@knoxie:
"My Bike has a 1000 watts, how can the OptiBike be as fast?
The Optibike is the most efficient electric bike produced - over 75% of the battery power is transferred to the wheel. Many other electric bikes are around 30% efficient. So while the Optibike has 850 watts of power, the other bikes actually have far less."
30% efficient??????? eh where is this BS coming from what electric bikes do you know that are this inefficient? the optibike is surely pretty efficient but why deride the efficiency of other bikes which are a lot cheaper?
here is this crystalite hub-motor simulator: http://www.ebikes.ca/simulator/
try it out..
there are situations were you realy see only 30% efficience !
for example: a crystalite 406, with 24Volt --> its ok for 25-26km/h so street legal in europe
now go up with this a steep hill... lets assume the hill is that steep, that you only manage to go with 7-8km/h
then look at efficience.. it drops from an maxiumum of 78% at 24km/h down to only 30-35%
at the same hill the optibikes motor with proper gearing will be able to spin still in a very good efficient-range and for that will outrun the hub-motor by far..
if you say: silly motor-battery combination (thats how some bikes are sold)
lets take 411 and 48Volts
highest efficience: over 80%... at 200Watt and 33km/h
highest power: at 55% efficience with 430Watt at 18km/h
BUT: you will not manage to go up a steep hill with 18km/h and only 430Watt
so speed will go down further..
at 10km/h the efficience is only at 33%, power also droped to 300Watt
so: here the optibike (or any other "use the gears"-bike) will outperforme the hubmotor at same input power by far
@safe:
The ideal bike would place the battery in the middle of the bike (for better weight balance) use a small lightweight brushless motor (much like the RC motors) and gears. That sounds great, but the "complete package" doesn't exist yet, so we have to simply describe things that aren't being sold yet.
maybe close to that was the old Flyer F-Series:
1.) battery in the center (and easy removable so you can take it with you for charging)
2.) motor in the bottom bracket
and now it comes: the motor was a gearless ! motor, so absolut noisless (because it spins slower than a normal hub-motor in the wheels)
nevertheless you could use the gears of the bike
only downside: this kind of motor was heavy
this here for me looks like a good concept (except of the batteries.. there is a other frame needed to bring the batteries into the center of the bike):
http://www.kraeuterbutter.at/Bilder2/sonstiges/Bilder%20fuer%20Beitraege/Tretkurbelantrieb_mit_Radnabenmotor.jpg
to make the bike light:
maybe the Nano (tonxing) motor could be used, with only 2 kg weight, still geared but not with noisy gears but with quiet rolls for gearing
just look on the picture: with using the gears you can be as fast or even faster then with the same hub-motor mounted in the wheel..
with first gear you have - look on the picture - about 4 times more torque compared to the same motor mounted in the wheel..
imho one of the best ways (torque, speed, still not very loud because slow turning hub)