Robertson’s ‘Time Machine’ gets a new lease of life
11 October 2019
Last night saw the official unveiling of the newly restored Robertson Clock, a notable timepiece that previously graced the Wills Memorial Building and controlled the chiming of Great George, the huge bell at the top of the tower, from its inauguration in 1925 to the 1960s. The ceremony took place in the Pugsley Lecture Theatre Foyer in the Faculty of Engineering’s Queen’s Building where the newly functioning clock takes pride of place (though it no longer controls Great George).
The clock was the brainchild of David Robertson (1875-1941), first Professor of Electrical Engineering at Bristol University. Among his many interests was the application of science to the design of accurate mechanical clocks and he authored many important papers on horology.
Making a case
Long before the advent of quartz and atomic clocks and GPS satellites, pendulum clocks kept the world’s time. Robertson’s clock was synchronised daily with time signals sent out from Greenwich by telegraph. His method of synchronisation was unique and notable in that it anticipated the phase-locked loop and phase/frequency detector now vital in radio, telecommunications, computers and other electronic systems. It was arguably the first ever true instance of the phase-locked loop and predated electronic versions by a decade.
Recognising its significance, the University’s 'Historic Buildings and Gardens Committee’ chaired by Alan Stealey, Head of External Estates, made a commitment to return the clock to its former glory. Led by Dr John Haine, visiting Professor in the Department of Electrical and Electronic Engineering, the restoration was entrusted to Johan ten Hoeve of The Clockworks.
As part of this initiative, Professor Robertson’s original engineering drawings will be made available online for the next generation of horologists. The clock was made by Messrs. Brecknell, Munro and Rogers of Thrissell Street, Bristol, “mechanical, electrical, and tramway engineers”.
A place in time
Professor Robertson’s IET obituary pays tribute to his strength of character: “The fact that he was confined to an invalid's chair by paralysis of the legs for the last 30 years of his life makes the achievement of his work so much the greater. With characteristic thoroughness and ingenuity, he so adapted his methods of teaching and working that he was able to fulfil all his duties… The beauty of his character was revealed by the way he bore this affliction, and his patience and kindliness were a constant source of inspiration to all who had the privilege of knowing him.” His students included Paul Dirac who later won the Nobel Prize for physics, and paid tribute in his writings to Robertson’s influence on his mathematical thinking.
Robertson’s name for the clock ‘A Time Machine for the University of Bristol’ – certainly hints at a wry sense of humour and maybe a nod to H G Wells. We think he’d be pleased to know that his clock will be keeping time far into the future, a talking point for students and the wider engineering community.
Although pendulum clocks have been superseded for keeping the world’s time, they are still human-scale mechanical oscillators. Pendulum dynamics is a fascinating field of research, still not fully understood even after 500 years of study. Aspects of the clock’s design offer a number of possibilities for student final year projects.
More about Professor Robertson, his clock and the history of the phase-locked loop can be found on Wikipedia:-
Robertson's description of his clock (PDF, 4,247kB) has been made available courtesy of the Institute of Engineers and Shipbuilders in Scotland
More about the interdisciplinary undergraduate course to study Electrical and Mechanical engineering:-