Pulley and gear unit: Ø40 × 16 flat pulley with a module 1, 20-tooth gear, Ø8 bore — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/pulley-gear-unit-40-m1-20t-bore8/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown's figure (1868); true size, no printing allowance
Catalog version: 2026-10-20

Overall (mm): length 40.0, width 40.0, height 24.0
- A Ø40 × 16 flat-belt pulley and a module 1, 20-tooth spur gear (pitch Ø20, 8 mm face) made in one piece, running loose on a Ø8 shaft: whichever unit the belt is on drives the gear cluster beside it, so shifting the belt changes speed.
- Xem Studio design following Brown's figure; true size, no printing allowance (apply your own to the mating features).

dimension  value
pulley  Ø40 × 16
gear  module 1, 20 T, pitch Ø20, 8 face
bore  Ø8 (runs loose)

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
- Xem Studio: drawing — web — Publisher's page; dimensions are facts — https://xemstudio.com/objects/belt-shifted-gears-two-speed-mechanism/

Free files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/pulley-gear-unit-40-m1-20t-bore8/index.json
API: https://xemstudio.com/api/geometry?object=pulley-gear-unit-40-m1-20t-bore8