No announcement yet.

MY1020 motor with 6 speed jack shaft

  • Filter
  • Time
  • Show
Clear All
new posts

    MY1020 motor with 6 speed jack shaft

    Just started my first ebike build, I'm planning on running an 1800w MY1020 motor under the seat with a 10t bike sprocket and a 6 speed freewheel hub and derailleur above the back tire on a jack shaft, I could have ran the motor direct drive but i wanted it to be able to free wheel with as little drag as possible and still have a range of gears so it will hopefully have enough torque to get up hills. I'll be running a 50t motorised bike sprocket on the rear rim so I should be able to run a heap of torque through the motor without straining the chain too much.

    Im going to weld a cargo rack on the back of the bike tomorrow that will give me something to mount the hub and motor to.

    Unfortunently im on a pretty tight budget (the reason I can't afford a good mid drive set up) so I'll be trying to get the cheapest possible parts for it. I'm planning on running 72v eventually 36v for now. Just wondering if anyone has used the 72v 80a kunray controller off eBay, it seems cheap at $200 and has 24 mosfets.

    Ill upload some better photos tomorrow after I've welded the hub and cargo rack on
    6 speed free wheel hub that will be welded above the back tire

    I've got everything welded up now but I think I'll add some extra bracing to support the motor as its is heavier than I expected. I'll have to work out the gear ratios too but I think it's going to be too high for the motor even in the lowest gear as it recommends 4500rpm for the motor so I'll have to try and get it doing 4500 at 60kmh in highest gear. Im also not sure how it will go changing gear, I can already see the chain coming off the motor if you were to change it more than a few gears as the sprockets will be way out of line. It should work fine if I aligne the motor to the best gear and fix the derailleur in that position.

    Just need to get a battery now, I was originally going to get 36v 10ah x4 so I could easily run 72v when I upgrade the stock 48v 32a controller but that would mean id have to get a 12v battery to bring the voltage up to 48v and it would be complicated to charge all the 36v and 12 v batteries so I think I'll just get a 48v 20ah to keep it simple.

    Im going to be using it in heavy rain too so any advice on what parts to waterproof would be greatly appreciated. I'm pretty worried the throttle will break if it gets drowned in water, I'm going to make a waterproof box for the controller and battery and use water proof joiners on all connections.

    Just checked the gear ratio and there is a problem, at 4500rpm the wheel will be doing 93kmh so at 46.5kmh its will only be doing 2250rpm which i think is way too slow, im not sure if this will damage the motor running it that slow cause its never really going to see more than 2000 rpm. I think im going to have to put another jack shaft on it to bring the gear ratio down a bit, id like it to be doing 4500 rpm around 60kmh.
    Last edited by ben4221; 03-22-2019, 12:56 PM.


      After some thought i have decided to start from scratch with a 20" rear wheel, i found one at the tip for $5 and it has a 6 speed hub attached which will be great for pedaling along at 60kmh im a bit worried that the 50t sprocket will not bolt straight up to the 20" wheel but apart from that im very keen to build the frame from scratch as it will allow me to custom build it around 2 48v 20ah batteries and it should also allow me to mount the motor with a way lower center of gravity and possibly hide it from view and mount a dummy 200watt motor on it to keep the police happy all though if i put a 200watt sicker on the 48v motor it might be enough to fool them if its speed limited and the pedal assist sensor are hooked up.

      The gear ratio is 5.925 which works out to be 72kmh at 4500rpm with a 20" wheel still way to high for the lowest gear but its better than 93kmh. Im also quite worried about the brakes as my old petrol bike used to top out at 47mph (75kmh) and the brakes were completely useless at that speed I hate to think of trying slow down a twice as heavy electric bike that free wheels so you've got no engine braking what so ever. I may have to fit some large diameter disk brakes to the front and rear rims and maybe an additional jack shaft that has a disk brake fitted sort of like a transmission brake, i think i will run another jack shaft to bring the gear ratio down a bit as id like to have the motor spinning around 4500rpm at 50kmh in a higher gear on the hub so i can still down shift if theres a hill or strong head wind.