Drum wrote: ↑
May 25 2018 4:26am
I recently repaired a TSDZ2 motor unit and mounted it on my spare mountain bike to test it.
While I had it apart I noticed that the large steel output gear that the chainring is mounted on was solid and did not have the sprag clutch (one-way bearing) in the centre like all the disassembled motors I had seen photos of previously. I assume this motor was the "coaster brake" version. Without the sprag clutch, pedaling backwards DID run the chain backwards and would work just fine with a "back-pedal" coaster brake.
So I assume that if you order the coaster brake version of the motor, the solid gear will be installed and it will do what you need.
There is one very minor issue: the pedal shaft is now driven by the motor.. the pedals must rotate with the chainring, and if the motor is driving the chainring to rotate forward it is also driving the pedals.
When I suddenly stopped pedalling after pedalling hard, I could feel the pedals kick forward a bit before the controller caught up with the sudden drop in torque on the pedals and cut power to the motor.
This was noticeable but not dangerous.. got used to it very quickly.. but it means you should NOT use a throttle with one of these motors, and if you get one be prepared to live with this little quirk.
Apart from that "kick", the bike rode very well. The torque sensor is "double sided" so "sees" torque from either pedal. The assistance kicked in smoothly within half a rotation of the pedals, then increased assistance smoothly with increase in pedal torque. MUCH nicer and more natural to ride than any bike I have tried with cadence-sensing PAS control.
If I did not specifically need the backpedal brake function I would prefer one of the units with the sprag clutch, however there is an advantage to the solid gear: one less thing to fail. There have been a few people who have had to replace the sprag clutch after it started slipping, allowing the pedals to rotate forwards without reliably driving the chainwheel forwards... not an issue with the solid gear!
Hope that information helps,