People generally do not understand what makes a clock "accurate".Originally Posted by megabyteme
Even movements specifically built for accuracy and housed in barometrically stabilized (or even vacuum) chambers are not constantly correct to the second...what they strive for is being wrong consistently.
A clock that gains five seconds every day is considered "more accurate" than one which is perfect for 10 days then suddenly loses 10 seconds.
I built a regulator movement for a quite serious collector who installed it (after building a magnificent case) into a climate stable, electronically monitored room. the swinging pendulum broke a lazer beam which allowed for continuous data logging. It was within one second for 40 some days and then spasmodically gained 5-6 seconds. We attributed this to binding in the Harrison gridiron pendulum I'd built.
The second movement I built for him used a single Invar rod and a mercury glass jar bob, I'm not sure how well that one performs.
Of the clocks pictured, the second one is probably the most conventionally "accurate", It's a remontoire movement and will hold to within 5 seconds over the course of it's 30 day run between winding.
The first clock (with the big gear or "great wheel") was later converted to a variation of the Breguet twin pendulum regulator and occasionally has long periods of dead nuts accuracy.
Keep in mind that there are over 2.5 million seconds in a 30 day month, so really, anything better than a few seconds a day is pretty fucking good.
If accuracy interests you, read the story of John Harrison (he, along with Charles Babbage, is a hero of mine), who, more than anyone before, understood what "accuracy" was all about.
I wasn't aware of "injustice in my story"...I just couldn't afford the time required for a build (average about 6-9 months apiece for the show clocks) without having presold the work.
I do have the prototype of the great wheel clock (I wasn't sure I could make a 8" diameter, 360 tooth gear successfully) that does not have all the upgrades of the final piece (the final has titanium gears, full ball bearing pivots and a jeweled half impulse escapement).
It does run although I like it best with no dial or hands, so there's not much point in keeping it wound.
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