How do clocks work?
Clocks are generally powered in one of six ways: weight-driven, spring-driven, atmospheric, battery-operated or electric. Weight-driven, spring-driven and atmospheric clocks have mechanical movements and will be discussed first.
Weight-driven clocks are mechanical timepieces that are powered by the gravitational pull of heavy weights slowly falling down. The gravitational pull generally lasts for up to seven days, at which time the weights need to be pulled back up. The weights hang on either cables or chains and are pulled up by either winding the cables up with a crank that gets inserted into the holes on the front of the dial or by manually pulling up the chains. Most weight-driven clocks will also produce a chime. The example of a grandfather clock below illustrates this type of weight-driven movement with chimes.
The patriarch of clocks, the grandfather, are mostly weight-driven, mechanical clocks which are encased in a tall, wooden cabinet that acts as an echo chamber for a cathedral chime melody or other classic clock chimes. As the hand advances, the minute hand trips a star gear located on the center stem of the dial face. The point of the star gear lifts a pin that triggers the turning of the music roll (just as you would find in a music box).
As the music roll turns, it pulls back a chime hammer, which then falls back to its original position and strikes a chime rod, or in some cases a steel tuned tube. Most chiming, weight-driven, mechanical grandfather clocks have 12 hammers and rods. Yet a few select models have 16 hammers and rods. Still further, a very select few models have 5-9 hammers with steel tuned tubes. Mechanical wall and mantel clocks may only have 8 hammers in their triple chime movements and may also only have 5 hammers for their Westminster only movements. The chime rods, or in some cases steel tuned tubes, are cut at various lengths to produce different notes. These hammers and rods, struck in various orders, will produce the selected chime. Grandfather clocks with 12 hammers and rods will generally produce either the single Westminster melody or the selected triple chime cathedral melody of Westminster, Whittington or St. Michael's. Grandfather clocks with 16 hammers will generally feature the triple chime of Westminster, Shubert's "Ave Maria" and Beethoven's Ninth Symphony "Ode to Joy.