motor. Nothing like being able to cruise with your thumb on the throttle.

My favorite retrofit kits were the 24V Currie Technology kits. They bolt on the back wheel. They look a bit funny, but they work really well. Unfortunately, they don't make them any more, but you can find used ones on eBay.

Good luck!

- Forbes Bagagtelle-Black
 

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undies said:
Frankly I don't get it; our town is flat and not very big. If one wants to experience the thrill of self-propelled two-wheeled travel there are these new contraptions called motorcycles that you can get now. Just a thought :confused:
Motorcycle = 180 (or less) hp, fossil-fuel-burning smog-spewing death machine which requires a driver's license. Cost is up to $30,000 or so.

Electric biycle = ~400W, clean-running, energy efficient machine which can be ridden by anyone 16+ with or without a driver's license. They are (relatively) safe unless you drive them like a maniac. You can get a lot of excersize on them, so they have potential health benefits. Great for people who want to get excersize while they commute, but aren't fit enough to do it on leg muscles alone, such as the elderly and handicapped segment of the population. Cost is less than $1000.

So, there are real reasons why electric bicycles make sense. These reasons are why they are selling millions of them in China, where bicycles are viewed primarily as commuter vehicles rather than excersize toys.

Yours,

FBB
 

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Dave_Stohler said:
FWIW, road bikes are the most efficient machine known to man.
Almost correct. They are the most efficient vehicle yet invented (That I know of, anyway).

Dave_Stohler said:
Electric motors are, at best, only about 40% efficient.
Incorrect. Electric motors can have efficiencies in the high 90's, percentage-wise. Even a standard, off-the-shelf NEMA B motor can have efficiencies in the 90's. See:

http://www.engineeringtoolbox.com/electrical-motor-efficiency-d_655.html

Internal combustion engines top out in the 45% range, or thereabouts.

- FBB
 

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undies said:
You should get out more
Ouch! HEY! It's been raining, okay?! And I've really turned into a Californian over the last few years - a little bit of drizzle and I stay indoors playing computer games. I was going to go on a killer ride tomorrow, with ~4-6K feet of climbing, but there is a storm moving in, so I guess it's a big breakfast and then I'll finish conquering Northern Europe. If it clears up in the afternoon, I'll get out and go for a ride.

And I'll continue to like e-bikes even if they're not cool.

Yours,

FBB
 
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