Discussion in 'Electric Bicycles' started by MX21, May 27, 2008.

  1. MX21

    MX21 New Member

    I had a GEBE on my mountain bike and while it worked ok, I've really been wanting to go electric, since I fly RC electric airplanes. I also want to be a little more stealthy.

    I had already purchased a speed controller and was selecting a motor and batteries, doing the calculations, when I saw what this guy was doing:


    That spurred me on since he was successfully using almost identical components to what I had picked out. I was trying to figure out how to attach my motor and drive the wheel when I realized I already had the mounting bracket and belt reduction in my GEBE. So I pulled the gas engine off the bracket, drilled 4 bolt holes and mounted my electric brushless motor. I got an HTD pulley to fit the motor so it will work with the HTD belt and ring.

    Haven't ridden it yet, still mounting the rest of the electronics. But bench testing looks good so far.

    Think it will work?

    Last edited: May 27, 2008

  2. MX21

    MX21 New Member


    Attached Files:

  3. Esteban

    Esteban Active Member

    Looks great. I have thought about the same idea. Hope it does well for you !!
  4. Ypedal

    Ypedal Member


    Q: How does that big rim looking pulley fit/mount to the spoked wheel ?
  5. MX21

    MX21 New Member

    It has a bunch of notches in the edge that snap onto the spokes. You can sort of see it in this photo:

    Attached Files:

  6. JemmaUK

    JemmaUK Guest


    I cant see why it wouldnt work, but I suggest some sort of variac controller or the power delivery will be snatchy which is the last thing you want.

    I would also most definately advise a powerful horn - 30mph while sounding like a lawnmower on amphetamines is one thing - people can hear you. 30mph on something thats practically silent is another.

    good luck with it - and if you get it working dont forget to talk to the people at GEBE - I think Dennis would be very interested in the concept since it has advantages of quietness and compactness..

    Jemma xx
  7. MX21

    MX21 New Member

    I wired up a thumb throttle lever to control motor speed. It has a spring return to so throttle goes off if released (required in California I think). I'm using a standard RC speed controller that takes a pulse width input for speed control. The throttle lever is wired into a servo tester to generate the require pulse width control from the pot.

    Last edited: May 28, 2008
  8. MX21

    MX21 New Member

    Update: tested a run around the block. I get a little bit of skipping of the belt if I throttle up too fast, especially uphill. That's manageable. Under load though, I'm getting some slip and squealing from the motor. I think I have to change some options in the brushless speed controller to prevent it getting out of sync with the motor.

  9. split_yer_wig

    split_yer_wig New Member

    that looks like a great idea.......i think that opens up alot of possibilities......i like the belt drive idea better than most as far as motorized bikes...i think i'll look into a 1000watt motor as opposed to a 4 stroke now.............**** you i was just ready to buy a gebe kit with a tanaka 40cc engine.........but now im gonna keep up with your progress as i may just "go green"
  10. MX21

    MX21 New Member

    I may have a Tanaka 40cc engine for sale soon. :lol:

  11. split_yer_wig

    split_yer_wig New Member

    sweet........but im gonna check your progress on the e-motor.........like i said.............the possibilities are better on the electrical side of things.................i wonder why no one bothered to try this before..............................if it ends up working well for you im in like flynn.............................****,im thinking of hooking up a powerfull 1000 watt or even HIGHER engine and forgetting about front hub kits with gas back end hybrid stuff......just wheel into work and plug in the breakroom......................................maybe even offer to build everyones bikes at work for lunches and afterwork beer.....i know alot of them will want one too.....i just gotta do more research on electrical stuff.......................and of course battery technology
  12. split_yer_wig

    split_yer_wig New Member

    updates bro?..............i have a feeling that this can be alot more powerful than a hub.....not just because you can install more powerful motor but because the pully/belt system offers more torque (or so i would guess)..............you may be onto something here
  13. augidog

    augidog New Member

    i've been watching this with great interest...as soon as i saw the subjectline, it made perfect sense :cool:
  14. MX21

    MX21 New Member

    No update yet. I sent a support request to the manufacturer of the speed controller to find out the best settings for a high-torque application like this. They haven't responded yet. I may just do some experimenting tonight with some of the settings like motor start power, advance, PWM rate, etc.

    I'm also working on an instrument panel. My other hobby is radio-controlled airplanes, with experimentation in UAV applications. I have a board I built that uses a GPS to log speed and position, plus current, and voltage to an SD card. I've modified my current sensor to handle higher currents. This way I'll have a live display of current, voltage, watts, avg watts, speed, climb rate, odometer, etc., plus a recording of the entire trip.

    Last edited: Jun 11, 2008
  15. MX21

    MX21 New Member

    Took it out again tonight after tweaking a couple of the speed controller settings. Seemed to work a little better. Then while coasting in the driveway, the motor started making noise. Looks like a magnet came loose. :( I'll have to see about getting the motor fixed or replaced.

  16. MX21

    MX21 New Member

    Am I overworking the motor? I only peaked at about 53 amps today. But is the torque too much?

    The drive ratio using the 17 tooth pinion on the motor and the 266 tooth GEBE ring is about 16:1. Am I require too much torque from the motor? Would it be better to add another reduction stage and use a higher kV motor?

    Which is better: use a low kV (171) motor with 16:1 drive ratio, or a higher kV (340) with 32:1?

    Or maybe this motor had problems to begin with. ?
    Last edited: Jun 12, 2008
  17. Alaskavan

    Alaskavan Guest

  18. split_yer_wig

    split_yer_wig New Member

    wondering if titan system would be better if using electric motor.......im thinking a little less torque
  19. srdavo

    srdavo Active Member

    electric motors produce a "bunch" of low-end torque.

    coupled with a 16:1 gear reduction, thats a "whole bunch more" torque.
    (also resulting in a lower top speed.)

    what is your motor's max. rpms?

    on your test rides....what speeds are you achieving?
    Last edited: Jun 15, 2008
  20. MX21

    MX21 New Member

    The motor is rated at 171kV and up to 12s lithium battery (44.4v), so rpm at max volts is about 7600 in theory. I get around 30 mph on level ground, which seems to agree pretty close with calculations.

    I got this from the motor speed controller support (Castle Creations):

    You are correct, under load the ESC is loosing sync with the motor. Low ‘motor timing’ helps
     with this but as you are already at low there is no help here. The problem is, with these large, low Kv 
    outrunners when you put them under too much load the stator iron saturates and becomes a dead short 
    to the ESC. Of course, when this happens the ESC can no longer accurately read the back EMF from the 
    motor and looses sync and you can get no more power or the motor stops suddenly. Iron saturation is 
    the bugaboo in the closet with outrunner motors. 
    I'm not sure I understand this. The meter shows a max of about 53 amps, yet I'm overloading the motor? The motor does get pretty hot, but I was wondering if that's due to the loss of sync. Maybe the current is jumping way up when out of sync, but only periodically and the average current is still low.