Two speeds by shifting a belt between pulleys carrying gears (20 / 40 T) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/belt-shifted-gears-two-speed-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown No. 59 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- Two loose units on the input shaft, each a pulley with a gear (20 and 40 teeth), mesh with a 40 / 20 cluster on the output shaft. The belt on the 20-tooth unit's pulley gives the output half the pulley's speed; shifted onto the 40-tooth unit, twice — the unit not driven just idles.
- Module 1, 30 mm centres; belt from a wide Ø40 driving pulley 140 mm above, drawn on the 20-tooth unit.
- Brown's No. 59 (two speeds from a belt shifted between pulleys carrying small and large gears).
- Parts (each has its own page): pulley-gear-unit-40-m1-20t-bore8, pulley-gear-unit-40-m1-40t-bore8, gear-cluster-m1-40-20-bore8, plain-flat-pulley-40x66, flat-belt-16x1-5-pulleys-40-40-c140, linear-shafts-h6.
- Brown's movement No. 59 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
units  Ø40 pulleys with 20 / 40 T gears
cluster  40 / 20 T
speeds  0.5, 2 × input
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. 59: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_059.html

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