Ball Clock II ~ Hour Striker Rebuild

by Jon Long Sr on January 7, 2017

Not everything will go as planned in life and none truer right now than this project.  Back from Christmas vacation and back at it.

My original design for the hour striker was pretty simple.  The weight of a ball would cock the hammer and a cam would release it at an interval to provide a time space between strikes. See Photo.

The problem I had to work out was a balance between cocking the hammer and enough weight to make a good strike when the hammer was released.  I tried adding weight to the hammer and even tried a bigger bell.  All the tings I tried worked to some degree, but not enough to make the statement that I wanted.

I had to “Bite the Bullet” as they say and accept the fact that a big change had to be made to the mechanism.  I felt that I could keep the lower mechanism that cocked the hammer in the original design and use it to set up a sequence run by the upper shaft.

Using a spring to power the hammer seemed like a better idea as it could be adjusted.  I could also make a better stop adjustment for the hammer and mount it on bearings.

So the idea was to release the hammer in a way that a cam on the upper shaft could cock it.  At the end of the cocking cycle it would be released by a pawl, which was also adjustable, to strike the bell.  The cam would provide a positive time interval between strikes regardless of when the mechanism was tripped. 

A latch was made to keep the mechanism tripped until a strike occurred. Since there is not fixed relationship between the balls being released into the trip mechanism below and the setup, the latch verified a strike and allowed the process to continue.  There is a relationship between the latch and accepting another ball in the mechanism below.

The first cocking cam had 4 lobes which was a bit slow at 6.0 seconds.  The second version had 5 lobes allowing a strike every 4.8 seconds.  It was important to find the right interval and still not be too fast.

There was another thing to consider also.  When 12 balls were released into the striker trip mechanism, there was only room for 7 balls that were clear of the gate that released them.  The way the hour Ball Selector Cam was made, there was only 27 seconds before the gate would close.    That meant that the striker mechanism had to consume 5 balls at 12 o’clock within 24 seconds.  The smaller hours weren’t an issue as there was more time to clear the gate.

Anyway, the larger bell and spring loaded hammer provides a clear strike.

 

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