When to rebush?

ticktock

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Aug 24, 2004
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Working on a Gilbert Time and Strike 8 day. Standard movement from the 1930's.
What is the rule for the amount of play before replacing the custom bushings on the mainspring wheels? There is some movement but not eliptical.

tick
 

shutterbug

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I make note of any movement, then while it's apart closely inspect the suspect holes. If they're round I'll probably let them ride unless the amount of slop is just unbearable :) I figure it's been running that way, so let well enough alone. However, there's always a chance that either the hole has been reamed or the pivot size reduced by repairers, so your 'clock sense' comes into play.
 

antiekeradio

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What is the rule for the amount of play before replacing the custom bushings on the mainspring wheels? There is some movement but not eliptical.
assemble the plates with the mainspring wheels and the wheels driven by it.

Turn the mainspring wheel while heavily braking the rotation of the second wheel. When turning, push the mainspring wheel either towards or from the driven wheel, or any other direction where there is play.

If there is any position where you can clearly feel the transfer of power is not smooth, you do need to rebush.

If the wheels run relatively smooth together in all attainable positions, you do not need to rebush.

Play in bushings always needs to be considered in direct relation with the teeth whose interaction is affected by the play. a wheel that has few teeth with a large modulus working on wide pinion leaves can take much more play than a wheel with a large number of small teeth, running on a small pinion.
 

ticktock

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Aug 24, 2004
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assemble the plates with the mainspring wheels and the wheels driven by it.

Turn the mainspring wheel while heavily braking the rotation of the second wheel. When turning, push the mainspring wheel either towards or from the driven wheel, or any other direction where there is play.

If there is any position where you can clearly feel the transfer of power is not smooth, you do need to rebush.

If the wheels run relatively smooth together in all attainable positions, you do not need to rebush.

Play in bushings always needs to be considered in direct relation with the teeth whose interaction is affected by the play. a wheel that has few teeth with a large modulus working on wide pinion leaves can take much more play than a wheel with a large number of small teeth, running on a small pinion.
Very Interesting! Thank You for that insightful comment.

tick
 

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