The epic journey of the spinning disks of doom.

Well, maybe not epic, but at least humorous. The spinning disks of doom were five "steel" plates I ordered from Big Blue Saw because they were cheaper than material + machining time at MIT even though we have six abrasive waterjets. Go figure. I say "steel" because the first set I got was aluminum. I had actually figured out this mistake before they arrived because the shipping weight was off by exactly the ratio of densities. Anyway, I eventually got the steel plates and installed them for motor testing:

DO NOT TRY THIS AT HOME...OR ANYWHERE.

This was an incredibly bad idea. 55lbs of steel dangling off the edge of a motor shaft with no other bearings and no enclosure is a disaster waiting to happen. It happened to be very well balanced due to the fact that the waterjet cuts the ID and OD at the same time, and it ran very quietly, but NO NO NO DO NOT DO IT. It stores as much energy as 500 lbs moving at 40mph. This makeshift inertial dynamometer provided some invaluable testing data for the kart regen system, and then I decided it must be destroyed. It was the most dangerous thing I've ever built, and I decided this while standing next to a 110F ultracapacitor on an electric go-kart...

So where do flywheels go to die? When I got involved with the MIT Electric Vehicle Team outreach project, they were looking to make a tabletop demonstration of regenerative braking. Sounds familiar. Turns out they had enough time to do it the right way...bearings, hubs, enclosure, etc. It was also much smaller...8" instead of 14" diameter disks. So, I gave them the plates and they produced a mini-flywheel out of the insides:

Much more sane.

So that takes care of the donut holes, but then what do you do with a bunch of 1/4" steel donuts? Pretty useless, right? Not if you believe in conservation of usefulness. After looking around for a microwave transformer or something to smooth out some extremely high battery charging current, also for an EVT project, I remembered these donuts. Toroidal inductor core!

Also surprisingly less dangerous than the previous usage.

Yes, I know this is not a great inductor, as a lot of field is wasted in the excessively-large steel ring. But according to some maths it is >200uH, which is good enough for the job. The job, btw, is insane-charging a motorcycle Li-Ion battery pack. (4-6C charge rates.) This will smooth out the 100A charge to about a 5A or 10A ripple current. Hopefully...

In any case, the spinning disks of doom have found new homes.

EVER / e-Kart Wrap-Up

Well, I'm back in Cambridge now trying to catch up on a week's worth of work. (It helps that I'm still operating on a slightly shifted time sense; I've been getting up at 6AM and going to sleep at 11PM recently. I realize this is fairly normal...but not at MIT.)

Anyway, I had a great trip that will undoubtedly be one of the most memorable experiences of my higher education. I can't help but think that at some point in my life, when electric cars are at least a common sight, if not prevalent, I will think back to this and bore people with my stories of the early days. What's that? I bore people with my stories already? Well then mission accomplished, I guess.

I already went on about EVER in my last post, so the only real update I have for that is an amazing gallery of pictures:
http://web.mit.edu/scolton/www/EVER_pics
Photo credits: Cam T. (mostly), Max H., Paul P., and myself.

After EVER, I moved on alone to e-Kart, a French electric go-kart competition for schools and universities. It reminded me a lot of FIRST, in the team structure, educational emphasis, and competition environmont. The karts there were decidedly faster than ours, on average, but also a bit lighter I think. (Stupid Americans and our over-sized vehicles.) There was also a lithium-ion kart with an AC motor that I think is the most drool-invoking go-kart I've ever seen (third clip, #77):



The others were also very impressive, in both power and degree of instrumentation. Most were heavily student-built, too. Here is my small gallery from Tours, France, where e-Kart was held this year:
http://web.mit.edu/scolton/www/ekart_pics

I don't know yet what exactly the path I take from here is, but I've seen enough now to know that this is an awesome educational opportunity. Maybe there's a role for me in creating something of an open-source reference for this kind of project. We'll see. I'm looking forward to seeing America's first foray into educational alternative fuel (not just electric) kart challenges this in May: Winston-Salem/Forsyth County School is hosting the Go Green Go-Kart Competition, open to all NC schools. Until then, preparation for 2.007 will probably thoroughly occupy my time!

Things I Learned in Monaco

A portion of the Cap Kart team just finished up a trip to Monaco for the EVER '09 conference, and all I can say is "Wow." It really is an amazing place and I can't think of a better venue, especially for automotive enthusiasts. We were awarded "best student paper on ecological vehicles," a wonderful honor which just reaffirms the quality of work that this team can pull off in just a few months. I use this project now as a mental model for how effectively things can get done with the right set of people, skills, ideas, and resources. I know it's unrealistic to expect such good team dynamics in all instances, but it's helped me develop my project organizational skills, at least. Here's a picture of the six team reps, looking sharp for our presentation:

I learned a lot during this conference. It was my first conference of any type, since I have just started my graduate school career, and so I was a bit nervous. But what I found was very comforting: There was certainly some very detailed technical and analytical work presented, but our particular brand of hands-on experimental work was also well-received. And the relative anonymity helped - presenting with a clean slate audience seemed easier to me than talking to MIT faculty/students about it. Besides the scientific conference, there was also an expo and a rally, where I got to see two Tesla Roadsters up close. Here's the blue one:

Speaking of Tesla, I also just saw video of the first public test drive of the Tesla Model S, a "seven" (five) seat sedan with a base price of $50,000 for a 160-mile range. Here's a car being built by a California start-up in a matter of a couple years that is fully-electric and only $10,000 more than the Chevy Volt, a plug-in hybrid with a 40-mile battery range. Oh, and it does 0-60 in 5.5 seconds. An electric sedan. Check out this video. This is the future, tearing up the streets at night with an impromptu police escort and a hand-held camcorder. It reminds me a bit of our kart videos in style...accessible, 21st century, unedited do-it-yourself technology for the YouTube era. No press agents, no corporate public relations highlight reel, just a sick ride shown off by a company without any "bad momentum."

Back to Monaco. The other thing I learned was about Monaco itself. I wasn't surprised that it was a beautiful and extravagant place. Nowhere else in the world could you see a Lamborghini with a Rolls-Royce awning and a palm tree reflected it its perfect clear coat, parked in front of a Porsche dealership...

...or stumble upon one of the most famous and scenic Grand Prix circuits in the world...

...no, none of that really surprised me. What did surprise me was that you can actually go there. No, seriously. You can spend five nights in Monaco, traveling from the US, for less than $1,000. (Not including the money you decide to blow in the casino or renting a Ferrari. But let's pretend for a second that you don't gamble or know how to drive.) This is how to pull it off:

1. Travel in the off-season. March/April is apparently not tourist season, even though in my opinion the weather is perfect. 60/70s and mostly sunny. A bit cold for beach people, but I am not one of those. Perfect walking/sitting outside weather. And the airfares were dirt cheap, a casualty of the economic recession. Just over $600 r/t on Air France with an easy connection in Paris. From Nice, you can take the bus or train to Monaco along the beautiful coast for less than $10.
2. Travel with a group and stay in at the Adagio Palais Josephine in Beausoleil, France. This is a hidden treasure. It is a 10-minute walk from the casino and the port, but you immediately cut your hotel expenses by about 75%. An apartment for four, which could easily sleep six, was 128 euro/night ($170/night). That's $42/night per person! For a huge apartment with a balcony, separate bedrooms, a dining room, and a kitchen. The kitchen is the other key:
3. Cook your own food. While you can find some reasonable deals, such as these delicious 4.50 euro crepes you can eat outside at the harbor...
   
   ...you can really cut your spending by cooking your own. Example: Simpler, but almost as delicious homemade crepes:
   
   There is a market right outside the Palais Josephine. You can eat for about $5/person/day. Another reason to go with a group.

And then, with the money you have saved, you should feel free to spend on way overpriced souveniers, helicopter rides, high-stakes blackjack, Ferrari test drives, or whatever else floats your boat. Or you can relax and enjoy a wonderful deal at a place that is, in my opinion, a much nicer trip than Paris or Vegas. It is neither touristy nor exclusive, and for car lovers it is a dream come true. Go. Now.

I am now in Tours, France, to observe a university-level electric kart competition, a good opportunity for me to take some lessons from experts here about what we could be doing to further education in the alternative energy fields. Hopefully, the new enthusiasm for such ventures will open up similar opportunities in the States. Maybe I can help with that. I will continue to accumulate pictures and in a later post will link to the entire gallery from Monaco and Tours.

Au Revoir!

Photo credits: Cam T., Paul P., Max H.

Happy New Year

It's been a while...

In the latest exciting news, our Cap Kart paper entitled - ready for this? - "A Simple Series Battery/Ultracapacitor Drive System for Light Vehicles and Educational Demonstration," was accepted for presentation at the 2009 Ecological Vehicles and Renewable Energies (EVER '09) conference in Monaco. Ridiculous title aside, it was a fun paper to write; if you'd told me last year that my first real publication as a graduate student (or ever) would come from this project, I probably wouldn't have believed you.

Cynical Shane would like to point out that this project, now accepted as real research by more than just me, was done quickly, simply, and inexpensively. Not that it was easy. In fact, there were more times during this project than ever before that I've felt overwhelmed by technical difficulties. But it stayed on schedule and on budget the whole way, and produced real experimental data from an actual physical piece of hardware. Which is more than I can say for some other projects I've been involved with recently.

Good Shane says: Look at that view! I'm happy and proud for the team that an idea which I knew was a good one has made it this far. I can't wait for the trip, which falls during my spring break, and the chance to see some other really cool projects in the field. It'll give me something to look forward during the Boston winter months.

All that's left to do now is dismantle the spinning disks of doom, which have somehow served their purpose without killing anyone, and get the kart out to the track some time when it stops snowing. (May?) Plenty of stuff to keep me busy in the meantime. Happy 2009.

Camera Purge

One of the benefits of having a video camera with a 30GB hard drive is that you can store 7 hours of video, but that also means that people leave a lot of raw video on it. (I say "people" because it's been a while since I've actually shot video with my own camera.) So to test my video converter and new computer, I took some of the left over clips from the Cap Kart project and clipped them together.

If you were wondering what NASA-like engineering procedures are employed in my summer projects, these should clear things up. Happy Thanksgiving!

On Simplicity

I love simple systems. I think somewhere in the process of building a 300-amp motor controller from scratch, we forgot how remarkably simple the electric go-kart really is. It took a while to get there, but in what I think is a good example of engineering system design, the individually complex pieces (most of which I would have preferred to buy off-the-shelf if they actually existed) together make something so easy to understand that it must work.

When the kart engages its regenerative braking circuit, there are only really two places for energy to be stored: in the moving mass, or in the capacitor. The batteries are out of the equation, since the main controller, in an act of almost absurd simplicity, cuts them off and shorts the motor terminals across the capacitor. Of course there is friction, but let's say we idealize by using a 54lb steel flywheel instead. ("That is one of the scariest things you've ever built." -Matt R.)

The only way to move energy from the mass to the capacitor is by energizing the motor's magnetic field, forcing current to flow as it acts like a generator. The flywheel slows down, the capacitor fills up, and along the way a sizable portion of the energy is dissipated in the resistance of the motor. Since we can measure current the whole time, the energy dissipated can be calculated. And guess what? It almost exactly matches the energy difference between the final value of the capacitor and the initial value of the flywheel, every time. The data is up on the site.


I'm not sure why I was surprised by this. There's a huge spinning disk, a huge capacitor, and a huge copper motor winding. There's no where else for 10kJ to go in a matter of seconds without destroy something, so that must be all there is to it. I'm pretty sure I thought this all through and came to a similar conclusion before we even started building. But after months of fiddling with power electronics nuances, it was wonderful to see the conceptual simplicity come to life and to see the data confirm that physics does indeed work.

Take-away: If I draw a resistor and a capacitor and ask people if that's a simple thing, they say yes. If I draw a go-kart with regenerative braking, they say no. Hopefully I've taught a few people to say they're the same.

Large Spinning Disks of...Aluminum?!

I was wondering how UPS had managed to alter the material properties of steel to make it so light. A minor setback, steel disks are now on their way. I hope somebody out there is designing something really cool that can be cut out of the inside material of left-over 14" aluminum disks.

Large Spinning Disks of Doom (or Steel)

An annoyingly blog-like title to start with. Aside from just testing out how this blog thing works, I will attempt to catch my readers (hah!) up on one of my current fun projects, an electric go-kart with a 110F ultracapacitor boost. (Think railgun-you-can-ride.) Working with a crazy - but very competent - group of high school students from the MIT Edgerton Center Summer Engineering Workshop, we built it over the summer and have had some fun driving it around campus:



By the way, I do this kind of stuff because I sometimes get bored with business-as-usual in my life as an engineering student. But this particular project is interesting because I think, as fun as it is, it also has significant serious research potential. Since we've already proven it is a fun ride, I'm thinking it might be time to satisfy academia with some more controlled experimentation. Hence, the spinning disks of doom:

These 11lb, 14" steel disks will provide rotational inertia directly to the electric motor on the kart, enough to simulate the effect 500lbs of kart + driver. And all without leaving the table in our shop. Not as much fun, but with the wireless data acquisition system it should rake in results fast enough to meet some paper deadlines. And even if the papers get rejected, guess what, now we have a sweet electric go-kart and five massive steel plates.

If you are wondering what magic MIT technology we use to produce custom-cut steel disks, it is called an abrasive waterjet. But in fact you can use one yourself. I sent the order out at 2:45PM and they were cut and shipped by 5:00PM. Can't beat that.