Bell-crank lever turning a pull through 90° — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/bell-crank-lever-mechanism/  (CC BY 4.0)
Basis: Xem Studio design following Brown No. 126 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- An L-shaped lever on a pivot at its corner: a pull on one arm becomes a pull at right angles on the other. Force ratio = arm lengths (1 : 1 for 30 × 30 mm; the 20 × 40 crank gives 2 : 1).
- Here the catalog 30 × 30 bell crank turns on a 623 bearing pressed in its Ø10 pocket, with 60 mm links on each arm.
- Brown's No. 126; used in bell-pulls, control rods and brakes to change the direction of a push or pull.
- Parts (each has its own page): bell-cranks, ball-bearings-metric, four-bar-links, dowel-pins-metric.
- Brown's movement No. 126 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
arms  30 × 30 mm at 90°
pivot  623 bearing on Ø3 pin
links  2 × 60 mm
ratio  1 : 1

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. 126: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_126.html

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