Servo - March 2010

robots under covers. People were proudly showing their bots in detail, and many teams were helping each other fix their robots. This was uncommon before 2006. I also believe the tutorial helped to increase the number of Brazilian teams who compete, not only due to the technical tips, but also due to the description of our wonderful experiences at RoboGames. Finally, the fact that we won both a gold and bronze medal in

2006 also had a great impact. It showed other teams that it was possible for a Brazilian robot to win, even in such a tough event.

RoboGames also had an influence on the number of categories in Brazilian hosted events. Since our attendance at RoboGames, we added hobbyweight combat in 2007, featherweight combat in 2008, and then followed by 3 kg Sumo and hockey in 2009.

Since 2006, we’ve attended RoboGames every year. For RoboGames 2007, we increased the speed of Touro’s drum. We needed that extra energy against the increasingly well armored bots. The width of the S7 drum teeth was increased from 3/4” to 1” to take all the impact energy. All hex screws were changed to flat or round head, so they wouldn’t be torn off. We also built our first lightweight — Touro Light (Figure 5) — using the same idea as Touro. Figure 6 shows one of our most exciting matches — Touro against Sub Zero. In only our second year at RoboGames, we went undefeated in both middle and light classes to win two gold medals. It was a wonderful experience!

Even though our robots didn’t break, we’ve learned a lot from the fights. We had to change Touro Light’s drive motors after every match — using only two 775 motors was not enough for a lightweight. After facing Pipe Wench, we realized that it would be good for Touro if its drum was reversible, to effectively work even when flipped over.

We also realized that our robot’s ground clearance was too low, since it got stuck quite often. In Brazil, our arena does not have to take the punishment of heavy or super-heavy bots, so its floor is very smooth (with seams no greater than 1 mm). If you have a match right after The Judge or Megabyte, several seams may have opened up. We’ve realized that the bot has to adapt to the arena, and not the other way around.

For RoboGames 2008, we decreased the thickness of Touro’s top and bottom plates to gain a little ground clearance. This didn’t solve the problem, but it did help a little bit. Touro’s drum became reversible after changing the weapon solenoid to a pair of Victor speed controllers. Touro Light’s drive motor was changed to an 18V De Walt. This led to the birth of our first featherweight: Touro Feather.

Touro was doing well until it got defeated twice by the vertical spinner Professor Chaos. One of our main problems was our 1” wide tooth which did not withstand a weapon-to-weapon hit while Touro was flipped over. Touro Light

Figure 7. Touro vs. Mortician 2009.

(Photo by Brian Benson)

didn’t do well either – its planetary gearboxes didn’t take the higher power from the 18V De Walt, shearing the pins from the last stage in two different matches. Touro Feather had a very powerful brushless motor spinning the drum, however, the drum’s v-belts were too rigid which prevented the brushless motors from spinning up sometimes. The low starting torque of brushless motors can be a problem if the BESC (brushless electronic speed controller) is not well programmed.

In 2009, I released the English version of the RioBotz Tutorial. I had learned so much at the RoboGames 2007 and 2008 events – both from other builders and from broken parts – that the tutorial doubled in size, reaching 380 pages. You learn a lot from these types of events. It’s like drinking water from a fire hose sometimes, so be ready to take several pictures and notes.

For RoboGames 2009, we increased Touro’s S7 drum tooth width to 1.5”, using a new drum with a higher moment of inertia. Both Touro and Touro Light’s drums featured a single S7 tooth, balanced by a tungsten counterweight flush with the drum. Touro Light’s drivetrain was upgraded to a pair of De Walt power drives. Touro