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Specs

Pack 8x Makita Lithium Ion Power Tool Batteries
Capacity 432 Watt-Hours
Configuration 2 series 4 parallel = 36 Volts 12 Amp-Hours
Max Power 10C => 120 amps@36v = 4320 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 Shenzen Sucteam 400 Watts (actual 750 watts/1 HP)

Problems

  • Cargo capacity limited
  • Over seat steering with straight handlebars limits visibility and comfort
  • Lead acid batteries are extremely heavy

Solutions

  • Add cargo boxes
  • Add passenger seat while remaining compatible with standard bicycle racks
  • Evaluate underseat steering
  • Use lithium based batteries

Results

Add cargo boxes

Adding two carbo boxes was a definite winner. Wearing a backpack is not an option on a recumbent, and anyway wearing a backpack while cycling is never very comfortable. The boxes were chosen to be large enough to fit a couple of laptops and sacks of lunch. One possible improvement would be top lids to keep out rain. Holes were drilled at the rear bottom side of the boxes to allow any liquid to drain out in case of a spill.

Two Riders and Rack Compatibility

It’s possible to put two people within a standard wheelbase if one rider uses a recumbent layout and the other is upright. Based on testing, the center of gravity of each rider should fall within the front and rear axle or handling will be negatively affected (the rear wheel was shifted backwards in mid-2009 to correct this problem). Since the original 26″ wheels were replaced with 20″ wheels, the wheel to wheel length only increased a couple of inches overall, maintaining compatibility with racks found on trains and buses. If the front boom were collapsible, the bike would have the same overall length as a standard upright for storage.

Underseat Steering

Although it might look unusual at first, underseat steering is extremely comfortable. The arms droop down like they might on a couch and just rest on the handlebars. The handlebars must be designed properly to avoid interfering with the rider’s legs when they are down on the ground (instead of pedaling). Cable linkage to the steering is one solution. Another, the one taken here, is to curve the handle bars inwards nearer the head tube.

Lithium Batteries

The lithium batteries weigh about 75% less than the previous lead acid batteries weighed. The bike now weighs one half of it’s total weight with lead acid batteries. It feels more like a bicycle than a slow motorcycle– it is possible to lift it and it does not get damaged when it falls over anymore. The lithium batteries also have far more power, accelerating the bicycle to 25mph. They also charge faster 75% faster.