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On several previous posts, I noted that some Schatz miniature 400 day clocks (model 53 movement) needed a 0.0024 inch thick suspension spring (whereas the Horolovar 400 Day Clock Repair Guide specifies a 0.0023 inch spring).

I just experienced this again – this week I repaired a Schatz “London Coach” 400 day clock (which has the model 53 movement). The clock ran too slow with a Horolovar 0.0023 inch spring. With a 0.0024 inch spring, it keeps good time.

I measured the thickness of the 0.0023 inch springs, and they are closer to 0.0022 inch thick. It may be that a batch of springs were made too thin, or were mislabeled.

I experienced the same thing with a Kundo miniature 400 day clock this week.  With a “0.0023 inch” spring, It needed to have the pendulum regulated almost all the way toward fast to get the clock to keep time. A 0.024 inch spring allowed the clock to keep good time with the regulator near the center of its adjustment.

Conclusion: if a Kundo or Schatz niniature 400 day clock loses time with a 0.023 inch Horolovar suspension spring, install a 0.0024 inch spring.

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Suspension Spring Units for Schatz 400 Day and 1000 Day Clocks

Schatz clocks have a model number inside a circle on the back plate (49, 53, 54 or JUM/7). The other numbers on the back of a Schatz clock are the date code (month and year). Here are the suspension spring unit numbers for Schatz 400 day and 1000 day clocks:

• Schatz standard size clock (49 on back plate): Unit 6789 (0.004 inch thick spring)
• Schatz miniature (53 on back plate): Unit 10A (0.023 inch thick spring)
• Schatz 1000 day clock (54 on back plate): Unit 10B (0.0024 inch thick spring)
• Schatz midget 400 day clock (JUM/7 on back plate): Unit 10C (0.0022 inch thick spring)

I am not a general clock parts supplier, but I can sell you Horolovar suspension units for $35 each, plus $8 per order for shipping and handling. To order, you may pay on my online payment page. You may contact me through my BillsClockworks.com web site.

I guarantee that the units are Genuine Horolovar units. I cannot guarantee that they will work in your clock without adjustment, for several reasons:

• Your clock may need servicing or escapement adjustment;
• The pendulum’s moment of inertia may be slightly above or below standard;
• The fork may need to be moved up or down slightly for optimum pendulum motion;
• Also, please be sure that the tines of the fork are not binding on the anchor pin (the vertical pin that moves back and forth as the clock ticks).
• Make sure that the upper block does not wobble sideways in its holder (the saddle).

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A company called Horolovar makes suspension springs for 400 day clocks. Various thicknesses are available. If the spring is too thick the clock will gain time, and if too thin it will lose time

Suspension Spring Thickness for Schatz 400 Day and 1000 Day Clocks

Schatz clocks have a model number inside a circle on the back plate (49, 53, 54 or JUM/7). The other numbers on the back of a Schatz clock are the date code (month and year). Here are the suspension spring thicknesses for Schatz 400 day and 1000 day clocks:

• Schatz standard size clock (49 on back plate): .004 inch
• Schatz miniature (53 on back plate): .0023 inch (Note 4-8-12: I now recommend a 0.0024 inch thick spring)
• Schatz 1000 day clock (54 on back plate): .0024 inch
• Schatz midget 400 day clock (JUM/7 on back plate): .0022 inch

Suspension Spring Thickness for Kundo 400 Day Clocks

• Kundo full sized clock (about 12″ tall): .0032 inch
• Kundo miniature clock (about 9″ tall, including the oval base model): .0023 inch (Note 4-8-12: I now recommend a 0.0024 inch thick spring)
• Kundo midget (similar to the miniature but the anchor pin has an offset bend and makes contact with the fork slightly behind the back plate): .0022 inch

For other clocks, you will need the Horolovar 400 Day Clock Repair Guide to determine the proper spring thickness. Note: measuring the old spring’s thickness is not a reliable method, as the spring may not be a Horolovar brand spring. The Repair Guide and suspension springs are available from Norkro.com and other clock parts suppliers.

The thicknesses given above are for genuine Horolovar suspension springs, which most clock suppliers sell. You may want to ask to be sure you are getting Horolovar suspension springs.

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