Completing Überclocker 4 & The Leadup to Franklin Institute 2016

Saturday, October 15th, 2016 @ 0:53 | Bots, Events, Überclocker 4

We interrupt this irregularly scheduled build report for VAAAAAAAAAAAAAAAAANNNNN TIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIME!

Contrary to most years that I’ve returned from Dragon Con by road, I did not have a job pressing need to return to Boston, so could take a few days to roam around Atlanta. This time, I revisited a couple of old haunting spots from the high school days – namely, junkyards, flea markets, electronics shops (what remained, anyway), aaaaand McMaster-Carr. When it was time to return, I decided to do something which I’d been thinking about for a while, and had been recommended by “car people” friends – hit up the mountain roads of the Blue Ridge Mountains and Great Smoky Mountains National Park. Many moons ago, my parents took me on a road trip to Harrah’s Cherokee Casino in North Carolina via some scenic routes such as U.S. 441, and I’d been reading up on the area as of late. Back then, I certainly didn’t appreciate the scenery or natural surroundings as much as I d…. nah, I still don’t, but those mountain curves I remembered as being awesome.

I solidified the plan as diffusing through North Georgia using U.S. 19/129 through Blairsville into North Carolina, then ascending via U.S. 74 eastwards until the intersection with N.C. 28. From there, I would follow the Tail of the Dragon (returning to U.S. 129) and eventually end up in Knoxville, from which it is easy to return to the Interstates. It was an incredibly scenic adventure – I definitely want to return here next year and perhaps try a different tourist trap on the way down – I’m hankering a little for the Diamondback 226.

The careful reader would notice that yes, this means I took a heavily-loaded Mikuvan filled with an entire Dragon Con of robot gear with Overhaul in the back and everything up and down twisty two-land forested mountain roads.

b o d y   r o l l

And bought the “unflattering water slide photo” at the end!

I must point out – loaded heavy in the back with about 500 pounds (Overhaul, all the robot gear and tools, all of Jamison’s robot gear and tools, and whatnot) made the handling and ride better than empty, I’m pretty sure. I tend to throw MV around like a go-kart, and the back end does get light due to the front mid-engine and front driving position. In winters, I regularly keep tools and heavy objects in the hatch to get more purchase during slushy or snowy weather. So I think riding empty might not have been any better, and it’s not like you can actually go that fast on the road while maintaining your lane. It took a few turns to “get it” (and probably warm the tires up a little) before I began really tossing it into the curves. “Continuous tire squeal” must have been concerning to bystanders…

Here’s the whole run from my high-mounted dashcam. Note that this is a very different and weird position compared to most dashcam videos – it’s mounted high up on the very tall cabin, pointed more down than forward, and Mikuvan has no front. Some people actually have said it made them dizzy due to the different motion experienced.

I think around the 3-minute mark is when I started getting more adventurous. Cynthia can be seen trying to constrain herself, her phone (recording a different perspective), and random objects in the cabin.

Anyways, fun times. But you guys came here to see Über-haul work! Here’s what went on in the few weeks before Franklin 2016. In this timeframe, I also went to New York Maker Faire to marshal the Power Racing Series race there again – Chibi Mikuvan came along as an exhibition item, but I didn’t race. I’ll need to post an update about the Detroit and New York Maker Faires at some point.

I did a fair amount of work in the remaining few days in Atlanta. One of the first things I did when I returned was drop by MITERS and use the large drill press to finish drilling some of the frame holes all the way. I then assembled the bot more completely to test the fit of everything.

Verdict: Yeah, sure, whatever. #zerosigmas

One element that has been missing up to this point which you people keep pointing out is that Clocker 4 is missing the classic Overhaul ears. Yes, yes I know, I just haven’t gotten to them yet.

The purpose of the ears on Overhaul 1 were to permit self-righting – the bot had a stable 45-degree-roll upside-down orientation that in testing, we could not get out of. Overhaul 2 addressed that problem a little with geometry, but it was still there – so the ears appear in a slightly different shape. The shape of the ears is a compromise between eliminating this 45-degree stable spot and extending far enough up to tip the bot over once it was fully on its back, using the action of the forks.  OH2 traded some of this latter ‘stickup’ distance for more sideways extension, which is why its ears appear proportionally smaller and flatter than OH1. The tradeoff is it takes a full power swing of the forks to get back over, something I was not too happy about and which contributed to a fair amount of pre-event paranoia in the team.

For Clocker, I wanted to explore the ‘high stickup’ option. This meant the ears have to be shifted forward some to not interfere with making the upside-down stable spot worse. It also makes the bot look very much like some kind of micro-fox or Gundam headpiece.

The ears are designed to be printed using Onyx with additional carbon fiber perimeter reinforcement, so they ought to be immensely beefy. They have to stand being landed on if this thing gets flipped.

I printed these while in Atlanta, but the installation came afterwards. They push into one of the circular cutouts in the clamp arm, have a flange to maintain the tilt angle, and is sandwiched together with 4 bolts.  This configuration means they don’t wrench on the side plates of the clamp arm, which are aluminum and would likely bend, instead bracing each other using the bolted connection… It also hopefully also makes them replaceable. I may pursue a similar strategy for Overhaul this coming BattleBots season, even if the ears are individual weldments.

The chain path for Clocker 4 was never quite decided, but I figured there would be a third tensioner or chain guide involved to force the chain to contact the motor drive sprocket more. This manifested itself in this slip-on tensioner that I designed after seeing the most perfect location for it also coincided with one of the frame rail trusses, so it was easy to make something that  mounted directly on it. Unlike Überclocker 3, it doesn’t have roller tensioners on eggy cams, so is not adjustable in this manifestation, maybe the next one.

Problem: I got paranoid and piled everything onto my scale, and it came out two pounds overweight. Wait, what? The CAD model says 29.5 pounds!

After significant investigation, it turned out that my beautiful PAXi motors were never assigned a finished weight. They each contributed 2.2 pounds to the bot in real life, but were modeled as only 12 ounces apiece…. basically, the P80 parts that I did assign weights for during the design of Overhaul 2….

However, I might actually swap these out before FI 2016 for modified P60s, since having the armor weight back would be nice.

Well then. Turns out I needed more than armor weight! Even eliminating 1lb each would still put the bot overweight. The remainder, I figured, came from wiring (all the 12 gauge adds up) and additional hardware.

Alright, time to borrow a P60 model and smash the AXi onto it.  At this point, I do not own a P60, so I didn’t know how easy this was to do, but it was still 2 weeks out from FI so there was plenty of time to find out.

Since the frame was designed around and cut out for a P80, I actually had to make a P60 to P80 adapter plate. This attaches to the front of the motor using its existing tie rods in counterbored holes, so the front face is flush. The tapped holes are at the P80 bolt circle locations.

A week later, a pile of BaneBots equipment appears. I took the opportunity to also investigate their new BB series gearboxes – Building Block, so named because they feature stackable designs similar to the Vexboxen. I got a BB150 thinking it was similar to a P60.

I was wrong. It’s like a P70 or something, literally almost the middle in dimensions between the P60 and P80. Their BB220 gearbox is the same square size as the P80, however.  Internally, it’s quite massive and a huge improvement over the P60 architecturally, with widely spaced bearings and a double-thick output carrier plate.  I will keep the BB150 around for other applications – it’s too big for this one. Banebots have come a long way from their early brass gear days, but I feel like people never quite let them live that down. The six P80s in Overhaul 2 speak to that well.

THIS IS WHAT ROBOTIC FRUSTRATION LOOKS LIKE.

Mabuchi 700 series motor bolt circle: 2x M4 on 29mm

AXi 4120 bolt circle: 4x M4 on….

30mm.

Look at us, we’re so brushless we need to be just different enough to piss everyone off.

Luckily, “drill out the mounting holes 0.5mm larger each” was enough and the M4 cap screws just barely slipped into the existing counterbores.

To mount the pinion, I borrowed a 0.2357″ (6mm minus 0.0005″, because what are units?) reamer from Jamison and expanded the 5mm bore with it, then pressed the pinion on. This fit is backed up with green Loctite 609 retaining compound. It mildly makes me worry, bu Jamison swears it works… alright, we’ll find out. I’d personally have gone  -0.001″.

Here are the two completed P60 & Axi sandwiches ready to mount in the bot. This setup weighed 19oz each, down from 34oz of the P80 combos, putting the bot at still a half pound overweight.

With the motors now secure, I returned to the parts of the bot I stopped caring about before Dragon Con – namely, the electronics mounting. I first cooked up this DLUX 160 bracket in Atlanta and tried 3D printing a version. It worked fine, except there was not really a way to retain the top one since the gap now crossed by the N shape was open. I closed the gap using the diagonal brace that acts a little bit like a flexure spring.

Now the DLUX controllers take some effort to push in, which is great, since they won’t easily slide around.

The bracket attaches to the bottom of the bot with four #4-40 screws.

Next up? Battery tray. Clocker 3 just cinched the battery to the baseplate but I wanted something more constraining for the full contact 30lb class. Now the battery will sit in a 4-sided tray so it can’t move, and secured using nylon Velcro straps to that. The 4.4ah 7S lithium pack I had been using in Clocker was downsized to a 3.3Ah 6S pack to save more weight.

Clocker is known to work for exactly 1 match on a 2.3Ah battery thanks to FI 2015, and I originally used the 4.4Ah lipo packs because I had them and because Dragon Con matches tended to run back-to-back with minimal repair time.

The reason the tray looks oversized for that 3.3Ah battery is because it’s actually designed to house a row of A123 cells. The Franklin museum does not permit conventional Lithium batteries in anything above the 3lb class, since it’s entirely indoors in a museum and magic lithium smoke & fire cannot be tolerated. So, A123s it is. This means most bots run on reduced power for FI since you can’t fit as much battery into the same location using round cells as prismatic ones.

Pictured is 8 A123 cells. I plan on fitting as many cells in series as I have weight for at the end.

The final 3d printed bracket of convenience is the receiver and other electronics housing. This is taken care of by using the RageBridge lift & clamp controller as a cap! It’s a hollow case secured to the baseplate with more #4-40 screws, then the Rage comes in upside-down and is retained the same way.

After the New York Makre Faire, it’s time to perform the final fitting-out of the bot. Here’s everything being installed in place…

Another experiment I wanted to try in the interest of #season3 Overhaul was tilting the rubber shock mount wubbies to dig the front of the wedge into the ground. Since these wubbies were in a regular pattern, it was easy to put an equally regularly increasing spacer height under them progressively. For weight and lack of steel fender washer purposes, I made quick 3D-printed (this word….. I swear) spacers to test a few orientations. I think they’ll make it into the final assembly because nylon is still far more rigid than rubber – there’s actually no need for steel washers.

It’s coming down to the last three days before Franklin now, and I’ve started mass producing wheels and…………… set screws. I promised to bring a bag of them to the event to sprinkle into the arena. They’re 1.5″ diameter and 2″ tall, made of genuine organic Miku Blue PLA (get yours today!).

Wiring completion was fast, as more than half of was done in Atlanta. I just had to make a few more extensions and replace the 3mm bullet connectors on the AXi motors with 4mm ones. I decided to not make a switch panel for now, opting to just do it like most of my other smaller bots and just plug & unplug the battery cable.

Checking out the weight I had left over, I decided to run a 7S A123 pack instead. I weighed the bot with the FI-illegal lithium polymer battery to establish an upper limit, and then just added as many A123 cells as I could under that limit.

Now, look at that battery and tell me that you’d rather have that bullshit than a professionally made lithium cobalt battery!

And here it is! The finished Clocker 4, alongside a toy Overhaul for even more scaling fun.

But the story doesn’t stop there. At this point, the bot was still around 6 ounces overweight (with the FI-illegal battery, which is 2 ounces heavier than the 7S A123 pack). So I at minimum still had to cut off 4 ounces, preferably more.

I decided the best way to do this was to trim off the inside corners of the pontoons. They’re actually now shaped more like Overhaul’s. The flange on the interior only reaches back about 3/4″, which should be enough to still hide the edges from intruding weaponry. This actually removed about 3 ounces per side, putting me a healthy amount underweight.

Another funny robot exercise: Trimming the pontoon bottoms to be level and also riding flush with the ground. Just throw the whole thing on a belt grinder and have at it!

Just barely under now, with the 3.3Ah LiPo pack and all remaining hardware I could think of added, so I actually have a healthy margin for FI with the 7S A123 battery.

Here’s a test video of Clocker 4 playing with the (still working, just sans actuator) carcass of Clocker 3.

As I point out in the video, it’s way more stable when lifting than I anticipated. Clocker 3 is huge for a 30lber, and it just gets picked up and whammed around almost effortlessly. I was super happy with the speed of the lifter. While the clamp could be faster, the priority was on holding force for this edition with speed only coming from severely overvolting the clamp motor. Recall that the clamp motor is the same as what 12 O’Clocker used for drive this year – I just made sure to order a bunch of spare motors.

Time to pack it up. To come is the event report!

 

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    7 Responses to “Completing Überclocker 4 & The Leadup to Franklin Institute 2016”

    1. Matt Says:

      Does your MIT email still work?I sent you something about what specific A123 cells you were using, as I’m making a high school team and all the events near us are also no lipos.

    2. tician Says:

      The original A123 company was founded by MIT grads, so they gave MIT students/clubs many ‘not quite meeting the scary awesome spec’ 26650 cells and some other prototypes. A123-branded LiFePO4 cells can still be bought, but not always super easy to get.

      Hobbyking has a decent variety in pack sizes and ratings, and great prices if you can get them from a local warehouse. Lots of ‘power’ packs for high-C operation, but not quite A123-level of awesome.

      I’ve had decent experiences with batteryspace LiFePO4 cells, and they sell them in many sizes and ratings. Have a 4+ year old 4S 20Ah prismatic pack still running fine for powering a low-speed rover (<10A continuous for rover and small PC) and occasionally a Harbor Freight cordless reciprocating saw. One of two small 'energy' cells intended for a cheap, low-power LED flashlight was a dud, but too small and inexpensive to bother returning/replacing.

      Tenergy is okay for 'energy' cells, but not sure how well they handle higher discharge rates. Headway is another manufacturer, but they are geared toward larger cells for packs in e-bikes that are likely too big for a 30lbs bot.

      Also, YAY! for Mountain Dew PETE bottle shrink wrapped battery packs.

    3. the chuxxor Says:

      I can attest to most of those cells meeting the Scary Awesome Spec anyway…. and after 7 years (I was present for the grand reception in 2009), I can say we’ve finally gotten down to the last dozen boxes!

      I also agree with the assessment of Batteryspace cells. They are my go-to for industrial/commercial inquiries.

    4. Matt Says:

      for future reference, what email should i use?

    5. Matt Says:

      Also, the reason why I was wondering in particular which cells you were using is because all the cells I could find had a constant discharge of 30a tops, and I’m planning on doing 30a each side. on a 12lber.
      god what is wrong with me.
      also, It looks like we will be doing a similar track to testbot 4. look out for a spring flipper coming your way.

    6. the chuxxor Says:

      charlesg still works, in fact I probably got your email but I have a habit of going “I’ll answer this in a bit” and then forgetting about it >:T

    7. tician Says:

      Batteryspace currently has A123 26650 cells in stock for ~$14 each in small quantities (5~20) with tabs (http://www.batteryspace.com/A123-System-Nanophosphate-LiFePO4-26650-Rechargeable-Cell-3.2V-2500-mAh.aspx).

      buya123products.com has better prices ($9.25 each with further bulk savings), but located in Taiwan and shipping primarily to asia and pacific regions, so cost of US/Europe shipping will likely cancel any savings.

      I bought my first A123 cells several years ago from RCLipos (http://www.rclipos.com/A123_Cells.htm), but not sure they still actually have them in stock and the cells are more expensive than Batteryspace.

      I bought some 2S LiFePO4 20C ‘transmitter’ packs from Hobby King a few years ago to build 4S packs for a DARwIn-OP robot. The final configuration was a 4S 1.45Ah LiFePO4 pack instead of the default 3S 1.2Ah LiPo pack, but the 2S 2Ah LiFePO4 ‘transmitter’ packs that did not fit were rebuilt with 12AWG power leads and they work well with the Harbor Freight reciprocating saw when I don’t need the extended use provided by the Batteryspace 20Ah pack. So, Hobby King LiFePO4 ‘transmitter’ packs can be decent for power applications if you are willing to void the warranty and replace the tiny wires and connectors.