Wednesday, March 18, 2015

Battle Bots, Part 2!!

Better late then never!!

So, the two weeks leading up to Motorama was a hectic time with the Boston weather making the trip to MITERS more of the trek than normal. No bike and flaky T service makes for a long (cold) haul home in the evenings. Traveling for work also limited my time.

Anyway, back to robots! After breaking the old armor I rolled back the design iterations to make the armor piece with a solid base plate. I'd initially planned to use steel (heavy)for the armor but since I was using aluminium, I could use more adn thus make the the armor and base piece one single piece.

This part was cut in the IDC on the ShopBot as before. The piece was annealed and all the bends were made with the DIY die press I made. Fixtures from some crufed lab equipment had a nice long 90 degree channel at 45 degrees. This piece was placed on the bed of the small arbor press while an short section of square Al stock had a slot milled in it across the diagonal to fit snugly onto the shaft of the arbor press. The die press worked an absolute charm, giving very clean bend lines and a great deal of control over the final bend angle.

The front flipper is mounted to a support rib that also braced the Al armor. My first iteration suffered skewed holes thanks to me forgetting that the drill chuck is significantly greater than the diameter of the drill bit..oops. I remade this piece with a removable flipper mount so that the it could be drilled out correctly then installed in the rib. This worked a charm in the end. The flipper itself consists of two pieces, a spring steel plate with a lip mounded onto a .25"Al plate which connects to the rib and the drive servo. Stainless steel pins were used in in the hinges and secured by over shadowing the holes with button head screws. The spring steel was first annealed where it needed to be bent till it was cherry red, and was kept there for a few minutes to make sure it was annealed fully. I bent the lip using a vice. The steel was bolted onto the Al with a handful of M3 button heads.

With the front rib complete, I could begin the process of securing the battery. The battery was secured against on of the motor supports with a block of delrin and bounded vertically by the front rib. The flipper drive servo is also mounted to the base with two small delrin blocks. The linkage arm from the servo is simply a short piece of Al.

The initial plan was to make a sort of composite armor with some water jetted spring steel plates epoxied to the Al frame. Due to a series of calamitous events, the waterjets that we'd access around the MIT campus were all down the weekend before Motorama and part of that last week.Cue a new solution. I knew Charles had made Colsonbot and after Jamo showed me a few video's from lasts years Moto, I reckoned encasing the bot in some colsons would dramatically increase the survivability of the bot. Since we didn't happen to have an 8" colson on hand, I butchered a 6" colson to make 4 bumpers that would absorb/divert any impacts. The thickness of the colsons also meant that they served double duty by protecting the wheels. To mount the colsons to the Al, three self tapping torx screws were driven into each bumper after a liberal coating of E600 was applied to both contacting surfaces.

The last thing to do was to fit the top armor to the bot along with the rear rib. This took a bit of tweaking with the benchtop sander to get things just right. After the final assembly I weighed the bot. 1382g. So around 20g over the limit (1362g). Pretty damn good for just winging the whole armor but. The final Solidworks weight was around 900g. The rear rib was made of 3/8" Al since it's what I grabbed first. Taking this down to .25" with the mill knocked off around 50g since the final weight was 1330g.

I should probably point out that I finished the bot around 2 hours before our scheduled departure time, so I'll count that as an finishing early..... Once i was all packed and ready to go, I went upstairs to help Dane and Bercu with their bot.

Yeah yeah, I'll add pics soon. Due to the time press, I got super lazy about photographing some of the construction phases.