Archive for the 'Done!' Category

 

The Return of a Legend: ChibiKart Reunion Tour feat. Brushless Rage

Jun 20, 2017 in D.P.R. Chibikart, Motor Controllers

Brushless Rage is moving along quickly! I’m really hoping now to do a limited release (to people with known loads and needs) in time for Detroit Maker Faire. I’ve been working on it more sporadically in the past month due to other… obligations? but now I see the tunnel’s end. Here’s what’s been going on with it in the past few weeks when I haven’t been hiding under a van.

So that 2-way optocoupler salad was good in concept, but it ended up being incompatible with its purpose in life: to communicate bidirectionally so I could use the servo cable as a programming cable for SimonK/BLHeli enabled bootloaders.

It seems that the protocol requires the ability to tri-state, or at least assert both high and low logic levels. The circuit I modified can only drive high (or low) and otherwise has to rely on a pullup resistor, and that might not be playing nicely with the needs of the protocol. That is something I haven’t studied in depth due to its poor documentation, so if you know the specifications for the protocol, chime in!

Either way, it was looking like the final board revision would just use a single unidirectional optocoupler for the R/C signal input, and another galvanic-coupled pin on the same line but on the microcontroller’s side of the optocoupler as a programming header.

When the optos were bypassed (….again…. sigh) I was able to use the AfroESC programming dongle to re-upload firmware and change settings at will. The first step in this process is to flash the ATMega microcontroller with a socket and use the Enable Bootloader setting in KKMulticopter. Then I can just use the USB dongle instead of breaking out the socket every time.

I prepared two units this way, and also had heat sink plates cut. These heat sinks were designed a while ago for the Half-Rage that doesn’t exist yet – it has exactly half of the spacing of the mounting holes of RageBridge! So it was a good pick for the 6-FET power board for Brushless Rage. I cut out a square of silicone pad to fit underneath. In the ‘production’ version they’d obviously be die-cut to shape.

So now I have two mini Brushless Rages. What would I ever test them on!?

 

It’s back! I reclaimed the D.P.R Chibikart from the MIT shop not long ago, since they were refreshing a lot of the space displays and I’ve been gone a full year and a half now (…). This thing was kind of the pinnacle of my design class years, it having won an Instructables contest and all, and serving as a foundation for not only my next few years of students but for about a dozen or so builds worldwide (possibly more – those are just ones who wrote home).  A lot of tricks and hacks were used on it to make things easy to build for people without machine shop access. It’s also just stupidly fun to drive, and before the MIT IDC became populated extensively, we had stupid indoor go-kart races in it.

Over the intervening 2-ish years after my EV building class finished its run and now, it had been on display in various forms, so it wasn’t operational. The batteries had been removed and the motors’ sensor boards (which were partially designed for vehicle projects like this!) were broken off.  So I was just going to rewire it from scratch to accept two Brushless mini-Rages!

I focused on mechanical restoration first, like retightening some bolts. I had to add a new chain on the right side since the old one fell off (with the sprocket) a long time ago.

The sprocket itself is also quite well used, and the set screws are no longer very tightenable without stripping. I’ll likely have to drill these out to rethread them later due to the much higher potential torque going through them now with Brushless Rage.

Battery-wise, I decided to look for a 36V solution to make sure they can operate at 10S/36V reliably. I had some older 10Ah e-bike packs which were given to me with broken BMS cards. So I just removed them and soldered output wires in place. Classic!

The output wires terminate in XT-90 connectors, which were also retrofit to the existing wiring harness.

The Brushless Rage units are mounted with not much more than some Dual-Lock patches, and.

I had to pick through two boxes of random electronics to find my last working servo tester unit. In a pinch, these can be chopped up to accept Hall Effect throttles in place of their potentiometers. The Hall throttles typically put out between 1 and 4 volts instead of a full 0 to 5 volts, so the motor controller would need a calibration ability to get the full range out of it.

As expected, the Hall throttle’s 1 to 4 (well, about 0.9 to about 4.2) volt swing puts out somewhere around 1.13 to 1.85 millisecond servo pulse lengths. I set the Brushless Rages to accept 1.2 to 1.8ms as a result.

Everything’s bundled back up now!

Riding this thing has now become very interesting. Due to its very low gearing to the ground (only 3:1), it does have a hard start, but will always do so after a cog or two. This was actually a good test of how tuned out the SimonK firmware is; the mass-to-force ratio of an EV is usually much higher than that of a robot, even the 240b Sadbot, so it’s a tougher load to get going. The power is not unlike what BurnoutChibi ended up having, but more muted; BurnoutChibi had the advantage of being able to spin the motors much faster to get some ‘free power’.

I immediately ran into the problem of blowing the set screws right off the small filed flats on the motor shafts. This thing was originally designed for maybe 500-750W of power using the e-bike controllers, not an unlimited-current dump.

Either way, some replacement set screws and Loctite enabled some “road testing”. Here’s a highlight:

Results: My Starting-and-reversing optimized SimonK is okay in an EV application but only under some circumstances.

Specifically, you need to either turn down all the braking ramp speeds and magnitudes, or remove motor braking completely. In a robot drive application, the motor braking very closely following the command input helps decelerate the load and therefore reduce the momentum the motor has to start against the other way. In an EV application, that just means you decelerate as hard as you accelerate. It COULD be okay for some things, of course. I found that Chibikart drove well if I had the BRAKE_POWER setting cranked down to 1/8th of MAX_POWER, as well as the BRAKE_SPEED (ramp-down rate of the output PWM, basically) reduced to 3.

With these settings, I could modulate the throttle pedal to give a predictable regenertive braking effect. Too fast BRAKE_SPEED or too high BRAKE_POWER and you just end up impaling yourself on the handlebar here. I could see this on a tight Power Racing Series just thundering around never touching the brake pedal/handle, but it would still be a little annoying for a scooter or electric [skate,long,mountain...]board where you’d rather coast. In that circumstance, I’d just turn MOTOR_BRAKE off and forget about regeneration anyway.

For comparision, I found that Sadbot drove the best with BRAKE_POWER = MAX_POWER and BRAKE_SPEED at 4 (BRAKE_SPEED maxed out at 8 actually tried to slow the motor so fast it tended to either lock up wheels or slip motor poles on deceleration).

 

And with that, I sat down and pounded out board rev 5:

The main difference is removing the bidirectional optocoupler, as discussd, for a normal one. That’s still a 2-channel opto; I have yet to find a single channel (4-pin) opto in a package I like, but it does make more sense to use one here. Besides that, in rerouting some of the optocoupler traces, I got suckered into giving it better analog and digital signal separation (oh, boo-hoo…).

I also finally implemented the damned LEDs. SimonK actually has LED support, for signals that indicate throttle state and motor state. About time I figure out what this thing is doing!

Overall, I think Brushless Rage is ready to be fitted on something for Detroit Maker Faire. I’m not sure right now if I’m racing anything, or going to marshal and tech-safety-Stalin. I may choose to temporaily rebody Chibi-Mikuvan for funsies, since I want to keep the CMV shell in good shape after retirement.

Well, those are just thoughts anyway. There are also other thoughts:

Brushless Hipsterism Intensifies: Returning to Brushless Rage. Brushless Mini-Rage!? And Trying Hub Motor Drive in a Beetleweight

May 12, 2017 in Motor Controllers, Reference Posts, Roll Cake

Oh, Brushless Rage… how far you’ve fallen. It’s been standing idle since late last year when I got the first version running. Thereafter, it began having some rather obdurate power supply problems that I couldn’t resolve with a few different attempts, and with #season3 still unknown (TO. THIS. DAY. UUUUUUGGGGGGGGGGGH.) and having to pick up and move shops, I lost motivation. Now, with the spring and summer silly go-kart season coming up, me really wanting to pregame getting Overhaul back in shape ( *cries deeply* ), and my comrades over at Robot Wars screaming for assistance, it’s time to put my robes and wizard hat again.

The last time I really worked on Brushless Rage was in October. After tuning out the first one, I went ahead and made a 2nd one. I wanted to get Sadbot running on them for a few test drives.

Here’s my innovative housing for the two controller! Bolted back-to-back with drilled holes in the Ragebridge shipping box.

And that was all! It was retained by a few zip ties running through the bottom ‘breadboard’ baseplate. I didn’t take much test video of Sadbot running on them, unfortunately;really the only one that exists within easy reach is, uhh, this one. While it doesn’t show them getting whipped, they definitely don’t not work! Yay!

But not for long. I soon lost both of the units in further off-bot tuning of settings. They didn’t blow up, but simply failed to ever power on, with the LM5017 regulator simply sitting there getting hot. The only “fix” was replacing the regulator, and I say “fix” because that really didn’t fix anything, and they would die again within minutes or even seconds.

No problem… maybe it’s just an issue with the two boards. I’ll just try another one of the five total I ended up making….

Nope. Nothing. They died one by one, all to the same symptom. I tried redoing my math for the regulator for the 4th time, thinking maybe  I made a mistake somewhere. I even tried mimicking the reference design to try and get something running. I literally never do that.

At this point, I figured it must have been something incredibly dumb and simple I missed. But why would the first two have worked at all, even for a little while?! Convinced the solution might just suddenly invent itself, I stopped thinking about it.

And so here we are, a few weeks ago, when I’m slowly building up a new rev of the logic board that fixes up some trace routing problems and Little Blue Wire problems. Again, the logic regulators kept exploding, some times dramatically taking out the input trace like seen above. The little light is strapped across the 15V gate drive supply to give me a visual indication of it being on.

What is with me and being unable to use switching regulators!? I recalled the Ragebridge Diode Debacle of 2015, and decided to take one last Hail Mary run through the datasheet along with friends to carefully cross-check each other for boneheaded mistakes and…….

TI, you assholes.

So here’s what’s going on. The Vcc pin of this chip allows you to power it from its own output voltage, which is often fairly low, so it prevents a lot of heat dissipation in the chip since otherwise it would have to derive its own power from the voltage input (up to 95V). But what I missed is this only works up to 13 volts. My gate drive supplies were 15 volts by design.

Beyond that? Who knows?! It might work, it might not. I’m guessing my first two were just high enough in manufacturing overhead that they worked for a little while. Subsequent statistics were not on my side.

Okay, whatever. I cut off the 11.3kohm feedback resistor and threw on a 9.1kohm to drop the voltage from 15V to about 12.5V and let’s see what happens.

Ah, it wakes right up.

Of course it does.

So I decided to respec the gate drive for 12.5V. Why do this instead of go for the full 15+ volts? Because I’m really aiming to make this design work at high-for-robots voltages of 36-48v, possibly up to 60V nominal with a different power stage, so I’d like to save the power dissipation in the chip’s onboard logic power supply.

The change in drive voltage will slightly affect the drive characteristics and switching time. For now, I’ll keep all the power stage parts unchanged, but I’ll probably tune the gate resistor values later.

 

To get rid of the noisy ripples on the feedback network and to stabilize the switching frequency, I added some more bypass capacitance to the chip. This was not included in the design at first, since I figured my large ceramic input and output caps were nearby, but it really really wants its own little private capacitor on Vcc. Gee, I thought I was a princess at times.

So now this thing is pretty much bombproof. Here’s a video of it throwing around one of the 30-pound old MIT CityCar prototype motors (which I inherited 4 of after the project was dismantled):

In that video, it’s running from 36 volts. I tested it with a smaller motor all the way up to 50V input before getting too scared for my power supply’s life; I’ll need to try it on a larger high-for-robots voltage power system later, but nothing smelled imminently unhappy!

With the regulator death issue apparently behind me (again) I decided to push another board revision. This time, I added all the necessary bypass caps and changed the layout of the logic power supply, as well as take out some parts I decided were superfluous.

The logic power supply got a little smaller and more electrically optimal. The whole thing is just less messy now. I like it – it takes up around 1/3rd square inch of PCB space on one side. At the behest of a professional PCB engineer friend, I turned the inductor 90 degrees and joined it with the LM5017′s switching node with a small trace instead of a larger groundplane. This would prevent the switching node (a source of huge voltage swings in microsecond timescales) from broadcasting as much noise.

Besides some other minor trace chasing, what’s going on down below on the board is also something experimental:

That there is a bidirectional optoisoated I2C bus for transmitting data between two microcontrollers which should never meet directly. I had a single-direction opto input on the board revisions so far, but this prevents updating of settings via the SimonK/BLHeli type bootloaders. That means tuning the settings require busting out my chip socket every time, which is annoying. I reviewed a couple of bidirectionally isolated bus schematics and decided to try this one out first, since it involved diodes only, not transistors.

The problem is, the I2C bus is a open-drain configuration with pullup resistors and ’1′ bits transmitted by pulling the line down to 0v. I kind of wanted to try keeping the opposite polarity, so to speak (even though SimonK supports an inverted input setting) just because I’m used to thinking about things this way. So I tried flipping the circuit over…. pullup resistors became pulldowns, and common-emitter became common-collector, and so on.

It makes sense in my head, but I’m sure excited to see this work!

On the board, this is the layout. It doesn’t consume much more space than my previous 1-direction optocoupler setup, and can be bypassed for testing with 2 wires if needed. That’s the nice thing about keeping things upright signal-wise.

So before I sent this board revision out, I stopped for a moment to think who would really be wanting to use Brushless Rage. I’d designed the 12-FET board to effectively replace Overhaul’s 250A DLUX controllers (with more realistic ratings, mind you). I’d say the majority of people who would buy such a thing won’t be running motors that big.

Recently, the thought of a “Half-Rage” has been coming up in my mind as something worth pursuing. This would be a board with about half the footprint of a RageBridge 2 and supporting about 1/2 of the amperage. As some curious question-askers had innocently drilled into my mind, this would be an Actually More 30lber-Sized controller.

> mfw "When are you going to make a 30lber/12lber version of RageBridge?

 

With this in mind, I decided to make a copy of the power stage and began downsizing the hell out of it.

Step 1: Reap what I sow when it comes to the sheer number of vias I deposited under the FETs.

After bunching the FETs together, I referenced one of the earlier abandoned Brushless Rage layout ideas for the output wires. This board is now short enough that I’m comfortable pulling the phase outputs all the way to the right with the power. Keeping all my wires on one side is something I prefer.

Somewhat final routing of the fat bus traces here. I had to move a few gate drive traces, as there was no longer an opportunity to swap sides in the middle of the FET bank. Power+ runs straight from the bottom right corner, through the bus capacitors, into the high-side FET. Power- emerges from the current shunts and then has 3 paths to return to the buscaps before being slurped up by by the wire hole on the upper right.

Here’s an overlay of the signal board design on the power stage, showing roughly the size of things. The final power stage is 2″ x 2.75″. Not the tiniest thing, but I have more capacitors than you!

This board shares a lot of thermal characteristics with RageBridge, so I’m pretty comfortable calling this a 50A continuous class controller. 50 real under-partial-throttle amps, so that’s what, like 1,200 Hobbyking Amps?

In all likelihood, this controller will be able to handle an average 63mm SK3 motor in continuous duty applications like a silly go-kart. Robot-wise, it will probably be stressed handling the same in bidirectional drive mode.

Fast forward a few days and….

OhmygoditssocuteIjustwanttohugit and then make it run a 80mm outrunner on 12S violently. I’ve ordered parts to make a handful of these, and two are going on Sadbot ASAP to be driven until something blows up!

Direct Outrunner Hub Drive for Your Little Bot

Next up, something even smaller!

So I’ve long been a connoisseur of fine handcrafted hub motors. I got curious recently on using direct-drive small outrunner motors in an ant or beetle after thinking a while on the redesign of Roll Cake. Version 1 of Roll Cake was honestly just a braindump of a vision I’ve had for years for the shape of the bot, and everythng else came second to that. On the beetle scale, the multi-pulley serpentine pulley drivetrain simply had too much friction for the Fingertech motors (which were severely underpowered for the task) to overcome.

For the next version, I’m ditching the triangular cheese wedge shape for something more straightfoward. The cheese wedge will be back for a heavier weight class. Roll Cake’s design really wants to have the middle of the bot kept clear for the flipper linkage. I’m sure I could work around it with low-mounted drive motors and similar, but this was an excuse to play with brushless things!

I based my thoughts off Jamison’s mini-gimbalbot which used camera gimbal motors for drive with a small Hobbyking R/C car ESC. It drove “okay”, certainly capable of a weapon delivery platform. So naturally, I wanted to put some SimonK-capable controllers on it and see how the handling would change. I got a small selection of motors: A pair of DYS and Quanum 28mm motors as well as a pair of Multistar “HV” 460kv motors. 460 RPM/V is reeeeeally slow for that size of motor that isn’t a gimbal motor, so I was quite interested in them.

These are the gimbal motors. I like them for their pancakeyness – the Quanum motor is more 30mm and has a bigger stator.

Playing around in the CAD model a little for component placement. At this point was when I realized Roll Cake in this incarnation might end up looking a lot like The Dentist :P

I designed up a few hubs that bolt to the face of the motors and have a tapped middle hole to sandwich a wheel. The wheels are spare 1.625″ BaneBots wheels that I originally bought for Candy Paint & Gold Teeth.

Shown with those motors is a ZTW Spider 18A controller. My typical SimonK ESCs, the Afro series, were out of stock when I placed this order, so I took recommendations from people on what I should use. The Spider series are fairly popular these days among small bot folks.

The issue is, they come with BLHeli firmware, the other other open source drone racing / vaping rig development path. It’s a newer effor than SimonK and has a more polished interface. I’d read about it before, but not worked with personally. Other builders have said it doesn’t run robot drivetrains as well due to being much more optimized for propellers. So hell, why not – this was a chance to explore that side of things.

Here’s some real life CAD layout, featuring the Multistar motors.

I really wanted to use the gimbal motors, but they disappointed me in bench testing sufficiently that I didn’t even end up installing them. Basically, they can’t draw enough current to make torque at typicall little-bot voltages. With phase resistances of 10-20 ohms, they can really only draw ~ 1amp or so. I mounted one in a vise and could stop the motor with my pinky finger at full radio stick input.

These motors might be better at 6S and up, but for the time being, since all of my small-bot batteries are 3S, I decided to pursue making a test platform using the Multistar 460kv motors.

 

The platform of choice was…… one of Candy Paint’s spare weapon pulleys. I literally spilled my “preformed robot spares” bin on the ground and tried to see what was good to use as a base. Hey, it’s round and has convenient wheel holes in it already! All I needed to do was quickly whip up some motor mounts (3D printed) and I was in business.

 

Here’s everything hooked up. That nut is for a counterweight on the front to add some friction against the ground while turning. Otherwise, it had a tendency to keep spinning and spinning if you even thought about turning.

Communicating with the ZTW Spiders was a hell of an adventure in its own right, and I am putting this post under Reference Posts because I’m 99% I will need it again or someone else will randomly find it while needing the information. If there was any industry that continually pisses me off with how undocumented and tribal-knowledge focused it is, it’s the R/C anything industry.

So, here’s how everything went down. I lost my AfroESC USB communicator, so I purchased the Spider SPLinker advertised as working with the controllers. I also bought one of these stupid things:

That’s a “SimonK/BLHeli compatible” dongle called the ESCLinker. It allegedly can talk to either kind of ESC, but there was nothing remotely resembling a manual or operating guide; all of the search results for this brilliant device were people complaining that there was no manual.

So I’m writing the manual now: This thing does not want to talk to KKMulticopter Tool (my go-to for flashing SimonK ESCs). It will only talk to BLHeli Suite. As a matter of fact, I couldn’t get the Spider SPLinker to talk to ANYTHING. For all of my tuning here on, I used the ESCLinker tool.

Here is BLHeli Suite, which is hosted on the sketchiest possible website that is one tier above compiling it from the Git repository yourself.

Notice how I’m connected to the ZTW Spider now. The ESCLinker (and SPLinker) install as virtual COM ports.  The necessary baud rate is 38400 baud, not 19200 (Afro/Turnigy USB dongles, to my knowledge)

By the way, once I realized this, I tried to talk to the SPLinker and ESCLinker on KKMulticopter Tool again using 38400 baud; no dice.

Further investigation revealed that the ESCLinker needs these options to communicate to the ESC – both options 2 and 3 will work. So if you’re listening, people mystified by the ESCLinker: Talk to it on 38400 Baud and ask it to communicate to your ESCs with BLHeli/SimonK 4-way-if bootlader.

Ugh. One of my selfish reasons for wanting Brushless Rage is so it’s one known quantity and I never have to dick around with other people’s open-source bullshit again.

So with all that behind me, I decided to try out BLHeli drive on the little pulleybot. I went with intuitive settings based on my SimonK advice, which included “Damped Light” mode, a fancy euphemism for synchronous rectification/complementary PWM, medium to low timing and maximum start power. BLHeli also has a “demag compensation” feature which appears to delay commutation to compensate for current decay in the windings. Who knows!? I wasn’t given the imprssion that its users actually understood what it meant, nor does the manual really say anything useful.

I found that Demag Compensation turned all the way up gave the best performance, along with maximum start power. However’ it still couldn’t compare with my SimonK experience. It seems like even maximum start power is much weaker than what SimonK permits you to do.

Here’s the final test drive I made with the BLHeli Spider ZTWs:

I’m honestly not very impressed. I think BLheli is very much optimized towards multirotors and helicopters (hmm, maybe it’s even called BrushLessHeli for a reason!) and the settings are more high-level and mask the underlying mechanicals of the firmware. I think this makes it much more accessible to hobbyists, though. In the end, I’m not very enamored by it.

These were my final settings:

For a direct comparison, I decided to replace the ESCs with my old SimonK Afro 30 amp units. These have been on quite a few bots now, starting with the original Stance Stance Revolution, and they were completely beat up. But they still worked!

A direct replacement into the existing wiring harness later… we have SimonK!

I found myself in the awkward position of using KKMulticopter Tool to compile a customized SimonK formware, then uploading it via BLHeli Suite because my USB dongles didn’t talk to KKMulticopter Tool; I’d lost my AfroESC USB dongle a long time ago.  BLHeliSuite doesn’t seem to have a firmware editor window that I’ve found yet.

Here it is. I found the SimonK version so much more responsive that I actually needed more counterweight on the front. So, a non-fitting bolt gets zip tied to the nut! Now the bot’s a lot more controllable:

I like it a lot. It might even be worth doing 4WD to give me more yaw damping, or I’d have to design the bot to be well balanced enough on front skids, or something. I used my typical SimonK parameters: complementary PWM, maximum braking power, maximum braking ramp speed, and adjusted start PWM limits to something like 50%.

I’m aiming to get Roll Cake and maybe Colsonbot running for this year’s MomoCon in a couple of weeks, so hopefully I’ll post up some design news soon!

 

A Return to Inexpensive Chinese Van Lighting: LED Sealed Beams Update

Apr 27, 2017 in mikuvan

Boy, I’m all up on that chinesium recently, what with Chinese machine spindle drivers, the inaugural Chinese ~120lb Middleweights tournament which I helped transcribe results for, my Chinese production run of RageBridge 2sChina China China China. I love China. China is where all kinds of interesting things spawn from, some of which make you wonder who approved the push to production.

A while back, I broadly sampled cheap automotive LED products in an effort to convert all of Mikuvan’s auxiliary lighting to LED. That writeup is here. I’ve been pretty successful on this front, only having to replace one of the dashboard lights and another running light since then…. so they definitely don’t not work, but I’ll probably do another round of upgrades to the next price tier soon and see how the Market Structure has changed.

What I want to go back to is LED headlights. When I made that post, LED headlights were still quite a novelty, and very expensive. What generic products existed then were limited to these kinds of things:

I discounted them pretty heavily because they looked simply too Harbor Freight flashlighty for me – there’s no way you can aim those things properly. Just like a cheap LED flashlight, they wouldn’t have any meaningful beam pattern, and instead just be a soft wad of light. I wasn’t in much of a hurry to get real GE Nighthawks obviously, so I let the matter fall aside.

Until a few weeks ago.

While campaigning for Vantruck parts on RockAuto, my automotive opioid dealer, I noticed these under the headlights section:

Hmm, well that’s interesting. They look exactly like the GE Nighthawk units. I’d not researched the 5×7 H6054 sealed beam size before since I never had to; the 4×6 H4656 type didn’t have any LED listings on RockAuto, probably because everything sucks.

Well, now I’m beginning to think there’s a pattern. I looked in some other palces for H6054-sized LED lights, and….

 

That one is from TruckLite, which carries them along with other annoying Brodozer lighting products. For the record, this is a GE Nighthawk 5×7:

The problem? They’re all expensive as hell. I’m really not in the mood to pay $180+ for a single headlight unit, especially if I don’t know if they’ll work well.

Well, now I see the pattern. One axiom of Chinesium product finding is a corollary to the Law of Chinese Product Packaging Inertia, which states that if the products look alike, they most likely function alike in all but the most trivial ways. This has been my guiding principle for finding Chinese motor controllers and mechanical products for years.

If you turn that around a little, it becomes if multiple U.S. vendors offer the same looking product, there is likely a generic Chinesium origin. It’s something like that old quote that goes Behind every great man is a woman, except made of phthalic acid plasticizers and artificially manipulated currencies.

So I went AliExpress hunting. That didn’t take very long:

 

Score! I had what appeared to be the same kind of units as the first hit. Even better, the top 3 hits were three different approaches.

This is what always pleases me about the wild world of Chinesium: Nobody knows what they’re actually selling, so unlike Western product development culture where everyone focuses on one or two strategic approaches, the Chinese philosophy (if there even is an organized one… I don’t think so) might be spam the SHIP IT button . Recall my post about finding a new coolant pump for Chibi-Mikuvan, and how I found 3 different styles of water pump on Amazon in a few minutes.

So we have the Nighthawk clone on the left, what appears to be some kind of optometry examination device in the middle, and the “compound fly-eye” LED grenade on the right. Pretty much all of these listings, by the way, have random images of American pickup trucks or heavy duty trucks in their descriptions. They know. Since I know the Nighthawk style exists in the US as a baseline, I decided to spring for a set to try out.

While on Aliexpress, though, I got curious about the state of the 4×6 market. The styles are much the same, with most products being the LED-spam approach and some of a hybrid projector design like the aforementioned middle 5×7 product. Which, by the way, seem to be rather trashy for aimability also based on Dane’s analyses, as his Jeep XJ also uses the 5×7 size.

There was a style which was different , a combination of the LED-spam and the Nighthawk style divided high-and-low beam reflectors. These things used significantly fewer LEDs, so there might be some hope of the beam pattern being reasonable. I found a set from the same seller as who I was planning on getting the 5×7 size from:

 

By the way, don’t be deceived by the suggested transit time for the shipment. Often, you can pull down a little menu under Shipping which might reveal a very cheap DHL or Fedex/UPS option. For $14 I had all 4 headlight units in one week. I can barely coerce a shipment across the US in that time!

Fast forward a few hazy days where I think I remember some Brushless Rage work, and….

Nondescript Chinese gift boxes! Hurray!

The boxes are completely blank – presumably, resellers will have their logo and other information printed on them.

Here’s the 4×6 unit. The front cover is an unknown clear plastic; while it was advertised as a UV-resistant anti-scratch-coated polycarbonate, who the hell knows. I didn’t feel like taking a torch to these to sniff them just yet.

The casing is a very solid feeling cast aluminum with heat dissipation fins. Cooling, for the longest time, was the biggest issue plagueing LEDs and preventing their use in high-powered lighting. There aren’t any provisions for forced air or active thermal management (some modern car LED headlights are maintained by a Peltier solid state device), and I think they’re just counting on sealed-beam sockets on older vehicles being pretty open air. It’ll be interesting to see how these fare in a hot environment.

Let’s power it up! This is Low beams mode:

You know, I was honestly surprised at the beam definition. I pointed it across the dark warehouse and it wasn’t bad at all.  While looser than a modern xenon setup, it was still defined.

High beam lights up the top row of 5 LEDs, and boy is it bright. The bottom 4 still stay lit, however, so the difference between the centers of the beams is not as defined as for my current set of high-brightness halogen lights.  You’ll see this pattern change in the installation photos later.

 

The funny part was powering on what I called the “goat lights“. There’s a cute little LED strip in the middle behind a angular diffusing lens which is separately powered. They’re present as running lights. The extra wire emanating from the connector is so you can tap them into an existing DRL circuit.

So, overall I’m so far impressed. They don’t seem to be shitty. Let’s move onto the 5×7:

So this thing is interesting. Low beams shoot out the top half of the assembly, while high beam turns on the lower half while keeping the upper half lit.

It took me a minute to accept that yeah, this is also legitimate. The reflector on the top half is tilted slightly downwards, and the lower reflector is more straight-on. Actually desirable behavior for headlights. It seems like this one had some more R&D or engineering put into it. The beam pattern was even more concentrated than the 4×6 model since there is only 1 giant emitter per side, and there was more discernable shift between the high and low beam levels. I like it a lot actually! Unlike the 4×6, this type does not have a running light or accent. However, that style is also available in 5×7.

Alright, it’s install time. Since Vantruck is still mechanically indeterminate, I pitched the 5×7 units at Dane, so you might see them on his website soon. For now, I was going to install the 4×6 onto Mikuvan to see what the difference is like.

I set up the test in a parking garage, center-aligned with a spot marker line pointing at a wall about 25 feet away. I set up my camera on a tripod in the middle, immediately in front of the bumper aligned with the marker. I then tried to not move the camera for the entire test, including installation and aiming. The shutter and aperture speed were changed to a setting I liked and then they were not touched for the testing.

First, my regular old low beams. These are Wagner Britelite increased-brightness H4656 bulb modules. I’m not sure I can recommend them – as much as I like the light spam, I get maybe a little over a year to about 18 months out of them consistently. They’re advertised as having less lifetime, though, so I’m not even mad, just a little Disappointed Asian Dad.

Two defined spots, slightly biased low and to the right. The left light was recently replaced and I couldn’t be arsed to aim it properly, so it’s sitting a little higher and not quite as right any more.

Stock high beam halogens, unified spot high and a little to the right. Mikuvan’s 4-headlight setup means in high beam operation, they’re ALL on – it has two dual-filament H4656 type bulbs for standard low beam operation (which the LED units will replace) and two H4651 dedicate high beams.

Install was simple. I modified the marker light wiring harness on each side to plug in the “goat lights”, and here they are. Very goaty.

The main power connector, though, is actually an H4 type, not a H4656. This is some stupid automotive U.S. vs. The World standard I don’t understand, but it just involves a fast pin change on the connector to be compatible. Seriously, people, this is stupid.

After a few attempts at aiming, here’s what I came up with.

Damn. This was, again, taken with the camera in the same spot using the same shutter speed and aperture. I’d describe this as a curtain of light. The beam is so broad that I could barely aim it enough rightwards – I just about bottomed out the adjustment screw on the left headlight. However, it has a fairly sharp vertical cutoff, so that’s good for not glaring people.

Now with all 4 lights working in hi-beams mode, you can see how far rightwards the left headlight has been moved. This was all in an attempt to get it vaguely centered on the halogen lamp’s spot. I had to compromise here, as the difference in level between high and low wasn’t as drastic. I erred on the side of keeping the low beams lower to the ground, rather than broadcasting my lane change clearance to Mars.

I went on a run around the block to test everything out, and I must say it’s an immense improvment. My only concern was if it was significantly glare-inducing to someone oncoming because of the sheer width of the beams. I just vaguely tested this by squatting in the street at roughly the driver’s head height of the Honda Civic next to me. Result: Not any worse than what I get daily from people with modern HID setups, or even worse, from those HID retrofit kits that never aim correctly.

Here’s a test video I took shortly thereafter on a deserted road in Mexico showing the beam appearance. The scatter means it lights up distant road signs ridiculously well, much better than the halogen units.

So what to do after I have 2 of them? Now my headlight colors are mismatched, so I gotta…

Upgrade! See, now that the Chinesium base product has been hunted down and interrogated, I grabbed this set from a US seller instead. The box was exactly the same, just printed with some fancy letters and numbers and whatnot. The product? Also exactly the same!

DOUBLE GOAT MODE ACTIVATE. This photo is retro-futuristic as hell. EXPERIENCE THE AESTHETIC

You know how I can tell these were the same product by different manufacturers? My headlights are still slightly different colors. The color temperature of the two purchases is barely not the same.

Alright, so what have I learned here? The current low-cost aftermarket for LED headlights seems to have some viable products now. I did not crack open any of the units to inspect the components inside – maybe I’ll do that down the line if one dies, or I pick up another one. The units, both 4×6 and 5×7 type, seemed to be built well. My only concern is really longevity and ambient temperature tolerance. That’s something only operating these for a while will reveal.

Here’s a caveat though. With all 4 units running in high beams mode, it’s a ridiculous amount of light. I light up highway signs from like a quarter mile away easily because of the beam spread. I actually am concerned about it being unsafely bright when I use high beams to signal someone, like acknowledging a turn. It’s like a camera flash, but even worse. I’ve worked into the habit of briefly blinking the running lights on and off instead of flicking high beams to counteract this. A little bit of a damper on something otherwise very great so far.

If you go for a set, the general trend based on my own tests and reading reviews and discussions is aim them lower than you think you should. The light spread counteracts the lower spot with standard halogen lights, so aiming lower covers more of the road in front, and also makes sure you don’t glare people.

 

 

Motorama 2017: The Event Report; Or, How Not to Scale-Model Test Your BattleBots

Feb 26, 2017 in Bots, Events, Überclocker 4

And we’re back! I must say, in a way, I miss the abject chaos (read: spinners) of the full-contact weight classes, but it is glaringly clear that I need to get my strategy back in shape. In all, this event was a good wake-up call for me if I want to play the BattleBots #season3 game seriously, but that’s for a later analysis. Here’s how things went down, starting with the finishing of Clocker a few days before.

One of my last to-dos was making spare armor wedges. I’d already waterjet-cut the plates, so they just needed to be cleaned and welded. These wedges represent a simplification of the design used on Overhaul that I would like to transfer. They’re simpler, reducing the number of facets and panels by half*,while also retaining the same lower-edge durability with a (higher mounted) gusset. However, they are missing the “Jersey barrier” double-angle front that Overhaul has, and this will be important later.

So there are four wedges – two are made from regular cold-roll mild steel, and the other two from 4mm AR500 plate. I’m really expecting to run the AR500 plate as primaries, and only ditch out to the mild if they get (somehow) demolished. I suspect there wouldn’t be much left of the bot if that were the case, but it’s good to have options! The 4mm plate one weighs several ounces more than the mild steel, owing to higher plate thickness (.125″ vs .140″) so I’ll definitely have to free up weight for it.

I jigged the whole thing up since it tabs together into itself and tack-welded the panels together using a TIG welder, before switching to the good ol’ spray-and-pray MIG welder to blend the outside seams together and drop a huge interior fillet into whatever edges I could on the inside. I am still the only person I know who tacks assemblies together using a TIG welder, and then switches to using a MIG welder. I write this off as me having zero patience for welding, but needing the initial assembly to be straight, so I do it with the precise near-zero-force application of a TIG welder.

*Note that Clocker doesn’t have forward- or side-facing wubbies like Overhaul, so if those features are being added back, it would increase the plate count, but still not to the point  where I had them for #season2

Free up weight? Where the hell else can I do that from!? It seems like Clocker’s been pretty well dieted, but a few weeks prior I had started thinking of do I really need semi-infinite drive power? in the form of possibly replacing the AXi motors. They work great, yes, but are definitely overpowered and therefore heavier than I need. I decided to swap to a set of 42mm SK3 outrunners, which would reduce me by around 4 ounces per motor, allowing me to use the AR500 wedges as the heaviest configuration. Power-wise, the SK3 outrunners would have been just fine. They also pair up with the pinions of the 4:1 P60 gearboxes from BaneBots I ordered (due to the higher Kv) and bolt to the motor plate with no modifications.  This is a great combo – I highly recommend it as a plug-and-play 30lber-scale brushless drive rig now.

The motors were basically the last thing to arrive before I had to leave, so I decided to hold off swapping the parts in until we got to the event.

motomumu

The following image shows the totality of the glory of America:

 

 

On Thursday night, we packed Literally All the robots into vantruck, along with a sizeable amount of tools, support equipment, and other miscellanea. I planned to get there early-ish Friday to help set up and also to aid in Antweight & Fairyweight tournament logistics. Along with me were SawBlaze and Overhaul for display at the front of the audience section.

Sadly, this trip as-photographed did not happen, but that is an entire other story that has to be told separately. Long story short, the haulage minus SawBlaze and Overhaul were reshuffled into Mikuvan. This is a great story, I guarantee you (if you stalk me on the Internet, you already know it, so no spoilers!)

Alright, so it’s like 2PM on Friday now when I get there and everything is horrible and nothing matters. Let’s swap the motors onto Clocker:

Boy, those ESCs – spares left over from Overhaul and Sadbot, Dlux 160A HV units – are now officially overkill too. That’s what happens when you make a parts-bin robot. With the motor reduction, I was able to make weight using the AR500 wedges. Also in the same disassembly service were the floor scrubber tires:

 

Here’s a better look at them. I liked how they handled in the test box – still just a little light on traction, but very predictable. I brought along the Forsch (black) 60A wheels also, but decided to run these first since the Forsch ones felt a little more stiff.

Fast forward to Saturday and….

I feel like I’m at some kind of  career fair or anime convention. The people-ocean density was staggering; this is the largest Motorama Robot Conflict historically, and the largest year-by-year growth (over 50%). A lot of new faces, probably 25% of builders, and also quite a few returning legends. It’s a good problem to have.

In the interest of not dying, the 3lbers (beetlewights) were basically running in a parallel event with an 8 foot arena just off screen to the left, with only large bots – 12lbers, 30lbers, and 30lb Sportsman’s – running in the big arena.  Given the sheer number of beetles, it was the only way!

What’s great is MassDestruction helped spawn several ‘newb-vets’ who cut (….blunted?) their teeth in the MassD arena over the course of the last year.  These are two of Alex Hattori‘s robots. At this time last year, he had a 30lber made of two steel bars welded to a cast iron pot, and since then he’s cleaned house at like, every MassD ever, I swear.

 

 

Some other remarkable bots forged at MassDestruction from guys who work at, uh, MarkForged. Crap, my sponsor is beating me at my own game! What do I do!?

Another one of my favorites return – this is Pitter Patter, a 30lb shuffler (actually 45lb in the weight class) which way back in the olden days of Motorama 2015 was the original design model for Overhaul 1′s shuffle drives, which were basically a direct knock of this thing! For this version, the saw got smaller, but the shufflers got way faster… like 3000 RPM fast. This thing was cookin’ it in the arena.

Basically, you’re not getting anywhere NEAR the whole story just from these few photos. I remember when robot tournaments were this big, from the momentum of the first run of BattleBots, and I hope I see the 2nd Great Awakening of robots progress further still.

Anyways, onto my matches! This is Glasgow Kiss.

Topologically, it’s a good mockup of the Cobalt match. This is okay too! I’d actually hoped for a vertical spinner opponent so I can practice my anticipated strategy of using the ünicorn. However, I’ll gladly try to practice my horizontal-fending tactics too. The high level plan is to come into his weapon tangentially using the AR500 wedges and bounce him around, ideally towards walls, and try to corral into corners. More or less the same plan as for when I fought Cobalt.

I mounted the ünicorn anyway in case it could be used – I wasn’t counting on trying to swipe the belt pulley, as it’s too far inwards.

So how did this match go? Uhhh…

Well that’s not very typical at all.

Let’s watch the match video to find out what happend!

Alright, so my strategy starts out working fairly well. I’d say about 0:30 is when things start going awry. While I get a few more good tangential shots in, Glasgow Kiss is able to get one or two shots in which climb up the wedges and take out the clamp actuator and main lift gear.

At 0:49 I make a pretty bad driving error and end up plowing directly into the blade, so the forks and clamp are pretty much done by then – you’ll see me raise them to try and keep them up and out of the way.

The last big connection throws both of us apart across the arena, and I’ve lost all drive power by now so I tap out.

What Andrew (driver of Glasgow Kiss) does well is pivot the bot on the blade axis – in part a consequence of it being so heavy – such that it’s hard to just ‘get around the back of’ or execute similar strategies. He does this several times to leak away from Clocker’s grasp succesfully, leaving me to chase while he spins back up.

If you watch closely, you can see Clocker has some maneuverability issues right away. One of them is the bot’s right side having a tendency to stop and not reverse, which means I missed a few in-place turns. This occurred to me as strange – I mentally wrote it off to the smaller brushless motors in the drive cogging on start, but it definitely didn’t occur in test box driving. The heat of the match kept me moving, though, and I elected to try and drive around the problem, exercising the tactics I outlined in how2brushless at the bottom.

So Clocker seemed to be in one piece still at the end. Time to appraise the damage:

Check out the gear carnage. This gear is made from 7075 aluminum. It’s a nice and rigid alloy, one of the strongest by tensile strength aluminums, but it’s really best used in bulk such as gearboxes or bearing blocks and the like, not in thin sections. The gear is fairly heavily webbed out for weight, so it cracked through readily instead of bending. A 6061 gear would have bent and I would have had a chance to sledgehammer it back to something resembling flat.

 

Glasgow Kiss machined off most of this corner here when I was turned around. I’ve thought about making plastic corner hoopy-jiggles before, but haven’t been compelled to yet. As a part of a comprehensive horizontal weapon defense strategy, it might be worthwhile to do for Clocker using some 1/4″ UHMW or a thinner spring steel.

D’oh. I think the cross-arena impact stripped all the #6-32 threads from the end of the gearbox, so I lost drive on this side. On the other side, the chain jumped between the drive sprocket and the rear wheel sprocket.

You know what was awesome though? The AR500 wedges, on both sides, are practically untouched. Lightly divoted, but they were still flat to the ground. I did write off two of the lower wubbles on each side which had some tearing damage beginning.

But you know what – this setup went head to head with one of the biggest 30lb weapons a dozen times and isn’t much worse for the wear. What it really showed me is that Clocker’s frame and armor is perhaps overly built for the weight class now that geometry is compensating up front for frame thickness.

By near complete accident I’d say, the ünicorn came THIS CLOSE to piking the pulley and belt.

Alright, it’s time to fix everything up. Both sides of the bot had to be disassembled to replace the drive motor studs with longer ones. Since the P60 motor plate screws don’t go all the way through, there was some thread left which I could use with longer #6-32 bolts.

It looks like the frame was tweaked about 1/16″ in a parallelogram shape, from a similar corner hit on the rear right side (opposite the well-machined one), so the left side drive sprockets became offset enough to cause problems.

Getting the damaged lifter parts off was an adventure that took a long time. I’m now heavily rethinking the clamp collars on live shaft approach. It was fine in the Sportsman’s class where Clocker never took any real damage there, but with everything twanged up, there was hearty use of deadblow mallets, aluminum pusher tubes (to avoid marring the shaft), screwdrivers, etc.

What I couldn’t save were the clamp actuator and lift gear. I had thought about machining another lift gear the week before, but it remained just a thought. While I had a newly assembled and painted clamp arm ready, I didn’t bring spares for the clamp actuator. Without a backup clamp actuator – since Glasgow Kiss had basically wiped all the internals out also – I had to push everything back together in “spatula mode”, just with the lower forks and around 120 useful degrees of gear. Once again showing the difference between Sportsman’s and the full contact weight classes – just like in BattleBots, you should really be prepared to build 2.5 robots, one full set of spares and another for the things which break the most often.

So I delay my next match (and run down that delay as far as I can) to get spatula mode together. When I finally hustled into the arena, though, I discovered that Clocker could only spin in place or turn right. I clearly had wired one of the drive motors backwards, but what? Moving only channel 1 in my elevon-mixed (single-stick driving, basically) radio only caused the left side of the bot to move, with no response from the right side. However, it could obviously spin in place; without a motor being backwards, it means it could drive straight forward or backwards, but only turn right with 1 channel.

Without more time, I had to forfeit my match against Shaka, who, I will point out, somehow went 2/2 at this tournament using only forfeits. It won its matches by forfeit, but had endemic electronics problems which caused it also to lose by forfeit… I am told that in testing shortly after our non-match, it blew up.

Back in the pits, it took me a little more investigation to discover that my Hobbyking radio had somehow lost a mix. When you configure a radio for single-stick driving (or Delta Wing, Elevon, V-tail, etc. for aircraft), you assign mixes to tell channel outputs to listen to certain combinations of stick inputs. Here’s what a typical simple elevon mix looks like for my Hobbyking T6A-v2 transmitter:

There’s two mixes involved – one to tell Channel 1 to move with Channel 2, which on a typical radio is the vertical throw of the right-hand joystick. This means pushing forward on the stick sends the same signal to both outputs on the receiver, so the robot drives forward.

The other mix is to tell Channel 2 to move the opposite of Channel 1, which on a typical radio is the horizontal throw of the joystick. This means if you push stick right, one side of the bot moves forward and the other moves backwards, and is accomplished by setting the mix percentage to be -100 in both directions (do the opposite no matter which direction the stick is moved)

For me, the latter mix – the one outlined in Miku Pink – was NOT responding, despite showing correctly! This meant moving Channel 1 resulted in no opposite motion, just the bot pulling right. This was exactly the behavior seen in the arena, and I would never have discovered it if I had not accidentally put a motor in backwards.

I said the maneuverability tics Clocker showed in its first match will come into play later. I’m now 99% sure that this issue affected the match, and I tried to dynamically drive through it since I try to avoid stationary directional changes (turning in place) due to the brushless drive. A non-working Elevon mix will still kind of work if you move Channel 2 first – it will simply add and subtract Channel 1′s value from one side. In this case, it left the bot prone to pulling right, which is exactly what I saw.

How did I discover this was the problem? Well, I simply had it resend all the settings to the radio without touching a single one and it resolved itself. My radio literally lost a mix from its memory between Friday and Saturday for reasons unknown, even to the point where it convinced its software that the mix was still present.

I must say, I am not even mad. This is an impressive failure mode that I’ve literally never seen before, ever. Before anyone dishes on Hobbyking radios, though, I personally have owned a half-dozen (I keep accidentally giving them to newbies or random students and then getting another one) and also worked with hundreds back in my 2.007 days when they were the radio of choice for the class, and this is the first one I’ve ever seen DROP A SICK MIX like that.

With Clocker out of the tournament and the radio issue solved (!?), I waited for the 30lb rumble to join in on, where I basically overdrove the arm past the end of the gear immediately….. so I simply ran around as a wedge corralling bots in corners until the Vex sprockets’ teeth all came off!

My chain gliders probably wore  enough in that 5 minutes of crazy driving to make the chain skip on the sprocket (since it doesn’t have that great wrap angle), and the power of the brushless drive proceedd to machine the teeth off in short order. Ah well – it was a great rumble anyway. At one point I had every bot except Translationally Inconsistent, who kept slithering away sideways, piled in one corner.

Once I find a good video of it, I shall update the post to include it.

What’s great to see is that the 60A wheels hardly wore. Obviously this is both good and bad, since it means I could have traded hardness for more traction. For the 30lbers, I might go back to the 50A compound – Clocker in previous incarnations has run 50A wheels and I’ve been satisfied. Now is when pouring a few full-size wheels for Overhaul to try and drive around would be a next step.

We part with some shots of gourmet damage from one of Jamison’s loser’s bracket matches against Triggo. megatRON was upgraded to have an AR500 impactor disc on the end instead of a saw, and having that house brought down on you is capable of some serious damage:

this kills the triggo :c

Check out the 1/8″ heat-treated chromoly-steel shell rim also, from the same weapon:

This thing is not trivial; megatRON was actually one of my more feared potential matches because I have relatively weak top side defenses. Expect potentially interesting changes to Sawblaze for #season3 perhaps?!

Speaking of which, what takeaways for Overhaul do we have here besides the obvious bring a spare of the thing you don’t think you need spares of. Or three.

  • DAMN, THAT WAS A GOOD MATCH THOUGH. Honestly, if I had the choice of losing like that to Cobalt, versus the way I did via #setscrewghazi, I’d have picked the former in a hurry. I would have had enough spares to bring Overhaul back online quickly anyway, and it would have made for a much better show and much better test of the bot.
  • I’m highly satisfied with the AR500 wedges. So happy. It deflected the hits from Glasgow Kiss with ease, and also seems to have done its job of transferring the energy into the floor. AR500 has become a bit of a crack epidemic in robot fighting recently as more of it is readily sourced along with laser/waterjet services to handle it. It’s a nice alloy, really – heat treated to the high 40s Rockwell C already, and easy to weld with conventional consumables.
  • Good deflection is also a curse, because you aren’t in control of where the big beating-stick goes afterwards. I’m more convinced than ever – besides by this hit – that the double angle on the front of Overhaul’s pontoons is an absolute necessity. I designed without them for Clocker for simplicity and to see if I’m just being alarmist, but what the single slope let Glasgow Kiss do is deflect its own way upwards and clean house in the clamp actuator. I will need to think about how to  how to retain or improve this design for Overhaul, and to add it to Clocker.
  • I think it might be time for a scoop, for both Clocker and Overhaul. You know how Overhaul has the short arms that I used against Cobalt? Imagine those becoming vestigial and ending behind a angled steel plow which could nest in between the wedges on their inside slopes, making the front of the bot more contiguous. The remnants of this design can be seen in the forward-angled plate that resides on OH1′s forks.
  • It’s more clear than ever that a self-reinforcing geometry trumps material thickness outright. If scaled down directly without changes, Clocker would have 0.75″ thick frame rails, which it clearly doesn’t. It has 0.5″ thick, heavily-machined out side rails with 1/4″ thick cross-bracing plates, and that left the match against Glasgow Kiss needing a single screw extraction and maybe a hit from a good ol’ Engineering Hammer. What this actually means is I spent much of the 6 hour drive back from Harrisburg trying to rationalize that maybe I do need to have Overhaul’s frame remachined again. I’d be able to optimize for the geometry of the side rails. It would shed a lot of weight which can go into other systems I was running out of weight for, and really, based on how deeply Overhaul’s frame rails are pocketed, it’s almost useless to be made from 1.5″ thick stock. But UUUUUUUUGGGGGGGGGGHHHHHHHHHHHH.
  • I’m really, really itching to leave the clamp collars behind when it comes to power transmission to the forks. I think when it comes to fork improvements, just adding cross-bracing to Overhaul is enough, and I way more favor the 8-bolts-to-remove-an-arm setup on it right now for serviceability. I can replace a full set of arms and the clamp actuator on Overhaul faster than I could get the damaged forks off Clocker.

I would love the opportunity to test these hypotheses on a 30lb scale again in less than 1 year, especially because I (think) #season3 is still going down this year. Even if I can’t prove my hypotheses in short order, this was all good stuff to know!

It’s Motorama 2017 Time! Überclocker Changes and Upgrades

Feb 15, 2017 in Bots, Events, Überclocker 4

Since Franklin Institute this past year, I’ve been spending quite some time thinking about what changes I need to make to Überclocker for the annual winter robot party, Motorama. It’s the largest event on the east coast for years running, and the ONLY one left with full-contact 30lbers; I’ve gone basically every year since 2013, and sporadically before that (2008, 2010). This year is slated to be some kind of BattleBots #season2 reunion (where Season 2 was called “Motorama, the TV Show” since so many builders who regularly participate ended up on teams!), and there are some of us who are taking the opportunity to do some… scale model testing. Quick! What is the Reynolds Number of a flying Tombstone!?

So here’s what has been going on during the past few weeks! In my summary of the Franklin event, I identified a couple of strategic issues with Clocker which would also concern Overhaul for #season3, given that they’re built so alike.

The first was having everything ‘line up’ in the front. While it also included making the pontoons more adjustable, higher priority on my mind was making sure the arms have enough constraint that they don’t just splay out. We saw this happen in the Overhaul vs. Beta match where I caught Beta with one arm over and one arm under, so the arms because angularly misaligned. Recall that Clocker 3 and before all have multiple spanning elements holding the forks together; alignment was never a problem with that, but Overhaul didn’t have those elements primarily for an aesthetic reason (to maximize the forkiness). While Clocker sort of did have those constraints at Franklin, it was just one spacer stack, and that was quickly lopped off by megatRON.

 

So I’m gonna add more, duh! These two additional spacer & tie rod stacks are located out-of-plane with the one at the end, which will yield much greater torsional stiffness.

One issue is that another 18″ of threaded rods and aluminum tubes will put the bot back overweight a few ounces. Nonetheless, I intend to just build everything out to my desires, and then try to weight-cut from there, rather than compromising early. To pre-compensate a little, I decided to order replacement smaller drive motors. The AXi motors are great, but they are dramatically overkill for power, and I can definitely afford to lose a few ounces. Going to the 42mm outrunners will save me about 3 ounces a side, which alone might be enough. In order to utilize the smaller, higher-Kv motors, I also decided to order a pair of Banebots P60s in the 4:1 ratio instead of my current 3:1s, which should allow me to keep about the same speed.

Now, the 2nd big strategic weakness I want to experiment with is where it gets a little interesting.

I mentioned in the FI post about minimizing my defensive cross-section when it comes to vertical weapons. Those things – including drums, drumlet-drumettes (smaller in diameter and width) and vertical discs/blades are actually what I fear the most designwise, because they do two things to you in a match. One is flip your bot over, from which you need to recover (and which would take precious seconds where you’re vulnerable to followup attack from a good driver), but the more insidious one is ruining any straight edges you might have had where the weapon hits. A small KE weapon will put all of its energy into your material like a singularity; it will deform wedges and protrusions, basically preventing you from having an advantage again. All it takes it one fuckup, as Clocker’s match with Duck Yeah and even better example Blacksmith vs. Minotaur show. Notice how Blacksmith more or less has control of the match before it gets dinged once.

So to counter these kinds of weapons, you would have to do two things. Number one is keep them away from you, and number two is present as small of an area for them to touch you in as possible. There’s a lot of precedent in the sport with “keep away sticks”, including one used to great effect on Icewave last time on the show. To reduce my “vulnerable edge length”, then, I basically had to distill the front wedges down to points.

I take that back: this got interesting very quickly.

 


DUAL WIELD

So that’s revision 1 of the design. See those perforations? That’s for if I mess up and somehow manage to plant these into someone’s weapon instead of besides it. This design is intended to be cut out of AR500 grade steel, which is extremely rigid and springy but won’t stretch that much, so it will preferentially break at the postage stamp line. It’s like an active salamander tail system.

The saw teeth on top are the real bad idea here. Instead of a keepaway stick, I wondered what would happen if I made it a part of the offensive strategy. Most of these little vertical weapons have rubber belts attaching them to their motors. What if I just went straight for that with a very sharp stick? Stab into the gap between weapon and robot frame until you damage the belt or take it right off. That would take some serious driving and luck to pull off, which lured me to the idea further.

There was only one thing I didn’t like, and it was one of those “come back to what you CADed up last night in the morning and think again”. One of my complaints in the FI recap was getting stuck on MegatRON when we charged at each other. These extra-long death-shanks are attached just as the pontoons are, so if I run up on someone else’s wedge I can just as easily prevent Clocker from getting back off. Which is serious bad news when it comes to avoiding a vertical disc/drum spinner, since now they can just turn slightly for a broadside.

This led to revision 2:

Yeah. “It looks like a sawfish-unicorn”, or an Overwhal. That’s right, I decided to affix it to the clamp arm instead, exactly in the fashion shown.

This position I liked a whole lot better for two reasons. One is that it’s implicitly height-adjustable, and can actually be a manipulator weapon of its own. Clocker’s top clamp arm is not trivial – it is designed and built for about 500-600 pounds of closing force. It will lift a lot of things on its own, and is more finely positionable than the lower forks. It’s also more durable with its leadscrew attachment, but the leadscrew anchor is also a mechanical fuse for if things go very wrong and it gets the uppercut treatment – it will break away and probably fling the clamp arm backwards and out of the way, leaving the forks still usable. If I attached this to the forks, and they get bent, then my life becomes very difficult.

The second is a takeoff from the height adjustability. I realized that offensive unicorn strategy #2 was that now I can reach around weapons and bring the house down on their retreating sides, where the disc necessarily disappears back into the robot. With crafty positioning (or a lot of flailing) I could pretty easily literally throw a wrench in the works and shove a wad of AR500 directly between the robot and its own weapon. This would probably result in a very sad unicorn horn and ideally more sad opponent; for me, that’s why the postage stamp holes are kept, so not only will it break away on a successful landing, but will also do it and leave me a 2nd chance if I miss.

Strategically now, I can keep the clamp arm closed and all the way down and use the horn as a keep-away stick of minimum attackable cross section, and also manipulate bots from afar, or get it caught in something else like exposed drive wheels.

….and if you thought it looks silly in the CAD, it looks 10 times as silly in real life. I actually want to make another one of a different length now!

This is another ‘attachment of several ounces’ which would necessitate shedding weight elsewhere, which I will find. One thing I designed up previously but never implemented in real life was a set of light wedges, to be made of sheet 1/8″ aluminum bent into shape. I’m going to go ahead and make them, since they’ll cut around 1 pound off the bot each (Those steel wedges are HEAVY!)

I won’t need that much reduction in weight to use the horn of course, so maybe the configuration will add something else interesting to make up the weight, or just ballast. There is literally no point in weighing less than 30.00 pounds.

So that does it for major design changes. Moving onto more minor quibbles, I wanted to go back and have a look at the wheels again. The custom 50A cast urethane wheels worked beautifully at Franklin, and I now had a bucket of Simpact 60 and Forsch URS-2160 (McMaster part number 8644K24), both 60A urethanes with much higher tear strength ratings, to try.

Now that I was confident in the process, I revisited the hub design. I just designed the first hubs with circular thru-holes for rubber retainment so they could print without support, but the circular holes caused the diameter of the hub to start getting large. I didn’t have much more than the 1/8″ tread pattern’s worth of tread thickness per wheel. With a more rigid rubber, I might be able to increase the relative thickness of the tread portion.

I updated the hub to look pretty much like a scooter or skate wheel core – through-slots replace the circular holes, and the walls are thinner. This brought inwards the OD about 1/4″, which is great!

I also wanted to play with another tire geometry. A little earlier in the year, when Big Chuck’s Robot Warehouse was just being set up, we rented a floor grinder to strip the wooden floor of the decades of industrial grunge that had set up colonies within it:

Well gee, as soon as I saw that, how could I not clone the design in one of my own wheels? So if you’ve never used a floor grinder, a big sanding drum gets shoved over this flappy-wheel. To install it, you lock the rotation of the flappy-wheel and gently rotate the drum over it (in thise case, clockwise) while pushing it on. The flappy-wheel is effectively a huge sprag clutch with the drum as the outer race and the flaps as the ratchets/sprags. When the wheel is spun by the motor and the drum gets loaded against a floor, the flaps get forced open a little from the transmitted force of friction, causing them to push out against the drum harder, which causes more friction.

After I finished going “Well huh, that’s kinda smart’ I realized this design would get very good traction in one direction as each flap gets forcibly planted into the arena floor. The reverse direction might not be as spectacualr. Before I got ahead of myself with anisotropic traction designs, I decided to just imitate the flappiness  in my current tire design.

That’s the same helical tread sweep, just with many more slits of a greater depth and narrower width. I did this for “easy” (change the number and size of swept features) for the time being. I’d like to play with a straight-cut geometry like the floor scrubber in the future.

Printing this damn thing was an ordeal. Unlike the previous wheels, the molds could no longer be printed upright without support structures due to the way the helical threads are placed. Furthermore, the deeper tread features also prevent demolding in two halves, so I had to split the mold into quarters. Attempt #1 with supports was basically a no-go, since it was almost impossible to get them out cleanly and not leave little strands and hairs everywhere.

I next tried to print the mold wedges “pointy side up”, making a flat face on the outside of the circle for them to sit on. This was okay, but the nylon warped just enough on each print to make the edges not seal at all – this was attempts #2 and #3. I guess I could have made an Onyx mold too, since it has virtually no deflection, but by that time I’d mentally moved on.

The fourth and successful attempt was a single-piece mold which simply had the upper lip chopped off. I don’t even know why I thought the upper lip was needed now. Just fill to the top and be done!

That’s the model with the lip removed.

So how do you demold this damn thing? It was risky, but I decided the one-piece mold was okay because of the spiral nature of the tread allowed me to helically demold the cured wheel from the mold. And this ended up being completely true! I back out the hex bushing a half-inch, take a wrench, and untighten the wheel right out!

This worked quite well. Here are the two first wheels to emerge with the new material and tread! I stuffed the leftover mixed rubber into an old wheel/hub combination, because wheels are wheels. Notice the white core of the two new ones – they’re made from plain ABS, since I wasn’t about to waste the Onyx material on something I wasn’t sure could ever be removed from the mold. They’ll be on standby as low-priority spares nontheless.

Next up, the Forsch Polymers URS-5160. Forsch is one of those “Call Billy” companies that I always complain about – just go look at their 1997-chic website! Except this time, I was literally told that I had to call Billy (over in BILLING no less) and FAX him the order, then MAIL them a check. Credit card? Paypal? Pffff.       

Oh, Billy also leaves at 2pm each day, so I gave up after 3 days of failing to get in contact with him because I might have trouble waking up before 2pm on most days. Luckily, someone clued me in that McMaster’s general purpose pourable 60A urethane is manufactured by Forsch, otherwise I would have given up completely.

So why the hunt for a product which tries so desperately to not be purchased by anyone? Well, it advertises around 25% more tear strength and ultimate tensile strength than Smooth-on’s Simpact 60. Smooth-on is geared towards being easy to use – everything is made 1:1 or 1:2 mix ratios, so it doubtlessly sacrifies some strength and performance for convenience. I figured that polyurethanes worked like tacos – the shadier and harder to find that a Mexican restuarant is, the better the food. This has been almost bulletproof in my experience. I made it a point to obtain a Forsch product and use it like Robot Jesus Himself intended.

What I really want to try getting my hands on is the URS-2450, which has basically the same tear strength but in a 50A durometer. May Billy and I finally meet in the grand arena of procurement soon.

I cut new wedges out from AR500 plate. These were what they were meant to be, but I couldn’t get the material in 1/8″ (or 4mm-ish) thickness in time before Franklin. This was actually cut from one of Jamison’s spare plates left over from Sawblaze. I’m preparing them for welding here by grinding the incredibly thick scale they all seem to come with off.

Stay tuned for more, though with Motorama now 2 days away, I might just be updating after the fact! Still to come are the making of the pontoons, the spare lighter drive motors, and maybe a little bit of wheel testing!