| Collection | ABDNP University of Aberdeen, Natural Philosophy Collection of Historical Scientific Instruments |
| Object Name | Graham's dead beat escapement |
| Object Number | ABDNP:200022a |
| Other Number | 22; C113 |
| Other Number Type | old number; collection number |
| Brief Description | Brass and wooden model of escapement with 60 second face. Pendulum ( ABDNP200022b ) fits on rear. Holes on right of base probably for small pulley wheel, now missing. Dial marked in seconds and labelled every 10 seconds. Escapement wheel 152 mm external diameter. Replacement dial hand fitted in 1982. It's special feature is that the escapement wheel doesn't rebound at each tick but stops dead. |
| Dimensions | height 267 mm; dial diameter 150 mm; base depth 183 mm; width 230 mm |
| Materials | brass, wood |
| Condition | good |
| Completeness | incomplete |
| Completeness Note | missing small pulley wheel on base plate to take cord of driving weight, which is also missing |
| Maker | J. King |
| Object Production Place | Aberdeen |
| Object Production Date | 1781-1789 |
| Object History Note | 1790 list |
| Publication Note | LEMUR database; 'Science Preserved' (1992) Mary Holbrook; Newsletter No. Mar. 1993. King's visitors' centre caption "One of only three surviving models made by Patrick Copland's assistant John King in the mid 1780s. King was a trained clockmaker. An escapement of this |
| Caption | "Graham's Dead-beat Escapement Among the many distinctions earned by Marischal College must be its pioneering venture, among British Universities at least, of employing a full-time scientific instrument technician. By the mid nineteenth century, academic Assistants for Professors were becoming commonplace, to ease the burden of the Professor's teaching. It was not until the early twentieth century that technical assistance was similarly considered a necessity. Marischal College was sufficiently forward in promoting the use of demonstration apparatus in its extensive Natural Philosophy course that it took on a technician in 1783. His name was John King. At that time he had newly finished his apprenticeship as a watchmaker, though he did not have his Burgess's licence to practice this trade within the City boundaries. The College paid for him in the first instance with a 3-year grant from the Board of Trustees for the Encouragement of Manufactures in Scotland. Extending his stay, John King remained for 7 years, leaving in 1790 or 1791 to establish himself as a clockmaker in Tanfield (now a suburb of Aberdeen). Clocks signed 'Jno. King' are still to be found in the North East. The few extant examples of John King's College work are unsigned (since he was in the employ of the College). Among these few is this oversized model of a dead-beat clock escapement. In a pendulum clock, the escapement serves the dual purpose of transmitting the power of the weight to the pendulum to maintain its oscillations and transmitting the timing of the pendulum to the gear train that drives the hands. It is the escapement that makes the clock's tick. Any imperceptible irregularity in the motion of the escapement builds up over thousands of ticks to affect the clock's timekeeping. Graham's dead-beat escapement was the design used on most high precision regulators because of its smooth recoil-free operation."
Author: Reid,John.S Date: 1993 Purpose: University.Newsletter
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