It sounds like a rhetorical question that a Midwestern engineer might ask, something on the order of ‘can you fix this bad PCB spin?’ [Tom Stanton] sets out to answer the title question and ends up building a working e-bike with a drone motor.
You might be thinking, a motor is a motor; what’s the big deal? But a drone motor and a regular e-bike motor are made for very different purposes. Drone motors spin at 30,000 RPM, and an e-bike hub motor typically does around 200-300 RPM while being much larger. Additionally, a drone motor goes in short spurts with a large fan blowing right on it, and an e-bike motor can run almost continuously.
The first step was to use gears and pulleys to reduce the RPM on the motor to provide more torque. A little bit of CAD and 3D printing later, [Tom] had a setup ready to try. However, the motor quickly burned out. With a slightly bigger motor and more gear reduction, version 2 performed remarkably well. After the race between a proper e-bike and the drone bike, the coils were almost melted.
A decade ago I was lucky enough to work for an employer that offered a bicycle loan scheme to its employees, and I took the opportunity to spend on a Brompton folding bike. This London-made machine is probably one of the more efficiently folding cycles on the market, and has the useful feature of being practical for longer journeys rather than just a quick run from the train. A 3-speed hub gearbox is fine for unhurried touring, but sadly my little folder has always been a bit of a pain on the hills. Thus around the start of the pandemic I splashed out again and bought a Swytch electric upgrade kit for it, and after a few logistical and life upheavals I’ve finally fitted it to the bike. I’ve ridden a few electric bikes but never had my own, so it’s time to sit down and analyse the experience. Is an electric bike something you should have, or not?
A Box Of Bits Becomes An Electric Bike
Swytch sell their kits via crowdfunding rounds, so I’d been on a waiting list for a while and got an early-bird price on my kit. It took quite a while to arrive, much longer than the expected time in mid-2020 because of the pandemic, finally being delivered some time in February last year. It came in a modestly-sized cardboard carton which would be an easy carry on the Brompton’s luggage rack, containing neatly packed a new front wheel with motor, as well as the battery and all sundry parts.
Fitting the kit shouldn’t stretch the capabilities of a Hackaday reader, with probably the trickiest part being the positioning of a Hall-effect sensor near the crank. The kit works by providing a motor assist when you pedal, so part of it is a set of magnets on a plastic disk with various attachments for different cranks and pedal sets. The Brompton front wheel is removed and its tyre and tube transferred to the Swytch one, which is then put on the bike. Once the magnet disk and Hall sensor are attached, the cables follow the existing ones and emerge at the handlebars where a sturdy bracket for the battery box is fitted. Continue reading “Converting Your Bike To Electric: Why You Should, And When You Shouldn’t”→
It may not look like it in some parts of the world, but electric vehicles are gaining more and more market share over traditional forms of transportation. The fastest-growing segment is the e-bike, which some say are growing at 16x the rate of conventional bikes (which have grown at 15% during the pandemic). [Jacques Mattheij] rides an S-Pedelec, which is a sort of cross between a moped and an e-bike. There were a few downsides, and one of those was the pitiful range, which needed to be significantly upgraded.
The S-Pedelec that [Jacques] purchased is technically considered a moped, which means it needs to ride in traffic. The 500 watt-hour battery would only take him 45km (~28 miles) on a good day, which isn’t too bad but a problem if your battery runs down while in traffic, struggling to pedal a big heavy bicycle-like thing at car speed. You can swap batteries quickly, but carrying large unsecured extra batteries is a pain, and you need to stop to change them.
There were a few challenges to adding more batteries. The onboard BMS (battery management system) was incredibly picky with DRM and fussy about how many extra cells he could add. The solution that [Jacques] went with was to add an external balancer. This allowed him to add as many cells as he wanted while keeping the BMS happy. The battery geometry is a little wonky as he wanted to keep the pack within the frame. Putting it over the rear wheel would shift the center of gravity higher, changing the bike’s handling. After significant research and preparation, [Jacques] welded his custom battery back together with a spot welder. The final capacity came in at 2150wh (much better than the initial 500wh). An added benefit of the extra range is the higher speed, as the bike stays in the higher voltage domain for much longer. In eco mode, it can do 500km or 180km at full power.
It’s awe-inspiring, and we’re looking forward to seeing more e-bikes in the future. Maybe one day we’ll have tesla coil wireless e-bikes, but until then, we need to make do with battery packs.
[Dave Schneider] has been chasing an electric-bike build for more than 10 years now. When he first started looking into it back in 2009, the cost was prohibitive. But think of how far we’ve come with the availability of motors, electronic speed controllers, and of course battery technology. When revisiting the project this year, he was able to convert a traditional bicycle to electric-drive for around $200.
Electric skateboards paved the way for this hack, as it was an outrunner motor that he chose to use as a friction drive for the rear wheel. The mounting brackets he fabricated clamp onto the chain stay tubes and press the body of the motor against the tire.
The speed of the motor is controlled by a rocker switch on the handlebars, but it’s the sensors in the brake levers that are the neat part. Magnets added to each brake lever are monitored by hall-effect sensors so that the throttle cuts whenever it senses the rider squeezing the front brake (effectively free-wheeling the bike), while the rear brake triggers a regenerative braking function he’s built into the system!
Sure you can buy these bikes, you can even buy conversion kits, but it’s pretty hard to beat the $88 [Dave] spent on the motor when the cost of purpose-built motors is usually several times this figure. The rest is fairly straight-forward, and besides ordering batteries and an electronic speed controller, you likely have the bits you need just waiting for you in your parts bin.
Electric bikes, and really all electric vehicles, have one major downside: the weight and cost of batteries. Even with lithium, battery packs for ebikes can easily weigh more than the bike itself and cost almost as much. But having to deal with this shortcoming could be a thing of the past thanks to [LightningOnDemand]’s recent creation. Of course, this would rely on a vast infrastructure of Tesla coils since that’s how this bike receives the power it needs to run its electric motor.
The Tesla coil used for the demonstration is no slouch, either. It’s part of the Nevada Lightning Laboratory and can pack a serious punch (PDF warning). To receive the electrical energy from the coil, the bike (actually a tricycle) uses a metal “umbrella” of sorts which then sends the energy to the electric motor. The bike drags a chain behind itself in order to have a ground point for the electricity to complete its circuit. There is limited range, though, and the Tesla coil will start ionizing paths to the ground if the bike travels too far away.
While we can’t realistically expect Tesla’s idea of worldwide, free, wireless electricity to power our bicycles anytime soon, it is interesting to see his work proven out, even if its on a small scale like this. Of course, it doesn’t take a research laboratory to start working with Tesla coils. This one is built out of common household parts and still gets the voltages required to create the signature effects of a Tesla coil.
There’s no better way of improving a project than logging data to make informed decisions on future improvements. When it came to [Brian]’s latest project, an electric bike, he wanted to get as much data as he could from the time he turned it on until the time he was finished riding. He turned to a custom pyBoard-based device (and wrote it up on Hackaday.io), but made it stackable in order to get as much information from his bike as possible.
This isn’t so much an ebike project as it is about a microcontroller platform that can be used as a general purpose device. All of the bike’s controls flow through this device as a logic layer, so everything that can possibly be logged is logged, including the status of the motor and battery at any given moment. This could be used for virtually any project, and the modular nature means that you could scale it up or down based on your specific needs. The device is based on an ARM microcontroller so it has plenty of power, too.
[Tom Stanton] is well-regarded in the maker community, and has put much effort in over the years on a variety of electric vehicle builds. In the process of upgrading his e-bike last year, he ran into some issues with the main drive pulley. Rather than rely on guesswork, he threw engineering at the problem.
The problem concerned the mounting bolts on the pulley’s hub, which would pull out under high torque. [Tom’s] initial finite element simulations had suggested the design was sound, but reality was proving otherwise. After further analysis and testing, [Tom] determined that his analysis hadn’t properly simulated the bolt pull-out condition. With this corrected in the software, it was readily apparent that there simply wasn’t enough material around the bolt holes to hold the torque load.
With the simulation now more closely agreeing with reality, [Tom] was able to correct the design. New parts were created with a strengthened mounting section, and the pulley was successfully able to deal with the loads in service.
It’s a great example of using engineering simulation tools to solve a problem quickly, rather than simply guessing and hoping things will hold up. We’ve seen [Tom]’s work before, too — like this fun backyard trebuchet build. Video after the break.