Fuse Chain Operation for easing out Spring
ACTION
- A mechanical clock is run on the energy provided by a wound up spring.
- As the spring opens up, it provides the force needed to run the clock hands through a series of wheels and levers.
- A normal clock goes runs fast when spring tension is maximum and progressively slows down.
- A chronometer overcomes this limitation by using Fuse chain arrangement. .
- Fuse is a grooved brass pulley which is precisely tapered.
- A chain attached to the spring mechanism of a chronometer, is wound around the fuse as shown in the diagram.
- When spring is fully wound, most of steel chain is would around fuse.
- When spring tension is maximum, the rotating lever is at the fuse is minimum.
- As the spring tension reduces the fuse diameter increases ensuring a constant moment.
- Thus regardless of spring tension, the moment is constant and a steady gear movement is ensured.
How to start or reset the Chronometer?
- Lock the gimbals of the chronometer.
- Remove the glass of the dial by rotating it anti-clockwise.
- Fit the tipsy key over the square-headed nut of the centre spindle of the chronometer and rotate it clockwise, thus moving the minute hand and consequently the hour hand, forward.
- Set the hands to about 3 minutes before the time of the next available radio time signal.
- Since the position of the second hand cannot be adjusted, set the minute hand in accordance with the ‘position of the second hand (e.g. if the second hand has stopped at 20 seconds the minute hand should be set at 1/3 of a minute).
- In case the tipsy key does not fit on the centre spindle nut, the minute hand may be moved gently forward by a finger.
- The hands of a chronometer should never be moved backwards.
- Never touch the second hand.
- Screw on the glass of the dial, release the gimbal lock & wind the chronometer.
- Be gentle while handling the chronometer at this instant as it should not begin to work accidentally.
- Lock the gymbals, close the lid of the box, take the box out of its compartment and hold it clear of all obstacles.
- The chronometer is now ready to be started.
- When the time signal indicates about three minutes to go, give the box a quick quarter-turn (about 90° rotation in azimuth) in the direction of clockwise movement.
- The chronometer will start working.
- Gently replace it in its compartment and unlock the gimbals.
- Utilize the remaining ‘two minutes of the time signal to note the error of the chronometer.
- Make appropriate entries in the ‘chronometer log book‘.
How/ Where Chronometer is stowed?
The chronometer is slung by gimbals inside a wooden box fitted with a glass lid.The box is stowed inside a padded recess, normally located in the proximity of chart table.
The padding has two uses –
