Rocking shaft driving an upright shaft continuously through two opposed ratchets and bevel gears — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/opposed-ratchets-bevel-gears-rocking-mechanism/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design following Brown No. 49 (1868)
Catalog version: 2026-10-20

Sizes: see table below
- Resize: multiply every length by one factor k and the motion stays identical: angles, ratios, timing and the formulas below do not change, because a mechanism's motion depends only on the ratios of its lengths. Here, stays the same: gears, ratchets.
- Resize: fit clearances stay in mm (a slide fit is the same gap at any size); keep every printed wall and pin at least two nozzle widths; mass grows with k³ but part strength only with k², so at k = 2 parts are about 8× heavier and 4× stronger: check pins and thin links when scaling up.
- Two mitre gears ride loose on the rocking cross shaft, facing each other across a third gear on the upright shaft. Each carries a ratchet wheel; a pawl on an arm keyed to the cross shaft drives each, the two ratchets set opposite ways.
- Rocking one way, pawl A drives gear A; rocking back, pawl B drives gear B. Because A and B sit on opposite sides of the upright gear, both turn it the same way: the upright shaft goes round (almost) continuously while the cross shaft only rocks.
- Built from three module 2, 24-tooth spherical-involute mitre gears (cone distance 33.94 mm) and two copies of the catalog 24-tooth ratchet, feed pawl and feed arm (Brown No. 225 parts); the gears were checked in mesh at six angles. Brown's No. 49.
- Parts (each has its own page): mitre-gear-m2-24t-bore5, ratchet-wheels, ratchet-feed-pawl-24t-d40, ratchet-feed-arm-30, linear-shafts-h6.
- Brown's movement No. 49 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.

parameter  value
gears  3 × mitre, module 2, 24 T
ratchets  2 × 24 T Ø40, opposite hands
input  cross shaft rocking
output  upright shaft, one direction

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. 49: figure, his text and an animation — web — Publisher's page; dimensions are facts — https://507movements.com/mm_049.html

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