Converting your bike to an e-bike: why you should and when you shouldn’t

Ten years ago, I was lucky enough to work for an employer who offered a loaner bicycle program to its employees, and I took the opportunity to buy a Brompton folding bicycle. This London made machine is probably one of the most efficient folding cycles on the market and has the useful feature of being practical for long journeys rather than just a quick run from the train. A 3-speed hub gearbox is fine for unhurried touring, but unfortunately my little backrest was always a bit of a pain on the hills. So, around the start of the pandemic, I again splashed out and bought a Swytch electric upgrade kit for this one, and after some logistical and life upheaval, finally got it installed on the bike. I’ve ridden a few e-bikes but never had my own, so it’s time to sit down and analyze the experience. Is an e-bike something you should or shouldn’t have?

A box of bits becomes an electric bicycle

All parts of a Swytch kit. From the Swytch assembly manual.

Swytch sells their kits through crowdfunding rounds, so I was on a waitlist for a while and got a pre-list price on my kit. It took a while to arrive, much longer than expected in mid-2020 due to the pandemic, finally delivering in February last year. It came in a modestly sized carton that would be easy to carry on the Brompton’s rack, neatly packed containing a new front wheel with motor, along with the battery and all miscellaneous parts.

Installing the kit shouldn’t expand the capabilities of a Hackaday drive, with probably the trickiest part being positioning a Hall effect sensor near the crank. The kit works by providing motor assistance as you pedal, so part of it is a set of magnets on a plastic disc with various attachments for different cranks and pedal sets. The Brompton front wheel is removed and its tire and tube transferred to Swytch’s, which is then put on the bike. Once the magnetic disc and the Hall sensor are attached, the cables follow the existing ones and emerge at the handlebar where a solid support for the battery box is installed.

First impressions of the Swytch kit

The motor is a compact unit, more than I expected.
The motor is a compact unit, more than I expected.

The battery also contains the motor electronics and driver, as well as provisions for the brake sensors and a hand throttle, which I hadn’t ordered. My kit is painfully road legal in the UK with a pedal sensor, software limited 250w power and a top speed of around 15mph. I could have ordered it with no limits and all the extra toys to make it look more like a small electric motorcycle but even if I can remove the soft limit I can’t deny the risk of a roadside inspection and fine if I was doing it.

Swytch offers two batteries in 30km and 50km range sizes, and of the ones I’ve purchased, the larger one. After charging it, I turned it on and clipped it into the holder. Ready to test a new toy on the concrete apron behind my hackerspace!

The Swytch battery comes with some controls on the top, the main function of which is to vary the amount of power assist. This is best described in terms of who is responsible; at maximum assist it’s the bike that pulls and all you have to do is move the pedals, while at minimum it’s a handy aid that softens the effort and makes cycling a less tiring exercise while leaving you definitely in control.

The Swytch battery on the Bromptoon handlebar.
The Swytch battery on the Bromptoon handlebar.

There is a small catch: under certain conditions, the engine vibrates instead of starting smoothly. From my experience with AC motors for Hacky Racers and other machines, I’m guessing it comes from motor feedback to the controller via back EMF sensing rather than hall effect devices, so what I’m seeing is a temporary loss of this return. It is usually quickly cured by stopping pedaling and restarting after the motor is shut off, which does not significantly impede progress.

I used the bike a lot for general riding, but also set out to work out the real-world achievable range with some longer cross-country testing with it in low-power mode to help rather than replace my cycling. As expected, I never managed to crack 50km, but I got pretty close.

My routes weren’t ideal with a few inclines and on one of them strong headwinds the day I did it, but I still achieved between 40km and 45km which I consider not too bad for a 50 km battery. Once the power is exhausted, there is noticeable drag from the motor, but this does not render the bike unusable.

So what does an electric bike look like?

The description of a Swytch kit aside, it’s time to give some more general impressions of e-bikes based on using an e-Brompton as everyday transportation. There’s even a ride angle, as the bike is now an all-wheel-drive vehicle. How does this change the driving experience?

The electric Brompton in all its glory
The electric Brompton in all its glory

The first impression of a daily e-biker may seem obvious as it is now much faster. I could hit mid-teen speeds before, but only with a bit of effort, now they’re within reach at all times. It’s great for getting from A to B, but I’m also very aware that I can get into trouble much faster. Oddly enough, I found myself riding much more carefully, especially in town where there are pedestrians and traffic.

With the power supply in the front and the pedal in the back, the bike is now a two-wheel drive vehicle. Two-wheel drive motorcycles are so rare that they are limited to very few small production models, but thanks to my friend Russ’ electric minimoto conversion, I had the rare opportunity to ride one at the EMF 2018.

It was especially safe on gravel roads at EMF camping, but suffered from a pant-filling moment on start-up as the front wheel spun while the rear had traction. By contrast, the momentary delay afforded by the Swytch pedal sensor system was enough to ensure the Brompton was moving before power got to the front wheel, ensuring that even on loose surfaces there was never unexpected slippage.

The resulting two-wheel drivetrain makes a noticeable difference on surfaces such as grass and loose gravel that would normally challenge the Brompton, and when you give it a spirited ride on tarmac, the extra traction can get me out of trouble. . Getting addicted to fast tight corners with rear wheel slippage is dangerous though, because when the inevitable happens and the front wheel doesn’t have the buy to pull me through, I can see the results could be painful. The sight of a middle-aged woman exorcising her teenage BMX dreams on a folding commuter bike must be fun to watch, but at least I was having fun.

So, should you go electric with your bike, or is it a bit useless? After all, it’s not quite cheap and you have to pay for a bike on top. The answer is if you are fit or only run short distances, it may not be essential. But if you’re covering medium distances, and perhaps more importantly if you’re riding places where it’s important not to arrive in a sweat, then an e-bike is a worthwhile upgrade. The Brompton isn’t my main bike, so I use it for trips where I have to take it by train or car, and I like the Swytch kit for the extra reach it gives me while still riding. preventing him from looking overworked.

Oddly enough, there is one use case that an e-bike would not be suitable for, and that is riding longer distances. The idea of ​​riding more than a short distance against the added drag of the engine isn’t appealing, so the Brompton is now a bike with an effective maximum range of 50km. I frequently use my everyday bike for longer trips, but for your one bike, it’s worth considering.

E-bikes aren’t for everyone, but maybe 2022 is the time to give them a try?

Back To Top