The leg bone's connected to the...

Happy New Year!

Time for another installment of your local horologist's latest obsession... the "butcher" Morbier clock. In our last episode your correspondent was extolling the history of these Comtoise clocks and the physical qualities of working on them (and how those joys extend to horological work in general).

Now we will dive back into just one of the many elements of this Morbier that this horology detective has never seen in any other clock before. 

On deck today: the dog bone

What?

This:

Let's jump in.

As most reasonably awake readers (thank you) will recall, classic elements of mechanical clocks include a wheel train that provides power to an escapement. The escapement is the heartbeat of a clock. A diagrammed example (from Charlene's Ingraham) is here.

The power from a clock's escapement is regulated by the swings of the pendulum AND is transmitted to the pendulum via a crutch. 

This is one of most commonly misunderstood elements of mechanical clocks. 

Pendulums are not perpetual motion devices. They are powered by wound springs or weights transmitting that power through the wheel train to the escapement.

Pendulums do swing with highly precise and controlled cadences (regulation) but the swing is powered and sustained by tiny pushes from the teeth of the escape wheel. 

Here is the escapement of our Morbier:

Remember that the power transmits up the wheel train to the escape wheel. That train drives a lot of power to the escape wheel but its rotation is limited to tiny ticks forward by its engagement with the pallets of the anchor.

As the anchor rocks the escape wheel teeth alternately fall on and push against the two pallet faces. Here's an escape wheel tooth pushing the exit pallet face.

You can see in both photos above how the pallets / anchor are attached to the crutch. It is connected directly to the arbor of the anchor so that as the anchor rocks back and forth it drives the movement of the crutch.

Here is an animated gif of the action of the escapement.

Each tooth alternately pushes a pallet face and the crutch rocks back and forth accordingly.

Important reminder: the crutch is not the pendulum. The crutch engages with the pendulum.

Here is a gif YLH has used before describing Charlene's Ingraham.

On Charlene's movement the pendulum begins with that thin suspension spring hanging down from the middle of the movement connecting to the black pendulum rod swinging below. The crutch is the brass rod on its right. It's attached to the anchor up in the escapement and descends down alongside the pendulum rod and curls into a loop around around it. 

That's where the power transmission takes place from crutch to pendulum. Each push of the escape wheel teeth transmit from pallets to crutch which gives a tap left or right on that crutch loop.

Those taps keep the pendulum in motion. 

Most clocks have a direct intersection of crutch and pendulum in some variant like the crutch loop above.

Our French Morbier has a crutch and pendulum but they do not hang along side each other nor directly come in contact like most clocks.

First, they hang several inches apart, parallel to one another.

See how the crutch has an elbow that loops around the winding arbor? 

The pendulum rod has a loop in the middle so it can swing around the minute arbor and the wheels sitting on it.

And now we're back to the proverbial dog bone there at the bottom of the movement.

It is a piece of brass with holes on each end. One looped on the end of the crutch. The other affixed to the pendulum rod but allowing it to rotate freely.

Instead of a crutch loop like Charlene's clock... the Morbier uses that dog bone to transmit power from the crutch to the pendulum rod.

Oh and see the top of the pendulum hooked onto the bottom of the rod? That hook is the top of a strip of metal that connects it down to the full pendulum which... 

Just peaks out from the bottom of the dial repoussee when it is all together and running.

This clock is full of wonder.

As is this clock lover.