Defying gravity

Neighbor Chip the antiques dealer stopped by a few weeks back and placed a clock on the kitchen table. 

Chip provided little information, playfully leaving it for his horologically obsessed neighbor to ascertain what's what.

The next day this clock curious cat had it on the shop bench.

Well, well, well.

Your local horologist recognized this type of clock but had never seen one in the wild.

It's known as a Gravity clock sometimes also referred to as a Saw or Sawtooth clock. Gravity clocks have been around for quite some time. Earliest examples reportedly go back to the 17th century. Here is a lovely example dated to 1829. 

Don't let the "Anno 1750" fool you. Our example is a modern reproduction. Probably 1970's give or take. 

Our gravity clock is quite small. The dial is just a bit over 3 inches in diameter. The pendulum itself is about 3.5 inches long.

This clock hunter has never seen a clock with a pendulum that protrudes out from the top of the dial like that. And yes the pendulum swings over the face of the dial!

The Germans have a term, "Vorderzappler", for clocks with pendulums that swing in front of the dial. Loosely translated to "front wiggler" or "cow's tail" pendulums. Here is an older example of one that is not a gravity clock.

Wow.

Gravity clocks sit / ride on a toothed, brass rod AKA a rack. With our clock the rack is secured on each end to a carved back board. 

Here's the full clock as received, laying on its back on YLH's workbench. 

In normal operation that backboard and the whole apparatus is hung on the wall vertically. 

The clock movement is encased in a very heavy iron housing. Maybe 2-3 pounds or so. That brass rack runs through the body of the clock. 

The rack is anchored to a post on each end of the back board with the effect of raising the rack about a 1/2 inch off the face of the board. This gives the case clearance to move along the rack without rubbing the board.

How does it run?

As the learned reader might recall virtually all mechanical clocks are powered by weights or springs. Well this clock has no mainspring. 

What is does have is gearing inside that engages with the teeth of that brass rack. The weight of that heavy case provides the power to drive the clock. 

To wind it the clock is raised / lifted up to the top of the rack. It clicks as it is moved along along the rack. Yes just like the click when winding practically all mechanical clocks. 

Once raised to the top of the rack the clock is released and then, once ticking, it slowly descends downward.

This is a 30 hour clock, AKA a "one-day", meaning the clock "falls" down the length of the rack over the course of about 30 hours. 

Except this one just falls. 

During examination YLH could observe that the clock wound up correctly, clicking away as it was lifted, but it was clear that something was amiss. Had butter hook simply stood the clock up it could have actually crashed down to the bottom of the rack. 

Indeed the clock wasn't engaging with the rack properly on the way down. Sometimes it seemed to lock on the rack and then suddenly it wasn't and would slip down the rack. Something was not engaging correctly inside the clock to allow it to be powered and run securely and correctly. 

Something was probably broken.

Ah. 

OK Chip.

Challenge accepted.

But what mysteries would be found inside that case?

Stay tuned for our next episode dear reader and discover the mystery of the crashing not ticking clock.