2x4 Scooter Build

Ta daa!

I just finished building 2x4 Scooter!  Its mostly functional, although the steering is a tad floppy and the throttle is a bit scary.  From the previous CAD design, I put in a few extra pieces including a piece to brace the wheels and a front bumper to help make the steering more rigid.  I also made the motor mount adjustable so I can tension the drive belt over time.

Most of the body was straightforward.  I cut the 2x4 stock down to size with a radial miter saw.  The hardest part to make was the steering column, which I used a bandsaw to cut down and sanded it with a belt sander until circular and smooth. Using 2.5" wood screws, I assembled the frame with a hand drill (although I wished I had a hammer drill).

Once the frame was together, I had to put together the wheels.  Everything I had came in parts, so I had to press some bearings into the hubs, stuff the wheel with an inner tube, screw the hubs together, and then pump up the tire.  I mounted the wheels on 200mm long M10 screws, which made for a simple axle.

Next I had to figure out the electronics.  First I went to work on the battery pack.  With some help from Charles Guan and some spare A123 26650 cells, I was able to solder up a 8S3P pack which would give 26.4V nominal (the maximum for my ESC) and over 6Ah of charge.  It took me in a few hours to make, partially due to having to hand crimp and assemble the appropriate connectors to balance the cells, but after I shrink-wrapped the whole thing it turned out nicely!

The last part to tackle was the throttle.  Using a force sensor I had leftover from a class, I wrote up an Arduino program to give me throttle control that was dependent on how hard the sensor was pressed.  Its very sensitive, but since I have some other things to work on, I'm leaving it for now.  In the future I plan to fix the throttle issue, make a new drive pulley (the current one isn't centered), and possibly stabilize/redesign the steering.  For now, here's a video!

By the way, I did pretty much all of the work at MITERS, so many thanks to them for their hospitality!

Did I Mention I Like Cars

Last week I attended the New England International Auto Show.  I was pretty cool, and I got 50% off the tickets with Groupon so I went with my girlfriend Alina.  I got to explore/sit in a bunch of new cars and ogle more expensive ones, so all in all it was a good trip.  For example, they had a Fiat 500 Abarth!

Yes, I did fit.  Barely.

There were a bunch of things I liked, including engines, rims, and various shiny things.  They even had some fancier cars such as the Lexus LFA, Mercedes SLS, and my all time favorite the Audi R8 :D

I could barely contain my excitement.

Winter Break

MIT's Independent Activities Period is good and bad.  Its good because there are a lot of opportunities and it gives students a break from regular semester classes.  Its bad because it lasts until February so that I won't graduate until June!  Regardless, I have been making the most of my time recently by keeping busy.  I was lucky enough to spend over a week at home which my family, which included Christmas and New Years.  Despite the festivities I somehow got some work done!

First off, I had to help my dad fix the tire on our minivan.  He teaches a high school auto shop class, so its really cool to see where he works and learn from him.  The front-right tire pressure was dropping to around 15 psi just days after filling it up, so we knew something was wrong.  After a quick inspection it turned out the culprit was a huge nail the van must had run over recently.  As I learned, the way to plug the hole is apparently to coat it in industrial rubber cement and jam a sticky, jerky-like stick in the hole.  My dad told me he's been doing it that way for decades, so it must work pretty well.  Once you let it set for a minutes, you just pump up the tire again, trim the ends off, and voila!

The ends wear off as you drive. Who said car maintenance was pretty?

I also finished up the CAD for my first electric vehicle.  Its not terribly exciting, but the project is suitable for a beginner.  I was inspired by the idea of wanting to make a scooter, but not having the materials or money to make an expensive one.  I present to you.... 2x4 Scooter!

Composed almost entirely of wood 2x4s, it has two 8" wheels, rear wheel drive via a brushless outrunner motor coupled with a timing belt, and I plan on making a lithium-ion battery pack to give it plenty of power.  I'll post the build once its finished!