Weighted belt tightener: pulley on a slide pulled by a hanging weight — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/weighted-belt-tightener-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown No. 23 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- The driven pulley turns on a slide that runs on guide rods; a weight hung from the slide pulls it away from the driver, so the belt stays at the same tension however it stretches.
- Belt tension ≈ half the weight's pull per strand: a 394.58 g steel weight gives about 1.94 N in each strand. Here Ø80 driver over a Ø40 pulley 150 mm below, 16 × 1.5 belt of 491.17 mm.
- Brown's No. 23 (hanging, weighted tightener on a sliding frame).
- Parts (each has its own page): flanged-flat-pulley-40, flanged-flat-pulley-80, flat-belt-16x1-5-pulleys-40-80-c150, tightener-slide-8mm-stub, hanging-weight-d40x40-lug, linear-shafts-h6, dowel-pins-metric.
- Brown's movement No. 23 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
pulleys  Ø80 above Ø40, 150 mm
slide  60 × 20 × 10 on 2 × Ø6 rods
weight  Ø40 × 40 (394.58 g steel)
belt  16 × 1.5, 491.17 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. 23: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_023.html

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