Welcome! Beneath this text on the main page are my most recent posts. Class projects are listed in the left column, while more personal projects are in the right column

Friday, January 27, 2012

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!

Saturday, January 21, 2012

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.

Friday, January 13, 2012

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!