125 : 1 · three 5 : 1 stages

Three compact 5 : 1 stages, 63 mm across, for solar trackers, telescope mounts and slow turntables.

Stepper gearboxes125 : 13 planets3 stagesRing held

Build it with your AI

Using the CheapCADTools connector, design a 125 : 1 planetary gear set in Planetary Gear Designer: module 1 mm, 20° pressure angle, herringbone teeth, a 12-tooth sun, 18-tooth planets and a 48-tooth ring, three planets, a profile shift of 0.2 on the sun, face width 12 mm, three stages stacked. The sun: a 5 mm bore with a D-flat 0.5 mm deep. The carrier: 6 mm planet pins. The carrier's output: an 8 mm bore. Set an input torque of 0.45 N·m. Check the design, apply any Auto-fix it suggests, then export every part (the sun, a planet, the ring and the carrier) as STEP and STL and give me the download link.

Paste it into Claude, ChatGPT or any AI app with the CheapCADTools connector, and it designs this planetary set with you, checks it and hands you the files. How to connect your AI.

What's in this design

Sun

12 teeth · shift +0.2 · tip Ø14.81 mm · face 12 mm · bore Ø5 mm D-flat (0.5 mm flat) · no hub

Planets · 3

18 teeth · no shift · tip Ø20.62 mm · face 12 mm · bore Ø6.3 mm on a Ø6 mm pin · print 9 (3 a stage)

Ring

48 internal teeth · shift −0.2 · outside Ø62.81 mm · rim 5 mm below the roots · one ring round all three stages, 59 mm long

Carrier

straddle (two discs and posts) · disc Ø47.09 × 5 mm · 3 pins Ø6 × 23.0 mm · output bore Ø8 mm · plus two carriers printed with the next stage's sun

The set · Module 1 · 20° · herringbone

125 : 1 reduction in three 5 : 1 stages: the ring is held (one ring round every stage), the sun is the input, each carrier drives the next stage's sun and the last carrier is the output.

Notes

Hardware: 9 × planet pin Ø6 × 23.0 mm; 9 × M3 screw, about 11 mm long.
3 stages, one under the other: each carrier but the last carries the next stage's sun on its underside, one part; print it sun down, with supports under its disc.
The Strength check rates spur sets only: helical and herringbone sets aren't rated yet.

The link opens the whole set in the Planetary Gear Designer's 3D view. Change the teeth, the number of planets or stages, which member is held, the carrier, bores or hubs, then download STL, STEP or the carrier's DXF and SVG.

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