Human Electric Trike Thesis

Design of an electrically assisted human powered trike


Posted by Bob Dold on Saturday, June 3, 2006 10:50 PM

BikeEV Specifications

The following list of specs is primarily from my memory; errors and omissions will be corrected as they are discovered!


24V permanent magnet DC (PMDC), 1HP with integral 11:1 right-angle reduction gearbox (330RPM max. at output shaft). Sourced from EMD (Electric Motor Developments) in Essex, UK. (approx. 23lbs)
Made by Curtis (1206?), purchased rebuilt from Test Engineering with custom 80A current limit to protect the motor.
2 Hawker Genesis 12V 26Ah sealed AGM lead-acid batteries, wired as a 24V pack.
Parallel human/electric hybrid. The rear wheel is driven by a 7-speed Sachs internal hub, which is in turn chain-driven from the motor output shaft (at a 1:1 ratio?). The motor output shaft can be driven directly by the electric motor as well as by the pedals, via a 7-speed cassette. A freewheel between the 7-speed cassette and the motor output shaft allow the pedals to remain stationary even while the motor is running.


Top speed:

50kph (level ground, electric only)
60kph (electric + pedal assist).
30km to 80% DOD (real-world commute with hills at full speed with occasional pedal-assist).
Bike (including Zipper fairing and Sachs hub): C$2500
Electric drive components: C$500
approx. 100lbs total (23 motor + 29 bike + 23/battery + misc.)

The adapter and drive sprocket are now mounted on the output shaft, and the 7-speed cassette/freewheel threaded onto it. Unfortunately, I neglected to get a photo of the adapter on its own first. The output shaft has also been shortened at this point.

One of the two Hawker Genesis batteries is visible, suspended from the seat frame. The 12V batteries are wired in series to supply the 24V motor.

From the run of the drive chain, it is evident that the drive and driven sprockets are about the same size (24T, IIRC). The largest sprocket on the cassette driven by the pedals is a few teeth bigger (26T, again IIRC). The drive ratio from the motor back was chosen to allow a top speed of about 60kph, and the ratio from the pedals to allow a cyclist to provide some degree of pedal assist at all speeds.

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