Four-bar links: flat links with 20 to 100 mm hole centres — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/four-bar-links/  (CC BY 4.0)
Basis: Flat links 10 wide × 5 thick, Ø3 holes at exact centres from 20 to 100 mm
Catalog version: 2026-10-20

Sizes: see table below
- Seven lengths: 20, 30, 40, 50, 60, 80 and 100 mm between hole centres.
- Ø3 holes at both ends for Ø3 pins, so links pin to each other, to the bell cranks and to the Scotch yoke rod.
- Builds crank-rockers, parallel motions, rocking beams and the Ross yoke linkage.

centres  width × thickness  holes
20 mm  10 × 5  Ø3
30 mm  10 × 5  Ø3
40 mm  10 × 5  Ø3
50 mm  10 × 5  Ø3
60 mm  10 × 5  Ø3
80 mm  10 × 5  Ø3
100 mm  10 × 5  Ø3

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Wikipedia: Four-bar linkage — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/Four-bar_linkage
- Long Earth Society: Engine and rig builds on extrusion frames — web, video — LES site — https://longearthsociety.com/engineering/

Free files (CC BY 4.0, Xem Studio; STEP + STL, 7 parts): https://xemstudio.com/files/hardware/four-bar-links/index.json
API: https://xemstudio.com/api/geometry?object=four-bar-links