This larger version of the Drogerdy Tank Bot is designed as a base robotics platform for my students to use in their own robotics projects. It features a large component box, mounting area for sensors at both ends, provision for 5mm LED head and tail lights, provision for a photo-gate to measure cog RPM.This bot I designed so that my students have a solid platform on which to based their robotics projects on. Once again you will need these motors to get this going: http://www.ebay.com.au/itm/5pcs-Lot-TT-Motor-Gear-Motor-for-ARDUINO-Smart-Car-Robot-/181628767023?pt=LH_DefaultDomain_15&hash=item2a49eb0b2f I just searched "Robot Motor" on EBay and heaps come up. I run them at 9Volts Max (pref 7.2V)- at 12 volts, if the tracks get stuck, the motor will have enough torque to chew out its own spindle. For each track assembly you will need: 1 x outer frame 1 x inner frame 2 x main cogs 4 x small cogs 31 x tracks 31 x pins Print the tracks with 100% fill. Print the pins laying on their sides on a raft. Print the body section sideways with break-away supports Each main cog has 5mm holes that go right through the frame to allow for a photo-gate which will allow your bot to at the very least know the motor RPM. Construct a photo-gate for the cog that does not have the engine. With this info you should be able to ensure that both tracks move at the same speed. Without this your bot will arc to one side, especially when going across a slope. There are 5mm holes for LEDs at both ends of the track assembly which gives your bot that "hey look at me" factor. Other than that, the bot designed to be very adaptable. Enjoy!