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Specs

Pack 8x Makita Lithium Ion Power Tool Batteries
Capacity 432 Watt-Hours
Configuration 2 series 1 parallel = 24 Volts 12 Amp-Hours
Max Power 3C => 36 amps@24v = 864 Watts
Charge Time 8 Hours
Motor Kollmorgen 400 Watts/0.5HP Rated (1500 watts/2 HP actual)
Gearing 72:11 single speed No.35 chain drive
Controller Kollmorgen 400 Watts (actual 750 watts/1 HP)

Problems

  • Previous long wheel base bicycle was extremely long– 6 feet
  • The most nagging trouble area for the long wheelbase bicycle is the long chainline and gearing

Solutions

  • Build a compact recumbent bicycle with a shorter overall length
  • Build a simple serial hybrid drive, using very little chain

Results

Compact Recumbent

A compact recumbent bicycle can easily be built out of a children’s bicycle. A boom is simply attached to the front and a seat mounted to the top of the main triangle. The original seat post can be used to support a seat back, much like the Cruzbike conversion. The handle bars are more difficult. The old style threaded head tubes do not make it easy to attach different styles of handlebars. Newer threadless headsets are better suited for this. Positioning of the handlebars is also critical. The handlebars should be just behind and clear of the knees. Extending them higher leads to fatigue in the arms. The width of the handlebars can also be reduced.

Serial Hybrid Drive

A serial hybrid has two or more motors (in this case, a human and an electric motor), but only one mechanical connection to the drive wheel. The coupling of the motors is electric. A simple serial hybrid drive can be built using scooter motor attached to the bottom bracket. The output of this motor is attached to a battery through a diode, a simple electronic device that allows energy to flow only one way. The diode prevents the battery from spinning the motor. The voltage of the generator motor must exceed the battery voltage for the generator to charge the battery so for this bicycle the generator was attached to one 12v lead acid battery. The setup is not efficient (probably 40-50% in this simple form) but it would be useful for a bicycle where a mechanical coupling is impractical.