What is Big Trak? Big Trak is computer controlled tank. In other words, a robotic tank! I still have mine, and its Transporter too. It is great fun to see what I can make Big Trak do, even 30 years or so later. I would really like to build a high-quality Big Trak equivalent as a robot test bed for other projects.
I've also moved my other robotics info here, Big Trak is the only robot I really have for now.
Big Trak a 6 wheel computer controlled robot tank. There are 6 wheels, 3 on each side. Of the 3, the center one on each side is the drive wheel. The rear wheels are fixed suspension, and the front wheel articulates up/down as a suspension / stabilization mechanism. The left and right drive trains are separate from each other.
How does Big Trak turn? Just like a real tank does! Big Trak and larger tanks use a technique called skid-steering, where the wheels on one side drive forward, and the wheels on the other side drive backwards to spin the tank in its place. More sophisticated setups are possible, where you spin one side and don't drive the other side. Or, even drive the two sides at different speeds for more gradual and precise control.
The Big Trak has one "weapon" a photon canon. [Un]Fortunately it will not photonize your brothers and sisters. The photon canon is really a light bulb, and a speaker for the awesome sound-effects of firing.
Big Trak has one accessory, the Big Trak Transporter. The Transporter is a four-wheeled trailer which the Big Trak pulls via a 5th wheel hitch. The Transporter can empty (as a dump truck) its load via program control. The setup is quite manueverable, ant it isn't too difficult to even program Big Trak to drive the Transporter around a corner -- Backwards!
Big Trak has some nicely done implementation details. Each drive wheel has an optical encoder in the final drive segment so that it can tell how far it has travelled. The distances aren't perfect, and different floors have different slippage amounts. However, it isn't a total no-feedback spray-n-pray drive control.
The other cool feature of Big Trak is a magnetic clutch in the drive train. This helps to keep Big Trak actually moving in a straight line during the theoretical straight forward and reverse segments of travel. How this works is that the L and R drive trains are independent of each other. However, one of the drive wheel and its mate in the opposite train have magnets of opposite polarity. When Big Trak is turning these magnets rotate in opposite directions past each other and nothing happens. However, if Big Trak is moving in a straight line, the two magnets are close to each other. The pair of magnets then "grab" each other's fields and there by synchronize movement of the independent left and right drive-trains!
See my Radio Control Info for descriptions of how RC servos (often used in robots) work, and what you need to do to drive them.
Perhaps Toys isn't the right word, for many of these are far more than just a toy. Educational supply places often have many components that can be used for fun or projects, or for prototyping before building. For example, components such as multi-range planetary gearboxes, marble tracks, rolling ball items, robot components, etc.