Do I have to use a PVC adapter?

[ThatGuy]

In a piston cannon I am working on I am using 1" pipe as a barrel but want to have the last 6-8 Inches be 1 1/4" Pipe to allow larger projectiles.

Do I really need an adapter? 1 1/4" and 1" PVC pipes fit really well together.
and the 1 1/4" will fit through a 2" to 1 1/4" adapter that has been sanded so it can extend 3-4 more inches out of the chamber.

My thought is if I have the pipes overlap for 2 inches and put as much PVC cement as I can it should be OK. Has anyone done this before or would it be discouraged?

[Gun Freak]

In my experience with the fit of 1-1/4" and 1" PVC, it is definitely not snug enough to solvent weld. You can epoxy them if you are good with epoxy.

Also I hope you know you need a coupling to use a bushing like that.

[ThatGuy]

is it OK to sand off an adapter coupling just enough so the pipe extends through it?

Ya sorry that was a quick sketch- I haven't gotten all the parts together yet and was deciding if I should have the 1 1/4" barrel inside the chamber or outside as a barrel attachment.

Should I make the barrel diameter change inside the chamber or just have the 1" barrel extend outside the chamber and attach the 1 1/4" barrel there?

[Lockednloaded]

Why not just have the seat be the 1-1/4" pipe and have a removable 1" pipe insert?

[Gun Freak]

"Adapter coupling"... do you mean bell reducer? NO. Not unless you are certain it is pressure rated, which it probably isn't.

Should I make the barrel diameter change inside the chamber or just have the 1" barrel extend outside the chamber and attach the 1 1/4" barrel there?

That sounds like a better idea.

But are you going to leave the larger projectiles at the end of the smaller barrel? That doesn't sound right. There will be way to much dead space.

[ThatGuy]

is having a 1 1/4 barrel inside a 2" chamber going to give me enough power? Because I will just use 1 1/4". I just thought 1" would give me much more volume.
Another reason is I am venting with a blowgun and was going for the smaller piston- but I am told a 1.5" piston should work with a blowgun.


And I am confused about the adapters- which one is a no-no?

needs coupler

does not



Thanks for the info

[Gun Freak]

The one that does not need a coupling is generally a no-no. Plus, bushings looks better and reducers looks stupid, IMO.

Um, 1-1/4" fittings fit in 2" pipe, which means if you use a 1-1/4" barrel then you'll only have a fitting's-width of volume which is not nearly enough.

[ThatGuy]

That is what I thought- this is my first piston cannon and with a 1" barrel I have all the parts figured out.
Thanks for the help.

Only 1 more question- like I said before would it be safe to sand off that part of the bushing that prevents the pipe from being pushed all the way through? I want the barrel to extend out the end.

[Gun Freak]

Yes, that is how everyone does it. If you have a dremel with a sanding drum, that is the best way.

[Proxywars]

If you have any problems on your first gun and you don't have machining equipment you might want to get the taste of pneumatics by making something like wat I made with $10 =). Shoots batteries like a beast and the kick is nice too. Do whatever you want i'm not trying to make you throw ur plan away.

[ThatGuy]

Thanks for all the help!

I have had experience with pneumatic cannons but not with pistons. I will definitely make a battery launcher though- I have at least 40 dead AAs

[Proxywars]

Haha ya just make sure you dispose of them once the get bigger in the center or you will have dead grass.