How to build a clock

A lot of the jobs I do rely on two basic things. Firtstly I’m an engineer. I love understanding physics and systems. Secondly I love antiques and history and antiques so every time I see a broken clock I see a broken piece of history. History is history. There isnt old history and new history there is just history. So I fix clocks from any era. This balances well with my love of engineering because clocks encompass history as a constant variable. How we measure time. How we understand time. How we, as innovative human beings, are pressed by a compulsion to improve what we do. Some people believe this is primarily driven by capitalism and the edict of building a better mouse trap, but I believe it is something far more than that. We just like buggering around with things to make them “better” which is an entirely relitavistic word and concept. We promote entropy, the driving forward force of the universe, and just love making things more complicated to improve performance.

But you can over do it.

Clocks really really demonstrate this because in the rush to develop ever more accurate, portable and miniaturised time keeping systems we have made mechanial clocks far more complicated than they need to be in order to do exactly the same job.

So whats the simplist effective way of making a clock?

Its fairly straight forward and you can do it with wood, metal, or reclaimed materials.

A clock comprises of three essentail systems that link in a linear format. These are

  1. Power
  2. Gearing
  3. Regulation

Thats all you need. Its really as simple as that. Lets explore each

  1. Power. Clocks are either driven by springs or weights. Weights are better. This is because they supply a constant force. A hanging weight always weighs the same at the end of a string, not matter how long the string is. So if you base your power source on a weight then you know that the force going through your gearing is going to be constant. That means the rusult will be constant. The results in this case are the rate at which you minute hand goes round 360 degress in an hour. You dont really want that calculation to have variablility within its cycle. So you get a barrel with a cog on the end of it, wrap a string round it, and then hang your weight from the barrel. The turning force of that barrel with the weight hung off it will always be constant. Because you included the cog on the end of the barrel you have a method of transferring that turning power (torque). Torque is measured in foot pounds or newton meters. Imperial and metric. Imagine you have a car wheel. You weld a metal bar that is 1m long to the centre nut so it sticks out like an arm from the centre of the wheel. You then hang a 1kg bag of sugar off the end of the welded rod. You have created a turning force of 10 newton meters. Im not going to bother with an explanation of how newtons are force and KG is mass. Its the same as far as we are concerned in this article. My point is that the force you transmit up a gear train from the source is calculable quite easily. If you hang a 1kg weight from a 1m radius barrel then you are generating 10 newton meters of torque (there are about 10 newtons to a kg). Im probably going to far with the maths here as this is a concept article.
  2. Gearing. The reason you need gearing is to spread out the drop of your weight so your clock doesnt work for 10 minutes before the weight his the floor. Its to slow down the rotation of your barrel with the weight on. Each spindle in a clock has a wheel and a pinion gear. The pinion gear has a set fraction of teeth compared to the wheel mounted on he same spindle. Its a ratio converter for your torque. So you know from “power” what your output is but now you want to divide that up into smaller chunks of power per second. You therefore gear down via connecting pinions and wheels in a sequence until the last cog in your gearing turns quite quickly but with very little force. The last cog in the gearbox is called the “ESCAPEMENT”. This is where the pedal hits the metal and power is transferred to the regulator.
  3. The regulator. The regulator is the part of the clock that actually measures out time into consistent units. The idea is to make one, or an exact division of these units, equal to one second. There are three common types. Quartz crystals that vibrate at a very specific and exact frequency when an electrical current is passed through them, platform escapements where a cartwheel on an axle rotates back and forth because theres a spring attached to it, and a pendulum. A pendulum is the best. A pendulum always swings at the same speed in a vacuum. That means that if you start the pendulum with a big arc or a small arc is will always pass the “down” centre point with the same frequency. Thank Newton (Issac not the unit) and Huygens the astronomer for that. This means that if you put a device on your escapement cog that allows each cog tooth to push the pendulum just enough to account for air resistance then your escapment cog is going to turn at whatver rate the pendulum passes the down centre point. The device that does this is called an anchor escapement. Imagine an upside down anchor hanging over the escapement cog. The pendulum attaches to the shaft of the anchor and the anchor points are set low enough so that when the pendulum is at rest the points sit in-between the escapement cog teeth and prevent it from going round. I wants to go round and is applying force to do so, but not enough to start the heavy pendulum off. If you swing the pendulum then one anchor point goes up and the other goes down. The one that goes down connects with the side of the cog tooth thats trying to turn and the force is transferred to the pendulum. As the pendulum swings to the other side of the anchor comes down in between the escapement teeth and the process of force transmission continues in this repeating cycle.

If you change the length of the pendulum you will find the point at which it swings back and forth at 1 second. If you escapement cog has 60 teeth then bingo (each swing is one second, left or right). That sorts the seconds and minutes out so an hour hand just needs to be put on with an offset cog at a 1:60 ratio. Easy really.

If you have understood this you’ve just made a clock. The actual production is just detail.

Incidentally all this is really down to Newton and Huygens. Every few generations has their greats and if you want to know who ours is its Elon Musk. We are privileged to live in his lifetime and I highly recommend you follow what he is doing, how he does it, and how he thinks. A new type of genius for a new age.