ei8htohms
8555
lift angle
Hello nilomis.
Lift angle is the angle within which the roller jewel is interacting with the pallet fork, so is the portion of the "swing" of the balance where it is not truly free, but subjected to exterior influences. Lift angle contributes to escapement error (a complicated subject in itself), so a smaller lift angle is desired as a generality, but practical limitations related to manufacturing tolerances and the suitability of the resulting component systems for real world wear and tear usually keep the lift angle for high beat watches pretty close to 50o in practice.
The lift angle is manually entered into a timing machine in order to allow it to approximate an amplitude measurement. The timing machine is recording the escapement sounds and measuring how long it takes from the first to the last sound of each tick and then applying a calculation to that measurement based on the supplied lift angle to establish the angular speed of the balance and deducing from that the amplitude.
_john
question for the geeks.......
Folks, I have a question regarding amplitude of a watch which is used as a measure for the accuracy. I understand why the deviation of amplitude would represent accuracy but often the total amplitude seems to be used synonymously. As in "....change increa...
complicated
Hello JMan, Discussions of amplitude very often take place between two people with a less than completely thorough understanding of the subject. I once had a US watch industry executive (NOT my current employer) relay to me a story wherein he bragged to h...
Great and highly educating post, a true classic! ...
...thanks, John! I printed it and put it into my copy of Raymondin/Monnier, because your expalantion is so much easier to understand than the stuff written there. Regards, Marcus
Had to read it twice to make sure I was following...
Thanks for posting, very informative. I almost wrote "useful", but the only real use it has is to make me more aware of something I know very little about
Excellent post, John
Excellent post! As you say, amplitude is more of an indicator of good design and manufacturer, and I wonder if things like balance wheel inertia, "power curve" and reserve de marche would be better indicators of potential performance? If people can obsess...
What I'd love to see
I'd love to see curves like these published across entire power reserves....
Any chance of...
seeing the source data for that graph? Thanks for the posts, John. Informative and fascinating as ever.
it just looks like ~4000 rows of this
t [s] Rate [s/d] Amplitude [°] 2 12.8 290.0 4 12.5 290.0 6 12.3 291.0 8 11.8 291.0 10 11.7 292.0 12 11.8 293.0 14 11.5 294.0 16 11.3 295.0 18 11.7 296.0 20 11.7 296.0 22 11.5 297.0 24 11.7 298.0 26 12.0 298.0 28 12.0 298.0 30 12.1 298.0 32 12.2 297.0 34 1...
That's exactly..
...what I'd like to see You'd then be able to interrogate the data by manipulating the scales....but as you wrote, you'd need a fair few samples and a decent amount of background info before you could make any inferences....fascinating, though.
Per watch...?
I can see the use of this on a per-watch basis, but could you do it as a generalisation for all instances of a movement if it's so sensitive to adjustment, or are some production movements so consistent that it's feasible? nick
realistically? probably yes
Hi Nick, This is only a couple hours worth of data, so it's definitely only useful on a per watch basis and even then more for curiosity's sake. If you look at the total amplitude and rate trace over the full run-down of a watch it tells you a little more...
Cool
Hi John, I'd wondered if people used FF transforms for watch analysis. It's used for precision clocks, and I love the idea of long term studies of precision clocks such as various Shortts or the Littlemore showing the earth's natural resonant frequencies ...
Now that...
...is some interesting data. My FFT skills are almost dead, but that's the kind of analysis/tool I'd love to see more of. Brilliant work, John
I've thought about trying to put together some sort of
optical pickup for measuring rate & ampltiude myself. I've built home-made optical pickups for other purposes before using the light source and receivers from an old fashioned 'roller ball' computer mouse. Positioning the pickup to work reliably, and cali...
If you end up putting something like that together...
Send me the "how to". The I'd love to have something like that! _john
There's a chapter...
...in Robert Matthy's Accurate Clock Pendulums on both the sensors and the electronics for use on clock pendulums. The book itself is worth the read for the sheer pleasure (if you're that way inclined). nick
thanks for the book reference
Hi Nick or John, Are there any other books that you could recommend that explain the technical design aspects of a watch? In the vein that is being discussed in the currently? Thanks. J.
Daniels Watchmaking is quite good
The portions of the book specifically dedicated to these issues are pretty small (most of the book focuses on hand fabrication of watch components) but very informative. DeCarle's Practical Watch Adjusting is also an excellent resource. _john
Too much or virtually nothing...
If you speak French and have university-level maths/physics there's a set of four tomes from the EICN at le Locle (swiss technology university department specializing in microtengineering, with a sub-speciality of horlogery). Its' called Théorie de la con...
thanks.....
The Theory of Horology seems like the right kind of book. A bit on the expensive side though........ J.
Doesn't Brian Mumford..
already make an optical pickup for watches? and the interface for converting it to a usable signal with the micro set thingy? (Never seen one, touched one or used one, but like the ideas) Tom
Yes...
Brian does make them, but the cost is not negligible, and for some applications they're overkill. nick
iA quick look at his website...
suggests that the optical pickups available for the Microset machines are used for timing clock pendulums. Again, never actually seen one, only read about them online. There is one attachement he sells for vibrating bare hairsprings, but I can't immediate...
We are fortunate to have John here :-)
John, as always, wonderful and informative post. We learn so much here from you! Ken
Indeed. My thanks to John . . .
. . . for sharing his valuable holiday time with us. Gratefully, Art
Thanks for this, John!
A great exposition of a topic that was previously completely opaque to me. I now sense the fog lifting just a bit... Best, Gary G
appreciate the thorough response.......
John: Thanks for the education. I just finished my first read. But the topic is technical enough that I need to re-read your response to completely digest all the information you have presented. But it was my initial inclination that there was not going t...
Very informative.....
It's definitely a complicated subject, and you definitely educated me a bit more on it. Thanks. Dave
Hi John, I assume that you're an engineer or in a related field?
Great post and truly educational. If accuracy is needed, folks could get an atomic clock and think about how to mini it. Some things are better left with in-perfections, albiet not too much. cheers PAt
Thank you for an outstanding answer
At the same time you explained clearly the amplitude and the effect of a high beat. Great. And what about the "lift angle". How this relates, or not? Warm thanks. We need more posts of this caliber.
lift angle
Hello nilomis. Lift angle is the angle within which the roller jewel is interacting with the pallet fork, so is the portion of the "swing" of the balance where it is not truly free, but subjected to exterior influences. Lift angle contributes to escapemen...
Thank you
John, Just copy/paste your two answers on a single document that is now part of my small reference set. Great and direct answers. Cheers and enjoy your holiday
What an outstanding post!
Thanks John for taking the time to put it together. I am astonished how little I knew about the matter! Cheers, Magnus
Mr. Ohms....
John, Your response to this op is well reasoned and insightful, as usual. Real world experience has shown us that cross caliber comparisons based on amplitude alone are very difficult indeed. You and I have seen very stable modern movements with relativel...