A striking beauty

Last night your local horologist and spouse had dinner with Ted (and Lisa and Kelsey and Ryan). 

Turn's out Ted's clock was actually from his Grandmother (Nana). So here's to Nana and we'll refer to it as her clock from now on.

In our last episode we were getting Nana's Adamantine bushed, cleaned up and running. 

The movement fully reassembled and the time train seemed to run well but the clock didn't strike.

So keeping time but not striking.

The primary feature of a clock is timekeeping but many clocks have secondary features of striking or chiming or both.

Chiming is when the clock plays a melody on the hour. Classically the Westminster Chimes like Big Ben.

Nana's clock does not have a chiming function but it does have a striking function.

A clock is striking when it hits a gong or bell at the top of the hour, in count with the current hour. So for example "bong, bong, bong" at 3 o'clock, "bong, bong, bong, bong" at 4 o'clock, etc., etc.

American clock striking has been my bugbear. 

Why?

Well I understand a fair bit about striking as I've worked on many striking clocks but somehow getting the striking right on a clock has been, at times, driven more by good fortune than learned efforts.

While I worked on our Adamantine friend it occurred to me that over the last few years I have worked almost exclusively on French, German, Viennese and English clocks.

And of those with striking trains most had a rack and snail striking mechanism and I went through some vigorous learning on how to align the strike on those movements. 

One of the many features I've come to appreciate about rack and snail striking is that most of its components are outside the plates, frequently on the front plate. There are some rods and a few other striking bits on the inside/between the plates but most of the action is outside.

So in the example below (from our beloved DUFA box clock) every part with a green arrow is a key piece of the rack and snail striking mechanism (there's the snail in the middle with the holes).

Take the movement out of the clock and its striking works are right there in front of you. Having so many of the components outside the plates makes configuration much easier.

Not so much for American striking clocks which are almost all built with striking levers and wheels inside (in between) the front and back plates. 

So when you assemble American movements, before fitting the top plate to all those arbors, you have to get all those wheels and levers laid out such that they are aligned in relationship to each another...

... juuuusst right.

Below is a view of Nana's clock with the movement open and I'm laying out the wheels and arbors for striking before I put the other plate back on. 

I've already aligned two levers and related wheels.

Here I'm trying to get different two levers, a rod and a pin aligned.

When the clock is striking that center arbor will spin counterclockwise and its rod will push the J lever. When reassembling the movement the rod can't be up against the J lever. It needs a gap when it starts to strike.

Looks good.

I also have to align the warning wheel pin sticking up on that warning wheel to be about 180 degrees rotation away from the warning lever. It needs a lead time when the warning wheel spins.

Oh I understand that NOW. 

Uh yeah you may have already noticed that I had that warning wheel pin wrongly set up in this photo. The pin is way too close to the warning lever.

And so I found out AFTER I assembled the movement and tested the warning function that my set up didn't work because the pin was too close to the lever.

Time to disassemble the movement again and better align the warning wheel pin relative to the warning lever.

Now you get why it's been a bugbear.

OK I got it this time.

The clock strikes now.

Here's the movement with the time train and the strike train fully installed.

This is the front plate view. The two winding arbors and the center arbor will stick out through the front of the clock.

A few more things to do before we're ready to put this movement back in the case.

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Oh and I made a discovery too!

Warning: deep horology waters ahead!

Remember the brass cock for the anchor saddle pivot? 

No? Well I discussed it here.

And here it is again.

What is that anchor pivot cock for?

It holds the anchor pivot.

Thanks Arnold. 

But why does the anchor pivot need a cock and not just be attached directly to the plate?

Ah...

A quick review of the basics of mechanical timekeeping using some of the earlier, barn-fresh photos.

Looking at the photo below...

The mainspring on the left turns a series of wheels that end on the Escape wheel (pointy teeth).

As the Escape wheel turns (counterclockwise in this view) its teeth hit the pallets in sequence giving it a nudge.

That nudge seesaws the anchor gently up and down as it pivots on the... ahem... pivot.

As it moves back and forth so does its crutch which wraps around the suspension rod (AKA pendulum) that has a hook at the end for the weighted bob (not seen here) which rocks back and forth.

Tick tock.

The pivot holds the anchor and crutch assembly which pivots back and forth as the clock ticks.

The anchor has a brass plate with two holes on each side which slide over the pivot. That brass part is called the saddle.

When the anchor is in place on the pivot it is held there by the black, flat-faced anchor keeper.

You can see the wear pattern on the exit pallet where the escape wheel teeth hit it. That is a minor amount of wear IMO.

This part of the clock where the escape wheel and the pallets of the anchor engaged with each other is referred to collectively as the escapement.

OK DOCTOR CLOCK!!!

What's the darn pivot cock for!? 

Why isn't there just a pivot connected directly to the plate?

OK, OK. I'm coming to it.

Reader(s) who go way back on my blog may dimly recall a post from 4 years ago (where does the time go?) about the topic of locking and dropping.

In short it relates to how deeply (or shallowly) the pallets of the anchor engage with the teeth of the escape wheel.

The drop is the gap between the tip of an escape wheel tooth and the end of the pallet. The lock is another tooth hitting the other pallet and specifically how deeply / far along the face of the pallet it slides.

Here's a screenshot of Kathleen's anniversary clock highlighted from that post 4 years ago. The pallets are angled differently and pallets are above escape wheel (vs. below it on our clock) but you can see the distinct drop on the left and the lock on the right.

In the image below you can see the lock and drop of our nicely cleaned up escapement. I've included some zoomed in bits to help show this. 

On an anchor as it rocks back and forth, one pallet releases a tooth creating the drop and the other pallet is then hit by another tooth creating the lock. Then they alternate, the other tooth drops and the next locks.

Hard to see but on the left there is a drop / gap and on the right there is a lock / tooth hitting the end of the pallet.

OK ready now?

Maybe you've already guessed. 

The pivot cock is attached by that large screw on the left which, when gently loosened, allows you to slide the opposite / pivot end of the cock up and down and correspondingly the pivot and the anchor attached to it.

Push it way up and the anchor pallets jam into the teeth. Push it way down and the pallets and teeth never connect.

Adjust it right in middle and you get a nice drop and lock on the teeth and pallets.

And getting that locking and dropping juuusst right is key to a well running clock.

Here's a video of now fully assembled movement ticking on the stand. As it zooms in note the alternating lock and drop on each side of the anchor. Pause the movie and slowly advance it. You can really see the locking and dropping. 

Oh and turn up the volume.

Yeah it's been a while since I've worked on an American movement.

I'm impressed with this 19th century design on the escapement.

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Next up...

Back in the case!