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This is a stage prop for the theatrical play "The Father" by playwright Florian Zeller (here is an article from the NY Times about it). "The Father" tells us about André, 80 years old, father of two daughters, widower, suffering from dementia. He lives alone in his flat in Paris and tries to show his daugther, that he still can take care of himself. But slowly things start to change: the flat seems to be different, things are missplaced. Time shifts between now and then...

The play jumps around in time. To give the audience an orientation about when in time we are, the creative team wanted to have a large clock hanging over the center of the stage. This clock should be able to speed up and slow down, turn backwards and forwards...

That's where I came into play as head of the props department and passionate tinkerer. As the clock should be hanging in mid air, there was absolutly no possibility to do this manually. So it was my job to come up with a different solution...

Step 1: Research and Collecting Parts

I did a lot of searching on the web to get ideas and tried some stuff on various clocks we had on storage. From similar experiments on previous plays I knew, that it had to be a really solid metal clockwork, because this cheap plastic stuff isn't up to the forces of fast spinning motors. I happened to get my hands on a old city clock, which had a very simple clockwork. I found out that it was a part of a master and slave timing system. This clockwork seemed very easy to manipulate from outside, but it was in no working order, as some had cut off all the wires.

So now I knew, what to look out for an finally found a big railroadstation clock on ebay for a good price. While I was on the hunt for the clock, I did some research about how to get a slave clock to work without a master and found a guy somewhere in bavaria, selling various kinds of impulse generators for slave clocks. Obviously there is a market for this kind of thing...

So now I had the right clock and an impulse generator to make the clock work as a clock. But that was only the basics. I needed to be able to control the clock remotly. So I needed a motor an something to control it. Sounds like a RC-car to me. So I headed to the storage dug up the box in which good old Toto was hiding an took him apart....

To build the framework for the motor I took again the metal construction sets for kids from eitech and I ordered some stuff like cables, plugs, battery packs to start with. Later in the game where some additional cog wheels an other stuff. You will see, as we go along.

Step 2: Make the Clock Work As a Clock

After some research, this was by far the easiest part. I hooked up the impuls generator to the clockwork, wired the battery packs and all was set.

Step 3: Transfer of Power, Part 1

At first I tried a very direct approach. On the back of the clockwork was a small wheel to set the time. I connected it directly to the motor with a short plastic tube (pictures 1-5). I hooked up the motor to the rc-equipment and gave it a try (see video)
It worked fine, and the hands of the clock were spinning very fast.

But I soon realized, that the motor could spin the clockwork, but the clockwork was to weak to spin the motor. So I had to come up with something different.

I fixed a small gear on the clocks axle and pushed it with the tooth side into a round piece of pvc (I drilled the center hole slightly smaller than the gear). On the motor axle I left a piece of plastic tube from the first version, and now I had a basic version of a clutch/transmission system (see the last video). Now I just had to make it controllable by my RC-remote....

Step 4: Transfer of Power, Part 2

In the last step I explained how I came up with my transmission system. Now it's all about making it work by RC.

First I needed a platform to build upon. The clock is made from very sturdy sheet metal so it would be less then comfortable to drill in for my trial and error approach. So I made base from a round piece of plywood I had laying around in storage, cut a slot for the hanger and a round hole for the clockwork. Done.

Next part was to somehow make a casing for the motor. For this I used the eitech parts I mentioned in the first step. I had to adapt them a little, but it worked fine. The hinge needed some adaption as well. Then I fixed it to my baseplate, so that the axle of the motor lined up with the center of my pvc-disc.

Then I added in the servo to lift up or pull down the motor as needed. The round servo wheel didn't provide enough travel, but the star shape worked really well. So I could fix the servo to the baseplate.

Step 5: Transfer of Power, Part 3

Now I worked on the transmission part. To get better force transmission I started to try various approaches.

The main problem was, that the axle of the motor wasn't round. You can see it in the first picture of this step: one side was flat to provide better torque when you fixe a gear directly onto it. My main problem was, that in the beginning I had no such fitting gear at all. So I had to find a workaround.

I started with a small clear rubber hose which had the perfect diameter and a very thight fit, but still: not round.

So I stuck another bigger piece of hose over it. Better, but still: not round.

In a box full of various springs I found one which I could push snug over the smaller piece of tube and then push the larger piece over it. The complete setup still fitted on the axle, so: even better, but still not round enough and thus to noisy.

At this stage I added an extra wheel on top of the disc to keep it level and as a bonus this reduced the rattling noises as well. But still I wasn't there yet.

So my next approach was that I replaced the spring by a piece of brass tube. This worked fine and I was almost where I wanted to get. To refine this I let the motor spin at high speed an held a piece of sandpaper to the rubberhose to sand it perfectly round. Done!..... Done?

It was ok now, but I felt I still could get it a bit better, so I ordered various gears and belt pulleys to try out and finally found one that could accomodate a piece of rubberhose. Now I could finally call the transmission part done for good!

Step 6: Tweaking and Noise Cancelling Part 1

Especially in the beginning the rattling noise of the whole setup was very loud. Especially as the whole clock is built from sheet metal it works like a huge resonance chamber. So I had to put some effort into noise cancelling.

The first step was to add a layer of felt inbetween my wooden plattform and the metal back of the watch face. I used the wood as template, cut some leftover felt strips into shape and fixed them with double sided tape to the back of the clock and then also with tape the wood to the felt.

That was fairly easy, but created a new set of problems: all the carefully adjusted distances were off now. So I had to rearrange motor and transmission disc. Just look at the pictures and you will get it...

Step 7: Tweaking and Noise Cancelling Part 2

With the transmission readjusted, I added two hanging points (to avoid the clock turning around, when hanging in midair over the stage).

In the same step I added another layer of thin felt between the watch face and the back of the watch.

Then I filled up all the empty space on the rear side with foam, and covered it all up with a large round piece of thick felt.

Step 8: Tweaking Part 3

To accomodate the two battery packs I used an old tobacco box to make a battery case.

To avoid battery drainage between shows, I soldered a large on-off-switch into the wiring.

Step 9: Tweaking Part 4

When not perfectly in neutral position the cruise controller emits an annoying high pitched noise. To avoid that and to easyly find the center position I made a half disc of pvc sheet with a small nook in the center and stuck it to the remote control (no need for left and right control in this setup as the clutch is controlled with the left lever)

Just a little extra: to film and in the same time controll the clock, I rigged my camera directly to the remote... ;-)

While trying out the clock I quickly found out that the battery pack had not enough power to last long, so I decided to use the small battery packs just for the clock and bought a bigger one for the RC-setup. I moved the battery box to the side of the impulse generator and placed the new big battery pack in the center underneath the whole setup. The large battery pack is hold in place by some eitech parts and velcro.

Step 10: Final Touches

To wrap this all up I had to fix all the foam to the inside and the felt cover to the back. I killed to birds with one stone with the following setup:

The foam was fixed to the wood with long screws an large washers. Onto the lower washers I added counterparts for magnets. The upper screws went through felt AND foam. On the top screws I used the same spacing as on the lower ones, to be able to keep the flap open when necessary.

Then I added magnets to the inside of the felt to keep the flap in place. To keep the edge clean I added a thin strip of felt with double sided tape around the inside edge and tucked the felt flap underneath. But I soon realized that the felt strip didn't stick very well to the double sided tape. So I exchanged it against some window insulation. This doesn't look as nice and "organic" as the felt, but it sticks to the metal...

Later I added a cover for the motor cage to protect it from "hits" from behind (the daily use of props in the theatre is sometimes a bit rough).

The last addition was a possibility to recharge the big battery pack without the need to open the back cover. I soldered the corresponding wires to the other side of the switch. Like this it's only possible to charge the battery pack when the system is shut down and the charging plugs are disconnected when the system is on. The extra wires are completely hidden underneath the foam..

Step 11: On Stage

Finally the play had it's premiere. Here you can see some pictures from the play (© by Martin Kaufhold, set design by Mona Hapke, the actors on the images are Karlheinz Glaser and Aglaja Stadelmann).
In the embedded youtube trailer, you can see the clock in action at the very beginning and at about 1:17.

<p>Very clever device, maybe you could have implemented a DMX control as well.</p>
<p>Thanks! Actually I thought about using DMX control, but as I have no experience working with it I stuck with the &quot;hands-on&quot; way.<br>But as I'm slowly working my way into the &quot;raspberry-pi-cosmos&quot; at the moment, I might be able to control my next similar device with my smartphone or tablet... ;-)</p>

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Bio: I'm a swiss guy, living in germany and working as head of the props department in a small opera house. On the job and ... More »
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