Tag: motorama

Waterjet cutters are your friend.

chorl

Radical pseudo-environmentalists are not. THANK YOU. OH MY GOD. Finally someone condenses everything that is wrong with the modern Green movement and the general feel-good-do-nothing consciousness in those circles that is actually DETRIMENTAL to progress and helping “the environment”. I hate that word, but it’s useful some times for what it describes. Oh, and the 200+ comments are also insightful in themselves.

Anyways, onto the TB report. I finally got some time on the God machine today and cut out most of the parts that still need to be finished. The aluminum plate I ordered hasn’t arrived yet, so I borrowed a plate of 1/2″ aluminum for the purpose of getting the arm together. It might also function as a backup and spare parts.

Washing away the tons of abrasive sludge covering the aluminum plate after cutting. These are the arm sections.

I also cut the garolite top and bottom plates on the WJ. Although the holes and slots are consistently placed, the garo did suffer from a case of “Waterjet-induced Delamination Syndrome”. Garo is made from pressing multiple layers of fiberglass together with an epoxy resin, and that can let loose when a few KSI of water suddenly forces itself within the layers. I think this can be resolved by injecting some epoxy or CA glue (or even epoxy softener/acrylic solvent) and then clamping for a while, but it seems like abrasive particles have been trapped under the layers as well. That would be a bitch to get out. I might just leave them stuck in there forever.

One arm section retrieved. Even with no draft compensation (tilting head), it did extremely well on “uber-fine sandpaper’d baby’s bottom” quality. These pieces do need some post-processing in the form of channels milled, holes drilled and tapped, and bushings mounted. I’ll attend to that over the course of the week.\

The arm links themselves are composed of multiple pieces screwed and pinned together. Notice the little tabs connecting each part. They are there to prevent the parts from falling into the waterjet tank, never to be seen again. With the tabs, I can lift all the links out as one piece, break them apart, and sand the tabs off. A small time penalty for alot of insurance.

Some schnazzy side armor plates. Now I cannot lose.

Another weird waterjet artifact, this time on the rear armor plate. For some reason, the course-programming software insisted on piercing all holes except one in a part, then cutting the profile, then going back and doing that last hole. What does this mean? Loose floppy part gets punched by a 40KSI column of water and jumps all over the place. On a hard material such as spring steel, this resulted in an odd pattern in the part. The end result was that I had to go and tweak the program in that one portion only for the rest of the parts.

I don’t have another sheet of spring steel handy, so might just drill (punch? dremel? chisel? What the hell can I do with hardened spring steel!?) mounting holes in an adjacent location.

Hey, it’s the bot. Sort of. At least the internals are enclosed on all sides now. At this point, I just need to make the wedges and perform the appropriate finishing jobs on all components. I can probably throw together the electronics in one evening.

IT’S GETTING CLOSE! Yeah, Moto is. Now less than TWO WEEKS! Things have to get moving soon… including me, since classes start Tuesday.

TB4.5MCESP1 Update 13

chorl2 Comments

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].