Servo - April 2010

polycarbonate. Open the lid of the trunk and set the polycarb into the opening. I like to turn the trunk upside down with the lid resting on the ground and the main box supported with scrap lumber for this part. Now take your 2” x 3” piece of lumber and cut it to fit the inside of the lid. The polycarb should be sandwiched between the 2 x 3s and the inside of the lid (see Figure 3).

Run your wood screws through the lid into the 2 x 3 around the sides. I prefer to not run the screws through the polycarb as I prefer to not put any holes in it. When you drill plastics, you create micro-cracks which over time and impacts can grow to become bigger cracks. If you’re anything like me, you are very anti-crack. (Remember kids, cracks kill).

Test the Test

Functionally, the test box is now complete. You can throw your bot in there, drive it around, turn the weapon on, and everything will be hunky dorey. At this time though, you may notice something inherently annoying about your test box. By opening the lid to the complete open position, the test box will flop onto its back, and that’s just not cool. There is a simple fix for this problem. Take some of that string or lightweight chain you have laying around and create a leash on the outside of the box that limits the opening of the lid (see Figure 4). My test box allows motion to slightly beyond 90 degrees from the closed position. This allows the lid to stay open without my needing to hold it open, but it won’t tip over either.

Upgrades

Bling Bling. Here are a few ideas that I’ve had that could really make your test box the crème de la crème, so to speak. Remember earlier when I told you to pick up that MDF? This is where it can come in handy. If you’re worried about your bot getting through the plywood side walls, screw some MDF onto the outside of the test box. This will add weight, but for less than $20 a sheet, you can’t go wrong adding it.

Another upgrade you may want is new wheels — maybe even with spinners. Your test box, of course, will help you test your robots safely, but when you go to an event, you can use your test box to carry stuff. Bolt your test box to a two-wheel hand truck. Not only can you test your bot safely in the pits (get your frequency clip first), it will also save you trips from bringing your stuff in from the car. Nice. I didn’t have a hand truck, but I did have an old skateboard I bought at a yard sale. It doesn’t turn great, but I can ride my test box at the skate park.

You may also want to upgrade the floor of your test box with the

same floor as the arena you’ll be competing in. If the full size arena has seams, add a seam to your test box. Remember you’re testing, so you want to know how your robot will react to the conditions it will likely face in combat.

FIGURE 5. Completed test box with bot inside, ready to be tested.

Safety (Test) First

It has always surprised me how much people are willing to spend on a CNC titanium blade or custom turned bearing mounts for the bots, but those same spending habits don’t translate into safety equipment. This simple test box will last you through many bots. The low cost of the materials and short build time will make it well worth the investment the first time your bot behaves abnormally or something catastrophic fails, and the high speed shrapnel is contained. Remember, the controls are much easier to operate if you have all your fingers. SV

C mbat Zone’s Greatest Hits This month, CZ is experimenting with a new feature. We all know that creating bots is a fulfilling mental exercise, building them is satisfying craftsmanship, and going to events is great for bonding with your buds. But let’s face it — it’s about the

● by Kevin Berry

destruction! The audience doesn’t cheer for box vs. wedge fests. It’s the sparks, tosses, and large, flying chunks that get that “ohhhhh!” sound bouncing around the venue.