Unown mill engine

As above i was gifted this engine some years ago and asked on MECH and really got nowhere.

The engine is all brass ecept for the fastners which are steel and the flywheel alone weighs 4 to 5 pound and the eccentrics are pressed out wit very sharo corners

Not going out because all of the snow i got it out again and started again with it trying to find out the pitch of the screws before i could not find any thing, but this morning was trying thread gauges again thought about unf and they could be 5 unf i await in tracy tools foe cheap ta[p and die to try so it could be American,

Where i am really stuck and know nothing about it is the valve gear,

It is supposed to have reversing gear i have a eccentric and a plain drive bush? and have ordered some brass for making the eccentric.

To get down to basics does anyone know how the valve gear works and spell it out for me in simple steps for me to make.? Thanks in antisipation Graham

Edited By Graham Titman on 10/03/2023 17:55:17

Looks like you have Stephenson's valve gear. Plenty of examples on google.

There should be two eccentrics and straps side by side on the crankshaft both with rods going back to the expansion link (plate with curved slot) You can see the end fitting for the rod in the upper hole of the link in a slightly different coloured metal possibly bronze,

The long curved leaver will raise and lower the expansion link, when one of the eccentric rods is approx inline with the valve rod it will run in one direction, when the other is lined up it will run the opposite way.

I would also look at small Whitworth threads in you are in the UK

If you look at this video of my traction engine you can see how I move a lever one towards the rear to raise and lower the expansion link and direction changes