These two items from gizmag and AutoblogGreen came to my attention recently.
The first, immediately below, from gizmag, introduces a novel system for an electric bicycle that uses both a hub mounted motor and a separate hub mounted battery on the other wheel. This struck me as quite an interesting idea. Having never ridden an electric bicycle of any kind, I can only speak from what I suppose to be the case. With that caveat, I have always thought that the battery pack on any electric bicycle I have seen heretofore was mounted much too high for stability. It seemed to me they were all mounted up on the top frame tube or on the down tube coming down from the fork bearing tube. Of necessity, they had to be high so not to interfere with the riders legs when pedaling. Having the battery mounted in the hub would seem to me to make for a lower center of gravity and, thus, a more stable bike. Having the probable weight distribution close to 50/50 would have to make for a better handling bike, too.
Even though it’s dated earlier, the second item, from AutoblogGreen, initially fascinated me, as it combines motor, battery, control system, and charger in one hub. It also adds a Bluetooth wireless throttle control, too. Talk about state of the art, this concept has all the bells and whistles. Then I started really analyzing it and I kind of lost my initial enthusiasm. I can’t help but think that all that weight biased to one end or the other would negatively affect handling. I also can’t see how they are going to get a big enough battery in that hub to deliver the performance they claim. I suppose the bluetooth solves the problem of wiring a control on the handlebar to the wheel, but I can’t help but think it’s overkill. It appears to me to be a solution in search of a problem.
Sources: http://www.gizmag.com/e-electric-bicycle-electric-motion/11059/ and http://www.autobloggreen.com/2009/02/19/mit-greenwheel-simply-an-electric-bicycle-revolution/
February 23, 2009 With the increasing popularity of the electrically assisted pushbike we are starting to see some innovative designs hit the market. While hub motors are the number one solution for mounting the electric motor within a bike frame, either in the front or rear wheel, mounting the battery pack and motor drive electronics has remained a challenge when taking into consideration practically and aesthetics. The folks at Electric Motion Systems think they have the answer with a combination of a 750 watt rear wheel mounted hub motor with built-in motor drive electronics paired with a battery pack mounted in the front wheel hub.
e-electric bicycle
The E+ Electric Bike is available in six styles of bike that are all a variation on a hard-tail mountain bike. The E+ comes standard with a 750 watt BLDC rear hub motor but there is a high torque 85 Nm 1kw hub motor as an upgrade option. Both hub motors have built in inverters so there’s one less box to find mounting space on the bike frame for. The front hub mounted battery pack is something we’ve never seen before on an e-bike. The internal layout is very similar to a hub motor with the stationary inner structure (called the stator) attached to the axle while the outer housing is attached to the rim via spokes and rotates as part of the wheel. Thirty NiMH battery cells are arranged in six groups of five cells arranged in a polygon layout parallel to the axle and mounted on the stator. The battery pack puts out 36 volts at 9 amp hour giving a battery capacity of 324 watt hour. (0.324kw/hr). No electric only range is quoted as this is very dependent on terrain, how much you pedal and the amount of regeneration possible but each battery charge should give between 20 and 40 miles (32 – 64 km). A full charge from a 110v wall socket will take four to six hours and cost about $0.03.
The E+ has a handlbar mounted LCD display where the rider can select 19 different cycling modes that range from full electric to pedal only modes. One of the E+ modes offers to let you set the cycling mode for increased resistance to give you a greater workout even if there are no hills in sight. While this could well be a useful feature, it also highlights one of the side effects of BLDC hub motors - they do not freewheel. Because a BLDC hub motor contains permanent magnets even when no power is applied there is still magnetic attraction between the magnets and the poles on the stator meaning there is always cogging resistance. The company says this should only be a problem with a flat battery on extended flat surface riding, as with any kind of undulation the motor will regenerate on the down hills just enough to provide power assistance up the next hill.
The LCD-display also shows speed, distance traveled, battery capacity, cruise control option, and 19 cycling modes. It also displays trip-specific data such as distance of trip, duration, and average speeds. Pocket-sized and removable for safe and easy storage, when the display is removed, the battery is disabled and the motor is put into full resistance mode, making pedaling virtually impossible. This unit has backlighting (0-100%) and automatically adjusts the contrast of display depending on outdoor conditions.
The Electric Motion Systems E+ Cruiser and E+ Mountain Bike cost USD$3,495.
One definition of the word elegant is “to be gracefully concise and simple.” In the future, the dictionary just might include the GreenWheel as a product that illustrates this principle perfectly. From the MIT Smartcities team that gave us the stackable cars concept and the RoboScooter (still a go), comes a wheel that can turn an ordinary bicycle into a very desirable electric one in an easy, cost effective manner. Enclosing a motor, A123 Systems batteries and a generator into a small aluminum pancake hub, the GreenWheel can give you up to 25 miles of propulsion, or much more if you don’t mind pedaling. Unlike conversions kits from the past, it forgoes running wires the length of your bike by incorporating the magic of bluetooth to control the twist-throttle.
Over a dozen different configurations of the GreenWheel are scheduled to be tried and tested by a variety of cyclists this spring. Once the the team analyzes their feedback, an ultimate configuration of power, speed and cost will be settled on and mass production will get under way. With an estimated cost of “several hundred dollars,” they better plan on making a lot of them since not only are they a wonderful “solution” for several cities and ridesharing programs already showing interest, but in a world-economy that can’t afford to buy cars the way they used to, the GreenWheel should have a bright future.
[Source: MSNBC]
