Motors

Electric motors are just about the easiest way to generate reliable motion. They can be purchased at hobby stores and found in many devices.

Hydraulics

Hydraulics is the transmission of force via fluid pressure from one place to another. If two syringes are connected by a tube and are filled with a liquid, the position of one plunger affects that of the other and it is an example of hydraulics.

Pneumatics

Pneumatics is the transmission of force via air pressure from one place to another. If two syringes are connected by a tube filled with air, the position of one plunger affects that of the other and it is an example of pneumatics. Actuating a piston with air also counts.

Fans

Fans can be used to mechanically blow objects or to heat/cool objects using the supplied air. There are a wide variety of fans that can be used for different events, such as MagLev, but some fans are not legal, depending on the allowed electronics.

Solenoids

Solenoids are electromagnetic coils that, when powered, retract or extend a metallic rod. Solenoids vary by power usage, travel distance, travel direction, and whether they are spring return or not.

Springs

Springs come in a variety of shapes, the most common of which are compression, tension, and torsion. Depending on what you want to do, you will have to choose which is best.

Mousetraps

Some years mousetraps are mandated to be included by some task in the rules, otherwise avoid them whenever possible. They are finicky and unreliable, but useful if you have nothing else.

Timing

Sand/Liquid Timer

This is not limited to sand. Anything that will flow evenly can be used. The idea is simply that a certain amount has to flow through the orifice before the counterweight on a lever or some such device will be overcome. The timing can be adjusted by adding or subtracting small increments on the counterweight.

Threaded Rod

Perhaps the ultimate timing mechanism is the threaded rod. Using the same principle that the vehicle building events use to create braking systems, a nut travels down a threaded rod until it comes into contact with a switch or pushes some object. Timing can be adjusted precisely by the starting and ending locations of the nut.

Wound Rod

This is the poor man's threaded rod. Using nothing but a dowel rod (or any other round shaft), thick wire or rope or something is wrapped in a helix down the rod. This creates an equivalent to the threaded rod for a ball bearing or marble to travel down. It is less precise, but can be made at no cost.