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explain drop and lock to me!

cazboy

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OK I have a hard time understanding the concept of "drop and lock" as it pertains to a recoil escapement. I found this youtube video http://www.youtube.com/user/Clockhistory#p/a/E72BCAB593FA9FC1/2/Q6hC31fEN2I which shows drop before and after adjustment. My problem is that I can't see any difference between the "before" and the "after".
What am I supposed to be looking at when I watch that video? Obviously I'm missing something.
 

wow

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The verge is slightly closser to the EW at the end of the video than it is at the beginning. I always adjust it as close as it will go without jamming. This gives a wide pendulum swing and best operation. Maybe there is more to it than that, but it works for me.
 

antiekeradio

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my first suggestion would be to remember that recoil escapement does NOT have any form of lock.

The drop as seen in the video is the amount of "free fall" the escape wheel makes after leaving the tip of the anchor at the right hand side.

if you would play this picture by picture, you would notice that when the tip of the escape wheel tooth is still barely touching the tip of the anchor on the right side, the tip of the next tooth on the left side is still some small distance away from the surface of the anchor on the left side.

As soon as the two tips on the right side loose contact, the next tooth 'drops' on the left side of the anchor.

Some amount of this free rotation (drop) is required to prevent jamming, however all of it is a pure loss of power transfer to the pendulum. So it should be kept at the lowest minimum practically attainable, as you see in the 'after' footage at the end of the clip.

Sometimes it is not enough to merely change the distance of the 2 pivot point to achieve small and equal drops, mostly in situations where serious wear or previour repairs have taken their toll. What to do in such cases is beyond this explanation, though :D
 

shutterbug

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The drop also produces the tick and tock that we hear, so a loud ticking indicates a lot of drop. The lock can be thought of as the point that arrests the drop. The lock has to be above the start of the angled pallet face on a dead-beat. Increasing the lock makes that distance greater, decreasing the lock makes it shorter.
In the video, you're looking at the curved "entrance" part of the verge. You can see that after the adjustment, the straight part of the verge has been bent just a bit. That 'raises' the verge closer to the wheel on both sides, so the physical position of the pivot point might have been moved a bit downward too to negate the effect on the exit pallet. It's hard to see that.
 
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antiekeradio

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the verge has not been bent; the cock on which the verge pin is mounted has been rotated slightly towards the escape wheel.

Lock cannot be described with the example video; post another one if you must explain lock. Again; there is no lock in recoil escapements! :D
 

shutterbug

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antiekeradio;499345 said:
the verge has not been bent; the cock on which the verge pin is mounted has been rotated slightly towards the escape wheel.
I'm not so sure, antie :) Look closely at the lower tooth position in relation to the body both before and after. To my eye, it has been lowered in the final adjustment. Could be wrong, but simply raising the pin would effect both entry and exit equally. I don't think that's what the poster was trying to show:?|
 

bangster

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Drop is the amount of free EW rotation between release of one tooth and capture of another. Measured in degrees of arc. Also viewed as the distance between the receiving pallet and the tooth it is about to receive at the instant of release.

Lock is the amount of overlap between pallet and tooth at the instant of contact —the "distance in" at contact.

Run is the distance of travel along the tooth after lock. It is caused by overswing (pendulum travel after lock).

The sequence is: Release — Drop — Lock — Run — Release — Drop — Lock — Run...

In a recoil escapement, the moment of lock is followed by recoil; in a deadbeat it isn't.

Every escapement has both lock and drop. And run, since proper overswing is necessary to healthy operation.

bangster
 

Willie X

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Caz,

I think that your question has already been well answered by others but if you do try the minimum drop, often suggested, be sure to apply light finger pressure to press the escape-wheel arbor and the pallet arbor (or saddle) together, while you are making this adjustment. This is essential for older clocks showing some wear. Going closer than about 10 thou on an older clock can be problematic.

Willie X
 

LaBounty

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Bangster's explanation is exactly correct but Antiekeradio also has a point...

The recoil escapement does not have separate locking and lifting planes like those found on a deadbeat escapement. It isn't really necessary to talk about "lock" in a recoil escapement since there either is some or the escape wheel freely rotates without being caught. The lock in a recoil escapement must occur on the lift surface. Lock in a deadbeat escapement must occur on the lock surface rather than the lift surface or there isn't lock even though the tooth is "caught".

Ref.
De Carle, Donald, "Practical Clock Repairing", pg. 15.
Goodrich, Ward L., "The Modern Clock", pg. 145.
 

bangster

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Thanks for the explanation, Dave. Now I see what Antiek had in mind: roughly..."no lock because no lock face". Point well taken. :Party:

bangster
 

Scottie-TX

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Semantics:
Semantics, and I'll not try to convince you there is lock on a recoil as first, I couldn't do it and second, it would be non-productive.
Like many call the anchor a verge. There is a verge. It is for a verge escapement that has recoil. But when someone calls an anchor a verge - I still know the part referred to is an anchor. Some call 'em gears. I know they're referring to wheels. Semantics.
Even the experts differ on lock and drop.
When discussing, "lock" of a recoil escapement, Penman calls it "bite".
Conover avoids giving it a name at all - only describes the event.
Balcomb calls it, "engagement".
Whatever you wanna call it. We all know of the event being described.
Experts differ on the meaning of drop - well - not the meaning but which is entry and which is called exit.
The most accepted is inside and outside - inside being entry and outside, exit.
The difference comes when one describes exit drop as the time and space preceding tick heard on exit face. Most would call this, "entry drop", i.e. the drop apparent after tooth leaves the entry pallet and until the tick of it dropping to the exit pallet.
So when discussing drops it is important to know how YOU regard it or describe it because exit drop is changed by a procedure different from that of entrance.
So; Semantics. O.K. There's no impulse lock but I UNDERSTAND the event you described.
 
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antiekeradio

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I have always understood lock in dead-beat escapements as the portion of the escape cycle where the escape wheel tooth travels along the locking surface.

the locking surface "locks" the escape wheel, as to say the wheel is kept stationary while the anchor moves into overswing, stops, and moves back until the impulse/lift surface.

So in my understanding of the semantics, the notion of "lock" is tightly bound to the bit where the anchor moves and the wheel doesn't.


In recoil escapements, the escape wheel is prevented from turning freely after each impulse, but it is no wonder the literature does not seem to have a specific name for this, since it is in essence nothing more than the next impulse cycle.

without overswing, a recoil escapement operates with impulse, drop, impulse, drop, impulse, drop and that's about it. The transfer of contact from one pallet tip to the other is all contained in the idea of 'drop' because without the next impulse angle
stopping the free motion of the escape wheel, the description of 'drop' is incomplete.

So, in my opinion is does go a little bit futher than 'what name to give to the beast' i.e. semantics. The locking phase in a dead-beat escapement makes it fundamentally different from a recoil escapement, and it seems ill-advised to use one and the same name (whether you call it lock, bite or engagement) for a phase that exist in one escapement type and doesn't in the other.
 

Scottie-TX

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Now we disagree and for good reason and not semantics.
lock in dead-beat escapements as the portion of the escape cycle where the escape wheel tooth travels along the locking surface
The DISTANCE the tooth TRAVELS along the locking surface is not lock but is a measurement of overswing or supplemental arc - the DISTANCE the tooth travels AFTER lock.
Amount of lock is a measurement of the distance from where the POINT of the tooth strikes the locking face to the shoulder of the impulse face.
We disagree again and again, not for reason of semantics:
without overswing, a recoil escapement operates with impulse, drop, impulse, drop, impulse, drop and that's about it.
We disagree again, for without overswing in a recoil escapement, there can be no impulse.
Impulse is provided by the reversing of the train, which if there's no overswing, the train is not reversed and there is no impulse.
 
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cazboy

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OK, I think I get it. But the difference in the before and the after in the video I referenced is pretty subtle. But once I really studied it I can see a difference in the amount of action the EW makes on the entrance.

If I knew how, I would like to make a video that is similar to that one but with circles and arrows and slow-motion, just to point out EXACTLY what is meant by drop.

And I now understand that there isn't really "lock" in a recoil escapement!
 

leeinv66

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Scottie-TX;499511 said:
Now we disagree and for good reason and not semantics.

The DISTANCE the tooth TRAVELS along the locking surface is not lock but is a measurement of overswing or supplemental arc - the DISTANCE the tooth travels AFTER lock.
Amount of lock is a measurement of the distance from where the POINT of the tooth strikes the locking face to the shoulder of the impulse face.
We disagree again and again, not for reason of semantics:

We disagree again, for without overswing in a recoil escapement, there can be no impulse.
Impulse is provided by the reversing of the train, which if there's no overswing, the train is not reversed and there is no impulse.
Yep, absolutely right Scottie!
 

antiekeradio

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Scottie-TX;499511 said:
We disagree again, for without overswing in a recoil escapement, there can be no impulse.
Impulse is provided by the reversing of the train, which if there's no overswing, the train is not reversed and there is no impulse.
If you interpret impulse as 'the power stored in the train as a result of overswing' ... yes

but that's not what impulse is, is it?

If I understood the translation of clockmaking terms as used in English correctly, impulse is the escapement phase in which there is power transfer between pendulum and escape wheel. LaB uses the term 'lift'.

During overswing, there is some power transfer from the pendulum to the escape wheel. After the dead point (return of direction of the pendulum) the power transfer goes the other way. As the escape tooth rides on the impulse face / lift surface of the anchor all the time during this part of the cycle, it seems of little use to characterise the path between the 'entry point' and the position of the tooth at dead point any different than the same path the other way round.

The situation in the hypothetical recoil escapement with no overswing would be that there is only power transfer from the escape wheel to the anchor, not the other way around. Why would you call this power transfer anything other than impulse, if the same action is called impulse when there is overswing?
-> posts merged by system <-
PS Cazboy, the difference is not that easy to observe. It is mostly noticeable if you keep your eyes on the spokes of the wheel. You can see them 'jump' a bit.

Since the camera is a bit closer (more zoom) in the 'after' shot, it is difficult to observe the actual change made. The text reads 'the verge will be moved closer to the escape wheel to reduce the entrance drop'. If you open up the video twice and pause the video at the beginning and at the end, you can compare the shape of the anchor more accurately. To me, it looks unchanged. The position of the oval anchor cock seems to have changed slightly from pointing towards 2 o'clock in the direction of 1 o'clock.
 

bangster

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cazboy;499519 said:
OK, I think I get it. But the difference in the before and the after in the video I referenced is pretty subtle. But once I really studied it I can see a difference in the amount of action the EW makes on the entrance.

If I knew how, I would like to make a video that is similar to that one but with circles and arrows and slow-motion, just to point out EXACTLY what is meant by drop.

And I now understand that there isn't really "lock" in a recoil escapement!
No, there really is "lock", i.e. depth of pallet into tooth at instant of contact. Both recoil and deadbeat escapements have THAT. The continued movement after that instant isn't Lock, but Run. Both escapements have that, too...at least if they expect to keep going.

What recoil has and deadbeat lacks is continuous ongoing (back & then forth) motion throughout the cycle. What deadbeat has and recoil lacks is a period when the EW is stopped dead. There may be a name for that period; I don't know what it is. It's during the front half of that period that Run occurs: pallet travels deeper along tooth, while tooth remains stopped. I'd call that the "dead period" rather than "lock" or anything else.

It's important to have a word for that initial depth, since it matters. The word is "Lock".

Sez me.

bangster
 

shutterbug

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Correct me if I'm wrong :) I consider the 'impulse' of a recoil the action following the reversing of the train when the stored energy created by the reversal pushes the pendulum in the opposite direction.
 

Scottie-TX

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I believe most would agree with that SHUT. I like ANTIEK's description as the pendulum imparting power to the train during recoil and the train returning the power to the pendulum during impulse.
You're not in the minority. I think many have problems wrapping their brain around, "drop".
Hope LAB won't mind this drag 'n drop of a sketch he provided and is currently at the sticky, "Clock Parts Terminology". Here: No circles - use your imagination but good arrows.
See the space between tooth and pallet just unlocked on left (entry) and the gap between the tooth and exit pallet? Those gaps are called "drop" and the measurement of them described as amount of drop. Ideally, drops should be minimum and equal.
Thanks LAB!
View attachment 3534
 
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Scottie-TX

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. . . . . and I don't wanna make it even more confusing but actually the wheel above is not in an ideal position for describing or measuring drop.
Wheel is turning clockwise and you note tooth has just departed locking face of entry pallet and onto impulse face. Observation and measurement of that gap is only when the upcoming tooth lands on the exit pallet. It is at THAT moment of exit lock when drop is observed and measured - same goes for exit - that gap between tooth and exit pallet when entrance locks.
 
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LaBounty

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Hey Scottie-

I'm pleased the diagram is getting used! Unfortunately, I had to take some latitude when creating a single diagram to show all of the important components of the escapement and the diagram blurs some of the definitions.

What is shown as exit drop is fairly correct but shown a bit large for illustration purposes. The entrance drop isn't correct since it can't be truly shown until the moment of exit lock. And the diagram shows nearly zero entrance lock when there should be some overlap of the escape wheel tooth on the lock face of the entrance pallet.

I too like Antiekeradio's description of power transfer and utilization. I made up some diagrams showing this in a recoil escapement for a lecture several years ago...


View attachment 3535


View attachment 3536


The concepts shown in the diagrams are exactly what Antiekeradio is describing but I've only been able to find this information as "strongly implied" in Goodrich's book.
 
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bangster

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I like the diagrams. Tell me about the difference between Impulse and Lift.

bangster
 

Scottie-TX

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Certainly we await LAB's reply but I see impulse as the tooth returning to the pendulum, the potential it was provided during recoil and lift the ADDITIONAL impulse provided by the surface of the pallet until it unlocks. That ( the amount of bite, engagement, lock or whatever you wanna call it) is why it is important to have maximum bite as the first portion is just a tradeoff and the remainder, the driving impulse that maintains pendulum motion. The lift provides the impulse necessary to maintain motion the same as the impulse face does in the deadbeat.
This is also why amount of lock on a deadbeat is unimportant, except in 400 day clocks, as amount of lock is unproductive. LIFT only is productive.
 
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LaBounty

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As Scottie says, it has to do with energy.

As the escape wheel tooth runs up the recoil pallet face following lock, the escape wheel backs up and adds potential energy to the system. When the anchor changes direction, this potential energy is converted into kinetic energy which impulses the pendulum. This impulse is necessary to keep the pendulum going since, in a recoil escapement, lift alone isn't enough.

To me, the difference between lift and impulse in a recoil escapement is that impulse utilizes the stored-up potential energy accumulated during recoil and lift doesn't.

Hope that helps!
 

leeinv66

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LaBounty;499747 said:
To me, the difference between lift and impulse in a recoil escapement is that impulse utilizes the stored-up potential energy accumulated during recoil and lift doesn't.

Hope that helps!
I'll get myself in trouble here as theory is my least favorite aspect of clock repair:eek: But, from my observations, both lift and impulse are achieved via the use of potential/stored energy David. The escape wheel is constantly influenced by the potential energy provided to the movement by it's power source! I see the recoiling of the escape wheel prior to the impulse phase as an added, secondary source of potential energy. Ok, so just how far off base am I:D
 

LaBounty

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Hey Peter-

You aren't off base at all! The potential energy stored in the power source is turned into kinetic energy which keeps the pendulum moving.

I think the difference between impulse and lift in a recoil escapement is how the kinetic energy is turned back into potential energy (recoil) and then becomes kinetic energy again (impulse). During lift in a recoil escapement, the energy stays kinetic.

Maybe it would be clearer to say, as Antikeradio suggests, that during recoil some of the energy is given back to the train by the motion of the pendulum. So, this energy doesn't come from the power source but from the momentum of the pendulum. It is then given back during impulse. The energy for lift comes up the train from the power source.

This is an extremely difficult topic which is probably why books on escapement theory avoid it :).
 

leeinv66

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LaBounty;499820 said:
Hey Peter-

You aren't off base at all! The potential energy stored in the power source is turned into kinetic energy which keeps the pendulum moving.

I think the difference between impulse and lift in a recoil escapement is how the kinetic energy is turned back into potential energy (recoil) and then becomes kinetic energy again (impulse). During lift in a recoil escapement, the energy stays kinetic.

Maybe it would be clearer to say, as Antikeradio suggests, that during recoil some of the energy is given back to the train by the motion of the pendulum. So, this energy doesn't come from the power source but from the momentum of the pendulum. It is then given back during impulse. The energy for lift comes up the train from the power source.

This is an extremely difficult topic which is probably why books on escapement theory avoid it :).
Thanks David, that makes a lot of sense! I can well understand why the books avoid this subject as I struggle to grasp it even when it is laid out in layman's terms as it has been here!

I tried to apply Newton's third law (For every action, there is an equal and opposite reaction) and soon realized there are so many interactions going on in an escapement that you would have to write a thesis just to explain them. Far too big a task for this self taught bodger:D
 

leeinv66

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LaBounty;499844 said:
If you really want to exercise your brain read Rawlings' "The Science of Clocks & Watches" :).
Yes David, I know the book and my brief encounter with it reinforced my dislike of theory:D However, I did manage to gain snippets of valuable information in amongst all the mathematical formulas and physics (most of which were waisted on me). On the bright side though, I did manage to turn a profit when I resold it on ebay:D
 

RJSoftware

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To me it's all about how far to set the anchor depth. And that's all there is to it really, for me that is.

I don't think it really effects the aspect of time keeping efficiency. More to do with longevity of the time piece. I say this in the consideration that a recoil probably produces more wear (from recoil action) than a dead-beat.

The most interesting thing about all of this is the impulse.

To think that the power supply of an average 30 hour clock spring could supply enough energy to maintain even the largest of pendulums such as that of Big Ben.

Yes, that is what I said...! :)

You see, gravity is really an equal force upon all things. For example, when you drop a feather off the side of a building and a bowling ball, they would both land the same time...
..
..
..:eek:
..
..:eek:
..
..
..:eek:
..
..
..:eek:
..
..
..:}(boing...!)
provided you did this in a vaccume chamber. :confused:

So, it is then also true that the little iddy biddy smidgen of impulse power is same relativley speaking to push the pendulum of Big Ben as it is to push the pendulum of an ordinary 30 hour clock.

It is the timing of the impulse that keeps the pendulum motion from decaying. Right after the moment inertia has changed direction.

So, whenever I see a post where someone talks about changing the pendulum bob weight, I realize that this concept has not taken hold.

Also, what you may come to realize too is that if you have difficulty with calculating the pendulum length for any reason, just make a dummy pendulum.

Weight does not matter...! So use a piece of coat hanger wire and aluminum foil bob. Slide the bob till it keeps time fairly well and there you have your length...!

Now some of you might be scratching your heads a bit. Your not quite buying all this buisness.

But the question is -is this ALL real or is RJ jerking your leg somewhere?

RJ :Party:
 
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Dave D

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I have Dave LaBounty's video on recoil escapements and found it very informative. All of his videos that I have ordered were well done and worth every penny.
Dave Dazer
 

Dave B

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RJSoftware;499952 said:
You see, gravity is really an equal force upon all things. For example, when you drop a feather off the side of a building and a bowling ball, they would both land the same time...

Weight does not matter...! So use a piece of coat hanger wire and aluminum foil bob. Slide the bob till it keeps time fairly well and there you have your length...!

Now some of you might be scratching your heads a bit. Your not quite buying all this buisness.

But the question is -is this ALL real or is RJ jerking your leg somewhere?

RJ :Party:
True, but only to a point. When you use a coat hanger for a rod, and a wad of chewing gum foil as the bob, you change the center of gravity to a much higher point than a light rod and (relatively) heavier weight would have. So, changing the weight of the bob does have an effect, but it is not because the heavier bob drops across the arc at a faster rate. It is because the center of gravity (or, rotation, if you prefer) has changed. (I don't like to think of it as a center of rotation, because that confuses my head.) :p
 

Scottie-TX

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"Ditto" again. Of all he wrote - and this ain't "let's pile up on DRJAY" - but it's about the dummy pendulum I also took option.
First, I wouldn't make a dummy pendulum. I'd make a smart one. Reason the tinfoil bob doesn't make a good bob is as DB wrote. It is too light. It is too unlike the bob to be used. Most any bob would be heavier than a ball of tinfoil so would incorrectly suggest a longer pendulum. The test pendulum should have a bob of similar dia. and weight of the one to be used. No reason to not even use the bob that will be permanent for the most accurate test.
 

RJSoftware

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Well, you know how it is, it just depends on how big you make your aluminum foil balls...

Hmmmmmm, :p
RJ
 

leeinv66

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provided you did this in a vaccume chamber.


RJ, as I have never lived in a vacuum chamber, I'll have to take your word for what goes on in there;)
 

bangster

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leeinv66;500060 said:
provided you did this in a vaccume chamber.


RJ, as I have never lived in a vacuum chamber, I'll have to take your word for what goes on in there;)
Well, for one thing it's very quiet. :D
 

antiekeradio

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All I know is that living in a vacuum makes your blood boil. In that aspect there is an analogy to some clockmaking theoretical discussions :D

The coloured diagrams are useful to visualise the different types of energy flow, and do conform to what seems to be happening in theory. But it seems rather confusing to put 4 names on one single tooth-surface interaction, moreover when only 3 of those actually happen.

The surface in the "lock" phase is never travelled, as the EW tooth only lands on the surface at the red/blue borderline.

It seems that it would be simpler, clearer, and more in line with the study book terminology if the entire sequence of processes as illustrated in the drawing with recoil-impulse-lift would simply be called 'the impulse phase' Where recoil during the overswing is a special type of impulse, in which there is some energy transfer from pendulum to EW.

With the pallet moving upwards, there is absolutely 0 difference between the phases that are identified in the drawing as impulse and lift. The pendulum has no memory where it was at time of drop when it was moving the other way.
 

RJSoftware

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antiekeradio;500076 said:
The surface in the "lock" phase is never travelled, .
Actually, think I have seen some lock surfaces that draw the palette inward during the lock process. So, that would be a form of travel, true?

RJ
 

antiekeradio

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We are still discussing the existence and terminology of "lock" in recoil escapements.

Of course, there are many other types of escapement where locking takes place, with or without true deadbeat operation. Most pin pallet escapements have some undercut to the locking surface.
 

bangster

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Antieke, I'm not sure whom you are arguing against. The terminology has been accepted long enough for Goodrich and DeCarle to have used it in their books. Are you suggesting that they were somehow mistaken?

bangster
 

Scottie-TX

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I don't have DeCarle or Goodrich. Could you quote or paraphrase them on recoil whereas, "lock" is concerned in recoil?
 
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Scottie-TX

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Thanks BONG!
KOOL stuff. Other than LAB, I've never read another author refer to lock on a recoil. I agree on the term, of course, but am not opposed to those who eschew the word. Again semantics and I have no problem understanding and accepting what others call it. Thanks!
 

antiekeradio

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Hmm, yes, it is semantics after all I guess.

it's a bit confusing to use the same terminology for the "lock" in escapements with, and without special provisions to extend the "locking" of the escapement.
 

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