cold arbor

First, I would like to say that I finished Ninjabridge.

It looks like this:

Yup. Back to a relay.

Ninjabridge worked briefly after extensive noise-reduction and ground loop prevention surgery. Sadly enough, it suffered a gate drive failure and subsequent Epic Shoot-Through at almost full saw speed. Nothing was particularly happy.

And so with the sun rising yet again, I pitched together this 12v SPDT relay assembly. It’s triggered by the previously mentioned R/C switch.

At least the saw works. Some more drive testing confirmed that my fears about the saw’s startup and running current pulling down the entire system were unfounded. Here’s a video of Arbor nibbling on some wood.

And a “pre-event” picture (not that D*C is a destructive enough event to warrant it, but hey.)

Überclocker

After putting all the screws on Arbor, I turned my attention back to Clocker to address one last detail that hasn’t proven fatal, but isn’t very healthy to ignore.

The bot’s drive chains have been getting increasingly looser as matches passed. The left side, in fact, has become so loose that the chain hits the ground on the bottom side of the frame. This is just begging to get snagged on something, or to make the chain walk right off the sprocket.

I’ve been meaning to put a chain tensioner on the drive since I built the bot, but never got around to it until now. The tensioner is just some simple bits of milled Delrin that has holes for perpendicularly tapped screws. I freehanded the vertical holes with a cordless drill, which brought back memories of before I was saved from a life of meager tools and hand fabrication. It was a heartwarming moment.

With the tensioners, the drive is substantially quieter. I would also venture as far as to say the bot is a little more responsive, too, since before the tensioners, the front wheels could spin 30 or more degrees before engaging.

If the chains ever get looser (Robot Jesus forbid) the Delrin sections can be milled more to compensate.

So now it’s time for a Clocker photo – I cheated a bit here, and actually took the picture before adding the tensioners.

And an everyone shot:

boxxy

No, not that boxxy.

This year, I’m going to be shipping down the bots ahead of time – which really explains why I’m working on them now and not, say, next weekend. Last year, taking Überclocker and support equipment as baggage cost me a cool $90 or so for overweight, oversize, over-the-top baggage fees. For essentially the same price, courier services will ground-ship an excessively large “package” from here to Atlanta in about 3 to 4 days.

Now, I’m defining “package” as “giant 2-foot wooden cube weighing 135 pounds and loaded with two (and a tenth) deathbots”, which might be stretching the definition some. But here’s the wooden box.

It’s made of some cheap Home Depot plywood (the same plywood, in fact, that Arbor was nibbling on. That panel became the bottom.

This time, I have enough overhead such that I’m actually bringing SPARE PARTS.

The bots go out in several hours and will hopefully arrive Thursday…

Something that very few people (myself included) have seen is the inside of NK’s weapon motor. About the time I built it in 2008, my camera decided to consume itself. So all I had from that time were grainy cell phone pictures because I’m compulsed to post build reports, but those pictures didn’t really show anything worthwhile.

NK’s motor was the third hub motor that I’ve ever built, period (after the original RazEr motor and the second iteration). It is also hands-down the most cleanest wound and carefully terminated motor I’ve built. This was back when I actually had patience for making motors. All the winding layers are clean and the termination is perfectly symmetric like a LRK should be.

After this, it all went to hell because I just stopped caring about how neat my motors looked… or even how concentric and wobble-free the cases were because it was fine as long as it could MOVE, dammit.

In International Crazy R/C Airplane Guy Notation, this motor is a 5205-14D. 52mm diamter stator, 5mm stack, and wound 14 turns per tooth in Delta termination.

I bought replacement magnets from Superdupermagnetgeorge to fill back in the 25% or so of the rotor that had become detached. The original magnets appeared to have been retained solely by superglue.

That’s kind of not legit at all.

In recent days, MITERS was given several large jugs of epoxy and hardener. While cleaning out a back shelf for the new EPOXY section, I found alot more adhesive accessories from years ago. Of most immediate interest was several cans of epoxy filler in different flavors in types. There was a can of West System 403 fiberglass-based filler, a bucket of phenolic microspheres, and wood flour.

I decided to do something that every other custom motor builder seems to do – fill in all the gaps and seams in the magnet ring with some hybrid epoxy. Adding filler gives the glue volume and more bonding area to the magnets. The fiberglass-based filler came out rough and lumpy, so I tried mixing up a cup of phenolic microballoon epoxy. It came out looking sort of like epoxy-flavored Nutella.

Now those magnets shouldn’t be going ANYWHERE.

weapon pod pivot

One of the gimpiest parts of NK5 is the weapon pod’s rear pivot. The disc is mounted on an assembly that can swing up and down, letting the bot drive inverted if necessary. The issue is that I made the last pivot in like 5 minutes. It was just a piece of sandpaper-cleaned Home Depot aluminum tubing and some roughly cut spacers. It flexed all over the place, and by the time D*C2008 was over, the tubing had crumpled from the impacts.

This was inexcusable. And so, in the middle of the night, I hopped on the lathe and just started making something. Above is the first 100% designed on the fly part I’ve made in a very long time. On one end, a snap ring groove. And on the other side, a 1/2″-28 thread machined so a thin panel nut can thread onto it. It basically functions as a very complicated but specialized bolt, holding the two halves of the bot together with some preload.

Originally I had intended to pick a random snap ring from the hardware bin, but a bit of digging around located me these weird e-clip-like things. A bit of research on McMaster showed me that they’re called “poodle rings”, presumably because of the big ears.

They had a much large diameter and thus potential contact area, so I remachined the groove slightly to fit them.

I also recut the UHMW spacers (using the same stick of UHMW) so they fit better and were also much large in diameter. The larger in diameter they are, the better they can resist side forces.

The old disc was warped from NK faceplanting into the steel arena bumper at full throttle. As a result, I dug out the spare disc I cut in 2008 and gave it the heat-to-orange-and-dump-in-oil treatment. It’s a crude method of heat treating, but it gives decent hardness for 4130 in bulk (don’t try this with a tube frame…) Afterwards, I reassembled the weapon motor and gave the teeth a touch up on the grinder.

With the important part of the robot done again, I begin refilling the internals. Pictured is the 1.3Ah Li battery I bought as a replacement for the old 2008 battery, now featuring a very dead cell. I actually got two because they’re too cheap for their own good.

And here’s the beauty shot:

While I had the lid open, I added a green LED next to the blue. Because funky colors are totally a priority.

NK handles just as well as I remember it from 2008. The right side drive motor is making some weird noises, but it doesn’t skip or feel crunchy. Regardless, I should probably get some replacement motors and have them dropped in Atlanta for next week.

Total robots finished: 2.999999999996842178 / 3

In 2008, I had a Pre-Dragon*Con Botgasm. Last year, with only Überclocker, I didn’t have enough robots on deck to be finished in order to properly botgasm. Therefore, this year, I’m going to have to make up for it with now three bots that need completion!

Well, let me interrupt myself before I even start: Überclocker is done. I closed the bot up (well, minus battery cover, which I physically lost some time in the past 6 months) this afternoon and have been driving it around relentlessly trying to uncover hidden driveline mechanical flaws that could come and bite me in two weeks.  With Clocker asymptotically functional, I set it back up on the shelf and am now turning my attention to Cold Arbor…and a a revival of the Nuclear Kitten.

Überclocker

Two days ago, I left the FrankenWalt gearboxes about 95% finished. I made both gear cases, both sets of ring gears, both motor mounting plates, even both output stub-shafts… but only one output spindle. I just didn’t feel like machining the teeth off another gear that night.

But I returned later, having re-educated myself on the importance of finishing robots, and attacked that last remaining part.

Now here’s the reassembled drive base of the robot. I essentially took apart the entire outer metal structure, cleaned everything, then put it back together with the motors in place. Significant amounts of dirt, arena grunge, and metal chunks and flakes (!) made it into the corners of the robot, so as long as I had it in the open, I might as well clean it all out.

The outer chains have experienced some pretty serious stretching, and I expect that I’lll need to make a tensioner for them soon, lest they snag on something.

A couple more screw later, and the fork structure is remounted. While I had the fork apart, I took the time to make a few minor tune-ups and adjustments; mostly line items on the laundry list of upgrades that I keep intending to do (since they would technically take little time), but never get off my ass to do so. Such as:

…grinding the tips off the fork shaft set screws. These were formerly normal cup-pointed set screws, but I was dissatisfied with the way the cup point was gouging and digging into the flat on the (relatively) soft aluminum lifter shaft.

One way to resolve this is to just make a more legitimate power transmission medium, such as a keyed hub. But we can’t have that, since I’m lazy and therefore always vigilant for hackarounds. To obtain a wider contact surface with the aluminum shaft, I ground the tips off. Now, the contact circle is much closer to the 1/2″ screw diameter.

It won’t prevent gouging, but it should increase the shock torque handling ability of the fork a little more.

I kept the electronic bays intact, so dropping the Victors back in was a quick job. Since most of the wiring was on connectors, I didn’t have to rewire much from scratch.

Bonus: There is something very, very bad in the above picture. First one to name it wins….

… something. For what it’s worth, I fixed it.

A quick power-on confirms that the system is still functional.

Well, functional to the degree that I somehow managed to solder both drive motors in backwards.

Oh yeah – also on the list of stupid hacks I never get to is rearranging the actuator layout of the robot. Historically, Clocker has ran with the clamp actuator slung under the clamp arm itself. This location protected the motor itself from direct impact from opponents and also made the wiring path simple.

However, it severely constrained how far up the clamp could move, because the way the linkage is set up, the motor would just back itself into the aluminum fork hubs. This essentially limited Clocker to gripping opponents less than 8 inches tall.

I’ve toyed with the idea of flipping the actuator around so the motor is mounted above the clamp. This arrangement gains the bot another 2 or 3 inches of “grip” and also helps the leadscrew clear the truss that forms the forward portion of the clamp arm, which means the clamp can close to just over 1″ gap.

The only downside is that the motor is now open to damage. I’ll make an aluminum plate cover for it or something, but I think I’ll keep this setup.

All of this said and done, here’s some test driving video of Clocker, chasing Twitch, Jr. Everything goes well until the robots collide head on.

Hint: The robot that weighs three times as much and is essentially an uparmored Humvee in terms of structural durability fared better. Sorry Twitch :<

However, test driving revealed a critical flaw in the right side FrankenWalt – the first one I made. When I hard reverse planted Clocker into a corner, the right side completely lost coupling. I was completely unsure of what it could be, since the whole thing was made of Beast Fits and Loctite. As it turned out, the second stage ring gear’s press fit was in fact not a press fit at all. I probably only thought it was because I was pushing through burrs. The gear was actually pretty free to spin inside the gearcase. Solution: Drill down into the ring gear through the aluminum case just deep enough to insert a dowel pin. I used a #14  drill at 0.182″ diameter to make a gouge for a 3/16″ pin.

And by pin I mean lathe tool stock. Hey, it’s hardened steel and polished. Give me a break.

(The pin was cut flush with the gearbox surface and ground smooth, just for the record.)

It’s good that I found this out now and not, say, Monday morning of the con.

Overall, that does it for Clocker. I still need to cut out a replacement battery cover, since it being a nondescript cut-up-looking chunk of black plastic, it probably fell on the floor and got tossed during a shop sweep. At this point, Überclocker weighs 27 pounds – more than it did originally, but not surprising after the addition of the much bigger drive motors.

I’ll actually be making the replacement battery cover out of some very thick steel just to use up the last 3 pounds and push the robot’s CG back another millimeter.

cold arbor

Arbor has reached its own apex of entropy – after this point, I should be putting the robot back together more than taking it apart. Hopefully – I still haven’t addressed the drive motor issue yet. I kind of don’t want to make another two FrankenWalts, but I doubt I’ll be able to use the 24:1 gearboxes any more.

The designed parts of yesterweek have materialized into 1/4″ and 1/8″ aluminum plate. I managed to find a good deal on 2024 aluminum panels on eBay several weeks ago, and the 1/4″ parts here are made of that plate. Featured above are the new claws, the new saw motor mount, and new actuator mounting points for both front and rear actuators.

A little bit of sanding later and the rear actuator mount is in place. This is a very visible use of “thickness buffers” in the art and science of T-nutting. The original 1/4″ aluminum struts were 1.75″ apart, but the saw actuator is 2 inches. So between the back of the bot and the saw actuator, the spacing needed to widen up an eighth inch on each side and still had to hold T-nuts at the back.

So the solution is to stack two 1/8″ plates: one part which is purely a T-nut anchor, and another which is identical in that regard but also has the actuator mounting points – and make sure it’s on the outside of the stack.

The mounting plate is bolted to the thickness buffer plate using a handful of 6-32 cap screws. I thought about riveting it, but I couldn’t find our rivet gun.

The actuator drops in place like so. The only thing changing on this part of the robot is the leadscrew, which I’ll remake using a longer piece of Acme rod stock.

electr(on)ic mayhem

One of the downsides of possibly running two robots in the same class is that they might have to fight eachother in the tournament. If this happens, you either have to make sure you’re awesome at dual-joystick driving two robots at the same time, or have two radio transmitters.

I don’t. I only have my (outdated and obsolete) Spektrum DX6 radio. The same type that I ran back in 2007, when DSM1 was still in style. I have multiple BR6000 receivers for the transmitter, but only one Tx, and I don’t intend to get more obsolete equipment.

So what do I do? A real Spektrum rig is going to cost me another $2-300, which I could swing, but it would be kind of a waste of money given that term is about to start.

Luckily, like every other problem I have, Hobbyking has a solution.

On the left is my Spektrum DX6 (not even the i version). On the right is the HK-T6A 2.4Ghz 6 channel radio.

It costs all of $25, and includes a receiver. However, it also comes with no displays whatsoever (it’s the most bare-ass radio I’ve ever seen with more than 4 channels), no onboard switches for calibratoin, and the worst, buggiest we-made-this-with-a-trial-version-of-VB6 calibration software ever. Oh, and you can technically only get 5 of 6 channels working at any one time if you enable V-tail (& elevon, Delta wing, etc.) mixing for single-stick robot driving.

What it does have, though, is an established userbase and numerous “upgrade” hacks and replacement calibration software, such as Digital Radio.

The most important thing, though is that IT WORKS. For $25, I can deal with some shortcomings and rough edges. I’m tempted to tell Horizon Hobbies to just fuck off, but I also understand that HK is playing with alot of home field advantages, and would still spring for a real Spektrum rig any day.

The bottom line is that Arbor is getting its own radio for the con and for future events. This receiver setup has been determined to output “Bot-safe” signals i.e. none at all when the radio link is lost, so Arbor ought to still pass every failsafing test there is.

For what it’s worth, here’s a slightly junky shot of the inside. The difference for me between Chinese equipment and “established” well known manufacturers is that I never feel bad tearing into the former without even using it beforehand. Usually, I know that at least some kind of engineering has gone into the latter, and that me picking at it is only going to make things worse. So I satiate my curiosity on cheap parts and equipment.

The main MCU in the radio is an Intel 8051 knockoff that appears to share the same instruction set and pinout. Otherwise, the radio module itself is a bit more sophisticated, and features a 2.4G Taiwanese transceiver (Amicom A7105) and some kind of custom ASIC from Flysky (FS8004, which I can’t find a datasheet for anywhere).

My first mod to this radio is to make the left stick (throttle) spring-return to run the saw and clamp actuators. I didn’t have the correct part, but I chopped a spring lever out of a dead DX6 transmitter and sanded it down until it fit in the same slot. I also used the spring from the dead Tx.

There you have it – for $25, which is something like the cost of two burgers from Five Guys or how much Mountain Dew money I run through per week, you can get a 2.4Ghz 5.2387 channel radio that is essentially intereference-free, does not require channel crystal diggling, and has all the features you might need to control a basic robot. A word to robot n00bs: it did not use to be this easy. Get building.

nuclear kitten 5.1 surround sound edition

It’s back!

NK5 has been sitting idle on my robot shelf since Dragon*Con 2008 after it was first built. I’ve practically not looked at it, since I assumed it had taken significant damage at DC08 and was essentially not worth repairing.

After some egging by friends, I found out that I was pretty wrong.

Here’s the robot after I stripped everything down to prepare for rework. The overall appraisal:

• The two drive gearboxes I thought were destroyed are actually working fine. No stripping or weird noises
• The motor is functional, doesn’t have crunched bearings, or shorts in the windings. It just needs some magnets replaced.
• The weapon pod swingarm is pretty heavily damaged and will need rebuilding to a beefier specification.
• The 3S 1.3Ah lithium polymer battery is toast. D’oh.
• Why the hell did I use 12 gauge wire on a beetleweight?

I’ve ordered replacement magnets and two replacement lithium packs from Hobbyking. Hopefully, with the magic of express shipping, they will arrive next week. NK fundamentally needs maybe two or three hours of work to be back to competition-spec.

How long will it actually last? I have no clue. It’s built to barely 2008 spec, and the brushless masculinity contest has grown in magnitude sine then by far. But, expect NK5.1 at Robot Microbattles on Sunday.

It has begun.

While I seem to be in “build season” mode year-round, it is during long breaks with little in the way of academic or life obligations that I get the most done. Last summer, I began work on LOLrioKart and built Überclocker, Pop Quiz 2, and Nuclear Kitten for Dragon*Con.

… which sort of sucked horribly for everything. Except NK, but only by about *this* much.

So what’s coming down the projectubes this summer?

Mostly the same thing. D*C is my biggest bot-celebration of the year, so once again the combat robot fleet takes high priority. Since there’s really just one robot that needs rebuilding, I also have the usual pile of small electric vehicle projects, of which only one is actually urgent.

Übercløcker RЭmiχ

I started redesigning Uberclocker some time in the fall of last year, hoping to get it done by Motorama 2009. Of course, due to scheduling concerns and logistics, this didn’t happen. But what that presented me with was the chance to put it away and not look at it for several months.

This is pivotal. The basic design has already been hashed out, but now I get to return to it after not thinking about it for a while. I am now in the process of analyzing the 3d model for any “impossible objects” that I might have included, or Really Bad Ideas. Such design flaws plagued the real life Uberclocker 1.0 at D*C last year.

Planned upgrades from 1.0? Well, besides EVERYTHING, the primary focus is on drivetrain reliability, center of gravity, and the upper clamp arm.

As a member of the pushybot school of combat robotic thought, I value maneuverability and driving above jawesometacular weaponry. Uberclocker 1.0 had a strange serpentine timing belt setup that seemed like a really awesome idea at 5 in the morning, but… wasn’t.

The robot also suffered from “centrally located center of gravity” syndrome at the event. While a CoG near the geometric centroid of the robot is good in practically every other case, the fact that the bot’s sole purpose was to grab another opponent and lift it off the ground meant that it just sort of faceplanted every time I attempted a lift. Not a very impressive show. The redesign lengthened the wheelbase of the bot, and selective weight reduction moved the CoG back about 4 inches, without additional ballast.

Oh, that’s right, Uberclocker 1.0 weighed in at an incredible 22.5 pounds out of 30 at the event. I’ll fix that too.

What I didn’t really get to (properly, anyway) in the redesign was the upper clamp arm. The previous arm was both weak and structurally unsound. While I think I took care of the “unsound”, I still have my doubts as to the clamp mechanism’s effectiveness.  In the past, clampbots have used pneumatics to actuate the upper half of the clamp. This is advantageous because a pneumatic actuator requires no “holding power”, unlike an electric motor, which has to be continually powered to produce torque. Pneumatics also have a certain amount of spring-back ability that a solidly coupled electric actuator doesn’t.

But robot-heaven forbid that I make Überclocker even more complicated by incorporating a pneumatics system for the one actuator that might need it. Thus, I’m still partial to a (spring-coupled) leadscrew-type mechanism, over the current design candidate’s motor-on-a-weird-gear. Except this time it won’t be driven by a beetleweight motor.

I intend to keep the “Chinese puzzle” frame, and will be refining it for ease of assembly. I devoted a few weeks to just fabricating the frame parts last time – no, never again. That’s what computer-controlled machine tools are for.

Pop Quiz 2√2

Incidentally, 2√2 is about 3. Not quite there, which also describes this planned rebuild of Pop Quiz 2. It’s not quite a complete conceptual revision, but there will be significant upgrades all around.

PQ2 is one of the (if not the) flattest 1lb class robots around that has an active weapon. It hits lower than some undercutters. The problem is that going the extra 1/8″ down in this current design meant that I had to ditch practically all the well-known, battle-proven parts – Sanyo gearmotors, SPEKTRUM 2.4ghz receivers, etc.

It was a fun thought experiment come to life, but the robot had a horrific reliability record, almost no reception due to the FM ground-band receiver, and a 5 minute chopped hack of a master power switch that ended up disintegrating after exactly 1 hit at D*C 2008. Pop Quiz had about 15 seconds in the arena.

Not cool. For ’09, I am INCREASING the height of the bot. Me, making a robot taller. How many times does THAT happen?

The robot height will be increased to about .400″, enough to cram in a set of real Sanyo micro gearmotors. The rest of the robot’s electrical system is sound, and so is the weapon motor. I’ll most likely end up reusing the electronics anyway, minus the cheesy little FM park flyer receiver. Instead, it will be swapped out with the latest Spektrum DSM offering, and I will run one transmitter between all the robots.

There’s no current virtual model for PQ2.8284171, but just imagine the current bot 0.025″ thicker.

Nuclear Kitten 5.1 Digital Surround Sound Edition

I’m actually satisfied with the performance of one of my combat ‘bots for once. NK needs very minor rework to take another run at D*C. The weapon motor needs some magnet reglued, and the weapon pod pivot axle is slightly bent and needs to be made better anyway. Past that, I have a spare blade to replace the faceplant-into-steel-bumper bent blade.

The only point of concern with NK is the drivetrain. Despite having a mechanically isolated weapon, I’m still blowing drive gearboxes, just because the bot is that much more powerful. I might switch to something like the 50:1 Copal motors || redesign the motor mount || use softer wheels.

No frame changes are necessary, since the bot escaped D*C rather unscathed.

LOLrioKart

Since I discovered that the main battery pack was leaking voltage all over the place (somehow, through an eighth inch of rubber?), I stripped down the entire electrical system and tested all the batteries. It turns out that the steel casings of the cells are live, something which I’m fairly certain should never be the case. While it’s fairly common for the battery negative terminal to also be the casing, the errant voltages are always somewhere between 0 and 1 volts.

This case voltage doesn’t seem to have negatively affected the cells, but I’m fairly certain it’s the culprit behind stray frame voltages. Somehow.

The focus for LOLrioKart work will be the electrical system. I intend to complete and test the ginormoFET controller and possibly implement dynamic (or regenerative!) braking using the upper leg of the half-bridge. Mechanically, the kart is fine.

Well, except for the brakes, but they’ve always been undersized and insufficient.

Ultimately the goal is to run it for longer than 1 minute on all 54 volts, or the full pack voltage of whatever eventual power system I might come into. I’m heavily considering crating up LOLrioKart and shipping it down when Dragon*Con comes around, so I can drive it in the parade. This could possibly be the worst idea I have ever thought of.

Project RazEr

It’s been hanging on a utility hook since the last controller fire. Everything works and the batteries are still charged, so all I need is a BLDC motor controller. Since everything still technically “works”, I don’t intend to touch the scooter that much, if at all. Any work on it will be replacing the shell of the wheelmotor with something more substantial (and better engineered, and more reversably built).

Time to get crackin’.

About time, eh? This past summer, I continued my R&D position at the Media Lab while building three combat bots. Nuclear Kitten 5 and Pop Quiz 2 are updates to the insect fleet while Ãœberclocker is a completely new build, exploring new building techniques and technologies.

Sadly enough, PQ2 and Ãœberclocker fell victim to the age-old trap of trying too many new things and making too many changes at once, and not enough testing before deployment.

The final rundown after D*C 2008:

Ãœberclocker

What can I say? While Ãœberclocker looked awesome and had more pretty machined parts than I have ever put on any other bot before, performance was massively lacking. A number of factors contributed to this.

1. Lack of design revision and validation. Combined with 5AM Joltgineering, this led to a vast number of absurdisms in the design. Unserviceable parts, spotty attachments, poor placement, the works. Had I waited a while after completing the design, then ran through the entire process again, I probably would have altered quite a few things. The bot’s assembly was very much one-way. If I wanted to change a lifter motor, half of the thing has to come apart – and most of the electronics have to be unwired. To replace a drive wheel involved 3 sizes of allen wrenches and fiddling with multiple spacers. All of this made it a nightmare to service at the event.
2. 5am Jolt-gineeringâ„¢. It was summer. I had neither class obligations nor a very strict schedule. Much of this bot was designed in the early morning hours. Designs need a proper balance of neurotransmitters that are absent when you hard-reset your sleep cycle. This led to things which would normally be Really Bad Ideas suddenly seeming like optimal solutions.
3. Lack of testing again plagues my builds. I thought that an entire summer would be enough to get the bot done, but it came down to the last weekend before the event anyway. The bot was never quite fully operational either, with part failures causing the ultimate scrapping of the top clamping fork. Fortunately, tuning the lifting fork servo was rather straightforward, and it performed admirably. The drivetrain, however, was never run under battle conditions. The inadequacy of my serpentine belt setup revealed itself rather painfully at the event where I lost both drive sides due to slipping belts (Which subsequently took 15 minutes to reseat.

When all was said and done, Ãœberclocker won 1 match, not by its own merits, then lost the next two matches. At the end of my final match, one of the lifter fork motors went up in smoke from me trying to use the fork as a hammer. Compounded with the rest of the failures and the dysfunctional clamping fork, I forfeited the tournament.

All of Ãœberclocker’s matches except for one (due to a corrupted file system on the camcorder’s miniDVD media) are here.

Here’s some action shots of ÃœC at the tournament.

Ãœberclocker initiates a ninja lift on Scimitar. This was one of its only good shots – where it didn’t just fall over.

In another match with Scimitar, the two bots perched precariously on the edge. At this point, I had lost the entire drivetrain, so couldn’t quite back him off.

Ãœberclocker attempts to brute-force Poulan Rouge off the stage after failing at a lift

So, what actually worked?

• The concept is good. Ãœberclocker was one of the more popular bots at D*C this time around, mostly due to its unique design and strategy. It just needs a better execution. A more rearward center of gravity, stronger clamp fork, and more reliable drivetrain just to start.
• Ãœberghettofrakenb0xen performed spectacularly. The robot had no trouble dead lifting 30 pound opponents at a brisk speed. Ultimately it was rapid repeated reversal of the fork drive that caused a motor meltdown due to high current. The shaft clutch worked great in preventing gear explosion.
• Spring-loaded front legs weren’t able to perform up to their full potential because the rest of the bot sort of prevented them from actually having any effect. However, they did allow negotiation of the hazards without much issue in most cases. The front parts were too low and would some times get caught on the edges of the bars and ride on them. This can be solved by using a bigger front roller.
• It looks badass. What, don’t think so?

Ãœberclocker is a concept which I want to continue developing to bring it to maximum effectiveness. Design revisions include trying to fix all the problems indicated and making the strong points better. However, I have no targeted event date for the redesign, and it could be as late as Dragon Con 2009.

Pop Quiz 2

It’s the flattest active-weaponed antweight ever. Again, just like Ãœberclocker, the concept was great, but my lack of attention to detail ultimately tainted the execution. This build fixed one of the major shortcomings of the original Pop Quiz – a weak, unreliable weapon. This time, the blade was frighteningly fast, to the point that I never actually full-throttled it due to a fear of the bot just taking off.

The tradeoff was the unpredictable drivetrain. To stuff everything into a 3/8″ tall space, I had to build custom gear drives and modify the motors. While a stock solution such as Sanyo Micromotors do fit in the space, they were far more expensive than what I had already. The “frankenmotors” worked great in testing, but over extended operation, they began to gunk up. The square slot car motors themselves are already rather low quality and have widely varying no-load RPMs. This translated to different load characteristics. Throw in some manufacturing tolerances on my gear drives and I had a stochastic drivetrain.

To make matters even worse, I quite literally had no control over the bot’s direction due to the total lack of radio reception. If the weapon was running, then the bot would randomly interpret its own noise as signal and randomly drive around.  The GWS park flyer receivers have almost no filtering and seem to accept used toilet paper and old batteries as valid.

At the event, PQ had all of 1 match, lasting about 10 seconds. The single hit blew apart the momentary button switch that was the bot’s master power switch. In the battle royaly, PQ was able to land a few hits before pinging itselff off a wall and out of the arena.

All 20 seconds of Pop Quiz’s matches are here.

PQ wasn’t in the arena much at all, so I only got one picture of its work.

Pop Quiz goughes in the titanium plow of Segs, a rather innovative 8WD “flexible” bot. This same impact flipped PQ over and also destroyed the power switch.

Pop Quiz was a great trial in how flat I could build something, but returning to the previous chassis outline would benefit the practicality greatly. I can use real drive motors, have more space for batteries, and use a larger weapon motor. PQ1 had a strong drivetrain but weak weapon, and PQ2 had a strong weapon with a spotty drivetrain. It would be beneficial to combine the two traits, but like Ãœberclocker, there is no scheduled rebuild for Pop Quiz at the moment.

Nuclear Kitten 5

NK5 was a two-week speedbuild that only happened because I discovered the magic of waterjet-cutting 2D parts and assembling them like 3D puzzles. We’d been doing this in the lab for a while, but I never gave it a shot myself – that is, until Big Blue Saw ran a free part sale. It all started when I tried to stuff the redesigned frame onto a 9 x 9″ square of aluminum. While the complexity of the frame put it over the “freeness threshold”, I couldn’t resist but fab it anyway. The rest of the bot followed.

The best part about this bot was the new bladehub motor. Previously, NK used a friction drive between the blade and the weapon motor. This was spottily reliable and also required constant adjustment. With my experimentation in hub motors over the past year, I decided to build a high-speed fully self-contained disc motor just for driving the weapon. Backed by the power of lithium batteries, the spinup time to “vibradrive” was under 2 seconds. I also never hit full speed with this weapon because the bot would begin to move around the floor powered by its own vibrations.

The new disc was lighter in profile but heavier overall, being made of steel instead of titanium. The tips were heat treated to avoid blunting, and this worked well. In the Battle Royale, the disc warped at the nonhardened points after the bot faceplanted into the steel arena bumper rail at full speed. Better than just shattering, I suppose. After the second match, the disc motor threw a magnet and was dragging it across the stator for the rest of the tournament. This gave it massive starting issues, but after everything got up to speed, the weapon still worked.

The combination of NK4′s fast, balanced drivetrain and this version’s weapon meant that NK was a great performer. It fought four opponents to capture the D*C 2008 Beetleweight championship. The caliber of the Atlanta bots is really rising fast… I’m sure next year will be even more action-packed. All of NK’s matches are here.

NK took moderate damage to the weapon system during the tournament and would require a rebuild of the motor. Since everything else pretty much works, I will probably run it at Motorama ’09 or a local event.

Some performance pics…

NK does a number on Drumbeat. The gouges on the back side are a bit bigger.

A long skitter mark from when NK was inverted and balanced rather interestingly on its weapon.

Final remarks

So there it is. There’s something I want to change for future events, and that is actually being prepared. It used to be that the bots were really simple and I would have finished building weeks before the event and spent the rest of the time messing around and practicing. With added time constraints and the complete destruction of any time management ability I might have had, this is becoming more difficult. I’ll have to hold myself to the rule that if the bot isn’t finished and tested, I won’t attend the event. The fuss of having to deal with broken subsystems at the event is one whose ultimate cost is the fun factor in attending. All that results is frustration.

I was so busy with Ãœberclocker at DC ’08 that I took practically no pictures or had any time to just sit and watch the event. That’s not a very good attitude to approach the events with, especially one as laid back as D*C.

Until next time…