Tangled Marionette Mk2 Build Report

"Quidquid Latine Dictum Sit, Altum Viditur"
Translation: Anything said in latin sounds profound.

Since I had new ideas about something to build for the 2002 BotBash, I was originally hoping to just give Tangled Marionette a quick freshening and then get to building my new project ASAP. However, despite the fact that the Marionette was up and running, I knew it had several major issues:

  1. The setscrews holding the drive sprockets to the output shafts on the mk1 version kept coming loose under stress.
  2. The motor mounts could not keep the motor from rotating out under strain, thus loosening the chain and allowing the chain to skip.
  3. The drive pods (milled into extruded tubes of 6063 Aluminum) were extremely difficult to service since all the "fiddly bits" were down inside a tube space only 1-3/4" wide.
  4. Since the drivetrain was originally designed around a spinner, and then a lifter, it was not invertible.
  5. Most significantly: The drive pods were EXTREMELY twanged after several run-in's with the massive blade on Jerome Miles' "Hyper-Active" at BotBash 2001. There wasn't a square angle left anywhere.

    I did attempt to remedy the major issues using the old chassis rails, but issues with the motor mount to wheel spacing, etc. really complicated things. That said, a design tweak and complete re-machine were in order. So thus was born the Mark-2 iteration of Tangled Marionette.


    Here's my Team Raptor-style shot with all the machined components ready to be assembled. A few components were recycled from the Mk1 version: The motors and Vantec ESC, the Carbon Fiber top and bottom plates, the electronics box, the wheel-side sprockets, the chain, the shoulder-bolt axles, and the spikes appropriated from the defunct lifting apparatus. Everything else was machined from scratch.
    One of the big changes this year was that rather than hacking each of the drive tubes out of a single length of extruded tubing, they were a 4-piece assembly made from two lengths of extruded channel stock and two 6061 plates. This enhanced the ease of assembly and serviceability. Here you can see a partial assembly with the inside rail and the top plate. Next the outside rail and bottom plate would be added. Building the pod as a big "sandwich" was VASTLY easier than the elf-hands-required assembly I designed last year.
    Another shot shows the new nylon motor mounts with worm-gear clamps. Also, now the idler sprocket is moved to the inside rail (actually it threads into the nylon mount). Once again I can tension the chain by taking advantage of the off-center output shaft of the Pittman gearhead motors; rotating the motor in the mount changes the drive sprocket to idler spacing and tensions the chain. Also a big improvement from the Mk1 version: the drive sprockets are now pinned to the output shaft of the motor, rather than set screwed.
    Two assembled pods and the carbon fiber "belly pan". Unlike Mk1 that used angle brackets to affix the two pods via the front and rear panels, Mk2 was built as a "stressed skin" construction rather like a race car. The tension of the assembled top and bottom plates kept everything rigid. Without a top plate, the whole unit was VERY flexible. This was simpler to build (since I didn't have to fabricate a bunch of annoying angle brackets), but required more fasteners which lengthened the amount of time required to remove the top for servicing.
    A third transverse channel served as a mount for the vantec and power distribution, and further strengthened the chassis. You can also see the HDPE rear panel I'd hoped would be sufficiently radio-transparent to obsolete an external antenna. It wasn't. The new Titanium wedge is also barely visible on the right.
    Battery mounts got significantly simpler this time around. Slots milled in the inner drive rails served to pass through a pair of zip-ties. What's not obvious from the previous pictures is that the extruded channel tubes for the drive pods are also 1/2" shorter than the Mk1 version. (2.5" instead of 3"). Since I wasn't trying to squeeze a lifter motor or spinner into the design, I could push the "flat-as-a-pancake" envelope a bit.
    The backside of the 3rd crossmember served as power distribution and as a mount for the combination charging port and master-link. I took advantage of the interlocking nature of the anderson power poles to create a physically polarized 3-terminal connection that allowed me to connect a charger to the battery + and - terminals OR to connect a shorting link from battery+ to system power + to turn on the machine. There was a good chance my lovely wife would be operating Tangled Marionette this year so I wanted the system fool-proof to prevent the possibility of a Astroflight-Vantec interface from occurring. (a.k.a. a voltage to smoke converter).
    As with the Mk1 version, a single project box houses a Team Delta BEC and a micro receiver. In this case a Novak XXtra synthesized receiver gives me crystal-less access to the entire 75MHz band, which was handy when it came time to change channels. Paired with my new Hitec RCD Lynx 3D transmitter, I have 3 channels, and my wife found the pistol grip/steering wheel interface much more intuitive to drive than a single-stick aircraft style interface. Tank mixing was still done on EXP2 mode in the Vantec.
    I also recycled the nylon antenna mount from the Mk1 version. This mount could be attached to either the top or bottom plate, depending on whether I planned to run predominantly inverted, or right-side-up. (For example we ran inverted for the "KillBall" event to put the spikes into "ball handling" position.) Also, you can see the head of one of the 5/16" shoulder-bolt axles. These are great axles because they have a precision ground shaft and still have a threaded end for easy attachment with nylock nuts.
    Another enhancement this year was a Titanium wedge. I actually recycled this titanium from the shell of Robot-Wars veteran "Mortis". The Mortis team was finished with their carbon-kevlar composite and titanium shell after Battlebots Las Vegas in 2000, and didn't want to haul it back to England on the plane, so I scooped it up and its been sitting in my garage ever since. My wife was glad to see me finally make use of the material. Outside edges were cut with a shear in the shop at work, but the notches for the tubes had to be cut with an abrasive cutoff wheel. Standard stainless hinges, 10-32 button head cap screws and Nylock nuts complete the assembly.
    I got a lot of interest in the Vantec terminal block replacements that I used in the Mk1 version. Here's another shot of the terminal blocks with the wires coming into the top of the Vantec, rather than from the side. I have extras of these replacement blocks now so anyone who'd like to retrofit their Vantec should email me at herbie@puppetmaster-robotics.com for details and pricing.
    Did a much better job of coming in on-weight this year. The new chassis construction was only slightly heavier, due mainly to the extra fasteners. The big weight increase came from using 1" larger diameter colsons (for invertability) and the addition of the titanium wedge. All in all, it was a solid chassis package.
    Buttoned up and ready to rock at BotBash 2002. Here we're set up to run inverted which puts the spikes (under the black-bungeed "sharps" protection) in the up position, which was perfect for handling the "KillBall". We scored 3 or 4 goals, (I lost track) at least as many, if not more than, everyone else at the event.


    On to Event Report


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