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Discussion in 'Chronometers' started by gmorse, Mar 17, 2016.
What an incredible film! I've bookmarked it now - thanks Graham
Thank you so much Graham. I had lost track of John's work after the Longitude Symposium and had not seen anything of his output since then. The Emmanuel chronometer is truly an amazing exposition of the chronometer escapement. The other short clips on his web site are also pretty wonderful. I may need to do some tracking to find the longer versions and animations of the ones he did as work for hire.
No words possible. And that's from one known for verbosity. Thanks for sharing this very timely (for me) link. I've been trying to understand the workings of the spring detent in my Hamilton model 21, and that animation put it right there in front of my eyes. It's exactly what I was hoping for. Truly world-class animation. I'd have to say it was perfect. So there's a word rightfully well-reserved, and in this case, well-deserved. Cheers.
A masterpiece esthetically and technically! Thank you for sharing. As you said, "no words required!"
Is that what that type of escapement is called, chronometer escapement?
Why does there need to be the dummy pass where the strip is pushed out of the way? What does the strip do that can't be done without it there?
Have another look at the video; if the gold passing spring wasn't there, the detent locking stone would be crashed into the escape wheel on the clockwise swing of the balance. The balance only being impulsed on the anticlockwise swings gives it the maximum possible degree of detachment.
It is called a chronometer escapement, or "spring detent", and this one is based on Thomas Earnshaw's design, which you'll notice locks with the detent in compression. I know that looks counter-intuitive, especially considering the thickness of the spring supporting the detent, but it's been found to give the best performance.
But isn't it exquisite?
Exquisite it definitely is. Thanks for the explanation, I'll take a closer look again. I had heard of spring detent now I know what I am looking at.
That has been called a spring detent escapement (there is also a pivoted detent escapement), a "chronometer" escapement, and/or an Earnshaw escapement. This type of escapement gives impulse to the balance wheel only every second beat of the balance. The spring you refer to is often called a "bypass" spring. The video calls the jewel that activates that spring as a "dummy pass" jewel (often called a "bypass" jewel) that fits into a roller on the balance staff. In one rotation, the bypass jewel pushes the bypass spring aside and completes its cycle. On the return trip, the bypass jewel pushes against the bypass spring which pushes the detent aside, allowing the detent jewel to unlock a tooth on the escape wheel. While this is happening, a trailing tooth on the escape wheel comes in front of the impulse jewel in the impulse roller (also on the balance staff), giving the balance an impulse, when the detent jewel releases the escape wheel. The detent jewel returns to a locking state immediately, once the bypass jewel releases to bypass spring, to stop the very next escape wheel tooth. Then the whole operation repeats. If you observe the arms on the escape wheel in the video, you can observe the escape wheel turning. You don't see it turn if you watch the teeth of the escape wheel because everything happens so fast! I am certain the animation should be easier to understand than my description!
Thank you Graham, that was amazing!
The terminology I am familiar with is the "passing spring", the "impulse jewel" and the "unlocking jewel". The geometry is very intentional with the unlocking jewel having the shortest action radius so it takes the least energy from the balance and the impulse at a much larger radius to have the briefest period cf contact between the escape wheel and the balance. i.e. the greatest detachment.
As Doug mentioned when looking at this in real time, you cannot see the teeth move on the escape wheel. It looks like only the spokes move. If you can see the teeth move the watch needs servicing.
Oh where do people find the time and energy to produce such great things. thanks, Graham.
Truly we live at a great time when people can be shown the never before seen in such great detail and in many different ways which in turn allows the average person to learn and understand how and why things work like never before and it will only get better in time, Take for example IBM's "Watson" and where that is heading and how great it would be to ask any question in any natural language and it understands what your question is and it searches all the accumulated knowledge of mankind and in no time at all it can give you the answer in a number of different ways, If anyone has seen the movie "AI" they will certainly remember this line "Ask Dr. Know. There's nothing I don't", how great that will be some day......