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Environment and energy

The e-bike revolution

07 Jul 2020 James McKenzie
Taken from the July 2020 issue of Physics World. Members of the Institute of Physics can enjoy the full issue via the Physics World app.

Electric bikes are all the rage, but James McKenzie wonders if the future lies with a minimalist kit that can be retrofitted to an ordinary bicycle

Ortis Deley with a Cytronex-adjusted bike

We’re finally, cautiously, emerging from the global lockdown designed to halt the spread of COVID-19. It will be interesting to see what real and lasting changes the pandemic brings, but as I mentioned last month, I suspect our travel and transport habits will never return to pre-lockdown ways. The UK government already said in May that it would invest in “pop-up” bike lanes with protected space for cycling as well as wider pavements and safer junctions. Cycle and bus-only corridors were also due to be created in England “within weeks” as part of a £250m emergency travel fund.

As UK transport secretary Grant Shapps put it, social-distancing requirements mean that even if public transport reverts to a full service, there will be an effective capacity for only one in 10 passengers on many parts of the network. ”Getting Britain moving again is going to require many of us to think carefully about how and when we travel,” he said. Shapps claimed that some parts of the country had already seen a 70% rise in the number of people cycling to work or the shops, adding that “when the country does get back to work, we need those people to carry on cycling and walking, and to be joined by many more”.

There’s also been good news for fans of motorized scooters, or “e-scooters”, which are basically two-wheel scooters with an electric motor added. Currently illegal in many countries, a trial e-scooter rental scheme is set to begin in Birmingham this month. It will let the government explore the benefits of e-scooters and possibly make them – and other novel forms of transport, like Segways – legal on British roads. It won’t be simple: a similar trial in San Francisco led to angry “e-scooter wars” between residents and commuters riding these devices illegally on pavements.

Wheel of fortune

I already own an Inmotion V3 self-balancing electric unicycle, which has a gyrostabilized wheel and looks a bit like a Segway. Problem is, you’re not meant to use one of these on the road or pavement, only on private land. During the lockdown, it’s therefore been gathering dust in my garage and instead I’ve preferred my old-fashioned pedal bike, which I can use legally on the road and keeps me at a safe distance from other people. But are ordinary bikes a realistic way forward – especially for those who have to travel long distances or up steep hills?

The future, I think, lies in electric bikes. Sales of e-bikes are rising, currently totalling about 50,000–60,000 a year in the UK. That figure’s dwarfed by conventional bike sales of more than three million, but the evidence points to serious e-bike growth over the next 30 years, according to the car-part and bike retailer Halfords. But, wow, these dedicated e-bikes are expensive. Bosch will sell you one for £2000, while its top-of-the range model with full suspension will set you back more than £6500. I’d be nervous about leaving one of those locked up anywhere on the street.

With a battery fully integrated into the bike’s frame, they’re heavy too. I suspect there will be a limit to how many customers will want to pay for something that costs more than a decent used car. The high price was also one of the problems that stalled sales of Segways in the early 2000s and why other firms stole a march with other self-balancing scooters that had cheaper and better designs. As Lotus cars founder Colin Chapman famously said, the trick is to “simplify, then add lightness”.

I bought a simple piece of kit that I retrofitted to my existing pedal bike.

That’s why I bought a simple piece of kit that I retrofitted to my existing pedal bike, turning it into an e-bike at much lower cost. I’d first seen the device on TV’s The Gadget Show a few years ago, watching in amazement as presenter Ortis Deley fitted his ordinary bike with a C1 lithium-battery-powered kit from the UK firm Cytronex and then raced British hill-climbing champion Dan Evans over a 7 km uphill course. The combined battery and motor controller are disguised as a water bottle and attached to the bike frame, giving Deley an additional 250 W of power via a motor fitted to the hub of the front wheel. Although Deley didn’t beat Evans, it was very close (he might have won if UK regulations didn’t prevent an e-bike going faster than 25 km/h).

Uphill challenge

I’ve had a lot of fun with my new e-bike conversion. I’d previously tried cycling to work with my ordinary bike but the uphill sections were a killer and I always ended up a soggy mess at the office. But now I found myself passing local, hardcore Lycra-clad cyclists up hills in my business suit without even breaking sweat. And thanks to the water-bottle kit, no-one knows you’re on an e-bike. Even better, when I’ve reached my destination, I can simply lock my bike, unclip the “bottle” and take it with me.

The Cytronex kit gives me roughly 40 km of assistance range, helping me to build up my fitness – I save the joules for the hills or when I’m tired. The kit and motor, which add just 3.6 kg to my bike, couldn’t be easier to use. In fact, its inventor Mark Searles recently fitted one to a Brompton folding commuter bike and then attempted the dreaded 22 km-long climb of Mont Ventoux in southern France. Rising vertically by 1600 m, it’s a regular part of the Tour de France, but Searles completed it in just 84 minutes – on a par with the best riders in the world.

Surely that makes the Cytronex-adapted Brompton the ultimate lightweight environmentally friendly commuter vehicle. And with potentially quieter roads once the COVID-19 pandemic is over, what better way to keep fit, get to work or go shopping? As with many things, the simplest solutions are sometimes the best.

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