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(Why) does the escapement/balance wheel have to be post gear train?

Annapolis
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Caveat: I'm a Humanities guy through and through---no background in engineering of any kind. So I'm very open to the possibility that this is a completely stupid question to anyone who knows anything about mech-e. But I'm trying to learn more about the way my mechanical watches work.

As I understand it, the mainspring drives the gear train (the watch-works) leading to the escapement, which controls/regulates the output (the heartbeat) of the entire operation. Basically, the power comes from the spring, and the escapement controls the cadence at which that power is released; the gear train is in between.

I get too that the gear train delivers some resistance/torque, right? So it's not, like, a neutral thing.

But why (for the sake of argument) couldn't the escapement/balance be right after the mainspring and before the gear train? What functional difference would that make to the performance of the watch? Harder to regulate if that were the case?

...Does this question even make sense?
 
Canuck
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In my opinion, the amount of power required to operate a gear train would be far and away to powerful if it were even possible to insert the escapement and balance wheel immediately after the mainspring barrel, but before the train wheels! The escapement and balance wheel system is by far the most sensitive and delicate part of the movement. From an engineering point of view, what you suggest is simply not possible. The escapement doesn’t “control the cadence” as you imply. The balance wheel and hairspring regulate the cadence. All the escapement does is to keep the balance wheel oscillating.

The mainspring barrel reacts very slowly and in minuscular outputs as the watch operates. The escapement operates with quicker, more obvious cycles, more consistent to what happens that far from the mainspring barrel.
 
Annapolis
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Ah, ok. I think I had a too-simplistic understanding of how the escapement/balance bit works. Appreciate your taking the time to reply.
 
Dan S
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I would need to think more about this, but off the top of my head I think it would be challenging to transmit much torque through the balance/escapement. But there are many designs that have been attempted over the years, so who knows.
 
Archer
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Annapolis Annapolis
Ah, ok. I think I had a too-simplistic understanding of how the escapement/balance bit works. Appreciate your taking the time to reply.

The gear reduction that the train does also reduces the torque and loads. To power the escapement and balance directly from the mainspring without that reduction would have implications for the not only the forces on the escapement, but the mass of the balance that would be required. A large balance would need larger balance spring, pivots etc., which adds more friction.

Also, the mainspring barrel turns incredibly slowly, so in a typical watch the barrel turns about 6 or 7 times over it's full power reserve. How you practically make such a slow turning gear (which is what the barrel drum is) into something that would actuate an escapement at any sort of frequency would be a challenge (of course adding a gear train is the answer, but not to your scenario).,

There would be a number of hurdles that would have to be overcome to make this possible...
 
Annapolis
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I didn’t realize the mainspring barrel turns _that_ slowly.

This was educational. Thanks, all.
 
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