01/12/2024
Happy New Year everyone! Here’s one of my latest projects. I found a Domino trade stimulator locally and while it was in beautiful condition, the air pump in it was completely shot. The original leather cup washer was cracked and brittle, and soaking it in 3 in 1 oil to restore the leather only dissolved it. Oops. I needed a new cup washer.
Made some posts in coin op Facebook groups, and thanks to a suggestion by Tim Claremont, with a $14 sheet of leather from Michael’s and several experiments later, I finally got a working leather cup washer, made by hand.
The first pic is the original leather washer. It basically rotted away.
Leather is surprisingly difficult to cut with a crappy exacto knife. I first tried cutting disks slightly larger than the diameter I needed so I could have some wiggle room to shape with scissors. While they fit the pump housing snugly, they didn’t have a seal. I figured it was because when the plunger pushed down, the edges of the leather pushed up, making it cone shaped and more aerodynamic, breaking the air seal.
In a last ditched effort to make a cup washer, I watched some videos on leather shaping. They all used some kind of mold and a negative to press the leather down, which I don’t have, but I figured I could at least try to fit it to the internal diameter of the pump.
I made a larger leather disk so the extra leather hung over the edge of the cylinder by a few mm, then I soaked it in water for a few hours to soften it. I packed it into the tube, checked on it a few hours later to see if it was still in place, and left it for another 24 hours. When I got home earlier today, it was fully dry and retained its cup shape.
I cut a hole in the center of the gasket, and found a single rivet and washer just wide enough to fit inside the cup so it keeps it shape. I manually fastened the rivet to the washer and cup and then reassembled the shaft.
My Domino finally works! The cup must be working to catch air as it compresses, so molding to the interior of the tube was the trick. Also my dog Lincoln approves of my handiwork 👌
And before anyone asks, no this Domino is not for sale 😎