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.

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…

Alright, so I’m in Atlanta.

Sunday and Monday evening were mostly spent tuning the signal module. I found out that the Victors do indeed have optocouplers larger than the asses of most Hollywood women, and not even the Atmel chips could drive them. In the end, I still have to splice some small signal transistors (ran open-emitter style for non-inverting buffering goodness) into the PWM cables so the Victors would notice my desperate attempts to communicate.

The signal module is an Arduino embedded Atmel controller, and the code was all written by me. It’s my most complicated recent microcontroller adventure. I excavated a little of what I learned about discrete-time control systems from 6.01 to implement the control loop. Essentially, the AVR waits for an incoming R/C signal and reads each pulse width to determine my throttle stick position (and thus the fork position). It then has 18 milliseconds to determine what to do with it. 18 millseconds at 16MHZ is alot of time.

The AVR chips have a 10-bit analog-to-digital converter, so it reads the arm potentiometer and returns a value between 0 and 1023. Conveniently, R/C PWM signals have pulses between 1000uS and 2000uS, which is close enough to 1024 and 2048, 2^n values. So it was rather easy to make a proportional-only controller by scaling the armpot values. I added an integral term to the output equation also to get rid of the steady-state positioning error that resulted from the Victor controller’s deadband around 1500uS. This got the arm responsive enough for me to call it a night and tune it later.

Then stuff broke.

Of COURSE I had to go back and make a few solder joints more permanent, and otherwise touch up the PCB I mounted everything to. I didn’t notice that I had made a very tiny solder bridge between +22 volts (the robot’s main battery) and the output side of the 5v regulator chip.

When I plugged it back in, the AVR controller quite literally exploded in my face. It’s in several pieces.

So then I really did have to call it a night…and started packing the bot up. I ordered a new Arduino board (since the roasted one is very securely soldered to the PCB and not worth the effort to extract) and should have it next week. For anyone interested in learning from my adventures in making a giant servo, I’ll post my code when it’s cleaned up and tuned.

Uberclocker

I stuffed two suitcases full of robot equipment with clothing and personal supplies interspersed between the goods. Here’s Uberclocker locked into its handy bot carriage, with spare parts and hardware. As there was plenty of space in the suitcase, I zip tied NK and Pop Quiz in, to keep the bots in one place. The other suitcase contained the charger, transmitters, and tools.

Somehow this all got past Homeland Hilarity, but the botcase suffered a bent caster wheel. In order to make the thing self-supporting, I borrowed a hammer from one of the baggage offices to beat it back into shape. Wait, I just got handed a massive claw hammer by an airport desk clerk? Huh?

Anyways, in Atlanta, I got to work on the new clamp arm actuator. Here’s a rendering of the new design.

The gist of it: Solid aluminum structure, indirect gear drive. The leadscrew is fixed to the fr0k and does not rotate – instead, this whole assembly climbs up and down it. This takes all the loads off the motor shaft and instead transfers it to some big chunks of metal. The only way to destroy the clamp arm now is to rip the leadscrew clean out, or applying so much force that the nut strips out.

I’m not saying this can’t happen, but it’s unlikely to happen at D*C.

Here it is implemented. Yes, I’ve been COMPLETELY spoiled by easy access to machine tools – while this would have taken me a few minutes walking to get done at MITERS, I had to drive no less than 50 miles round-trip to make this sucker, and of course make Dale put up with my really bad habits that I’ve accumulated from working without supervision.

Suburban Atlanta needs a few you-build-it freelance engineering places, so I think I’ll make it a mission later in life to start them. Although I suspect the culture to support it is missing…

This actuator is a throwback to something I made in late 2005 for Science Olympiad. My robot entry for that year had a linear actuator attached to a movable jaw that could clamp down on objects. I custom-made the actuator using some gears hacked out of an R/C car, a block of UHMW, and patience on the drill press. The output gear is threaded on the inside to ride up and down a piece of threaded rod.

Pop Quiz 2

In the same machining session, I made a new blade collar for Pop Quiz. This retains the blade on its drive motor, so it’s a pretty critical part. Stock steel shaft collars didn’t come in the width I needed, and would have been a tad too heavy. So I made a quick aluminum clamp-style shaft collar, 1/4″ wide, 1.25″ OD.

I’m still facing severe failsafing issues with Pop Quiz. It’s been a reported problem with the tiny GWS receivers, and there seem to be no workarounds besides the usual anti-RF stuff, but the thing is still pretty jittery. It goes nuts if I turn the radio off when anything is moving.

Pretty bad for something that can remove outlying body parts with ease. I might switch back to the other micro-style receiver and mod it for height.

Here’s Pop Quiz in its final state.

In other bot news, Nuclear Kitten’s replacement battery pack arrived and will be swapped in shortly.

Dragon Con is A WEEK AWAY!

Actually it is. From the past several builds, I have come to a conclusion that beginning exactly one week before I am to leave for an event, things will go horribly wrong that will leave whatever I am building crippled and disabled and unable to function up to its full potential. We saw this with TB4.5MCE for Battlebots IQ, where I lost an arm ESC and couldn’t obtain a main battery worth its weight in beans. TB4.5SP1 for Motorama had a whole third of the bot go out two days before I left, and only some last minute hacks allowed it to run at all.

There are plenty of rational explanations, of course, since I usually get to rigorously testing my engineered systems only in that last week or so, and untested systems like to break if they’re not properly designed and built. But the fun explanation is that the robot gods are just out to get me.

Oddly enough, nothing wrong wrong with NK except losing a LiPo cell, which is not a terminal disaster.

Over the past few days, I have been slowly wiring up Uberclocker. Working in an environment where everyone else is also working on something interesting means I get distracted far too easily, so it’s really taken _that long_ to wire the bot up.

Here’s most of the wiring. For a bot with 5 motors, 4 controllers, and 2 batteries, the wire layout is surprisngly clean. In this picture, the master power switch had not been mounted and no cell balancer wiring is installed.

This was the condition of the wiring for the bot’s first remote-controlled powerlift – the previous one was by touching wires to battery leads, which isn’t exactly a legit in-arena tactic. So what weighs more than or equal to a 30lber?

Well, at MITERS, plenty of things, but the only thing compact enough was this…

…45 pound rackmount uninterruptible power supply battery pack.

I approve of this bot. It can raise the 45 pounds pretty briskly and can suspend it in the air with no motor power applied (with the controller in Brake mode), and can bob it up and down. I don’t have an amperage number yet.

As expected, the back end of the bot lurched upwards on beginning the lift, but fell back down due to the support from the rollers in the front. I didn’t practice balancing the bot with a load on the rollers, but that should probably happen some time.

Then stuff broke.

First, while running the clamp arm with no load, the Banebots 12-45 controller popped its reverse direction. It was a very audible (and frightening) pop that made me think one of the FETs on the Victor 883 controlling the fork motors fried.This was strange, since I was using a motor far, far smaller than what the BB controller should be capable of handling, and it was not clamping down on something or hitting a travel limit. Just small reverse throttle.

So I have started the replacement-under-warranty process with Banebots. We’ll see how THAT one goes – chances are they’ll be considerate and ship me a new one in Atlanta.

After the mild scare, I decided to continue testing by dropping in the ANT150 controller from Nuclear Kitten. But again, that didn’t last long, because…

… the actuator motor shaft snapped. The B62 has a reported history of fracturing output shafts, and it looks like the bug hit me. However, it looks like the shaft actually broke in flexure, which tells me that the radial support at the base of the leadscrew is poor.

I’m not surprised. When the clamp arm hits something on its way down, the load on the actuator is essentially pure compression. Any buckling of the part connections at all could lead to catastrophic failure, which seems like what happend in this case.

This is bad. Very, very bad. Considering the whole leadscrew assembly was green Loctite’d together, it’s going to be nearly impossible to extract the broken shaft stub. A replacement motor is a hefty $30, and I’d have to buy and machine a new section of leadscrew.

Bad indeed. Without the upper clamp arm, Uberclocker is a giant spatula of questionable sexiness.

I’m now in the process of specing out parts and designing a new leadscrew machanism. This will be an indirect drive type device that will take the stress off the motor shaft itself. The motor, furthermore, will be mobile along with the upper clamp instead of being pivoted in a fixed location on the forks. Instead, the leadscrew will be fixed with a pin type joint at the base.

Using an indirect drive leadscrew mechanism, similar to the “beak” of my 2005 Science Olympiad robot, should make the whole thing more reliable anyway.

This will have to be fabbed in Atlanta, since I won’t get any parts I order now by Monday and actually get anything done. So with the clamp out of commission, I tied it to the fr0k to secure it and continued finishing and finalizing the wiring. I installed the battery balancer plug, another Convenient DB9 Connector of LiPo Balancingâ„¢ , physically mounted the power switch, and cut holes in the top plate to accomodate them.

Besides the DB9 connector, I also put in a direct connection to the battery using a Deans female side connector mounted to the left Ebay. For this bot, the charging current needed will exceed the limitations of the 24-22 gauge wire that fits in the DB9 connector, so I will use that only for the charger’s balancing function, and the big connector for actual charging current.

After tidying up the interior some, it was time for a beauty shot. Cheesy cell phone camera style.

The bot’s now only missing stickers and blinkenlichten.

And also the signal module. The signal module is my name for the receiver + fork controller combo that will occupy the left side Ebay. The fork controller will take input from the Spektrum Rx and do two things – one is buffer the signals for the Victors, and two is correlate my transmitter’s Throttle stick position with the position of the fork. It will take input from the potentiometer mounted to the fork and drive the ESC accordingly.

I decided to let it process al l the receiver signals (and passing drivetrain commands straight through) instead of making a separate buffer board for the drive only – it keeps the wiring cleaner and allows for future expansion of more advanced control schemes.

There is minimal hardware left to implement, since the microcontroller already comes with its neato support board.

There are exactly three days left. Can I get everything working?!?

So I can’t find the sub-micron sized grain of dust or metal shaving that is caught in the lens actuator of my camera. Unfortunately, this means that I will have to start haunting Ebay and local consumer electronics outlets. Until then, I suppose everyone who reads this site (all -0.000001259 of you) will be in suspense, save the occasional grainy cell phone camera picture.

The basic rundown is that Ãœberclocker is ready to be wired and NK is also approaching mechanical completion.

Ãœberclocker

I drew up the “EBay” assemblies and prepared flat patterns to make them out of sheet metal. Unlike TB4.5SP1 which had all its electronics in a bunch, Ãœberclocker features “distributed electronics”. There’s not really an advantage to either method, just that I couldn’t find space in this bot to slam all the electronics in one place.

Each is a work of 1/16″ aluminum origami (read: smashing in a vise and banging on it while wielding a torch) that bolts to a close frame member. There is nothing secured to the baseplate, unlike TB (and all my previous bots). Furthermore, all of the Ebays are dismountable from the outside.

This is the left side Ebay, which houses the main switch and Convenient DB9 Connector of LiPo Balancingâ„¢. The big switch came off a 1980s era PC power supply which, despite being a 7 inch cube, could manage maybe 200 watts. It is mounted such that the top bezel is flush with the top cover plate of the bot. A little rectangle will be cut out of the top plate to pass it.

Since Ãœberclocker isn’t a severe duty bot, I decided to forego making a normally closed switch like I did for TB. The detent is strong enough for me to not worry about it randomly clicking off.

The rear Ebay clamps the batteries between itself and the rear of the bot. It also carries the Victor 883 controllers for the drive motors. The right side Ebay houses a third Victor and a small Banebots ESC to control the clamp motor.

fr0kp0t mounted. This was an afterthought, and I really didn’t want to take the entire thing apart again, so it was just clamped and hand drilled. The potentiometer is rather exposed for something which will be telling the fr0k everything about where it is in life, so it might get a larger metal cage. The pot is coupled to the fr0k through the shaft set screw.

There is currently no bottom hard mechanical stop for the fr0k, and so it can swing all the way around the bottom of the bot (no doubt ripping off the entire bottom plate in the process). To prevent this, I’ll add some things that stick out of the fr0k towers. While I could easily limit the travel in software, a hardware backup is good for preventing self-eating disasters.

So Ãœberclocker is ready to be wired up and programmed. The fr0k, with the chain tightened (by removing one pitch with an offset link), successfully powerlifted 30 pounds, so I know torque isn’t a problem. Maybe there will be a drive test soon…

Nuclear Kitten 5

NK went from 0 to about 50% done in a day due to the “snap-together” chassis. The only thing I needed to build for that were some nutstrips ( 1/4″ aluminum squares with regularly spaced tapped holes), which was tedious but trivial. Past that, I had to machine up the weapon motor and drive wheels.

I specifically bought a 4-40 spiral-tipped tap so I could powertap all the holes, 7 each in 12 nutstrips. Sadly enough, I’m short about 4 inches worth of 1/4″ square aluminum stock to make the last of the nutstrips. This is within range of just biting the proverbial bullet and machining down some bigger stock.

Blurry ass-picture showing some frame bits and the nutstrips. Ignore the obvious non-trusses that populate the inner rails. My excuse is that it was 5AM Joltgineering – I’m not sure why I didn’t just link the corners with triangles instead of making an ugly V shape.

I like this “Chinese Puzzle” frame – I think I’ll keep the tricks in mind for future projects.

While the waterjet pump was still primed, I tossed on a plate of 1/4″ 4140 and cut out the blades.

Because the blades are now steel, they are thinner in profile. This should be more than enough for 3lber duty, especially after heat-treating (famous last words).

After discovering that the grungy MITERS horizontal bandsaw cut much faster when I dropped a weight on the end of it, I started on the disc motor. The motor itself is almost identical in structure to my wheelmotor and much simpler in construction. I also didn’t have a stiff and consistent tool holding device when I built the wheelmotor. Overall, this resulted in a very fast build of the disc motor structure.

I made two side plates out of 3″ aluminum round and the center axle out of 1″. A steel pipe was turned into the magnet ring. This steel pipe appeared fine on inspection, but upon contact with a cutting tool, turned to powder on the inside. Fortunately, the rust wasn’t deep enough to affect the final ring dimensions.

I also made all four drive wheels. Each wheel consists of a stock SDP (redundancy?) pulley, an aluminum “rim”, and an O-ring “tire. The process was fast, since each rim only had radial features that could all be made by selective parting tool use. The drive motors themselves are in transit and should arrive Monday. Previously, I ordered a few Speed 300 size RC motors off Ebay to retain the absurd speed and maneuverability of NK4, which featured those motors spliced into the aforementioned gearboxen.

Upgrading the wheel size the morning before I ordered all my parts (more 5AM  Joltgineering), I failed to account for the fact that one of the frame connector pieces now interfered with the front wheels. Something will probably be sanded down.

After taking a Taco Bell break, I put the disc motor together for a test fit. This motor has a very tight airgap to maximize torque, and I was worried about the tolerances adding up and causing the stator to grind against the magnets. To my surprise, it ran concentric and true – with no rubbing. Cheers for the robot gods. I then went back and preliminarily installed all 28 magnets (in groups of 2) with ultra-thin CA glue. The empty spaces will be filled in with epoxy.

So, here’s a picture of NK in that “well, it LOOKS done” pose.

Old NK is undergoing the scrapping process to extract the goodies (there’s not much left).

Only a few spacers here and there remain to be done on NK.

So the summary of things to do is:

Ãœberclocker

1. Wire up!
2. ???
3. Profit!
   1. Make bot carrier

NK5

1. Weapon pivot axle and spacers
2. Wind motor
3. Tune drivetrain for belt tension
4. Wire up

PQ2

1. Wait for giant plate of titanium (est. Tuesday)
2. Cut blades out of Ti
3. Machine a blade retaining collar
4. Integrate receiver and mixer into a single module
5. Think of how to get reception

A week remains…