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Mark of Mission #1: Telling the Gospel
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Thanks go to Jack Thornton for his research about our Tower Clock, and for looking after the clock on our behalf for many years:

 

Clock mechanism 

The tower clock was installed on the second floor of the bell tower in December 1910, in a large wooden cupboard.

The makers, F.W. Benson of Ludgate Hill (see Note 1 below), were clearly proud of this fine example of Victorian engineering as the huge iron frame carries a brass plate with the inscription ‘Clockmaker to the Queen and Prince of Wales.’ This referred to Queen Victoria and Prince Edward, so the mechanism appears to have been made before 1901.

The wood rod pendulum beats 1.5 seconds and is coupled to a ‘dead beat’ escapement mounted in the flatbed frame. The pendulum weighs 100lb (47kg) and is about 8ft (2.5m) long. It passes down through a slot in the floorboards to the first floor, where fine adjustments of timekeeping rate can be made by adding or removing small weights, in the form of steel washers hung on a hook attached to the rod. For example, if the clock is losing 7 seconds a week, the addition of an 8-gram washer will correct the rate.

There is always a need for slight correction at least twice a year due to the change of temperature in the tower between summer and winter.

The escapement is coupled by bevel gears to a long vertical shaft, which reaches to the top of the tower, where a gearbox transfers the drive directly to the minute hands of the two dials.

Behind each dial is a set of gears, known as the ‘motion work’ which takes the one turn per hour of the minute hand and drives the hour hand round once every twelve hours. The ‘going train’ (the timekeeping part) is driven by an 80Ib (37kg) weight and a weighted lever provides temporary maintaining power to keep the clock ticking while the driving weight is being wound up.

Hours are struck on the ‘tenor bell’ – the largest in the set of 8 in the bell tower. This was cast in Whitechapel in 1724 and weighs approximately 1 ton.

Striking is achieved by means of a heavy hammer that strikes the outside of the stationary bell. The bell ringers have to withdraw this clock hammer before they commence ringing each week, otherwise the swinging bell could hit and bend the hammer.

A 250Ib (115kg) weight drives the ‘striking train’ and a rack striking system controls the correct number of blows. The two weights are suspended from stranded steel cables, which pass over two pulleys mounted high in the tower.

Once a week the weights are wound up by means of a large handle to this high level from which they gradually descend to ground level during the week, dropping a distance of 40ft (12m).

The rate of striking is governed by an airbrake in the form of a large 2–bladed fan. The speed of this fan can be adjusted by altering the pitch of the blades and is at present set to allow an interval of nearly 2 seconds between strokes of the bell hammer, i.e. it takes around 22 seconds to strike 12 o‘clock.

The original card of instructions for winding the clock stipulates that is should be oiled once a month and the mechanism completely dismantled for cleaning every three years, which seems an excessive amount of maintenance. However, lubricating oils at that time were fairly primitive and tended to oxidise and become rather like glue when exposed to air (see Note 2 below).

Fortunately modern clock oils are manufactured from highly refined mineral or synthetic oil and there is a grade produced specially for tower clocks (sometimes referred to as turret clocks). Oiling once a year is now sufficient and such frequent dismantling is unnecessary.

As there is no ‘seconds’ hand, timekeeping is checked at the first stroke of any hour and is usually consistent within a few seconds per month, so that small adjustments are needed only occasionally (except when squirrels or magpies build nests among the motion work behind the dials).   This accuracy is good considering the simple escapement type, the wide temperature extremes in the tower and the way the two sets of hands are exposed to wind and rain.

For some years after the clock was installed it was probably set to time according to a sundial, requiring a correction to convert the sun time to local mean time. Old pictures of the church show a vertical sundial situated above the entrance porch.

In 1924, the BBC introduced the time signal, using a direct line from the Greenwich Observatory to synchronise the ‘6 pips” with mean time at Greenwich.

We are fortunate at St Andrews to have such a good example of Victorian tower clock and in good condition, bequeathed to us by a previous generation. Provided it continues to be serviced properly it can be expected to keep good time for many years to come.

 

 

Further notes on the above:

Note 1: In the 1850’s J W Benson opened premises at Ludgate Hill, with a steam powered clock factory nearby. He died in 1878, leaving two sons, Alfred and Arthur to continue the business. In 1879 the company was awarded a Royal Warrant by Queen Victoria, followed by those of Edward Prince of Wales and the Kings of Denmark and Siam. Manufacturing ended when the factory was bombed in WW2.

Note 2: In late Victorian times chemists were working to develop oils suitable for lubricating steam engines, initially using combinations of petroleum, animal and vegetable fats. Lubricating oils in use at that time included almond oil, coconut oil, fish head oil, lard oil, olive oil, rapeseed oil and whale oil.  

 

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