Electric Pennyboard

 In college I used a Meepo electric longboard to get around campus quickly. Up until I actually needed a car to get to a summer internship it was the perfect transportation. I could get to my 11am robotics class a half mile away from my dorm within 5 minutes and the board was small enough that I could bring it into class with me instead of locking it up outside to prevent it from being stolen. The battery was the right size to last two days in case I forgot to charge it and it had a top speed fast enough for it to be effective for games of 'tow rope' in the quad.

I really liked that electric longboard; however, I had some ideas to improve the design for my use case. The biggest problem I had with the longboard was that it was too big to comfortably carry. There is a handle in the middle of the board that works well until you have to walk through a crowd and accidentally hit people with it because the board sticks out 2ft in front and 2ft behind you. I also tried carrying the board by the front truck and dragging the rear wheels on the ground but over rough terrain this doesn't work well. My ideal carrying configuration is to have the board be short enough such that when I hold the board by the front trucks it doesn't touch the ground.

Then a friend of mine got a pennyboard to go around campus. This small form factor ticked all of the boxes for me except for being electric - I got too used to not having to pump the board and having brakes in case I get going too fast. I grabbed a pennyboard for myself with a plan to electrify it.

For my first attempt I got a VESC 4.12 and a 3548 outrunner. I modified the rear truck of the pennyboard to hold the motor and drive one of the wheels through a two stage gear and belt reduction. I thought this was a pretty neat low profile design but after putting the board together I realized that since the motor did not have hall sensors there was not enough starup torque to get the board moving reliably. The motor is also a little under powered and was not able to reach as fast of a top speed as I would have liked.

I put this project on hold for 2 years until another friend graduated and got an upgrade from his Meepo to a nicer board. Since the battery was dead he gave me the trucks and electronics. I found that the Meepo electronics fit in the pennyboard and the trucks were hole for hole compatible. I just had to build a 10S lithium ion pack and create an electronics enclosure for the board! Building a pack was very straightforward - I just found some 18650 cells, a BMS, some nickel strips, and borrowed a spot welder from a friend. For the enclosure it was slightly larger than what could fit on my Prusa Mk3s so I took some filament and the file to work where there is a Sidewinder Artillery with a larger bed.

I gave the electric pennyboard some initial testing and my first impression is that this is dangerous. It is very easy to accelerate or stop fast enough to throw the rider off of the board due to the shorter stance. I ended up having to run off the board several times while stopping and did a few accidental rear wheel wheelies while accelerating fast. After using the board consistently over a week most of these problems went away as I got better at riding the board. I still don't trust myself to go much faster than a running speed that I can bail from but it has become a fun way for me to chase robots around the office. I am beginning to think that if I had this board in college it would have made a fun way to get around classes slightly more practical.