Trains
Several pairs in series
A single worm pair can give a large ratio on its own. If the shafts must be parallel, it may take a train.
For a large speed ratio in a single gear pair, a worm and gear are well suited. Britannica Scholars: gear If the shafts must be parallel, it may be necessary to use several gear pairs in series (a train) to obtain a large ratio. Britannica Scholars: gear
The wheelwork, or train, of a clock is the series of moving wheels (gears) that transmit motion from a weight or spring, via the escapement, to the minute and hour hands. Britannica Scholars: clock
A pinion is a gear with a small number of teeth designed to mesh with a larger wheel. Britannica Scholars: clock An arbor is a turning rod to which gears are attached. Britannica Scholars: clock
A clock train is worked through, gently, on the clocks page, and in more depth on clockwork.mechanics.im.