Thanks Ginger Nut
.
So this is the little design problem I'm thinking about. If you use a sliding ball as a check valve you need clearance around it to allow water to flow past when the valve is open. But if the valve is horizontally oriented, the weight of the ball tends to make it rest on the bottom of the large bore, off center.
To close, the ball moves to the valve seat end of the bore. The valve seat is a small hole, typically concentric with the bore. The ball closes the valve by basically plugging that hole.
But if the ball is off center, that means it must lift when it gets to the seat, since the ball was resting off center with the bore. Will that happen for sure? Seems like how surely it lifts depends on the amount of oversize of the bore, the size and weight of the ball, and how the seat is shaped.
If the seat is concave with a hole in the center, that would help the ball seat. But usually what is recommended for best seating is a convex seat with a hole in the center. I can imagine that if proportions of all these things weren't right, the ball might not lift and seat.
So the question is, how much oversize can the bore be to get good flow through the check valve for a 3/16" ball, when open, yet have the ball lift to the seat properly. And what shape and position should the seat be?
There are other design possibilities than the above:
1.) The sides of the bore could be grooved -- this would allow clearance around the ball for water flow, yet maintain a relatively tight guide clearance for the ball.
Question -- how to groove easily in this size valve (3/16" ball), and how to make a stop for the end opposite to the seat so that the flow can continue around the stop. Ball travel should only be about 1/32" to 1/16" by most accounts.
Possibilities -- maybe groove with a home made single toothed broach -- shaped like a chisel. Maybe use a pin as a stop in a cross drilled hole.
2.) The ball could be supported by a cage in a much larger overall bore to give clearance, but the ID of the cage could be close to the ball size to serve as a guide. Making and attaching a cage this small could be tricky/finicky.
Possibilities -- maybe a cage consisting of two hairpin shaped wires at right angles to each other. Maybe inserted in small holes in the seat and soldered there.
3.) Maybe the seat could have a double taper -- an internal convex cone with hole (volcano shape) and a larger concave cone lead in that lifts/guides the ball to center on the seat. This would require making a special cutter for this shape.
Writing this all out like this, it looks like #3 above would be the simplest. A home made cutter could even form the bore and the special seat in one operation if designed right
Still not sure what the optimum clearance would be for the bore vs ball size, though. I imagine even with such a cutter, it's possible to design a bore too large or too small to work well.
