2" Coax Pilot Options? Updated

[Technician1002]

You may wish to use something to keep the barrel centered. On the mouse musket, I used some poly tubing. I cut three pieces about 2 inches long. I put holes cross way through the center of each and threaded a zip tie through them and secured them to the barrel about 6 inches from the end.

The 3 tubes squished down slightly as it was placed in the chamber keeping it centered. The very long taper on the barrel is not needed. You need just enough bevel to let the piston seal to lift as the pressure in the pilot is reduced. As the pressure reduces, the contact area reduces to just the rim at the barrel ID. The narrow end remaining on your barrel could have some issues with higher pressure and the piston seal.

Good luck.

[Gun Freak]

Yeah about the long taper, you could cut the barrel and chamber a bit shorter to make the taper a bit stronger. And as Tech said, barrel supports are definitely needed. If you look around the showcase there are some creative ways to do it.

I have an idea for you, just a thought. If you use schedule 80 pvc then you can buy 1.5" bushings and glue them directly into the pipe. The fit is perfect. This would eliminate the need for nasty couplings on the ends.

[tony48]

Ok I will redo The taper on the barrel seat. How thin should I make the pipe wall at the seat? And I was planning on a barrel support but not sure about what to use yet. This is not a big deal though because I can easily turn one on the lathe or whip something up fairly easily

[Technician1002]

Leave the barrel full diameter. Round the edges some with sandpaper so when the pilot pressure is vented the piston rests lighter on the barrel and the outside forms a gap. Then the effective piston seat is near the barrel ID. Leaving it thick will prevent it from cutting into the seal very deeply.

If you look at the valve seat on the Mouse Musket, even though the seat seal is the o ring, the barrel end and reducer is there to support the piston when the force on the seat is high.

[tony48]

I rounded the edges but I did take some off the lip so that the wall is about 2/3 as thick as it originally was. I think it will be ok and I'll test it like this

[jackssmirkingrevenge]

The tapering was not necessary, all you needed was a piston face the same size as the piston O/D and it would have worked anyway.

[tony48]

The tapering was not necessary, all you needed was a piston face the same size as the piston O/D and it would have worked anyway.

Will you explain this a little more please? I'm not quite sure what you mean.

[jackssmirkingrevenge]

A common misconception is that the piston has to have larger diameter than the seat, or have part of its face exposed in order to function well.

This is irrelevant, what is important is the difference between piston external diameter and barrel internal diameter.

The instant you pilot the valve, the force holding the piston shut is removed, and air is free to enter the resultant gap between breech and piston face, thereby forcing the piston open. It's a good idea to chamber the edge of the breech end of the barrel to smooth passage of air and prevent it cutting into the sealing face, but it terms of function it will work regardless.

[tony48]

Ok thank you very much. I will keep this in mind as I do the final touches on the valve seat. Thank you very much to everyone that has contributed so far to this project and my thread on my 3" piston valve. I have learned a ton and have started my addiction I should also have some nice cannons to post in the pneumatic cannon section soon

[tony48]

I worked on the cannon a bit more today and it led to another question. I have alot of pilot area in the 1" pipe. So I'm wondering if I can fill up this extra volume with a custom turned piece of wood with a small hole drilled through the center. It would essentially be shaped like a tube with very thick walls. Would it still be able to pilot if the hole through this piece of wood was only about 3/8"? This would make it much smaller than the piston which is ~1". Any ideas? I will have pics up later tonight.

[Gun Freak]

That would work but is there any chance you could make it out of plastic stock instead of wood, that would last longer. Make sure the hole through the spacer is larger than that of your pilot valve and there shouldn't be any restriction.

[clemsonguy1125]

That would work, but like Gun Freak said plastic might be better, if you have HDPE I think that would work great. Its what tech uses for his QDV pistons I think.

[tony48]

ok here it is so far. I'm going to drill and tap the back threaded plug so it will go to a modified blowgun that will be the pilot valve and the fill valve. You can see the round spacer which basically looks like a dowell with a hole drilled in the middle. The whole is currently 5/16 but can be drilled larger. and I have foam that will also go in the 1" pipe to cushion the piston, it will not just be slamming into the wood.



And just for kicks...my finished piston


So what do you think? Will this work alright with a modified blowgun? It just seems weird that the pilot volume is all going through this small tube.

[clemsonguy1125]

That should work with a good bumper, It also looks like it would be easy to replace. If it were me I would fill it with rubber stoppers with a hole drilled through them, they would serve as a bumper.

[tony48]

Thank you, that is a good idea