Easier cycling using electricity
Peter van der Linden

I want to ride my bicycle to work. It would be good for the environment, and good for me. The weather in California makes this feasible most of the year, and I can find bike paths for most of the route. There's one problem: I live about 8 miles from the office, and that's too far for me to just start doing it.

The Caltrain service from San Francisco to San Jose is convenient for my commute, and they are "bicycle friendly" with the northmost coach on each train adapted to carry bicycles. I tried it for a while. Bike a mile to the Caltrain station, catch a train, get out at Sunnyvale station, ride the last couple of miles into work. But you have to follow the train schedule, not your own. On one occasion, the train never arrived and I had to ride the whole way, arriving hot, sweaty, and late.

Problem Solved

Electric-motor-assisted bikes are just feasible today, for short distance runs between charges (say a dozen miles). They have not yet benefited from high volume production or intensive R&D. Those improvements are still to come, but leading edge adopters can use them now. With his first pay packets of 2008, my intern, Sean, bought an electric bike. It was a complete assembled bike for about eleven hundred dollars. Sean invited me to ride it round the parking lot. I was hooked instantly. There are many reasons to love an electric bike: the "gadget factor", the free exercise, the low cost of use, and the knowledge that you're shunning oil (and all the desperate problems that political misjudgment has brought on our heads).

Most off-the-shelf electric bikes don't look neat. They have bulky battery packs, that appear to be wedged on as an afterthought. There are currently just two mainstream American bicycle manufacturers, Giant and Dahon, with better looking electric models, selling for about $1800. But you can't actually buy one. At the time of writing (summer 2008), the manufacturers can't produce them fast enough, and there's a waiting list.

The Dahon MuP8 folding electric bike,
with ugly battery pack spoiling the clean lines

(electric and folding - this is off the scale on "gadget factor")

Update my regular bike

My regular bike suits me fine. It's a Globe "City" model, a classic of practical "sit up and beg" cycling. I rarely ride off-road, and don't need the added weight of front or rear suspension. (Update: there's a lot of weight on the back of this bike, and my next model will have rear suspension).
Nothing special, but it's equipped just the way I like, with mudguards, dynamo (battery-less) lighting, a luggage rack, a chainguard, and other conveniences. I negotiated the price down to $300, on the last day of a "going out of business" sale at the Globe shop on Castro Street in Mountain View.

It was clear that the most satisfactory approach would be to retro-fit an electric motor to my existing bike. You could buy a complete kit, such as the $650 Go-Hub kit, or this one, or this, or these, but I wanted to choose individual components to optimise for appearance and weight. A bit like the audiophiles do, with their stereos.

Most of the components came from Rob Means, who is a knowledgable, friendly and effective advocate for green transport technology. This is Rob's website.

Choosing components

These are the components you need to add, to make a bike electric:

  • an electric motor, typically fitted to replace the hub in the front or rear wheel.
  • one or more battery packs
  • a controller unit to switch the power to the motor (you don't want to route that through the throttle), and to turn things off if a heat sensor in the motor trips.
  • a hand-operated throttle, to tell the controller how much juice you want.
  • a wiring harness to tie all this together, plus connectors, gaffer tape, velcro etc.
  • a battery charger - this is more than a voltage transformer; it has circuits to monitor each cell, and not deliver too many amps too fast.
Your main choice is the power rating of the motor. The more power, the more speed, but also the bigger (and heavier and more expensive) battery pack you need. I chose a 250 Watt motor from Brushless Motor Corporation, because of its light-weight - only 9 lbs.

This is a "brushless" motor, meaning that commutation (dragging the rotor around) is done electronically, via motor shaft position-sensing and power transistors.

Brushless motors are more expensive, but more reliable as there are no wearing parts.

More importantly, this is a geared hub motor with a freewheel inside. The freewheel means that when the motor is not powered there is no magnetic drag on the wheel. The freewheel means that when you pedal, you don't have to turn the motor, only the outer hub holding the motor. (Although a freewheel eliminates the possibility of regenerative braking, which you would otherwise get by using an updated controller). (More detailed explanation here). So when the electricity is off, you are only pedaling against the weight, not the magnetic drag.

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