Crossed belt drive (driven pulley reversed), 2 : 1 — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/crossed-belt-drive-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown No. 2 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- Crossing the belt between two pulleys makes the driven pulley turn the opposite way to the driver; the ratio is still D₂/D₁ (80/40 = 2 : 1).
- Both pulleys get the same wrap, π + 2·asin((R₁ + R₂)/C) = 224.05° here, more than an open belt gives the small pulley, so a crossed belt grips better; the strands rub where they cross, so it suits slow, narrow belts.
- Drawn on the catalog flanged pulleys Ø40 and Ø80 (16 mm faces) at 160 mm centres with a 12 × 1.5 belt, inside length 531.27 mm. Brown's No. 2.
- Parts (each has its own page): flanged-flat-pulley-40, flanged-flat-pulley-80, crossed-flat-belt-12x1-5-pulleys-40-80-c160.
- Brown's movement No. 2 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
pulleys  Ø40 and Ø80, flanged
centres  160 mm
ratio  2 : 1, reversed
wrap (both)  224.05°
belt  12 × 1.5, 531.27 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. 2: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_002.html

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