Tid-Bit 6 - More Donuts
Published in the 8/2010 NAWCC Bulletin, page 477
The purpose in making the drums larger is to increase the torque supplied to the mechanism by the weight. Torque is what drives a mechanism. So, rather than hanging a larger weight on a mechanism that won’t run (a practice that will only increase wear, especially in a poorly serviced mechanism), some folk just make the winding drum larger, providing more torque to the mechanism, and hopefully making the clock run. Torque is calculated by multiplying the force (think weight pulling on the weight chord) times the moment arm (the radius of the winding drum). So, increase the radius of the winding drum and you increase the torque. Problem is, if you increase the size of the winding drum, each turn of the drum releases more weight chord. In fact, the increased weight drop is directly proportional to the increase in the size of the drum. And, if more weight chord is released in each turn, the weight falls farther for each turn of the drum, and the drum ends up turning fewer times for a given available weight drop. So, a larger drum may get the clock running, but it will shorten its duration.
If you look back in the August 2005 NAWCC Bulletin starting on page 469 http://www.snclocks.com/TechnicalInformation/Articles/Clock-repair-vienna/10764949_4gGKr#750284439_BwENm you will find an article on a donut I found in a month-duration Vienna Regulator. Since then I have come across several more donuts, and one of my correspondents down in Dallas sent in interesting pictures of one he found – carved out of a thread spool – as shown in Figures 1 and 2 below:
Read MoreThe purpose in making the drums larger is to increase the torque supplied to the mechanism by the weight. Torque is what drives a mechanism. So, rather than hanging a larger weight on a mechanism that won’t run (a practice that will only increase wear, especially in a poorly serviced mechanism), some folk just make the winding drum larger, providing more torque to the mechanism, and hopefully making the clock run. Torque is calculated by multiplying the force (think weight pulling on the weight chord) times the moment arm (the radius of the winding drum). So, increase the radius of the winding drum and you increase the torque. Problem is, if you increase the size of the winding drum, each turn of the drum releases more weight chord. In fact, the increased weight drop is directly proportional to the increase in the size of the drum. And, if more weight chord is released in each turn, the weight falls farther for each turn of the drum, and the drum ends up turning fewer times for a given available weight drop. So, a larger drum may get the clock running, but it will shorten its duration.
If you look back in the August 2005 NAWCC Bulletin starting on page 469 http://www.snclocks.com/TechnicalInformation/Articles/Clock-repair-vienna/10764949_4gGKr#750284439_BwENm you will find an article on a donut I found in a month-duration Vienna Regulator. Since then I have come across several more donuts, and one of my correspondents down in Dallas sent in interesting pictures of one he found – carved out of a thread spool – as shown in Figures 1 and 2 below:
Figure 1 - A wooden donut that Scottie found in a German Vienna-Style Regulator
While Scottie’s is perhaps the most “inventive”, I have also come across winding drums that have been wrapped in tape, old news print, and thread. All apparently in an attempt to increase the diameter of the drum, thereby getting a balky mechanism to run.
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