VR-379 Rare Compound Seconds-beat Pendulum
While we all know that clocks with meter-long pendulums tick once per second, perhaps you are not aware that clocks with shorter pendulums can also tick once per second. This is achieved by having two pendulum bobs, one on the lower end of the pendulum rod (the conventional location) and one on the top. While extremely rare (there is one in the Clock Museum in Vienna), there were a few made – of which this clock is an excellent example.
I think the pictures do a good job of showing how the pendulum is set up – here are a couple of general comments:
- The pendulum pivots on a knife-edge suspension point – located in the middle of the brass section just below the top of the faux-grid-iron pendulum.
- Both the upper bob (black cast iron disc) and the lower bob positions are adjustable to control the rate of the pendulum
- The crutch pin set-up is rather fancy – with the pin riding on a lever such that the crutch pin can move up and down, allowing it to rest in the triangular slot in the pendulum rod. This minimizes the play between the pin and the pendulum rod, as well as allowing for any difference in the alignment of the pin and the slot. This is necessary since the pivot point for the pendulum is below the mechanism, as opposed to the usual point which is usually in line with the anchor pivot point.
- The pendulum is 22 inches long
- The formula for a compound pendulum is: T=Pi * ((M1*L12 + M2 * L22)/(G * (M1 * L1 - M2 * L2)))½
While the pendulum is extremely unusual, the mechanism is also a bit of a wonder. I have not yet had a chance to go through the mechanism, but, just looking at it I can see the following:
- Maintaining power
-Center-sweep second
-Very unusual anchor – set up so that the anchor can be rotated relative to the arbor – with a very elaborate and well done clutch mechanism
-Very small mechanism – back plate measures only 3.25 inches tall.
-Exquisitely made crutch with the pin on a lever – beautifully made.
-Dual idler gears on the front of the clock to drive the minute cannon from the second arbor, and then too drive the hour cannon from the minute cannon.
Overall, the clock case is in reasonable condition, but will benefit a great deal from my going through it. The top finial is clearly a replacement, and will be replaced with one more appropriate. The case measures 51 inches long with the current top finial.
Fortunately the dial is in exceptional condition, with a couple of fine hairlines that will disappear when the dial is cleaned.
This is a clock I am really looking forward to going through.
Read MoreI think the pictures do a good job of showing how the pendulum is set up – here are a couple of general comments:
- The pendulum pivots on a knife-edge suspension point – located in the middle of the brass section just below the top of the faux-grid-iron pendulum.
- Both the upper bob (black cast iron disc) and the lower bob positions are adjustable to control the rate of the pendulum
- The crutch pin set-up is rather fancy – with the pin riding on a lever such that the crutch pin can move up and down, allowing it to rest in the triangular slot in the pendulum rod. This minimizes the play between the pin and the pendulum rod, as well as allowing for any difference in the alignment of the pin and the slot. This is necessary since the pivot point for the pendulum is below the mechanism, as opposed to the usual point which is usually in line with the anchor pivot point.
- The pendulum is 22 inches long
- The formula for a compound pendulum is: T=Pi * ((M1*L12 + M2 * L22)/(G * (M1 * L1 - M2 * L2)))½
While the pendulum is extremely unusual, the mechanism is also a bit of a wonder. I have not yet had a chance to go through the mechanism, but, just looking at it I can see the following:
- Maintaining power
-Center-sweep second
-Very unusual anchor – set up so that the anchor can be rotated relative to the arbor – with a very elaborate and well done clutch mechanism
-Very small mechanism – back plate measures only 3.25 inches tall.
-Exquisitely made crutch with the pin on a lever – beautifully made.
-Dual idler gears on the front of the clock to drive the minute cannon from the second arbor, and then too drive the hour cannon from the minute cannon.
Overall, the clock case is in reasonable condition, but will benefit a great deal from my going through it. The top finial is clearly a replacement, and will be replaced with one more appropriate. The case measures 51 inches long with the current top finial.
Fortunately the dial is in exceptional condition, with a couple of fine hairlines that will disappear when the dial is cleaned.
This is a clock I am really looking forward to going through.
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