Click trick

 

In our last episode your local horologist had discovered, but had yet to reveal, the underlying problem with the Sessions Ramona mainspring.

It took a beat but upon examining the movement this burgeoning metallurgist was proud of his relatively quick espying of the issue. It's right there in the photo above. 

See it?

You do? 

Very good. 

You must be quite a close reader of this blog (or a clockmaker yourself) because in previous posts YLH has talked about the same type of mechanism in other clocks that ended up broken in our Ramona.

You don't see it?

No? 

Well let's briefly review.

What does it mean to "wind" a clock? 

It means using a key to wind up the mainspring which, under the tension of its coils, provides power to the clock.

When you wind a clock with its key why doesn't it just snap back like any other spring when you stretch or push it?

Because as you turn the key a few degrees the click mechanism locks the mainspring wheel in place preventing it from spinning backwards. As you continue to turn the click locks again and again creating that click, click, click you hear as you wind the clock. 

Let's look at a very clear example, our old friend the DUFA box clock.

Your horological explainer picked this one because all the components of the winding and the click mechanisms sit on the outside of the main plate. Easy to see and the action of the click is the same as the Ramona and most every other mechanical clock.

The key is inserted in the clock and goes over the winding arbor. It turns (clockwise) and with it turns the brass ratchet wheel (click wheel). The steel click pivots on its center axis (rivet) and rides up the tooth of the ratchet wheel as it turns. As the wheel continues to turn the tip of the click rides up the tooth of the ratchet wheel, passes the lip of the tooth and then the pressure from the click spring snaps the click down into the gap of the next tooth of the ratchet wheel. 

That snapping downward creates the clicking sound of winding.  

The ratchet wheel is shaped such that the click will lock snugly into the tooth gap. This prevents the winding arbor from turning backwards as the mainspring builds us pressure from winding.

The DUFA has a really nicely made click mechanism. Really robust. 

Now the DUFA is a German clock. American clocks were built more cheaply and had somewhat more... gymnastic click spring solutions.

Most every American clock used some form of a click that was inside the movement and directly attached to the mainspring wheel. 

Here's the mainspring wheel with its click mechanism from Nana's Seth Thomas Adamantine clock that YLH worked on a couple summers ago. 

The click and its circular spring are attached to spokes of the mainspring wheel. 

Note how that click spring makes almost a complete loop around the sun ratchet wheel before it lands on the head of the click, pressing it downwards.

Thus the whole click mechanism is actually attached to the mainspring wheel. 

Here is a gif of YLH testing Nana's clock's mainspring wheel click now fully cleaned. 

Cleaned up well. 

See how the end of the click spring flattens? It slips into a slot on the end of the click. Keeps it snugly in place as it presses downwards.

Here's a very similar one on a New Haven clock. The click wheel spins in the opposite direction.

Here's an example from an Ingraham kitchen clock serviced by your then neophyte horologist 6 years ago.

That one has a flat strip of a spring pressing the click down. 

(Is it pressing down? Gotta check that one again with more seasoned eyes. Good thing it's not in active service.)

Here's a photo of a different Sessions movement with a pristine click mechanism. 

From the NAWCC

The Sessions click mechanism has its click spring attached to the base of the click. The spring is pulled over and tucked under a catch on a spoke of the wheel and that pressure from the spring pulls the back of the click upwards with the force pivoting the front downward onto the ratchet wheel.

And here's that photo from the top of the post now highlighting that it shows our Ramona's click mechanism as YLH found it.

Why is the click completely flipped backwards (rotated clockwise about 300 degrees)?

Probably from the explosive force of the mainspring failing.

OK so we can see that something bad has happened with the click. But why?

This was revealed with just a bit more looking and confirmed once the movement was fully disassembled.

Another quick aside.

As competition for American clocks grew so did the pressure to bring costs down and so descended the quality of the designs of some of these click mechanisms. And with that up goes the risk of failures.

And (coming full circle now)...

Sessions clocks are notorious for their poor click designs and high failure rates.

Ah ha!

(Your local horological smarty pants probably should have remembered this when first evaluating the Ramona and negotiating with Al.)

There are a couple issues with the quality (or lack thereof) of the Sessions click mechanisms.

Most notable is that the click spring itself (in this case really a wire) is made of brass and that is not as tensile nor as strong as the steel click springs used in virtually all other clocks. 

In all the other examples above the click springs are steel. Not the Sessions.

Those brass click springs frequently failed in Sessions clocks. All sorts of models, not just the Ramona.

YLH disassembled this Ramona's movement and got up close and personal with its mainspring wheel.

In the photo below the major portion of click spring is sitting loosely under YLH's thumb. 

That spring snapped at point A-B. Before it broke, the rest of the B part had originally curled over the top of the click to the left and then tucked under the catch on the left spoke. Like the photo above of the pristine Sessions click. 

And in this photo you can see that in fact the click spring had broken before and had been welded back onto the click wheel at some point. 

So likely this spring has broken twice!!

Now we know why that mainspring was dangling. 

The click holds the mainspring tight to the movement. When the click fails during winding the mainspring explosively unwinds uncontrollably. Usually from wound to fully unwound in less than 1 second.

Once that click is broken there is no way to wind the now completely released mainspring without a repair of the click.

Hope nobody got hurt.

So!

Well now...

What are we going to do about this broken click?

How is the mainspring itself? Did anything else in the clock get damaged?

Tune in next time!

updated 4/10/25 adding gif of working click