OK - here we are - patented by Wren and Hopkinson in 1866, this was an attempt to reduce the footprint of slate dressers by fitting two into (roughly) the space of one and a half. Greaves did the same thing with his double sided dresser, but in the process lost the main advantage of his rotary dresser by forcing the actual dressing rotor to oscillate.
Here there are two working blades and fixed edges operated from cranks on the shaft above the machine which itself was driven by the usual fast and loose pulley arrangement.
The original patent drawing shows an iron frame. (The drawing needs re-doing as I hastily traced the patent many years ago):
🔗Personal-Album-54-Image-49731[linkphoto]Personal-Album-54-Image-49731[/linkphoto][/link]
While the machines at Diffwys Floor 6 Mill clearly had wooden frames. This is my reconstruction sketch based on what we found there. (AGain this is in great need of redrawing.):
🔗Personal-Album-54-Image-49732[linkphoto]Personal-Album-54-Image-49732[/linkphoto][/link]
Cheers
Grahami
The map is the territory - especially in chain scale.