Need help installing pedal on a bike without lock ring

[Supreme Kay]

I have a mountain bike to converted into an electric bicycle. However, the bicycle crank does not have a lock ring to install the pedal assist sensor. I can install the magnet disc but not the sensor due the lack of lock ring. I would appreciate any suggestion. I attached picture of the the bicycle, magnet disc and pedal assist sensor

 

[Chalo]

That looks like a cartridge bottom bracket, which has no lockring. But it has a shoulder on the right side, and you should be able to sandwich your sensor between the shoulder and the frame.

It takes a special tool to remove the bottom bracket, which a bike shop has. After the sensor is installed, the front derailleur will have to be adjusted slightly, because the chainrings will be shifted slightly to the right but the derailleur will not.

If you need to put the sensor on the left side, you'll have to get a deeper retention ring or a wider bottom bracket (e.g. 73mm) so that the ring sticks out far enough to thread on a conventional bottom bracket lockring after fitting the sensor.

 

[docw009]

PAS bracket should be so simple, but the kit manufacturers sure don't help. I've put on three of them and have not seen a bike yet where the circular bracket would actually fit onto the BB using its native locking scheme. For that case, the instructions usually say "use glue".

I attached the sensor to the frames of my bikes.

Here I re-used the PAS bracket. Just cut it and folded it.


Then I attached it with a hose clamp.


On this bike, I put it on the non-sprocket side. I used a different bracket because I wasn't sure how the sensor needed to be mounted on this side. I also used a small nut/bolt instead of the original screw because the plastic housing was damaged.
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The magnets have to rotate into this particular sensor, and since that is counter clockwise on this side, the sensor points down. I also found that the disk had to be positioned so it spins opposite to the arrow. Be prepared to test your arrangement.