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Interesting French escapement ca. 1730

rstl99

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I just acquired a cartel clock from France, ca. 1730. Made by a famous maker of the time. His name is on the dial and the movement. The movement is in excellent condition and ticks nicely.

I'm trying to identify the kind of escapement the clockmaker used. It looks like a Graham deadbeat (which was relatively new at the time, but known about in France). But the shape of the teeth are different. I've looked through all my escapement books and can't find something exactly like this one.

I attach a couple of photos. The plate shown is the dial plate (right next to the escapement). And the escape wheel in the photo turns counter-clockwise from the angle shown (clockwise, if you were looking at the movement from the front (dial) side. So the sloped-down portion of the teeth are leading in the rotation.

Any ideas on the escapement type?
Thanks
Robert

IMG_0388.JPG IMG_0389.JPG IMG_0391.JPG IMG_0392.JPG IMG_0393.JPG
 
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Chris Radano

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Alex K

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Congratulations with this nice clock Robert!
I feel this is a Graham but viceversa - working palets are on EW and 2 teeths are on "anchor"... why not..
 

gmorse

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Hi Robert,

That's some very crisp work!

I think you'll see some slight recoil when it's running, because although the lift is mostly on the escape teeth, the shape of the pallets suggests that it isn't completely dead-beat, especially the entry pallet. True dead-beat pallets are circular, but the locking faces on these two are different; the entry is convex and the exit is flat.

Regards,

Graham
 

Chris Radano

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On a Brocot escapement, the escape wheel teeth are curved concave at the tips, the entry pallet is semi circular and the exit are flat. But the general shape of the teeth on this are similar to the Brocot. Also the French origin.
So it could be considered a club foot escapement?
 
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rstl99

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Thanks to all of you for your thoughts on the escapement. Once I take the movement apart for cleaning servicing I'll be able to take a closer look at the pallet configuration, as per Graham's thoughts.
I found this diagram in Thiout (1741) which confirms the shape of the teeth are indicative of Graham's design, at least as the French understood or interpreted it.
This maker was known as an innovator so may well have tinkered with the original design for his own purposes.
I'll also attach a couple of photos of the lovely movement, which I had the occasion to photograph yesterday.
Cheers.
Robert

IMG_7033.JPG
 
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rstl99

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A couple of quick photos of the movement from my new clock. I'll place many photos of the clock in all its aspects on my website/blog, as I proceed with disassembly, inspection, and conservation/repair activities over the next several weeks.

I'll certainly be back here with findings, and to seek insights of learned members, as I uncover aspects and secrets of this historically interesting clock.


Robert

IMG_0391.JPG IMG_0393.JPG IMG_0400.jpg
 
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jmclaugh

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An interesting escapement which looks to only span 4 teeth.
 

rstl99

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An interesting escapement which looks to only span 4 teeth.
I hadn't thought about that Jonathan, but indeed the span is very short compared to Thiout's diagram and most diagrams of Graham's escapement in the literature. Le Roy was quite the innovator, as his adaptation of Graham's design (which was only a few years old when he built this clock) illustrates.
 

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I was thinking, it could have inspired Roskopf’s pin pallet escapement.

Ralph
 

rstl99

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I'm not very familiar with Roskopf, but he no doubt inspired himself from many things that came before him.
 

Ralph

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I'm not very familiar with Roskopf, but he no doubt inspired himself from many things that came before him.
He used the tooth form to impulse static pins on a lever (anchor). Your escapement has pallet faces similarly impulsed by the tooth. In a Brocot escapement, the cylindrical surface of the jewel provides the impulse. It is sort of flipped.

Here’s a good article on escapements.

https://theindex.nawcc.org/Articles/Headrick-Anchor.pdf

Here’s an animation of a Brocot escapement.

Brocot Clock Escapement in Motion

Here.s a Graham’s escapement animation.

Graham Clock Escapement in Motion

I haven’t found a good animation of a pin pallet escapement, but if you operate your escapement, I think you will see it is not a form of Brocot’s.

Here’s a video of a pin pallet/ pin lever in action.


In Graham’s escapement, the tooth form is secondary, and only the tip is important. The rest of it it is for strength and non- interference. In your escapement, the tooth form is paramount

IMHO Ralph
 
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Alex K

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He used the tooth form to impulse static pins on an anchor. Your escapement has pallet faces impulsed by the tooth.
I don't agree, more looks like tooth pushes edges of the anchor. So this is flipped Graham. It fould be flipped Broccot if teethes was rounded on the ends but it is not the case.
I could say that this close to Swiss type... but still no, this is poor Graham...
Also there could be really no recoil beacause teethes on EW can have rounded sides for "round sliding"... and even if not - it is really neglegible.
I think this is not best solution since only two sharped faces works all the time compare to classic Graham where 30 teethes works and resource is more stretched.
imho))
 

rstl99

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Thanks for all the great information links, Ralph!
Regards,
Robert
 

Ralph

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Alex, then I guess you're right about not agreeing. ;)

I'll stand pat.

If Robert indicates the escape wheel's direction during it’s operation, that will make things more clear. My thoughts are based on the assumption that the escape wheel as we view it in the pictures will rotate counter clockwise, when in action. If that is the case, that will eliminate Graham’s and Brocot’s escapement or their variants as considerations.

If the EW rotates CW, then my thoughts are invalid.

Pictures of the anchor to clearly show the pallets, would also aid in speculation.

Ralph
 

Alex K

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Ralph, I just not agree with You if you see there pallet faces. Theare no pallet faces on the anchor). That's why this is pure Graham in nature.
And for sure this works only if EW goes teethes faces forward.
 

rstl99

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If Robert indicates the escape wheel's direction during it’s operation, that will make things more clear. My thoughts are based on the assumption that the escape wheel as we view it in the pictures will rotate counter clockwise, when in action. If that is the case, that will eliminate Graham’s and Brocot’s escapement or their variants as considerations.

If the EW rotates CW, then my thoughts are invalid.
Please see my text above, which stated which way the EW was turning. To make things clearer, I've rotated the photo so you can see the EW and escapement more naturally (from the top), and as I wrote above (copied below), the EW indeed turns "counter CW".

I attach a couple of photos. The plate shown is the dial plate (right next to the escapement). And the escape wheel in the photo turns counter-clockwise from the angle shown (clockwise, if you were looking at the movement from the front (dial) side. So the sloped-down portion of the teeth are leading in the rotation.

jlr ew.jpg
 
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Uhralt

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Please see my text above, which stated which way the EW was turning. To make things clearer, I've rotated the photo so you can see the EW and escapement more naturally (from the top), and as I wrote above (copied below), the EW indeed turns "counter CW".

I attach a couple of photos. The plate shown is the dial plate (right next to the escapement). And the escape wheel in the photo turns counter-clockwise from the angle shown (clockwise, if you were looking at the movement from the front (dial) side. So the sloped-down portion of the teeth are leading in the rotation.

View attachment 639771
I read in the German translation of the books of the famous French clockmaker Saunier that this kind of escapement was intended to minimize friction, pressure and wear by distributing the load equally to the escape wheel teeth and the anchor pallets. With the pointed "regular" escape wheel teeth all the pressure and wear is at the tip of the teeth and where they touch the pallets. With the larger surface of this type of escape wheel, the pressure is distributed on a larger area and impulse is given both by the angle of the teeth tops and the pallets.

Uhralt
 
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rstl99

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Thank you Uhralt, that sounds like a very rational explanation by Saunier, which I'll research deeper in his book (thank you for typing the description). [Note: in reading Saunier's lengthy description of escapement aspects in his Traité, I am reminded of the depth of knowledge that he possessed and shared at great length to whoever was interested to read.]

An antiquarian horologist in France that I showed the picture to thought he could see faint traces of tin applied to the escape wheel teeth. He said it was a practice by some repairers of the past, to prevent excessive wear on the EW teeth faces, tin being a bit "self-lubricating", which was useful since the oils used at the time this movement was made (early-mid 1700s) were not terribly performant or long-lived. Also he said that tin was resistant to atmospheric changes (dry/humid, hot/cold), which was practical since these clocks were placed in environments (rooms in old castles and estate houses) where the environment could not be as well controlled as in our modern dwellings. I felt his hypothesis was deserving of consideration, so I share it here.
Cheers.
 
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Uhralt

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Thank you Uhralt, that sounds like a very rational explanation by Saunier, which I'll research deeper in his book (thank you for typing the description). [Note: in reading Saunier's lengthy description of escapement aspects in his Traité, I am reminded of the depth of knowledge that he possessed and shared at great length to whoever was interested to read.]

An antiquarian horologist in France that I showed the picture to thought he could see faint traces of tin applied to the escape wheel teeth. He said it was a practice by some repairers of the past, to prevent excessive wear on the EW teeth faces, tin being a bit "self-lubricating", which was useful since the oils used at the time this movement was made (early-mid 1700s) were not terribly performant or long-lived. Also he said that tin was resistant to atmospheric changes (dry/humid, hot/cold), which was practical since these clocks were placed in environments (rooms in old castles and estate houses) where the environment could not be as well controlled as in our modern dwellings. I felt his hypothesis was deserving of consideration, so I share it here.
Cheers.
I think the escapement is shown here in table 11 as Fig. 13. Interesting to hear about the tin. I haven't heard that before. I have also read that some clockmakers drilled tiny holes into the tips of the escape wheel teeth to hold some oil, so lubrication at this area was obviously a concern.

Uhralt Saunier.JPG
 

rstl99

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Thanks yes fig 13 is similar to the escapement in my clock.
Tiny holes indeed!
And I know this is a well known fact but wasn't to me before I heard it, that the brass escape wheel teeth will eventually wear down the steel pallets of the escapement. I have an old ca. 1750 English tall clock where some steel has been applied to the worn faces of the pallets, due to that effect. Of course the reasoning is that many EW teeth are wearing on just a couple of escapement pallets. But in time, I presume the EW teeth must also wear down and require replacement of the wheel.
Cheers.
 

Chris Radano

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Somewhere I read the English clockmakers complained Brocot escapements were difficult to keep lubricated. I imagine this one, too.
Yours survived since 1730. Steel on brass, most likely they just stop running, opposed to wearing down.
 

Ralph

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Robert, the closest example of your escapement, is shown as figure 13, on plate XII. It is described in section 976. That example is slightly different then yours from what I can see. On yours, the lift appears be mostly, if not all, provided by the EW teeth. I don’t believe your pallets have impulse faces.... it might just be the view provided.

Your escapement shall remain nameless. ;)

Regards, Ralph
 

rstl99

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[QUOTE="Ralph, post: 1442641, member: 524"
Your escapement shall remain nameless. ;)
[/QUOTE]
Thanks for the figure and paragraph numbers.
Maybe I should call it the "Julien Le Roy" escapement, after the actual clockmaker who made it!
 

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