Robotics
How to build a Battlebot without a machine shop.
It wasn't the first time I had seen Battlebots, but when I really paid attention, my enthusiasm really took off. I got on the web and looked up the Battlebots.com website and learned of the rules. Then I found a bunch of web pages put up by robot builders. The contestants that were on TV were dispensing all kinds of advice on how to build your own Battlebot. I went to the nearby Toys 'R Us store and bought a Tyco Super Rebound R/C car. After a few days taking it apart and putting it back together, I began to plan my own Battlebot. Christian Carlberg's website at www.coolrobots.com was very valuable in helping with basic details. Experience with the Tyco car and watching Battlebots and Robotica told me that a four-wheeled, tank type drive system was best. Soon I was ordering a RC radio from www.towerhobbies.com and scouting out hardware stores for parts. I first bought a blender for $18 before I learned that AC and DC motors don't mix. Then I saw an ad for Homier Distributing Corp's tool sale. They had 18V cordless drills complete with charger and battery for $30 each. My design initially had four wheels driven by two motors, but chain and sprocket systems seemed too complicated, so I went with a four-engine direct drive system. Besides, isn't four-wheel drive better? I bought some more of the same drills off Homier's website www.homier.com. At Radio Shack I got a fuse block with 15 amp fuses, a power switch, a wire stripper/cutter and a multimeter. At Home Depot and at Lowe's I stocked up on red and black 14 AWG wire, crimping disconnects, wire nut connectors, 3/8" particle board, angle braces, and a bunch of #8 32-3/4" machine screws. I bought two RCE225 relay switches from www.teamdelta.com with the intent to try them as a rudimentary speed controller.
I started drilling the particle board and fastening angle braces to hold my batteries. Next the switch, fuse block, and relay switches were attached. Following Carlberg's instructions I wired it all together with two of the drill motors and to my surprise, it all worked with the remote control. Unfortunately, I dropped a wire during the wiring process and it fell on the one place on the board that would complete a short circuit of my battery. The batteries sparked for about two whole seconds during which time I think the light in the switch burned out and the battery terminals got oxidized. There didn't seem to be any permanent damage, though. Even the switch still worked sans light.
Next came the hard part. How do I attach the motors to the chassis and the wheels to the motor? I tried looking at local machine shops for an estimate of something that would hold my motors securely to my chassis. One shop ignored me and another quoted me $125 for each motor mount. So I went back to the almost discarded drill casings, sawed off the top part that originally held the drill motor and attached them to my chassis. For wheels, a friend named Derek suggested using hole saws for wheels. At first I resisted the idea, but after consideration of the benefits of having wheels as weapons and finding some recommendations on vacuum cleaner belts at www.infernolab.com, I decided to go with the hole saws. Again, I benefited from a tool sale and picked up four hole saw kits complete with mandrils for $6.50 each at Harbor Freight Tools. At this point, I had to dismantle everything from my first build to put it on a larger board. Poor planning, but now I get to take it apart. My first robotics injury was scraping off some skin trying to pry apart the wire connectors with a screwdriver.
Putting it all back together went pretty quickly. I attached the third and fourth motors, installed the hole saws, and tested the electronics again to make sure they survived the relocation. Still operational. So I tried the whole mess on the ground. Here, I learned first hand why everyone recommends a speed controller. The relay switches only allowed the drills to reach their maximum speed immediately, causing the wheels to spin out all the time. I hadn't used the vacuum belts yet, but I could tell that this jumpy thing just wouldn't steer well.
So I ordered an RDFR23 from Vantec (www.vantec.com). They were backlogged so I had to wait more than a month. I got the RDFR23 because my batteries fully charged are close to 20 volts and I wanted the eventual possibility of moving up to middleweight class. Until the speed controller comes, I need to figure out how to drill holes in the hole saws to attach the vacuum belts. I also need to think more about the body armor and weapons platform. My daughter gave me some pointers.
Here's a breakdown of the cost of materials (tools not included):
| Vantec RDFR23 Speed Controller | $350.00 |
| Futaba 6XAS Radio, Receiver, Servos, Battery, Charger | $225.00 |
| Homier Drill Motors, Batteries, and Rechargersx6 | $200.00 |
| Team Delta RCE225 Relay Switchesx2 | $80.00 |
| Black & Decker Cordless Saw | $54.00 |
| Hole Saws, 5 in diameterx4 | $28.00 |
| Futaba J Servo Extensions | $13.00 |
| Machine Screws | $9.00 |
| Particle Boards | $8.00 |
| Vacuum Belts, V1091x4 | $7.00 |
| 14 AWG Connectors, Box of 50 | $7.00 |
| 14 AWG Wiring | $5.00 |
| Wire Connectors, 4 Boxes of 6 | $4.00 |
| Angle Brackets | $4.00 |
| Fuses & Fuseblock | $4.00 |
| Rocker Switch | $3.00 |
| Duct Tape | $3.00 |
Total cost so far: $1004