Transactions of the Institution of Engineers in Scotland with Which Is Incorporated the Scottish Shipbuilders' Association Volume 10 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1867-01-01 Excerpt: ...now arises, what is the cause of these variations, and how on dynamic principles are they to be explained. The dynamics of the subject is indeed very simple, and can be easily reduced to a well known general problem. A simple pendulum when it vibrates through a very small arc, vibrates according to the law of simple harmonic motion. Take a spiral spring, with a heavy weight hanging by it, stretch it a little and let it go, and it vibrates according to the same law. The vibrations of a tuning fork, or any other instrument giving a similar musical sound, are also according to the law of simple harmonic motion. Another case of simple harmonic motion we have when the piston moves to and fro in a cylinder, the head of the piston rod being guided by a cross-head and slides, and the crank and fly-wheel making one revolution for every backward and forward movement of the piston. The balance-wheel of a watch, vibrating to and fro through a certain angle, is approximately a simple harmonic motion. The longer the hair spring is, the more nearly it will approach to simple harmonic motion, and it will keep time the more accurately. Now, against every change of motion of a body there is a certain reaction, and every motion to and fro of the balance-wheel of a watch or chronometer reacts upon the case of the watch or chronometer; and if the case is so suspended as to be free to vibrate, the motion of the balancewheel will generate a vibration of the whole, so that we have two motions to consider, --one, that of the balance-wheel, inside the watch; the other that of the whole watch except the balance-wheel. Upon the mode of suspension of the watch or chronometer will depend the nature of the vibration which it takes up and the resultant effect upon the rate The rate i..