L. von der Burg or Kern?

[Ken M]

This looks like plate 1411 with no signature. The suspension unit is a Kern standard. Anyone know what this is?

 

[KurtinSA]

Maybe plate 1667? What does the rest of the clock look like?

Kurt

 

[Ken M]

I just paid 4 times what it's worth and can't afford it, but I couldn't help myself. I think you're right, 1667.

 

[Schatznut]

I just paid 4 times what it's worth and can't afford it, but I couldn't help myself. I think you're right, 1667.

View attachment 655176

Good looking clock - the Roman numerals are especially nice. Now if you'd payed 10x what it was worth...

 

[etmb61]

The clock is a Kern but the pendulum is a Schatz. You should have one like this:


Eric

 

[Ken M]

I hope the weight is close. Anyone have one that can tell me the weight?

 

[KurtinSA]

I have two Kerns with the 1667 back plate. The pendulums run about 10.5 oz each while just about all Schatz 49 pendulums run about 12.5 oz. So, you will need to account for that going forward.

Kurt

 

[Ken M]

How do I account for that?

 

[Ken M]

I have a couple pendulums hanging around, one Kundo, and I think a Schatz, they weigh 8.something. The Huber that I have down right now, weighs 9.59. I'm pretty sure my scale is good, but I could be wrong.

 

[KurtinSA]

How do I account for that?

This is where you'll need to take a spring out of a package that you think might work. Clamp the bottom block on and put the top block on at the right spot...but don't cut the excess off just yet. Find a way to clamp the top block on something so you can hang the suspension spring and the pendulum with the adjuster in the middle of the range. Start it oscillating and time how long to get 8 beats. If it's longer than 60 seconds, you'll need a thicker spring. If less than 60 seconds, you'll need a thinner spring. The rule of thumb is 0.0001" equals 4 seconds per minute of rate.

Kurt

 

[Ken M]

Thanks. This will be a new experience! So if the Schatz is 2oz lighter than the Kern, I'll need a thinner spring than the 0.0036" the Kern calls for? A lot thinner?

 

[KurtinSA]

My Schatz clocks are 2 ozs heavier than my Kern. I'm not aware of the precise relationship between spring thickness versus pendulum weight, but it stands to reason that heavier would require a thicker spring. But the guide calls out 0.0036" for plate 1667 and most Schatz clocks are 0.0040". The Kern spring is slightly longer than the standard Schatz, so that will factor in as well. My guess you should start with a 0.0040" and go from there.

Kurt

 

[Ken M]

That's sounds like a plan. I'll weigh it first. I'm thinking the pendulums I have laying around are for miniatures, just guessing.

 

[Ken M]

I just took my Schatz standard down for some cleaning, pendulum weighs 12.65. Those other two are for mini's.

 

[Ken M]

Got the Kern, everything is there. Got the works taking a bath. The base plate looks painted gold. Are they supposed to be like that? What will I find underneath, brass or steel?

 

[Schatznut]

I just took my Schatz standard down for some cleaning, pendulum weighs 12.65. Those other two are for mini's.

The pendulums for the Schatz 49s are heavy suckers but keep in mind, as Galileo showed, that the period is not related to the mass of the pendulum, but to its length. The ideal mass of the pendulum would be that which would guarantee the escapement would continue to trip for the maximum duration of the winding (in this case ~400 days) and no more.

As to brass or steel, a magnet is your best friend.

 

[Wayne A]

The pendulums for the Schatz 49s are heavy suckers but keep in mind, as Galileo showed, that the period is not related to the mass of the pendulum, but to its length

Think Galileo was referring to swinging pendulums. Torsion pendulums are affected by mass and spring rate.

Wayne

 

[Schatznut]

Think Galileo was referring to swinging pendulums. Torsion pendulums are affected by mass and spring rate.

Wayne

Interesting. Can you point me at a reference that shows the dependence of the period on the mass?

 

[Wayne A]

Interesting. Can you point me at a reference that shows the dependence of the period on the mass?

Well maybe later I'll look. For now what do you think will happen to a torsion pendulums period if you remove a couple weights reducing its rotating mass?

 

[KurtinSA]

Easy enough to test...take an existing suspension unit and clamp the top block to a test stand. Hang two different pendulums, say a regular one and a miniature one and determine the period or how many beats in say 60 seconds.

Kurt

 

[Ken M]

That's what I'm trying. I replaced a couple balls on the Schatz with lighter balls from another pendulum, I've got the overall weight to 10.74, or something like that. I'll name it Frankenstein if I get it running.

 

[Schatznut]

Well maybe later I'll look. For now what do you think will happen to a torsion pendulums period if you remove a couple weights reducing its rotating mass?

I'd expect no change. The amplitude of the rotation would change but not the period.

 

[KurtinSA]

I took a suspension unit off a Schatz clock. I hung the top block and put on the Schatz pendulum. It weighs 12.6 oz and I got 8 beats in 60.52 seconds. I found a miniature pendulum, probably a Herr, and it weighs 6.7 oz and I measured 8 beats in 31.07 seconds.

Kurt

 

[Schatznut]

I took a suspension unit off a Schatz clock. I hung the top block and put on the Schatz pendulum. It weighs 12.6 oz and I got 8 beats in 60.52 seconds. I found a miniature pendulum, probably a Herr, and it weighs 6.7 oz and I measured 8 beats in 31.07 seconds.

Kurt

I wonder what the relative center of mass of the two pendulums is. For example, the regulator nut changes the period of a pendulum by moving its center of mass, not its mass. I wonder what the effect of removing two opposite weights from a four-weight pendulum would be. The center of mass would remain the same but the weight would be decreased by a significant amount.

 

[Wayne A]

I wonder what the effect of removing two opposite weights from a four-weight pendulum would be.

Thats the question I asked you earlier. Its going to reduce the pendulum's period.

 

[Schatznut]

I've identified the error in my thinking. I was thinking of the pendulum as a classic gravitational system wherein the connection between the center of mass of the pendulum and the pivot is a rigid body. That's not the case in a torsion clock, in that the connection is a spring.

For the rigid-body case, T=2(pi)*sqrt(L/g) where T is the period, L is the length of the pendulum and g is the force of gravity.

For the spring case, T=2(pi)*sqrt(m/k) where T is the period, m is the mass of the pendulum and k is the spring constant. (Red highlight added because this is the point Wayne is making.)

The basic period of a torsion pendulum is set by the mass and spring constant, but fine regulation is set by changing the center of mass of the pendulum relative to the centerline of the torsion spring. This is the effect of conservation of angular momentum (the same phenomenon that causes a skater's speed of rotation to increase as she draws her arms in close to her body). It has nothing to do with the rigid-body period of oscillation.

When we're choosing a new torsion spring, we're playing around with the spring constant k - the only variable in the equation we can adjust unless we change the weight of the pendulum. The calculation of k for a given torsion spring is complicated in that there are a large number of factors that affect it, not the least of which is its overall length.

I have a standard Kundo I bought without a pendulum that's running a Schatz pendulum because that's all I had. I had to choose a different suspension spring relative to what "The Book" says but it runs great and keeps time well. I played with the m/k relationship to get the T necessary.

 

[KurtinSA]

Took the same setup and removed two opposite weights and shells on the Schatz pendulum. Weighs 7.9 oz and I measured 8 beats in 43.68 seconds.

Kurt

 

[Ken M]

Interesting.. You do the math, I'll just wing it! I've got some work to do on it before I get serious about getting it to run.

 

[Ken M]

Will wonders never cease? Full weight pendulum, I might try reducing it again....maybe. It only lost 10 minutes in an hour...maybe I can dial in in! j/k. It's running, I have other clocks to tell the time. I really like the dial, maybe some day I'll try it different spring to get it closer on the time.

 

[Ken M]

I swapped a couple weights, still runs slow.

 

[Schatznut]

The Schatz clocks run with a 0.004" spring. Increasing the thickness of the spring will cause it to run faster. I don't recall you saying what strength spring you installed originally, but you might try going up 0.0002" from where you are now and measuring the difference.

 

[Ken M]

I used the .0036. I have a ,004, not sure if I have anything in between. Maybe I'll try the .0040, but I think a .0038 would be better, it's real close now with the pendulum cranked all the way up. I'm afraid the .0040 might send me in the other direction.

 

[Schatznut]

The 0.004" will likely be the upper bound. Give it a try and see how close you come...

 

[Ken M]

It's keeping perfect time as it is. I set it an hour slow by mistake, got up the next day and it was an hour slow. I thought it had lost 100 hours over night.......anyway, it's keeping good time with .0036" and two Schatz weights swapped out for lighter weights. Frankenstein.

 

[KurtinSA]

The next repair person to see this clock is going to want to have a word with you!!

Kurt

 

[Ken M]

Yea, but I'll be dead, so I don't care.

 

[Wayne A]

Schatz weights swapped out for lighter weights. Frankenstein.

Ran across a couple clocks like this.. One clock even had lead shot for weights which is terible because the loose shot could move around making time regulation nearly impossible. Ended up makeing new weights.

 

[Ken M]

I'm thinking about replacing the weights in the pendulum and trying a .0040" spring. In the book it says to use unit 11A, there is also an 11B apparently for a locking pendulum, it is a bit longer. If I went with the bit longer 11B. what effect will that have? If this doesn't work, maybe I can still use the spring on another clock....if it's longer. Thoughts?

 

[etmb61]

Ken,

If you are going to use the JUF/Schatz pendulum then use it unmodified with the .0040" spring. The free lenght of the spring will effect the pendulum's rotation slightly but not as much as changing the spring's thickness. The JUF/Schatz pendulum should have more than enough adjustment range to compensate for the extra length.

If you end up marrying movements with pendulums from different makers, you need to use the spring size associated with the pendulum, not the movement.

Eric

 

[Ken M]

Thanks Eric. It's running goos with the cheat I did, but I might find a clock that needs the pendulum I robbed two weights from.

 

[Ken M]

It's running with the .0040" and full Schatz weight. Looks slow, and I just maxed it out on the fast setting. Basically the same it was with lighter weight and thinner spring.

 

[etmb61]

Horolovar spring?

 

[Ken M]

Yes. Maybe I need to go to the shorter 11A.

 

[etmb61]

If you have the space between the top of the pendulum and the bottom of the movement you may need to go as short as 6789.

Just for giggles I checked my new stock of .0040" marked Horolovar springs with a micrometer and found .0039". My last old stock spring is actually checked at .0040". The springs in the two new packages even looked different from each other. That could be a problem too. Lots of supply changes probably happened between the time the original spring sizing was figured out and the books written until today. We may have reached the point were we will need to test each spring we use.

Eric

 

[Ken M]

I got this spring over 10 years ago, so who knows? I don't have a micrometer to check it. It lost about 7 minutes overnight. To me that's outside the margin of error, but we'll see over the next day of two. Nothing I can do with it, it's maxed out. Still a nice clock. Some day I may see the pendulum for sale on eBay!

 

[Ken M]

Finally. I found that there were a couple more threads at the fast end, so I cranked it up and it ran fast, a little. I've been tweaking it down, and it's keeping pretty good time now. So, Monday I'll be getting a beat up Kundo, looking forward to it.

 

[Ken M]

Maybe plate 1667? What does the rest of the clock look like?

Kurt

SO I now have two of these clocks. My old book did not have plate 1667. But that's what they are. According to Appendix 81 in the book, the 1954 version of this plate have an escapement guard and a pendulum locking bracket. Neither of these two have those additions. When I got these clocks, they just struck me as old. So am I to assume these clocks were made "sometime" between 1932 and 1954? Is there anyway I can narrow that down? Now I just need to fine a Kern pendulum for Kern #1 and get that Schatz pendulum off it. It's a good timekeeper, but that Schatz pendulum needs to be on a Schatz!

 

[KurtinSA]

John Hubby had presented information about Kern & Link as being in business from 1929 - 1937...they grew out of the old Kienzle company. In 1937, they became Kern & Söhne which was basically the company until the end of production...1960s or 1970s?

Given that your clock doesn't have a guide cup, it's definitely a pre WWII or up to WWII clock. Kundo was the first to introduce the guide cup in 1933, but the other clocks didn't follow suit until later, some not doing it until after the war.

Not sure what Appendix 81 shows other than a general layout of the clock...certainly doesn't say anything about 1954. But since your clock seems to be Kern & Link and no guide cup, I'd say it's probably mid to late 1930s before they changed names.

Kurt

 

[Ken M]

Plate 1667A, I'me just guessing that's the later model, is c 1954. That's where that came from. They do smell like 1930's, thanks.

 

[KurtinSA]

Note that the guide says Kern & Söhne for 1667A.

Kurt