400 day vs 1000 day in accuracy

SpaceCowboy850

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Oct 29, 2019
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Is there any difference in accuracy on a 400 vs 1000 day clock?

My first thought is that since the mainspring of a 1000 day clock will be tighter and have more consistent power draw, over the course of a year, you could probably dial it in to be more accurate than a 400 day clock. Or at least as accurate as a 400 day clock is over 3-4 months.

My second thought is that none of this matters, and getting a clock that is within several seconds a day is generally considered high accuracy on a mechanical clock, but that still places you 5-10 minutes off every 3 or 4 months, and 400 or 1000 day, doesn't matter, that is a very hard goal to achieve regardless of how consistent the mainspring is.

And yes, yes, I know "if you want accuracy, go quartz", but I think there is something very satisfying about getting a mechanical movement as dialed in as possible. To me it's part of the allure of the mechanical - that this is just classic newtonian motion at work yet it can still achieve surprising accuracy.
 

KurtinSA

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My understanding is that there are three power regimes on 400-day main springs. When fully wound (or near that end of being wound), there is a bit of excess power and the clock will be fast. Towards the end, power is starting to falter so the clock will be slow. So, that leaves the long middle portion where the power is fairly constant and once regulated, the clock should be fairly accurate.

So, that suggests that a 1000-day clock will have a longer middle portion of power and thus be more accurate over a longer period of time. All other considerations taken into account.

Kurt
 
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MartinM

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What Kurt said. Except that more power equals a slower clock. Not faster.
 

MartinM

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The top of the wind (or a stronger spring) imparts more energy into the pendulum's rotation making it take longer to complete a cycle. As the spring weakens, at the bottom of the wind, the pendulum's rotation is decreased and the period decreases (cycle frequency increases), causing the clock to run faster. This is the same phenomenon for most spring-driven clocks that don't use a fusee system.
 

KurtinSA

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That's contrary to my limited experience. I seem to recall that a given clock will be running more or less within good regulation and then it stops. When I go back to wind the clock up, the first thing I noticed after a few days is that the clock is now running fast. That was the basis of my observation.

Kurt
 

victor miranda

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power and regulation of 400 day clocks do not seemed tied together in my
tests to get accuracy. getting them running and power are related however...

from what I can tell If you can get a 400 day like a schatz 53 to run
with the pin only pushing the fork and not touching the fork otherwise
you will get consistent regulation... well, improved anyway...
It is hard to know why the clock will change the
total rotation from 260 to 270 or the reverse...
the above does not mean faster or slower or that the regulation changed.

victor
 

MartinM

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That's contrary to my limited experience. I seem to recall that a given clock will be running more or less within good regulation and then it stops. When I go back to wind the clock up, the first thing I noticed after a few days is that the clock is now running fast. That was the basis of my observation.

Kurt
That is generally true for recoil escapements. Especially those with shorter and/or lighter pendulums. For the deadbeat escapements we see on 400 day clocks, it isn't. Extra power in the recoil escapement serves to stop the pendulum from making a full swing and effectively speeds up the clock.
 

Wayne A

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Interesting thread. I've been working on a miniature kundo that has been hard to regulate with precision. Running the book's listed .0023 spring with a steady 370deg of rotation it seems that the pallets were bottoming out on the escape wheel, well I thought that can't be good for accurate time keeping. Also the regulating adjustment was very sensitive to the smallest movement. So I switched the suspension spring to a .0024 thinking it would reduce the sensitivity of the regulating adjustment and perhaps reduce over swing from bottoming out the pallets. Results were that yes the regulating adjustment was no longer sensitive at all and very easy to set. Positioned the fork so the pallet no longer bottomed out and no flutter with the thicker spring. What was not initially expected was the rotation increased to 390deg but it really does make some sense in that the lost energy from the pallets bottoming out is now being used in the swing.