That's Rolez not Rolex
Last October I saw a local craigslist offering.
Scott and I went over to check it out.
30-ish Matt and his wife lived in a small bungalow in PG. He was running late. We were in no rush. Nice people.
He said the clock "ticked but didn't keep good time."
The thing is solid slate. Maybe 30 pounds worth. Glass bezel missing. A little scuffed but overall looked nice. No maker's label but peering in the back I noted a few things.
Firstly, it wasn't keeping time because it had no pendulum. Matt wasn't aware it needed one.
OK.
A quick glance saw the distinctive round shape and classic elements of a French movement and there was a maker's mark.
Jules Rolez Limited Paris. Not Rolex.
We haggled. I knew this beastie needed some work but suspected I could make it run.
He wanted $140. Settled on $60.
Took her home and put her on a shelf for a few months. Didn't do much clock stuff in the cold weather.
Spring has sprung and I'm back at it. The new bench didn't hurt either. So dusted the old girl off and found an appropriate pendulum on eBay.
Appropriate.
Ahem...
Standard french pendulums are a bit more complicated than those found in your typical American antique clocks.
The French version has a double hook that goes over a pin on the suspension spring.
The weight of the pendulum bob tends to be standardized on most mantle styled French clocks. However many clocks, especially French ones, are quite fussy about the length of the pendulum.
When I bought my cuckoo last summer there was a second pendulum in the box of parts. From an entirely different clock. It was a French pendulum.
Let's try it.
Nope. Was way too slow even with adjustments.
Actually I guessed it wouldn't "beat" at the correct rate no matter how adjustable. It's just too long. Longer pendulums beat more slowly than short ones. Think grandfather clock vs a mantel clock like this.
How did I know that the pendulum from my cuckoo find was likely too long?
The movement told me.
Thus beginneth the history lesson...
Turns out most 19th century French clocks have their movement back plates stamped with numbers that correspond to the pendulum length that matches the clock. Right on the bottom of the plate below the maker's mark.
Regardez.
The "4" and "4" on each side of the plate refer to Pouce and Lignes.
I'll quote, extensively, a richly detailed article written by a fellow member of the NAWCC, Dave LaBounty:
"First is the problem of determining the values of the numbers originally used in calculating the pendulum lengths. The French used "pouce", the French word meaning "inch", and "ligne", meaning "line", as units of measurement for their pendulum lengths with a pouce being divided into 12 lignes. Therefore, if one ligne is added to a pendulum length of 4 pouces,11 lignes the result is 5 pouces, not 4,12. These units have an integral part in the history of France's conversion to the metric system and some of the difficulty in finding the original values is due to this conversion. If the values the French used to determine pendulum length are not used in determining the beat rates, the rates will be inaccurate and defeat the purpose of the table. It is important, therefore, to use the late 1800's pouce and ligne values in determining the beat rate for a late 1800's clock.
Prior to the French Revolution (1789 - 1799), the pouce and ligne were accepted units of measurement with the value of a pouce in millimeters being 27.07 mm and a ligne, 2.256 mm. However, during this time, the scientific community was trying to establish a new decimal or "metric" system to replace the cumbersome one using pouce and ligne. The political unrest at the time gave them an uphill battle, and in 1800 a decree was made to use the new metric system with the old French names to help it gain acceptance. This turned out to be unpopular and for twelve years two "metric" systems were in use: one with pouce and ligne to represent metric units and one with units of meter and centimeter. Then in 1812, Napoleon established the "systeme usuelle" which modified the metric weights and measures to bring them more in line with the pre- Revolution units. This changed the value of a pouce from 27.07 mm to 27.75 mm and a ligne from 2.256 mm to 2.31 mm. Finally, in 1840, the "usuelle" system was repealed in favor of the scientist's first metric system and France declared the decimal metric system to be the only legal one. Anyone who ignored this law was subject to stiff penalties.1 This system is the same one used today in many countries of the world and the scientific community as a whole. France is the center of the metric or International System (SI) of weights and measures and maintains the standards for the world. So, why did French clockmakers stamp the numbers for pouces and lignes instead of centimeters and millimeters on the back plates of their movements after 1840? Perhaps it was a little left- over rebellion, stubbornness, or more likely, tradition."
Stubborn? The French?
Quelle surprise!
And how about Napoleon having his own system for a while. So a pouce was an inch and then it wasn't and then it was.
If you really want to see the math, check out Mr. LeBounty's article. It references both Chemistry and Physics books. Whew!
Anyway Monsieur LeBounty calculates that a pendulum of 4 pouces et 4 lignes beats at a rate of 10,474 beats per hour. Of course that also depends on relative gravity...
Umm... what it really boils down to is that 4 pouces et 4 lignes comes about to a pendulum length of about 4-1/3 inches.
Another interesting factor. The pendulum length is measured from the point the suspension spring exits the suspension bridge to the middle of the pendulum bob. Many 19th century French clocks employed an adjustable suspension made by the Brocot family.
Some more context and history...
Pendulums need to be adjustable in length. Keeping the proper beat on a clock often requires modest adjustments of pendulum length.
Very early French clocks were not suspended by springs but were simply hooked to a length of silk thread. Adjust the length of the thread and you adjust the length of the pendulum. But that design had many compromises too.
Like so.
At the time many clockmakers were working with metal strip suspension springs and Louis Brocot attempted to combine the silk thread adjustability with a suspension spring.
It didn't last. The silk thread had to go.
Brocot designed a fully mechanical solution that became the standard for French clocks thereafter.
From his original 1840's patent drawings:
His son, Antoine, kept up the family business and patented some important modifications in 1866.
And here's that 1866 patented version on the bench today with its suspension spring just popped out a bit from it.
Complete with the family name stamped there on the adjustment wheel.
Rotating that starred adjustment wheel turns a screw that slides the adjustable block in the bridge up and down. The suspension spring doesn't get longer or shorter, the point that it exits the block does.
Nice piece of engineering history in my hands.
OK if you're still awake what this meant on a more practical level was my 6-ish inch (full length) pendulum needed to be more like 5-ish inches.
So I found another one on eBay.
Of course it worked.
I'll get to that.
Scott and I went over to check it out.
30-ish Matt and his wife lived in a small bungalow in PG. He was running late. We were in no rush. Nice people.
He said the clock "ticked but didn't keep good time."
The thing is solid slate. Maybe 30 pounds worth. Glass bezel missing. A little scuffed but overall looked nice. No maker's label but peering in the back I noted a few things.
Firstly, it wasn't keeping time because it had no pendulum. Matt wasn't aware it needed one.
OK.
A quick glance saw the distinctive round shape and classic elements of a French movement and there was a maker's mark.
Jules Rolez Limited Paris. Not Rolex.
We haggled. I knew this beastie needed some work but suspected I could make it run.
He wanted $140. Settled on $60.
Took her home and put her on a shelf for a few months. Didn't do much clock stuff in the cold weather.
Spring has sprung and I'm back at it. The new bench didn't hurt either. So dusted the old girl off and found an appropriate pendulum on eBay.
Appropriate.
Ahem...
Standard french pendulums are a bit more complicated than those found in your typical American antique clocks.
The French version has a double hook that goes over a pin on the suspension spring.
The weight of the pendulum bob tends to be standardized on most mantle styled French clocks. However many clocks, especially French ones, are quite fussy about the length of the pendulum.
When I bought my cuckoo last summer there was a second pendulum in the box of parts. From an entirely different clock. It was a French pendulum.
Let's try it.
Nope. Was way too slow even with adjustments.
Actually I guessed it wouldn't "beat" at the correct rate no matter how adjustable. It's just too long. Longer pendulums beat more slowly than short ones. Think grandfather clock vs a mantel clock like this.
How did I know that the pendulum from my cuckoo find was likely too long?
The movement told me.
Thus beginneth the history lesson...
Turns out most 19th century French clocks have their movement back plates stamped with numbers that correspond to the pendulum length that matches the clock. Right on the bottom of the plate below the maker's mark.
Regardez.
The "4" and "4" on each side of the plate refer to Pouce and Lignes.
I'll quote, extensively, a richly detailed article written by a fellow member of the NAWCC, Dave LaBounty:
"First is the problem of determining the values of the numbers originally used in calculating the pendulum lengths. The French used "pouce", the French word meaning "inch", and "ligne", meaning "line", as units of measurement for their pendulum lengths with a pouce being divided into 12 lignes. Therefore, if one ligne is added to a pendulum length of 4 pouces,11 lignes the result is 5 pouces, not 4,12. These units have an integral part in the history of France's conversion to the metric system and some of the difficulty in finding the original values is due to this conversion. If the values the French used to determine pendulum length are not used in determining the beat rates, the rates will be inaccurate and defeat the purpose of the table. It is important, therefore, to use the late 1800's pouce and ligne values in determining the beat rate for a late 1800's clock.
Prior to the French Revolution (1789 - 1799), the pouce and ligne were accepted units of measurement with the value of a pouce in millimeters being 27.07 mm and a ligne, 2.256 mm. However, during this time, the scientific community was trying to establish a new decimal or "metric" system to replace the cumbersome one using pouce and ligne. The political unrest at the time gave them an uphill battle, and in 1800 a decree was made to use the new metric system with the old French names to help it gain acceptance. This turned out to be unpopular and for twelve years two "metric" systems were in use: one with pouce and ligne to represent metric units and one with units of meter and centimeter. Then in 1812, Napoleon established the "systeme usuelle" which modified the metric weights and measures to bring them more in line with the pre- Revolution units. This changed the value of a pouce from 27.07 mm to 27.75 mm and a ligne from 2.256 mm to 2.31 mm. Finally, in 1840, the "usuelle" system was repealed in favor of the scientist's first metric system and France declared the decimal metric system to be the only legal one. Anyone who ignored this law was subject to stiff penalties.1 This system is the same one used today in many countries of the world and the scientific community as a whole. France is the center of the metric or International System (SI) of weights and measures and maintains the standards for the world. So, why did French clockmakers stamp the numbers for pouces and lignes instead of centimeters and millimeters on the back plates of their movements after 1840? Perhaps it was a little left- over rebellion, stubbornness, or more likely, tradition."
Stubborn? The French?
Quelle surprise!
And how about Napoleon having his own system for a while. So a pouce was an inch and then it wasn't and then it was.
If you really want to see the math, check out Mr. LeBounty's article. It references both Chemistry and Physics books. Whew!
Anyway Monsieur LeBounty calculates that a pendulum of 4 pouces et 4 lignes beats at a rate of 10,474 beats per hour. Of course that also depends on relative gravity...
Umm... what it really boils down to is that 4 pouces et 4 lignes comes about to a pendulum length of about 4-1/3 inches.
Another interesting factor. The pendulum length is measured from the point the suspension spring exits the suspension bridge to the middle of the pendulum bob. Many 19th century French clocks employed an adjustable suspension made by the Brocot family.
Some more context and history...
Pendulums need to be adjustable in length. Keeping the proper beat on a clock often requires modest adjustments of pendulum length.
Very early French clocks were not suspended by springs but were simply hooked to a length of silk thread. Adjust the length of the thread and you adjust the length of the pendulum. But that design had many compromises too.
Like so.
At the time many clockmakers were working with metal strip suspension springs and Louis Brocot attempted to combine the silk thread adjustability with a suspension spring.
It didn't last. The silk thread had to go.
Brocot designed a fully mechanical solution that became the standard for French clocks thereafter.
From his original 1840's patent drawings:
His son, Antoine, kept up the family business and patented some important modifications in 1866.
And here's that 1866 patented version on the bench today with its suspension spring just popped out a bit from it.
Complete with the family name stamped there on the adjustment wheel.
Rotating that starred adjustment wheel turns a screw that slides the adjustable block in the bridge up and down. The suspension spring doesn't get longer or shorter, the point that it exits the block does.
Nice piece of engineering history in my hands.
OK if you're still awake what this meant on a more practical level was my 6-ish inch (full length) pendulum needed to be more like 5-ish inches.
So I found another one on eBay.
Of course it worked.
I'll get to that.
Pouce Went The Ligne of my Heart - your terrier-like determination is astonishing.
ReplyDeleteI love how much history is wrapped into the hobby of clock restoration. Nicely done!
ReplyDelete