How does this electric assist work? Where is the battery? In the bag on the rack? Isn't it heavy reducing somewhat the gains from extra power?
Sorry for the late reply. The battery pack is located in the army surplus bag(thats mine, its not the stock bag), on the rear rack. You can basically use anything(topeak bags and rack, duct tape, empty plastic containers, anuything) where the battery will fit. The motor already comes mounted on the rim, and you just install that on your front fork. Install the throttle, wire the whole thing up(connect the motor to the controller, and the controller to the battery pack) and you're ready to go(the batteries already come pre-wired in my case).
The kit works like this: You have to pedal first to activate the motor, to about 3-5 mph. you can stop pedalling if you choose to do so, but the system works better in conjunction with human power. Variable speed via the throttle. Can go about 18 mph assisted, more or less. Range with the battery that I have(three 12V/12 amp per hour sealed lead acids) which is about 30 lbs is about 25 or so miles with moderate pedalling. I can climb hills up to about 9% grade for at least half a mile continously, and the motor doesnt feel hot to the touch at all(motor temperature is one of the limiting factors of efficiency and range).
You can always spend more money on lighter battery technology. NiMh of the same energy capacity weighs about 15lbs but can cost about $300(lead acids cost about $100-120). I've seen systems that can go 40 miles using lighter niMh and Im planning on using them once my lead acids die out in about 10 months of regular use or so.
The whole system is deffinitely not light(especially if you're using lead acids, like I do), so acceleration suffers from a dead stop(you can always buy systems that starts from a dead stop without pedalling, unlike mine). The motor is more than efficient to handle the extra load of the system itself. At cruising speeds on flat ground , you won't even notice a difference and you can turn the motor off and pedal instead, riding on the momentum. You will deffinitely notice the big difference when climbing hills(much, much easier), and I almost always run out of gears on my mtb style comfort bike at full speed(flat ground). Time to shop fot a better crankset and gears for me. My whole system weighs in at about 75 or so lbs., including the bike. The kit weighs in at 45 lbs(30 lbs battery and 15 lbs front hub motor), so thats comparable to a fully loaded touring bike. But again, you have a motor, they don't. Use it.
Electric assist is probably not for everyone, especially weight weenies, but it addresses many reasons people give out when asked "why don't you use your bicycle for errands/commuting/etc", like hills(San Francisco...San Diego...), sweating, headwinds and well, it's just damn hard!
Okay, I have typed in alot of words and I'll stop because I'm getting hungry. Time for dinner! Hope all that diatribe helped you understand electric assist much better!