My first spud gun (and problems)
Posted: Mon May 12, 2008 5:55 pm
I just discovered this place a couple of days ago, and I am amazed at the amount of new technology that has become available though this forum, especially the wealth of information about piston valves.
Naturally I set out right away to construct a small prototype coaxial launcher. Failing to find any pressure rated PVC in the shops around here I decided to go with what I had in my junk box, so I made this fairly run of the mill coax using a cast epoxy piston with a piece of bike tire for the seal. The chamber is from a desoldering sucker, the copper pipe is 1cm (3/8") inner diameter and the "end caps / bushings" are made from 5mm acrylic I cut to shape and glued in place with a generous amount of epoxy. I don't expect this to hold a lot of pressure, but it's just a prototype after all.
Trouble is: Even though nothing is leaking, and the piston definitely gives a good seal, nothing happens when I pump up the chamber and then trigger the valve. The pilot volume empties with a small whoosh of air, but nothing comes out the front. I am wondering if either the main chamber is not filled up at all (piston forming too tight a seal), or if all the air from the chamber exits through the pilot valve (piston too loose).
The fit seems about right, the piston moves easily and if I blow hard with my mouth I can get a little air past it. I guess I could just mold a few more pistons, since it's easy enough, but maybe I am just overlooking something very simple since I am new to this?
Any help would be appreciated!
Naturally I set out right away to construct a small prototype coaxial launcher. Failing to find any pressure rated PVC in the shops around here I decided to go with what I had in my junk box, so I made this fairly run of the mill coax using a cast epoxy piston with a piece of bike tire for the seal. The chamber is from a desoldering sucker, the copper pipe is 1cm (3/8") inner diameter and the "end caps / bushings" are made from 5mm acrylic I cut to shape and glued in place with a generous amount of epoxy. I don't expect this to hold a lot of pressure, but it's just a prototype after all.
Trouble is: Even though nothing is leaking, and the piston definitely gives a good seal, nothing happens when I pump up the chamber and then trigger the valve. The pilot volume empties with a small whoosh of air, but nothing comes out the front. I am wondering if either the main chamber is not filled up at all (piston forming too tight a seal), or if all the air from the chamber exits through the pilot valve (piston too loose).
The fit seems about right, the piston moves easily and if I blow hard with my mouth I can get a little air past it. I guess I could just mold a few more pistons, since it's easy enough, but maybe I am just overlooking something very simple since I am new to this?
Any help would be appreciated!