What's a Fusee Anyway??

Let's take a quick look at some of the terms that have been mentioned in recent posts.  To do that, we'll start at the basics of how mechanical clocks are usually powered.

The clocks featured in recent posts are built before the general use of electricity.  Steam engines would normally be too large and inefficient to power such small devices, plus you would have continually stoke it to keep the clock running over night.  So what powers these clocks?

We've discussed examples of the very earliest clocks that run on water power, but the tried and true method of running an accurate timepiece is to harness the power of gravity.  This is the original GREEN power.  Gravity is constantly renewable and reliable.  As long as we have a planet, we have gravity.  Weight-driven clocks also have the advantage of being very accurate.  The force of gravity is always constant in any particular location, so the clock won't speed up or slow down at any point because of an increase or decrease of power.

Weights get in the way sometimes though.  What do you do if you want to make a smaller clock that fits on a shelf?  There would be no room to fit the weights.  Early American clockmakers solved the problem by making really tall shelf clocks with weights hidden in the sides of the case.

Eventually (in the1400's)  the obvious solution became to use the recoiling power of a metal spring.  The spring didn't require the space that weights did, but the power of a spring does diminish as the spring winds down.  This would cause the clock to slightly slow down - hence the Fusee.

The Fusee is essentially a cone shaped wheel, connected to a powered spring barrel.  As the spring applies pressure to the inside of the barrel, it turns, and pulls on the chain connected to the cone.  As the chain is pulled from the cone to the barrel less force is required because of the increasing radius of the cone. This compensates for the weakening power of the spring towards the end of its power cycle.

As you can tell, cutting a fusee accurately requires an expert machinist and craftsman.  Only the finest, most expert clocks incorporated fusees.

Eventually, finicky and delicate fusee mechanisms became obsolete due to more accurate and more reliable advancements in escapements.  Today, very few mechanical clocks have fusees and they have become largely a fascination and curiosity among horologists.

We have several posts that talk about this interesting element of horology.  Click here for more posts about the Fusee.

New problem with your young clock?

Clock movements are really very simple, when you compare them to electronics. Brass clock movements are generally not influenced by all but the most extreme static electricity, temperature fluctuations, humidity changes, or magnetic fields. Once all of a clock movement's wheels have turned 1 revolution, there is no reason why they shouldn't keep making those revolutions for at least 2 years time without service unless some physical change has come to them.

Unless it has been moved or jostled there is no reason to expect that any modern mechanical clock should develop any new problem after a week's worth of good running. If your clock stopped working properly "out of the clear blue sky," take a moment to double check the following:

1. "Is the clock hanging straight?"
Forget about how straight the clock looks on the wall. Use your ears. You should be listening for an even TICK TOCK (listen) sound. If you hear an uneven tick TOCK or TOCK tick (listen) sound, carefully tilt the clock one direction or the other. You can carefully move the bottom of the hanging clock to the right or to the left until you hear that even ticking sound.

2. Flat against the wall.
Make sure that your clock is hanging flat against the wall. There should be no space between the back of the clock and the wall. The clock needs to be hanging exactly parallellel to the wall.

3. Wind the clock fully.
Many times, clock owners will be afraid of winding a spring-wound clock too tightly. Don't be. You can't break the spring. Most mainsprings are about an inch-wide ribbon of tempered steel. Could you imagine breaking this with your own arm... by twisting it?? These springs will break under the stress of age, nothing more. Besides, there is a stop catch built into new mechanisms to provide safety.
Wind the clock until it comes to a complete stop. If you have a key, wind it until it goes no further. If there are weights, wind the clock until the weight comes all the way to the top. DO NOT LIFT the weight with your other hand. There should always be tension on the chain or cable which supports the weight. The cable won't break, you don't need to "help" it.

4. Shut-off switch
Check the shut-off switch and don't trust the markings that label that switch. Sometimes they can be confusing. If your clock is not cuckooing, try the shut-off switch in both positions regardless of what the marker says.

5. Where are your weights?
Make sure the weights are each hanging on the hooks correctly.





6. The cuckoo door
There is a little wire latch which sometimes gets in the way of the cuckoo door. Make sure that this is out of the way so that the door can open.