Dorrin K Mace, Horologost

Dorrin K Mace, Horologost
The Clock Man in a pensive moment

Wednesday, January 25, 2012

The "Franklin" Clock

A Franklin clock with a four hour dial is one of the strangest horological phenomena. This type of clock was made for a period of about 70 years in very small numbers. Today there exist examples of longcase, wall and bracket clocks and there is also some early documented evidence of other examples.

In his "Clockmakers Dictionary" of 1855 Ferdinand Schade still defines the term "Franklin Clock".
On plate I of his dictionary this clock is illustrated. Thus it still must have been an accepted concept among clockmakers in Germany.
Original Franklin Clocks differ from conventional clocks in two main ways : - the train and the dial.
The train consists of only 3 wheels (including the escape wheel) and two pinions. The typical motion work with minute wheel, reverse minute wheel, pinion and hour wheel are not used at all in these clocks.
So a special type of dial was needed, and this is the distinctive feature in contrast to other clocks. It is basically a four hour dial showing the minutes i.e. 240 divisions, but the following variations occur:-

Bild 1

In the center of the dial is a 3 coil spiral engraved or painted which is divided into quarters corresponding to the four hours taken for one revolution of the single hand. The periphery of the dial has a minute ring for 4 hours, i.e. 240 divisions. The clock has a single centre hand the point of which indicates the minutes and its shaft passes over the centre hour sectors.

For one revolution the hand has taken four hours to cover all four hour sectors. These are numbered from one to twelve on the three coils of the spiral, see illustration No...... The user of the clock must know roughly what time of day it is in order to read the correct hour number from the right sector. Thus telling the time with this clock must have created problems. Nevertheless, the hourly indication by means of the spiral was retained, at least experimentally, by clockmakers such as Grant, Smeaton (the famous English civial engineer), and the royal clockmaker Vulliamy.

Franklin also provided a small seconds dial which popular English clockmaker Ferguson dispensed with in his first simplification of Franklin´s dial illustrated in Lloyd´s Dictionary.  At the same time the spiral disappears in favor of three concentric rings divided into 4 quarters. These rings were then used in later Franklin clocks by Kinzing, Klug and Porthouse et al. Ferguson tried to reduce further difficulties in telling the time. In a further design he reintroduced the conventional minute hand revolving once an hour with the hours and seconds indicated on discs seen through apertures in the dial.

This later design proves Ferguson’s rejection of Franklin’s four hour dial although he (Ferguson) retains Franklin’s simple three wheel and two pinion train.

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