French Portico Clock Questions

[Schatz70]

This is cool looking clock that I would like to restore but I'm missing the pendulum and the hammer. Questions regarding the pendulum:
1. The back plate has the numbers 64 and 560 on it. Does that tell the length of the pendulum?
2. The crutch has an unusual shape - there is a narrow slot cut in it that widens out to a crescent shape (see last photo). How is the pendulum supposed to tie in to the crutch? There is a suspension spring up at the top with two pins sticking out the sides to hang the pendulum on.

Questions regarding the hammer:
3. It looks to me like the hammer attaches with a taper pin to the arbor sticking out the back plate above the "560" shown in the third photo. Does that sound right?
4. I'm thinking my best option is to fabricate a hammer using a couple pieces of brass rod, a piece of wire, and a piece of leather. What would you do?

Question about the maker:
5. The back plate has a shield logo with the letters B and D and "Made in France". Any idea who the manufacturer is?

Thanks for any help.

 

[wow]

You will need a pendulum and hammer similar to this.
The pendulum hooks on the suspension spring and extends through the fork. The hook is sold separately.

 

[Schatz70]

You will need a pendulum and hammer similar to this.
The pendulum hooks on the suspension spring and extends through the fork. The hook is sold separately.

Thank you! The slot in the crutch is 2 mm wide and the hook you listed has an unthreaded 2 mm hole for soldering so I guess that is right. The arbor for the bell hammer is square. It looks to me like the bell hammer is just held on by friction which is how they get lost. I'm going to try the Time Savers part you suggested. You have been very helpful.

 

[wow]

Thank you! The slot in the crutch is 2 mm wide and the hook you listed has an unthreaded 2 mm hole for soldering so I guess that is right. The arbor for the bell hammer is square. It looks to me like the bell hammer is just held on by friction which is how they get lost. I'm going to try the Time Savers part you suggested. You have been very helpful.

The length of the pendulum will have to be figured out. That one can be cut off if it runs too slow. The arbor that holds the hammer usually has a tiny hole in it and a tapered pin holds it on.

 

[Schatz70]

The length of the pendulum will have to be figured out. That one can be cut off if it runs too slow. The arbor that holds the hammer usually has a tiny hole in it and a tapered pin holds it on.

My guess is that there is supposed to be not much clearance between the bottom of the pendulum and the marble base of the clock - no more than an inch, maybe no more than half an inch. Better to err on the long side because as you say I can always shorten it if it runs too slow. You are right about the hammer arbor - there is a tiny little hole for a taper pin.

 

[wow]

Some portico clocks had larger, more ornate pendulums. Yours may have also but I have not seen them from suppliers. You may be able to find one on eBay but rarely. In the mean time this will work

 

[Schatz70]

Some portico clocks had larger, more ornate pendulums. Yours may have also but I have not seen them from suppliers. You may be able to find one on eBay but rarely. In the mean time this will work

I ordered the French Brass Sunburst Pendulum 2-1/8" x 11-1/2" from Timesavers. I'm hoping it's going to be a 2 mm pendulum rod but they don't tell you that.

French Brass Sunburst Pendulum 2-1/8" x 11-1/2"

Round cast brass plated sunburst french pendulum with a 12" partially threaded rod. 2-1/8" diameter x 3 ounce bob. Top hook sold separately.

timesavers.com

 

[Schatz70]

There is a little brass gear that doesn't turn anything on top of the suspension spring that says L BROCOT BUSGDG which might be a clue as to who the manufacturer is.

 

[daveR]

The 6 4 at the bottom of the clock os your key to the pendulum length. It gived you tje length from the suspension to the theoretical centre of the bob in old French inches (pouces and lignes). There are conversions available on the internet. The little brass wheel at the top should mesh with another in the pendulum support mechanism to give fine timing adjustment from the dial.
David

 

[bruce linde]

There is a little brass gear that doesn't turn anything on top of the suspension spring that says L BROCOT BUSGDG which might be a clue as to who the manufacturer is.

that's a style of beat regulator that (effectively) lengthens or shortens the pendulum to allow you to regulate the movement. it it adjusted using the smaller end of a double-ended key, with the arbor for it up around the 12 on the dial. many many french movements have brocot adjusters... and other than 'french movement' specific manufacturer names are hard to come by....

 

[wow]

I ordered the French Brass Sunburst Pendulum 2-1/8" x 11-1/2" from Timesavers. I'm hoping it's going to be a 2 mm pendulum rod but they don't tell you that.

French Brass Sunburst Pendulum 2-1/8" x 11-1/2"

Round cast brass plated sunburst french pendulum with a 12" partially threaded rod. 2-1/8" diameter x 3 ounce bob. Top hook sold separately.

timesavers.com

I didn’t think about that pendulum. That is better than the one I suggested. You can probably adapt the rod to the hook.
I have worked on a lot of French clocks but have not seen that logo. Someone will come along with that info. Let us see it when you get it all done. Nice clock!

 

[Schatz70]

The 6 4 at the bottom of the clock os your key to the pendulum length. It gived you tje length from the suspension to the theoretical centre of the bob in old French inches (pouces and lignes). There are conversions available on the internet. The little brass wheel at the top should mesh with another in the pendulum support mechanism to give fine timing adjustment from the dial.
David

Thank you! I found a conversion that says 1 ligne = 0.088812168 inches, so 64 ligne would be 5.68". That's probably in the ballpark. I don't see another gear that meshes with the one on top of the suspension, but the pendulum is going to be totally visible and accessible (there is an opening in the bottom of the case that the pendulum hangs through) and will have a rating nut on the bottom of it.

 

[new2clocks]

The back plate has a shield logo with the letters B and D and "Made in France". Any idea who the manufacturer is?

The logo on the backplate is a trademark of Bawo & Dotter, a New York importer of clocks. However, this does not solve the mystery of the maker of the movement.

There is a little brass gear that doesn't turn anything on top of the suspension spring that says L BROCOT

Brocot refers to Brocot escapements and Brocot suspension adjustment that Brocot patented. Many French manufacturers used Brocot technology, so again no help on the maker of the movement.

Regards.

 

[daveR]

From what I have seen it is a little un usuual to have brocot adjusters on portico clocks, but that doesn’t meanthey weren't used! There needs to be a tiny hole above the 12 or even in the bezel so the rate could be adjusted from the front. Looking at your pictures also seems to show no provision for the front to back arbor to be mounted. You could turn it by hand , the change is very slight, if you want really good timekeeping. Maybe the suspension cock was substituted in for another one in the last 100 or so years!!
David

 

[agemo]

Hi,
Pendulum length calculation :
(27,069 X6 )+(2,25575x4) = 171,437 millimeters

Round up to 171.5 millimeters
Amicalement GG

 

[agemo]

This is a mistake, sorry !

 

[Schatz70]

Be careful as said above to orientate the pallets well, the left one upwards and the right one downwards.

View attachment 676873

My clock does not have a Brocot escapement. It has a verge with pallets that interact with the escape wheel.

 

[Schatz70]

Hi,
Pendulum length calculation :
(27,069 X6 )+(2,25575x4) = 171,437 millimeters

Round up to 171.5 millimeters
Amicalement GG

Thank you; that is helpful. 17.15 cm = 6.75 inches which looks about right with the addition of more length for the distance between the center of the pendulum bob and the bottom of it.

 

[Schatz70]

To expand on daveR's comments and agemo's calculation of the pendulum length, the 64 on the back plate means 6 pouces and 4 lignes.

1 pouce = 27.07 mm
1 ligne - 2.256 mm

I found an online calculator here: M & P French Clock Pendulum Length calculator

When I put 6 pouces and 4 lignes into the calculator it gives 171 mm as the pendulum length which agrees with what agemo said.

 

[R. Croswell]

......... Questions regarding the pendulum:
1. The back plate has the numbers 64 and 560 on it. Does that tell the length of the pendulum?

This article explains all you will ever need to know about how these numbers relate to pendulum length and a lot more. As the article details it can depend on when the clock was made and which standard was used.

https://abouttime-clockmaking.com/pdfs/french_clock_beat_rates_labounty.pdf

RC

 

[new2clocks]

The logo on the backplate is a trademark of Bawo & Dotter, a New York importer of clocks.

I should have cited mikrolisk as the source of this information.

Regards.

 

[Schatz70]

The pendulum and hook arrived today. The description on Timesavers said that one end of the rod is threaded and I incorrectly assumed that the threaded end is for a rating nut, but it isn't. The threaded end is meant to go into a threaded hook at the top, and someone I spoke to at Timesavers verified that the threads on the rod fit the #12260 French pendulum hook which has #3-48 threads, which, curiously, is an English size, not a metric size. I used an English screw chekr to verify that the threads are #3-48. So the way to regulate the clock is via a set screw on the back of the pendulum bob (see second photo) which I wasn't altogether happy about because I think a rating nut gives you finer control over the rating adjustment, but on the other hand it looks better with just the pendulum bob and no rating nut on the bottom of it. I bought an unthreaded hook but that just means I will have to solder it on rather than screwing it on, but no big deal. The pendulum rod does fit in the notch in the crutch, and the hook fits on the suspension spring, so I think it's gonna work, assuming I am successful in overhauling the (very dirty and badly gummed up) movement.

 

[Uhralt]

Your clock has a Brocot adjustment. That means you can fine adjust the clock by turning the small square on top of the dial. First make sure that the adjustment is in the middle of its range. Then secure the bob at a height that makes the clock run almost correctly. The rest can be adjusted using the square. Turing it clockwise makes the clock run faster, counter-clockwise slower.

Uhralt

 

[daveR]

Yes, Uhralt is right on, use the the screw on the pendulum for a fairly rough set up and the brocot adjuster is a much finer sdjustment, but the range is not very wide. And I agree with you an adjuster hanging off the bottom of the sunburst would look wrong! The Brocot unit on yours is an extra, my two , and possibly third, but dismantled, only have the adjustment available from the pendulum.
David