Electric Vehicles

In recent years, I’ve taken on a keen interest in electric vehicle technology. To that end, I’ve built several small electric vehicles which demonstrate propulsion technologies and nonstandard powertrain architectures, as well as motor control systems and user/operator interfaces. These projects, unless otherwise described, have been products of free time and not funded or supported officially by MIT. Note that some projects below have been taken apart, recycled, or otherwise terminated, so their pages are for historical/reference purposes only.

As usual, individual pages that contain more detail are linked through the image thumbnails, if they exist.

Chibi-Mikuvan is the latest technology and methodology demonstrator made from a hodgepodge of unrelated commercial and industrial parts, in addition to being my first foray into composite bodywork. Combining a salvaged NiMh battery from a hybrid 2010 Ford Fusion, a 9″ angle grinder’s right-angle gearbox, a water-cooled R/C boat inrunner motor, and a 1/5 scale R/C car ESC, Chibi-Mikuvan is designed to superficially resemble a cartoony version of a 1987-1990 Mitsubishi “Van/Wagon” known as the Delica in non-US markets. The bodywork uses the fiberglass-foam composite sandwich construction method, and despite being decorative only, is still highly rigid.

BurnoutChibi is a complete rebuild of Chibikart 1 with two goals: To demonstrate how to properly use a sensorless drive system in a vehicle, and to have two speed ranges. BurnoutChibi’s powertrain uses an extremely fast (400 rpm/V) motor geared very high (16:1 in low gear), and it is able to start, using regular hobby model ESCs, every time. The two speed ranges enable both positive starting torque and high top end speed. As a result, it goes much faster than a Chibikart ever should.

RazEr REV2 is a refresh of RazEr rEVolution which uses frame materials more effectively and has more of a ‘finished look’ to it with wire guides and switch panels. Otherwise, the internal components have stayed much the same.

The Democratic People’s Republic of Chibikart was built in an attempt to make the Chibikart design as accessible as possible. All of the parts are commercially sourceable (Yes, even the waterjetting – that’s the easy part.) and the methods are repeatable. The hub motors and exclusive battery module of Chibikart 1 are switched out in favor of R/C outrunners and chain drive. A step-by-step Instructable was published focusing on the construction of the vehicle.

Johnscooter is the testbed vehicle of Kitmotter 0002. Based on a “FX-1 EZ Rider” compact electric scooter frame, I removed the original powertrain and only slightly modified the frame to accomodate Kitmotter. It otherwises uses the stock battery and retains the stock braking system. Its sole purpose is to test the viability of Kitmotter.

Melonscooter 2 is a continuation of my “daily driver”, Melonscooter, using a much larger and more robust former 50cc scooter frame. It retains the same 80mm “melon” outrunner which gave the projects its name originally, this time paired with automotive lithium iron phosphate modules.

LandBearShark is another embodiment of my undying desire to create that which should not be created. 4 horsepower of DC motors driving snowblower tracks, fed by lithium iron phosphate batteries, all stuck to an old-school skateboard.

eNanoHerpyBike was built entirely of on-hand parts, in one day. It uses a high speed R/C helicopter motor with a very high (8:1) gear ratio to attain (relatively) fine control, immense torque, and high top speed, despite using a R/C aircraft motor controller.

Technologies and Components

The Miniature Electric Hub Motors have been my primary “field of research”, if they can be called that. Since the first version built in late 2007, I’ve been refining the engineering in order to make them more powerful, torquey, and reliable. There have been several variations and designs, most of which have ended up on some kind of scooter.

What fun is a motor without a motor controller? In a quest to conquer my electrical engineering demons, I’ve designed, built, tested, and detonated several motor controllers. They range from simple DC motor control to 3 phase brushless motor control. Most are controlled by an Arduino in one way or another, and some are specialized. However, for reference purposes, I’ve grouped them onto one page.

Chibikart is an ultra-small four-hub motor drive go-kart designed to test out the ability of the 100mm size hub motors to move a person without assistance, such as kick-riding a scooter or skating along. I wasn’t sure that the motors could handle enough continuous power to move a person on flat ground, but my fears were allayed with Chibikart displayed way better than expected efficiency and power use at speed, even climbing up one of MIT’s spiral parking garages. Chibikart is also my first use of 80/20 slotted framing which is very popular for prototyping machines quickly – and now I see why.

Melon-Scooter is my “daily use” vehicle. Using one of the largest BLDC aircraft motors available with lithium nanophosphate batteries and pneumatic tires makes for a longer range, more durable, terrain-capable scooter than any of the RazEr iterations. Melonscooter I was retired, finally, due to frame rust after 3 years of service!

The RazErBlades are another bid to motorize that which should probably remain unmotorized. Born partially out of peer pressure and partially out of curiosity, the skates use RazEr’s motor technology and are filled with lots of firsts for me – namely, custom PCB design, wireless communication, and user interface design.

RazEr, initially known as Snuffles Reloaded, was one of the first projects I embarked on soon after arriving at MIT and discovering the practically boundless resources available. It features a unique direct drive motor embedded in the rear wheel (which itself has been revised many times) and is one of the lightest and smallest scooters capable of the 3-5 mile, 10-12 miles per hour “urban local use” range. This style of compact electric scooter has been termed “electric kick scooter”, and of all of the currently existing projects or products, RazEr is still the smallest.

RazEr rEVolution is the latest in the line of hub motor scooters. RazEr was a great proof of concept, but it’s dimunitive size means battery life and motor torque are both very limited. rEVolution starts over with a fully custom frame and a much larger motor which features double windings and a redundant controller. It’s still an “electric kick scooter” class vehicle, however, and is comparable in size to the Motorboard series of scooters.

Snuffles was my very first EV project, constructed during the summer of 2007. The original scooter, a Sharper Image X2, was a very small “electric kick scooter” whose size I wanted to maintain while adding more power. It featured a mostly stock R/C aircraft equipment lineup, including a very dramatically oversized motor. The vehicle was almost impossible to control, but very fast and indeed very dangerous. Building Snuffles contributed in large part to me becoming an undergraduate member of the Smart Cities group in the Media Lab.

LOLrioKart is my most well-publicized work, and is a project that is constantly in flux. While originally built as a joke, it became a serious engineering endeavour as I began experimenting with electric motor controllers. The “Kartroller” series is essentially its own project bloodline, and is finally stable at version 6, featuring bidirectional drive and regenerative braking. A rear differential and front disc braking are also features not often found on randomly-built go-karts.

Millicycle started life as a pocket bike rolling frame I purchased on a whim. I quickly put together a power system with some lithium nanophosphate batteries and a custom BLDC motor that I originally designed for an experimental Media Lab motor scooter (i.e. Vespa-like). Millicycle is named as an homage to the Killacycle. Now revived as a project by Adrian Tanner!

Segfault served the dual purpose of fun vehicle exercise and class project (well, a certain part of it anyway), so it is doubly linked here as well as the Academic Projects page. It’s my entry into the DIY Segway world, but it possesses one trait which sets it apart from most of the others…

Straight RazEr was designed partially as an homage to the original “Snuffles” scooter and partially to see just how ridiculously fast a push scooter sized vehicle can go. It is designed from the ground up to be a drag racer, with wide soft rubber wheels and a motor almost as large as Melonscooter’s. Now revived as a project by Kramniklabs.


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