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.

How cuckoo clock music is supposed to work

Below you can watch a movie (visit our YouTube channel!) with a cuckoo music box functioning properly. Sometimes minor adjustments need to be made to the two arms connecting the clock mechanism to the music mechanism. As you watch the video, pay attention to the two black arms that reach in from the left side. One on top and one in the middle (touching the spinning fan-fly or governor).



In the first part of the video you see one cuckoo call and music right away. The second part shows how the music mechanism is first started by the cuckoo mechanism, held while the cuckoo calls, and then released to allow it to play.

The thicker, black metal arm on top unlatches the music drum and the music mechanism so that the drum starts to turn. It is abruptly stopped however by the second, thinner wire that touches the brass fan-fly. This stopping wire remains in place until the cuckoo bird has finished its call.

If this second wire didn't stop the fan-fly from spinning, the music would play while the cuckoo bird calls and cause cacophony.

Once the bird has finished the call the wire gets out of the way, allowing the fan-fly to spin and the music to play.

As the tune reaches its end, the black metal finger on top should be far enough away from the music box arm below it to allow the latch to fall in the hole and stop the music.

Watch the video again:



This video is provided as an example of how this SHOULD work. If you make adjustments to your cuckoo clock music make sure that they are INCREMENTAL adjustments. The tiniest change in the placement of these two arms will be all the adjustment you should make. Any adjustments to either the clock or the music mechanism should be done by a trained professional. The gears, teeth, and wheels inside either mechanism are very delicate and precise. Please don't try to make repairs to either mechanism, but you may try to make tiny adjustments to the two wires that connect the two mechanisms as described above.

NOTE: The movie here shows a music mechanism in an 8-day cuckoo clock. This is important because most 8-day clocks don't allow the music to play on the half-hour.

NOTE: The clock featured in this movie is the 2005 award winner of the VDS Clock of the Year. This clock was produced as a limited edition of only 111 pieces for the 111th anniversary of Rombach und Haas.

A few pieces are still available: