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Old 03-16-10, 02:03 AM   #1
aum108
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Join Date: Mar 2010
Location: New Zealand
Bikes: crappy dual-suspension mountain bike I'll be trading in for something better
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Newbie needs suggestions

Hi,

I'm a total newcomer to eBikes, but the concept has grabbed me hard. The itch won't ease up until I scratch it!

I'm looking to add electric assist to my humble mountain bike, along the lines of:
this DIY projectl.
What appeals to me about this approach is its low cost, relative simplicity, coherent electronic design, and especially the regenerative braking feature.

However, please note that I'm virtually a complete mechanical newbie. With bikes, I'm a complete non-technical user, and haven't even removed the rear wheel to patch the tyre. My technical expertise is with electronics, microcontroller design and software development (which I'll be calling on when I design the controller).

So I'm writing here in the hope that you good folks here can offer some advice, and explain things at a fairly basic level.

With this project, I'm seeing a few dilemmas such as:
  • Coupling the motor to the wheel - chain drive, or roller against tyre? Pros and cons? The article linked above uses the roller against tyre method.
  • Best place to source the motor really cheap? I'm in New Zealand where motors (and just about everything) are expensive. Can anyone suggest a cheap creative source?
  • Should I couple the motor to the front wheel or the rear wheel? An advantage of front wheel is better weight distribution, but at what cost?
Also - if I want to use the chain drive option - what parts do I need to rig up a non-freewheeling sprocket to the front or rear wheel? (I don't want freewheeling, since I want to pursue the regenerative braking option, and I'll be looking for a motor with electric clutch which itself will be able to freewheel)

As for batteries, I'm looking at SLAs (as per the article), mounted in the centre frame.

For the controller, I'm thinking of creating a microcontroller-based design, involving variable PWM, and a bidirectional twist throttle - allowing for variable power assist, as well as variable amount of regenerative braking. Perhaps even a strain gauge or potentiometer attached to the brake caliper, to allow variable regenerative braking with small pulls on the brake lever, and standard friction braking with harder pulls.

A finishing touch would be to add some solar panels allowing for recharge of the SLA while bike is parked (and, to an extent, while bike is in motion).

So what are people's thoughts on this, especially with the mechanical issues? Have I picked a year of nightmares, or can you point me to some simple ways through?

All help gratefully appreciated.

Cheers
Dave
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