2 motors 1 bike?

Discussion in 'General Questions' started by Dylan Siu, Sep 23, 2016.

  1. Dylan Siu

    Dylan Siu New Member

    I currently have a 49cc kit on my beach cruiser and a friend has an e-bike he built. I'm a noob in the forums so I'm not sure where this goes. But me and this friend had the idea of getting two bike kits and mounting them both to a single bike. One on the front wheel and one on the back. Im leaving out what kind of bike to make the question a little more broad. I'm asking for thoughts such as...

    Complications of having both motors

    I'm thinking it's possible to link the throttle to a dual brake lever to pull both throttle and clutch cables evenly. I feel it would also be difficult to keep the front drive chain with tension. I could weld a cage or frame like mount to place the front motor. What am I forgetting?

  2. zippinaround

    zippinaround Active Member

    using them both at the same time probably wont be much different to just having the petrol engine but could be good using them individually i.e when out of petrol switch to electric
  3. FurryOnTheInside

    FurryOnTheInside Well-Known Member

    The front and rear wheels move the same distance when going in a dead straight line but when you go around a corner or just wobble a bit the front wheel takes a longer path than the rear so it must rotate faster.

    On cheap kits with no QC and tolerances a mile wide it is possibly best left to someone very experienced to try to synchronise the engines if it's possible at all.. but as above I doubt that would work well anyway!
    The kit is a bit heavy for mounting above the front wheel, the engine mount studs are not in a convenient place to bolt to any existing rack, and the exhaust is not a convenient shape. It's a lot of work to find out whether it can work at all.

    An I.C.E. / electric hybrid would be really cool so you can be silent in town but have power and convenience out on the open road. A freewheeling mid mount electric motor may be easier than a front hub motor. Two complete motor systems is really expensive though!
  4. Frankenstein

    Frankenstein Well-Known Member

    I was looking at the push design section of this site. Was wondering how well it would work if a motor was hooked up to a push rig with a decent ratio (think higher speed per rpm, so to use it as a pusher at high speeds) while also using my jackshaft motor which is freewheeled of course. This would remove issue of different speeds of 2 wheels since the front of the 2 driven wheels would be able to move faster without any complications.

    It almost seems too easy, and while the cables would need to be massively long for the application it still seems like an easy experiment to give a shot at. I could imagine the looks the police would give. Pretty sure no laws written up preventing 2 separate motors driving 2 separate wheels. In fact I think pusher set ups are completely outside the realm of the current law since I think it's better defined as a motorized trailer designed to be towed by a bicycle rather than a motor assisted bike...

    The problem would be handling 2 throttle systems and clutches at once. I can see a thumb throttle being acceptable, but a clutch takes a bit more leverage than I think my thumbs can muster up comfortably, perhaps a centrifugal clutch would be viable, but that requires starting the motor before its intended time of use, if it stalls at any point before you use it that would be a pain...

    Perhaps if I grow a third arm I could handle the logistics...
  5. Steve Best

    Steve Best Well-Known Member

    No syncro needed unless mechanically connected. You could run 2 gas motors with different ratios on each wheel and it would work fine for the most part. There are some small oversteer/understeer issues, more or less the same as weight bias/balance.

    I am all up for an ICE/Elec hybrid and sharing the workload over the 2 wheels. I'd rather have a 1hp (750w) front drive and a 2hp rear drive than all 3 hp on the rear wheel. I could see the front hub being low speed high torque for starts, town and trails with the ICE being for higher speeds and distance and both being used for mid speed hillclimbs and mud or dirt.
  6. butre

    butre Well-Known Member

    yeah as long as the engines aren't mechanically connected the rear engine will just have less load on it. if they were mechanically connected worst case scenario you have wheelspin through corners, but that can be a fun scenario if you expect it
  7. FurryOnTheInside

    FurryOnTheInside Well-Known Member

    I was really expecting some sort of horrible engine braking effect from the front wheel drive every time the bike deviates from a dead straight line. Is this not correct? (I am assuming that only one throttle would be used for both engines)
  8. Steve Best

    Steve Best Well-Known Member

    I have limited experience with hub motors but the ones I've seen have either a one way bearing or very limited resistance to forward movement. I do plan on running both motors on one throttle. No horrible engine braking effect will occur because there is no mechanical connection, however any drag on the front wheel on slippery surfaces can be a bad thing.

    The turning lockup thing is only from a mechanical connection between the wheels.
    Even it goes away if you are applying enough power or the tire loading is very light.
    Very familiar with this on ATVs and off road vehicles.

    The old Rokon 2wd bike used a ratchet over-run device and later a spring wrapped around the shaft to accomplish the wheel speed differentiation.

  9. FurryOnTheInside

    FurryOnTheInside Well-Known Member

    What about with a pair of 48cc ICEs controlled by a single throttle though? I think that was the original proposition. My comments above were mostly based on reading the 2wd on one engine threads.
    So if the front wheel resistance is lowered by turning a corner,, that will just allow it's engine to turn faster with the same throttle setting? That's good news. :)
  10. Frankenstein

    Frankenstein Well-Known Member

    A spring wrapped around a shaft... What a hell of a good idea for a differential!

    Now that has me thinking about something rather interesting, a trike with independent rear wheel suspension AND differential!

    Does anyone know if this exists yet so I don't have to try to invent it for the hell of it, I've been looking at trike designs and implementing a motor (definitely 4 stroke) into one but I can't get past the fact that without a differential it would nearly want to fall apart and if I'm going to make a trike I'm going to make it comfortable as possible. Rear suspension almost sells the idea to me...
  11. Sounds like a head ache