Parts:

• Two HS-475HB or Better Servos
  • Modified for continuous rotation
• Four Hockey Pucks
• Toy Tank
  • Needs the track, also small idler wheel
  • You can look around for it, normally from a toy tank found in radioshack, you can make your own from a length of rubber or similar
  • I only used this because I had it for free, be creative
• Four Identical Gears
  • 1" Diameter is Perfect
• 1/8" Thick Plastic Sheet
• Coat Hanger
• Hardware
  • 1/4" Diameter 2" Long Bolts, four of them
  • Bag full of washers and nuts for all of these

Tools:

• Dremel
• Drill with "doorknob hole" cutting saw

Construction:

Detailed diagrams and instructions will be included detailing the modification of the hockey pucks into pulley wheels, the installation of the tracks, and the gears joining the servos to the wheels.