I have finished electrifying the wheelchair-and-bicycle tandem that we use for family outings with a 15-year-old teenager. As promised, I am sending you photos of the build.
I tested it over about 120km with a 70 kg load at the front: two bags of sand. The motor provides tremendous help, but control below 8km/h is unsatisfactory; see the end of this email.
The tandem was made by combining a modified conventional wheelchair with 20″ wheels and an old mountain bike whose rear frame was reinforced to support the motor.
They can be separated quickly using a toggle latch, leaving the handlebar on the bicycle and the front brake lever on the wheelchair, as on a commercial model.
The gear controls are grouped on the right of the handlebar: a half-twist grip for the rear derailleur and a lever for the front. The left side carries the removable front brake lever and the thumb throttle. This arrangement has proved very practical. An electric retarder control was provided for safety: the red button.
The controller’s many wires and connectors required a separate junction box.
The battery is a 36V-14,5Ah model and will be more than sufficient for the intended use. Pedalling normally without exhausting myself on a varied route, I get a range of around forty km. The passenger will get tired before the battery does!
The throttle control you recommended is smooth and easy. I appreciate the assistance-level adjustment, which seems to depend on speed: each setting has a speed above which electrical power drops to its lowest level, around 6km/h at level 2 and 14km/h at level 3, and so on. This suits the way I use the bicycle.
However, this bicycle is often intended to travel slowly and, when necessary, start on a hill. Motor control below 8km/h is disappointing. Under load, it is very noisy and transmits strong vibrations to the bicycle. I expected better, especially as the controller seems to use the position sensors: if they are disconnected, the motor no longer works. By comparison, my postman’s electric bike, with an 8 Fun rear hub motor, does not do this at all!
* Is there anything that can be done, perhaps a programming setting to change? Please let me know.
Kind regards,