Replacing a gear in the transmission of a Copal flip clock

ID: 206476

Description: Most flip clocks from the Japanese manufacturer...

Steps:

  1. Here is the removed motor with transmission; the cable has been detached.
  2. To avoid confusion, the cables were cut to different lengths.
  3. Solder the cables back on after the repair and insulate them well with heat shrink tubing.
  4. Now the motor must be detached from the transmission.
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  5. Take a suitable flat tool, e.g. a small flathead screwdriver, and carefully pry off the cover on the back of the transmission. You may need to unscrew the tiny Phillips screw in the center.
  6. The cover is attached with repair glue during reassembly.
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  7. Turn the clockwork over.
  8. The transmission is attached to the motor with three rivets. Grind off the rivets with a rotary tool.
  9. When reassembling, apply a drop of repair adhesive to this spot.
  10. Insert a small flathead screwdriver between the transmission and the motor and carefully pry the transmission off.
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  11. The rivets are still protruding from the gearbox cover. Sand them down completely.
  12. Now you can very carefully pry off the gearbox cover. Take care not to damage any of the delicate gears.
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  13. The first gear in the transmission is driven by the metal pinion on the motor shaft. It is under the most load and breaks faster than all others.
  14. Remove the first gear and replace it with a new one.
  15. Spare parts are no longer available. You must create the gear using a 3D print and make it fit exactly.
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  16. Here are the old and the new gear. The old gear is significantly worn down—after over 40 years!
  17. The gear does not fit perfectly right out of the 3D printer. The hole for the axle must be reamed to exactly 1 mm. The outer circumference must be sanded down slightly so that the distance to the second gear of the transmission is as small as possible.
  18. Work as precisely as possible; we are talking about 0.1 mm here. A jeweler might be able to help with a suitable tool.
  19. A hard material (SLA) was printed as finely as possible here so that the gear has the longest possible service life.
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