It was a lovely afternoon many summers ago when I was enjoying a bicycle ride beside the river with my children. One of the kids decided a race to a tree in the distance would be a good idea, and we all sprinted to the target. When we stopped, I had one child missing. Back in the distance I could see my youngest daughter in tears sitting beside the path.
The trauma still haunts her to this day. The dreaded chain derailment had occurred when we started our dash. She had tried to resurrect the linkage and now had grease over her hands – which she had smeared over her face to try and wipe away her tears.
“Why do bikes have chains?” asked my daughter, wanting the answer to be something incredible that would justify her oil-stained face. “Well,” I started, “before the chain, direct drive bikes, like the penny-farthing, had to have large drive wheels which made them unsafe. From 1885 the ‘safety cycle’ was introduced with sprockets and a chain that made the bicycle safer with smaller wheels and also made it the most efficient means of transport with an energy conversion rate of 98 per cent.” She wasn’t convinced. “I want a bike without a silly chain!”
I can finally deliver some good news to my daughter.
A German company, Schaeffler, has just revealed an innovative new drive system for electric bicycles that removes the chain from the system completely. Just like a diesel-electric train uses a diesel engine to generate electricity to power electric motors, we now have the same concept in bicycles with humans acting as the power generator. The crank mechanism stands alone as an electricity generation device to drive an electric motor based in the wheel hub or hubs.
The first question that came to my mind was efficiency. How does this method compare? As it turns out, quite favourably! The new ‘bike-by-wire’ system, Free Drive, developed with two-wheel electric drive specialist Heinzmann, is only 5 per cent less efficient than a traditional sprocket and chain configuration.
So if it is less efficient, why bother? The main goal was not efficiency but instead design freedom. My belief is that this will be as substantial a game-changer for the e-bike revolution as using carbon-fibre was for the shape of bicycle frames.
In the past, every different configuration of a traditional bicycle or recumbent or three or four wheeled version had to solve the problem of connecting cranks and a chain back to the rear wheel or wheels. In some configurations, a ridiculously long or multi-chained approach was required for that mechanical connection. Free Drive allows a designer to place pedals at the most convenient location for the rider and place motors in one or more wheel hubs. Imagine a bicycle with a powered hub at both the front and rear wheel. Or a trike that has both rear wheels powered by motorised hubs. For the best pedal efficiency, a preferred cadence can be set and the hub will vary the power generation – and hence the resistance to pedalling – to suit. It wouldn’t matter if you were going up hill or down dale, you could pedal at a constant tempo. If you were generating more power than required, the extra power would go in to the battery. As with cars, all system components communicate with each other via a CAN connection.
After more than ten years, I can finally give my daughter what she asked for!
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