Electric Bikes - Ebike without drag?
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I currently ride my car to university, and for my work ( drive for a living 3 hrs a week ). Im thinking on nice days I can get away with biking most of this distance myself, but not at a high speed and I got a fair ways to go (12 km each way for school). I want to be able to get a system that has NO drag when not in use though. I know brushless motors are better than brushed from my r/c cars even for drag, but I have searched and read here that there is still resistance. I havent bought a bike yet either, so is WEIGHT or lower center of gravity to reduce air drag more important? Any bike ideas? I would very greatly appreciate any advice. Normally id have no problem doing this without e assist but ive been sick the last year and my cardio suffered big time and I still having a hard time getting it back.
In terms of air drag, adding an electric motor+batteries to a bike makes almost zero diffrerence. Lower center of gravity will not reduce air drag. High center of gravity will make a bike handle somewhat differently. If your bike has high center of gravity and all of the extra weight is on the rear, it is likely you will not like the handling (although I personally don't mind having a lot of weight up high in the rear).
If you want zero drag, get a "geared hubmotor" or a motor system that is not built in to the hub (the walmart/schwinn E-zip and the cyclone-tw.com kits, for example)... because all of these have a freewheel so that the motor doesn't have to turn while the bike is moving.
I put a lightweight motor+battery on my bike for a total e-bike weight of 45 or 50 pounds and the bike is very rideable without the electric power. It is noticeably harder uphill due to the extra weight though. That will be even more true if you go with a 75+ pound e-bike (Lead Acid batteries or big hubmotors will make your bike heavy.)
Thanks for replying!
I didnt mean lower center of gravity in terms of the balance, but rather lower handlebars, lower seat, smaller frame, = less wind resistance due to less area of displaced air. I am wondering if weight or aerodynamics is more important in choosing a bike and kit. Also I looked at the cyclone kit you sent the link too, and that seems like a good kit and the freewheeling is nice, however the distance per aH of battery seems to be lower than some of the other kits such as the Wilderness.
Im guessing you have a brushless front hub motor, and your saying with ZERO throttle you dont notice any increased drag from the motor's magnets? Thank you!
I dont need to go fast, I just want light pedalling + motor and around 30-35 km/h for 25 km.
I have a cyclone kit. One that doesn't work, due to an as-yet-undiagnosed electronics problem. Cyclone has some reliability issues, as do some of the other makers. The most popular kits that I know of (crystalyte, wilderness energy) sound like they are more reliable than cyclone.
In my experience, air drag is the most important efficiency consideration when you have a kit as powerful and fast as my cyclone 500W kit. If you will spend most of your riding time at speeds of 20mph and down, weight may be more important. (but with pedaling plus a 360w or 500w cyclone motor, don't expect to be going under 20mph very often.) If you are willing to pedal, don't set your bike up to be uncomfortable to pedal, because pedaling increases range a lot. The best improvement I think I could make to my bike if the motor were working would be to put aero bars (http://www.cruciblefitness.com/etips/RichFit.htm) on, although they'd look funny with my MTB tires and wheels.
Cyclone kits have about the same range per usable watt hour as brushless hub motors. (range per watt hour is what's important, not range per amp hour.... watt hours are amphours times volts... for SLA batteries usable watt hours are somewhere around 0.5 times rated watt hours) Manufacturer claims about range and efficiency for e-bikes tend to be somewhat misleading.
So if you had to do it over again would you have gotten a hub motor? Thats alot of money to have electrical problems on a pretty simple design. :-S
I would probably get a hub kit, yeah. Or the cheap walmart e-bike.
I don't need a motor to get to my new job (4 miles from home, i ride my other bike) but it's irritating that the thing doesn't just work and stay working.
The awesome thing about the cyclone kit is that since it uses your rear derailer gears, it has awesome torque on the uphills and awesome speed on the flats... when it works.
Ok so your saying if im looking for a kit and I need it to be VERY reliable, steer away from the Cyclone kit? Can you please point me in the direction of one that would do 20mph for 20 miles unassisted? ( so once I pedal it should do 35 km/h for at least my trip to university and back )
06-07-08, 04:27 PM
I thought about getting a rear e-hub breifly, but I like a front one because instead of power to only one wheel (rear e-hub) I can use my pedal assit to the rear wheel so I get power to both front and rear wheels at the same time (AWD).
32kph (20mph) for 20 miles, unassisted, you'll need maybe 350 rated watt hours of nickel or lithium based batteries, 600+ rated watt hours for lead. A 200W motor will not be enough, and a 500W motor will be enough. People who buy the wilderness energy or crystalyte motors seem to like them; same for BionX. If you're on a budget and you don't buy a cyclone kit, you might want to go ahead and buy a gearless hubmotor (which is what most hubmotors are) despite the drag.
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