Hanging a Suspension Spring on a 400 Day Clock

A couple of Anniversary Clocks in need of new Suspension Springs
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I picked up these two anniversary clocks at a local antique shop, one for $20.00 and the other for $10.00. Whenever I find these type of clocks, I always assume I'll need to replace the suspension spring so mentally add in that expense for my total cost. It's really quite easy to do and for most of these kind of clocks, it's about all you'll ever need to do for them. Since they beat so slow and they are protected under their glass domes, they rarely exhibit any wear. As it turns out, even though the one on the left appeared to have the pendulum in place, I found a surprise as you'll read about later if you make it through the rest of this.


Black dial

One thing I really liked about this Anniversary clock was the black dial and flower decorations. It's a little bit different than any of my other 400 day clocks, which makes it a good candidate to join the collection.


Looking up the movements in Terwilliger

If you're going to do any work on 400 day clocks, the first thing you'll need to do is get a copy of the acknowledged "bible" for Anniversary Clocks, the Horolovar 400 Day Clock Repair Guide by Charles Terwilliger. Here I learn that my Euramca Trading Corp. clock was made in 1952 (which is my birth year too!) and also find the suspension spring replacement details. The black dialed Kundo is much more recent, being made in 1976.


Suspension Spring Pattern

The Terwilliger book has actual size sillouettes that you can use as a pattern to make your replacement with bulk suspension spring wire. Complete assembled suspension spring units are also available if you find you're missing the fork, top, or bottom block pieces. When you have the book with the patterns, building the suspension assembly is as simple as laying the pieces on top of the diagram and tightening the pieces in place.


Holding the top block steady while tightening block screws

Take care not to kink or bend the new suspension wire while attaching it to the blocks and fork. This photo shows a way to hold the block steady with a small hand vise so you can securely tighten the block screws without placing any strain on the delicate suspension wire.



After removing the suspension spring cover/guard from the Kundo, I was surprised to find that some well meaning, but ignorant amateur had replaced the suspension spring wire with fishing line! Of course the clock would never run that way, though it might fool someone since the pendulum could rotate for several minutes. Like I said earlier, I always expect to install a new suspension spring anyhow, so this didn't bother me, in fact this probable helped keep the price down to a reasonable "as is" level.


Mounting the top block

It's very important to be sure the top suspension block is tightened enough to take up any excessive slack space, but not so tight that the suspension wire cannot adjust itself to hang staight down. If too loose, there will be a loss of impulse power to the pendulum and the clock will stop. If too tight, the suspension wire cannot automatically align itself to hang straight and could put a bend or kink in your suspension spring.


Replace the suspension spring cover

Don't forget to reinstall the suspension spring cover and replace any other pendulum locking pieces you may have removed. The spring cover improves the time keeping quality of the clock by reducing temperature variations. Many of the clocks I find are missing these pieces since lazy owners don't always bother to replace them and they get lost. Of course the clock will still run without them, but it's always more desirable to have everything complete.


Ready for timing and bench test

Now the clocks are ready for timing and beat adjustments. First be sure the clocks are perfectly level. I always start with all three of the leveling feet in in their fully in position. Then make the minimum change necessary to only two of the feet to bring it level. I used my Windows Timing Machine program to help set the pendulums in beat and to adjust them for an 8 beats/minute rate. To adjust the beat, slightly turn the top block mounting piece until the pendulum rotates an equal amount in both directions after a tooth is released from its pallet. If you listen carefully, you can hear each tick as a tooth is released and make a mental note of how many degrees the pendulum continues until it stops and reverses it direction. To adjust to time, rotate the rating nut adjustment in the + direction to go faster or towards - to slow down. These both ended up running within a couple minutes per week which is about as good as you can expect for these clocks.


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