AMC Atomic Clock
January 29, 2018
The AMC Atomic Mechanical controlled consists of a stationary master clock and a wristwatch. The functions of the wristwatch are explained hereunder.
In addition to the basic hours, minutes and seconds, the AMC model features the following complications:
• Power-reserve indicator
• Oil Change indicator
• Automatic rate adjustment
• Synchronisation with the master clock
• Rewinding the wristwatch by the master clock
The power-reserve indicator shows the state of wind of mainspring barrels. The movement is powered by two stacked barrels giving a power reserve of four days.
Oil Change indicator
The Oil Change indicator shows when the movement is due to be cleaned and the oil in the bearings changed. For this purpose the Oil Change indicator is driven through a reduction gear. If the watch operates nonstop, the indicator will take more than four years to go around its dial. We recommend having the movement serviced after about three and a half years of operation to avoid any damage.
Interaction with the master clock
The master clock has to oversee the various requirements and limitations of the watch. The interaction takes place in three broad steps.
1. Automatic rate adjustment
2. Time synchronisation with the master clock
3. Winding the wristwatch by the master clock
Automatic rate adjustment
This complication enables the watch to be adjusted by the master clock. This means the wristwatch has to be mechanically connected to the master clock.
The mechanism receives an impulse from the master clock via a pusher in the case of the watch. This must be repeated at different intervals to establish the time basis for the adjustment.
If the time varies from that of the master clock the adjustment index will be shifted slightly, altering the rate by about 2 seconds a day to counteract the variation. The rate can be progressively reduced according to the time intervals determined by the master clock. Thus the time difference at the last adjustment is kept in the master clock.
• Adjustment only takes place if the rate exceeds 10 seconds a day.
• The rate cannot be more than half a minute.
For this reason, the initial adjustment can only take place if the last synchronisation was not more than 24 hours previously.
Pressing the pusher turns the sliding lever clockwise. This pulls a small fork along, allowing it to move freely about its axis.
Both pins of the fork are in contact with the callipers. The callipers close when the fork is withdrawn. The callipers do not close symmetrically to enable the fork to move along a linear guide.
The calliper system
The calliper system is a purpose-built symmetrical construction. In addition to impulse planes for each calliper arm, the system also has two fingerpieces, one acting as a feeler, the other as a switch. In the starting position (pusher released), the arms of the calliper are kept apart to the buffers by the spring. There is thus no contact with the calliper disc.
The movement of the calliper is governed by the calliper disc, which is fixed to the seconds hand. If the rate is less than 10 seconds, it is considered in the neutral position. That means that the callipers are blocked by the calliper disc and can no longer draw together. No adjustment takes place.
When the calliper disc is not in the neutral position, only one arm of the calliper is blocked while the other arm can travel the entire distance. When the calliper closes, the calliper disc rotates at the same time.
Shifting the index cam
One arm of the calliper acts when the watch gains; the other when the watch loses. Below, from left, are shown the positions for a small variation in rate, and with the watch gaining and losing.
During the shift operation, three actions happen simultaneously:
• Sensing the calliper disc and rotating it if necessary.
• Shifting the index cam
• Holding the index cam in position.
The rotation of the index cam moves the index lever that acts on the balance spring. A peg at the end of the index lever rides in a spiral groove in the cam, shifting the lever when the cam rotates. Each step of the cam changes the rate by around 2 seconds a day. If the index cam turns clockwise, the watch goes slower.
Synchronising with the master clock
This mechanism enables the minutes and seconds to be synchronised to the time of the master clock.
The mechanism is activated by a pusher in the case of the master clock.
The minutes and seconds hands fly back to zero and the hours hand to the nearest hour. As soon as the pusher is released the hands are set free and the movement runs independently.
The movement of the pusher is transmitted to the heartpieces by a system of levers.
The hammer lever drops on the heartpieces to rotate them to zero, as in a chronograph.
The hammers are not fixed to the hammer lever, enabling the two heart pieces to be positioned precisely.
The heartpiece for the seconds is mounted directly on the shaft of the seconds wheel. For the minutes, the rotation of the heartpiece is transmitted to the minutes hand via an intermediary wheel.
The hands are zeroed by the master clock a short time before the hour. When the hour is reached the master clock releases the pusher and the zeroing lever springs back to the starting position. This releases the heartpieces allowing the movement to resume its function. The minutes and seconds show the same time as the master clock.
Winding the wristwatch from the master clock
The wristwatch is wound by the master clock by means of a shaft that acts on the winding crown. When the wristwatch is placed every night in the master clock to be wound, it should not be wound by hand.