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December 29, 2014

2014 East Campus Roller Coaster

Since working on the rotating climbing wall last year, I've been interested in trying to revive the East Campus roller coaster.  Fellow MechE 2016's Jaguar K. and Wesley L. were similarly enthusiastic about the roller coaster, so we started coming up with ideas over that fall semester.  We got an early start on the approval process for the ride, and, thanks to lots of hard work from our Rush chairs and others, we were able to get the permitting and approval from MIT and Cambridge in time.

After a week of construction, we had a working roller coaster:

Photo credit to the folks at

More documentation of the roller coaster's design and construction can be found here.

September 30, 2014

iPad Retina Display External Monitor

Two summers ago I bought an iPad 3 LCD off ebay.  These are 9.7" 2048 x 1536 IPS panels, which use an internal DisplayPort interface.  In May, I finally got around to building an external display out of the panel, which can be clipped directly onto the side of my Macbook Pro's screen, and is powered by a USB port.

I have been using the display on a daily basis for the last four months, and it has held up beautifully.  It took a little while for my eyes to get used to the tiny 264 pixels-per-inch pixel density, but I can now comfortably use it at native resolution.

The display's build log can be found here.

December 2, 2013

All Terrain Scooter Redux

The original version of my all-terrain electric scooter suffered from a number of problems, the most important of which was in the motors I used.  The triple CIM motors were just not capable of providing both the top speed and acceleration I wanted out of the vehicle.  Actually they could, but just not for very long before the insulation on their windings turned into a melty black mess.

After some attempted snow-scootering during the northeast snowstorm last year, I decided I was sick of the freshly roasted motor smell, and stored away the scooter until the summer.  A full teardown of the scooter revealed enough unnoticed or impending failures that I decided to scrap pretty much the entire mechanical end of the original scooter.

Version 2 features the same HobbyKing LiPo battery pack and Kelly 72V 200A brushed motor controller as the original, but nearly everything else is new.  Replacing the CIMs are a pair of Magmotor S28-200's, which are slightly larger than the S28-150's of battlebot fame.  Like before, the motors are mechanically coupled to one output shaft through a gearbox reduction, and connected electrically in series.

This version also has even bigger wheels (because the old ones clearly weren't large enough...), and over a foot of clearance everywhere.

The scooter's build log can be found here.

October 5, 2013

Gourd Ukulele

Back in June, I returned to Atlanta for a couple weeks.  While there, I took advantage of all the woodworking hand tools I had access to, and made this ukulele.  The body of the instrument was made from a dried gourd.  The neck is mahogany, which was scavenged from the desk in my old bedroom.  The fretboard is burned oak, which was split off a stump in my back yard, and the soundboard was the bottom of a desk drawer.

The ukulele is about Tenor sized, and tuned with a low-G.  Fret positions were determined using this handy online fret calculator.  All of the construction except drilling a couple of holes was done with hand tools.  The neck was shaped mostly with a drawknife, except for the channel for the tuning pegs, which was chiseled out.

The ukulele's build thread can be found here.

I don't have any audio or video clips of me playing it, so you'll have to take my word for it that it sounds pretty good.  I think it does, at least.  Not that I have much to compare it to.

September 4, 2013

Rotating Climbing Wall

For REX this year at East Campus, I helped to design and build a rotating climbing wall.

The climbing wall consisted of a twelve-foot diameter by eight-foot wide wooden cylinder suspended on an axle.  The surface of the cylinder was covered in climbing holds.  As the climber progresses, their weight causes the cylinder to rotate opposite the climbing direction.  

April 28, 2013

Zero-Dollar Carbon Fiber Bicycle

Back in January, I was presented with a large carbon fiber tube, in the form of an oar.  Being who I am, I made the obvious decision to build a bicycle frame out of it.  As I found out when building my bamboo bike, making a bicycle frame from scratch, especially when using composites,  is not actually very hard, as long as you have a lot of patience.  To make this project more interesting, more challenging, and cheaper, I built the entire frame and bicycle without spending any money on it.  Every component (except the pedals, which used to live on the bamboo bike) I either made myself or scavenged.

March 25, 2013

Electric Tricycle

So I built another electric vehicle.  This time around, I actually did some designing before I got any parts, so this was less of a "what do I do with this cool part" project than most of the things I build are.  However, the actual construction of the vehicle was started due to the acquisition of a cool part:  the "melon" sized brushless motor that drives the tricycle.  Getting the motor was a great excuse to implement a bunch of ideas for an electric vehicle I developed after building my electric scooter.

This was my first big project done with access to real machine tools (courtesy of MITERS), so this was both my learn how to machine things and learn how to Solidworks project.  Even with just a semester working with these tools, I was able to make this vehicle significantly more refined (while simultaneously even more ridiculous) than my scooter.

The design for the vehicle was inspired by the classic Radio Flyer tricycle.  That vehicle geometry is not exactly intended for the high speed go-kart like performance I wanted, so I tried to optimize the design while retaining the tiny kids-trike aesthetic.  

And now, a brief overview of the tricycle's specifications:

Motor: Turnigy C80100-130 brushless RC outrunner
Controller: Kelly KBS48121 120A peak BLDC controller
Batteries: 39.6V 7.5 Ah A123 Systems Lithium Nanophosphate pack
Drivetrain: Manual 8-Speed Shimano internal gear hub, custom spur gear differential
Chassis: Welded steel tubing and aluminum plate construction with side-to-side leaning
Top Speed: 45+ mph, if you're feeling brave

More pictures, videos, and build log can be found after the break.