Gears are generally used for one of four different reasons:
The fact that one gear is spinning twice as fast as the other is because of the ratio between the gears -- the gear ratio. In this figure, the diameter of the gear on the left is twice that of the gear on the right. The gear ratio is therefore 2:1 (pronounced "two to one"). If you watch the figure, you can see the ratio: Every time the larger gear goes around once, the smaller gear goes around twice. If both gears had the same diameter, they would rotate at the same speed but in opposite directions.
Imagine the following situation: You have two red gears that you want to keep synchronized, but they are some distance apart. You can place a big gear between them if you want them to have the same direction of rotation:
Or you can use two equal-sized gears if you want them to have opposite directions of rotation:
However, in both of these cases the extra gears are likely to be heavy and you need to create axles for them. In these cases, the common solution is to use either a chain or a toothed belt, as shown here:
The advantages of chains and belts are light weight, the ability to separate the two gears by some distance, and the ability to connect many gears together on the same chain or belt.
Example 1 Example 2 Example 3
An automaton is a general term for any formal model of computation. Typically, an automaton is represented as a state machine. That is, it consists of a set of states, a set of transitions from state to state, a set of starting states, a set of acceptable terminating states, and an input string. A state transition usually has some rules associated with it that govern when the transition may occur, and are able to remove symbols from the input string. An automaton may even have some sort of data structure associated with it, besides the input string, with which it may interact.
Automaton Chess Player, 1770
Wolfgang von Kempelen’s mechanical chess player was one of the most famous automata of all time. The automaton, produced in 1770, bested a host of chess experts, European royals, and celebrities in live chess matches. The automaton chess player fascinated the public because it not only imitated human behavior, it appeared to be a “thinking machine.” German inventor and showman Johann Maelzel brought the device to the U.S. in 1826, where it sparked heated debates among audiences and journalists about the mystery of its operation (an 1837 newspaper expose revealed the presence of an assistant concealed inside the cabinet). Barnum claimed that Malezel—through his use of the press to inspire public conversation about the attraction’s relative authenticity and deception—influenced his own career as a showman. A fire at the Chinese Museum in Philadelphia in 1854 destroyed the automaton chess player.
Tik-Tok is a fictional character from the Oz books by L. Frank Baum. He is one of the earlier robots to appear in literature, though that term was coined after Baum's death.
Tik-Tok is a mechanical man that runs on clockwork springs which periodically need to be wound, like a wind-up toy or mechanical clock. He has separate windings for thought, action, and speech. Tik-Tok is unable to wind any of them up himself.