Wednesday, September 26, 2012


So a couple of months ago I went back to Mexicali, Baja California, Mexico. Which is not in SoCal even though most people think that whenever I mention "Baja California" -_-. Anyway, I stayed there for a few days only so I could attend my sister's high school graduation (she's going to Princeton! wooo). During those days, I learned that one of my friends, Juan Bustamante, had a cousin who was throwing away a tiny motorcycle that wasn't working anymore. I went over to see if I could fix it or at least figure out what was wrong. The first things I checked were the battery and the motor. I don't really have any tools back home besides a screwdriver and a wrench so there wasn't much I could do but luckily my Juan had just bought a multimeter so we probed the battery and found that the 18v battery only had 4v across it. Which made sense considering the lead acid battery had not been charged in about four years. To check if the brushed DC motor still worked I had to place enough voltage across it make it overcome its own inertia  and have it start spinning. I didn't have a variable power supply so instead we got eight AA batteries and taped them in series to make a 12v "pack". The motor did spin so I decided to keep it for a future project (or maybe just to take it apart and use its stator). After we diagnosed the problem, Juan decided that he was never going to use it anymore so he offered to give it to me. I was unsure about whether or not I should bring the pocket bike with me back to MIT considering that it's more than 2500 miles away and it might be a problem to bring on the plane. So I did a quick Facebook post to see what my friends thought about it.
Clearly, they thought it would be awesome if I brought it and motorized it so I could race against Adrian who built his own electric pocket bike, MilliCycle

Mount without pocket
The first thing I had to do was figure out how to mount the motor onto the frame. The original motor was a brushed motor and it had its mount holes on the bottom so the frame had a mounting plate for it. I decided to take advantage of this so I took some scrap metal I found in N52-318 (room where the MIT Electric Vehicle Team meets). It was an aluminum C-Channel so my ex-roomie Roberto used the bandsaws and drill presses in D-Lab to help me cut off one of the sides and make mounting holes for both the frame and the motor. We later realized that we did not take into account the aluminum between the motor and the pulley so we had to go down to MITERS to mill a pocket for it.
Motor mount with pocket (it's on the other side)
motor controller attached with more scrap aluminum
I wanted TinyCycle to be way more powerful than RailScooter so I used a motor twice as big as the one on RailScooter. It's a Turnigy SK3 6374 Brushless Outrunner. It's 192kv and has a resistance of .016 ohms. More importantly, it has more power than I really need on such a small vehicle but meh, it should be fun. For the battery pack I soldered two custom 5s2p battery packs in series. This means I have a 33v pack on TinyCycle; much bigger than the 24v battery pack on RailScooter. The motor controller is also different. RailScooter uses a sensored kelly controller whereas TinyCycle uses a sensorless 250watt jasonTroller. The jasonTroller was clearly TinyCycle's limiting factor so I plan to swap it for a more a 500watt jasonTroller. Hopefully that will give me enough power to do wheelies!
bicycle mount in D-Lab

battery pack sketchily mounted with zip-ties.

TinyCycle's Maiden Voyage with the 250w controller

Garage Run with  a scooter, two go-karts, a quadrotor, and a tiny motorcycle
So many little EV's!
Garage Run from the Shane's quadrotor's point of view
Cute British Accent Asian Girl
So apparently, tinyCycle is a chick-magnet. A couple of TDC brothers and I were riding it around dorm row last Saturday night around 1am. Which is also the time MIT frat parties are over. Several girls walked over toward us and started asking me about tinyCycle. 
I even got the above girl's phone number :) 


  1. Hi Victor,

    Which speed controller you end up using and what modifications have you done to it?
    I have a goped esr 750 that was modified with the turnigy 6374-192kv and 18650 cells. Now the biggest problem was to find a reliable ESC. Tried RC stuff and Chinese bike controllers and nothing worked more than couple of days/weeks until it died or cought on fire.


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  3. Hi Victor, i'm making an electric competition motorbike with my university team and i would like to talk with you to ask you some advices.

  4. Hi victor- I'm desperately searching for that girl in your picture. Is there anyway you can contact me? All the best...

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