Stepped cone pulleys (three speeds by moving the belt) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/stepped-cone-pulleys-mechanism/  (CC BY 4.0)
Basis: Xem Studio design following Brown No. 8 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- Two identical stepped pulleys mounted head to tail: moving the belt from one step pair to another changes the speed ratio — 50/30 = 1.67, 40/40 = 1, 30/50 = 0.6 — while the belt length stays the same because each pair's diameters add to 80 mm.
- Drawn with the belt on the middle (Ø40 / Ø40) steps, shafts 120 mm apart; belt inside length 365.66 mm.
- Brown's No. 8 (speed pulleys); the classic lathe and drill-press drive.
- Parts (each has its own page): stepped-cone-pulley-50-40-30, flat-belt-1-5x16-pulleys-40-120.
- Brown's movement No. 8 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
steps  Ø50 / Ø40 / Ø30 (×2, reversed)
ratios  1.67, 1, 0.6
shaft centres  120 mm
belt  16 × 1.5 flat

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Henry T. Brown (1868, public domain): Five Hundred and Seven Mechanical Movements — scan on archive.org — web — Publisher's page; dimensions are facts — https://archive.org/details/fivehundredseven00browiala
- 507movements.com: Brown's movement No. 8: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_008.html

Free files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/stepped-cone-pulleys-mechanism/index.json
API: https://xemstudio.com/api/geometry?object=stepped-cone-pulleys-mechanism