Archive for September, 2013


The Mt. Washington Alternative Energy Summit, from the Perspective of a Not-Very-Alternative Energy (yet) Vehicle

Sep 29, 2013 in Events, mikuvan

“Summit”! Do you get it!? It’s a summit, like a meetup or conference. On a mountain! And you call mountaintops summits. Wasn’t that smart of them?!

I’ll never let that one be lived down.

It was an eclectic (dare I say electric?) gathering spearheaded by one of the area electric vehicle bros, Ted, and it all came together at the base camp of the Mt. Washington Auto Road. I was inhaled by the draft of everyone planning on going, a few days before the fact… with a broken window and all, and figured it would be a great chance to spy on everyone elses’ hardware and get some inspiration. And so, Mikuvan got to climb 4,600 feet to the summit of Mt. Washington (and get back down), and I got to see some of the latest production and custom EVs up close.  I summitted with the EVT Porsche, which was brought for the purpose of climbing Mt. Washington for the first time. I was part of the escort on the way up, and the… uhhh, “brake van” on the way down to prevent Shit Literally Going Down. Now aren’t I glad my brakes are in seriously awesome condition?

Early on Saturday morning, I pitched RazEr and Johnscooter in the van and headed north. Little did I know that they’d be both completely useless at the event venue, but hey.

The adventure begins with a roughly 3 hour drive to middle-northern New Hampshire. I am under the impression now that New Hampshire is made entirely of mountains, forests, and campgrounds. No wonder everyone who lives there is a freedom-loving rugged mountain hermit…

The scene of the event was the ‘base camp’ of the Mt. Washington Auto Road. The Road was nestled in a valley between two mountains, south of a little one-street town. To reach it entailed travelling on several small state roads, which threaded through additional little towns and settlements. I have this hypothesis that small-town America is homogenous across cultural regions, and I definitely felt the familiar vibe here as I did in southern small towns when I was younger.

Not sure if I’d be able to deal with the inconvenience of not being able to stumble downstairs and across the street at 4AM for a burrito yet, however. Clearly, Big Chuck’s Robot Warehouse needs an integrated burrito joint.

It’s early Saturday morning, and various exhibit vehicles are just starting to filter in.

These things were pretty rad. They’re Tribeys, by Black Sparrow Industries – think LandBearShark‘s more generally mobile cousin – you stand on these sideways like a board. They have a big hub motor in the back and a steering linkage controlled by rider tilt.

One of the highlights of the event was an original Stanley Locomobile – not the original which climbed Mt. Washington in 1904, but one from the same era. Looking at the technology on it really is a testament to how refined the modern automobile is, but all the same basic systems were recognizable. If I jacked Chibikart on 26″ slick bike wheels, it’s almost part for part.

It had an open differential. A very open differential. And exactly one brake – a big band brake wrapping around the outside of said open differential, occasionally, as the operator put it, getting doused in oil and grease from the driveline. Sounds like my kind of brake!

Why yes, this is my other car.

The usual commercial suspects – Nissan Leaves, converted plug-in Toyota Priiii, Volts, and of course Model Ssen, were present. At least two distinct Model Ssen rolled in and out throughout the day, and like 3 Volts.

One of Ted’s bikes. The last time I saw this thing was at the Somerville mini Maker Faire, when it still had a bucket of Hobbyking lipo packs. I got to ride this a few laps around the campground area – gobs of torque to be had from the Etek/Mars motor.

Another quirky “alternative transport” machination, the ELF. Designed for hybrid pedal and electric power, it’s more or less a trike with an outer shell.

Under it was a Crystalyte hub motor being used in a… not very hub motor way. I noticed a few of us had some laughs over this, but it’s a 100% legitimate way to use any motor, even a “hub motor”. Power is, after all, composed of both torque and speed, so for the same torque, you have more mechanical power if you can get more speed. Hence, running a motor on a higher voltage (than some reference design) and gearing it down more is a sure fire way to get more performance, and also a possible way to get more efficiency out of the system.

I’m a hub motor aficionado, so I took particular interest in everything equipped with hub motors. Here’s a full size electric motorcycle with not one, but two hub motors cleverly hidden in where the rear hub would usually be. The motors are discrete, so to change a tire off the rim, you’d just dismount the motors. Compared to a system where the rim is somehow part of the motor, or requires dismantling an endcap of a motor to get to, I think it’s a better system. Plus, more torque. Double the torque.

All flavors of electric rideables were in attendance, including this redneck cousin of Cap Kart. Lead and series-wound DC motors, still the baseline of EVs everywhere.

The alleged fastest street-legal motorcycle, Electracutioner. It used, of all things, a giant GE series wound motor mated to a rack of what I could only see as private-label Hobbyking lipo packs. Brute force motor with brute force energy.

Another fancy bubblecar, the Corbin Sparrow. Check out the “golf ball” texturing on the backside of the fenders – it’s also present on the underside rear of the vehicle. I overheard the designer, or perhaps a fan that sounds really like the designer, claim it makes a few percent improvement in the range of the vehicle.

The MIT EVT rolls up with the Porsche and a few other toys.

A few moments later, and completely annihilating the carbon footprint of the event, Adam shows up with Lipobike in tow.

By mid-afternoon, the event was at peak liveliness. You can see me desperately trying to ride RazEr around in the middle there. Hey, it worked some times – when the grass was flat, but not muddy, and not rocky!

Your “LOL HEY GUYS” picture for the weekend.

I didn’t really get any good pictures of the convoy starting to go up the mountain, but here’s the EVT group at roughly mile 5 of 8, pulled off to inspect the status of motor systems.

The Porsche nearing the top. There were several occasions when the upward-traveling convoy had to yield to downward-traveling traffic, and the Porsche… uhh, didn’t have enough torque to start again. Presumably it’s a rotor-lock protection in the motor controller, since it didn’t even try. A gentle push was needed to get it started again.

Maybe the Azure Dynamics controller is just a giant Hobbyking ESC inside.

And the group has summitted.

We stayed up at the top for about 2 hours, then began the careful trek down. I led the convoy down since I had a really tall first gear that basically made 20-25mph the no-effort engine-braking-only descent speed (and which makes for surprising agility in low speed city maneuvering), so I had braking overhead to stop anyone else just in case. Every 2 miles, the convoy pulled off and students scrambled around with IR thermometers to check brake temperatures. The Porsche consumed about 50% of its pack on the way up, and regained something like 25% on the way down, and Model S owners were reporting 25-30 miles added back to their ranges.

It shows that regenerative braking is 1. pretty cool and 2. not entirely bidirectional on the average because you can’t capture back most speed-dependent steady state losses, and batteries do not charge and discharge symmetrically. Regen is often touted as some kind of miracle in EV marketing and very misunderstood. Maybe it’s time for an Instructable…

Here’s one of the “nice pictures” I took at the top.

And one I took on the way up, near the 4 mile marker!

The party ended around 3PM, and pretty much everyone was back in town by 7PM.

stuff lurned

Overall I consider this a worthwhile adventure, and it showed me a lot of the smaller end of EV hardware (plus, I got to van-camp for once!). Unfortunately there weren’t any custom electric car conversions, something I was sort of itching to see. Essentially, I was hoping to use this trip as a mental make-or-break for the still-on-the-agenda EV conversion, I swear. I figured the next 5 to 6 months was a period of time when the weather around here is too damn disgusting to drive anywhere, so if I could be convinced that the work could happen during that time, then I should begin immediately.

That how it would proceed if I had infinite money, anyway, since in my estimates I would probably still need to drop the higher end of several thousand dollars to get an electric powertrain for Mikuvan operational nicely. Not a motor and a knob glued to the center console, but functionally transparent to how it is now. It’s really not prudent for me to try and assume that I can consistently spend a ton of money over the next approximate year at this point. I am, after all, not yet Elon Musk and cannot yet troll space, and the last thing I want to do is to get halfway done, then be forced to give up or abandon the project for some reason.

Besides, you don’t just take apart something that has gone almost 7,000 miles in the past five months (early 4/5ths of that just by means of epic road trips) without so much as a hiccup or misfire, then put it back together in a less useful (comparative) position – that’s taking apart the castle for the stones when you have to spend thousands of dollars to pile the stones in the shape of a slightly different castle, all for your own amusement.

So yeah, I’m still totally in denial about it, but I think Mikuvan will remain stock for a while to come. That, or it’s time for another van!

Mikuvan and the Broken Windows Fallacy

Sep 25, 2013 in mikuvan

Continuing on the trend of “Charles writes about stuff that actually happened like 2 weeks ago”, this is the tale of how not to follow service manual instructions, and then how not to do bodywork. But I’m glad to say all is actually well, and it’s not as bad as I make it out to be in that sentence… though I am still out about $350 total for a new rear hatch window.

Immediately post-Dragon*Con, I was planning on taking the early fall lull in activity (read: I don’t want to do anything useful for a like a month after Dragon*Con) to get some pressing bodywork done on Mikuvan. I bought the vehicle originally with a line of rust and bubbly paint on the rear hatch window’s bottom sill, a telltale sign of some bad or shady window repair work that damaged the paint or something a while back:

It had only been deteriorating since April, with the bubbles slowly flaking off and the rust stains spreading. I decided that it was now or never in order to tackle it, since soon the weather here would be getting too cold and wet – the only real venue I have to do this kind of stuff is outside. Some time the week after D*C, I decided to try and remove the rear window to assess the damage in detail.

The rear window is retained by a thick rubber gasket that’s S shaped. One ‘fjord’ of the S envelopes the outer edge of the glass, and the other one grips the inside of the hatch, slung across a perimeter ‘pinch weld’. I had heard of various tricks involving a greased string wrapped around the outside to work the gasket out of the frame, but that sounded a bit kinky to me, so I consulted the manual:

..okay then? Here goes nothing…

Well shit.

I’m guessing this was another one of those situations where “Pry with screwdriver” means something different to a mechanic or auto body specialist than, say, me. I got about 3 inches of the gasket out from the inside before seemingly prying incorrectly or something – as you can see above, the fracture started from the end of the right side of the seal. The sound was best described as “polyphonic gunshot” as the propagation of fracture caused the sound to be spread over a few hundredths of a second. It took me a few seconds to realize this was going to be expensive.

More importantly, I was worried about finding a replacement glass at all. It’s one thing to get glass for a GM econobox, but there weren’t many of these vans sold in the U.S. in the first place, and most of them surely have dissolved long ago. I was ready to start scouting the Canadian Delica forums for someone with a parts car.

But I seemingly got lucky. I first hopped on Rock Auto, my favorite parts house, and they somehow had 1 item in stock for “Rear Window Glass”. Figuring that they couldn’t be too wrong, I decided to give it a shot.

In the mean time, I consulted a few area auto body shops to get estimates on glass replacement, including my favorite in the area, Chicken & Shakes:

Sadly, they did not do glass work. What I learned is that most reputable glass shops won’t take customer-provided glass – they had to source it for you. Something about warranties, I wasn’t sure. Whatever the case, enough asking around got me a contact with Jose and Jesús, who will pop my new window in for $80. I’m convinced that this is how things actually get done in the world – you keep digging until you find some dudes who just don’t care about The System who’ll take care of you in like 10 minutes. Kind of like how I run my shop.

Now that I got an estimate for the installation, it was up to me to strip away the rust and seal the window frame before my glass came. The first step was to amputate the remains of the window:

I set up a plastic drop sheet that went over the rear seats and extended a few feet on each side, then I ripped out the clear packing tape that I had paved the window over in order to hold it together for the time being. Then, some selective hammerwork freed the crunchy window and it all fell out in roughly one piece. You can already see some of the cancer that the gasket was hiding.

Oh boy, this was going to get interesting. I was really, really hoping for just some bubbled paint and rust spots I could wire brush out, but this one looked like it had depth.

A lot of depth. In fact, I think I started chipping off about 5 different peoples’ Bondo jobs. I was suspecting that most of this rear hatch was made of Bondo, but it still sounded metallic when struck, so I figured it wasn’t too bad. But Bondo is moisture-passive, so the steel had begun rusting out again underneath it, presumably from a single crack in the repair.

Cleaning out the gasket of broken glass bits while I formulated an attack plan.

I had hoped to take the intervening week between the glass order and when it arrived (and when I’d have to call Jose after he got off work at his real auto glass shop) to make all these repairs, but the Media Lab class and other shop-herding commitments meant I neglected to do this. Next thing I knew, my Rock Auto order had arrived.

Well damn, it actually is the same glass! It carried an original manufacturer’s sticker, so I was probably looking at a piece of glass older than I was.

It was the Wednesday before Maker Faire New York, I had promised to carry six MITERS frosh (and non-frosh) to New York, and I was not going to do it while missing a rear window. This shit had to go down now. What follows occurred from roughly 10PM Wednesday evening until 4 or 5 PM Thursday afternoon…

Oh, and I now need to add the NYMF to the list of things to report on ex post facto

Because the evenings around here were now in the mid-50s and high 40s, it was too cold to paint or use any crosslinking compound (e.g. polyester resin based Bondo). I pulled into the auto shop, carefully nudging the EVT Porsche and Solar Car out of the way, closing the garage door with about 3 inches to spare. Some more plastic sheeting was set up to enclose the rear hatch area.

The plan was to grind and wire brush as far down as possible to expose metal first. Then,size up the situation and decide if hammering in some replacement sheet metal or laying up fiberglass was a more viable option.

I used a crimped coarse wire brush first to knock away most of the loose material, then switch to a flap disc to do the more heavy duty removal. I returned to the wire brush to hit the corners since it was more flexible.

This thing was like a fuckling Jawbreaker candy with its layers of filler and paint. Check out those strata that geologists would murder for.

I went into this with no intention of restoring the previous repairs’ contour, because the stuff was around 2mm thick in places. I was basically out to get the repair well-sealed and the area somewhat smoothed just so it didn’t look like total shit. Patient hand-sander I am not. I’m rolling with the assumption that there will be a day when I have enough money to get this thing fully resprayed and repaired by a professional shop, and my mission is to preserve it until then.

The open-pit mine has been expanded as far as I felt was adequate to start on the fix itself.


I found three of these riveted patches on the rear window seat, suspiciously equally spaced. A bit of research led me to the discovery that these areas originally had small drainage channels to collect water that got behind the gasket, but they could become blocked easily and hence trapped water instead. This would explain why they rusted out and were repaired first.

That’s one hell of a shoddy repair job. It’s two rivets, one of which was totally hollow, so there was no way it could have been waterproof. The rest of the patches were the same.

By now, I had formulated the battle strategy – cut out the steel patches and go over the gap in fiberglass. I had, after all, invaded Solar Car territory, and at my disposal were rolls of fiberglass cloth, fiberglass and epoxy resin, and semi-infinite Bondo.

I used a metal cutting wheel in my trusty $14 Harbor Freight angle grinder (yes, all this work has been done with a $14 Harbor Freight angle grinder – yes, I’d recommend it to anyone) to slice out the steel patches.

I kept the one with the little rust monster, by the way. It was too cute to throw out.

Now I had 3 roughly equidistant holes in the hatch.

The fiberglass cloth went on in 3 layers, one after the other. I first coarse-sanded the area for better adhesion, then painted the resin around the area to be patched. The cloth was laid down and manually pushed into roughly the right shape. More resin was “poked” into the cloth with the application brush in order to saturate it, and then a larger amount was painted on for the next layer.

When all 3 layers were applied, I began pushing the cloth into shape by poking it with the brush again. As it turns out, this seems to be the easiest way to maneuver the cloth into shape by small amounts. Then, it was left to set while I worked on the next one.

By the way, I’d never done any composites layup of any type before this. I made this up completely on the fly after watching a few Youtube videos.

(The big air bubble on the right side was tamped down right after taking this picture…)

The time: About 3am on Thursday, and all 3 patches have been. applied. These were left to cure for several hours while I jumped in and took a nap. The light source is a 500W halogen work light that I pointed at the area from a few feet away in order to keep the metal a little warmer. The shop is not very well insulated, so it tends to follow the weather.

The time: About 6:30AM Thursday. Woken up by a contractor crew barging into the building, I began applying Bondo in small amounts in order to soften the edges of the fiberglass. I was not going to mash enough on to restore the original contour. Bondo says it needs only an hour to cure before sanding, but I found it was still a little flexible after that, so I gave it two hours. Notice the slightly different colors indicating different passes.

The time: About 9am Thursday. Enough was enough, it was time to start painting. No, the contour is not perfect at all and I’m sure you’ll be able to see it from a mile away…

I used 60 grit sandpaper on a power sander to blast the peaks and valleys down to a more smooth condition – notice the “bondo strata” becoming wider. I ran a finishing pass with 220 grit which I also used to rough up the surrounding area for better paint adhesion.

I used more plastic drop sheet to mask off the areas that I wasn’t going to repaint. There’s going to be a curiously new looking band of white across the back of this thing. I only had (read: The two surrounding Advance Auto Parts only had) enough of the specific shade of Chrysler white I half-assedly matched to the existing body color, so I couldn’t redo the entire rear hatch.

Picking the color was a bit of research work. None of the generic Ford or GM or Toyota colors offered were good visual matches, but then I remembered that Chrysler was basically Mitsubishi (and vice versa) in the 1980s and 1990s, and a bit of Intergoogling confirmed that some people were using Chrysler colors to repaint old Mitsubishi cars. Lo and behold – Dupli-color’s Chrysler “Bright White” was a near perfect substitute.

It’s about 9:30, and the first layer of primer has gone on above. I took the advice of the primer can and laid it out in four thinner coats, waiting about 15 minutes between each, and one hour after the last one.

Essentially noon now, and I’ve done the first layer of white (what the hell is this called anyway – base coat?)

The can of touch-up paint wasn’t enough to finish the 4th and last layer, so I ran off to the local Advance Auto again, which thankfully had 1 more can in stock, making it back in time to throw the last one on before giving it an hour to cure in order to prepare for the clearcoat. The time was about 2PM.

For the clearcoat, I removed the plastic dropcloth from the outside of the tailgate and gave the surrounding area a very find sanding with 360 grit. This was to ensure overlap of the clear coat so I didn’t have a bunch of exposed paint seams. To apply the clearcoat, I just aimed more carefully so it didn’t get everywhere, but contoured over the new and old interface.

Looking down the width of the new repaired area, you can definitely see the low spots in the fiberglass, and some of the ripples in the Bondowork. Whatever. Maybe those low spots will simulate the rain channels of yore.

I rolled out of the shop around 4:30PM Thursday. Overall assessment of the repair? Whatever, I did it in 18 hours and didn’t pay anyone money for it. Not that I would have accepted a repair of this visual caliber from anyone else but myself.

If I had taken just one extra day, then I could have done a much better sculpt of the rear hatch contour so Bondo lines weren’t visible all over the place. But this is a valuable lesson for next time – none of this was as hard and weird as I originally thought. I just really want some little rental car damage inspection stickers so I can make a note to myself which areas are made of solar car goo instead of steel.

Friday afternoon, I bumbled into Jose’s shop with the new glass, and watched firsthand as he and Jesús slung the window on in a minute flat, using the Inverse Greasy String Method (after some minutes of prep work, I mean, like wrapping the gasket back around the glass). They then filled the gap in the gasket with polyurethane sealant and a section of generic weatherstripping.

The hell. Professionals, man. They didn’t even grease their string! Seriously!

Look closely on the left side and some of my “handiwork” is easily visible. From a distance, you can’t really tell – only up close and if you are looking for it. Or if someone runs their hands along that section under the window, but if someone else is feeling up my van, I would probably take issue with it anyhow.

There it is – how I dove head-first into bodywork and learned definitively that it’s a thing which takes time and patience and those other virtues I don’t have, but isn’t that mysterious and fearsome either. The “Death Race 3000″ school of automotive repair is looking more attractive now!


The Dragon*Con 2013 Complete Roundup, Part II: Event Recap and Maker Resources

Sep 19, 2013 in Bots, colsonbot, Events, mikuvan, Twelve O'Clocker, Überclocker ADVANCE

So here we go – now that Part 1 has had some time to sink in, and now that my shop is looking remotely functional again, it’s time for some part two. In this section will be the two new ‘sections’ (carried over from part 1):

  1. Operation GIVE ME A BRAKE: Brake system and inspection all-around on Mikuvan!
  2. Pad Thai Doodle Ninja, an Antweight 4-bar pushybot I designed and built in like 72 hours!
  3. The trip down, the con, and how the bots did at the event!
  4. The links and documents associated with my two panels at  Dragon*Con.

This semester, the two fabrication labs I oversee in the MIT-SUTD Collaboration is once again playing host to How to Make a Mess out of Almost Anything:

Yeah, it’s going down about like that. Unlike the last two academic terms (January – August, basically), I’m not “running” a class this term, so it’s going to be way more chill. I’m not sure if I will want to run back-to-back design classes again like the consecutive 2.00gokart and “2.00GLP”, since the overall level of intensity and chaos is extremely high. I see how the department can go through design class professors rapid-fire now.

Anyways, back to the trip. It’s Tuesday night! Time to load up robots.

Dragon*Con 2013

…but first, I need to get my 200 pounds of tools, accessories, and spare parts out of the back. I left a spare tire, van-specific tool box (like my robot-specific toolbox, but everything is bigger!), and spare fluids. The floor jack was removed since there is a bottle jack for tire changes in a rear compartment. Basically I was purposefully blocking myself from doing any roadside extensive work – I think I’ve gotten everything mechanically to the point where a failure necessitating deep dissection is practically going to be catastrophic in nature and not something I’m going to do in a parking lot.

Replace all the van kibbles with robot kibbles. I guess I could have kept the van kibbles in the back anyway, since I was initially expecting more bots and parts. This stuffing was, consequently, not as epic as the Motorama Stuffing or the Last Dragon*Con Stuffing (though those vehicle did have less hatch space to begin with). The ship-out time was essentially midnight.

Around 4, we reach Flushing, New York, where Xo Has Joined Your Party. This is where the trip got a little more interesting.

In 2007, before I was a wee bunny at MIT, my parents and I drove up to visit the place. We took I-95 in all of it’s forms through DC, Baltimore, Philadelphia, Newark & New York City, then up through New Haven and through Rhode Island. My only memories of the trip are of how I-95 was utterly depressing in every way, from tolls to traffic to construction, and the general level of suck the Northeast urban cluster exhibited.

Six years later, I was meandering up the Bruckner Expressway in the wrong direction when I hazily decided that maybe I-95 wasn’t as bad as I remembered. Plus there was like an exit for it right there and if we kept going semi-lost I’d end up back in Connecticut. So, down 95 we went, across the George Washington Bridge (slowly, because construction and late night truck traffic), and down the New Jersey Turnpike, the fancy Delaware Bridge thing, then down onto Baltimore and onwards.

I’m glad to say that 95 is every bit as depressing and repulsive as I remember it and that nobody venturing out of the Northeast to anywhere should ever drive on it for any reason.

All together, I think between Queens and Baltimore I busted $35 on tolls alone, not even including the relatively minor tolls in Massachusetts. Every bridge or turnpike had its own toll authority.

I thought the Interstates were supposed to be full of FREEEEEEEEDOOOOOOOOOOOM.

In the Baltimore-Washington area, I stopped at my favorite IHOP in College Park, MD. This has been the focal point of several Otakon trips. South of Baltimore, we hit what I like to call “Facebook traffic”, where congestion is so bad and traffic is so stop-and-go that everyone is on Facebook complaining about it. This took about 2 hours to sit through because we came in at the exact time to hit traffic in both metro areas. How are you actually supposed to get to work?

We hit Atlanta around 10PM, for a trip duration of essentially 22 hours, many of which were spent fucking around with the abomination that is 95 in the Northeast Corridor. For instance, it took about 45 minutes to even get out of New York. Then factor in the fact that the cruising speed of my lovely pallet of cinder blocks was about 65 to 70mph.

The next day, it was off to the Invention Studio to get the band back together. Here’s the shot of the trip:

We journeyed a little off campus to get lunch, and in the parking lot of the local small sketchy college restaurant cluster was an Audi R8. Like most expensive cars, it was parked “haphazardly”.

This year, since I brought actual working robots, and because Pad Thai Doodle Ninja was completed the evening before the con really kicked off, and because I wasn’t trying to speedball an entire new bot in 3 days,I got a lot more wandering and people-watching time. I was especially tuned to try and find people with costumes that looked like they required some amount of mechanical construction or engineering (see my brief on this last year).

That, and giant Totoros.

Here’s a good example. This funky gun-like prop had a ton of lovely CNC aluminum work. The wielder, though, wasn’t the builder.

I spy a little of waterjetting on some of those interior parts!

The thing I’ve historically liked the most about Dragon*Con over other gatherings is that there’s no particular theme. The con covers about every niche of culture, up to and including robots. You’re not even going to find that at PAX or Comic-Con. This enables people to mash together different story universes and characters with much more impunity, for the amusement of all… such as Portalmau5 up there.

I’ll be honest – this is pretty much the only reason I went to the actual con for, besides my own panels. No, not just any group of girls in costume (that’s so last year), but specifically one series. The latest thing I’ve been fanning over is Monty Oum’s RWBY, also known as “Charles has to build shit that Monty designs with ill regard to constant-volume systems”. Most of the characters are Action Girls with giant mechanical transforming weaponry – what’s not to love? The thing that hooked me at the beginning was the RED preview.

The series so far has really pinged my “defer judgement” sense, since to me it seems a little hurried plot-wise and is seemingly laundry-listing TVTropes (site left unlinked because I don’t want to sink everyone’s productivity for the next 11 days) on purpose. But I’m proud of my ability to cherrypick favorites very specifically, so I’m still into the series for the giant mechanical transforming weaponry.

The series is so new that I wasn’t sure if anyone was into it enough to plan costumes, and I wanted to get a sense of what is already out there in terms of mechanically actuated versions. Conclusion? Zero. On the internet, and in real life at the con.

That’s where I come in.

…not right now, though. With Saturday winding down and the Robot Microbattles just around the corner, it was time to intensively practice driving. This was the remains of a laser-cut quadrotor frame that everyone’s 1lbers and 3lbers were beating on throughout the evening. I also repaired Colsonbot by printing a new motor mount carrier and replacing a stripped drive motor.

This year, Microbattles got the entirety of the International ballroom at the Hyatt Regency Atlanta. In past years, the event has only gotten half the space, and the audience had to be capped every time. The event size is now on par with the main Robot Battles, with even more entries.

So many, in fact, that single elimination had to be used for the tournaments again, and we still ran overtime. The event has been running against its time limits (and beyond them shamelessly) for the past 2 years, and this year was no different. Hopefully the D*C planning committees finally recognize this.

The Atlanta arena returns! This year, an actual 12″ sanding disc was mounted on the spinning turntable. I’m glad to see that my contraption is still functional. During the event, it produced quite a few light shows from bots being stuck in the hole, and reduced the diameter of a few wheels.

The usual suspects were in attendance. Here’s the table of G3 Robotics & Variable Constant & Guy Who Never Updates His Website.

This is a reasonable approximation of the audience during the day. The added seats and projection screens helped crowding immensely. Because the arena has a pretty high bumper rail (3″ or so), and it’s up on a stage, you can’t actually see the bots from the audience unless something exciting happens, so it’s entirely dependent on the video crew!

microbattles results

Because the Antweight tournament was single elimination, sadly Pad Thai Doodle Ninja only got one match in, against the veteran Segs (pic from years past, to the left). Cynthia put up a valiant driving effort, but the lack of “lifter lip” on the arm meant it had a hard time getting under Segs, and the bot was twice as slow as originally planned.  Near Chaos Robotics, filmer of events, recorded the match in two halves: Part 1, Part 2.

In the rumble, PTDN got into the thick of it and pushed a few people around, then got pinged a few times by DDT. The lifter arm was bent up,  but the bot otherwise had no permanent damage and still drives.

Showing why extending the front armor to the floor might be a bad idea – check out the crimps on the left side. After the DDT damage, the bot had trouble maneuvering on the floor.

Rear view of the damage. Because DDT pinged the arm while it was partially up, the force ripped the rear link out of the arm. That part was extremely thin-walled to begin with and should have been thickened, but I was afraid of it interfering with the robots’ self-righting. Turns out that wasn’t a problem.

I do want to fix up PTDN and upgrade the drives to the original 10:1 spark motors I had intended, and redo the front armor. The lifter servos will either be consolidated into one higher torque metal gear servo, or two digital servos for better range matching.

Colsonbot, sadly, was unable to colson much because of the unrepaired damage from Bot Blast. The “duallie” O-ring wheels were beginning to come apart, and the O-rings tended to slip off and get caught between the shell and the bot. It survived the event pretty much unscathed, however, and I don’t intend on making any big changes to it save for remaking the wheels into single-o-ring affairs that have more ‘stretch’ on the rings themselves to prevent them from twisting out. Colsonbot got in one match against Radiobox, and also the Beetleweight rumble where it was mostly a stationary arena hazard.

big bots

Back in the Invention Studio on Sunday night, preparing for some final tuning and drive testing. Null Hypothesis had to have a drill motor replaced, but otherwise, I didn’t have to do anything to the bots for once.

At the event, while I was testing Null Hypothesis on the stage, it randomly blipped and stopped moving. The cause was traced to the controller completely losing its gate drive power supply for some reason. Whatever the case, it necessitated an in-field replacement, which Adam is handling.

Most of the builders are seasoned & flavored veterans, but there were some rookie builders this year. It’s good to see the sport grow organically, if not somewhat slowly. This bot is an alleged 12lber – according to the builder, it weighed 14 pounds when finished. Oops! And hence, it was named. It ran without any top armor at all – something which ended up causing it to lose to 12 O’Clocker.

Omegaforce returns, with more unique wedge attachments. The outer and inner wedgelets are linked together in such a way that the outer set lifting upwards for any reason causes the inner set to drop down to the ground. The upper wedges can swing all the way backwards. So it’s a multi-tiered defense system against oncoming opponents. The actual functionality was a bit spotty.

Non-rookie builder (I met Miles at Motorama 2013) but first Robot Battles event. The center of this bot was supposed to be a lifter, but some things didn’t happen in time. And yes, it’s entirely made of wood. I was hoping to face this with Überclocker, but didn’t get that chance.

Another rookie bot that was supposed to have an attachment in the middle (in this case, a hammer) but Stuff Didn’t Happen.

Überclocker 30 charging before matches began.

12 O’clocker after its first match, which I won. I learned that the springy legs worked well, but they were not well constrained downwards and could get pushed to the point where the front wheels of the bot were propped off the ground. The contact point they make with the front axle standoff should probably be modified to capture the leg in either direction – up or down.

This is probably the most quintessential robot even picture I’ve ever taken. Equipment all over the table, Mountain Dew everywhere, and “beasting food” as I like to call it strewn about.


I try to post audience pictures of Robot Battles every year, because it really is a phenomenal show. I think the audience averages 5 or 600 people and can peak near a thousand. In quite a few years that I remember, the hotel had to deny people entrance because it became standing-room only and exceeded the allowed occupation of the room. Here’s the right half of the audience…

The center…

And the left half.

Oh, this was before matches started.


I’m extremely proud of the bots’ performance and reliability this year, as well as the show they put on. For my 10th (!) Robot Battles it’s quite refreshing to have things that worked. The robots ended up losing only due to my own mistakes, or my tendency to favor a good show over winning at this event. I actually can’t bring myself to just drop someone off the edge cleanly with the Clocker pair, and this did bring about my own downfall a few times…

Regardless, Überclocker 30 got 2nd place in the 30lb class, fighting Null Hypothesis (oops…), Overthruster , Null Hypothesis yet again, Jaws – probably my most favorite Clocker match ever, Overthruster for the nth time, and finally losing again to my eternal nemesis Nyx. Overall record of 4/2. There were sure lots of reruns this time around. Clocker was a crowd favorite in the past, and now even more so since it works pretty reliably. At the very end, during the rumble, I did lose the drivetrain completely, most likely due to the solder joints breaking off the motors – this has been a weakness of the bot since Motorama ’13 that I forgot about until now.

12 O’Clocker finished what essentially is 3rd place, since the winners’ bracket finals loser and the losers’ bracket finals winner were the same bot. In the final match, I just got plain outpushed by a more powerful and faster opponent. 12 O’Clocker was also a crowd favorite, possibly more so than Überclocker itself, if I could judge the audience well, and went 3/2.  12 O’Clocker’s match videos: Tetanus Shot 1, Oops, Omegaforce, Apollyon, Tetanus Shot 2

So what’s next for the robots? Besides the odd demo or sparring match, it’s time to make the upgrades for Motorama 2014 next February. Überclocker’s current form debuted this past February at Moto ’13, and I don’t anticipate making any changes to it at all (except for actually using the Quick Disconnect style terminals on the Dewalt motors, maybe…). The new actuator on Überclocker’s clamp worked as I expected – I could grab and hoist up opponents very quickly, and the multistart leadscrew eliminated the binding it was prone to perviously so I no longer had to be gentle with the stick – RageBridge took care of the “endstops” by entering current limiting mode. On 12 O’clocker, I want to better secure the front legs, but otherwise, the bot incurred no damage from this event.

the way up

I decided to be intelligent and finally take a route which I’d been eyeing for years, but never dared try for some reason until now:

In my opinion, this is the most direct possible shot through to New England without going near any metropolitan agglomerations. The plan was to detour north at Charlotte, NC. and follow I-81 all the way up to Motorama Harrisburg, from whence my general solution has been to go east and up-around New York City through 287, then cutting north out of CT on I-91 and I-84. The upper half of this has been tried and verified many times.

I think this was a good decision. Not only was it smooth all the way, but the western VA and NC scenery subtracted from the boredom greatly. We passed through, and stopped in, a few small towns and villages nestled in the Appalachians, places that I’m sure high flying urban folks around here don’t give a shit about. It was, in my view, a more authentic American experience.

Stopping for a fuel and breakfast somewhere north of Roanoke, VA.

daily van bro

I saw something which looked out of place across the street at a convenience store. Turns out it’s a Greenbrier, one of the original American compact vans built to compete with the VW bus! These are rear-engined, just like the VW bus, but the Ford Econoline of the same era was mid-engined and rear wheel drive, and the layout was directly ported and evolved by the Japanese. So, really this is an evolutionary ancestor to Mikuvan.

It was also on sale. I called up the seller, but sadly the price asked was out of what I had in my pocket at the time. If I were into these things, though, it would be a very fair price for a vehicle in as good visual condition, and as good running condition as the seller described.

Compared to almost all modern cars, I’m pretty damned small, but the Greenbrier was somehow even smaller. And it had 3 rows of bench seats.

The rest of the trip up through Harrisburg and beyond was pretty standard. We arrived back in around 1:30 AM (that is, 0130EDT Wednesday 9/4). And so that concludes Dragon*Con 2013. A pretty delightful adventure filled with working robots and now-most-definitely-working vans.

Well, okay, I did have to rebuild my A/C blower motor again, in the Georgia Tech parking lot. Remember those brushes I installed? They were backwards, and they ate through the copper bus wire after a few thousand miles. A random 200W scooter motor turned out to have the exact same size brushes, and saved the day.

Maker Panel 2013

Here’s where I (finally) post the presentation from the 2013 Maker Resources panel, and some related links, in one place! The panel happened on Friday evening at 7PM, and I had a pretty full house for most of it. Unfortunately I once again neglected to bring my video camera to the event, but I did notice quite a few folks taking video. If you have some high quality video of the panel, I’d like to include it here.

The panel was broader in scope than just “where to buy stuff” which I did in 2012. It put more emphasis on CAD software and transferring designs to parts using digital fabrication techniques (waterjets, lasers, etc.), and in general how to design better things. I tried to include some CAD program demos of stuff like Sketchup, freeCAD, and Solidworks/Inventor, but I actually ran so far over time that the director had to step in and cut me off (Sorry Val!). Maybe next year.

Also included as part of side discussion were the slides from last year with general parts & resources.

Here’s the list of stuff I said I’d put up like two weeks ago:

The Dragon*Con 2013 Complete Roundup, Part I: Operation GIVE ME A BRAKE and A New Surprise Antweight!

Sep 08, 2013 in Bots, colsonbot, Events, mikuvan, Pad Thai Doodle Ninja, Twelve O'Clocker, Überclocker ADVANCE

I’m back.

Somehow, and not broken down in western Maryland or something. The past week has been so chock full of adventures that I didn’t even have time to post it day by day like I originally wanted to. The Dragon*Con party got back into town at 1:30AM Tuesday, and now that I’m done unpacking everything and catching up to the last week of shop shenanigans, it’s time to spew it all out before I forget. This post is going to be the length of a small novel and will have 4 official subdivisons with this being the first half. If I start dividing something up at the start, then you know it’s gonna be bad. High energy food supplies and plenty of water are recommended.

A flurry of things happened in the week surrounding 12 O’Clocker construction. Besides working on the bot, I was also racing to make sure Space Battleship Mikuvan could make it 2500+ miles without breaking down or being patently unsafe outside of reason (with me, just the qualifier “unsafe” is insufficient). And on top of all that, I was designing on-and-off an entire new bot.

Here are the four parts. The first two are in this post, the second will be going live later and the two bottom links will be updated accordingly.

  1. Operation GIVE ME A BRAKE: Brake system and inspection all-around on Mikuvan!
  2. Pad Thai Doodle Ninja, an Antweight 4-bar pushybot I designed and built in like 72 hours!
  3. The trip down, the con, and how the bots did at the event!
  4. The links and documents associated with my two panels at  Dragon*Con.

 Operation: GIVE ME A BRAKE

In continuing the tradition of naming major van work after very bad puns, the brake system inspection has been designated GIVE ME A BRAKE. I’ve known for a while that the brakes on this thing were “functionally obsolete” – meaning, nothing bad was happening, and it could definitely stop every time, but it took more effort than any other brake-booster equipped vehicle that I’ve driven and the pedal was on the soft side. For bumming at rather low speeds around the city collecting its own parts, I had no reservations. But before a 2500 mile road trip where the option of breaking down is not available, I decided to at least give the system a visual once-over, and replace some of the major components. At the very least, even if it cannot go I should still be able to stop.

It helps that months prior I had picked up the majority of a new brake system on Rock Auto on some serious discount. New rotors and drums were had for basically $10 apiece, and I also bought new shoes, pads, shims, springs and hardware, and other goodies all on clearance. I’m hoping this doesn’t mean I’ll never be able to get parts again, but for the next few myriad miles it should be all set.

Because I’ve already been surprised multiple times by the severity of mechanical degradation, I also bought a bleeder vacuum pump kit and like a gallon of brake fluid. So this was going to happen eventually anyway, and I took the impending Dragon*Con trip as an excuse to use some of these parts and tools for which I was beginning to feel a bit of buyer’s remorse.

The plan was to work from the rear and move forwards. I’d already gotten visuals on the front disk system in Operation: LOST BEARINGS, and they were serviceable, albeit heavily scored. The rear drum? Never looked at them. All I know about drum brakes are that they are this carefully balanced arrangement of springs and punched metal levers and this weird ratcheting thing that will explode if you touch them, or so everyone warns me.

I spent a while on the Internets watching videos of drum brake repair, and I keep wondering to myself who ever thought this was a good idea. Like, I’d have figured cable-and-cam actuated disk brakes (like almost all scooter and bike brakes) would have been way easier a solution at the beginning of it all.

Anyways, let’s begin. One night I decided to just dive right into it and started by removing the rear wheels.

With my trusty Harbor Freight impact driver (this whole thing is basically a Harbor Freight ad, by the way), I removed the lugs which have clearly been impact-gunned on like you’re totally not supposed to but everyone does anyway. Mikuvan is RWD, so when the wheel comes off the drums are kind of loose on the wheel studs already.

Or they’re supposed to be. I guess years of cyclic fretting causes these things to become stuck together. Someone’s helpfully smeared a layer of antiseize grease onto the wheel contact surface already.

The drum has a M8 tapped hole in it specifically for you to insert a bolt and use it to jack the drum away from the hub.

So here it is. This is the thing. Now what??

When I tapped the drum off, a small mountain of brake dust fell out (the piles on the ground to the right). There were more cakes of it in the crevices by the dust shield, and way more behind the axle hub. After an extensive cleaning and soaking with brake cleaner, the above pictured setup emerges. Before, it was all sort of this even black color. I’m sorry, Earth.

As dirty as it might have been, everything was remarkably new and in good condition. This suggests to me that the drums were serviced (relatively) recently, and rear brakes tend to wear far less than front ones. The lining thickness was almost original – maybe less than half a millimeter thinner than the brand new brake shoe linings.

I played around with this mechanism for a while and got to see finally how the parking brake links up to the shoes, and most importantly how the damned self-adjuster barrel works. Self adjusting brakes are one of those automotive things that I sort of hand-wave and accept that they work and exist, and to not try and figure it out. The other items on that list include manual transmission synchromeshes (“some kind of coney thing bashing into another coney thing and it all works”) and all automatic transmissions (“insert analog hydraulic computer, get different speeds”)

I determined at this point that the rears most likely do not need any parts replaced, if the work was done symmetrically.

Well, was it? I ran around to the other side to see:

This drum took quite a bit more effort. I did eventually get it unstuck with a large gear puller, but not before I thought that maybe some pressure was still remaining in the lines, so why not try and bleed the system to relieve it and see if that would get the drum off?

(Spoiler: The rear right shoes seemed to be adjusted out more than the left, so it was grabbing onto the small wear lip inside the brake drum. The puller just sort of munged everything over that lip.)

Harbor Freight, I’m counting on you to save the day. More scarier words have never been said.

This thing attaches to the bleeder valve and allows you to pull a vacuum before opening the valve, so nobody has to be at the brake pedal to pump it in time with your opening and closing. Create a vacuum in the canister, open the valve, a small amount of fluid (or air bubbles) is extracted, and close the valve before the pressure approaches ambient again.

I’ve noticed that this van is great at 3 things:  raining bearings at me, dropping little flakes of rust everywhere, and emitting brown and black mucus when I least expect it. I knew that brake fluid degrades after a while, but eww. Armed with a jug of new brake fluid, I decided to perform a full rear system flush (the fronts would wait until I have them apart). Out come the Gatorade bottles…

The bottle on the left doesn’t really capture the blackness of what came out for the first few minutes, since it’s diluted out with some newer stuff. I used the rear right wheel’s bleeder valve, which is the furthest point in the circuit, so both rears were cycles. Check out those deposits in the right bottle…

Anyways, here’s the right side assembly after some cleaning. Looks identical to the left one, so I decided to put everything back together. Since I messed with the adjuster on the left side, I decided to rough-adjust both sides using the brake drum as a guide (“Just a little drag”) and let the self adjusters handle it in the parking lot later.

The next day was dedicated to the fronts. I’d already removed the front hubs and calipers before to replace the front axle bearings, but had not tried removing the caliper slide pin or dismantled the caliper in any other way.

I spent the better part of half an hour trying to get the slide pin loose to swing the caliper to the shown position. Why? Because some fucker who serviced this before definitely impact-gunned it on. With a MUCH bigger impact gun. It took me 10 seconds of straight impact wrench bashing to get the damn thing off.

Blame it on weaksauce Harbor Freight wrench or whatever, but stop impact gunning my shit.

After removing the caliper body, the rest of the steps were fairly intuitive.

And back on. The C-clamp shown was to reset the piston to clear the thicker pads.

At this point, I could remove the caliper as a whole in order to take the front hub and disk off.

Here’s the left front hub removed, showing the nice and scored rotor with a giant ugly wear lip on it.

The disks are bolted onto the hubs, and I removed them by clamping the disks in a vise and impact gunning the bolts out. These used discrete nuts – the hub wasn’t threaded or something, so it was an adventure trying to apply back-torque with a breaker bar to some very corroded nut threads. Was it too hard to thread one of these things, guys?

All new disk mounted and torqued not with an impact gun. I cleaned out the grease cavity and bearing races completely because cleaning the hub caused a ton of grime to fall into the bearings, so they had to be cleaned out and repacked.

Front left wheel buttoned up. Now that I have a vague idea of what I was doing, the right side went much more smoothly.

This time I was a little smarter and made myself a shop rag seal for both sides.

This is the scene at the height of entropy, when I had all the doors open and all my tools out. I was convinced someone was just going to come by and steal everything while I was working inside.

But they’d be stealing Harbor Freight tools – so am I really worse off, or them better off?

Time to complete the system flush. Hey, did you know I had front air brakes? I didn’t know either!  The first thing that happened when I opened the valve was a small riot of air bubbles. That would explain the soft pedal for sure.

(I guess it’s more “air over hydraulic”, eh?)

The total amount of brakerade generated. It’s interesting to see the different shades between rear and front. The next day, I took this to the local auto recyclers for disposal, where they presumably lit it on fire in the back or something. By this hour, all the traffic in the area had totally cleared out, so I took “wearing in the pads” as an excuse to take the longest, most convoluted possible way back to home, starting with gentle low speed stopping and progressing into trying to see how fast I could stop before a red light while not locking up or doing a stoppie. Brake responsiveness and pedal stiffness were greatly improved by the work, which I suppose was the goal.

Continuing on the trend of extracting brown mucus from various places, I decided to change the differential oil since it’s probably another one of those things which was last serviced 153,000 miles ago. This process was relatively painless – untighten the drain plug, unscrew with your hand, then feel the viscous brown goo envelope your hand as you wondered when you went wrong in life and became a van mechanic.

The smell was horrid. Old gear oil additives seem to decompose into various phosphate and sulfide components over time and it was actually like 20,000 eggy burrito farts at the same time. I refilled the diff with some Mobil synthetic 75 weight gear oil. I’m actually not sure if this entire rear solid axle is oil-flooded or not, but it takes like 2 liters of the stuff and the bulb volume under the fill hole is not that large.

While I had my waste oil bucket out, I also changed the engine oil completely and installed a new filter.

Look closely at the picture of utter chaos a few lines back and you’ll notice I have little devil horns up front. They’re a set of these things that I turned into an adjustable roof rack using some spare 80/20. There was a point a month ago or so when I was extremely concerned about cargo space – when we possibly had like 5 robots and up to 3 large props travelling down, so I took some recommendations for roof racks. These little things seem to be convenient if you don’t want to drill and rivet into bodywork, and so long as I have a 10 foot long rain gutter on the sides, it can be slid anywhere.  I can bolt entire Chibikarts to the roof now. This might get exciting.

So, that’s the state of the van on last Monday night before our scheduled Tuesday night departure. It ended up that said large props and numerous large robots weren’t happening, so this is decor for the trip, but will surely come in handy some day.

Working roughly in parallel with this was the design and (mostly) fabrication of an entirely new bot.

 Pad Thai Doodle Ninja

I some times take interest in how people name their projects and builds. For myself, I began it all by building Test Bot which literally was a test bot to see if I could put together parts in a meaningful fashion, and the name just stuck. I tend to be very direct with names – for vehicle type projects at least, it’s usually [noun][thing] or [adjective, usually a size or qualifier][thing]. Melonscooter, Kitmotter, Johnscooter, Tinycopter, Chibikart… even Mikuvan.  it’s a naming method which I see as sort of idiosyncratic of my stuff, and which also spread to some of my former students or MITERS peers.

It’s harder to call for other things. It’s easy to see where LOLrioKart came from (if you’ve been living under a rock since 2009, it’s like Mariokart), but not so much Überclocker. I myself have even forgotten where I got the idea to take overclocker and turn it Über, and 12 O’Clocker was a jocular offshoot of that since it was a 12 pound bot. So I guess I name things by “least resistance” – I’ve never spent hours or days thinking of a name for a project. Nor do I do that for products: RageBridge was originally “Ragetroller” because I was enraged by the lack of good motor controllers in the robot universe, and DeWut!? was only a short step from DeWalt, whose drill motors I unashamedly press into duty doing things their engineers would have never suspected.

So of course what I’m saying is, I have no clue how the hell the name for this bot came along except for this image:

Look at the very bottom left.

This modern art example came about because somebody brought a bag of Internet-themed word magnets into the shop, and shenanigans ensued on the local Rancid Dragon (a greasy spoon Asian takeout place) restaurant menu. Pad Thai Doodle Ninja just had a good floooooooow to it. This bot was named before I ever started the CAD, which is rare.

So what is Pad Thai Doodle Ninja? I started itching for a new antweight right after finishing 12 O’Clocker the week prior. I could have re-entered Pop Quiz  from 2011 with a new, one-piece 3D printed frame, but that thing had a tendency to take off without warning (protip: long blades on horizontal bar bots are awesome but impractical). At the same time, in conjunction with my sentiments expressed in the original 12 O’Clocker intro post, I did want the return of Test Bot in some way. I miss driving a bot that’s 100% drivetrain, or mostly drivetrain with a single degree of freedom weapon. Not since I built Überclocker in 2008 has this been the case with one of my entries.

So why not make a tiny Test Bot?

It would come together quickly, once again being a 3D printed frame, and would only use parts on-hand and from McMaster (which is basically next day turnaround). I sort of rushed into designing this, so there are no early CAD pictures. Here were the goals:

  • Four wheel drive using two motors, some 20:1 Fingertech Sparks I had on hand, rear motor in a fashion similar to Test Bot 4.5.
  • Servo actuated 4-bar lifter using unmodified servos so the stick position is arm position (using some HK939MG mini servos I had already from the thrust-vectoring deathcopter project)
  • Sloped front with embedded lifter, possibly a short hinged wedge. Armor to be made with 0.015″ spring steel shim stock overlaid on the 3D printed frame
  • Able to self-right.

This last one is kind of tricky with 4-bar lifters. You really have to take into account the center of gravity of the bot, and the length and extension of the arm, in order to facilitate this. Generally, 4-bar lifter bots flop onto their backs and come to rest on the arm whenever it is then deployed, as the CG is too far forward, and no self-righting is possible. Check out this classic video of former Battlebots heavyweight Biohazard to see how a 4-bar could self right.

Notice how its center of gravity is far enough back that the bot hinges on its rear edge and does not come to rest on the arm. The arm’s retraction then keeps the CG within the line drawn between the arm’s contact point and the bot’s rear edge, and it gathers enough momentum to push back over. Making the bot able to do this meant making the arm extend all the way back across the bot. Notice also how Biohazard had a ‘tang’ at the very back of the arm, a part that sticks up – this aids in the maneuver by making the contact point with the ground further forward, so the ‘line’ is longer.

This goal meant that I was continually watching the bot’s center of gravity in autodesk Inventor, and also continually modifying the linkage to suit. The arm had to have a certain amount of extension to make sure the CG was in the right place, and that extension had to jive with everything else’s placement. Here’s an example of a 2D sketch linkage I used (many times, with different lengths) to check the arm geometry:

Notice the nonplanar attachment points for the arm – meaning, the pivots aren’t all on flat lines with each other. So the virtual arm (the top link) actually doesn’t sit flat whereas the real arm takes the mounting point shift into account and does.

Making little sketch linkages in CAD programs is one of those things which distinguishes a geometric modeler from a parametric modeler. The former just treats your lines as a drawing, and if you move an endpoint or something the line length and orientation changes, with no effect on other neighboring elements. In a parametric modeler, you can add things such as dimensions (exact lengths, regardless of orientation), and geometric constraints (this line must always be perpendicular to that one, or this point must lie on that line, etc.) and these constraints are dynamically solved as you force the elements to move.

This is the frame of the bot about 1/3rd through design. I modeled the basic proportions after Test Bot, but shifted the rear motors out such that the wheels could touch the ground if the bot were tilted up. This necessitated mounting the motor much differently than in Pop Quiz (2 piece top-down clamp mount) or in most of my other bots (face mount) – the motor mounts are actually C shaped and slide in from the back.

Also modeled in this early picture are the two metal gear miniservos and the battery, a 3S 460mAh lithium polymer pack left over from one of the copters. The choice of wheels was going to be my insectweight default: O-rings stretched around a custom 3D printed rim. The outer set of rings will double as power transmission to the front wheels. O-ring drives are pretty popular in these smaller weight classes, but as I learned early on, there’s a catch – O-rings have to be stretched over their wheels, or else they’ll just roll sideways right off! Typically the stretch is 25% or more. The same is true for O-rings used as drive belts.

About 50% done, and a few hours in. I’ve kept the center of gravity marker turned on (the yellow ball) to check that at all points in the arm retraction, it lies between the arm’s contact point (just barely behind it) and the bot’s upper rear edge. I’ve also now put in the mounts for the servos – a top down clamp.

A drastic change from the previous snapshot to now is the addition of solid wedges. I’ve historically not been a fan of solid wedges, but I think hinged wedges would have been too fragile in an antweight when faced with modern weaponry. It would also let me use a very thick section of 3D printed ABS, which would increase the strength of the frame. At this point, I was also extremely underweight, so the thicker the better, right?

The 0.015″ spring steel shim will be inset into the side wedges and front, and be retained by infinite #4 self-tapping screws. Attachment of armor to the substrate is just as critical to its effectiveness as what material you use. If an extra hard steel with good backing is used, weaponry will tend to glance off and not catch and rip the material.

Spring steel bits added. This arrangement of top armor leaves the servo and drive motors serviceable without removal. The front armor slopes down further than the bottom of the frame to complete the front wedge.

In retrospect, it would have been better to leave the front armor also stopping at the bottom of the frame, so there’s only one point of contact with a potential opponent – the lifter. During the event, any bending of the front armor caused the bot traction problems.

View from the front. One thing that is missing from this image, but made it into the final “production” arm, is a little tang in the back of the main arm link similar to Biohazard’s. The “ears” are both for adorabu and as a front stop to prevent bots from just driving right over the top, since this bot is so short (about 0.9″).

Sunday before the departure, construction began on Pad Thai Doodle Ninja by waterjet cutting the steel armor and aluminum arm parts. I also started the build of the one-piece frame on a Dimension 3D printer. Pop Quiz was originally slated for such a one-shot print, too, but I elected to use Make-a-Bot (when it was still a thing) to keep the resources ‘local’ so to speak.

Tossed in with the build were the auxiliary components including servo and motor mounts, and the little o-ring wheels.

I thought I had a set of 10:1 Silver Spark motors, but it turns out I either gave them to someone without thinking (This happens more often than it should…) or never had them in the first place. Instead, these 20:1 Gold Spark motors will have to do. It means my top speed is only going to be about 3 feet a second, which is quite slow for my tastes.

The o-ring wheels have the D profile already in their bores, but also have a cross “drilled” hole that I’ll tap for a 4-40 set screw regardless. In Colsonbot, I had trouble with the D bores stripping in the soft plastic.

The waterjet-cut pieces were out of 1/8″ aluminum for the arms, and my 0.015″ spring-temper steel shim stock for the armor.

I heated up the spring steel shim with a torch while it was in a vise in order to make these bends. The area of bend will be weaker than the rest of the steel, but I tried to keep the heat local as much as possible.

The holes are sized such that they’re just about .01″ too small for a #4 countersunk screw to pass through. This ensures that I have a reasonably flat surface up front, but is much stronger than if I had actually countersunk the screws fully. As will be seen, the screws stick up just a little bit.

One thing I forgot to do was mirror the last set of outside holes to the right side. Whoops…

There will be 3 standoffs between the inner and outer frame in those hole positions so I can mount the rubber O-ring drive without having to cut it every time. To make these new holes, I had to turn a 0.2″ peg that stuffed into my 0.2″ counterbored hole in one of the positions, use that to establish a coordinate system, then countersink the rest (though with 0.25″ cutters). The servo mount backs up the plastic material from sinking down due to cutting pressure, and the elaborate clamping prevents the plastic from fluttering.

This was the status of the bot before we left on Tuesday night. I was going to wait until we got to the Invention Studio and set up a forward operations base of some sort.

Bright and early on Thursday at the Studio. I packed Colsonbot and the semi-retired Pop Quiz; Colsonbot was actually going to be entered, but Pop Quiz was only along as spare parts if needed. On deck were machining some arm standoffs, modifying the lift servos, and then wiring the whole thing up.

Normally, I’d use some custom-machined spacers in these kind of applications, but the GT machine wasn’t very well suited to producing small stuff. It’s large in swing, gearheaded (and noisy), and the tooling was not in the best condition. So, to speed-finish the bot, it’s time to resort to plastic washers! This wasn’t as bad as I make it out to be, mostly because plastic does have some ‘give’ so I could tune the friction and slop of the joint using a threadlock-glued pivot screw.

The front link attaches directly to the servo output arm. I was preparing to run 2 servo lift on this bot in order to get more force – with 2 servos, the calculated max lift force when the arm is fully retracted (therefore in the worst mechanical advantage position) was 1 pound. So in other words, it can dead-lift an entire 1lber from the lowest position. Now, typically, when an opponent is lifted an edge, you’re lifting somewhere around 50% of the weight.

As I found out, these servos aren’t very well matched in how they handle the same range of PWM pulses. In fact, one servo traveled about 10% more than the other, while Y-connected to the same radio channel. This meant that the servos fought each other when the arm was at either extreme of extension. Digital servos would be far better matched.

In making the 2-servo version, I also had to “mechanically reverse” one of the servos since they faced each other across a mirror plane. Normally, Y’ing each servo to the same radio channel meant they traveled in the same direction while looking at their own outputs. But I needed them to travel in the same direction in a global reference frame, so one servo had both its 3-lead potentiometer feedback reverse, and the motor wires reversed.

Doing only one of the above would make the servo run straight into one end stop and smoke itself.

At this point, the bot was about 0.9 pounds, so I could as be as liberal with giant wires and solder blobs as I wanted.

Still with two servos, and getting through the wiring now. The black amorphous blob at the top is a small 3A switching regulator that gives 5V straight to the servos. I wasn’t about to try and hitch the servos directly onto 11.1v volts, because they would just grenade almost instantly.

The bot is mechanically together at this point. Notice the standoffs in the center between the frame rails that attach the outer wedge ‘flaps’ to the main body. If this thing were actually one piece, I’d have no way to actually mount and dismount the O-ring belt besides cutting it each time.

Completed bot on the googly-eye scale at 0.88 pounds. The extra amount down from 0.9 is presumably made up of wiring that I trimmed short or something, because I definitely added more screws…

Drive testing of this thing caused it to burn up and strip one servo, mostly due to them fighting themselves with the arm fully down. Going to one servo would have meant losing the ‘dead lift’ margin, but getting into a situation where the bot had to dead-lift an opponent seemed far less likely than a normal edge lift.

The left side servo was gutted, leaving only the output gear to act as a bearing.

The bot was a full 0.12 pound (or about 2 ounces) short at this point, and it was failing to self-right because the CG wasn’t far back enough. It would some times get in the right position with a forceful actuation of the arm, but with one servo a forceful thrust was out of the question. So I bought some fishing weights and melted them down, an ounce apiece, to append to the rear of the bot on top of the motor mounts.

Here’s the “before” shot, the pretty clean bot (no weights have been added yet).

And with the 2 extra ounces in the rear, the bot could self right every single time!

I handed PTDN off to Cynthia to drive for this Microbattles tournament. The event report for both big and little bots, and match videos, will happen in the next half of the post.