Minute hand springs back when clock strikes the hour

Paddyt

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Jul 22, 2021
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Hello all, I am new to clocks and slowly teaching myself in the art. I have an old Japanese Tokei Donkamaki that I am playing around with. I am trying to set the correct position of the minute hand when it strikes the hour. The “Levers of American Striking Movements” is a great resource. The issue I am running into is the minute hand gets to the vertical position, the striking starts and then the minute hand jumps back about 2 minutes. There is no play between the hand and the shaft, the play is with the shaft. Any thoughts on how to stop the jump back?

Please excuse my lack of knowledge of the correct terminology, I’m still trying to learn my way through it.
 

John P

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Strike hammer could be resting on minute shaft causing a jump of the hand when thru striking.
 

shutterbug

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Or you might have a lifting lever binding a bit, and when it drops off, the minute arbor reacts to being unencumbered again.
 

Paddyt

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In the video on the right why is the lever for the strike, under the lifter on the centre shaft?
Isn’t it supposed to stay next to the center shaft and the lifter swings around to come up and lift it into warning. When the lifter finally passes the lever for the strike the lever drops down and strike sequence begins. Or are you referring to something else?

again….please excuse my ignorance.

EE7F05A3-AF95-4529-B59A-AD441921A23C.jpeg F555B8B0-9D86-4183-B91D-A16F11FBDA05.jpeg 3A169DEB-E824-4CD9-80C9-E3989E91F762.jpeg
 

shutterbug

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The minute wheel seems to be moving with the hand. Perhaps the clutch is too loose.
 

Paddyt

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The minute wheel seems to be moving with the hand. Perhaps the clutch is too loose.
So it looks like the center shaft has a lot of play in it and it is very loose. So when the minute hand is to the right, it drops down clockwise and when the minute hand is on the left it drops down counterclockwise.
there is enough weight from the J lever to push against the strike release pin and force it upward. Then then the force is gone the shaft will fall back with gravity.

is there a way to get rid of the slop or put tension on the shaft so it does not move so easily? C2CD8757-A177-4A99-8B67-C3BAA6588C8F.gif F6C7DD32-FDF1-414B-AA5D-93C315328805.gif
 

roughbarked

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The whole shaft is turning so it does not appear that the canon is loose and slipping. I cannot see what the pinion behind the plate and behind the hour wheel on the main shaft is connected to? Perhaps it is not connected because it appears to be turning with the shaft.
The sloppiness can be cured by rebushing.
 
Last edited:

Willie X

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Feb 9, 2008
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I've seen a few where various auto-correction parts had been filed. You may have one of those? Look closely at the hook tips, the lobes of the 4 lobe cam (especially the tall one) and any tabs on the levers that transfers motion from the 4 lobe cam over to the hooks.

On the hour the correction hook should be rising about 2mm higher than the regular stop hook. The correction hook should stop the rotating pin on every quarter and release it only on the hour. The release is not a big movement, only about + .2 mm. That's 2mm extra stroke on the hour with a .2mm clearance at release, measured at the correction hooks tip.

if you don't have similar measurements look for worn, or filed off parts.

Willie
 

bruce linde

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uhm... actual videos are way better than animated gifs... much better resolution and no hesitations that might obscure what's really going on. and, the 'lightbox' functionality that shows larger versions of photos does not support animated gifs.

take videos with your phone, upload to youtube, and then copy and paste the urls here.
 

shutterbug

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heck the back plate center bushing too. I'm guessing you'll have lots of movement there.
 

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