SpudFiles

I had written a tutorial for casting pistons here, it's for epoxy but some of the principles apply to hot glue as well.

Gun Freak wrote:As soon as i saw your name, I though "Oh god, he's gonna complain about my pilot volume".

I see my reputation preceeds me it's not that I like complaining, but if you're going to bother making a cannon, why reduce the performance potential? In this case, you almost seem to be doing it on purpose! I mean, why do you even need the tee? The schrader can be tapped directly into the pipe. Even if you keep the tee, why the length of pipe on each end, instead of having it touch the chamber and sprinkler valve? There seems to be no practical or aesthetic reason for this.

Still, don't let me lecture you, it's your launcher after all - if you're happy with less performance, go for it

I just cut the pipe so the fittings touch when they are connected.

Here's a picture of my sprinkler valve... how do I get the diaphragm out? I dont want to mess it up. It's an Orbit.

Yep exactly like mine. Just grab the sealing face part and pull it off of the green top of the housing. It takes a little force but it will come out.
I'll post a pic if I can but I'm not sure I have one that I can open still...

Does it go back on easily?

Yes. Do you see how there is a circular rubber groove on the bottom housing piece that the diaphragm protrudes into when you put it on? It's the same on the top. You could also slowly work around the side, pulling it off a little at a time till you get it all the way off.

Ok cool. Thanks. That will make it more safe to drill the hole. Don't want to be drilling into the diaphragm