Mercer Chronograph No 222_3
Mercer Chronograph No 222_5
Mercer Chronograph No 222_4
Scarce battery operated and wind-up pen version tape chronograph by Thomas Mercer, St Albans, No 222, c1950, for use with a chronometer

Tape chronograph principally constructed in aluminium and brass, with substantial clockwork motor having two speed gearbox, electro-mechanical stop and start, speed control, roller driven tape transport with pinch roller, twin solenoid markers with pen carriers creating time code and event. Tape feed from external spool. Case marked with serial no. “222.”

All contained within a bakelite swing top case constructed with bright polished aluminium bracing, plated over centre catches and maker’s ID plate to front. Circuit diagram to lid inside, internal mounting points for tools and winding key, end mounted Bulgin six-pin socket with connections to solenoids and time code operation. Connection loom with six-pin Bulgin plug feeding into three cables, contact key, master chronometer and battery.

Operation: Essentially, this is a highly accurate event timer designed to operate in tandem with a Mercer chronometer fitted with single or multiple electrical contacts. The basic principle is that a paper tape similar to a ticker tape is moved beneath two solenoids, electro-mechanical devices which cause pen carriers to move up and down, imparting small inked marks along the outer sides of the tape.

One set of inked marks will be the time code, created by the making of electrical contacts within the master chronometer, usually timed on the second, but the duration may be longer depending upon the application.

The other set of inked marks created along the opposing outer side of the tape will be created on the making of the contact key or an amplified radio beacon signal. Thus the ‘event’ time maybe very accurately recorded, the distance between the time code marks on the second broken to 1/100ths of a second.

Interpretation of the marked tape was made optically through a magnifier and ground glass Fresnel Screen divided to 1/100th second

The contact key itself was developed over time and the specification had to be changed with the introduction of needle markers.

Comments: Perhaps the ultimate manifestation of the hybrid electro mechanical timer, these instruments are rarely seen, occurring far less frequently than the chronometers that were designed to drive them. Up until the acceptance of solid state timing equipment, these were the main stay of scientific analysis, chart making, ballistic study and record breaking.

Manufactured to the exacting standards one would expect from the maker of chronometers and other first class timing equipment, this is an instrument that is immediately interesting both mechanically and aesthetically.


Stock No: SI1589

Price: Vavasseur Archive – not currently for sale