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The Evolution Of Tower Clock Movements And Their Design Over

The Past 1000 years

by Mark Frank

The Evolution Of Tower Clock Movements And Their Design Over The Past 1000

Years

TABLE OF CONTENTS

Introduction and General Overview

Pre-History ...............................................................................................

10 th through 11 th Centuries ........................................................................

12 th through 15 th Centuries ........................................................................

16 th through 17 th Centuries ........................................................................

The catastrophic accident of Big Ben ........................................................

18 th through 19 th Centuries ........................................................................

20 th Century ..............................................................................................

Tower Clock Frame Styles ...................................................................................

11.

Doorframe and Field Gate .........................................................................

11.

Birdcage, End-To-End ..............................................................................

12.

Birdcage, Side-By-Side .............................................................................

12.

Strap, Posted ............................................................................................

13.

Chair Frame ..............................................................................................

13.

Plate-and-Spacer, Strap .............................................................................

14.

Plate-and-Spacer, Integral Plate ................................................................

14.

Flat Bed ....................................................................................................

15.

Flat Bed, Common Hybrids .......................................................................

16.

Other ........................................................................................................

17.

Modular ....................................................................................................

17.

Common Escapements Found in Tower Clocks

Verge, Foliot using Crown Wheel ............................................................. 18.

Strob, Foliot using Pinned Wheel .............................................................. 19.

Verge with Long Pendulum and Short Pendulum ...................................... 19.

Recoil, Anchor .......................................................................................... 20.

Deadbeat, Graham .................................................................................... 20.

Deadbeat, Pinwheel ................................................................................... 21.

Gravity, Dennison Double Three Legged ................................................... 21.

‘Free’ Pendulum .......................................................................................

22.

Types of Remontoire Used in Tower Clocks

Overview and General Function ................................................................

23.

Escapement, Spring style ..........................................................................

25.

Gravity Train Remontoire

Wagner, Swinging Frame ..............................................................

25.

Differential ....................................................................................

26.

Epicyclical .....................................................................................

26.

Robin, Endless Chain .....................................................................

27.

Verite, Rocker ...............................................................................

27.

Gravity-Escapement type ..........................................................................

28.

Striking Systems Used in Tower Clocks

Count Wheel .............................................................................................

29.

Rack and Snail ..........................................................................................

30.

Pin, Roller Pin ...........................................................................................

31.

Cam and Modular Cam .............................................................................

32.

Carillon .....................................................................................................

33.

Winding Systems Used in Tower Clocks

Capstan .....................................................................................................

34.

Direct Winding Square ..............................................................................

34.

Reduction Gear/Winding Jack ...................................................................

34.

Electric .....................................................................................................

35.

Stirrup ......................................................................................................

35.

Maintaining Power

Endless Rope, Huygens ...................................................... 35.

Bolt-and-Shutter, Weight and Spring ................................. 36.

Spring, Harrison ................................................................ 37.

Epicyclical, Sun-and-Planet ................................................ 37.

Typical Tower Clock Installations .........................................................................

38.

Exterior Views of Some Clock Towers .................................................................

39.

Tower Clock Restoration Highlights .....................................................................

41.

Footnotes .............................................................................................................

47.

Photo Credits .......................................................................................................

50.

ii.

The Evolution Of Tower Clock Movements And Their Design Over The Past 1000 years

How many people here have a tower clock? - Probably very few.

Now how many have been personally involved in the restoration or maintenance of a tower clock?

- Also very few.

This is reflected in the fact that compared to the numbers of domestic clocks, few tower clocks

were made. These clocks were costly. Especially so when combined with the fact that they

normally operated one or more bells and required a structure for the whole to operate within

along with regular, skilled maintenance. Often the church or town that wanted to erect a clock

had to levy a special collection or tax. Occasionally the clock would be a gift from the town's

wealthiest family. Certainly a good PR move on their part!

The purpose of this discussion is to illustrate the evolution of horology through the various

mechanical and physical aspects as represented in tower clocks. This is related to most other types

of clocks in general as their development closely parallel each other.

The earliest surviving example of a geared device is the

Antikythera Mechanism c.78 BC from Greece. A

remarkably complex mechanism employing epicyclical

gearing with an estimated 33 wheels. It demonstrated

the existence of a highly developed Hellenistic tradition

of geared instruments which was transmitted to and

preserved in Arabic culture and, in turn, influenced the

development of the Western European tradition of

clockwork 1 . Surely simpler geared mechanisms existed

much earlier, perhaps by a few centuries or more. Man

had demonstrated long before the invention of the first

clock a sophisticated mastery of the mathematics behind,

as well as fabrication of, complex geared mechanisms.

However, these machines did not have to

contemporaneously tell time. In other words the gear

trains were moved manually in order to mimic or predict

the movements of the heavens. Nonetheless just take a

moment to study the complexity and subtle epicyclical

gear interactions in this machine on the following page.

The genius of those ancient peoples! No other evidence

of such mechanical sophistication occurs until the

construction of the St. Albans tower clock which was

equipped with a planispheric astrolabe about 1330 - over

thirteen centuries later!

The gear diagram as well as schematic wheel layout

shows the full ingenuity and complexity of this

device. To the right is a modern reconstruction based

upon forensic examination.

The first mechanical time piece probably appeared in Italy in the

10th - 11th century. Some credit Pacificus, Archdeacon of Verona

(c. 880) while others credit Gerbert, a monk, who later became Pope

Sylvester II (c. 996) with having the first mechanical clock. It was

small; of wrought iron construction about ten inches high. It hung

on the wall and used weights suspended on cords as its motive

power. The escapement was that of a verge / folio design. The center

arbor carried a rotating dial on which the hours were painted and

moved past a fixed pointer. The dial also carried a ring of sockets

into which the owner could put a peg. As the dial rotated the peg

lifted a lever and sounded a bell at a predetermined hour. This was

the forerunner of the humble alarm clock. It's purpose was to warn a

monastery official to call the brethren to prayer by ringing the

monastery bell.

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