Electric Bicycle Conversion

Once upon a time I took it upon myself to create an electric bicycle. At the time I was still doing an daily commute to work 16km both ways, and thought it would be a good alternative to a car. The point was also to learn about bicycle mechanics through practice and have some fun with tools.

I picked up a donor bike based on the frame geometry. I like steel bikes with straight thin tubes and find the classic look with a horizontal top tube most aesthetically pleasing.

Most of the assembly work was done at Tumeke cycle space, a communal bicycle workshop based in Auckland. They have all the tools, lubricants, bicycle stands and donated spares available for people to fix their bikes. They share a space with Tangleball, a makerspace with lots of power tools, bench grinders, drills and heavier machinery. This resource is great and available for people to use, which I’m thankful for in many ways, since this isn’t the only project that benefited from their existence.

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The condition of the donor bike was abysmal. It was rusty and someone spray painted it with horrible cheap rattle cans.

After stripping the paint, the tubes revealed themselves to be covered in surface pitting. I didn’t care to spend money on a chemical bath, so I ground away the rust.

The donor bike was one of those wana be “mountain bikes” which are really just geared city cruisers with mtb tyres. I wanted to give it a road bike look, so a classic quill was installed.

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The motor that I got was a Bafang 350w center mounted system. I really liked the way it slots into the frame and gets hidden away between the cranks and doesn’t require to be laced into a wheel.

The installation was super easy, with no special tools necessary. I used mtb tyres off my other bike. They use disk brakes, and I had a fork with a disk brake tab, but the frame wasn’t compatible, and I didn’t want to cut + weld to make it work, so I opted out for no rear brakes to start with.

Gears were wired in with a classic lever shifter with 5 speeds on the rear. There is no need for gears in electric, since it’s a brushless motor with variable speeds, but it would help should a need to pedal arise (when the battery is flat for example).

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After the bike was built, the progress slowed down, as I had to move house and I no longer had a job to fund my DIY. Batteries are expensive to buy local, as it’s still a niche product in New Zealand, and ordering from China has its risks for lithium batteries. I did some tests with led acid PSU cells and was able to test ride the bike after getting help from my father with battery testing and construction, but was not a viable solution due to weight and capacity.

I see very few people riding electric bicycles around Auckland. Maybe it’s because New Zealand already has a culture of cycling and electric is just too expensive and fiddly for those who already cycle and don’t mind the occasional hill. Charging requires delicate battery care, despite the usual advertized “plug and play” that comes with cheap chargers that ruin battery cells. Regardless, I think cycling as a mode of commuting is more than commuting and skipping the distance, it’s exercise, it’s difficulty, it’s getting sweaty, it’s taking cathartic showers when you get there. Electric is different, some may say it’s cheating, some may say it takes the soul out of cycling. I think it’s necessary technology to drive personal transportation tech and battery tech further.

Unfortunately I had to abandon the project, never really getting to ride it, and sold off the motor kit. The project however taught me a lot about bicycle mechanics, maintenance and anatomy of a bike. It fulfilled the need to build I had when I’ve taken up the challenge.

This is the most complete it looked without temporary wires and battery: