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What do front hub motors weigh??

V

vanilla ice

Guest
Hi, I'm a new user here who has no electric bicycle experience. Nor do I have any powered bicycle experience. What do front hub motors weigh?

Reason I ask, I am thinking of adding a front hub motor to an off-road motorcycle, basically for the traction advantage in sand and mud, not for any addition acceleration. If the weight destroys the front suspension characteristics, I will stop before I start- thus the request for your input.

Would a necessary 60 to 70mph top speed compromise low speed torque? Assuming the use of a large generator can I get away with just using light weight stiffening caps instead of batteries? Or are batteries a better choice? Any ideas or thoughts on this are appreciated.
 


azbill

Active Member
Joined
Dec 15, 2006
Messages
3,721
front hub motors are not recommended for suspension forks, due to their torquing in the dropouts
 
V

vanilla ice

Guest
Torquing in the dropouts? What does that mean?

Motorcycle forks are pretty beefy and they usually have several bracket holes on each side for brake calipers. I can probably figure an arrangement out to connect those to prevent spinning the hub. The forces those fork take offs have to endure for stoppies and high speed stops are much more than even a ~1000w motor can put out I think. But if it turns out this is a legitimate concern so be it.

Yamaha and a couple after market companies have developed two wheel drive motorcycles, and from reviews there are many benefits to 2wd. But they use chain drive or hydraulic drive. I think these types of systems are too complicated for my diy abilities. All the commercial offerings of 2wd are very expensive as well. So here I am investigating on this forum.

I think I would need a little 0-5v TPS pot fed off of the carburetor linkage to automatically adjust throttle setting to match the rear wheel.

Another concern is durability. Are these motors strong enough to deal with hard landing from large jumps? I think weight and durability are going to be the big things.
 
S

StreetPlanes

Guest
I really don't think any of the bicycle hub motors are strong enough for motorcycles as they only use 14mm axles and if there are any electric motorcycle hubs on the market I'd love to see them as I've never seen any.

Now if you were talking Mountain Bikes the Wilderness Systems and others will probably do the trick.
 
V

vanilla ice

Guest
Torquing and power should be non-issues. I will be retaining the infernal combustion engine to power the rear wheel. I'm not looking for super duper acceleration here, I'm looking for an *aid* in traction for sand, mud or other adverse terrain. Its easy to "wash out" your front end in these conditions.

2wd motorcycles are not new. As I said Yamaha and a few others have built these successfully and the reviews are positive. These systems typically transfer 5 to 15 percent of the power to the front. That small amount is enough to change the characteristics of the handling. However hydraulic and shaft/chain systems are over my head, so I thought electric might work also while being simpler.

So does anybody know how much these things weigh?
 
V

vax

Guest
I was playing with idea of 2WD electric bike, using hub motors. I even contacted Crystalite for prices, but dropped the idea because of money shortage...
 
V

vanilla ice

Guest
Well this would be a hybrid I guess. The rear wheel powered directly from the gas motor and the front electric motor powered indirectly from the gas motor.
 
V

vanilla ice

Guest
Thank you, I'm still finding my way around the electric vehicle part of the interweb. I followed some links that suggested similar weights. Maybe I will need to go with one of the lighter lower powered hubs. I'm guessing I will need a fairly beefy generator and dc to dc converter if I want to get away without heavy batts.

I'll take a step back and re-evaluate this idea. I'm not sure if a lighter lowered powered approach will have the desired effect. Could be only half a horse power is enough to overcome the drag of the front tire through those turns in sand.
 
R

RLK

Guest
*Tangent*

I've taken a couple of lessons from a Baja 1000 finisher that lives here in town. He's an awesome rider in sand. He starts the lesson by riding his 950cc KTM LC8 through a deep sand section while thrashing the bars from side to side, hitting the steering stop each time. The bike goes perfectly straight. There were big piles of sand to the sides of his track where the front washed out, but the rear tire track was a straight line. He then explanes that you can NOT steer a bike in sand by twisting on the handlebars, you have to steer with your feet by shifting your weight from one footpeg to the other and throttle control. Then he started doing figure 8s in the sand with only one foot on the bike at a time and the other way up out about tank height like a circus clown. I learned a lot that day and don't have problems riding in sand like I used to.
*/tangent*

I don't think a .6 horsepower 16 pound hub motor would do a darn thing in sand. Depending on the bike there's anywhere from 20 to 100 horsepower to the rear wheel. What's half a HP going to do?

Have fun and good luck!
 
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