I’m still waiting to jack someone’s Media Lab login. In the mean time, I’m wrapping up some loose ends. After all the waterjet-cut parts are done, the bot is only a few hours away from testing and tuning.

Finished master power switch assembly. The bot is off when a key of appropriate dimensions (read: stick of steel) is inserted into the slot, tripping the two normally-closed switched to be open circuit. The key is a good indicator that the bot is inactive. Additionally, the bot cannot be randomly shut off in battle by the switch, unlike removable links or normally open switches.

If TB does stop moving in a match, something else has gone horribly wrong. If it suddenly stops with no contact from the opponent, I’m probably half a second away from running through the arena walls with a fire extinguisher.

At the same MITERSing session, one of the guys there tack-welded the hinge seams. I decided against making this my first ever welding project since it was a relatively precise part that would take a while to redo if it got blown up.

In the end, the hinges are still going to be attached to soft, squishy plastic. The tack welds at least prevent the seam from unrolling. Welding the whole seam would have been unnecessarily risky.
Hey, it’s a sheet of blue spring steel. I got this .025″ thick strip after deciding that TB needed some more perimeter defense. There will probably be bot-sized strips waterjet-cut out and attached to the UHMW. The advantage of having an über-hard material on the bot is the reduced likelihood of a KE weapon digging in and tossing the bot. UHMW flakes away nicely enough, but if it can save me from some damage, it’s worth a shot.

This hard coating should be even more advantageous on the front wedge, which is a very low angled surface. I might look into making some shapes for that.

I also replaced all the wheels. Originally, it has just been one wheel, but that left the bot a bit uneven. So why not.

A function of the charger that I had never seen before. In between battery cycles, it allows you to set a delay before it moves on to the next step. In the programming section, this function is called “Waste Time“. Apparently, the physical manifestation of that is “Dry”. I assume it just got done washing.

Speaking of the charger, here’s the finished “integrated charging package”, which is really just the power supply bolted to the underside of the carrying case. Hey, it gets the job done. All the charging accessories go inside the carrying case, and I left a long enough lead from the PSU that the charger can be moved outside the case if needed. The metal frame elevates the case off the power supply surface by about 1/2″ to allow its cooling fan to function.

Test fitting all mechanical assemblies (minus arm) for the first time. There were some tight spots as usual, but a few minutes of running in and some drops of teflon-infused oil solved that. The drive wheel centers seem to be short by at most a hundredth of an inch, but it’s enough to get the belts a bit floppy. No slippage, but I might drop a roller tensioner or two on them anyway.

Oh, and the pink sharpie stains are fully visible on this side of the bot. The stuff seems to have embedded itself into the UHMW, and paint solvents only cleans most of it off.  Instead of making the whole bot pink, I’ll just leave it in the Random Sharpie color scheme.

So, now that the only thing left is hauling a 40 pound slab of aluminum (when it arrives) to the Media Lab and hoping the waterjet is open, there’s not really much more to report. Class begins next week, and Motorama is in 2 weeks! AHHHHHHHHHH! I still haven’t figured out how to get there yet.

Anyways, boto[x].

Yes, another one! I wonder how many build report posts I can rack up before the bot’s finally done.

Completed arm motor assembly. This is a stock drill motor with the casing removed and with a modified output shaft. The motor is a 540 size – slightly shorter than normal drill motors. With the intermittent duty cycle of the arm, I decided a shorter, overvolted motor would perform just as well. I had to file down the endcap of the 550 drill motor in MCE’s arm gearbox such that it would clear the drive belts. With this, I won’t have to do it.

Test mounting shows that most everything is where it needs to be. Unfortunately, while deepening the right arm rail hinge pin hole to allow the final assembly to sit at proper width, the UHMW managed to flex out of the clamp and get sucked into the drill bit, causing one hole to be drilled 5/16″ all the way through. This doesn’t impact the arm operation, but does lose me a fastener location.

UHMW has a propensity to suck itself into whatever cutting tool you’re using at the time unless it’s REALLY well secured.

Hinges drilled. You may notice that they are missing the pins. I intend to use some hardened 3/16″ steel rod as “pins” instead of the cheesy stuff that came with the hinge, which I could bend a 4 inch section thereof by hand. The hinge seams will also be tack-welded shut to use the extra strength. Also, I might incorporate “nutstrip” along the inside of the bot at the attachment points to lessen the likelihood of losing a wedge even more.

The almost-done frame for the überswitch. In MCE, this was a hack with some aluminum angle, washers, and spare standoffs. I’m giving the switch a proper frame in 1″ aluminum channel milled to the appropriate shape. The key slot hasn’t been made yet, because…

…I couldn’t  find a 1/8″ endmill.  There was a broken one, but that doesn’t count. I did find this tiny 2mm endmill that I briefly started using to cut the key slot before realizing that the machine can’t run anywhere close to the speed the cutter needs. Something like this needs 5 or 6000 RPM or more to properly use. I stopped before causing some damage or breaking the tool. MITERS has 1/8″ endmills for the Bridgeport, so I’ll swing by some time later.

A few days ago, I decided (after almost blowing up my 12v power supply from a dead short) that I really needed to integrate my new charger and its power supply into one unit, along with accessories, to prevent from having a clusterfuck of wires every time I need to charge a battery. The prototype was made from GIANT LAZER’D acrylic, but acrylic does not cold-bend and I couldn’t find a strip heater. So I used the prototype as a template to transfer the hole pattern onto some .1″ aluminum.

The sheet was then folded on the Media Lab sheet metal device. It’s only built for 20 gauge steel, and here I am trying to bend .1″ thick aluminum on it. It did NOT go smoothly. But in the end, what brute force I could dish out did work, and there were no heartstopping cracks or odd noises from the machine.

Test assembly. I’ll probably mount terminal strips, fans (the charger does get hot despite what its 40mm fan tries to do) and other accessories as necessary.

Great, now that almost everything else is done, I just NEED SOME TIME ON THAT WATERJET! I don’t have a ML network login and so can’t hop on and do it just any time. Fortunately, the nice folks as the ML are always willing to help out. We’ll see where this week leads.

Bot on!