Archive for the 'Electric Vehicle Design' Category

 

The Life of Charles: Untold Tales of February Through Now-ish; BattleBots, Markforg3d, 2.00Battleship, and Chibi-Mikuvan Upgrades

Jun 16, 2015 in Chibi-mikuvan, Electric Vehicle Design, Events, Stuff

Isn’t it sad that the last meaningful post on this site was in February? I think it’s a travesty. A combination of perfect storm factors has overwhelmed even my blogging habits. I’m kind of like the Waffle House test of blogging – if even I stopped blogging, you know some shit went down. And I do have some very interesting news to report. In no particular order of criticality or intensity, I present…

  1. The extent of what I can say about Battlebots on ABC before the season premier!
  2. I got a new shiny thing, a MarkForg3D Mark One continuous-filament 3d printer!
  3. Porting (heh) 2.00gokart to the water: The making of 2.00Battleship for this summer’s SUTD program.
  4. When it’s not robot season, it’s go-kart season. Time to make some changes to Chibi-Mikuvan!

(more…)

Silly Go-Kart Design: The 2014 Summer Season

Aug 16, 2014 in Electric Vehicle Design

Hello and welcome to another episode of Silly Go-Kart Design! I’m your host, Charles.

I knew that immediately after coming back from the Detroit race, I’d totally drop off the radar for two weeks as the MIT-SUTD Global Leadership Program drew to a close and everyone rushed to finish their creations. What does global leadership have to do with silly go-karts? Hell if I know, but they asked me to run it last year and it sure as hell worked out! I don’t try to read too deeply into things with “leadership” in their titles.

This year, the program was expanded to 36 students. Oh, dear.

Thirty were shipped from Singapore, while there were six MIT students who were accepted into the program after a local call for sign-ups.

Luckily, the crew for this summer was made up of some pros. First, long time compatriot in robot arms Jamison, then there was Banks (who was also an undergrad TA for the spring 2.00gokart session), and joining new this summer was Paige, who was actually a student in this year’s 2.00gokart and decided to help TA this summer session. Without highly experienced TAs, this summer would have been actually impossible.

Before I dive into the action, here are the deltas from the spring 2.00gokart. There’s some important changes that we made to scale the class to the biggest it’s ever been, now with multiple instructors. Much of the documentation was moved to The Cloud™ through Dropbox or Google Docs.

The Secret Ingredient

This past spring, I decided to spice up the design space by giving all teams the opportunity to use a troll free part: a pair of pink Harbor Freight wheels, which has since been decided was the best idea ever. As I mentioned in the spring 2.00gokart recap, I wanted to use Vex Omniwheels as the troll free part, because why the hell not. I’d checked out Vex omniwheels in person before and they seemed to be well-constructed enough to handle vehicle loads.

I’m proud to say that the troll design sweetener totally worked. Multiple teams went for the omniwheel solution, and none of it ended in little rollers being scattered across the parking lot.

Parts Buffering

In the three or so weeks preceding the program, I ordered a load of parts that, from past experience, students tended to gravitate towards the most.


My body is ready.

In past classes, everyone’s mostly gone for the classic Kelly Controller and Turnigy SK3-63xx combination, a wheel or two from Monster Scooter Parts, chain drives, pedal throttles and thumb throttles alike, the weird little black brake calipers, a Hella switch, and so on. Then there’s always the odd DC motor team, so I got stuff to cater to them too, with the most common DC motor used previously (the 24V “500W” size scooter motor). This cabinet was pretty empty by the end of the class.

I try not to ‘kit the class’, but with time so crunched during the summer session, this was one way of making sure people could finish time. Teams that ordered a part I just happen to have received their parts generally after a day or two’s delay so they could get working quickly, but not right away to preserve an element of fairness. My benchmark for fast shipping is McMaster and Amazon Prime, so most teams got most of their shipped parts in the same timeframe anyway. Surplus Center folks, however, were out of luck.

It’s important to note that the contents were not made known to the teams beforehand. By the end, everyone pretty much figured out what kind of throttles and stuff I had anyway, but the work towards the beginning was reasonably independent.

Bill of Materials

One of the cornerstone elements of my ‘class’ is that all teams order their own parts (beyond the small material pile I provide them). In all past terms and semesters, this was accomplished by one team member sending me, via e-mail, a list of stuff to order. This worked well enough, especially since I am the only person with a procurement credit card.

What this system didn’t have is a way for any other instructor to verify/advise on perhaps badly informed or thought out purchases. Nor could students see ahead of time what their teammates ordered – near the end, everyone starts sharing parts and excess materials. We wanted there to be a bit more networking available to them, as well as to have the ability for each instructor to oversee the activities of a handful of teams.

For this BOM, we set up a Google Doc spreadsheet that was editable by invited students. Each team designated one member to be the go-to for finances. Through this spreadsheet, they were able to not only specify parts to be ordered, but also have a real time check of their remaining budget.

Students had made their own BOM Excel spreadsheets in past classes, but this made everything uniform and accessible.

The ordering protocol was that every purchasing day (Monday and Thursday of the 3rd through 7th weeks) I’d sweep through the BOM and then highlight green any items that were ordered. I’d highlight in red any items that were NOT ordered – the reason usually being that the specification was incomplete or the item was out of stock. Students were warned repeatedly ahead of time in both Milestone documents and the “Resources and Parts” lecture that this was going to be enforced strictly. We had very little issue with this overall.

This is an example of a fully filled out team BOM from the end of the class:

As can be seen from the image, I indicated when the order was fulfilled – for “class stock” parts, I changed the line to green when I made the “delivery”.

This BOM system worked out great, and I highly recommend it for anyone else trying this. Around the middle of the summer, one team made a “Stuff to share” tab with a similar format and quite a few teams listed their excess screws and materials.

Waterjetting and 3D Print Queueing

In semesters past, I was also the concentration point for all teams’ waterjetting files. Since 2.00gokart and last year’s GLP program only hosted 10 teams, it was still reasonable to keep track of. With competent instructors and more teams this time, we chose Dropbox as the venue for team parts submissions. I set up an instructor’s Dropbox account using our instructor email list as the account holder. The students were asked to either form a new Dropbox account or purpose an existing one (such as a personal account) for the class, and we sent invites to the e-mail addresses they gave us.

This way, any one of us could see in real-time what they uploaded. This caught a handful of potential “waterjet derps” before they were accidentally manufactured. I also recommend using this method, or an equivalent service, to sync fabrication files with instructors.

Within each team folder, students were asked to create folders with the date of submission (e.g. “Waterjet 23 July”) so we could keep track of what was submitted when. I put example folders in each group, such as “Waterjet 1 January” – this backfired at least once when one team absentmindedly put all of their waterjet files into that folder instead of one with the submission date on it, so we didn’t find it for days! Confusing examples are to be avoided in the future, but I gotta wonder some times, you guys….

So these back-end improvements are basically what differentiates this summer session from past sessions. I’m pleased with how they turned out – overall, there was minimal instructor confusion.

the build season

Now it’s time for the war stories! By all measures, this was the smoothest show we’ve pulled off yet – there were only a handful of issues that I’ll address soon. We begin with the first day:

One perk of having multiple instructors is someone can always be taking pictures. So here’s a photo of me giving the introductory lecture. In this one, details were given about the class, schedules, TA/Instructor/shop hours, design rules, and so on. Videos were shown of past semesters. That was more or less the calmest this whole summer was going to get.

Right afterwards, all hell breaks loose:

The demo parts were busted out and people began getting a sense of dread for exactly what they’ve gotten themselves into.

…and test drives were handed out. Not of Chibi-Mikuvan, mind you – that’s how people die. I put it out for display as a slight contrast against most of the aluminum extrusion framed, outrunner-powered karts present as examples (including the Chibi Twins).

It’s interesting to note that the majority of Singaporeans do not drive or own a car. The Singaporean government has purposefully made it very expensive and time-consuming to own a private vehicle on the island, due to traffic congestion and land concerns, so instead they spent massive money on a very well developed transit network. Seriously, I can get clean across the whole country in an hour on the trains, and buses will take me to the nooks and crannies. That’s how Shane and I explored so many resources when we were in Singapore. What buses don’t do, taxis will. So really, most of these students have never touched a motor vehicle in their lives.

And boy, did it show. The test drives comprised a whole lot of “100% throttle, 100% brake, 100% throttle AND brake at the same time”.

I once calculated that it would have cost about $85,000 to put mikuvan on the road in Singapore, not that they’d even let it in the country in the first place for being such a disaster. In the U.S., it cost me about $950: $800 to buy the thing, $50 for a PA temporary plate, $75 for a MA registration, and $30 for a MA state inspection sticker – ignoring the transit costs of renting a truck and trailer, of course. In singapore, the “Certificate of Entitlement” saying you may even own a car in the first place would have been around $80,000 (converted to US).

These kids will never understand the joy that is being under your vehicle, covered in burnt motor oil grunge, while contorting to European gymnastics levels to reach an impossibly tightened nut which you quickly discover you used the wrong socket driver size for. Maybe this is for the better.

In the first and second weeks, students generate ideas for their designs and perform analysis of  their desired drivetrain/performance parameters to select the core components – generally system voltage, which motor, which controller, and what size wheels.

One major aspect that differed from last year was that most of these students (something like 66%) were not engineers, electrical or mechanical: they were Architecture or Design students. Many of them had never touched hardware or tools in their lives. I was not informed of this beforehand, else I would have tailored the curriculum with more introductory material. It became painfully apparently during Week 2 when the heavy drivetrain and motor math was introduced – the amount of blank stares and glazed-over looks I received was disconcerting. As a result, we had to hold more hands during “office hour” tutorial sessions. Eventually, most everyone got their heads together and understood why I was making them perform these analyses. Other “crash course” subjects that were a direct result of the students being majority not MechE (unlike last year!) were Solidworks and machine design/mechanical parts knowledge areas.

Pursuant to the lack of experience in this field, many of the karts were somewhat derivative technology-wise. Seen above are students measuring and appraising Paige’s 2.00Gokart project. Many measurements of Chibikart were also made. In the end, though, I’d say the majority of vehicles were not copy-and-paste: the students took the modular concepts of what worked from our examples and reused the modules in their own designs. For example, the Chibikart style of motor mount/corner structure was popular, but in a kart which otherwise had nothing to do with Chibikart. This is totally fine by my books.

Hey! That looks familiar!

Now we’re moving onto week 3-4. Prototyping and getting your full-size mockup together was key, here. I bought something like 300 pounds of 1/4′ and 1/8″ MDF from a local wood supplier , just like during spring 2.00gokart, to let the students prototype to their heart’s content.

Again, the difference between the ‘prototyping’ they’ve been taught and my style became apparent. During this period, some students were frustrated that they were lacking material to make the traditional “prototype” seem in college design and build courses: foamcore, cardboard, wooden dowels, and the like. A few were not sure where to start because of this.

We explained as best as possible that the idea was to go directly from detailed CAD to full-size mockup. And again, this would have been totally fine for a crew of Mechanical Engineers, but time was lacking to accommodate the desires of the Architects and Product Designers. After some frowny faces, people dealt, and the mockup frames sprouted quickly.

The MDF ran down low towards the end of the class (week 6 and on) because many teams used very generous amounts to create bodywork, custom seats, and the like; necessitating me reordering the MDF shipment. My apologies to everyone in the Cambridge-Somerville-Medford area who might have been trying to obtain 1/8″ and 1/4″ MDF materials in the past few weeks.

Hardcore fabrication begins around week 5 as peoples’ parts come in and they realize that “steel rods” don’t make “steel axles” necessarily, among other intriguing facets of mechanical engineering. Also, you don’t tap threads with Loctite as a cutting lubricant.

Above, Tinymill is seen with its groupies. We ran machine training sessions as-needed for team fabricators.

Here, a student is seen nesting in a pile of go-kart parts.

We began taking waterjet cutting submissions during week 4 (basically early July), and one Milestone requirement was to submit several different waterjet parts. Unfortunately, not having a grade or something of coercive force behind it, few teams adhered to the requirement. Submissions really began hardcore around Week 6, which resulted in plenty of waterjet spawncamping by all the instructors.

One aggravating factor was that we originally intended to split the duty between two machine shops which had waterjet machines, but one of them ended up having machine and water supply problems in the middle of the summer, causing us to have to ditch entirely to one shop. That shop was one where only I and Jamison had authority to run the machines, so we ended up having to babysit the waterjet for 2x longer than intended.

It’s important to have a reliable service supplier, and possibly even a backup supplier, if you run a class similar to this. We could not have foreseen the first shop’s issues (and frankly, neither did they), so if I did not negotiate the second shop’s permissions earlier, we’d been b0ned (that’s a technical term).

During the last weeks, the design students’ creativity really began showing through.

I actually like having this summer crew of mixed backgrounds and majors. Why? Because nobody really build a normal go-kart. Even though there were challenges, it’s refreshing to see some experimental, kind of out-there designs, instead of 4 wheels and a steering column. There were rear-steers, there were hand controls, there was an attempt at torque vectoring, and so on. The lineup looked like something out of Wacky Racers.

Nobody’s under grading pressure to “do it right”, so they do it how they want – once again, aligned with my goals for the class.

Just take a look at “Trollkart” here. This was one of the normal ones. They found out that they didn’t really have a good ergonomic location for the throttle pedal. Solution? Make it a hand throttle pedal.

Also, they used the 1 Harbor Freight pink wheel that I gave them for free as a seat cushion. As it turns out, the hub really does not project upward enough to… uhhh, cause damage. They assured me of this fact, which I later confirmed.

…and yes, we had an “Omnikart” team! It took them a ton of effort to squeeze four motors and controllers under the statutory $500 budget, but they did it . Sadly, they spent too much time getting the mechanics running and dropped from the running for the race – instead, spending the whole period during the race trying to get it to drive. Maybe this was a little too ambitious, but the team was super into it the whole time. It was simply too much work for relative novices in an 8-week build period.

I hope to see Omnikart slowly hovering around SUTD in the future.

As week 7 draws to a close, chaos breaks loose in the IDC. Lines for the cold saw are backed up out the door, and people are starting to work on vehicles wherever they can find space!

the contest

We set up the track the same way as last year and this past spring’s 2.00gokart. This procedure is now well established enough with the safety office and parking office that I think I can throw a full event with 2 weeks’ notice, which is pretty awesome. The students were all eager to finally test their vehicles – remember that for many, this was the first complete functional project they’ve worked on.

It was a hard decision for us, but at the end of the build weeks, we decided to scrap the Time/Energy contest we’ve run in years past. The reasoning was that so many teams were just out to drive around novel designs that it made little sense to try and meter their energy usage. So really it became a race of time-only, and a few teams were clearly out to just drive their creations regardless of lap time! I believe that learning is most effective when you’re not under duress, so in the spirit of the program I went along with the instructors’ opinion to scrap metering the energy usage of the teams. It removed a significant bottleneck in queueing karts up for the individual runs.

As I was busy running the event itself, these (awesome) photos are mostly courtesy of Banks and his übercamera.

A great motion anti-blur of one of the omniwheel teams. They were clearly just having fun spinning around everywhere with omniwheels in the back. I took this thing for a spin after the formal event was done, and it’s borderline impossible to control after you get up to speed!

This is what happens when you don’t listen to me about fastening your wheels on properly, guys. One of the teams had an unfortunate, chronic disease of shedding wheels.

Field repairs! I strictly enforced a no-bringing-your-own-tools rule this time, so teams had to make do with a “pit kit” we assembled of the most common hand and power tools. During 2.00gokart in the spring, there were some problems with teams sneaking tools out of the IDC because they needed a special size of long-reach ball-ended hex key to reach their wheel mounting screws or whatever. Well, this time, I had a whole lecture devoted to design-for-maintenance, so y’all have no excuses!

One of the ‘off the wall” karts: a rear-steer, tiller-controlled trike. This is basically a normal go-kart turned completely around. Their complex rear steering linkage ended up biting them, but otherwise it was highly entertaining to watch snake around the course’s cones.

One of the “normal” karts, from a team of self-proclaimed newbies. For being said newbies, they did quite well; ultimately, they shredded their two rear tires!

An issue crops up with Team Newbie Kart.

We called this one “Overconstrained-kart” because they had a single middle rear wheel with drive wheels on the sides. They insisted that the center wheel was needed to support the driver’s weight. Pretty much everyone insisted back that they’d get much better performance if they removed it, which did happen during the middle of the event.

It did perform better.

One way to be fiercely stylish is to match your custom go-kart’s seat.

Don’t worry, Omnikart did get up and running during the event, but they burnt out two of their motor controllers. If I had known that the “40A” robot controller they picked for their design were about as well-built and rated as most robot controllers on the market, I would have offered them a free pair of RageBridges.

After the individual team runs were done, we moved onto “Anarchy Hour” where everyone who wanted to run head-to-head could do so.

At this point, MITERS invaded with Chibi Atomic Jeep! Sadly, I couldn’t get Chibi-Mikuvan back up and running in time due to the necessity of running the whole show.

The Electric Vehicle Team also showed up with its motley crew of rideables. And… wait, is that LOLrioKart?! Why, yes it is – under the command of a new captain. LOLrioKart sat abandoned in MITERS for almost 3 years before it was revived this year. This is the first time it’s been on a track of any kind.

Yeah, it’s as precarious and top-heavy as I rememebered it. Even more so, with it lacking 150 pounds of nickel batteries at the very bottom!

The photo of entirety for this year. Check us out in the background acting all goofy!

the future of 2.00gokart

There were plenty of improvements on the class structure that will make future sessions that much more streamlined, including the use of Dropbox and Google Docs to coordinate instructor effort. I think the class procedures and content is very much at a plateau of stability such that the class can be redistributed easily to anyone who thinks they can run a version of it. Already, I’m seeing derivative and inspired seminars/classes pop up – from a group at UC Berkeley to the Artisan’s Asylum to individual makerspaces.

Unfortunately, I think I’m no longer in a position where I can run 2.00gokart (or the summer session) again. I’m first and foremost responsible for the daily operation of the IDC fabrication shop. It used to be that the IDC was very small and easily managed alongside teaching, but nowadays it’s grown to house dozens of researchers and students. I can no longer justify the time put off running the shop spent towards teaching the class. Each time the class runs, the shop falls into disrepair because I literally only have time to fix what’s broken just enough to keep the students working.

This summer saw my spare time stretched to nearly its limit, and at times, it was frustrating to try and keep up with researcher’s needs while answering go-kart questions. It sucks, since I want to see this happen consistently and would vountarily do so if relieved of the need to run the shop it’s housed in. I’ve let the higher-ups at SUTD know about this issue, and I’m making plans for the continuity of 2.00gokart for next spring and years to come, but for now, I see myself fully entering the role of facilitator and stepping aside on my teaching duties.

(read: IT’S YOUR DAMN PROBLEM NOW! MUAHAHAHAHAHA…)

As for the class itself, I’m once again making the materials I generated freely available online. There are two forms:

  • First, a ZIP file containing only my lecture notes, “milestone” weekly report documents, and other files which I have sole copyright over: MIT-SUTD EV Design 2014 Reference Files. Not only does this have the 8-week program for the GLP, but it also contains this past spring’s 2.00gokart class Milestones, which is a 12-week program with more discrete weekly goals. This past spring, 2.007 itself implemented a “physical homework” system, which is also included in the Milestones but are not tied to or required to use the course materials.
  • Second, I’ve made the MIT Stellar Course Management System page for this summer session publicly accessible (Global Leadership Program 2014). I’ll investigate maybe having this ported to OpenCourseWare for more permanence, but for now, Stellar is stable enough.

That pretty much wraps it up for this year. The smoothest and most enjoyable season of “silly go-kart design” might very well be its last, but we’ll have to see what the future holds there. The students have once again packed up their vehicles and parts for the trip home, so at the very least, we have sprinkled Singapore with even more seeds of mischeviousness!

As for myself, it’s going to be a week of cleaning up the tornado disaster that is the shop, as well as shifting my focus onto ROBOT SEASON! BECAUSE DRAGON*CON IS SOMEHOW 2 WEEKS AWAY! Stay tuned for updates on that front.

2.00gokart: The 2014 Season!

May 11, 2014 in Electric Vehicle Design

It’s over!

Another spectacular season of 2.00gokart has been produced! This time, instead of holding the garage challenge like I have done in the past, I decided to reuse the “road course” that our group put together for the summer SUTD visiting students. Why?

As awesome and science-filled the garaging is, it’s kind of boring. It’s a great theory-to-reality comparison: the mostly-straight course (Let’s face it, 100 foot turn circles for a go-kart is basically just bad toe trim), is all uphill at the same grade the whole way, and of consistent traction characteristics. It’s easily analyzable by relatively simple first order estimates of gravity, rolling resistance, air drag, and drivetrain loss.

But its downsides are also many: there’s no line of sight from one garage level to the next, so we had to use a network of 2-way radios. The narrow concrete-lined end turns required padding or shielding to satisfy the safety office and make sure students don’t actually wham themselves (these two goals are mostly divergent). And of course, to collect the best data, only one team goes at a time, so there’s no head-to-head element, and a lot of waiting.

I  put together the road course idea because the summer students weren’t really in it for grade or explicitly to learn some engineering curriculum. Since that artificial carrot was gone, I figured that the final competition should be a lot more fun-oriented, and what’s more fun that running your peers over with a go-kart you build yourself?

This isn’t to say that science isn’t possible to do, since the Energy * Time metric works for any type of motion with two endpoints. It’s just that for a road type course it’s harder to predict without going into more advanced modeling of friction/scrubbing during turns, the impact of speed variations, and the like. For the summer, we did collect energy * time numbers, and it did provide practical insight into subjects like why two karts of basically the same powertrain layout could have drastically different scores.

With that said, here’s the media trail from just before the infamous “Milestone 7″ rolling-frame inspection, through the semester to the competition itself, ending with the compilation video for this year.

As the inspection approaches, it’s customary for students to find any open nook or corner to work on their vehicles. Usually it’s exactly where the vehicle died or some part fell off.

A common setup in the few days leading up: Food, drinks, headphones, Solidworks, and intent staring.

The inspection itself constituted a visual overview to check that your frame is rigid, your bolts are tight, and so on.

And, of course, the brake test. Your teammate pushes you to a brisk jogging speed, then you mash the brakes. My measure for passing is if the braking wheel could lock up – that indicates, at the least, that the vehicle’s available braking force exceeds its available traction. Karts with short wheelbases and rear brakes would of course excel at this test, albeit at the cost of actually being able to stop well in real life.

After Milestone 7, the teams have three weeks until their kart has to be done done (not just done, but like, done-done!). Good luck with that, Google Translate.

The last 3-4 weeks of the class are generally reserved for electrical work. I issue batteries once students put together their electrical systems and I or one of the TAs look over it real quick to make sure they aren’t immediately plugging it all in backwards. Later on is okay, of course.

In the final week, the shop enters tornado disaster mode.

Electrical system testing and debugging was some times performed live.

By which I mean, actually with live systems. I tried to discourage this practice, of course, but with no moral authority to stand on….

One thing I wanted to experiment with this year was getting onboard video from the karts. This was something I hadn’t had time to think about before, since the class before this point hasn’t been streamlined enough to “run itself” (so to speak). I investigated a few options, from GoPros to Sony Actioncams and the like, even the odd wireless webcam. I was looking for a combination of small  and unobtrusive, inexpensive (so that basically took out GoPros), and streaming video if possible. After some consideration, I remembered that there was a burgeoning market for no-frills small cameras that stuck to something and recorded: Cheap Chinese dashcams.

I only know them because I watch too many Russian dashcam videos. I honestly believe it should be a compulsory element of drivers’ education here, but Americans are probably too squeamish for that. Anyways, these Chinese dashcams offer a wide array of features – some have GPS, automatic G-sensor based file saving to capture the fucker hitting you while parked, voice and motion activation, etc.

All of those features aside, what you get is a relatively inexpensive ($100 or less covers it) camera that can record HD video and is easily portable, and that you won’t miss if it gets run over. I decided to forego streaming video for the ability to have many of them: By this time, I’d already worn down the class budget to a little stub.

Reading a little on dashcamtalk, I decided to go for the latest on the market: The GT680W. It’s resold under a couple of brand names in the U.S., but all of them talk to you in Engrish when you boot them up, as far as I can tell.

My only gripe with the GT680W ended up being its very short battery life. It has a very (very) small internal battery that’s only good for maybe 10-15 minutes of recording outside of a power supply. I’m guessing this was an acceptable compromise for a dashcam because most of the time it would be powered off the car’s 12V rail, and the job of the battery is just to close the video file when the power is turned off.

I provided a ball mount template to the students so they could devise their own creative mounting brackets for the camera’s stock ball and socket mount, which is seen above. Since they’re designed to hang from windshields, the ball mount it comes with doesn’t point back far enough to be used on a level surface.

Lots of dashcam footage was collected during the race, and some of it cam be seen in the highlights video!

As final inspection day approached, students began scrambling to finish important aspects of their vehicles such as the gaudy lighting and themed decorations.

During the week of final inspections, I set up a makeshift track around the conveniently looped shaped third floor of the building, mostly by setting traffic cones out and warning people working in the research labs that they need to yield before merging into the hallway. This was more or less when people started discovering that they should have listened to me when I warned them against chain drives…

The next thing everyone knew…

 

…it was race day! The track was set up the night before by myself and a few cohorts, so all we had to do in the morning was run power to the parking lot and set up the start and finish. All  of the pictures from here on are courtesy of shewu and Dane.

Being next to a power plant and all, you’d expect there would be easily-accessible outlets everywhere. No such thing – our only source of power for tools and charging came from a 150 foot extension cord run from like halfway inside the plant. I in fact had to walk around with a plant staffer for a minute before we even found one. Last summer, I used one that was much closer to the door, but this time when we tried, the circuit was clearly turned off, and the staffer was not an electrician, so he didn’t know where the circuit breaker for that one was.

A morning shot before we began at 9am and before this area became a total disaster too.

Driver’s meeting! I go over the track layout, the competition format, and various logistical issues such as the nearest class 1 trauma center.

At 9AM, runs begin with individual driver time trials – quite similar to Autocross. We rigged the karts with Wattmeters as per the usual procedure, so people could record their energy usage. Each driver got two practice laps and three scored laps.

Some live debugging going on. This team has a build blog! It needs updating! Hint, hint.

By midmorning, the pit area has become a tangle of power supplies, chargers, and soldering iron cords.

During the lunch break downtime & recharging time, I took a stab at my own course with Chibi-Mikuvan!

Having about 3 times the available motor power of my students, I of course, took the best lap time at 20.7 seconds. The quickest student team was 25.6 seconds. This is clearly indicative of my years of experience and accumulated skills.

Yep. Totally.

Chibi-Mikuvan catching a dab of oppo. I’ve now realized that it’s entirely possible on dry ground if I keep my weight forward a little (i.e. hang off the handlebars a little).

After the individual runs were finished, we entered Anarchy Hour, with multiple head-to-head races. Whoever had a grudge to settle from the term did it here!

Coming into the center hairpin turn just a little too hot…

Those fluff bricks were set up for a reason, and they performed admirably.

By this time in the early afternoon, vehicles from across campus had started showing up for Anarchy Hour. Seen here is bentrike, tinykart (not that tinykart, though maybe next time), and a few Electric Vehicle Team members.

Ben, of course, hands everyone their collective asses.

Watch out for this guy – not only did he revive LOLrioKart, whose wreckage  has been hanging in MITERS since 2011, but is up to plenty of his own no-good.

After everyone’s batteries finally ran down, it was time to pile the race apparatus back into the truck!

From here, the students have a final presentation this coming week to recap their builds and talk about their competition performance, then it’s time to clean up from the semester.

My thoughts for this time around:

  • I believe the class in its current form has reached a stability plateau. With more created lecture material, this semester I wasn’t running around answering basic reference questions so much as helping people with designs, which is good. The procedures for the semester are now well established and I feel like I can throw another race next week if I needed to. I think the class is very close to a fully exportable form, though that isn’t the primary goal.
  • More documented lecture material would still help. A few things I can think of immediately: Design for Maintenance needs to be its own thing. It should be a lecture of best practices and tips for making your creation easy to repair. Most people, myself included, have made things which require almost complete disassembly to change a simple part. Or, there’s 5 different screw heads and required driving tools to, say, move your motor mount a little. Another example would be more resource/parts appraising tips to go along with the lecture that is an overview listing. How do you know when two parts are the same across different vendors?
  • I think a different “secret ingredient” each term would keep it interesting. I also phrased it in the grand overview as a “ground point” for the design, but basically  it’s the free thing I give to students that they can accept if they’d like, so the less experienced can start somewhere. This term, it was the 8″ Harbor Freight Pink Tires for America which many teams took because it freed the budget up for something else. I’m heavily considering something ridiculous like omniwheels for the summer season. Anyone have experience with Vex omniwheels in a high speed traction application?!

And finally, as promised, the highlights video. Doses of insulin for your impending diabetes are to the right.

So ends another season of 2.00gokart! I have some shop organization to do in the coming weeks before the Singaporeans get here, and I also hope to finish the last little details of Chibi-Mikuvan.

After the races were over, I decided to try using a GT680W in its intended application. Well, to be fair, I don’t think they meant for it to be used in this particular mounting configuration…

I approve of the night video capabilities of this thing, which I think is almost equivalent to my 2010-era handheld camcorder, except without optical image stabilization. Being so flat, it buffers in the wind too, contributing to quality loss. I think for a $90 camera there is not much more to be asked.

All-around Updates: The Anime Boston Recap, 2.00Gokart Round 3, & Chibi-Mikuvan

Mar 28, 2014 in Chibi-mikuvan, Electric Vehicle Design, MIT, Bostoncaster, Cambridgeshire

I have resurfaced.

Like last year and the year before, major gaps occur in my webospheric presence because I’m busy with corralling a group of undergraduate students before one of them sails right off the 3rd floor of the building on a silly go-kart – 2.00gokart is running again this spring, with only minor changes to last year’s edition. In the mean time, Chibi-Mikuvan has been progressing slowly.

Because this post is going to have some obvious… length issue, here are jumps to the directly relevant sections:

  1. The Anime Boston recap (a.k.a “My Fangirls Rejoice”)
  2. 2.00Gokart’s current state
  3. The work on Chibi-Mikuvan since a few weeks ago

amine boson

One of the quirks of running a shop is you actually never have time to use your own shop; go figure, because you’re either fixing something or helping someone else with tools or their own projects. And many projects there were in the past few weeks: the IDC has been the ad-hoc command headquarters of the MIT Anime Boston brigade, probably because I know everyone and am there all the time anyhow. I even joined in this time! Historically I’ve been an incredibly lazy cosplayer and have just done whatever involved a lab coat or sunglasses.


Except that one time at Dragon*Con, with the 6-foot steel venier caliper, but I digress…

I think the only other time I went above and beyond for a character was the RazErBlades, which were more independent project than not, and I threw together an easy version of the character for Otakon 2010.  My interest in this domain is primarily that of impractically large transforming mechanical weapons, but I have  never taken it seriously enough to work on one as a project in its own right.

But that doesn’t mean I won’t facilititate or encourage people doing so. Check out Jamison’s Impractically Large Transforming Hammer-Cannon (from League of Legends) That He Finally Blogged About, for example.

And the one I am partial to, Cynthia’s Impractically Large Transforming RWBY Scythe.

I’m a fairly close follower of the RWBY series because of its proportion of fancy transforming mechanical weapons, all of which I say “Monty Oum, you son of a bitch.” to because I’m almost certain there are some volume discrepancies going on, such that if you actually built the weapons and had them function visually in real life, there would be no place to put the actual weapon part. But Monty designs are hardly the worst perpetrators of this in all of impractical transforming weapon history. In fact, I think a lot of thought was put into their actuation and mechanical design for the most part, especially for Ruby up there. Things at least don’t magically appear and disappear.

Anyways, I strongly recommend reading through Cynthia’s design and build process because it covers all the bases of design to iteration to implementation, all in a first large mechanical build. My own first mechanical projects were way more, umm, ad hoc organized. I saw a ton of the prep work that went into it, and my involvement was limited to some backend hardware support only (e.g. “make 23 of these e-clip things” “ok”) during the final days of the build. So yeah, here’s the link again to Cynthia’s Impractically Large Transforming RWBY Scythe (which I am told will become slightly more practical but no less large soon)

I elected to make myself some accessories and attend the convention as the fan-made “Rule 63″ of this character:


Image links to creator’s DA page

Okay, you can’t give a character that weapon, call him Garnet (I must use literally a ton of this stuff a year), and expect me not to bite.

Luckily, it still ranked on the favorable end of “easy” to “You have to be cosplaying for as long as I’ve been building robots to do it right”. I even made up a “make versus buy” chart for it:

 

One of the end goals of all the “Makes” was to use some of the rapid prototyping tools I had in the IDC which could be reasonably accessible to anyone – the Replicator 3D printer (which has sort of become our “student beater” machine), and a laser cutter. Harking back to my Maker Resources 2013 presentation at Dragon*Con, this year our group of maker-oriented con-goers (not to be confused with conga’ers) decided to host a panel with much the same topics, geared specifically towards costuming:

 

Unfortunately, I don’t actually have many pictures of my build, largely because it took place during the last two days before the convention where I was mostly aiding the completion of other props and handling 2.00gokart. But stuff did pan out. For instance, here’s a rose sigil thing that I made from the scrap outline of Cynthia’s rose cutouts. The bracket on the back was designed to snap-fit into the buckle of a large tool belt I bought and chopped up for this purpose.

The material is “silver” PLA, which I bought from Amazon (and which Zenn Toolworks hasn’t stopped calling me about to review… yeah guys, it’s filament! It’s all melty and stuff! Yay!)

It’s not silver in the traditional sense, but more like a gray PLA with some metallic sheen in it, which I suppose gets the job done.

A ton of other parts were also made in this same PLA – the large ammo boxes, for instance, which I drew up to hold two side by side .50 BMG rounds up to 6 high, because I don’t know if that was the idea or not, but had the dimensions of the .50 BMG in front of me. Plus, the scythe is allegedly also a .50 caliber sniper rifle. The ammo boxes had removable lids and actually served very practical purposes during the con. Besides those, the decorative crosses were also made in the same material.

I also used it to print the decorative bullets for the belts. Unfortunately, due to time, I didn’t make anything else to hold them to the belts, so we went without them – that will come later. I had a few feet of black cargo webbing and decorative rivets ready for the task.


Termed by my compatriots as “nerd-cute” or “nerdorable”

I think I shot pretty close in the end, eh? This was on Sunday, after Cynthia had broken her scythe demoing it so many times, so she designed and made a comically small stand-in from leftover MDF.

I ended up not being able to attend the panel, unfortunately, since Friday night / Saturday morning I was plowed over pretty hard by a (what I assume was) exhaustion-driven opportunistic flu/cold. It was bad – as in, I could barely stand up and walk straight bad. I ended up sleeping most of Saturday off in the IDC, and felt better enough on Sunday to tag along to the convention, since I paid $60 for that entry pass, dammit.

Which I lost, by the way, some time in the chaos of the week and had to borrow Nancy’s. Also, I never thought I would ever buy suspenders for any reason in life, but this was it. (They’re black, so not really visible in the picture).

While I have no plans for Dragon*Con but to bring back this character in more detail, Cynthia plans on a full rebuild of the scythe, so I’d pay attention to her site in the mean time.

2.00gokart: Year of the Weird Angular-Framed Karts

It’s back!

This year’s 2.00gokart session saw record application and enrollment. I had 64 students, mostly mechanical engineering sophomores but there were some serious left-fielders like Architecture/Visual Arts (course 4) seniors apply, but could only take 20. Man, my acceptance rate is getting to be almost as bad as MIT itself.

I expanded the field to 20 students (i.e. 10 vehicles) this year because of the experience over the summer with dealing with 27. It’s incrementally not much worse, especially now that I’ve produced more reference and lecture material which has cut down greatly on the time-consuming basic questions. The operations are now much more streamlined now that I have experience myself.

The rule changes this year are very slight, but are again designed to put a little bit of a twist in:

  • Your vehicle now has to fit through a standard U.S. doorway, basically 33″ wide. Sorry Nelson. And like half of everyone from last year…
  • You now have the option of getting once nice wheel…. or two Harbor Freight pink wheels. Cue evil laughter here.

Besides that and some minor clarifications, it’s the same thing as last year.

As usual, the class started with a “demo night” where everyone got to see examples from last year, and past students dropped by to visit. Here’s dgonz giving a short informative talk about the dangers of “dgonzing” in your chassis design.

A few weeks in, and people have their first orders.

This year, I got sheets of hardboard (Masonite) from a local wood distributor for super cheap, so everyone got to prototype their heads off on the laser cutter again…

…before I committed it to metal.

There are a lot more teams daring to wander outside the safety of 90 degree angles this year, including Triforce-kart up there. Which I’m sure is not the actual name, but I’m naming it just like I’ve named other things “5-degree-kart” (for having a frame that is a 95 degree trapezoid) and “bus-ass kart” which… you’ll see later.

The hardware in general is more robust this year, I think in part due to the added lecture / reference content and the availability of more examples from past years. Remember – these don’t come from kits, each piece is cut or machined from the students’ own designs.

In general, the design diversity is up from last year, which is what I want to see. Here’s one of the three teams that have elected to do live-axle, but they’ve also went and bought a differential (and named it Humphrey…). All this equipment came from Surplus Center.

Electrical system-wise, Kelly + SK3 still rules, but there are more dual-motor drive setups as well as one team going super experimental and taking a shot at using the Trackstar 200 – the big one. I eagerly await the results of this test since I’m using one on Chibi-Mikuvan.

Speaking of which…

Chibi-Mikuvan

Ah, now the section that will take the longest since it’s about me!

In the past few weeks, I’ve completely welded and assembled (and painted!) the frame, plus gained much more experience using the Shopbot CNC router to make the foam cores for the body. I also tried making the battery pack housings, but there’s either some quirk of the machine I’m missing or my parts are all scaled around 95% in the Y direction. The frame is almost mechanically done, upon which I’ll focus on getting the electrical system installed.

In the last episode, I cut all the tubing parts to size but had not yet put anything together. I had one giant weekend of welding some time ago in which I assembled the entire frame. The first things to come together were the steering knuckles, which also mount the brakes.

After dialing in my practice again with those, I decided to work on the motor mount. Recall that I’m using an angle grinder gearbox to “preduce” the motor speed before it goes into a chain drive. What better way to mount an angle grinder gearbox than with the disc guard ring it comes with? I cut the ring off using the other large angle grinder, then wire brushed the paint off in the critical areas.

Here’s the motor mount welded up, along with some of the outer frame parts. I wanted to put together as much independently as I could before joining the long frame rails, just so there was less fixturing shenanigans.

In the welding room…

I made tack welds to the frame with a TIG welder, but then came back with the MIG welder to finish the beads. This strikes many people as weird – and it kind of is, since typically you do it the other way around. My rationale is, the TIG allows me to exert no force at all to make the tack, whereas the MIG will always have a little wire poking your part and could therefore move the fixturing.

Well why not fixture better? I think the reason I fixture tenuously – generally with only those red magnets – is the same reason why I can’t finish the weld with the TIG welder. Time and patience. I’m insufficiently patient to do a nice TIG joint, when patience is the key virtue in getting a good one.

Spray and pray!

You know what they say, though. A grinder and paint…

…makes up for a welder who ain’t.

To be fair, there’s no shitty welding on the frame, but I also don’t take myself seriously enough as a welder to say anything more insightful.

The frame was thoroughly cleaned with acetone first, then I put down a few coats of self-etching primer followed by black engine enamel paint.

Overall, after a day of drying, it came out very nicely.

I test fitted some hardware to gain more insight on the lengths of spacer needed for the front wheels. Now that they’re mounted, the front disc brakes look even more ridiculous. Seriously, I think I could stop 3 other sketchily-braked entries in the next PRS race.

Rear axle in bearing blocks installed.

A closeup of the front axle kingpin and spindle assembly.

It’s up on four wheels! No steering parts yet….

The steering column supports are a fairly classic tactic around here of drilling some holes in Delrin (acetal) blocks. Acetal is a bearing plastic, so it’s super slippery while being pretty rigid. Two pin-jointed blocks constraint a steering column at any angle you please, then two shaft collars (one on the bottom, one up top) constrain it axially.

The driving link at the bottom is welded onto the column – instead of bolting into a face-drilled shaft collar like on Chibikart. This is just for expediency.

This forms the extent of the mechanical work as of yesterday. Likely right after I hit “post” here, I’ll go hook up the steering linkage and use a vise grip as a steering wheel and get pushed around the hallways.

Here’s some Shopbot work making the battery pack sides and the bodywork!

The battery pack sides capture the Fusion Sticks into groups of 5 so I can parallel the cells. They’re 3D milled parts by design; I guess I could split them into 2D layers, but I wanted to learn the 3 axis milling mode of the Shopbot. The material of choice is a 2×10 chunk of sanded fir I bought from Home Depot. To stay within the PRS budget, I need to make this from something reasonably strong but cheap, and wood actually qualifies well there.

After roughing and finishing, the end result looks pretty good!

I made two versions. The one on top is both roughed and finished, and is the best quality. The bottom one was one of my attempts to shortcut the process by only roughing. The Partworks software that came with the Shopbot is sort of limited in the things it can do – it’s for beginners and general non-engineers, after all, so isn’t full featured like MasterCAM or HSMWorks. It won’t cut the part out in “roughing” mode, only finishing, so I tried to trick it into thinking the part was thicker than it actually is such that it would “cut out” in the roughing cycle by virtue of stopping too far down. This did work, but the internal features were then too far down also!

Seems like the only way to really make this work is to make sure the stock is thinner than you tell it, which couldn’t work in this case because the parts are 1.5″ thick and so is a “2 unit” dimensional lumber.

I’ll just put up with the extra 30 minutes of finishing. What’s weirder is that these parts are seemingly compressed in the Y direction by about .05 inches consistently, almost like someone put in a “scale 95%” in the program that I haven’t found. I’m going to try running another version sideways (long direction oriented in Y) to see if it is signficantly shorter, which would tell me “someone set a fixed scale percentage”, or still 0.05-0.1″ shorter, which would indicate to me an offset problem.

With some lessons learned making the battery sides, I started routing out the foam cores which will eventually be between the fiberglassy bread in the composite sandwich shell.

I bonded the foam together with slow-curing epoxy that was filled with “milled fiber” until it was pasty. Which is really overkill since it seems like 77 spray adhesive worked just as well, but let’s keep it legit since this thing is totally going into space after all. I made several bricks that were to contain the four sides of the body.

Foam is messy. You can’t use the dust collecting nozzle because it would hit the part, so the foam flies everywhere and generally covers everything. And it’s ultra static-y when you try to vacuum it up.

Doing a finishing pass after the initial rouging!

Foam machines like a dense air, so I set the machine to run as fast as it could. All of these parts finished in around 1.5 hours.

One  of the sides right after cleanup.

The foam was held to the MDF disposable surface by…. hot glue. That’s it. I drooled hot glue in a vaguely grid pattern, about 2 lines per foot, in roughly the shape of the part, then slammed the foam brick down before it cooled off. It worked great!

To dislodge the part, I used a giant dustpan to split the hot glue under the edges, then slowly pulled up with it.

IT’S ALMOST A THING

Too bad that I welded the front wheels 1 inch too far forward – mistaking the end positioning of a dimension while jigging it up.

This means two things: One, that the frame needs to be cut in 2 places, and 1 inch subtracted from one side and added to the other, or two, the body has to get split and a 1″ foam extension added.

I went for the second, since it would also make the gluing easier to manage (I didn’t have any 48″+ clamps). So I split the body in half on my hot wire cutter. A 1″ cross section will be made and bonded to the body, bridging the two halves, and the whole thing rejoined with carbon fiber rods running lengthwise to give the bridge some structure.

Bonding the rear panel to the two sides was easy, since it was nice and arch shaped. I just piled heavy things on top to keep everything down, and used 1 clamp in spreader mode to set the angular displacement (It wanted to lean to one side). For added legitimacy, I used the fiber-filled epoxy here, as Burt Rutan would.

The front half was also easy, just another mess of clamps.

I received an order of 2 gallons of Nice Epoxy yesterday, and otherwise have all the supplies needed to do the fiber layup on-hand. I’m hoping to get to it this weekend, but it miiiiiiight involve a little more psyching myself out beforehand.

For now, I’ll work on getting the frame to mechanical completion because then I can wave it in my own students’ faces to encourage them to finish!

 

 

On 2.00Gokart; Or, Designing a Design Class to Disrupt Design Classes as We Know It; Or, How to Make MIT Undergraduates Build Silly Go-Karts so You Don’t Have To

Oct 23, 2013 in Electric Vehicle Design, MIT, Bostoncaster, Cambridgeshire

I think I’ve promised a 2.00gokart “total recap post” after every session of it so far. This is a piece that is long overdue on this site, and in all honesty, probably also way past its time to present in a more formal venue. Edit: It’s now on Make Blog! Thanks Make! For the past now 2 years and four sessions, what I consider to be my most long and extensive project has been developing quietly in the halls here at MIT – that is, as quiet as the high-pitched whine of square-wave commutated brushless airplane motors can get you, anyway, interrupted periodically by the interdiction of concrete-backed drywall upon metal; facilities and my space directors will never let me live that down.

I’m two months late and running from when I first said to expect a wrapup of the summer SUTD special session I ran for their visiting students.  What this post will be is a ton of writing. Interspersed with as many photos and references as I can manage, of course, in my usual style of discourse, but most of it will be me waxing poetic – and perhaps polemic at times – regarding my own motivations to start this course, experiences in running it, and ultimately what my end goals are and where I want to see this class end up.

I anticipate this post being extremely long. In fact, so long that I’m going to split it into multiple sections ahead of time. What will be presented from here on is basically a much more concise, casual, and perhaps more profane and offensive version of my original Master’s Thesis, minus most of the the graphs and tables (because every Master’s Thesis in engineering needs graphs and tables, for whatever reason), and with more pictures and videos. The first two parts essentially amounts to me ranting, and the second half is the productive info, followed by more despotic proselytizing.

Here’s the table of contents: First, a summary of my motivation for making the class. Next,

  1. A brief rundown of my own history with engineering projects and how that both aided and hindered my academic performance at MIT
  2. How I took an interest in teaching and why I saw issues with the current system of design classes
  3. A history of my involvement and leadership in the electric vehicle design realm
  4. Recap of the 2012 class “2.00scooter”
  5. The changes made for the 2013 class “2.00gokart”
  6. The 2013 summer special session and the changes made for it
  7. Where the class stands now; content, procedural, and logistics.
  8. What I think the class brings to the world of design classes that is different or novel.
  9. More about the resource base of the class and the cost of running
  10. An SAE Asston (like an ISO/DIN Arsetonne) of lecture notes, resources, and links I have built up so you can run your own silly go-kart class

(more…)