Accidentally left chronograph running on speedy 1863 movement

Archer, I have understood that you are a watchmaker on the forum.

I read your entire reply and understand your explanation. Pretty cool to be honest, and it makes sense when you consider that the torque decreases as the main spring unwinds.

A sincere thanks for taking the time to write that up 😀

For about the millionth time.

Maybe what’s missing is a time frame.... all mechanical watches being used continually will see their oils dry.... after about 5 to 7 years?

Awesome! I think he should met with "n'importe qui" 😁


There is extra work on the gear train when the chronograph is engaged. More wheels and hands to rotate, it is surely not free.
Maybe it can help to complete all that was already written...

1/
The power of the mainspring is delivered to the watch through the gear assembly. Most of the time, the gears are stucked and the mainspring cannot unwind because its torque cannot overpower the reason why the gear assembly is stuck... Note that a "sufficient torque" to move the "stucked gear" would cause the destruction of those gears ^^
The mainspring also cannot unwind "through the crown" because a spring prevents it to unwind the "wrong" way (preventing this spring to do its job is also how you unwind a watch before disassembling it)

For now, we have a stucked mainspring, that does not release any energy.


2/
When the balance wheel hits the pallet fork, it frees the whole gear train, and the mainspring can unwind... until the whole thing get stucked again by the pallet fork. The gear ratio dictates by how much the mainspring unwind each time. How often it occurs is dictated by the balance wheel. That is why it is also called the regulating organ: it is regulating the delivery of the energy from the source..

So... now we have the same amount of energy delivered during a same interval of time, with or without chronograph (or other complication) engaged

It surely looks like work is done for free...


3/
It is the most important, and often forgotten, part. The energy of the mainspring is delivered to the gear train, and part of it is transmitted to the balance wheel. It is the balance wheel that hits the pallet fork and frees the gears, remember? No energy stored in the balance wheel, no beat. If you do not trust me, just destroy your hairspring and see what happens 😁

When a complication is engaged, the balance wheel receives less energy. Part of what it usually receives was already consumed by the extra gears. It reduces the amplitude of the balance wheel, but as it is isochronous, the watch does not slow down nor speed up.
Because the amplitude is lower, the torque the balance wheel can deliver is also smaller. At one point, the balance wheel cannot overpower anymore the pallet fork and make it move...


In the end, The torque required by the watch to continue to work is not the one delivered by the mainspring to move the gear train, but the one delivered by the hairspring to move the pallet fork. It is always the same amount, but when the chronograph is engaged and the mainspring is also low on torque, the hairspring does not get that extra amount of energy, and the next beat it cannot deliver the required torque anymore.