Kundo 400 day torsion clock
Kundo 400 day torsion clock

Some clock repair folks (horologists) love working on anniversary clocks and some just cannot seem to bond with them. I am in the former camp that finds them intriguing and interesting to work on.

90% of the time the only thing wrong with these clocks is a broken suspension spring

I have 5 anniversary clocks in my collection, none of which are valuable and none that have cost me any more than $30. It’s a shame because they are fascinating devices. They are well-made, delicate and ornamental spring driven clocks. Many thousands were made and this is reflected in their low value today. I stay away from battery operated anniversary clocks that are still being sold and collect the older mechanical ones, the last of which were made over 30 years ago.

There are Gustav Becker, Haller and Schatz 400-day clocks that are more desirable, better made and fetch higher prices but I do not have any of those. I would be prepared to pay a little more for those but I am still looking.

Movement before cleaning
Movement prior to cleaning and showing verdigris on the spring barrel

I bought this for $5 at a local antique store. There is no point in buying one of these no matter how low the price so it is best to see if all the parts are there. 90% of the time the only thing wrong is a broken suspension spring. There are no missing parts on this one and it was in generally good shape. However, the suspension spring had been snapped off due to improper transport. People forget (or don’t know) that they have very effective pendulum locking mechanisms.

It is very important not to get it kinked or bent. A bent spring is the number one cause of these clocks not working properly

These are called torsion clocks because there is a weighted disk or wheel, often a decorative wheel with 3 or 4 chrome or brass balls on ornate spokes, suspended by a thin wire or ribbon called a torsion spring otherwise known as a suspension spring. The torsion pendulum rotates about the vertical axis of the wire, twisting it, instead of swinging like an ordinary pendulum. These clocks move very slowly and in the case of this Kundo Junior, 10 beats a minute compared to 100 beats per minute or more on a typical pendulum mantel clock. Because the gears move slowly there is minimal wear on the gears and plates and it is very common to find these clocks with a broken suspension spring as the only thing wrong with them.

Front plate removed
Front plate removed

The movement was disassembled and cleaned in an ultrasonic cleaner. The mainspring was taken out of the barrel, cleaned and serviced. I have never installed a bushing in an anniversary clock because they run so slowly.

Now to install the new suspension spring. The suspension spring is just a very thin piece of steel running down the back of the clock and it’s purpose is to twist back and forth while suspending the pendulum balls. It is very important not to get it kinked or bent. A bent or crimped spring is the number one reason these clocks do not work properly.

You can buy the pre-assembled suspension spring in kit form, that is, buy the springs already assembled in the blocks and fork but I have found that it is far cheaper to buy the springs separately and re-use the blocks and fork. I consult my Horolovar manual (yes, I eventually bought one) to find the exact template (in this case the Kundo 5E), unscrew the blocks and fork and install the new spring. Here is an example of a suspension spring from a Kern 400 day clock.

suspension spring installed on a Kern
New suspension spring installed on a Kern
The old spring was very twisted

A little patience is required to install the suspension spring. It is a delicate process but it is a relatively easy to do. It is best done on a flat surface. There are screws on the bottom and top block that must be released before the new spring is inserted. The bottom block was a little stubborn and a jewelers screwdriver is must, you don’t want to strip those tiny screws. Use the template in the Horolovar manual as your guide. For Kern above I employed a bit of guesswork because I had not yet obtained the manual. Once the blocks are in place the fork is attached and screwed securely in place.

Install the bottom block first. Attach the spring block to the 4 pendulum balls with the pin then lock the pendulum balls in place using the locking lever. Some 400 day clocks use a simpler bottom block solution that simply hooks the block into place. Because this one uses a pin it is a bit more frustrating. After the bottom block is secured and locked in place install the top block to the top mount by first slipping the fork over the verge post. In the case of this Kundo it is a small side screw that secures the top block to the mount (saddle?).

I then attached the dial face and the hands then gave the pendulum a gentle 360 degree spin. Not surprisingly the clock failed to maintain its spin. An adjustment was required.

As your look at the top of the clock you will see there is a screw that loosens to turn the fork one way or the other. Be very careful not to kink the suspension spring when loosening this screw. Loosen the screw gently, just enough to be able to move it and when you adjust it take small incremental steps. You can purchase a beat adjustment tool for 400 day clocks but with a little trial and error by observing the action of the verge and moving the beat setter, you will eventually find the correct beat. You will hear an even beat when the time between the tick and the tock is the same. The clock will be “in beat” and should run perfectly. Because the ticking is so quiet try to turn off any sounds in the room when you do this. I have several loud ticking clocks in my office and I stop them.

The clock has been running for several weeks and is in the process of being regulated. Above the pendulum balls in a regulating adjustment dial. You will see a “+” and a “-“.  Adjusting towards the plus side speeds up the clock and minus slows it down. I recommend eighth and quarter turns for either adjustment.

There is some debate whether or not to oil these clocks because the gears move so slowly. Although polishing the pivots to reduce friction certainly helps I tend to think that a little pivot oil is never a bad thing.

As I said, I am in the camp that enjoys working on 400 day clocks.