Talk:Anchor escapement

Account of this edit was suspended for vandalism and there are some unfinished sentences but has added what appears to me some good info http://en.wikipedia.org/w/index.php?title=Anchor_escapement&oldid=212238546

Anchor and Verge escapement

The article states that the way to tell if a clock has an Anchor escapement is to observe the second hand. If it moves bacwards a little during each cycle then the ascapement is an Anchor escapement. However, the article on the Verge escapement says that the same observed bacward movement shows that the escapement is a Verge escapement. Thus the method must be wrong (on both articles). 20.133.0.13 (talk) 08:34, 28 August 2008 (UTC)

The article says that is the way to find out if a pendulum clock has an anchor escapement. Both the verge and the anchor escapements have recoil, so their second hands move backwards. But the anchor escapement is used only in pendulum clocks, while the verge is used in antique pocketwatches (and some very rare early pendulum clocks, which didn't have second hands anyway) So if a pocketwatch shows recoil, it is a verge type, while if a pendulum clock has it, it is almost certainly an anchor type. So I think the articles are correct. --Chetvorno^TALK 17:39, 28 August 2008 (UTC)

Anchor vs. deadbeat

I'm having trouble seeing the difference between the anchor and the deadbeat. They are a slightly different shape; is this really the entire difference? --Doradus (talk) 01:16, 21 September 2008 (UTC)

Yes, it is. The image of the anchor escapement is pretty bad, and maybe the description of operation is too abstract. Thanks for bringing that up.

Pendulums keep the best time when they are given a brief push once every swing and are allowed to swing freely the rest of the time, just like a playground swing will have the most regular motion if it is pushed briefly. That is what the deadbeat does. While the escape tooth is on the locking face, which is during most of the pendulum's swing, the escapement is dead, and doesn't affect the pendulum's motion. In the anchor, because its pallets are angled, whenever a tooth is pushing against a pallet (which is constantly) it is pushing and pulling the pendulum back and forth. So the pendulum's period is more affected by the force of the escapement. A slight change in friction of the pallets, or a decrease in force as the clock's mainspring runs down, changes the pendulum's period. --Chetvorno^TALK 05:10, 21 September 2008 (UTC)

Wow, this article has had quite a flurry of activity in the last few days. Looking good! --Doradus (talk) 22:51, 24 September 2008 (UTC)

Mostly just breaking the large chunks of text into sections. It wasn't very readable as it was. --Chetvorno^TALK 08:40, 26 September 2008 (UTC)

I made an animated SVG image of a moving anchor escapement that illustrates well how it works. I'd like to add it to the article, but every time I try to upload it to Wikipedia, the database rejects it. --Chetvorno^TALK 08:44, 26 September 2008 (UTC)

If the image of the anchor escapement was mirrored left-right it would be consistent with the other two images on the page and the difference would maybe be more apparent?Mumiemonstret (talk) 17:13, 10 December 2008 (UTC)

Great idea. I replaced the image in question (which wasn't very good anyway) with one turning the same direction as the deadbeat image. Hope it helps. --Chetvorno^TALK 18:29, 10 December 2008 (UTC)

I suspected that this might be the reason for the name "deadbeat", but this isn't stated anywhere in the article. If there's no objection (and nobody does it sooner), I'll add it in a few days.

IMHO it would be helpful to understand the difference between anchor and deadbeat if there was a simple drawing overlapping the shapes of the pallets and escapement teeth. Perhaps some force vectors might help too.

What happened to Chetvorno's SVG? —Preceding unsigned comment added by DGerman (talk • contribs) 15:49, 5 April 2009 (UTC)

"When the deadbeat was invented, clockmakers initially believed it had inferior isochronism to the anchor, because of the greater effect of changes in force on the pendulum's amplitude." -- This is TRUE. Deadbeat escapements are very rarely found in spring-driven movements. The only way to solve the mentioned problem is to apply a constant force, as provided by a weight-driven clock. Coiled springs do not give constant force at all, which makes the deadbeat escapement very inaccurate. --94.208.42.4 (talk) 11:08, 29 October 2009 (UTC)

You are right that anchor escapements were preferred over deadbeat escapements for early spring driven clocks, but the reason was more complicated. It was not that anchor escapements were more accurate, but that the inaccuracy (lack of isochronism)of the anchor compensated for the inaccuracy of early pendulums. Pendulums swing slightly faster as the width of their swing decreases, so if less drive force is applied to a pendulum it will speed up. However a smaller drive force causes the anchor escapement to slow down. In early clocks these two errors roughly cancelled each other out. so as the mainspring ran down and exerted less force the rate of the clock would remain the same. But the deadbeat is definitely the more accurate escapement. --Chetvorno^TALK 18:19, 20 November 2009 (UTC)

Recent addition

Fascinating information about the Tekippe clock, Boettcher, and the cancellation of circular error was an important point to add. It should probably be mentioned that, at least by the 19th century, clockmakers were aware of the cancellation, and used it in anchor regulators until the deadbeat took over. I'll see if I can find a source. --Chetvorno^TALK 17:02, 22 May 2014 (UTC)

Earliest implementation

The article states that the earliest invention of the anchor escapement was in 1657, in Britain. However, the first pendulum clock was built in the same year, and made use of a verge escapement. I find it hard to believe that the invention could have followed so soon, especially because there was only one person (Salomon de Coster) who was allowed to build pendulum clocks as per Huygens' patent. The sources given do not seem very professional to me either, I suggest further research is done in this direction.--145.118.160.65 (talk) 12:10, 18 May 2009 (UTC)

According to Chapman, Hooke, an inventive genius, invented the mechanism around the 1660s but typically moved on to other things and failed to secure rights or develop it. William Clement, a clockmaker, probably independently invented it in 1671 and, being more practical, saw the potential and began to build clocks using it, the first grandfather clocks. When they began to make money, Hooke disputed Clement's priority, saying he had demonstrated the anchor escapement before the Royal Society in 1666. I don't know whether Clement received a patent for it, and whether Hooke formally challenged the patent in the courts, maybe someone could find out. --Chetvorno^TALK 17:25, 22 May 2009 (UTC)

Backlash

The use of the term "backlash" on this page is not how I as an engineer understand it, or how it is explained in the referenced Wiki page.

Backlash is the name of an effect that can result from small imperfections in the way that gears or screws fit together. If components don't fit together exactly, then when a motion is reversed, backlash can occur. For example, if a screw is being turned to advance a nut, e.g. in a lathe cross slide, and the screw is then turned in the opposite direction, the screw may have to turn a way before clearance between the thread of the screw and those of the nut is taken up and the nut starts to advance in the opposite direction; that is backlash. Backlash can be prevented by either very precise engineering, such as in a micrometer, or by loading the parts so that they always remain in contact, such as if a spring is used to hold a screw and nut together.

In a clock the components are held together by the force of the weights or the mainspring. During recoil the train reverses a little and the weights are lifted slightly, or the mainspring pushed backwards a little, but the same faces of the teeth on the wheels and pinions remain in contact with each other, they are held in contact by the force of the weights or mainspring, and therefore backlash in the sense that I understand it does not occur.

David.Boettcher 18:04, 23 May 2014 (UTC) — Preceding unsigned comment added by David.Boettcher (talk • contribs)

I agree, the loaded going train can't have backlash. It's also unsourced. --Chetvorno^TALK 18:17, 23 May 2014 (UTC)

The "Disadvantages" section list two major disadvantages of the recoil escapement, friction and recoil, which the next section says were remedied by the deadbeat escapement. However, it is not clear how the deadbeat remedied the friction, it is still a frictional rest escapement and the escape wheel teeth scrape along the pallets during the supplementary arc in the same way as the recoil; simply saying that they are just "resting lightly" on the pallets is not a convincing argument. Unless the deadbeat requires significantly less driving force than the recoil, then the friction must be similar. I don't think that the fact the recoil escapement reverses the train would make a significant difference in this either, it is only lifting slightly the weight that is driving the train and I wouldn't have thought that inertial effects would be significant. It is also not clear that the lack of recoil in the deadbeat is that much of an improvement, it makes it significantly less isochronous in "real world" escapements, those that do not fulfill Airy's condition, which is all those actually built as far as I can make out. David.Boettcher 19:27, 25 May 2014 (UTC) — Preceding unsigned comment added by David.Boettcher (talk • contribs)

The article didn't "....list two major disadvantages of the recoil escapement, friction and recoil...", it said that the anchor escapement was a "frictional escapement". This is a historical term whose meaning was explained in the article; it means the oscillator is disturbed by the escapement over its whole period 1 The article didn't say friction was the problem. The problem with the anchor is exactly what the article says it is; the drive force is applied during the whole cycle, especially the recoil period. "...the fact the recoil escapement reverses the train" certainly does "make a significant difference". It makes a huge difference where in the pendulum's cycle the disturbing force of the escapement drive is applied. The Airy condition says that even a large impulse force applied to a harmonic oscillator as it crosses its center equilibrium point theoretically has no effect on the phase (period). Conversely, a tiny force, or change in force, applied at the end of its swing, where it is moving slowly and spends most of its time, can cause a huge change in phase. Although the anchor/pendulum combination may be made isochronous for changes in "average" drive force, it is very affected by "transient" force changes during the sensitive recoil period. There are many causes of disturbing forces in the complex mechanics of recoil. A big one is the oil drying up. There is static friction when the train reverses. Experience has shown that it is not good to have the harmonic oscillator coupled to a gear train during the sensitive extremes of its swing; that is the concept of a "detached" escapement.

The advantage of the deadbeat is that the only escapement force on the pendulum during the outer part of its swing is friction. This is less than the recoil force by a factor of at least μ (the coefficient of friction), it is substantially constant, and unlike the recoil force its effect is at least partially self-cancelling; during the outward swing its effect is to decrease the period, while during the inward swing it increases the period.

The clockmakers of the 19th century knew all about the anchor's cancellation of circular error, and made use of it. The consensus, then as now, was that the deadbeat was a better escapement. If it wasn't, why was it adopted in regulators? Rather than depend on the fussy cancellation of two nonlinear effects in the anchor, with its complex interaction with the drive train, clockmakers found it better to start with a more inherently linear, isochronous escapement, the deadbeat. The pendulum still had circular error, but that could be reduced by designing the deadbeat with a smaller swing θ. Because circular error scales as θ², cutting the amplitude in half cuts circular error by 4. They also compensated for circular error with auxiliary devices like magnets.

The article also doesn't say that all the "disadvantages" of recoil that were "remedied" by the deadbeat were in accuracy. There is also the increased gear wear caused by reversing the train, and the teeth digging into the pallets' surface. --Chetvorno^TALK 20:03, 26 May 2014 (UTC)

Due to the above points, the added paragraph on the Tekippe regulator is misleading and needs to be rewritten with a more WP:NPOV. Although the Tekippe example is an important addition, the paragraph puts WP:UNDUE emphasis on it. The fact that a single experimental anchor clock built with 21st century technology beat 19th century deadbeat regulators doesn't make the anchor a better escapement. The paragraph needs to be replaced with a good explanation of circular error and the anchor's cancellation of it, including that 19th century clockmakers knew about it and utilized it, yet found the deadbeat to be a better escapement for precision regulators. --Chetvorno^TALK 08:13, 8 June 2014 (UTC)

Seconds length

The 1669 measurement without reference is given as 39.1 inches (990mm). But 39.1 inches is not equal to 990mm. I don't know which is right or how to look it up. The 1672 measurement of 39.09 inches (993mm) converts ok, but I could'nt access the book on my phone. Perhaps someone more knowledgable can fix this. Thanks!24.156.181.13 (talk) 16:48, 19 December 2016 (UTC)