John Harrison RAS Regulator 'Replica' - Video 2 of 13

A little patience is required: the main action occurs at thirty seconds intervals.

Presented is a view from the left (nine-o'clock) side.

There's more going on than a first glance (or the activity every thirty seconds) reveals, some of which is described below.

The most obvious motions are:

(1) - the pendulum, swinging from side to side in the left of picture. Each pendulum 'beat' (swing from one side to the other) takes one second.
(2) - part of the tiny, frictionless grasshopper escapement, almost completely hidden just above the pendulum (you might just be able to make out parts of the 'legs' of the grasshopper kicking, one kick every second). This will be shown in close-up in Video 4.
(3) - The quite long 'fly', near the cente of the picture, is only briefly allowed to rotate every thirty seconds (in other words, every thirty 'beats' of the pendulum - you can count the beats between each fly rotation event, if you're patient). The fly is linked to the 'remontoire', which is explained below.

The remontoire contains a coiled spring, and the energy stored in that spring keeps the pendulum swinging from side to side. The remontoire delivers far more precise 'packets' of energy to the pendulum (via the grasshopper escapement) than any other method could, which is absolutely essential to excellent timekeeping. The remontoire spring is rewound every thirty seconds, using energy from the main driving weight of the clock (just visible below the pendulum in Video 1 of this series). The fly is linked to the remontoire rewinding device, which is why it rotates every thirty seconds. The purpose of the fly is to slow the remontoire spring rewinding process down, otherwise it would be far too violent and cause damage.

The remainder of the mechanism is mainly special, low friction Harrison gearing and the unique Harrison-invented components needed to support it all with very low friction. The gearing feeds energy from the driving weight to the hour dial, minutes hand, seconds hand and remontoire.

All will become more obvious in later videos.

Further details at http://soptera.blogspot.com and http://www.hsn161.com/HSN/Heskin.php
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Category:

Science & Technology

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