8kW E-Bike Qulbix Q76R 100lb trail beast

Discussion in 'Some Assembly Required' started by sailah, Sep 11, 2017.

  1. sailah

    sailah Lampin' it

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    Well let's see, where to start.

    I bought a second hand controller from Endless Sphere just to get things rolling. Spent all afternoon redoing wiring to fit the new 300A Kelly controller. Got it to work.

    Secured battery with fiber tape and rode around driveway. Went awesome. Thing is just nutty with power. Which upon retrospect should have been clue number 1...

    So I went out on main rode and ripped up sidewalk. Thing wheelies going 20mph, and I'm 240#. So I start really getting after it and hauling down the bike path. For reference I was wearing shorts & flip flops.

    Then I turn around and head back.

    All was going great until the fucking rear wheel literally flew past me. :eek7 Like really fast. The back of the bike dropped down, out came the feet and I skidded across 2 driveways and came to a rest. The rear wheel kept going and crashed into my neighbors house. Who promptly came out to inspect the projectile that plowed through their bushes and hit the house.

    I was just dumbstruck. It would have been the best youtube video ever. I don't know how I kept it on 1 wheel.

    Anyways, the rear dropouts got seriously torqued and I think are pretty effed. Will require swingarm removal and bring it into machine shop. Quite a bit of damage. I think the torque just twisted it right out of there and snapped the 2 dropout retainer bolts. Will need to rethink this.

    :muutt

    20180609_175425.jpg
    #81
  2. Kai Ju

    Kai Ju Long timer

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    a rare case of too much power.
    #82
  3. Salsa

    Salsa Long timer

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    Check this out and see if I am correct.

    HP = watts = Torque * Velocity * a constant.

    So Torque = (8KW) / Velocity

    From a standing start and at low velocity, HOW MUCH TORQUE DO YOU HAVE ????

    Don
    #83
  4. sailah

    sailah Lampin' it

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    A fuck load.
    #84
    woods wizard likes this.
  5. Yinzer Moto

    Yinzer Moto aka: trailer Rails

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    That is a bummer about the setback. That is a downside of hub motors, all of the torque is transferred through the axle. On ones I have used in the past, they would have a steel torque arm that came off of the axle and attached to the swingarm/frame. Similar to a coaster brake arm. Does this setup use something similar? Or can you make something similar?

    As a side note, I had something similar happen on a downhill bike during a race. On the fastest section of the course, I snapped the rear dropouts off (swingarm was a similar design to what you are working with). At 40 ish mph, my rear wheel passed me. The bike dropped down on the swingarm and I rode it out, like you did.
    #85
  6. sailah

    sailah Lampin' it

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    Yeah these dropouts are more like a motorcycle than a bicycle. But since you don't slide the axle thru like a dirt bike, they have to have the rear open and that's what did me in. All the torque is being transferred through those flat on the hub motor axle and apparently it's a lot.

    I will remove swingarm and bring into shop. At a minimum I expect I'll need to TIG weld up the drop outs and bend them back into place. I may also look at machining a set of torque arms in addition.

    Now that I think about it, I did not actually have the 2 small M5 bolts that pinch the drop out closed. I remember fighting the threads and retapping them. So I suspect that had a major impact. I also remember tightening the axle nuts but can't remember if it was a final tightening. So clearly entirely my fault for rushing out to try it and not being thorough.

    But now that the adrenaline has worn off, let me say that in the 5 minutes I did ride, this thing is an absolute riot. It wants to romp, I can't remember a vehicle that has so much snap for its size.

    Will be fun to get it working safely.
    #86
  7. Yinzer Moto

    Yinzer Moto aka: trailer Rails

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    I did not want to blame anything on you but I did suspect forgetting to tighten the pinch bolts. I can totally see myself doing something similar, getting too excited to go take the thing for a rip down the street.


    There is also a extreme amount of torque through that area. I am not a fan of a design that relies on 2 little bolts to keep the wheel from torquing out of the frame. Good engineering allows for some human error without catastrophic results.
    #87
  8. tinwelp

    tinwelp Professional Idiot

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    Yeeouch. Glad to hear you're OK as this is an interesting thread!

    So looking up the specification of your motor I see a maximum of 170Nm or 182Nm depending on the motor version and peak current capability of your controller... and bugger all of anything to react with the torque. Am I correct in thinking all of the reaction torque is transmitted through the flats on the axle? If yes, I'm astonished this could work for any length of time. 180Nm is the sort of torque you'd expect from a little car engine...

    You can probably make this work if you were to make sensibly designed wheel dropouts in steel with a bit of strength, at least 10mm thick, and a decent sized pinch-bolt (M8 minimum). Alternatively, the motor could be modified to incorporate a bigger bearing to allow a chunky pin to pass from the stator to the frame. Many other ways could be dreamt up too, depending on what you have and how well equipped a workshop you have.

    Just straightening everything out and adding your tiny pinch-bolt probably won't be enough...

    Good luck.

    Cheers... Paul
    #88
  9. sailah

    sailah Lampin' it

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    Thanks Paul.

    The dropouts are really stout, or at least they were until I sparked off half the material riding on 1 wheel:lol3

    They are steel and 10mm thick. The slot aligns the flats on the axle and all torque is applied through this interface.

    I think I made 2 mistakes. First I forgot the pinch bolts, they did not break as I had thought initially. I also found them on my desk later lol. Also I do not recall really torquing the axle nuts, I mean they were certainly snug but not torqued. And I was in a rush to ride it.

    I think I will remove swingarm and bring that and wheel into my shop. Will torch/bend the remainder of the dropouts into place and then see what kind of room I have to possibly add a torque arm in addition as a doubler. Thinking I could laser this out in the exact shape of the axle so there is no way for it to torque out like the dropouts. I would need a way to bolt/secure to swingarm but that's easy enough to do.

    I have a fairly well equipped shop with mill, lathe, TIG welder etc.

    I don't recall anyone else suffering this fate on Endless Sphere and there are quite a few Quilbix frames running similar setup as mine. I think it was probably operator error.
    #89
  10. dentvet

    dentvet Long timer

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    #90
  11. sailah

    sailah Lampin' it

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    LOL haven't done squat. Super busy with being a startup, basically haven't even looked at it since accident.
    #91