SpudFiles

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?

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.

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?

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

"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.

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

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.

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.

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

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.

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

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