What do front hub motors weigh??

Discussion in 'Electric Bicycles' started by vanilla ice, Sep 4, 2007.

  1. vanilla ice

    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.

  2. azbill

    azbill Active Member

    front hub motors are not recommended for suspension forks, due to their torquing in the dropouts
  3. vanilla ice

    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.
  4. StreetPlanes

    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.
  5. vanilla ice

    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?
  6. vax

    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...
  7. vanilla ice

    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.
  8. RLK

    RLK Guest

    In the neighborhood of 15 or 16 pounds.
  9. vanilla ice

    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.
  10. RLK

    RLK Guest


    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.

    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!
  11. Donny G

    Donny G Guest

    I've got a pair of crystalyte 406/408 two speed hub motors collecting dust
    these are dual winding motors suitable for high voltage at 60v they pushed my heavy 26" wheeled schwinns to 34 mph @ 40Amps at 72 volts they would
    seriously haul Balls
  12. vanilla ice

    vanilla ice Guest

    You could be right, I'm not sure. The ohlins Yamaha setup only transfers a small percentage of the WR450's power to the front. IIRC ~10- 15%. Thats what makes me optimistic something like an electric motor can work. Those things make like 50hp, so figure 5hp to the front may be enough.

    And by work I mean slightly improve handling characteristics, not aid in acceleration. After all this is hugely inefficient- transferring power from an internal combustion engine to electricity, and back into motion through an electric motor. But it could be worthwhile depending on the effect on handling. The ohlins hydraulic setup is likely just as inefficient.

    Who knows maybe mimicking the ohlins setup with a couple of industrial small hydraulic pumps would work too. IMO that would be more difficult for a shade tree type though.

    You're saying 0.6hp, but there are much more powerful hub motors available. Heck I'm running my currie motor at over 1200watts and its a cheap little tiny bugger. And then theres always fork mounting a motor if a hub motor cant cut it.

    It would be interesting to see what kind of heat would be generated. You've got to remember the ICE is still powering the rear wheel also. That should reduce the current draw somewhat.

    I'll probably just stick to bicycles for now. I'm sure somebody will try this fwd thing on a ICE motorcycle sooner or later. From the rave reviews 2wd motorcycles have been getting I'd say its worth a shot. And as time passes the tech gets better, motors get lighter and more powerful. I'll return to this thread in five years and see if I was wrong.
    Last edited by a moderator: Sep 19, 2007
  13. RLK

    RLK Guest

    The next question might be...

    Why don't racing snowmobiles have powered front treads where all the best currently winning race sleds have skis?

    The physics are similar. Any good sand rider will tell you, "Keep the front end light" while making a twisting throttle motion with his/her right hand.

    Keep the front wheel light. :cool:

    Edit: A seperate part of the lesson I took from the Pro rider was about bike setup. I ended up buying high rise ATV handlebars that brought my controls exactly to belt height when standing on the pegs. That alone made technical riding of the bike over sand and rocks and mud and all other challenging terrain a billion times easier. Still, its all about weighting the footpegs.
    Last edited by a moderator: Sep 19, 2007
  14. DougC

    DougC Guest

    Before I was born, my mother's family had a Rokon 2WD motorcycle on their farm. I am told that you could be in the middle of midwestern-type woods and it would go anywhere you pointed it without much trouble. Riding across freshly-plowed fields was no big deal. Wasn't very fast (more like a giant minibike) and was rather expensive though.
  15. beast775

    beast775 Guest

    e bike gas power

    i liked the rokon i remember riding one mid seventies i beleve to long ago to remember!built a hybrid 43cc gas rear and 600 watt ehub front.i drove up a 20% gravel grade standing up and the ehub really pulled well, i drove up the same grade with just the ice motor and had to jump off at the top and push the rst of the way:shock:,but all the weight and mechanilcals on the hybrid would not be worth making for all day off roading,i have video of the said gravel grade but am losing interest as i type.115 lb bike vs 48 lb bike id rather push for 5 seconds compared to all the madness from a hybrid gas back electric front,did not compare to me.:eek:
    Last edited by a moderator: Nov 4, 2007
  16. billvon

    billvon Guest

    He may be quoting average power. That's one problem comparing motors; gas engines are rated at peak power and electric motors rated at average. I have a Crystalyte 5304 that I can run at over 5kW (about 7hp) in short bursts. I think it's rated around 500 watts though.