Brompton P-Line Rear All Axle Motor Build

This build came about because I really wanted a regular brompton with a grin all axle motor, and my dislike of a front mounted motor on the brompton. I previously had a crystalyte front mounted motor build, but I didn’t like it all too much because of how easy the bike tips when it’s folded (need to usually have a hand hovering around it), and the limited crank options that come about when using a bottom bracket based torque sensor. To fit the motor, I had to use an aftermarket titanium triangle (from hexati or ti-atom) instead of the stock triangle (overall I’ve had no issues with the triangle). Other than that the current iteration of this build is kinda jank (haven’t gotten around to 3D printing a custom housing for the controller so it’s just held to the bike with some voile straps for now)

It’s worth mentioning that I started this build before brompton rolled out their e-motiq rear mounted electric bromptons, but because the torque sensor they use has a much lower resolution compared to the all axle and erider, theres a pretty noticeable delay for the assist to kick on and kick off when you stop pedalling. Overall I didn’t like that as much - also no regen )

Overall the all axle motor has been great on this build, and my only gripe with it is overall weight. But because it has a cassette based torque sensor, I can save a bunch of weight by using a lighter crankset and skip the bottom bracket torque sensor - resulting in an overall weight similar to just the weight of a front mounted crystalyte motor. The weight being closer to the bike’s centre of gravity in the folded position, also makes the bike ridiculously stable while folded. Also despite being on the rear, the regen and braking force with the all axle is far greater than the crystalyte brompton motor.

Quirks:
- Because of how large the diameter of the motor is, and how small the diameter of the rim is - I did have to use schwalbe click valves (it’s better anyway) instead of presta valves, and had to machine a custom 90 degree click valve pump adapter to fit into the small gap between the motor and the rim to inflate the tires.
- Some titanium aftermarket triangles may use a slight dish offset. For my triangle I just had to tighten all the right side spokes and loosen all the left side spokes to account for that slight offset.