TECHNICAL
Are friends electric? With electric bikes gaining in popularity, author Richard Peace explains the background and what to look for if buying one
I
n very basic terms, electric bikes allow you to add power from a small electric motor to your pedalling effort; they are not mini-electric motorcycles as they still require some pedal input. Effectivley, they make pedalling easier — especially up hills, into headwinds and with heavy loads. Subject to a speed limit of 15mph — though you can use pedal power alone above this limit — and a motor rating of 250 watts, they are treated exactly the same by UK law as non-electric bikes. There’s no need for any red tape whatsoever. How long have electric bikes been around? You might think of electric bikes as being a phenomenon of the last few years, but the 19th century saw an electric machine produced by Humber (a tandem pacer used in the Bol d'Or 24-hour paced track race in 1899 in Paris). The 1920s and '30s saw a number of designs designed for public use, one example being the EMI/ Philips system. Petrol power overshadowed the idea of electric bikes in the post-war years but the oil crises of the 1970s saw an increasing number of designs come and go (including the wellknown C5). The 80s and 90s also saw steady technological progress, meaning a reduction in weight of electric bikes and extending battery range. Such has been their increasing popularity on the continent over the last decade they now account for a significant proportion of bike sales — around one in four bikes sold in the Netherlands is electric. Aren’t they expensive? Models start at a few hundred pounds, but £1,000 seems to be the starting benchmark for good quality bikes from well-known firms. They are eligible for the Cycle2Work tax subsidy in the same way that non-electric bikes are. What designs are there? There are two main designs, based on how motor power is applied: ■ Pedelecs — here the power is
MOTOR This is a rear wheel hub motor but other options include front wheel hub, or around the pedal axles. The motor also needs control electronics which may appear as a small separate box on the bike or, as here, may be hidden away, usually inside the motor casing.
activated by your pedalling motion, so as you pedal you feel the motor power magically pushing you forward. They tend to be the most efficient systems and give good smooth assistance over a wider speed range as they are working in every gear. ■ E-bikes — these usually use a throttle, but the very least you will have to do is spin the pedals round (though not necessarily put any effort in) to activate the power. Bikes can also be classed according to whether they have a ‘crank motor’ (usually located near the bottom bracket axle and driving
through the chain) or a ‘hub motor’, located in the wheel hub (front or rear). Crank motors are usually more reliable but more expensive and may not be as good at speedy hill climbing as some hub motors. Where’s the technology at and will it continue to improve? As electric bike technology has progressed their sales have continued to grow. Here’s a summary of electric bike technology to date: What batteries are used and what mileage do they achieve? Most electric bikes use lithium
38 London Cyclist June-July 2011
038040_tech_FINAL.indd 38
09/05/2011 22:27