Three speeds by shifting a belt over pulleys carrying gears (16 / 24 / 32 T) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/belt-shifted-gears-three-speed-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown No. 58 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- On the input shaft run loose units each made of a pulley and a gear (16, 24 and 32 teeth) and an idle pulley; the gears mesh with a cluster of 32, 24 and 16 teeth fixed on the output shaft 30 mm away. The belt drives whichever unit it is on: output speed 16/32, 24/24 or 32/16 of the input pulley's — or nothing on the idler.
- Module 1.25 throughout (N₁ + N₂ = 48 keeps one 30 mm centre distance); belt from a wide Ø40 driving pulley 140 mm above, drawn on the 24-tooth unit (1 : 1). Speeds: 0.5, 1, 2 × input.
- Brown's No. 58 (three speeds from a belt shifted across four pulleys carrying spur gears).
- Parts (each has its own page): pulley-gear-unit-40-m1-25-16t-bore8, pulley-gear-unit-40-m1-25-24t-bore8, pulley-gear-unit-40-m1-25-32t-bore8, gear-cluster-m1-25-32-24-16-bore8, plain-flat-pulley-40x16, plain-flat-pulley-40x100, flat-belt-16x1-5-pulleys-40-40-c140, linear-shafts-h6.
- Brown's movement No. 58 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
units  Ø40 pulleys with 16 / 24 / 32 T gears, module 1.25
cluster  32 / 24 / 16 T
speeds  0.5, 1, 2 × input, or stop
centres  30 mm

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. 58: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_058.html

Free files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/belt-shifted-gears-three-speed-mechanism/index.json
API: https://xemstudio.com/api/geometry?object=belt-shifted-gears-three-speed-mechanism