I really don't get the point of this. I mean, if you are on a bike in the city, you generally go fast enough just pedaling, and its not terribly hard on the legs. If you bike for exercise, this thing is moot.

Wait, I get it. Old people who want to bicycle but are weak. But most old people who are able to mount a bicycle can probably pedal along just fine.

Someone explain this to me!

I would want this for several reasons... Say that you have a place that 10 miles away, mostly downhill. Very easy to bike there, difficult to bike back.

Since I live in a relatively rural area, this would be a godsend when my legs get extremely tired and rubbery up a long incline. It would make me bike where I normally drive.

For those of us who are too blind to drive but can see well enough to ride a bike, this device could extend our range tremendously. I will get one when they are made available for my bike.

Would I use this? You bet. I have a 15 mile commute and would like to arrive fresh and not sweaty. Of course I am an old guy. . .

"GreenWheel"? "The cost of being green"? Aren't bicycles green to begin with?

Hehe good point John Clark. I want one of these because when I go on my bike ride on the bike trail I usually go 11-18 miles and sometimes the bike trail has these hills (that they put in intentionally to give you a workout) but I'm so tired that I just can't make it up. This will help.

Also I think it would help me get to the bike trail with no effort on my part then get me back home from the bike trail in 1 piece. Usually by the time I get home from my bike ride 2 hours later I can barely walk, especially if I haven't been riding in awhile so while I'm letting it take me home my legs are resting so I can actually walk to the bathroom instead of using a walker.

This is not ready for prime-time, it is a MIT project and once it makes it to marker (if ever) it will be more expensive then some of the ebikes that are already on the market (Currie's izip and ezip models and also a conversion kit for under $400). The reason are the batteries -- a lithium pack that can take a rider this distance is at least $500 alone plus all the other costs.

Regarding why would anyone want one of these, before knocking it, try one. They are a blast and just think how much more you might use your bike for transportation if you could arrive unperspired! Then there are all of us baby-boomers that would like to ride like we used to but just need a little extra help. They are also just plain FUN!

Electric bikes aren't meant to be 'green' motorcycles, they are meant to make it easier and more efficient to use a bike. They allow you to travel farther (and possibly faster) with a bike, which could mean that more people might use them.

It's clear that this sort of thing won't be cheap and easy to buy for several years but I will be happy when that happens!

I like to buy green wheel but do not know where and how ? thank you in advance for your respond

I'm fat and lazy. I want one. Does it come with a cup holder?

Problems:
1. It probably adds lots of extra weight, due to the hub, motor, batteries and controls.
2. It probably needs a modified frame, to take the extra frame torque, to stop the axle coming off.
3. It probably makes it harder to pedal the wheel, when used as a generator, and messes up the free-wheel.
4. You can't use this drive with a Rohloff gear hub, or any other kind of gear hub.
5. There is probably no hub gearing, so the motor will not be efficient across a range of speeds.
6. Non-standard hub wheels can be expensive, because a new wheel has to be hand built, and for each replacement rim, this can also cause problems when the wheel has to be taken off.

The only snag with a wheel-hub motor is the sophisticated electronics it needs to handle a large range of road-wheel revs.

Whereas by driving the pedal axis, the revs to handle vary within a mere 1 : 2 range a simple direct current motor without electronic torque variator can afford.

Hence my preference goes to a retrofit set comprising a left pedal with an additional chain-ring driven by a frame-mounted electric motor/chain reduction gear/battery assembly -- which moreover would not interfer at all with any existing rear-wheel derailleur or hub gears.

i want one for my daughter who has leg and muscle problems. this would give her some needed exercise without to much difficulty and still be able to keep up with the other kids. where can i find one? i need one as soon as posible. thanks

where can I get one (a greenwheel)

There are already E-motorwheels on the market, you can find them on eBay. The best is Crystallyte. You can also google it. Expect to pay about $400 for a complete kit, including batteries.

A friend of mine recently took a bike trip with his wife through Europe. An ebike allowed her to keep up with him. He got the pace and exercise he wanted and she was thrilled. Seems like a perfect combo to me!

Where can I buy it?

It's a great idea. I could use one to exercise on my way to work yet cruise when I get tired. I would use my bike a whole lot more if it was equipped with a green wheel. Save money on gas too. Excellent!