Has anyone ever bought a watch and found it was going backwards?
While the possibility seems intriguing, this would happen only if the watch was designed to do so, like in the original watch issued by Apple, and in some contemporary watches made for specific purposes. It is impossible that it happens by mishap.
There are watches built to run like that, and some come from famous brands as well, as these two Franck Muller demonstrate. However, if you mean that it could happen because of a technical fault, the answer is negative. Except by a demonical possession, that is.
It is technically impossible. And I will walk you by it and explain why.
There are several reasons why an ordinary watch – that is, one running clockwise – cannot run backwards.This would mean that I will be explaining a bit how a typical mechanical watch works.
1 – the shape of the arbor
First of all, to make hands turn backwards its wheels should rotate on the other direction – counterclockwise. This means that in a regular watch, in order for this to happen, the watch mainspring should be mounted on the opposite way. While this would be ideally possible, it could not happen, because if you do so the mainspring would not hold onto its central axis (called arbor).
The mainspring has a hole on one end (as you can see in the photo), and is coiled around the arbor when you wind it.
As you can see, however, the arbor has a sort of nail where this hole gets into – but you can also notice that its shape is eccentric: it has a sort of inner recess where the end of the mainspring goes.
If you try to mount it on the other direction, it will not stick in the nail, because the shape of the arbor would make it slide away. This is a sort of safety measure as well, so you have to mount the mainspring in the right direction.
3 – the shape of the escapement wheel and pallet fork
The escapement wheel is at the end of the wheel train, and is the one propelling the pallet – which most normally is in the shape of an anchor. You can see them below, the escapement on the right and the pallet on the left. The escapement is called a wheel, but its teeth are quite different from the ones used in normal gears.
As you can see, they are not symmetrical. This means that the escapement is made to turn in one direction only. If you try to make it turn in the other direction, it would not, because its teeth could not effectively engage the two ends of the pallet fork, and get stuck.
You can readily see that the pallet fork itself is not symmetrical, either. One arm is longer than the other, and the two rubies are set at different angles. This means that to make it run in reverse, you’d have to mount both escapement wheel and pallet fork upside-down, which is obviously impossible as they would not fit with the other elements of the watch.
So, to end…
As you can see, making a mechanical watch work in reverse is impossible, since its construction is made to let the mechanism rotate in one direction only. To rotate backwards, a watch should be designed to do that: it cannot just happen by mishap.
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