Antikythera Orrery (3d Printed)

by Zac Apelt in Workshop > 3D Printing

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Antikythera Orrery (3d Printed)

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3d printed Antikythera Mechanism

The Antikythera mechanism was estimated to be first built between 150 - 100 BC. The Ancient Greeks made this device to precisely know the position of the planets in the sky at any point in time. At this point in history, it was assumed that the Earth was in the centre of the universe, and so the position and the movement of the planets became extraordinarily complicated, leading to the use of mechanical epicycles. In addition, the Greeks didn't know about Uranus or Neptune so they are not included in the model. There are very few functioning models of the Antikythera and I wanted to share the astonishing complexity in an accessible way.

All the files are part of each step or can be found on my GrabCad page: https://grabcad.com/zac.apelt-1

A .step file is also available.

I'd like to give a huge thanks to Lawrence Cuthbert for an awesome starting point in the project. Further acknowledgements and references can be found in the last section of this Instructables. The relevant licencing of this project can be found in my GrabCad with the rest of the model.

Supplies

Any type of plastic (I used PLA)

~30 M3 screws

20cm M8 threaded rod

15cm 6mm metal rod

70cm 4mm metal rod

1m 1mm wire

Base

stationary base.jpg

First things first, the base needs to be printed. This file is called 'plate stationary', 3x 'foot' also needs to be printed. As well as that, all the files containing 'moon' needs to be printed. glue the 3 feet onto the base as seen in the image.

Moon 7

moon 7 and rod.jpg

screw the M8 threaded rod through 'moon 7' and slide the rod and gear into the base so that the gear is on the bottom.

Moon 6

moon 6.jpg

slide the shaft on 'moon 6' into the hole near 'moon 7' so that the 2 gears engage. use 'moon 6 cap' as a washer and screw the gear in so that it can't fall out. It is important in all steps that the gears can rotate as freely as possible but are still secure

Moon 5

moon 5.jpg

slide 'moon 5' into the remaining hole so that it engages with 'moon 6' and spins freely

Moon 4

moon 4.jpg

slide 'moon 4' onto 'moon 5' on the other side of the base. Use 'moon 4 cap' as a washer once again to hold these two gears together. It is omitted from the image for clarity.

Moon 2 + 3

moon 2 + 3.jpg

slide 'moon 2 + 3' onto the shaft on the base so that it engages with 'moon 4'. Secure it with 'moon 2 cap' which is once again omitted from the image for clarity.

Moon 1 & Main Gear

moon 1 and main gear.jpg

glue 'moon 1' to 'main gear' which is the largest gear. orientation does not matter.

Downloads

Attaching Main Gear

moon and main gear.jpg

Slide the moon 1 and main gear assembly onto the centre shaft so that 'moon 1' engages with 'moon 2'.

At this point, it is vital that when the main gear is rotated and the base remains fixed, the threaded rod rotates. If this does not occur or it binds, you may need to loosen some screws or sand a big off a shaft.

True Sun Epicycle

true sun epicycle 1, 2 & 3.jpg

On the main shaft, slide on 'true sun epicycle 1'. This should remain fixed with the base and not rotate.

screw on 'true sun epicycle 2' in the middle and 'true sun epicycle 3' further out so that they all engage.

The point of having a True sun pointer is to correct for the elliptical nature of Earth's orbit, pretty impressive for 2000 years ago!

Mercury and Venus Spacer

mercury and venus spacers.jpg

attach 'mercury planet gear spacer' and 'venus planet gear spacer' with 2 screws each as seen in the image.

Mercury Epicycle

mercury epicycle.jpg

Print the 2 Mercury gears, attach the larger to the middle so that it is fixed to the base (doesn't rotate) and screw the smaller gear to the Mercury spacer.

Venus Epicycle

venus epicycle.jpg

Same deal as before, small mercury gear attaches to the middle so that it can't rotate and the larger gear gets screwed into the spacer.

Tubes

s, m, v tubes.jpg

Now the fun bit! Slide the tubes into each other and use longer M3 screws to constrain them to the posts on the gears.

The idea of this is that the motion of the tubes is a non-constant angular velocity to model the elliptical orbits and the fact that they believed the Earth was in the centre of the Universe.

Make sure that this works by rotating the large gear and holding the base. All 3 arms and tubes should rotate. If it binds at this point, you need to fix it because it'll just get worse.

Date

date tube to extension of main gear.jpg

Glue the 'date tube' to 'extension of main gear' as seen in the image.

The Antikythera is basically a glorified calendar and this reads the date.

Attaching the Date Tube

extension of main gear.jpg

Place the extension of the main gear and the date tube onto the main gear and screw it to the main gear with 12 screws.

At this point, put this assembly aside.

Top Section

stationary sun gears.jpg

This is where the tricky bits begin.

slide 'stationary sun gears' into 'extension of main gear bigger'. These gears should be able to rotate but later on, you'll see that these gears are stationary relative to the base as the black bit spins around. It'll all make sense soon, I promise.

Mars, Jupiter & Saturn Gears

mjs top gears.jpg

Slide the 'jupiter 1', 'saturn 1' and 'mars 1' over the shafts. There is only one way that they can go on and engage with the corresponding gears.

Mars, Jupiter & Saturn Spacers and Shafts

mjs spacer and shafts.jpg

Cut 3 50mm shafts from 6mm metal rod and insert them into the holes so that they are flush with the bottom. place the 'mars spacer' and 'saturn spacer' on the shafts of their respective gears.

Saturn

saturn gear and tube.jpg

Slide the 'saturn tube' into the 'stationary sun gears' (printed earlier) and make sure it can rotate freely. Put the 'saturn 2' gear onto the Saturn shaft so that the post of 'saturn 1' engages with the slot of 'saturn 2'

Rotate the 'sun gears' to make sure the Saturn epicycle is functioning.

Jupiter

jupiter 2.jpg

Repeat the same procedure for the 'jupiter tube' and 'jupiter 2' gear. The only difference is that instead of a pin engaging with the slot, a long M3 screw is used in place.

It may seem as though the two gears won't stay engaged, but this will soon be flipped over so gravity will be on our side.

Mars

mars tube.jpg

This is the exact same procedure as Saturn.

Putting It Together

full assembly.jpg

Flip the previous assembly over and screw it onto the other half.

At this point, hold the base and rotate the large gear. The top half should be independent and none of the top gears should rotate. Now hold the outermost shaft (sun gears), the Mars, Jupiter and Saturn gears should all rotate freely at different speeds.

Coupling the Two Halves

top and bottom connected.jpg

Print 'wire connector' and put it on the largest shaft. Bend the 4mm wire into a shape that connects 'wire connector' to the horizontal holes in the base. Make sure the wires give the mechanism sufficient clearance, it's a pain if you don't measure it properly, ask me how I know!

Downloads

Adding the Planets

wire and planets.jpg

Print the parts named 'sun wire', 'mercury wire', 'venus wire', 'date wire', 'mars wire', 'jupiter wire', 'saturn wire', 'sun', 'mercury', venus', 'mars', 'jupiter' and 'saturn'.

glue the rings onto their corresponding shafts and use 1m of 1mm wire to bend the wire to attach the planets. The wire without the planet corresponds to the date and should rotate with main gear.

For Saturn's ring, I used some thinner wire and soldered it to support the ring around the planet.

Moon Part 1

moon shaft.jpg
moon shaft cross section.jpg

Print 'moon' and 'moon shaft'.

Slide the moon over the shaft and make sure it can spin very freely

Moon Part 2

moon bevel.jpg

Print 'moon gear' and 'moon gear 2'.

place 'moon gear 2' into place and then slide 'moon gear' so that the D shaft engages with the corresponding hole.

by turning 'moon gear', the moon should rotate on it's axis. This is used to demonstrate lunar phases.

Attaching the Moon

moon assembly.jpg

glue the shaft to the threaded rod.

By rotating the main gear, the mon should rotate on 2 axes. If it becomes difficult to turn, you may have to loosen the tolerances on the gears to make it very smooth.

Final Remarks

full thing.jpg

I have plans to add a stepper motor but at the moment, it's hand-cranked, like the original.

Credit:

this Wikipedia page provided most of the technical and historical information for the project: https://en.wikipedia.org/wiki/Antikythera_mechanism#:~:text=The%20Antikythera%20mechanism%20(%2F%CB%8C%C3%A6,and%20eclipses%20decades%20in%20advance.

Chris from the YouTube channel, Clickspring provided the inspiration for this project, he does some really amazing stuff and is recreating it authentically with original tools and techniques.

https://www.youtube.com/watch?v=ML4tw_UzqZE&list=PLZioPDnFPNsHnyxfygxA0to4RXv4_jDU2

I didn't design it from scratch, it was heavily based on this model but converted into a model that is able to be printed: https://grabcad.com/library/antikythera-mechanism-4