Follow the sun, planets, ring and carrier in one diagram. Switch between a fixed ring, carrier or sun to compare input/output directions and speeds. Tooth counts and module determine matching gear dimensions.
At 1×, 15 rpm takes 4 seconds per cycle. Playback scale changes elapsed time only, not the motion relationship. Drawing scale stays fixed during playback.
Change blue values → use the button to return to the drawing
m: 0.1–50 mm; integer zs: 18–80, zp: 18–40; zr = zs + 2zp ≤ 160; (zs + zr) divisible by 3. Planets must not overlap. Input: 0.1–3,000 rpm.Blue is input, red is output; a grey lock marks the fixed member. Green planets can spin while orbiting the centre. Follow the shaft markers together with the teeth.
Ideal unshifted planetary gears share module and a 20° reference pressure angle. Ring teeth zr = zs + 2zp. Three equally spaced planets require integer (zs + zr)/3. (ωs − ωc)zs + (ωr − ωc)zr = 0; planet spin is ωp = ωc − zs(ωs − ωc)/zp. Tooth flanks are involutes; root joins are illustrative. Rigid no-slip kinematics exclude backlash, tooth strength, efficiency, load sharing and manufacturing checks.
