Types of train clocks, or spring-driven mantel clocks, include those that show time only; those that show time and strike on the hour; and those that show time, strike and chime. A train is a set of gears, or wheels, that create movement in the clock. One train is needed for each function. Each needs periodic winding, with most models able to run for eight days straight.
The time-only clock has a single train that controls the hands of the clock. It only has one winding hole where a special key is inserted to turn the gears. Most clocks wind in a clockwise direction, and the gears become harder to turn as they get close to being fully wound.
The time-and-strike clocks have two trains, one to work the time movement and the other to trigger the strike. Some strike clocks give a single strike on the half hour in addition to the longer strike on the hour. These clocks have two winding holes.
Chiming clocks typically have three trains and either two or three winding holes. These chime a tune on the quarter-hours. Though the Westminster chimes melody is the most common tune, some clocks play multiple chimes. The full tune is played on the hour, and only part of it on the half- and quarter-hours.
Train clocks use either a pendulum or a balance wheel to keep time and must be perfectly level to do so. Some clocks have a built-in level, while on others the balancing is done by trial and error. If a clock is level, the tick-tock sound is even, or "in beat."