Grandfather size torsion movement

[pastdarrow]

Fellow members, is there a torsion movement large enough to use in a grandfather sized clock? Does the length of a torsion spring influence a clock like a pedulum does? Is it possible to use a smaller movement with a longer spring? Enlighten me, please.

 

[KurtinSA]

Not sure about GF size clocks, but there was a discussion about a torsion all clock a while back...if you didn't see that. Might provide some additional thoughts/discussions.

https://mb.nawcc.org/showthread.php?126875-Gustav-Becker-Torsion-Pendulum-Wall-Clock

Kurt

 

[Tinker Dwight]

The length effect that rate but only by the hooks constant
of the spring. Gravity has a tiny effect because as the spring
winds up, it lifts the bob by a thousandth or so.
The hooks constant of the spring and the rotational inertia
of the bob are the main factors.
A longer, stiffer spring is needed to have the same restoring
force.
There may be issues with increased air resistance loss because
the bob will have to rotate many more degrees to get the same
offset to run the escapement. This means a faster spinning bob.
Tinker Dwight

 

[John Hubby]

Fellow members, is there a torsion movement large enough to use in a grandfather sized clock? Does the length of a torsion spring influence a clock like a pedulum does? Is it possible to use a smaller movement with a longer spring? Enlighten me, please.

Interesting question. I've only seen a couple of grandfather size torsion pendulum clocks in more than 30 years chasing all kinds of these interesting timepieces. One in particular comes to mind that was made in 1864 and is still running today at the University of Otago in Dunedin, New Zealand. It is called the Beverly Clock. This is a one-off timepiece that operates entirely without manual winding, using daily temperature variation and to some extent atmospheric pressure variation to rewind its weight driven movement. It deserves much more recognition than it has received, being that since being started 151 years ago it has stopped only a relatively few times. The stoppages have been for cleaning, maintenance, one part failure, once for moving location, and on rare occasions because daily temperature fluctuation has not been sufficient to keep it wound.

If you are interested to build a grandfather size torsion clock, there are quite a few torsion pendulum wall clock movements that are large enough to be mounted in a grandfather size case, although these are generally rather expensive. I'm thinking of movements by F. DeGruyter (Plate 1473), R. Schnekenburger (Plate 1504), Carl Bauer (Plate 1303), Hanau Uhrenfabrik (Not in RG), Gustav Becker (Plate 1193), Jahresuhren-Fabrik (Plate1722). Some of these are full striking as well as having the usual time train. You can also use a standard 400-Day clock movement such as a Schatz, Kundo, GB, Kienzle, etc.

Your question about a longer suspension spring is important, all the clocks I've just listed use a "normal" suspension spring between 5 and 7 inches long. Making the springs longer will slow them down, inversely proportional to the percentage increase in length. For example a spring that is twice as long will reduce the rate by 50%, making a clock run 30 minutes per hour slower than it does with the shorter spring. So yes, the spring length is absolutely important. If you will search the forum for wall clocks, you will find that for the most part they use a longer pendulum but not a longer suspension spring. The perfect example is the Gustav Becker in the thread that Kurt provided, you can see that the pendulum is quite long but in fact it uses a normal suspension spring.

It may seem counter-intuitive, but you can make a pendulum as long as you want for any torsion clock movement and it will still run at the same rate as the shorter one, provided the extension rod or wire is relatively small in diameter so it doesn't contribute to the rotational mass of the pendulum. One caution: If you add any decoration, discs, or the like along the length of the extension rod to make it more attractive, you will have to increase the strength of the suspension spring to compensate for the additional rotational mass. Thus, in designing a grandfather size clock and you want to visibly see the pendulum, make it as long as you deem attractive and then compensate for any mass added away from the centerline by increasing suspension spring strength.

One more tip: If you want a typical grandfather size dial, say 10 inches diameter, you will need to use very lightweight material for the hands such as aluminum or a low density plastic, etc., and both hands "must" be counterbalanced for the clock to operate properly. They should also be rather narrow, such as the ones on the Beverly clock, to reduce mass.

Keep us informed if you do start such a project, I've wanted to do one for years but it always winds up being way down on the project list.

 

[John Hubby]

The length effect that rate but only by the hooks constant
of the spring. Gravity has a tiny effect because as the spring
winds up, it lifts the bob by a thousandth or so.
The hooks constant of the spring and the rotational inertia
of the bob are the main factors.
A longer, stiffer spring is needed to have the same restoring
force.
There may be issues with increased air resistance loss because
the bob will have to rotate many more degrees to get the same
offset to run the escapement. This means a faster spinning bob.
Tinker Dwight

Tinker, if you simply add length to the pendulum and keep the same size suspension spring, the pendulum doesn't turn any more than usual. How do I know that? I put a 60 inch extension wire on a normal 400-Day 4-ball pendulum and there was no change in rotation although it ran slightly slower due to the added mass.

 

[shutterbug]

I recently saw a grandfather sized torsion clock. It was in the Amana Colonies Clock Factory. It had electric lighting, so I was not able to ascertain whether the movement was mechanical or not .... but it was sure neat to look at. BTW, this was a modern production ... so someone is making them. They mostly use Hermle at the factory.

 

[etmb61]

In a tall case you could loose the mainspring too.

 

[Tinker Dwight]

Tinker, if you simply add length to the pendulum and keep the same size suspension spring, the pendulum doesn't turn any more than usual. How do I know that? I put a 60 inch extension wire on a normal 400-Day 4-ball pendulum and there was no change in rotation although it ran slightly slower due to the added mass.

Yes John, adding fixed rod or stiff wire length is simple. I tend to answer the what
I think the question is. "What happens if I use a longer suspension spring?"
I should have answered how to make it long to the bob, as you have.
Clearly the best way to solve the problem.
DieteR has shown such a modification on a post a few months ago.
See:
https://mb.nawcc.org/showthread.php?125180-A-self-made-anniversary-wall-clock&highlight=dieter
Tinker Dwight

 

[fixoclock]

I studied this situation many years ago and produced a full size "Austrian" dachluhr cased torsion clock using a Schatz 49 movement, converted to weight drive. Theoretically, the pendulum can be any length you like but the suspension spring remains the same as it would be in the standard glass dome clock.
The pendulum in this clock is 500 mm long and the suspension spring is up in side a brass tube which covers the lower block and all of the spring leading up to the movement.
The clock runs for 8 days and keeps very good time.

 

[pastdarrow]

Thank you, everyone who has replied to my post thus far. As always you people provide great information and insight. The project I have in mind is to make a tall clock out of a hollow tree trunk that has a natural opening at the base. The trunk itself lack the diameter to permit a swinging pendulum, thus the thought of a torsion movement. The opening at the base would allow a natural hole to observe the rotation of the pendulum. You have all been very helpful and I look forward to more information as it comes. You have given much grist for the mill.

 

[shutterbug]

A movement for the 'ol family tree, huh? (couldn't resist :cyclops