I'm looking to turn my recumbent Rans Rocket into an electric-assisted cycle for commuting purposes (extra speed on a stretch of narrow, hilly road, and help getting over a mountain ridge [500' worth of climb in last mile]). It is a short wheelbase recumbent with 2 20" wheels (406mm) with front and rear fairings to further reduce the coefficient of drag.
I want to keep this as simple as possible, so I plan on going with a hub motor. In order to avoid the back EMF penalty when pedaling without boost, I will likely go with a geared hub motor with internal freewheel.
I have been using the simulator at ebikes.ca and would like some feedback on whether people believe it is roughly correct.
The few geared hub motors I seen there are the eZee and MAC Shanghai. With a 20" wheel and 48v battery, the eZee gets up to only 23 mph at around 300 watts and the MAC gets up to 25 mph at the same power level.
Other than the BMC which is priced a little to high for my preference, is there any others that are considered reliable and designed more for speed than torque?
Your ideas are sound..
The kit I'm experienced with is the e-BikeKit (see link towards the top of the page). I have the non-geared motor right now. It's very nice - gives me 22+ miles/hr max on flat ground and no pedaling. Easy to install and works great and their ordering process gives you a lot of flexibility in buying exactly what you need. I'm real happy with it. One real nice thing is it has a three position switch for the handlebar that sets the power range. I keep it in the middle range that gives 18 miles/hr max with modest pedaling. I switch to the high power range when more speed is needed.
I have ordered the geared version - it should be arriving on Monday and I plan to swap the motors to have two bikes with the e-BikeKit.
The geared motor is lighter than the non-geared motor.
- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
I tried an eZee for my hills (much less demand than yours, as described)
and was disappointed with its "guts."
If geared it has to be, I'd go with a MAC 500w from cell_man (check in
with him on Endless-Sphere), since budget is an important consideration.
He'll give you reliable advice about your specifics, and good prices.
I have an ampedbikes 20" hub motor on a recumbent trike. You are correct about speed issues with using a 20" wheel. I discovered this after I bought my motor :(
I have put a diode in the circuit between the motor and the controller, which seems to allow the motor to come close to freewheeling. (Going down a 6% grade, coasting I go 25mph without the diode and 30mph with the diode. You are looking for a motor with lower torque constant. The CLYTE motors seem to have a torque and a speed option. (I have never used them.)
With a 20" wheel, if you want speed you are either going to have to:
a. buy a hub motor and have them change the gearing for you to max rpm
b. buy a dd hub motor that will probably weigh more than 25 pounds
c. install a motor/chain drive on your bent. This is the lightest weight option.