Four Glass Crystal Regulator, Pendulum Issue

MarcosGraveyard

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Hi all,
I have a four glass crystal regulator with an unnamed French movement with a Mercury pendulum. The clock was purchased at a general auction and came to me for cleaning. I overhauled the clock and cleaned the case but couldn't get the clock to go slow enough even with the pendulum all the way to the base of the clock (there was nothing on the rear plate to suggest a pendulum length).
I disassembled the clock and calculated the bph to be 10080 and now have the clock running on a clock stand and keeping time but the pendulum Bob is now well below the threads for the retaining nut and is only being held in place by the upper screw on the Mercury holder. Needless to say this now makes the pendulum too long for the case.

So, I'm fairly satisfied that the movement is original to the case but I'm not so sure it's the genuine pendulum, I've found repair marks from at least 2 previous repairs.
How would I go about altering the cog of the Mercury Bob to shorten the effective length of the pendulum? Or should I be looking at a thinner suspension spring perhaps.
Any thoughts or advice would be greatly appreciated.

Thanks in advance.


IMG_20210526_193911.jpg IMG_20210612_121354.jpg IMG_20210615_000832.jpg
 

bruce linde

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how fast is it running? is it possible the mercury part is upside down, and the set screw you reference goes on the bottom, adding weight there and changing the center of mass in the direction you need?
 

Ralph

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Your suspension spring is probably two heavy/strong. I would think .0035 or so, would work... Is the movement marked on the back? It might validate the length needed, in pouces and lignes. If marked, it would be on the bottom of the rear plate, on either side of the pillar.

I assume your Brocot suspension adjustment is raised to expose the maximum amount of spring.

Ralph
 

Dick Feldman

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Look at the situation from a different slant.
You are fairly sure the movement is correct.
It seems the pendulum may be correct.
When you take one step deeper, the escape wheel is moving faster than design.
Could it be the verge is skipping a tooth once in a while or more often than once in a while?
Have you watched/listened to the escapement run? Have you put a machine on the movement that records BPH?
If everything looks correct with the pendulum (ie. matching hanger, etc.) I would look elsewhere.
Just a thought.
Dick
 
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MarcosGraveyard

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how fast is it running? is it possible the mercury part is upside down, and the set screw you reference goes on the bottom, adding weight there and changing the center of mass in the direction you need?
When set up in the case it was running +50 minutes a day. Thats why I took it apart again to do some teeth counting.
I'm pretty sure the Bob is setup correctly, with the pointy ends of the vials facing downwards. The pendulum rod has about 15mm of thread on the end and I would doubt that a set screw would be clamped onto it. As it is now the thread is inside the lower brass plate and I cannot fit the brass retaining nut.
 

svenedin

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Here's the pendulum of my French Four-Glass. They are a bit different but I note the screw in the middle is at the bottom of my pendulum and at the top of yours. Also is the suspension spring the right length and in the right position in the Brocot Adjuster?

IMG_7276.jpeg IMG_5880.jpeg
 
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MarcosGraveyard

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Your suspension spring is probably two heavy/strong. I would think .0035 or so, would work... Is the movement marked on the back? It might validate the length needed, in pouces and lignes. If marked, it would be on the bottom of the rear plate, on either side of the pillar.

I assume your Brocot suspension adjustment is raised to expose the maximum amount of spring.

Ralph
The only numbers are 457 on both the front and rear plate, but they look more like reference or model numbers.

Suspencion adjustment lengthened to the max.

IMG_20210615_211431.jpg IMG_20210615_211347.jpg IMG_20210615_205807.jpg
 

MarcosGraveyard

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Look at the situation from a different slant.
You are fairly sure the movement is correct.
It seems the pendulum may be correct.
When you take one step deeper, the escape wheel is moving faster than design.
Could it be the verge is skipping a tooth once in a while or more often than once in a while?
Have you watched/listened to the escapement run? Have you put a machine on the movement that records BPH?
If everything looks correct with the pendulum (ie. matching hanger, etc.) I would look elsewhere.
Just a thought.
Dick
The only machine I have is the Clock tuner app, and on it is running fine. There is no skipping of teeth occurring.

Screenshot_20210615_212352_com.athumbsoft.pendulumtuner.jpg
 

Ralph

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I agree, the pointy ends of the vials should point down.

From the side, the suspension looks long. How long is it. The properties of the pendulum length are measured from the point of flexure, to the center of oscillation (mass). A shorter spring would raise the point of flexure and give you a little bit. It might get you back in the case. Check Svenedin's image.

How thick is your suspension spring? I just measured a couple of replacement springs... .002-.0025", using my caliper. I'll check with a micrometer.... .0015-.0023".

Ralph
 
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svenedin

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I notice that the mercury in your glass phials appears oxidised. Are they sealed (mine are sealed)? If yours are not sealed is it possible they have lost mercury or mercury has been added at some point? Back to first principles; if the clock is running fast then then centre of mass of the pendulum is too high.
 

MarcosGraveyard

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Here's the pendulum of my French Four-Glass. They are a bit different but I note the screw in the middle is at the bottom of my pendulum and at the top of yours. Also is the suspension spring the right length and in the right position in the Brocot Adjuster?

View attachment 659115
Interesting, most photos I've seen have the vials the other way up. The set screw is purely to stop the Bob twisting on the rod so I would think it would be better clamping on the straight rod rather than the threads.
I see your top plate isn't seated all the way down on the brass washers.

The bottom plate on my Bob already has lead in it presumably to add weight while aiding the holding of the vials. You can also see how short the rod is now.

16237897262825283460628040424186.jpg
 

MarcosGraveyard

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I notice that the mercury in your glass phials appears oxidised. Are they sealed (mine are sealed)? If yours are not sealed is it possible they have lost mercury or mercury has been added at some point? Back to first principles; if the clock is running fast then then centre of mass of the pendulum is too high.
Vials are perfectly sealed as cam be seen in the previous photo.
 

svenedin

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Interesting, most photos I've seen have the vials the other way up. The set screw is purely to stop the Bob twisting on the rod so I would think it would be better clamping on the straight rod rather than the threads.
I see your top plate isn't seated all the way down on the brass washers.

The bottom plate on my Bob already has lead in it presumably to add weight while aiding the holding of the vials. You can also see how short the rod is now.

View attachment 659122
Sorry if I’ve added confusion and mine is actually the wrong way round. My clock keeps excellent time though and it came to me a long time ago set up like that. If your pendulum is correct surely it must be the suspension spring
 

Ralph

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Svenedin, I think your vial frame is upside down. I've never seen a French mercury pendulum with vial tips pointing up.
 

MarcosGraveyard

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I agree, the pointy ends of the vials should point down.

From the side, the suspension looks long. How long is it. The properties of the pendulum length are measured from the point of flexure, to the center of oscillation (mass). A shorter spring would raise the point of flexure and give you a little bit. It might get you back in the case. Check Svenedin's image.

How thick is your suspension spring? I just measured a couple of replacement springs... .002-.0025", using my caliper. I'll check with a micrometer.... .0015-.0023".

Ralph
The suspension spring is 0.8" long and 0.002" thick, that's with my digital vernier, don't have a micrometer I'm afraid.
 

svenedin

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Svenedin, I think your vial frame is upside down. I've never seen a French mercury pendulum with vial tips pointing up.
Ralph, Yes I noticed! It keeps good time as it is so I probably won’t fiddle with it.

Edit: I did just fiddle with it and the inside of the glass of my tubes tubes is really dirty if turned the other way up whereas the pointed end is totally clean. My conclusion is it has been pointed end up for a very, very long time and so it must now stay.

Also I did a quick search on a well known UK antiques website and the Four-Glasses I found had pointed end up.

I think my clock was always pointy end up.

Stephen
 
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MarcosGraveyard

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The rod is already short of the bottom of the Bob by 0.4" add another 0.2" for the retaining screw. It's going to have to be a very short spring :)
 

MarcosGraveyard

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On the Timesavers website the thinnest French Suspension Spring the do is #27 which is 17.5mm pin to pin and 0.04mm thick (0.7" and 0.0015")
 

bruce linde

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Ralph

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Timesavers product sounds good, Though I would have thought .002 would be good.

Ralph
 

svenedin

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i have three, all tips down....
Fair enough but mine has been tips up for so long that the mercury has blackened the glass so they cannot now be turned the other way up. Also the tip ends of the tubes are so clean inside that it appears they were never tip end down.
 

shutterbug

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It's possible that the mercury in the pendulum has been replaced with a much lighter "look alike" material. That would cause it to run way faster than designed.
 

MarcosGraveyard

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It's possible that the mercury in the pendulum has been replaced with a much lighter "look alike" material. That would cause it to run way faster than designed.
I don't think so, it looks very like mercury to me in the way it feels and flows in the vials. The pendulum itself weighs in at 70g (2.5 oz)
 

Ralph

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Could your Brocot suspension and bracket be assembled wrong.? Compare yours to Svenedin’s. Good design would put your suspension point, which is actually the flexure point of the suspension spring in the same axis as your crutch arbor. Yours seems way below. :???:

Just looking again at your suspension bracket again, how is the suspension spring upper end secured. I don't see a pin. Do you have a picture straight on, instead of side view?

Ralph
 
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Willie X

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How much shorter does it need to be?

1 or 2 mm may be doable but a half inch to long would indicate a wrong pendulum.

It could be as simple as the vials being replaced with improper substitutes.

The suspension spring would be a likely suspect too but a shorter one will probably give you 1mm, possibly 2mm at the most, assuming the one you have is extra long.

Good luck, Willie X
 

Ralph

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I found a suspension like yours in my junk. It works a little different then the usual Brocot suspension you encounter. I wonder if these are a way around the patent, or if they are just a variant. The typical suspension has the upper end of the suspension fixed, and a moveable set of chops travel up and down to alter the suspension's effective length. Yours appears to have the upper end of the suspension spring attached to a screw, which raises and lowers the spring itself through the aperture at the bottom of the suspension block.

You should be able to see the spring expose more or less of itself as you operate the adjustment. Does it do that. A standard replacement spring would have to be modified to work. Is it possible it unscrewed iitself and is just captured in the block.

IMG_20210616_114700611_HDR_(1600_x_1200).jpg IMG_20210616_114724042_(1600_x_1200).jpg IMG_20210616_114743994_(1600_x_1200).jpg
 

MarcosGraveyard

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I found a suspension like yours in my junk. It works a little different then the usual Brocot suspension you encounter. I wonder if these are a way around the patent, or if they are just a variant. The typical suspension has the upper end of the suspension fixed, and a moveable set of chops travel up and down to alter the suspension's effective length. Yours appears to have the upper end of the suspension spring attached to a screw, which raises and lowers the spring itself through the aperture at the bottom of the suspension block.

You should be able to see the spring expose more or less of itself as you operate the adjustment. Does it do that. A standard replacement spring would have to be modified to work. Is it possible it unscrewed iitself and is just captured in the block.
The suspension spring is pinned in the threaded rod, within the adjuster. It's a left hand thread and the cog nut is held in a groove between the two halves, rotating the cog exposes more of the spring through the block. This means that the bend point of the suspension spring is always the bottom of the brass block

IMG_20210616_151932.jpg IMG_20210616_152343.jpg IMG_20210616_151843.jpg
 

MarcosGraveyard

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How much shorter does it need to be?

1 or 2 mm may be doable but a half inch to long would indicate a wrong pendulum.

It could be as simple as the vials being replaced with improper substitutes.

The suspension spring would be a likely suspect too but a shorter one will probably give you 1mm, possibly 2mm at the most, assuming the one you have is extra long.

Good luck, Willie X
I fitted the shortest, lightest suspension spring I had, and with the pendulum almost touching the base of the case, it still runs 21 minutes fast/day. (10238 bph instead of 10080)
Perhaps the whole Brocot mechanism has been changed?
 

Willie X

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It probably had a smaller (or more squat) pendulum, although it does appear that you could get by with a suspension spring 2 or 3mm shorter? You could rig up something temporary as a test, and see for sure. Willie X
 
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Ralph

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Here's another movement with a similar suspension. Note how the bottom of the block, the "flexure" point ", is near in line with the anchor /crutch arbor. Is it possible, there is another mounting hole to raise the block on yours.

BTW, this block is marked L. Pigeon .

Ralph

IMG_20210616_175114617_(1600_x_1200).jpg IMG_20210616_175124997_(1600_x_1200).jpg IMG_20210616_175608254_HDR_(1600_x_1200).jpg
 

Uhralt

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With the clock gaining so much time my impression is that the movement is not original to the case and needs a longer pendulum. These French movements can often be easily replaced by similar looking ones with the same dimensions. Maybe this is what has happened in the past.
It is hard to say how best to remedy the situation. You could find a fitting movement with the correct pendulum length on places like ebay, or could try to add something really heavy to the very bottom of the pendulum.

Uhralt
 

MarcosGraveyard

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I've bought a selection Brocot backcocks on ebay, should be here next week, going to try and see if I can re-engineer something.
 

Ralph

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Ramblings…… what happens if you take the lead out out of the Bob frame? I don’t recall ever seeing that. Is it possible the tubes were replaced. If you removed the lead, I suspect the vials would be loose. …. But if you did that and shortened the frame, it would lower your CoO.

I was thinking, even if you managed to raise the suspension block, your pendulum would probably still be too short, based on your test stand observation. You might need a new rod, if you are successful.

As others have pointed out, it is possible there was a movement, or pendulum replacement. Any numbers on the case or pendulum to tie it to the movement numbers?

it still bugs me that your crutch arbor is so high, relative to the suspension spring. … or is it your suspension block is so low, relative ro the crutch arbor?

An extreme attempt, that may or may not give you enough change to solve your problem, would be to take the lead out of the lower frame, and maybe even open the holes to allow the tubes to seat deeper in the frame. You would have to shorten the two balusters. That should lower CoO. Enough??

A sidenote, movements marked 4 - 8 have a 10080 beat.

Ralph
 
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MarcosGraveyard

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I tried various configurations of the assembly of the mercury bob. I removed the lead from the lower plate (two thick washers of lead for each vial) I tried no lead, lead top and bottom, one lead on the bottom only, all to no avail. Still running 200+bph when at its longest in the clock.

I still need. to find about 1.5cm from somewhere. When I received the clock the pendulum was off the movement and the lower nut wasn't attached to the rod, it was just sitting in the base of the case. This got me thinking that perhaps the pendulum isn't the original. I got a spare pendulum from a slate mantle clock and after a small bit of adjustment I have it in the case with plenty of distance between the Bob and the base of the case and its running slow!!

IMG_20210618_115553.jpg
 

Uhralt

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I tried various configurations of the assembly of the mercury bob. I removed the lead from the lower plate (two thick washers of lead for each vial) I tried no lead, lead top and bottom, one lead on the bottom only, all to no avail. Still running 200+bph when at its longest in the clock.

I still need. to find about 1.5cm from somewhere. When I received the clock the pendulum was off the movement and the lower nut wasn't attached to the rod, it was just sitting in the base of the case. This got me thinking that perhaps the pendulum isn't the original. I got a spare pendulum from a slate mantle clock and after a small bit of adjustment I have it in the case with plenty of distance between the Bob and the base of the case and its running slow!!

View attachment 659446
Not all crystal regulators had a mercury vial pendulum. I have seen some with plain bobs or with sunburst bobs or a bob with a regulating screw in the middle of the bob. It seems likely that your clock originally had one of those pendulums. I would look for an old one of this style online. They do show up from time to time.

Uhralt
 

Ralph

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Marcos, more curiosity. What are the dimensions of the frame, holding the vials? What is the length of your pendulum? A smaller frame would lower the CoO. Lower levels of mercury in the tubes would lower the CoO.

.. and then , there's a another possibility , that the clock did not have a mercury pendulum. I've seen them with alternative fancy pendulums. Not often, but they are out there, and I thought they were correct. ( I just noticed Uhralt posting the same idea.)

I did check about 6-7 pendulums, and they were pretty consistent with the frame height, which I think would be the most important measurement. The mercury height varied in some.

Ralph
 

MarcosGraveyard

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Not all crystal regulators had a mercury vial pendulum. I have seen some with plain bobs or with sunburst bobs or a bob with a regulating screw in the middle of the bob. It seems likely that your clock originally had one of those pendulums. I would look for an old one of this style online. They do show up from time to time.

Uhralt
Already looking. :)
 

MarcosGraveyard

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Marcos, more curiosity. What are the dimensions of the frame, holding the vials? What is the length of your pendulum?
Frame height is 48.45mm
Overall pendulum length (hook to lower nut) 137mm
Weight 70g

The replacement pendulum bob is 34mm in diameter and the overall pendulum length is 145mm
Weight 65g
The replacement pendulum has a 7.5mm gap from its lowest point to the base of the clock.

IMG_20210618_152609.jpg
 

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