Home made electric bike design

A

andrewjb101

New Member
Hey guys,

I'm really new to all of this. I was planning on putting an old lawnmower engine (2 stroke, 1HP) onto my bicycle, but after a few discussions we decided it's not powerful enough to get up a hill and be self sufficient. Also it's illegal on the roads in the UK. I'm going to build my own electric design using some custom components.

I'd like to use this electric motor instead:

http://www.hobbyking.com/hobbyking/..._Brushless_Outrunner_Motor_UK_Warehouse_.html

I need to make sure that I can get the right battery and it will go more than 10 miles on full power. I'd also like to work out its maximum speed and gear ratios, does anyone know how to do that?

As I said, I'm quite new to all of this and I'd appreciate the help!

drn2
 
I looked at those motors and they sure are enticing but cost has kept me from being able to use them for the reasons above, with high current demands comes the need for tremendous battery capacity. My 8 hp bike only has a range of about 5-6 miles before it hits LVC.
 
That motor was designed for aircraft applications, to drive a large propeller.

In addition to providing thrust the prop also forces a large amount of air over the motor. Without the forced air cooling the motor will burn out very quickly and be nothing but a smoking piece of junk.
 
Using an RC electric motor is reasonable. There are ways to fan cool air across the motor. E-bikes powered by Turnigy motors are not rare. I think the 8kw rating of the motor in your post is not so reasonable. It can suck a good LiPo battery pack dry in minutes. If you want decent range without spending over $1000 on batteries, get a motor that draws less power. The average electric assist motor kit in the US is probably 36v 500w. Smaller, 24v motors are gaining popularity, due to greater range.
Picking all the components yourself is fun, but you need to be sure that they will meet your needs and work together.
 
Why not use a Golden Motor kit that was designed for bikes, does not need a transmission or cooling, makes no noise and comes complete at 1 KW and costs a grand with the battery?

Also proven to plow thru snow and salt in Maine with zero maintainence.
 
I agree that an 8000watt motor is excessive if you have to spend a fortune on batteries that will last less than 10 minutes.
Those DIY kits look fun, but are the components good quality? How do you pick the battery, e.g. how do you work out the run time of the motor with each batter?
I'm looking at Golden Motor kits and Sick Bike Parts as suggested, and one of them definitely ships to the UK.

The idea of picking the parts yourself always appeals to me as you know what's going into it and where the bottle necks are etc. I quite like fabricating which is half the project for me. Has anyone custom picked their components?
 
Another thing to consider is that with some careful consideration you can quadruple the output of an electric motor by your setup. Look up over-volting.
 
I would go with a kit.
Rear drive hub or chain drive wheel like currietech.com
I would watch the higher voltage motor systems due to UK regs on speed.
I think you _must_ have a pedal sensor and can't do what currie calls tag twist-and-go
My "450w" chain drive motor will pull any hill you want at about 12mph and top speed
of just under 20mph (too fast for eu).
btw, with that LiFEpo4 pack I see 35ampres and that equates to around 800w.
 
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