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KF5JRV > TECH 08.05.22 12:38l 14 Lines 3711 Bytes #999 (0) @ WW
BID : 33642_KF5JRV
Read: GUEST
Subj: Shortt Clock
Path: IW8PGT<I3XTY<GB7COW<GB7YEW<VA7RBP<KF5JRV
Sent: 220508/1035Z 33642@KF5JRV.#NWAR.AR.USA.NA BPQ6.0.19
The Shortt clock is a precision pendulum clock that was developed in 1921 by the English engineer William Hamilton Shortt (1881–1971).
The peculiarity of the Shortt clocks is that they are largely free of atmospheric disturbances and disturbances due to friction. This is achieved by separating the master and slave clock. In the master clock, an almost free pendulum swings in an evacuated housing. A second pendulum clock synchronized with the master clock contains all other moving parts whose mechanical and other malfunctions could affect the master clock. The rate error of this almost friction-free construction is a few milliseconds per day, which was only exceeded by temperature-stabilized quartz watches.
The Shortt clock has two pendulums. The main pendulum swings largely freely in a container with reduced air pressure and receives a mechanical impulse every 30 seconds to maintain the oscillation. The secondary pendulum is located in a modified synchronome clock. As with all synchronome clocks, the pendulum moves a 15-tooth counting wheel via a pawl by one tooth per swing of the pendulum. When the counting wheel is fully rotated after 30 seconds, a gravity lever is triggered, which sits on a curved plane on the secondary pendulum and, when it rolls, gives the secondary pendulum new kinetic energy for the following 30 seconds. An electrical contact located on the gravity lever is then closed. The closed circuit magnetizes an electromagnet , which brings the gravity lever back to its starting position and opens the electrical contact. The daughter clocks that are in series are also moved forward by half a minute via this circuit. The circuit also releases a second gravity lever, which is attached to the main pendulum and gives the main pendulum its drive impulse. This is accomplished by the second gravity lever completely smoothly seated on a located on the main pendulum roller and the main shuttle issues a low driving in the low-traps always in the same oscillation phase. The gravity lever triggers a contact - always in the same pendulum phase - which closes a second electrical circuit. This brings the gravity lever of the main pendulum back to its original position and at the same time activates a synchronization device on the modified synchronome clock. A leaf spring located on the secondary pendulum accelerates it slightly when the synchronization device is activated and the secondary pendulum is within the working range of the synchronization device. If, on the other hand, the secondary pendulum is synchronous with the main pendulum, the synchronization device misses the leaf spring and does not influence the secondary pendulum. If the secondary pendulum swings slightly more slowly than the main pendulum, the synchronization of both pendulums works without errors and the main pendulum determines the accuracy of the Shortt clock. With this, the watch achieved an accuracy of better than 0.01 s / day deviation, and was also superior to the quartz watches invented around 1935 .
As early as the 18th century, the seconds pendulum had generally established itself as the frequency standard, as soon as the more precise mechanics of the watch escapement could reduce the friction and keep the amplitude constant. On Observatories special astronomical clocks were used, the second hand was connected to the shaft of the escapement wheel and narrowly further jumped to the pendulum. The time measurement refined by Shortt made it possible for the first time to prove that the rotation of the earth is not completely uniform due to the nutation caused by the sun and moon .
73 de Scott KF5JRV
Pmail: KF5JRV@KF5JRV.#NWAR.AR.USA.NA
Email KF5JRV@gmail.com
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