Modern Grandfather Clock

As a kid, I was fascinated with watches, clocks and especially the giant grandfather clocks. In 1973, I decided to invent and build my own hyper-modern version of a grandfather clock!

I bought four slabs of beautiful walnut wood, and cut them and screwed them together to form the main frame of a grandfather clock. I had also made grooves near the front and back edges so I could mount 1/4" plate glass in, so I had a closed rectangular box, which could be looked through from front to back.


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If I had had very long wood drills I would have bored passageways through the wood blocks for wires to pass through, but since I did not, I had to use a router to make internal grooves for the needed wires, and then glued very thin strips of walnut wood to close up those grooves (to be later sanded before it was all varnished and finished.). About a foot down from the top, I mounted a clear Lexan bar across the inside of this box, where any internal wires would easily be seen, to confirm that no wires were in it. Centered on that crossbar was a small metal fulcrum piece. A 39" metal bar hung on that fulcrum, via a small hole near the top end. At the bottom of that metal bar was a large disk to represent the swinging weight of a grandfather clock. That disk was not all iron but it did contain small iron pieces near each side.

Inside the walnut side wall was a larger circular area routed out. In principle, I should have done that in both sidewalls but for simplicity, I only did one side like that. I wound a coil of copper wire which resembled a bracelet, and that coil was then placed entirely within that new recess, and another thin slice of walnut wood closed that area up to become invisible.

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Here is the premise: When I would send a short pulse of DC electricity to that coil, it became a magnet and it attracted the iron of the swinging pendulum. The pendulum was made to the correct length so that it oscillated with a one-second interval, like all Grandfather Clocks did. A tiny amount of air friction inside the box to the moving pendulum represented some energy loss over time, as did a slight energy loss between the support fulcrum and the hole in the pendulum. Those were not large energy losses, but the pendulum would gradually swing with narrower motions and eventually stop.

So I used a very small electronic circuit as a timer to schedule exactly when I needed to make the magnet work which acted to increase the arc of the pendulum.

The pendulum was NOT attached to any mechanism, and appeared to simply be hanging in space inside the glass-walled box, but it ran continuously and very accurately for many months and years. It was an interesting optical illusion, where no one could figure out how or why it worked!

Above the Lexan crossbar was another crossbar which contained four digital displays, which showed the hour and minute at all times. At that time (1973) the largest such digits were only 3/4" tall, and they were not very bright, so the time display did not seem to be as impressive as the swinging pendulum beneath it!

But it was certainly a Grandfather Clock which kept impressively accurate time. It also only cost me around $40 to build, and most of that was for the walnut wood!

This presentation was first placed on the Internet in April 2012.

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C Johnson, Theoretical Physicist, Physics Degree from Univ of Chicago