Warranty.
Introduction.
Gravity Settings
Calculate Pendulum Length
Change in length.
Pendulum beats from info on clock
plates
Calculate Wheel diameter and depth of
cut
Wheel Module:
Cutting speeds
Calculate how much to
shorten an overlength mainspring.
Moonphases
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Clockmakers Aid has been written to provide a quick and easy way of performing routine calculations needed in a clockmakers workshop. It is based on some of articles published in the British Horological Institute's magazine 'Horological Journal' as well as the BHI's Correspondence Course. Modifications were made to the program based on the suggestions of Mr I Thorpe, these suggestions were accepted with great appreciation and have improved the usability of the program.
The program will perform calculations for gear cutting operations, pendulum length calculations, cutting speeds, mainspring calculations and will show approximate moon phases. It is strongly advised that you make a working copy of these pages for normal use, and store the masters in a safe place.
The pendulum calculations are based on an article and formulae published in the August 1988 edition of the 'Horological Journal' by Mr R.C. Barclay of the USA. Additional material was used from the British Horological Institute's Correspondence Course. The Wheel calculations used in these options are based on an article written by Eliot Isaacs FBHI and published in the October 1988 edition of the BHI's 'Horological Journal'. The cutting speeds were taken from the Presto ™ Cutting tools advisory booklet. The mainspring calculations formulae are from the British Horological Institute's Intermediate correspondence course.
The pages have been designed to be stand alone pages so that they can be saved in a convenient place, such as the desktop, and called at any time without having to log on to the Internet.
If you do not live in the UK, then you will need to change the gravity setting to your local setting. The table below gives suggested settings for various places in the world.
| Town | G in cm/sec/sec |
|---|---|
| London | 981.2 |
| Aberdeen | 981.7 |
| Belfast | 981.5 |
| Edinburgh | 981.6 |
| Manchester | 981.4 |
| Montreal | 980.7 |
| New York | 980.7 |
| Paris | 980.9 |
| Toronto | 980.5 |
| Washington | 980.1 |
This option is used to calculate the theoretical length of a simple pendulum required to maintain timekeeping on a clock that has a known gear train. The length of the pendulum will then be given in cm
The formulae used are:-
Vibrations per minute
V =(CW x TW x EW x 2) / (TP x EP x 60)
where, V = Vibrations per minute
CW = Count of Centre wheel teeth
TW = Count of Third wheel teeth
EW = Count of Escape wheel teeth
TP = Count of Third pinion leaves
EP = Count of Escape pinion leaves.
Theoretical pendulum length
L =(T2 x G)/ (PI2)
where L = Theoretical length of the pendulum
T = Time of vibration (seconds)
G = Gravity in cm/sec/sec
PI = 3.1416
This option is used to calculate the change in a pendulum's length to correct its timekeeping error. It is used when a clock has been running for a known length of time with a test pendulum, and it has not kept correct time.
Corrected pendulum length
LC = LT - (LT(1 - E/R)2 )
where, LC = Corrected pendulum Length
LT = Test pendulum length
R = The running time of the test
E = The error in time after the run
On the back of many clocks there is an indication of the optimum theoretical pendulum length. On Modern European clocks it is in cm on French clocks it is in Pouce. Using this option you can convert these theoretical lengths to beats per minute, or seconds per beat, for use on electronic timers.
period = sqrt(Pendulum length in cm x PI2)
NOTE: 1 Pouce = 2.707 cm
This option is used to find the blank diameter of a wheel or pinion if the module and the number of teeth is known. The correct depth is best found visually, adjusting the cutter in until the correct tooth shape is formed.
Note that the following constants will be used:
Addendum <9 leeves = 1.61, 9-13 teeth = 1.71, 14 teeth and over = 2.76
Wheel/Pinion Diameter
Diameter = (No. of teeth + Addendum constant) x Module
This option is used to find the module of a wheel or pinion if the diameter and the number of teeth is known. The correct depth is best found visually, adjusting the cutter in until the correct tooth shape is formed.
Note that the following constants will be used:
Addendum <9 leeves = 1.61, 9-13 teeth = 1.71, 14 teeth and over = 2.76
Wheel/Pinion Module
Module= Diameter/ (No. of teeth + Addendum constant)
This option is used to find the suggested optimum rpm for machining metals. The rpm's are based on the assumption that sharp High Speed Steel tools are used. If you are drilling, I would suggest that you reduce the suggested speed by about 20%. The formulae and the default suggested speeds are taken from the Presto Cutting tools advisory booklet.
The speeds used are:-
| Material | Cutting Speed m/minute |
|---|---|
| Aluminium | 60 |
| Copper | 60 |
| Brass | 30 |
| Bronze | 30 |
| Soft Iron | 30 |
| Mild Steel | 24 |
| Cast Iron | 24 |
| Stainless Steel | 12 |
| Silver Steel | 12 |
Cutting Speed
RPM = Cutting Speed/(PI x Diameter of work or Drill)
In the UK. mainsprings are purchased by specifying the height, strength and barrel diameter. Some times you cannot get the correct spring for the diameter of your barrel. It is then necessary to shorten the mainspring to suit the barrel. This can be done by trial and error, but this option gives an approximate amount to remove from the end of the spring.
This option will calculate approximate moonphases using formulae published by F.W. Britten. The formulae were also published in the Horological Journal in January 1992. The moon phases given should be within two days accuracy of the actual phases.