Bent Steel

The pendulum regulates the speed of a clock and without that pendulum a wound clock movement can run mighty fast.

In our last episode your local horologist was wrestling with making fine adjustments to the pendulum of Charlene's Ingraham Regulator clock. That effort was not about the speed of the movement rather the noisy nature of the pendulum swing. 

However, as we saw in the last video of that episode, the pendulum adjustments did not address all of the noise emanating from... somewhere.

Probably the escapement.

Why there you ask?

Because this clock doc addressed the other likely sources of trouble.

First was the wiggling pendulum bob as explained last time.

Second YLH examined the gap in the crutch loop.

Que?

It has to do with the pendulum. 

Technically the pendulum is more than the shaft and the bob. It also consists of the pendulum rod and the suspension spring right up to the top where that spring (ribbon of steel) slips through and hangs from a brass rod called a cock.

The pendulum moves because it gets a tiny push from the escapement via the crutch with each swing of the pendulum. In many American clocks the crutch and the pendulum connect at the crutch loop [there it is], which, if too wide, can rattle the pendulum rod.

Regardez.

See how the pendulum rod passes through the crutch loop? That's where power is transmitted from the crutch to the pendulum (in little nudges) and that is what keeps the pendulum swinging. The crutch loop is meant to have just a little room on either side of the rod so that it doesn't bind. Too much of a gap and it will rattle.

Charlene's crutch loop appeared to be appropriately gapped and was not rattling.

Hmm...

Working from the bottom up of this noisy pendulum, the bob was now good and the crutch loop was fine.

Yet there still was that extra beat!

Ahem.

What to do?

This clock audiologist tried to further isolate the source of the sound.

Here's a video of the whole pendulum swinging. As your local cinematographer moved in on the escapement, increasingly, that seemed to be the source of the sound. You can clearly hear that double beat on the left to right swing.

Well... things are now pointing to the escapement itself.

But the escapement is the source of the classic and expected tick tock sounds of a clock. We just seemed to have something unexpected happening too. 

Is that a good thing or a bad thing? 

Or a it-doesn't matter thing?

Let's put it this way. If it didn't matter would YLH be making such a big effort to explain all this? 

Nyet comrade.

As more regular readers (raise your hands) may recall, the ticking sound of a mechanical clock comes from the action of its escapement. 

And in order to explain what was happening with this clock, we will need to more deeply understand the function of the escapement.

What is the escapement?

WARNING... we will now have a NOSEDIVE brief foray into the mechanisms that drive the pendulum.

The power in a clock is transmitted from its springs or weights, through the wheel train, ending in the escape wheel which is the last wheel in the train.

Below is an example image of a wheel train (two actually (time and strike trains) but we are only interested in the one on the right (the time train)). Power comes from the wound mainspring at the bottom and travels up the train of wheels to the escape wheel at the top.

Courtesy of Blue Paper Technology

The two primary components of the escapement are the escape wheel itself and the anchor. 

Escape wheels are easy to identify because they are the only wheels in a clock with sharply pointed teeth. The anchor is that steel strip with the curved arms, the pallets. Power from the wheel train is transmitted from the escape wheel to the pallets via the action / motion of the escapement.

Here is the escapement of Charlene's Ingraham captured early in YLH's examination (and prior to cleaning).

The pallets are named entrance and exit because, as the escape wheel turns, the teeth that first engage with the pallet of the anchor are considered to be "entering" the escapement and as they proceed along and subsequently hit and slide off the second pallet, several pendulum swings later, they are considered to be "exiting" the escapement.

With Charlene's escapement the escape wheel turns clockwise and its teeth enter on the right and exit on the left. 

Here YLH will republish a slow motion animated gif from our last episode.

Observe the escape wheel teeth entering and exiting the escapement and note that in doing so they literally collide with the corresponding pallet. This is visible in both pallets above but is more pronounced with the exit pallet on the left.

Those collisions, entrance then exit, are the source of the tick-tock sound of a mechanical clock.

The anchor pivots back and forth because it sits on a pivot rod and it is connected to the crutch which engages with the pendulum. (The kind reader will refer back to the diagramed image near the top of the page outlining the parts of the pendulum and crutch.)

As the anchor pivots the engaged escape wheel tooth slides up a pallet side and then over the pallet face (beveled end). The escape wheel is carrying the energy of the wheel train and its teeth really want to turn so when they crest over the edge of the bevel the angle of the beveled face allows the tooth to push the pallet downward. That powers the pivoting/rocking action of the anchor, which in turn moves the crutch from side to side.

In the following foursquare of images, the exit pallet is in the left column of images, and the entrance pallet is in the right column. 

The top row shows the exit and entrance pallets respectively when the escape wheel tooth is hitting the side of that pallet (making the tick or tock sound). The bottom row shows when those same teeth are sliding over the face of those respective pallets.

Hopefully all of this will coalesce into enlightenment make sense if the patient reader/viewer enjoys the slow motion gif again. 

Power in motion.

END OF the brief foray... 

Thank you for your patience.

OK Professor! We now get how the tick and tock work. 

What about this extra beat on the left to right swing of the pendulum?

Well...

In his efforts of horological exposition YLH often worries about… 

Verbosity.

Expeditions into the weeds.

Long windedness.

Opacity.

And that, in general, when going beyond certain depths, he will straight up bore the kind reader.

And, in this example in particular, the details that underpin our errant sound, will test the geek tolerance of the best of you.

Seeking solace, guidance, moral support, reflection and the advice of council, YLH conferred with brother Scott, gifted proprietor of Johnson Arts.

His advice was along the lines of shaddup and write give it a try.

And so it shall be.

In our next episode.