Low power - Low weight - Low assist

[spike]

Thanks. I'll take a look...

Yes, they will build any size wheel. As you say, it's a bit expensive. The original quote for 2 kits was over $700!

Another dealer to look at for the Tongxin lookalike is Robert at trade@e-bicycles.eu.

 

[spike]

OK. I got the Tongxin kit after a long delay due to using the cheapest shipping option. I've attached a scaled down jpg of the invoice if anyone is interested. There were a few problems with the kit and Diana was willing to send a replacement, but after a bit of tweaking it's working OK now. The wheel build is pretty good and the hub a almost silent. The ordering process was very slow but polite and helpful. I'd be happy to buy from OutRider again based on the experience so far.

HTH

Spike

 

[pictsidhe]

All that is possible at the moment, Mr Bond

Power at the road = speed (m/s) x thrust (N)
0.45m/s = 1mph, 1N is about 0.1kg

Motors produce torque in proportion to current, this holds up pretty well in reality, 5A will give much the same torque at 5mph as at 15mph.
Speed is proportional to voltage, this gets a bit mangled by the motor resistance and current sucking volts away at high current (torque),
V=IR, eg: 1ohm motor and cable resistance, 10A current; 1 x 10 = 10V lost to heat the windings.
What you want to get up hills is torque, power depends on the speed and torque, if you want assistance at 30mph, your best bet is to overvolt, a 36V motor on a 72V battery would run to 30mph, think of a realistic limit. Some motors may disintegrate at high revs, this will be suck it and see. It is current that will fry windings and strip gears, other people may have found that point out on a given motor for you though. Your different modes can be obtained with a custom controller, off the shelf ones may lose the plot at high revs too, I'd be tempted to just use a twist grip, power meter and the cruise control between my ears though An A123 72V 2.3Ah battery pack would weigh about 1.6kg, at 50W and 75% overall efficiency, it would last 2 1/2 hours, you'll probably find running at 100W+ a LOT more tempting though.

 

[jbond]

There's a way of doing this with a CA. Set the CA to a current limit (variable pot or a switch with a resistor ladder) then have the CA clamp the throttle or over-ride the throttle and control the throttle voltage directly. The catch is to come up with a plan for power on-off. I thought using the pedelec would be a good way but common (infineon) style controllers treat the pedelec as a throttle over-ride. When the pedelec is active it effectively ignores the throttle.

I'm thinking perhaps a latching push-button with a brake override.

I believe somebody has come up with a circuit to do the same current limit by over-riding the throttle which would probably be a lot cheaper than a full CA. This appears to be what Storck have done. They have what looks like a thumb throttle, but actually it's a variable assist control working via limiting the current.

As you say, you can do all this manually. The catch is that the manual methods encourage you to use the power, and the way to get range is *not* to use the assist and put more physical effort in.