Electric BMX Has Pedals That Can’t Be Pedalled


We don’t mind it that there’s no chain connected to these pedals. At least there’s still somewhere to put your feet and our legs are too long to comfortably pedal this size of bike anyway. As you can tell, the added hardware takes care of locomotion using an electric motor.

The first step in this project was to find a steel bike frame to make welding a bit easier than it would be for aluminum. From there the paint was sanded at the attachment points and mounting brackets were fabricated from some angle iron. The rear mount houses a 500W 30A AC motor which uses a chain to drive the rear wheel. A specialty hub was found which allows the added sprocket to be installed on the left side of the rear wheel. Some threading issues prompted [Michael Monaghan] to come up with a method of adding a slot to lock the part in place.

Near the front fork the second mounting bracket holds the batteries; a pair of sealed lead-acid units. The speed control mounts on the top where the rider has easy access to it. The finished bike can get up to thirty miles per hour with a range of up to twenty miles between charges.

If you want your own electric bike on the cheap you can try building one from a salvaged washing machine motor.

30 thoughts on “Electric BMX Has Pedals That Can’t Be Pedalled

        1. Well, to be fair, yes it can be done such as on large trains, but I think the difference is the scale of the project. Yes it can be done, but it would be quite the challenge to make it efficient on a small scale.

  1. On one hand, I would be proud of this if I built it myself. It requires a variety of practical skills. On the other hand, where’s the hack? It’s basically an inferior version of something that has been commercially available for years. The throttle is just a potentiometer. Let’s see some schematics for an Arduino-based motor controller with regenerative braking.

    1. ” It’s basically an inferior version of something that has been commercially available for years”

      Isn’t this pretty much the definition of a hack–an ad hoc, DIY version of something that would otherwise require purpose built equipment?

      1. To be called a hack, I would expect a project to demonstrate some novelty or creativity. This could mean repurposing something or just giving it a weird feature not found on commercial products intended to do exactly the same thing. But to copy a commercial product without a single innovation? Admirably practical, perhaps, like my garden fence made of salvaged lumber and shelf brackets. But is that a hack people want to read about?

        1. This is hardly copying commercial electric bicycles. Most ebikes that you would buy use a motor that is laced into the wheel with the spokes (called a “hubmotor” for obvious reasons.) And even the chain driven ones usually have the motor mounted right next to the wheel axle, not right under the seat. And none of the commercial ones I’m aware of use a BMX frame, they’re all cruisers or mountain bikes.

        2. instead of complaining about what is and isn’t a hack, why don’t you submit more of your hacks, because apparently you have better hacks then this article, and i’d like to see them. even if they are just a fence.

  2. is that really an ac motor? this comment from the site “Once the project was done, I fine tuned the motor by cleaning the com and playing with timing to optimize power.” makes it sound more like a brushed dc motor. also the motor looks like it has 2 wires, single phase ac motors would be a poor choice for this kind of load.

  3. Reading his blog I wondered which third world country he is from. What a shock to see SoCal! Technical English is required in his discipline. What the hell is an “axial motor controller”? A hub motor? The pot is a thumb lever type for the motor controller. Also 20 inch tires at 30 mph is scary and very bumpy. Chain must whine loudly on the tiny sprocket. What’s wrong with using the right side drive. Gear it down a bit and make it legal (USA).

    1. There are Federal guidelines for differentiating a “motorized bicycle” (requires no license, can be ridden in bike lanes) from a “moped” (requires a license, must be ridden in motor vehicle lanes.) The Federal guidelines aren’t law, but many cities have adopted them as law. Among the requirements to be considered a motorized bicycle are functional pedals and a top speed (under its own power) of no more than 20 mph. There’s also a motor wattage limit, but I think it’s pretty high.

  4. Nice work.

    I wonder if it’s worth it to add some sort of a power generator to charge the batteries while it’s on the move. Perhaps pedal-powered or sacrifice some speed and use the chain to turn an alternator or something. Would the added weight simply offset any potential range increase?

    1. Pedal powered generator is a good idea. Not sure of the losses on that, but adding an alternator into the chain drive will be too ineffecieint and would cause a net loss in power.

      An intelligent charge controller would allow power to be put back into the wheels when going downhill or braking for example.

  5. I would be cautious building something like this in the US. I don’t know what the laws are for electric vehicles but I do know that there is a fine line between bicycle, moped and motorcycle here in Montana. I have a 49cc 2 stroke on my bike and it is barely considered a bicycle. Anything larger and it needs to be registered as a motor vehicle. Also there is a requirement for the bicycle to be able to be propelled by human force, e.g. pedals. Again, could be different because it is electric. If you want to build one yourself I advise checking your local laws first.

    1. In California – electric bikes do not have any licensing or registration requirement so long as they go less than 20mph, and are less than 1000W. You must wear a helmet during operation, which is not the case for regular bicycles. In California, there is no class of combustion-driven bicycle that qualifies as a “bicycle”. Source: hacker with DUI.

  6. Not gonna knock the guy who built it, it’s fairly clean. But this is NOT the best or even an extraordinary example of an electric bike conversion.
    Head over to http://endless-sphere.com/forums/, then find some of the crazy stuff that they do, brushless RC motors, the whole nine yards.
    In fact, THIS is what you need to post. I’m putting it in the tip line:

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