Bafang PAS senso

[lamonabike]

Hi. Has anyone recently converted their Rohloff-equipped Thorn with a Bafang front motor?
There’s a couple of issues Id like to understand.

The online sales stores (Amazon, etc) offer a left side and right side PAS sensor, neither of which seem very compatible with Thorn’s BB. Has someone fitted either of these successfully?

Also the Thorn dropouts are 9mm. I can’t tell but I imagine the Bafang kit requires 10mm. Has anyone successfully installed this and what was the solution?

Thanks!

[Andyb1]

On my wife’s hybrid I had to file the front fork dropout to 10mm to take the hub motor axle.   Could you find an older / cheaper fork?

[lamonabike]

Thanks. Could do yes. I’d rather avoid either!

Filing down is something I could live with.
I’m less convinced that the PAS sensor will fit and there doesn’t seem to be a way to check

[Danneaux]

Rather than modifying the fork, I'd be inclined to try filing flats on two sides of the axle, where it protrudes past the bearing locknuts. If you measured carefully to make sure they were in the same plane side-to-side, I think removal of only the threads (0.5mm each side) would fir the dropouts while still leaving adequate full threading for locknuts.

Best, Dan.

[Andyb1]

The axle reacts the electric motor rotation and it is imperative that it can not spin in the fork (or the wiring will twist badly and get wrecked).  ‘Torque brackets’ are available in stainless steel on ebay that go on the axle and bolt to the mudguard stay holes, but are probably only made for a 10mm axle.

[lamonabike]

Thanks all.

How about the PAS sensor. Has anyone got it to work on a Thorn using either the left or right side version?

[lamonabike]

I thought you might be interested to hear the latest on this.
I bought a left handed PAS sensor for £12 or so and installed it on my Thorn Raven crank.
It went on okay but as I was installing the crank arm back on it felt like I was crushing the sensor.
Just been out for a short ride and the turning of the cranks feels different.
I’m still not convinced it will all work but I think I just need to go ahead and buy the full kit and see what happens.

[lamonabike]

Photo of the PAS sensor

[Andre Jute]

There's a clearer photo of the sensor, and its receiver, in my 2012 set of articles Building an Electric Bike, which deals with fitting a Bafang front-drive motor and its control elements, starting at
https://www.coolmainpress.com/BICYCLINGbuildingpedelec1.html
The second article
https://www.coolmainpress.com/BICYCLINGbuildingpedelec2.html
contains the clearest photo of the sensor and receiver:


Note that while I left off the sensor and its assorted electronics as counterproductive to my intention on hand of advice from my local police here in Ireland, in Britain fitting the sensor may be a regulatory matter depending on the intended use of the bike. (On my current installation of a Bafang centre motor on my everyday bike which is not a Thorn, the sensor and its receiver are both internal.)