audrey xie
not a jack of all trades, nor a master of one. i prefer just being a lazy bum.
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Act First, Think Later — EV Moped Conversion pt. 2

Anxiety, the next gumption trap, is sort of the opposite of ego. You’re so sure you’ll do everything wrong you’re afraid to do anything at all. Often this, rather than “laziness” is the real reason you find it hard to get started. (Robert Pirsig, Zen and the Art of Motorcycle Maintenance)

Disassembling the moped was fun and all. But now came the difficult part, putting it back together. I started off with what I believed was the most simple part, replacing the original wheel with the hub-motor-laced wheel. The hub motor is just your average brushless DC motor (BLDC). The permanent magnets are located on the rotor, while the electromagnets are on the stator. Electricity charges the electromagnets on the stator to rotate the rotor. The only thing slightly different from a typical BLDC motor is that its axle is more reinforced.

The hub motor that I was working with directly drives the back wheel and has a max power of 3kw. The top speed is hard to estimate because I’m not sure what the final weight of the moped will be. Either way, the hub motor was laced using a single-cross pattern, which is the generic lacing pattern for larger hub motors and wheels.

Hub motor laced into wheel

Original wheel

I’ve realized that my way of working follows the “act first, think later” methodology, which often leaves me in bad situations. Case in point, I needed to remove the inner tube and tire from the original wheel and install it on the new wheel. Since I didn’t have the proper tire replacement tools, I decided that a pair of flathead screwdrivers would do the job well enough. Removing the inner tube and tire proceeded smoothly, but when I tried installing them on the new wheel, that’s when everything went haywire. First, the metal flatheads did a good job of scratching the black paint on the wheel. Second, the tire just could not fit onto the tire. It was only later that I realized, you can’t install a moped tire the same way one would install a bicycle tire. A quick internet search would have saved me the three hours spent prying the tire onto the wheel. Third, flathead screwdrivers are sharp and they will easily tear through butyl rubber, the stuff that inner tubes are made of.

The tire doesn’t fit

It turns out that there is a much smarter and much easier way of installing moped tires. Oddly enough, it involves Windex and zip ties. You first deflate the inner tube, then place it inside the tire. Next come the zip ties, compress the tire as much as possible before tying a zip tie. Repeat this step multiple times. Finally, spray an excessive amount of Windex on the wheel and tire. This time around, it was much easier to install the moped tire. Cut the zip ties and inflate the inner tube. The wheel should be good to go now, that is if you didn’t accidentally damage the inner tube. Unfortunately I did, so I had to remove the tire, patch the puncture wounds on the inner tube, and repeat the process.

Zip ties

Zip ties and wheel

Tire installed on wheel

Wheel on moped