Stand and deliver

In our last episode your local horologist was frustrated in his efforts to diagnose the movement of the Vienna single weight regulator without the ability to mount the movement and pendulum in a stand.

The Viennas are one of the few models of clocks where the pendulum is attached to the back board of the case and does not hang from the movement itself.

And the way the pendulum engages with the movement is... 

Hmm... 

On a practical level it is easier for your correspondent (and photo essayist) to explain how this engagement occurs by taking advantage of the decoupling of movement, pendulum and case required for this testing effort.

So...

Here is the movement freshly removed from the case. The dial is still attached.

Those slats slide into the mounting bracket in the case. Note the crutch descending from the top of the movement -- it has a pin attached to a mechanism at the bottom. 

Here's a close up.

That pin protrudes perpendicularly from the end of the crutch. The mechanism with the thumbscrews and threaded rod allow adjustment of the position of the pin. It's the way a Vienna is adjusted to be put in beat. The pin itself engages with a slot in the pendulum rod.

The pendulum hooks onto that suspension spring (here is a similar, illustrated example) and is suspended hanging against the back of the case. When the movement is installed it is slid into the case along those rails and the crutch pin is guided into the slot on the pendulum rod. When the clock runs the crutch swings and the pin nudges the pendulum back and forth.

So...

Any effort to test this movement and pendulum requires a way to hang the pendulum, independently from the movement, in such a way that they will precisely align and allow the pin to slot correctly in the pendulum rod.

Is there are way to do this?

This is a longstanding question that comes up not infrequently on the NAWCC message boards. In fact there is a thread with a fellow asking precisely "is there a movement holder device for Vienna regulators?"

Some horologists remove the bracket from the case. That seemed like it could create other problems and the bracket would still have to be mounted on something. 

On that NAWCC thread, real horologist Willie X. notes that he just tests the movement in his hand. Well he's a genius and this clock doc is nowhere near that talented.

But another long-time NAWCC clock guru, Shutterbug, made a concise recommendation that was exactly what your aspiring mechanical engineer had already started to envision as a fairly simple way to recreate this engagement outside the case.

Something like this:

YLH had an extra suspension bridge and suspension springs that should work -- at least for a test stand. Here's a closeup of the top of the board that served as the "case" for the suspension bridge.

And here is the movement being carefully aligned so that the crutch pin inserts correctly into the pendulum rod slot.

 From opposite angle.

And here's the bird's-eye view. 

Almost there. Steady now.

Mission accomplished.

Finally the clocks weight was added. YLH forgot to mention that the ability to hang the weight to drive the movement was an essential capability of the setup of the test stand. 

It all has to run with its weight as it would in its case.

One more view.

And here's the money shot.

Were the kind reader to expand the image to full screen they might be able to discern an escape wheel tooth landing on the face of the entrance pallet.

Don't worry if you can't. YLH could.

And in that view (and others not shown here) this clock doc could now figure out what was slowing / stopping our Vienna clock movement.

And he did.

It's actually shown in the image above.

Don't. It's way to hard to extrapolate from that shot.

All shall be revealed.

Next time.