Orrery

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A clockwork model of the solar system. Turn the crank once and the Earth goes round the Sun once, Mercury a little over four times, the Moon thirteen times round the Earth and Saturn a twenty-ninth of the way. Every planet sits on its own tube; the seven tubes turn inside each other round the Sun's rod and are driven from one layshaft in the gearbox below, with two extra gear stages for slow Jupiter and Saturn. Each orbit is within 0.05% of the real one. Saturn sweeps a circle 41 cm across, and nothing needs supports.

• 43 printed parts

• 29 × 27 × 20 cm assembled (L × W × H)

• ≈ 0.6 kg filament in total

• 200 mm bed size for the drum; Saturn's arm is 25 cm long and goes diagonally on a 22 cm bed

Parts

Drum: The drum the orrery stands on, 20 cm across. Its top is the floor of the gearbox, with the socket for the Sun's rod; underneath it, a tab and a hole in the wall carry the crank shaft.

• Size: 202 × 202 × 65 mm

• Print: Upside down, floor on the bed. No supports: the holes for the crank shaft are teardrops.

• Filament: ≈ 239 g

Top plate: Holds the Saturn tube, which turns in it, and the top of the layshaft. Four pillars hold it above the floor; an M3 × 12 from under the floor goes into each.

• Size: 200 × 200 × 54 mm

• Print: Upside down, pillars up. No supports.

• Filament: ≈ 62 g

Crank: Turn it once and a year goes by.

• Size: 48 × 30 × 16 mm

• Print: Flat, handle up. No supports.

• Filament: ≈ 4 g

Crank shaft: An 8 mm hex shaft from the bevel gear under the floor out through the wall of the drum.

• Size: 48 × 9 × 8 mm

• Print: Lying on a flat side.

• Filament: ≈ 2 g

Crank spacer: Sits on the crank shaft between its bevel gear and the bearing tab.

• Size: 14 × 14 × 6 mm

• Print: Standing on one end.

• Filament: ≈ 1 g

Crank bevel gear: 18 teeth on the inner end of the crank shaft. It turns the layshaft one to one.

• Size: 30 × 30 × 4 mm

• Print: Back face down, teeth up. No supports.

• Filament: ≈ 2 g

Layshaft bevel gear: 18 teeth on the bottom of the layshaft, under the floor.

• Size: 30 × 30 × 4 mm

• Print: Back face down, teeth up. No supports.

• Filament: ≈ 2 g

Layshaft: A 7 mm hex shaft beside the tubes. It turns once a year and carries the bevel gear and the five drive gears; the two sleeves turn freely on its top.

• Size: 66 × 8 × 7 mm

• Print: Lying on a flat side.

• Filament: ≈ 3 g

Mercury drive gear: 54 teeth on the layshaft. It turns Mercury's 13-tooth gear: 4.15 orbits a year.

• Size: 82 × 82 × 6 mm

• Print: Flat, hub up. No supports.

• Filament: ≈ 10 g

Venus drive gear: 39 teeth. It turns Venus's 24-tooth gear: 1.625 orbits a year.

• Size: 65 × 65 × 6 mm

• Print: Flat, hub up. No supports.

• Filament: ≈ 8 g

Moon drive gear: 62 teeth. It turns the Moon tube's 21-tooth gear, 2.95 times a year.

• Size: 77 × 77 × 6 mm

• Print: Flat, hub up. No supports.

• Filament: ≈ 9 g

Earth drive gear: 36 teeth, the same as the Earth's: one orbit a year.

• Size: 53 × 53 × 6 mm

• Print: Flat, hub up. No supports.

• Filament: ≈ 6 g

Mars drive gear: 25 teeth. It turns Mars's 47-tooth gear: 0.53 orbits a year.

• Size: 37 × 37 × 6 mm

• Print: Flat, hub up. No supports.

• Filament: ≈ 4 g

Jupiter sleeve: Turns freely on the layshaft. The Mars tube drives its 40 teeth and its 14 teeth drive Jupiter's 53: one orbit in 11.86 years.

• Size: 65 × 65 × 11 mm

• Print: Big gear down. No supports.

• Filament: ≈ 10 g

Saturn sleeve: Turns freely on the layshaft above the Jupiter sleeve. The Jupiter tube drives its 30 teeth and its 16 teeth drive Saturn's 49: one orbit in 29.5 years.

• Size: 48 × 48 × 11 mm

• Print: Big gear down. No supports.

• Filament: ≈ 8 g

Mercury tube: The innermost and longest tube, round the Sun's rod: the 13-tooth gear at the bottom, a hex for Mercury's arm at the top.

• Size: 96 × 23 × 23 mm

• Print: Standing up, gear down. No supports.

• Filament: ≈ 8 g

Venus tube: 24 teeth at the bottom, Venus's arm at the top.

• Size: 84 × 41 × 41 mm

• Print: Standing up, gear down. No supports.

• Filament: ≈ 13 g

Moon tube: 21 teeth at the bottom. Its top comes out just above the Earth's arm and carries the Moon train's 76-tooth gear.

• Size: 73 × 28 × 28 mm

• Print: Standing up, gear down. No supports.

• Filament: ≈ 10 g

Earth tube: 36 teeth at the bottom, the Earth's arm at the top.

• Size: 62 × 53 × 53 mm

• Print: Standing up, gear down. No supports.

• Filament: ≈ 18 g

Mars tube: 47 teeth for Mars and above them 24 teeth that drive the Jupiter sleeve.

• Size: 68 × 68 × 50 mm

• Print: Standing up, big gear down. No supports.

• Filament: ≈ 21 g

Jupiter tube: 53 teeth for Jupiter and above them 37 teeth that drive the Saturn sleeve.

• Size: 81 × 81 × 33 mm

• Print: Standing up, big gear down. No supports.

• Filament: ≈ 28 g

Saturn tube: The outermost and shortest tube; it turns in the top plate.

• Size: 78 × 78 × 16 mm

• Print: Standing up, gear down. No supports.

• Filament: ≈ 15 g

Saturn arm: 185 mm from the Sun to Saturn's post, with a short tail on the other side.

• Size: 228 × 114 × 52 mm

• Print: Flat, post up. It is 25 cm long: lay it diagonally on a 22 cm bed.

• Filament: ≈ 14 g

Jupiter arm: 145 mm to Jupiter's post.

• Size: 174 × 106 × 47 mm

• Print: Flat, post up. No supports.

• Filament: ≈ 12 g

Mars arm: 112 mm to Mars's post.

• Size: 148 × 63 × 46 mm

• Print: Flat, post up. No supports.

• Filament: ≈ 10 g

Earth arm: 80 mm to the Earth's post, with the stud for the idler of the Moon train on the way. The Moon gear turns round the Earth's post.

• Size: 98 × 50 × 40 mm

• Print: Flat, posts up. No supports.

• Filament: ≈ 7 g

Moon train gear: 76 teeth on the hex at the top of the Moon tube, just above the Earth's arm.

• Size: 98 × 98 × 4 mm

• Print: Flat. No supports.

• Filament: ≈ 13 g

Idler: 20 teeth on the stud of the Earth's arm. It passes the Moon train gear's turning on to the Moon gear at the Earth, the same way round.

• Size: 27 × 27 × 4 mm

• Print: Flat. No supports.

• Filament: ≈ 2 g

Moon gear: 12 teeth with a sleeve round the Earth's post; the Moon's arm sits on the hex at its top. It turns 76/12 times as fast as the Moon tube does, relative to the arm: 13.37 orbits a year in all.

• Size: 26 × 18 × 18 mm

• Print: Gear down, sleeve up. No supports.

• Filament: ≈ 2 g

Moon arm: Holds the Moon 15 mm from the Earth, just under it.

• Size: 21 × 19 × 9 mm

• Print: Flat, post up. No supports.

• Filament: ≈ 1 g

Venus arm: 54 mm to Venus's post.

• Size: 67 × 41 × 28 mm

• Print: Flat, post up. No supports.

• Filament: ≈ 4 g

Mercury arm: 36 mm to Mercury's post. It is the top arm, just under the Sun.

• Size: 49 × 31 × 21 mm

• Print: Flat, post up. No supports.

• Filament: ≈ 3 g

Sun: 44 mm across, on the top of the steel rod. It does not turn.

• Size: 44 × 44 × 38 mm

• Print: On its flat bottom. The bottom is cut at 45°, so no supports.

• Filament: ≈ 16 g

Mercury: 8 mm across.

• Size: 8 × 8 × 7 mm

• Print: On its flat bottom, no supports.

• Filament: ≈ 0 g

Venus: 13 mm across.

• Size: 13 × 13 × 11 mm

• Print: On its flat bottom, no supports.

• Filament: ≈ 1 g

Earth: 15 mm across.

• Size: 15 × 15 × 13 mm

• Print: On its flat bottom, no supports.

• Filament: ≈ 1 g

Moon: 7 mm across.

• Size: 7 × 7 × 6 mm

• Print: On its flat bottom, no supports.

• Filament: ≈ 0 g

Mars: 10 mm across.

• Size: 10 × 10 × 9 mm

• Print: On its flat bottom, no supports.

• Filament: ≈ 1 g

Jupiter: 28 mm across, with its cloud bands as grooves.

• Size: 28 × 28 × 24 mm

• Print: On its flat bottom, no supports.

• Filament: ≈ 5 g

Saturn, lower half: Saturn is tilted 27° on its post; the post goes into the hole in this half.

• Size: 22 × 22 × 11 mm

• Print: Flat face down. No supports.

• Filament: ≈ 2 g

Saturn's ring: 42 mm across, clamped between the two halves.

• Size: 42 × 42 × 2 mm

• Print: Flat.

• Filament: ≈ 3 g

Saturn, upper half: The top of the ball.

• Size: 22 × 22 × 11 mm

• Print: Flat face down. No supports.

• Filament: ≈ 2 g

Saturn peg: Lines up the two halves and the ring.

• Size: 6 × 4 × 4 mm

• Print: Standing up.

• Filament: ≈ 0 g

What else you need

• An 8 mm steel rod, 137 mm long, for the Sun: a piece of 8 mm linear rod or silver steel. A straight 8 mm hardwood dowel works as well.

• 4 × M3 × 12 screws for the pillars. They cut their own thread in the plastic.

• Super glue for the planets on their posts and the gears on the hex shafts.

• Optional: a little dry PTFE lubricant or silicone grease on the tubes.

Print settings

• 0.16 mm layer height

• 3 walls

• 20% infill

• PLA material

For a 0.4 mm nozzle. Filament amounts are estimates for these settings.

How to build it

1. Print the parts: Nothing needs supports. Scrape any elephant's foot off the gears and the ends of the tubes, then slide each tube over the next smaller one: they must turn freely inside each other.

2. Rod and crank: Glue the steel rod into the socket in the middle of the floor. Push the crank shaft through the hole in the wall and the tab inside, slide the spacer and the crank's bevel gear onto its inner end and press the crank onto the outer end.

3. Layshaft: Push the layshaft down through its hole in the floor and press the second bevel gear onto its bottom end, in mesh with the crank's. From the top, slide on the drive gears for Mercury (54 teeth), Venus (39), the Moon tube (62), the Earth (36) and Mars (25), each resting on the hub of the one below.

4. Tubes and sleeves: Slide the tubes over the rod from the inside out: Mercury, Venus, the Moon tube, the Earth and Mars, each gear in mesh with its drive gear. Then put the Jupiter sleeve on the layshaft, the Jupiter tube on the rod, the Saturn sleeve and last the Saturn tube.

5. Top plate: Lower the top plate over the Saturn tube and the top of the layshaft and screw the four pillars down from under the floor with M3 × 12 screws. Turn the crank: every tube should turn.

6. Arms and the Moon train: Press the arms onto the hexes from the bottom up: Saturn, Jupiter, Mars and the Earth. Put the 76-tooth Moon train gear on the Moon tube, the idler on the stud of the Earth's arm and the Moon gear over the Earth's post, then press on the Moon's arm. Finish with the arms of Venus and Mercury.

7. Planets: Glue each planet onto its post and the Sun onto the rod. For Saturn, put the peg through the ring and close the two halves round it, then glue the lower half onto its post. Turn the crank and watch the year go by.

Small parts: keep the planets and the Moon away from young children.

More

3D viewer, colour preview and the full guide: https://shapekit.cc/orrery.html

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