Hermle 321-020 commonality?

Schatznut

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Sep 26, 2020
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I just picked up an inexpensive wall clock with a Hermle 321-020 movement to practice on before moving on to overhaul a movement in another clock that is far more valuable. It appears that the Hermle movement is about the most common one out there, and the fact that there are many variants with different pendulum lengths, and hence beat rates, got me to wondering - how many of the internal parts vary between one using a 35cm pendulum and a 45cm pendulum, for example? Is it only the escape wheel and anchor that change, or are there other differences in the gearing farther down into the time train? Just curious...
 

Willie X

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Feb 9, 2008
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Are you sure that "2" is not a 4 ?

Gear swaps usually involve 2 or 3 arbor assemblies.

These clocks are good for practice and usually worn out from bottom to top. Bottom first and top later ...

Willie X
 

Schatznut

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Sep 26, 2020
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Are you sure that "2" is not a 4 ?

Gear swaps usually involve 2 or 3 arbor assemblies.

These clocks are good for practice and usually worn out from bottom to top. Bottom first and top later ...

Willie X
Yep, 321-020. And it's worn out at the bottom just as you suggest - lots of slop in the pivots opposite the clicks on all three spring barrels, but, amazingly, no significant wear on any of the other pivots. I miked the plates and was surprised to find that they're in imperial units - 0.0625" thick. Bummer. They would have lasted a lot longer if they were 2mm. I recently built my own bushing machine and this will be my first opportunity to try it out.

It also looks like it was serviced by some grease monkey with a Marfak gun. Just getting the grease, congealed oil and gunk off of it is going to be an interesting challenge.
 

Willie X

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The "commonality" of a "321" series Hermle would be about zero? Now, a 341 series would probably be 100s of thousands ...
:) Willie X
 

Schatznut

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The "commonality" of a "321" series Hermle would be about zero? Now, a 341 series would probably be 100s of thousands ...
:) Willie X
I guess I'm not making myself understood, Willie; my apologies. Let me try again. Say I have three different 321-020 Hermle movements sitting on my bench. Each one of them is marked with a different pendulum length and beat rate. How many parts are common between them?
 

Willie X

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Feb 9, 2008
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The 3rd, 4th, & 5th wheels could be different. Many other parts could also be different, depending when your clocks were made. Search for "Hermle 341-020 changing pendulum length". There are charts that will tell you exactly what has to be done for a certain pendulum length.
Willie X
 
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