Introduction: A 'Universal' Clock

This clock can show the time in 24 time zones of the world; this performance is achieved thanks to the arrangement represented in the drawing showing the basic components of the clock.

The clockwork 1 is installed in the support 2 which can turn around an axis fixed in the base 3. The hour dial 4 is also fixed to the base 3; however, the minute dial 5 is installed on one of the output shafts of the clockwork (in fact, the alarm hand was replaced by this dial). When the clockworks turns together with its support, the hour hand 6 displaces from one hour mark to another depending on the time zone to which the clock is ‘tuned’ at the given moment. However, the minute dial turns together with the clockwork, so the minute hand doesn’t change its position relative to this dial when the hour is changed. A disk with the names of the cities corresponding to various time zones is attached to the rotating support, and the user can see which city corresponds to the chosen hour through a window in the hour dial.

In fact, two cities would be seen through this window, the time difference between them being 12 hours. However, a slider with 2 openings installed above the window (not shown in the drawing) allows the user to see one or the other city; the city shown in the lower opening is 12 hours ahead of the city appearing in the upper opening.

The times shown correspond to the summer time (see Reference).



electromechanical clockwork

1.5 V AA battery


2 mm thick cardboard

1 mm thick cardboard

8 mm thick plywood

a piece of 2 mm diameter steel rod

a piece of 0.5 mm thick tin

a piece of 2 mm thick plastic

thick drawing paper

printer paper


black paint


Xacto knife

saw for wood

drill with 2 mm drilling bit


brush for paint brush for glue hard pencil

Step 1: Rotating Support

The pieces necessary to manufacture the support are shown in the scan. The 12-sided part where the clockwork will be installed, as well as the arms are made of 2 mm thick cardboard; the hub is made of 8 mm thick plywood.

A 2 mm diameter hole will be drilled in the centre of the hub; it’s important to make this hole strictly perpendicular to the surface of the hub to assure smooth rotation of the support. First, you assemble the arms with the hub; then you install the subassembly into the 12-sided part. The centre of the hub must be strictly over the centre of the figure; for this purpose, it’s advisable to proceed as follows:

draw the contour of the figure on a flat wooden board

drill a 2 mm diameter hole in the centre of the figure and install a piece (about 40 mm long) of 2 mm diameter rod in the hole; the rod must be perpendicular to the board

place the 12-sided part on the board so it fits into the drawn contour

put the subassembly ‘hub-arms’ onto the rod and find the right position of the arms on the 12-sided part

The support will be painted black except the surface where the disk with the names of cities will be placed.

Step 2: Base

The base consists of the plate and the bracket; the parts of the base are also shown in the scan with the part of the support. They are made of 8 mm thick plywood. The vertical part of the bracket is at 80 deg to the horizontal surface; therefore, the hour dial will be also inclined. I thought it would be better visible to the user in this position.

A 2 mm diameter hole for the axis of the rotating support is drilled in the vertical part of the bracket; it’s important that the hole be strictly perpendicular to the surface of the vertical part where the hub will sit.

The axis is a piece of 2 mm diameter steel rod glued into the respective hole in the bracket. The bracket is glued into the base; the assembly will be painted black, except the bottom surface.

Step 3: Disk

It’s is cut out of thick blue paper, its diameter is 116 mm. The disk is divided in 12 sectors each corresponding to 2 time zones with 12 hours difference.

I printed the names of the cities corresponding to various time zones (see Reference), cut them out and glued those small rectangles to their places on the disk. After the paper rectangles are fixed on the disk, the disk itself will be glued onto the 12-sided part of the support as shown in the pictures.

Step 4: Hour Dial

It’s made of 1 mm thick cardboard and thick paper glued onto the cardboard (to make the dial beautiful). There are a central hole in the dial (10 mm diameter) for the shafts of the clockwork, and a window in the upper part of the dial to show the names of the cities. The window is situated 5 mm below the upper edge of the dial, its dimensions are 30 x 15 mm.

I printed the numbers from 0 to 11, cut them out and glued in circular pattern onto the hour dial. Two brackets (see drawing) made of 2 mm thick cardboard will be glued to the dial as shown in the pictures. These brackets will be fixed with small screws to the base of the clock and provide support for the dial; the dial also sit on the front surface of the clockwork.

Step 5: Minute Dial

It’s made of 2 layers of thick paper, its outer diameter is 50 mm, the diameter of the central hole is 5 mm (such is the diameter of the shaft for the alarm clock in the clockwork that I had available). I put some epoxy glue around the edge of the central hole to make it more rigid, because the dial should fit tightly to the shaft.

The numbers from 0 to 55 with the interval of 5 are printed, cut out and glued on the dial.

Step 6: Spring

It serves to stop the disk support in the position exactly corresponding to a city; thus, what you see in the window of the dial is the name of one city, not something in between.

The spring is made of 0.5 … 0.7 mm thick tin according to the drawing.

Step 7: Knobs

I had to replace the original knobs (for setting the time and the alarm) of the clockwork to make the device fit into the support; therefore, I made 2 knobs of 2 mm thick plastic. One for time setting has the diameter of 8 mm, one for the alarm - 6 mm.

I installed both of them; thus, it would be still possible to use the clock as an alarm clock; the minute dial would play the role of the alarm hand.

Step 8: Slider

This part is made of 1 mm thick cardboard and thick paper glued on its face; the basic dimensions of the part are shown in the drawing.

To ply the upper part of the future slider, you could use the technique explained in the picture. The part of the cardboard strip where the bend will be made should be soaked in water, bent around a 1.5 mm thick shim and put under pressure. (For example, a flat wooden bar pressed with a clamp to a table).

I must say that the result of such a proceeding was surprisingly good - a clean bend.

Step 9: Installing the Clockwork

It was necessary to make two small bracket (see picture) of 2 mm thick plastic; they serve to fix the clockwork to the support.

After the clockwork is installed into the support, the latter will be installed onto its axis. Then, the hour dial will be fixed to the base of the clock. After this, the minute dial and the hands (hour, minute, second) will be installed onto their respective shafts of the clockwork.

Step 10: Reference

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