The Alldays and Onions 300-pound air hammer sits outside on its concrete pad wrapped in tarps — in "Christo Tribute" mode as my wife cleverly observed — waiting for better weather.
This side of the valve shows the flap valve which consists of a thin piece of springy steel held in place with two bolts and a much heavier, bowed spring. The thin steel sheet works as a one-way valve, lifting off of the ports it covers when pressure is greater on one side but slapping tightly shut when pressure is greater on the other side.
It appears that there is supposed to be two such flap valves and that one is missing. There are two open ports, similar to those covered by the existing flapper, threaded holes for the retaining bolts and some wear marks indicating that there was once a second valve in place. Figuring this out will have to wait for spring when I can examine the airways in the hammer carefully.
This is the other side of the valve — 180 degrees around from the previous image — and shows the other side of the valve ports. The valve body weighs around 90 pounds and fits very nicely into a sleeve insert in the hammer body. Just a little surface rust made it difficult to remove. Its own weight is enough to cause it to bind in the sleeve when half way out unless it's supported carefully.
It appears that someone had difficulty removing it at one time and attempted to solve the problem by inserting a bar into one of the ports in the valve body for leverage. There is a crack in the casting and a slight displacement of the web between two ports.
UPDATE: The Acadia engine needs a replacement magneto or some serious work on the existing one. And I haven't figured out how to mount a clutch pulley on it in a tidy fashion yet. Couldn't wait to find out if this thing works so we rigged up a friction-drive power source.