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An update on the 8 day Thommen aircraft dash clock as a good enough mechanical chronometer. After 4 months of accurate running the repaired Thommen 8 day clock stopped for good :(( The movement was removed and partially disassembled until a broken gear shaft at a jewelled bearing was discovered. The broken clock has been retired for parts and a similar Thommen has been purchased as a replacement. This time a Thommen aircraft clock described to be in great working condition was obtained on Ebay for $125. The replacement clock is identical to the original except for an ETA feature built into the dial crystal. This I'm guessing is to give a pilot quick time to arrival information.

Now the rating of the replacement begins. Hoping for 5 seconds per day or better.

Greg Rudzinski

From: Greg Rudzinski
Date: 2015 May 10, 09:18 -0700

Took an Ebay chance on a Thommen 8 day aircraft clock (7 jewels) that was not working for $45.  The clocked arrived not running as described. As soon as the dial glass was removed the second hand started to move. A very very lucky fix :)) The movement was not fully seated and secured by the two screws in the back of the case which caused the second hand to jam against either the dial glass or the minute hand. Adjusting the rate was more difficult. For this a digital stopwatch was used as a master reference. Small adjustments over the course of a day got the clock close to begin a long term rating. The first 24 hours came in with a loss of 8 seconds which is close enough for me on this type of time piece. Hopefully this rate will hold over the coming weeks and increasing temperatures. The Thommen makes for a good companion to a Longines 8 day aircraft clock which I already have. One clock set to UT and the other set to zone time.

Greg Rudzinski

 

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