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The design of a clock
The design of a clock
The elements of a mechnical clock
The elements of a mechnical clock
The Design of a mechanical clock clock can be broken down is several categories:
The motor, usualy weight driven or spring driven
The gears, layout and design, to transmit the movement and set the respective speed of elements
The escapement, regulates the timming, in clocks it usually use a pendulum, but can also be a balance wheel
The frame and enclosure, this where the parts come togheter, in a fashionable and practical way
A few numbers to get started
A few numbers to get started
In this example, the idea is to buid a clock that has a 8 days run time
It will be weight driven, I will chose a 1 meter drop as a start point
It will have a 30 teeth escape wheel that will have one rotation per minute, the pendulum will be about 1 meter long
The frame has to fit on a 200/200 mm printer bed, I want it to be modular to experiment with various escapements and motors
For 1 meter drop over 8 days, that is 125 mm per day
The escape wheel has 1 rotation per minute, that is 1440 rotation in 24 hours
If I where to place the driving drum on the hour arbor, that shaft will do 2 rotation per day, to get the 125 mm drop in a day:
125 / 2 = 62.5 mm per rotation
The diameter of the drum will need be 62.5 / 3.14 = 19.9 mm
The diameter of the drum can be doubled by installing a pulley on the weight, or the gear ration between the escape wheel and the drum can be increased. In the example above the ration: escape wheel to drum is 1/720
That also means that the weight needed to drive the clock is at least 720 bigger that what is needed at the escapement. In reality with friction and other losses, it is more likely to be 1000 to 2000 times bigger. This means that for every gram of pressure at the escapement pallet, the drive weight will be 1 to 2 kg
From this, 2 thoughts:
It is worth spending time on designing and testing an efficient escapement
The frame and the gears will need to be strong enought to handle 5 to 10 kg at the motor/drum
A basic clock
A basic clock
Just 3 arbors for the second, minute and hour hand, plus 2 transmission gears. Total 5 arbors
At the left:
The escapement with a 1 second pendulum and a 30 teeth escape wheel, the escape wheel does one rotation per minute and carry a second hand
In the middle:
The minute gear and hand. There is 60 minutes in an hour, so the ratio is 1/60 between the second and the minute hand.
At the right:
The hour gear and hand, including a drum to carry the weight to drive the clock, There a 1/12 ration between the hour and the minute arbor
Note: For this illustration to be to scale, the gears are module 1
The gears for the ration can be as follow
1/60 = 1/7.5 x 1/8 Gears teeth number can be: 12/90 and 12/96
1/12 = 1/4 x 1/3 Gears teeth number can be: 24/96 and 30/90
The total ratio between the escape wheel and the hour gear is 1/720
The hour gear rotates twice in 24 hour (one day). with a drum of a diameter of 50 mm, the drop in 24 hours would be:
Drum diameter x Pi x number of rotation in 24 hours
50 x 3.14 x 2 = 314 mm of drop for 24 hours. That is 2512 mm for 8 days
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