Crank pin in a slotted bell crank — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/crank-slotted-bell-crank-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown No. 156 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- A crank pin, in a slide block, runs in a slot along one arm of a bell crank pivoted 70 mm from the crank centre: the bell crank rocks through ±9.87° (sin⁻¹ 12/70), with the quick-return timing of a slotted lever, and its second arm, 50 mm long at 90°, carries the motion off at a right angle.
- Drawn at crank angle 200°: bell crank at 9.71°, output pin at (49.28, 8.43).
- Brown's No. 156 (crank pin working in a slotted bell crank).
- Parts (each has its own page): slotted-bell-crank-100-50-slot-50-90-b5, crank-disc-36-pin-r12, slide-block-12x6, dowel-pins-metric.
- Brown's movement No. 156 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
crank radius  12 mm
pivot distance  70 mm
swing  ±9.87°
output arm  50 mm at 90°

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. 156: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_156.html

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