Byzantine Sundial-Calendar

This is an ancient device remade with modern technology. The Byzantine sundial-calendar is the second oldest known device to use gears. It is estimated to have been made 1500 years ago. This project is a mostly 3D printed model based on the paper titled “Gears from the Byzantines: A Portable Sundial with Calendrical Gearing” written by J. V. Field and M. T, Wright published in 1985 Annals Of Science, 42 (1985), 87-138. This paper is available online and is an interesting read. Only 4 pieces of the original device survive: the front face, the arm, the input gear and the moon phase/age gear. The rest is guessed at from what information is available. The front and back face engravings are based on the images from the Field and Wright paper. All of the text is in the original Byzantine Greek. I have included a guide to reading this text at the end of these instructions. I have adapted their design to be compatible with 3D printing with the engravings being done by a diode laser engraver. My method of securing the various gears is almost certainly not how the original was done but it works well with 3d printing and is well balanced so that, when reading the time, the sundial hangs vertically. Because this is painted plastic, it will not handle frequent use with out showing wear. It is not highly durable. It is a way of making a nice display piece and an interesting way to model the technology inexpensively to those who already have a 3d printer and laser engraver. Everything is fully functional so you can experiment with how this device could have been used.

3D Printer (largest printed piece is 140 mm x 140 mm)

Laser Engraver (a 5W diode laser should work fine), (largest engraved piece is 140 mm x 140 mm)

1 M3 x 12 mm machine screw with matching nut

PLA printer filament (black, gold or bronze colored, and other colors if you like)

Spray paint that adheres to plastic in a bronzish colored gold and silver

CA Glue

Scrap cardboard

Sheet of paper

All of the files needed for this project can be found for free at Printables: https://www.printables.com/model/956274-byzantine-sundial-calendar

A layer height of 0.2 mm works well. I used PLA, but any material should work fine. To be historically accurate everything should be colored bronze except the moon phase dial. Trace evidence indicates that is was coated with silver colored metal. The 3 engraved parts should be printed in black and painted bronze or silver. See the printing notes below.

Print 1 each of the following stl files except print 2 of the new moons.

Part # ........Part Name .............Notes

1 ...............Front Face ..............Engraved part. Orient face down. Print in black.

2 ...............Input .......................Support needed.

3 ................Input retaining pin

4 ................Input washer

5 ................Arm ........................Support needed.

7 ................Ring body

8 ................Center pin ..............Support needed.

9 ................Vane

10.............. Moon zodiac gear ...Support needed. Orient dial face up. If your slicer will allow, change the color on the layer before the moon symbol and then back for the top layers.

11 ..............Moon gear ...............Support needed. Engraved part. Orient face down. Print in black.

12 ..............Transfer gear ...........Support needed.

13 ..............Sun zodiac gear ......Support needed. Orient dial face up. If your slicer will allow, change the color on the layer before the moon symbol and then back for the top layers.

14 ..............Revised back ...........Engraved part. Orient face down. Print in black.

15 ..............New moon ...............Print 2

16.............. Center pin retainer

17 ..............Spring

18 ..............Shackle

20 ..............Suspension ring....... Support may be needed.

There are three engraved parts, the front face, the revised back, and the moon gear. The general technique for each is the same. Each part to be engraved has a SVG file. Green is for cutting the cardboard, blue is for engraving the part, black to score lines and red is not used.

First 3d print the parts. Use a color that contrast the paint as this color will be the color of the text and lines. I used black for the front and back and for the moon gear. The face to be engraved is printed down on the plate to give it a smooth surface. Before painting, make sure that the parts fit in the holes and move freely. You may need to do some light filing.

Next spray paint only the face to be engraved. I used gold for the front and back faces and silver for the moon gear. On the front and back faces you will want to paint the outside edge too. You may want to mask the holes in the face to eliminate the need to clean them up later. Several light coats applied from different directions works best. Let dry.

Next prepare for engraving. The bottoms of the parts to be engraved are not flat. Also aligning the engraving on the part is difficult. The solution that I used was to use the laser to cut holes in cardboard and then set the part to be engraved such that the protrusions on the bottom of the part align with the holes in the cardboard. This both correctly locates and orients the part. I used 2 – 3 sheets of scrap cardboard from old shipping boxes. The total thickness needs to be greater than the extension of the protrusions and it needs to be flat. The cardboard sheets are held down with some neodymium magnets to keep them from moving during the cutting and engraving steps. Included are SVG files for each part that is to be engraved. You will need to use absolute referencing. To cut the cardboard to make a location and orientation template, use the green features to cut and the black to score reference lines. Turn off the red and blue features. You will need to determine the power and speed setting that work best for your machine. Once this operation is done, remove the inside of the holes that were cut. Do not allow the cardboard to move! If any thing moves, you will need to start over.

Engraving. Place the part so that the protrusions set within these holes and the part lays flat on the card board. You will likely need to refocus the laser. To determine the best setting for the engrave step I just printed a 10 cm PLA square and painted it and tried different settings for power and speed. It doesn't take much to burn off the paint. Now turn off the green and black features of the SVG and turn on the blue and set to engrave. For the moon gear you will want to have both the blue engrave and the black score lines on. The engraving should be just enough to completely remove the paint from the desired areas. Afterwards you may want to apply a clear coat to protect the paint from wear.

You may want to paint the outside of the ring body the same color as the faces.

The paper washer is laser cut from white printer paper using the paper washer dxf file. This just keeps the arm from sticking to the painted surface of the back face.

Glue the ring body to the back of the front face. Let the glue fully set.

Glue the vane to the center pin. The pin should be in the center of the vane.

Slip the suspension ring into the shackle. Bolt the shackle to the arm using the M3 machine screw and nut.

Place the 2 new moons into the moon gear.

Insert the input gear in through the back of the front. Slide the input washer over its shaft and insert the input retaining pin. It should not be so tight that it will not move easily.

Insert the spring next to the input gear so that it engages the ratchet of the input. (leave out if you want to be able to turn the gears backwards.)

Place the moon zodiac gear, the moon gear, the transfer gear and the sun zodiac gear into the back of the front face. While doing this you can orient each dial and gear for the correct day, moon zodiac setting, sun zodiac setting and moon phase/age.

Place the back carefully while aligning all of the gear shafts. While holding the back in place, put the arm in place with the paper washer between the arm and back face. Insert the center pin with vane and finally the center pin retainer to hold everything together.

Sun Dial:

Set the pointer on the arm to your latitude.

Set the vane pointer to the current month. For the 1st 6 months use the pointer at the top; for the last 6 months use the pointer on the bottom of the vane.

Suspend the device by the suspension ring.

Orient the face of the sundial so that the shadow of the gnomon falls on the vane.

Read the hour from the shadow of the gnomon on the vane. Each mark represents 1 hour. The mark furthest from the gnomon is noon.

Note: In this way of measuring time, each day has exactly 12 daylight hours and 12 hours of night. The length of the hour varies throughout the year and, except on the equinoxes, the length of the night hour is different from the day hour.

Calendar: Advance the day of the week input each day. Read the position of the sun and moon relative to the zodiac on the back. Moon phase and age are also indicated on the back. Due to the less than perfect precision of the gear ratios, occasional adjustment to the wheels may need to be made manually by removing the back and adjusting the orientation of the various dials and gears.

See the use instructions PDF to interpret the Byzantine Greek characters and numbers.