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I want to convert my bicycle into an electric bike by adding a motor to it, allowing me to ride it using both pedals and the motor. I need to add a motor and a separate chain system, similar to the ones shown in the photos below. enter image description here enter image description here enter image description here I need advice on the following questions:

  1. How can I change the old solid axle to a longer axle that can accommodate two freewheels without causing damage? New, longer axle

Old axle with existing freewheel 2) If I change to the new long axle, how can I fit it to the old frame? I've tried putting the new freewheel together with the old one on the old axle, but it's too tight and the wheel can hardly move. Did not put all the nuts but already very tight Do I have to use some tools to open the frame wider?

  1. Is there a way to put the new freewheel on the other side to replace the position of the brake, in order to save space? Can I put new freewheel on the left side instead, best if I can replace the place of the break on the left? best if I can replace the place of the break on the left? I can change this break to Caliper break to save space for new freewheel
  2. How can I fix the freewheel on the axle? The freewheel and the steel lock nut are too big to hold onto the axle. I can't find information on what I need to add to fix this issue. All I get now with the new adapter and freewheel There are still space between steal lock nut, new freewheel and the axle, cannot fit

I received instructions from the manufacturer, but they are not clear to me. I have been unable to find any helpful information from them or online. Here is how it should be assembled as in the instruction Here is how it should be assembled as in the instruction

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    Great question with a lot of useful photos, excellent work on documenting the situation.
    – Criggie ♦
    Commented Feb 15 at 5:05
  • Could you post a link to the seller's listings ?
    – Criggie ♦
    Commented Feb 19 at 5:42
  • Yes, sure: shp.ee/p332dhf
    – user1314404
    Commented Feb 23 at 7:22
  • I also found out how to use the adapter to extend the hub. Actually I need to turn the ring to the middle of the adapter so that it can fit 2 freewheels on two sides.
    – user1314404
    Commented Feb 23 at 7:26
  • I don't know how this two side freewheels could be possible: abulm.com/?product_id=46172651_56 and abulm.com/?product_id=46172637_56. Can I do that for my bicycle setting?
    – user1314404
    Commented Feb 23 at 7:27

1 Answer 1

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Firstly a quick correction - the freewheel is attached to the hub of the wheel, not the axle. Your axle stays still relative to the frame, and the wheel revolves around the axle on bearings.
Upshot,the freehub needs to drive the wheel's hub not the axle.

So the innermost freewheel will attach to the hub like normal. The outer freehub also needs to drive the hub, but without binding on the inner freewheel. Your supplier is referencing some kind of adapter that will "extend" the hub so that the outer freewheel can drive the hub while the inner freewheel can "coast" You don't want the freewheels or chains to be touching.

An additional problem here is that you're cramming another freehub into a space that doesn't really have room for it. Your options there are to

  • use a narrower wheel hub (increased risk of wheel collapsing sideways under cornering)
  • if its a steel frame then you can "cold set" the rear triangle to be wider, but this is only possible with steel. Your bike looks like aluminium in the photo, so this is not possible
  • final option is to use engineering tools like a lathe to thin down the hub and freewheels to get some few millimetres back.

Most strap-on motor kits avoid this by connecting the motor to the existing chain OR by putting a drive cog on the other side of the wheel where yours has a roller brake.

Upshot - this frame might be a bad choice for electrifying with this kit.

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    The best option is to use the same wheel and find a way to adapt some kind a freewheel to work with the new motor and chain. Can I extend the frame/frame's dropouts by some methods?
    – user1314404
    Commented Feb 15 at 13:36
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    Hi @Criggie, I'm wondering if it's possible to use a 2 or 3-speed freewheel to replace my original one. I'd like to save some space and then use 2 chains on each freewheel separately?
    – user1314404
    Commented Feb 18 at 15:27
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    @user1314404 not really - a multispeed freewheel would mean the pedal chain and motor chain are "tied" and both have to move at the same time all the time. So, you could never "coast" on motor, and the motor has to be running/using up battery even when you don't need it pushing. Manufacturer said "not for speed gears bike" I think your only option here is to talk to someone locally with engineering skills. If you do-away with the pedal chain completely then it is no-longer a bicycle, and becomes an electric motorbike, which has legal requirements.
    – Criggie ♦
    Commented Feb 18 at 21:43
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    I believe I need to find someone as well, but it's been difficult to find a local source. I've already asked two bicycle shops here, but neither of them knows how to help. If I have to order from overseas, what information should I provide to ensure they can make what I need?
    – user1314404
    Commented Feb 19 at 5:22
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    @user1314404 Perhaps you need an engineer who can solve problems, rather than a bike shop. That solution might be widening the frame's OLD measurement, or narrowing the wheel's hub. As it stands the stock wheel can't get another freehub fitted in the available space.
    – Criggie ♦
    Commented Feb 19 at 5:40

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