the english regulator
During the early 18th century, the development of the regulator clock was driven by the demand for accurate timekeeping. Work centred around The Royal Observatory, Greenwich, where timekeeping was central to astrological observation and later for the accurate measurement of longitude.
A regulator is capable of maintaining a going rate of better than 10 seconds per year which compares favourably with quartz mechanisms which at best can boast only +/-2 seconds per day.
High quality regulators use a dead beat escapement developed by George Graham [1673-1751]. Its action is evidened by the precise movement of the second finger as it rests momentarily on each second division.
As the driving power of a weight is constant the only variables affecting the accuracy of a regulator are the effects of temperature and barometric pressure.
The effect of temperature on pendulum rod length is overcome by the use of Invar, a metal with a very low thermal expansion coefficient.
Barometric pressure affects the density of air and therefore the swinging pendulum bob. To correct this I regulate my clocks when atmospheric pressure is at the ICAO average pressure of 1013.25 millibars at sea level. This ensures the clock shadows the pressure changes and maintains its rate over the long term.
The pendulum is of a fixed length and the final adjustment of the clock is made by the positioning of weights on the weight tray of the pendulum rod. Weights of up to 3grams in increments of 0.1gram are used to achieve rate of under ten seconds per year.
When a clock is being wound the drive power is temporarily removed. To avoid this situation regulators incorporate a mechanical contrivance built into the clock called a ‘maintaining mechanism’.
There are two types of maintaining mechanism, the first one designed by John Harrison [1693-1776] of ‘Longitude’ fame and the second is a bolt and shutter mechanism.
The Harrison mechanism is invisible to the user. The bolt and shutter mechanism cleverly uses energy by revealing the keyhole for up to two minutes while the clock is wound.
The driving weight for the clock is made of lead and housed in a brass housing.
4lbs are required to drive an eight day movement and 16lbs for a thirty day movement.
The distinctive feature of a regulator is the traditional dial in which second, minute and hour fingers have their own rings. The reason is that each finger is mounted on the end of an arbor requiring no additional cannon, and gearing to position the finger on a common centre as found on modern timepieces. Because additional gearing increases friction, this layout is mechanically more efficient.
The beauty of a regulator is that in its role as a precision timekeeper it has been spared the requirement of bells, gongs and chimes that the public has demanded for domestic long-case clocks.