Archive for the 'MIT, Bostoncaster, Cambridgeshire' Category


A New Beginning, Episode III: Revenge of the Charles

Nov 22, 2016 in Bots, MIT, Bostoncaster, Cambridgeshire, Shop Ninja

I’ve been doing a lot of these posts lately, it seems. Just last year, after departing my shopmaster/instructor position with MIT and hence no longer having a workspace there, I moved in to the Artisan’s Asylum, a local makerspace (which also happens to be the largest makerspace in the USA, founded and run for a while by the now creator of MegaBots). Now, barely over one year later, I’ve moved out again…

T H E   E Q U A L S    Z E R O   D E S I G N S   &   G R E E T I N G S   C O M P A N Y

…into something I can finally call “the shop”. God damn, remember when companies had REAL NAMES that didn’t sound like a syllable uttered while asphyxiating a small animal?

It’s about fuckin’ time. The hankering for workspace had reached a crescendo over the past few months between myself and Adam, my long-time partner in hood rat stuff & bad things, also now captain of Team Brutus. My recent contract projects have been bringing me newer, more interesting, and most importantly BIGGER work, and facing the prospect of having to also work on Overhaul again in a few short months (#season3), Artisans was becoming impossible. On the other hand, Adam has simply been making do without a permanent base camp for a while. Given both our proclivities and the rapidly rising prices in the area, it was another now-or-never scenario.


The building: a former clothing & sportswear factory which the company sold to new owners intent on eventually developing it into MOTHERFUCKIN’ CONDOSDO YOU PEOPLE NOT. HAVE. ENOUGH. CONDOS AROUND HERE OR SOMETHING? I digress. In the mean time, which means the next few years as they figure out exactly how ugly to make the new block o’ flats (that building being my local benchmark for ugly as fuck and overpriced construction) they’ve divided up the former factory floor into a few smaller parcels to function as rentable studios or offices, one of which fell into our lap. You can tell I really love the new property development trend in this area.

It’s on a typical “New England First Floor” – which means floor 1.5, with the basement halfway down. and us halfway up. So, no driving vans in, but direct freight elevator access to a real loading dock 6 feet below. In other words, just enough to be a pain in the ass and just good enough otherwise for me to deal, as the world likes it. The inside is stupendously large for both of us who have been conditioned to think that working butt-to-butt in a shared shop with Isaiah the Last Indie Wirebender is natural and acceptable. Nothing against you wire art, Isaiah, but my robots have tried to consume your workpieces several times while I was machining, and they’re really reaching their rebellious stage lately, so it’s better for both of us.

It’s ~2,300 square feet when finished – shown above is pre-construction of interior walls – putting it right about the size of MITERS. The multi-layered heavy wooden factory floor is finished in a classic “Inconsistently Leaking Machine” fashion sure to fetch thousands of hipster Bitcoins per month in the future when it becomes someone’s hotbox closet floor ,because weed is gonna be legal real soon now in Massachusetts! Oops… I mean #MakeAmericaStonedAgain-chusetts

With the beginning of the new shop space, so shall my Artisan’s Asylum presence come to a close. Luckily, most of my life is containerized. Not only did I count on having to move relatively often, as long as I didn’t own the whole damn block I was working in, but having stuff in nicely labeled containers appeals to my inner Jamie Hyneman greatly.  I bought a dozen more totey-bins (which by the way are called ALCs, or Attached-Lid Containers, but searching TOTEY-BIN returns the correct result on Google Images!) to more finely divide some of my parts since they would otherwise get too heavy.

By the way, it’s been physically verified that Mikuvan can contain 24 of these things – 26 if I use up the front seat.

As with moving out of any space or building or home, taking a look back once you’ve restored it to the condition you found it is a little somber. Alas, great adventures lie ahead! Onwards, through the skies, and across the seas… also over a few curbs, because 26ft box truck. You know what? Driving a truck in Cambridge ain’t so bad! You just BIG your way everywhere you want to go! Want to turn left? FUCK YOU! Want to merge onto Route 28 during rush hour? FUCK YOU TOO!  Uber driver? FUCK YOU SPECIFICALLY IN THIS FASHION!


The robots in their new homes, free to frolick in the open pasture… oh, none of them currently work? That’s too bad.


I picked a convex corner to slowly grow out of. While we have a “space plan” this is the two of us we’re talking about here, so everything is really coming together somewhat organically as needed, so long as it is vaguely understood to resemble some plan, if interpreted selectively. In other words, #yolo.

My former “workbench” at Artisans is made of a 60″ wide wire shelf, and it will become the new 3D printer farm and shipping center for Equals Zero Designs. Not shown here is a collection of Craigslist workbenches that appeared in the space some time later in the week.

As luck would have it, the IDC was getting rid of its original-issue fixed desks and cubicles to make space for more researchers. The large office desks that were a familiar sight in my build reports from 2012 onwards were going to get replaced with smaller, more portable tables. So what’s gonna happen to them?

They end up with me again. The corner I was in was the first to get cleared. While the desks were taken apart and shuffled, there is a very high chance that my former IDC desk is now in our new shop, another somewhat fitting and poetic closing of one of life’s little loops.

A photo taken later in the week of moving when the benches have been arranged and the IDC tables have been erected again. Notice that they’re a little crooked. They did depend on the cubicle divider walls for structure, which were not part of the deal. I might add some additional legs or some bracing to the desk later. However, for seriously heavy-duty work like “I am putting my laptop computer here”, along with EE work, they’re fine as-is. In fact, the widthwise span has already been set up as my EE bench as of the now.

Charlesland fades into Bercustan as you move rightwards above, with the border lying somewhere on a 3D surface defined by the location of the last series of hand tools we borrowed from each other. I’m going to build a wall of lipo batteries soon and make Adam pay for it.

Now, no new workspace that we have anything to do with is complete without….





My children weigh 4,600 pounds combined! Don’t you dare call them fat,  you droplet of coolant curdle!

Getting these two machines – the result of an industrial auction – is a worthy post by itself, and we learned a lot about rigging and moving heavy things that week. There’s quite a few resources on the Internet from people who have documented their own DIY machine moves, so I will gladly contribute to it. Let’s just say it involved….



 Don’t look at me, I wasn’t driving.

So what’s next? I’m basically moved in and have been hacking at things for a few days now. Ongoing facilities improvements will occur – such as moving the machines to their final spots where power will be run to them. I’ve been kept busy by contract work for most of this fall so far, but #season3 is on the horizon and I have some new and exciting content for the Beyond Unboxing series coming up soon, not to mention Brushless Rage development.

Welcome to Big Chuck’s Little Robot Warehouse!

Jan 17, 2016 in MIT, Bostoncaster, Cambridgeshire

Since December, I’ve been shifting operations over to my little safe-corner at the Art is a NSA-sylum. My ‘center of gravity’ is now over there, with only some big hardware still lounging around MIT which I hope to evacuate once I figure out space. Here’s what’s been going down on that front!

I decided to use a network of wire shelving carts and FIRST Robotics binny-things to organize storage and projects. That size of tote was on serious sale after the 2015 FRC game which involved moving them around.  There were two “densities”. One of them spaced the shelves around 15 inches apart, allowing a closed tote to be stored as well as allowing the usage of smaller 30-quart Sterilite bins which I had acquired a taste for in the IDC, but permitted the opening of neither in place (I  have to remove them). The other was build around 23″ spacings, allowing the large totes to be opened in-place and the smaller bins to be stacked.

Here’s my emo-corner after a night of setup. I decided to use the tighter spacing in the end since… let’s face it, I was more likely to put every little thing everywhere here, so might as well make more room for it.

I ordered two packs of FIRST bins. Once they arrived, it was time to get packing!

What I learned from this was that I had a lot of stuff. Gratuitous amounts of  stuff. And that’s JUST what fits inside approximately 10 bins! I have several go-karts and scooters that I need to find homes for, a rack of metal stock, and some other scattered builds and containers. These few weeks saw me unload a lot of stuff at MITERS and elsewhere, including LandBearShark, which has officially been adopted. Like the old LOLrioKart, you might see it surface again in another form with new operators.

Here we are now, on New Year’s Day, after another big move. It’s now feeling like home – once your 3D printers start moving over, that’s when you’ve truly settled into a space.

And yes, that’s my personal MarkForged machine! Go ahead. Ask me about it. I’m basically a salesman for them anyway.

I also have my own little export of the IDC electronics bench. Sourcing and dealing with the tools there has caused me to grown a liking to them, as well as allowing me to get to know their shortcomings and how to address them, so I got my own copies. The BK supply is still one of my favorite lab power supplies – the IDC ones have been regenerated into or accidentally shorted dozens of times by students. I purchased a WD1 station years ago at a MIT Swapfest event, and now finally have a proper place to use it.

The combination desk & EE bench will handle most of the RageBridge shenanigans, but what I don’t have yet is a more solid workbench for mechanical work.


Around the corner is a storage-only location. Consider it an evolution of Stuffcart. This uses the 22″ spacing for shelves, so I can open one of the bins in-place – basically cold storage for parts and whatnot. Not like I have a choice – the DC Motors bin outweighs me, for instance, and needless to say it’s on the very bottom holding the shelf upright. On the right side is basically all of Equals Zero Designs, plus some more robot detritus.

All of the shelves are on wheels in case I have to retool the spaces to do something in particular, or if AA is shifting around spaces; this corner is known as a “Pallet storage” location, where technically all your stuff should be on pallets but the keyword is “easily movable if needed” since the space membership cycles regularly and spaces open up or get eaten.

Finally having all my tools in one spot showed me that my single little rolley toolbox was not enough. It was time to move on up!

I #yolo’d this 44″ rolling tool chest from Harbor Freight on New Year’s Eve  as part of their end of year sale. While their prices generally don’t fluctuate much (as a devout HF disciple, I have a good idea of what everything costs yearround), it was on the low end again and… hell, why not. I immediately regretted this as I had brought neither help nor an appropriate vehicle, and it subsequently took myself and two HF guys to wrestle it into the back of Mikuvan after removing the pallet it comes on. This thing is quite beastly – it weighs 300 pounds empty and rides on huge aluminum-core casters. My only complaint is that it doesn’t come in Miku Blue.

What I might do is create a MDF and butcher-block top surface for it which bolts into where the handles and add-on side chests would go. That way I basically have a workbench built on top of this cabinet. Then at least I can hang things like a larger bench vise and arbor press, etc. off of the side, instead of having to source an entire other structure to have as a workbench. Anything heavy duty just gets walked over to the Asylum’s shop spaces – I don’t need to create a self sufficient bubble, just things which are a convenience and which don’t take up much space.

With stuff settled in and the space achieving productivity, it was time to move this coming year’s citizens in… Welcome to your new home, Sadbot. Don’t put too many holes into the drywall.

 what’s next?

  • RAGEBRIDGE 2!! After a month and a half of delay, Rage2s shipped from the PCB assembly house this week. It’s going to be an exciting week. If you’re a backer, prepare to get an update!
  • Overhaul v2 will be the  first “big hardware” project that this space takes on. I’m actually in the midst of trying to get special permission from BattleBots / ABC to blog all of it, from start to finish, including design and the work on Sadbot. Why? Well, first, because I can’t ever shut up about anything I’m building; you know that.But second, because I see the TV show as one grand chance to preach the gospel of engineering to a much bigger audience than I’ve ever done so before, and to show that building a robot of any sort is not something for ‘smart people’ or ‘the kids from MIT’ (a label which I’ve warned them I was fully divesting from this time). Showing the conception, design, engineering, fabrication, assembly, testing, and revision of one of these machines from end to end is specifically part of my agenda, something I was barred from doing the first time around because of the nature of the production. I hope to change this, or at least, be the only exemption. Maybe they can focus on OH2 as a specific side story thread or something. I don’t know, nor do I care about the presentation, so long as it happens.

That’s right, I’m fighting for the ability to disclose to you and discuss ALL of Overhaul 2′s deepest secrets, in immense detail, because I can’t be bothered to treat my favorite hobby & sport of 15 years as something that is magic to onlookers or have this notion that the secret-er I keep my robot, the more likely I’ll win.

That’s some kind of Apple bullshit, and I’ve never been a Apple fan. Let’s hope it works!

A New Beginning, the Second Story; RageBridge 2 FINALLY Going to Manufacturing; Season 2 and #SADBOT2016

Dec 01, 2015 in Bots, MIT, Bostoncaster, Cambridgeshire, Motor Controllers, sadbot2016

It’s official – after December 31st of this year, my contract with MIT as the MIT-SUTD Collaboration‘s International Design Center shopmaster will end, and will not be renewed. As of then, I will no longer have official ties to MIT. Hard to believe, eh?!

There’s no better timing for this, too, as #season2 is on the horizon early next year. My goal is to use this same epochal shock to usher Equals Zero Designs into prime-time, with the release of RageBridge 2 and a host of other stuff I’ve been working on this fall semester – stay tuned for that.

Ultimately, it was a combination of the fear of complacency as well as organizational changes that is pushing me to move on. First, because I have commitment issues and can see myself being a shop instructor & design class instructor for the next q years, which frankly scares the shit out of me. Sorry, ladies. Second, the IDC has moved on from its more “Wild West” days of supporting any which project, towards a more professional research-centered model with strong ties to industry. This is without a doubt better for the Center and will make it sustainable past its years with the MIT-SUTD collaboration alone, but I just didn’t see myself contributing to it any longer. I’m one of the last of the “original generation” of IDC inhabitants, and that presence has made itself painfully obvious in the preceding few months.

The thing I’ll miss the most is not anything to do with the Center, or even “my own” shop, but my interactions with the student maker community and being the go-to guy for late-night uncommon parts and advice, because yeah, of course I have one and of course I’m upstairs right now. That, and not being able to continue the great experiment that is 2.00gokart, but perhaps this will be remedied in due time.

In the coming weeks, I’ll be winding down my operations at MIT and shifting most of it over…

…to my little corner at the Art is a NSA sylum. What I might lose in the coziness of “my shop” I gain in a real, dedicated space for shenanigans and a much wider array of on-site resources and a massive community of deranged makey-types. Thus begins the story of Big Chuck’s Robot Warehouse & Auto Body Center. What, you thought I was kidding?

The downside? I have so much shit to move.

So many more people making and building things at MIT is a mixed blessing: nowadays nobody can get their own little private corner for too long. I’m currently trying to knock down my stuff load, which dates back to mid-2007, across 3 or 4 different sorting systems (at least 1 of which is just “NONE”), and several midden-esque locations. So, perhaps watch out on the For Sale page soon


Oh dear, I’ve officially become one of those delayed crowdfunding product people in addition to being just a crowdfunding product person.

Ragebridge2 got basically pushed back a month to resolve one of the biggest issues plaguing it from the start: the one channel “giga-mode” where the two sides are tied together so Rage becomes a single channel twice-as-awesome controller. A lot of prospective users were asking for this so Rage could conceivably be used in a heavier robot design. For example, the two sides put together at 150 amps limited would be plenty of current for, say, an Ampflow A28-150 motor.

Now, how hard could this one-channel thing possibly be? Isn’t it just copying and pasting the output of one control loop cycle to the other?!

Well, basically. But first, there were secondary issues that had to be resolved.


One thing that eternally plagues power conversion and motor control designers is noise. Switching tens or hundreds of amps thousands of times a second is not easy on sensitive logic. The bigger the parts get and the higher the amps go, the more likely you’ll start seeing things like optical isolation and fully isolated independent gate drive supplies, and the like. I think Rage is on the big end of what is basically “non-isolated” designs, where power and logic ground eventually meet on the same board. When they do, layouts and trace routing become as critical (if not MORE critical) than exactly what FETs you use…. I could have the most hardcore power devices in the world, and my board would just reset over and over if the current draw went over 5 amps or something if I dropped a haphazard or autorouted (shudder) layout.

Now, fortunately, for Rage, the critical current wasn’t 5 amps, but more like about 130-150 amps. On very hard reversing with the current limits near the top, the board would still trip up. However, it was no longer the microcontroller resetting, but the Allegro A3941 chips themselves that were having issues.  In fact, one side (channel 1) would preferentially shut down.

In fact, here’s a scope trace between low-side return (LSS) of the gate drive chip and my logic supply ground measured at the logic bus capacitor, on a 100%-to-0% step where I just kind of let go of the transmitter stick, with the current limiter set to maximum (75A) per channel. That’s a nearly 6 volt peak to peak smash, especially with a strong negative component. And this was at PWM frequency – happening 15,000 times a second.

If Rage were in dual-channel mode, this resulted in that side simply no longer responding, needing a reset to clear. If it were in single-channel mode, well… stuff generally blew up.

There wasn’t much more trace and component placement optimization I could make, however. I repositioned several of the gate drive traces, and more importantly, moved where the gate drive chips got access to VDD (system voltage) and VSS (system ground), specifically moving them away from “right under the drain tab”. I’m not sure why I even did that, but…

One last thing I decided to finally do was to airgap the whole logic ground plane.

Before, the plane filled the whole area that is now black in the center. This placed it right next to the high-power planes and the switching output of the motor, not to mention the high dV/dt gate drive traces. This is no longer the case.

All of these changes called for a new board revision, number 6. I decided to try a new-to-me vendor that I’d been clued into,, not to be confused with I see what you did there.

They have the quickest turnaround of any place I’ve used so far that doesn’t cost four-figures. I’ve actually since used PCBWay for a few more sensor boards and consistently get orders in on Wednesday afternoon, and receive them the following Monday, including shipping time with an air express service and which doesn’t even cost that much. The “downside” is no “fancy stuff” like 4 layers, microvias, plated holes and edges, etc… on your boards or it takes as long as it normally does.


It, uhh… Oops.

I’m pretty sure I clicked on the wrong choices for LPI (solder mask) color and silkscreen (text) color. The buttons are actually next to each other, okay?

Just in time for the cold season, the wild RageBridge gains a brilliant white winter coat to better camouflage itself against low-inductance motors and people who don’t know how to solder.

To be fair, this doesn’t look bad. However, the white board is easily stained by flux, and after reflow-soldering the FETs and gate driver ICs, there’s obvious yellowing of the board to a more ‘off white’ or ‘soft white’ kind of color. I think this is partly the flux, and partly because I cooked it too long. My process is not nearly as controlled as a production reflow line, so it’s not an entirely correct criticism. For production, I’m going to stick with black.

But did this revision solve anything? Quantitatively, I haven’t recharacterized the noise, but qualitatively, I haven’t gotten the board to reset or shut down in any way once. It will now happily grenade the power traces on a cross-side short, and continue working once I bridge the gap. This is all while driving a motor like 10 times larger than what it should be driving.

Well, that means it’s still blowing up in single-channel mode. It turns out there were quite a few structural problems with the firmware that allowed the input-taking loop to ‘override’ the current control loop. As the fastest loop in the code, the CC loop is what should be controlling the outputs at all times. The issue centered around passing variable values back and forth between the two loops. This itself was not causing the board to explode, per se. It needed an accomplice on the hardware side.

The other issue was that my deadtime between high- and low-side FETs being turned on was too small for the switching time.

The red trace is the gate of the high side FET discharging, turning the FET off, and the yellow trace is the corresponding low-side turning on. There’s very little error room here. It seems like the high side barely makes it off before the low side turns on.

Again, not very bad if the two sides were separate, but if they were switch together, all of the components better match perfectly. A few extra dozen nanoseconds here and there in delay and switching time differences would cause one side to be momentarily on while the other is off, or vice versa.  When this happened, there was an audible click from the capacitors as the cross-conducting FETs swished what must be peaks of hundreds of amps out of them and in a loop around the board. That was my sign to, umm, power everything off right now.

Prior to this, the board only exploded made terrifying sounds at very high throttle percentages (e.g. above 95%). I found out that the “output overriding” issues in the firmware were permitting very high PWM duty cycles, since the input-taking loop does not constrain its outputs to include deadbands on the low end (0-5%) and high end (95-100%). When this happens, it means the low side FETs occasionally turn half-assedly on and off due to the rapid on-and-off cycle.

I increased the deadtime to a safer margin to test again. The combination of correcting my variable-passing and adding more deadtime made for perfection! I just had to make sure that the outputs never went above about 95% – from there, it jumps to 100% – to avoid the possibility of one-side off (no FETs on) and one-side on, which is a slightly less bad case of one-side-high, one-side-low.

This jump is handled by a conditional in the fast (current limiting) loop. In practical use, this is almost unnoticeable (and is also used in RageBridge 1 and basically all other motor controllers, to avoid the things I explained previously)

With these issues resolved, Rage is now incredibly close to production. I’ve put in for the assembly quote and have already amassed the Bill of Materials. Associated tasks include getting quotes for heat sink manufacturing, and of course, in due time, readying the website and producing documentation. I hope to have everything out the door by mid-week, so Indiegooglers stay tuned for a huge update!


Way back during the middle of #season1, when we thought building a 250lb robot in roughly 5-6 weeks was going to be a breeze, I came up with the idea of a “practice assbot” for the 4 newer team members to construct so we can practice driving Overhaul v1 against it. Because, y’know, we were totally going to finish a week ahead of time and have time for everyone to take a turn at it and decide the chief driver on who’s the most skilled and… okay, that kind of died a little bit as we were welding the last bits of the new lifter assembly together on Tuesday night of production week.

But we were left with this tool, which just had to be used on something. The original plan was to put some wheelchair motors and tires on a square tube frame (leftovers from constructiong the OH1 frame) and throw this on a third of said motor. It would just be an irritating practice opponent.

During the brief interlude before #season2 work took off in earnest, I decided to take this project to fruition and adopt it, much like I am adopting the name and concept of Overhaul itself – more on this in detail soon, is my hope. I wanted first and foremost to have a 250lb-class driving practice machine. The difference between driving a 30lber and Overhaul was much like a small sports coupe and an overladen Chinatown bus. The second goal would be to test stupid experiments for Overhaul V2 (….more details on this soon, again, as I hope!) and basically make a “prototype” to make sure that certain bad ideas work, or are ruled out, before the proper build.

So I extracted OH1′s wheelpods from the apartment  and proceeded to think of the simplest, most durable frame I could build around it. Each wheelpod had four mounting points which were rubber shock isolators, so I just needed something to bind it together. A simple tube frame would have sufficed, but it was actually not heavy enough. To really get in the weight range I needed, there had to be much more steel.

My salvation came in the form of giant C-channel, specifically the “6 inch x 10.5lb per foot” type. That’s how it’s sold, pounds of STEEL per foot. In all, the thing above contains about 140lb of steel alone. Add in two roughly 25lb wheelpods and  batteries and it should be right up against ~220lb, so I could run this in other 220lb Heavy events if I really felt like it. The wall thickness is around 1/2″. It’s just a blob of steel.

But what it really needed was the Stick of Poking. For that, I conjured up a quick structure to contain a modified, chopped-down version of it.

The gear ratio may or may not be similar to one I intend to use in OH2′s main lifter, with the tip possibly kinda-ish at around the same distance as the anticipated new lifter, and it also miiiiiiiight be expanding on using the BaneBots P80 in applications most people would make fun of me for. All maybes. Nothing is certain at this stage, after all, and we don’t want to get too far ahead of ourselves, right?

I elected to use chain to keep it simple, with stock keyed shafts and sprockets running on stock mounted bearings. No fanciness here, just something quick to put together. The structure is entirely 1/4″ steel weldments from waterjet-cut puzzle pieces. I’m pretty sure it’s too spindly to be battleworthy, but again, I just wanted to see the numbers at work.

Oh dear, this thing is now looking too legitimate. I added some big rubber bumpers (which I ordered months ago for OH1 but found them too hideous to use, as well as heavy and improperly sized). Even if the arm is never installed or functional, at least it will be (relatively) soft with the big bumpers. Maybe I can use it to tow vans.

One of the intentions of this build is, of course, after all the experiments and bad ideas are finished, to have a sparring opponent for not only the future Overhaul v2, but also the potential storm of new heavy-class bots emerging in this area.

So, because the only purpose of this bot is to get experimented on and thereafter, shat on and beat upon, I figured it must be really sad, and so began calling it sadbot. It’s only tangentially related to #sadboys, I promise.

I ordered an unnaturally large quantity of STEEL compared to my usual daily recommended intake from Turner Steel, a local distributor, who delivered for free. By which I mean, dropping off slabs of a future overpass/bridge on the loading dock, and leaving me to try and budge it while making adorable squeaking noises like a rubber squeeze toy. If there is anything that building one (and soon to be 2, later three?) heavyweight-class robots is doing for my benefit, is MAKING ME LIFT, BRO.

To make up for it, building the frame was actually the most straightforward thing ever. Ignore the painted weeaboo face – I was somewhat delirious at that point. The cuts were made on a horizontal bandsaw, chamfers were gouged in with an angle grinder, and future weldment regions cleaned up with one of those fluffy paint remover wheel things. Word of caution: they are not fluffy at all, in real life. In fact, they throw chunks of hard plastic coated with abrasives at you.

After the mounting holes were drilled, I bolted the wheelpods in and actually used this assembly as a welding fixture. Long bar clamps held the sides in place at the correct height, while the whole frame was on wheels so I was able to push it around. In this exact form, I poured a few more pound of MIG wire into the frame. All possible edges were welded, both inside and out.

Having to build a heavy-class bot across multiple shops and buildings sucks. I should have invested in an engine crane and swapped some pneumatic tires onto it to sling this around. Pretty soon, this became too heavy for me to lift by myself safely, so I had to grab whoever was nearby. Here, the baseplate’s been installed.

Check out the 2×2″ hole pattern that peppers the 1/4″ cold-roll baseplate. I lined up the edges of the plate on the waterjet to make the pattern in one go. It’s like an optical table, except dorkier. This ensures I can attach any stupid thing I want to this baseplate.

The battery brackets are two pieces of 1″ angle stock, with a channel milled through each. The battery will be retained by a giant ratchet strap threaded through those channels. Each Overhaul battery is 37v (10S lithium) and 16 amp-hours. That’s literally 2x the battery we needed per match as reported by the chargers, as it turned out.

Here’s the pokey-arm tower cut, cleaned, and assembled, but not yet welded. Like the frame, I’m cheating and using the mounted bearings and shafts as a fixture to give some kind of perpendicularity.

The next step was to prepare the poker itself, which entailed drilling a 1.25″ hole through the solid 2″ diameter steel handle. I purchased an annular cutter off eBay for cheap, which are basically hole saws but actually built for cutting steel instead of just being coerced into doing so. I’ve always wanted to use one, but they’ve either been far too expensive or I had not needed to ever go through this much steel at once.

After using my cold saw to sever the handle to the needed length, I set everything up on the Bridgeport mill and gently massaged the cutter through in low gear. The process was utterly painless and the resulting finish was spectacular.

It’s almost like paying for the right tool makes your life easier or something! Go figure.

To-dos on #sadbot2016 involve welding the poker-arm assembly together and making some permanent temporary wiring to get it up and running. I’ll have more updates on this thing as the science experiment results roll in.


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!


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.


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.