This Water Flow Meter Clock came to the BWLR with the Thomas Horne beam engine from Henwood Pumping Station at Ashford in Kent and it was considered to be unserviceable. It was made by George Kent of Luton [Patentees: Clemens Herschel & Builders Iron Foundry USA].
George Kent of Luton is now owned by Asea Browm Boveri of Switzerland. Examples of a later model to the one on display at the BWLR are in the Brighton & Hove Engineerium.

This instrument for measuring water flow in a pipe was patented by Clemens Herschel in 1881 and is based on the venturi principle that when water flowing in a pipe passes a constriction (or throat) its increase in velocity causes a local decrease in pressure. If two tubes are connected to a pipe, one a full diameter and the other constricted, the change in pressure will cause a difference in water level in the tubes. Transmit this difference via floats to a pulley system and indicator then you have a measure of the flow in the pipe.

The role of the clock is to govern the rotation of the recording drum (the vertical brass cylinder) so that a permanent record of the flow of water against time is obtained as a pen carriage is pressed against a graph paper fitted to the drum. There is a raised area on the drum in the form of a parabola. the pen carriage also has a wheel pressed against the integrated drum surface which allows a cog to engage between the drum and the meter measuring gallons passed. the greater the flow the higher the wheel rests on the drum.

At the top of the drum most of the surface is raised and the wheel is held out for most of the drum circumference so allowing the meter to register. Conversely, if the flow is low the wheel is low on the integrated drum where it spends most of its revolution close to the drum surface, the cog is disengaged and the gallons not recorded.

The clock has a ‘dead beat’ escarpment with a spring over-swing absorbing device. This is an unusual addition but a safety measure in order to prevent damage to the escapement mechanism which has a large and heavy pendulum bob.
In horological terms the movement has a 1 metre length pendulum with a one second beat escapement.
3600 beats per hour.
86400 beats per day (24 hour).
31,536,000 beats per year.
Beyond a year – lots!!