Servo - March 2010

FIGURE 8

The competition I built Hot Stuff for would have matches that lasted three minutes long or until one of the robots got knocked out (whichever happened first). Balancing battery power can be tricky because if your battery is too small, then you risk running out of juice before the fight is over. If your battery is too big, then you are just packing around extra weight you could be using somewhere else. Figure 8 shows me making a battery pack housing that will space the cells apart to keep them cooler.

Heat is an enemy to anything electrical; in battery packs, extra heat can cause the packs to run less efficient and run out of juice faster. To combat heat, I built cell spacers out of polycarbonate to keep each Sub C cell an 1/8 inch from one another. I used Sanyo 2400 Sub C sized Nickel Cadium battery cells to power Hot Stuff because they are

FIGURE 11

FIGURE 14

28 SERVO 03.2010

FIGURE 9 FIGURE 10

lightweight, can source a lot of power, and they can be charged right in the robot. Figure 9 shows the two battery packs finished and ready to go in the robot.

Instead of rambling about how I mounted all the internal parts by bending this little piece of metal here or welded that tab there, I’ll just show you the photo with most of the internals mounted (Figure 10). I’m using a paintball tank that holds nine ounces of CO2 to power the lifting arm. I run the CO2 through a regulator that takes the 900 or so PSI (pounds per square inch) of pressure that’s in the bottle and lowers it to 150 PSI.

There are two air cylinders in the robot: a larger one to run the lifting part of the arm and a smaller one to run the grabbing part. Each air cylinder is run by a valve hooked to an R/C switch so I can control it with a radio transmitter designed for R/C airplanes.

In Figure 11, you can see the robot stripped down to just the frame. I hung it from my robot lab rafters (Okay, okay, my garage rafters) with a little piece of wire and hit it with some red spray paint. This part of the robot ended up only weighing 13 pounds — not to bad!

This was definitely going to be a very animated robot because every channel on the radio receiver was full (see Figure 12)! It was actually a really big pain to get all the plugs to plug in at the same time. (I guess the manufacturer figured they would never all be used at once.)

I started putting the robot back together after the paint dried. I used some black spray paint on the drive pods (I really liked how it all came out). In Figure 13, you can see I started to wire up the speed controller. This is one of the most important parts of a fighting