Piston Problems

[bamaboy2006]

Right now I am using a cheap 1/2" pvc ball valve because I haven't had time to install my sprinkler valve and it is very powerful. It blew a huge hole in 3/4" plywood from 50' away using 80psi.

I would love to see what this thing will do when I get my sprinkler valve fitted.

[SpudsMcGee]

I assumed using a blowgun was the best way to do it because some of the best guns I've seen used blowguns.

[bamaboy2006]

Well I am not arguing with you because I do not know which is best. I just researched a lot of different guns and the ones that listed the best performance all used sprinkler valves with a blow gun attached.

I have to say that with just the 1/2" ball valve this thing is extremely powerful and very very loud.

The first time I test fired it my girlfriend came running down stairs to make sure I hadn't killed myself.

I am very interested in making a breach loading gun next, but I believe I will do it without a piston since this one has caused my so much trouble.

I appreciate all the help and advise.

[jmeyer1022]

I believe you could but to exhaust your pilot with only a blowgun I believe you need an air-tight O-ring piston with a check valve.
http://www.spudfiles.com/forums/viewtopic.php?t=7933&
This helped me design my new piston a lot, take a look at it if you have any other questions just ask, but make sure you search for the answers also.

[jonnyboy]

Well it does make a difference...FOrexample if its a coax and he has a really big chamber then it might not push the piston agains the barrel hard eanoth...all these kinds of things...

Well the air would hit the piston before filling the rest of the chamber.
Maybe you should have a look here.

[psycix]

The sprinkler will pilot better then a blowgun, so there's nothing wrong with that. For piloting big piston valves with blowguns, your piston needs to fit very tight.
Note that you should mod your sprinkler valve (screw a blowgun in it) to make it open fast.

But back to your piston sealing problem:
At what pressure did you test it? Not all guns seal on low pressures, they need more to press the piston against the barrel.
Could you take a picture of your piston and the pipe it seals against?
And is your piston serviceable?


Oh, and:

Posted: Yesterday at 18:33
Posted: Yesterday at 18:34
Posted: Yesterday at 18:39

If you want to add something to your post, please do not double and triple post like that. Just use the EDIT button in the right-top corner of the post you want to edit.
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[bamaboy2006]

Ok. Sorry.

My piston is serviceable. I will try to take some pictures of it latter and post them.

Well I took it out to my field yesterday to see how far it would shoot and I am pretty impressed with the results.

Shoot it three times:
95psi - 420yrds
90psi - around 405yrds
and 85psi - a little under 400 yrds

My air pressure changed because I had to fill my air tank up at home and every time I pressured the gun it would loose air and it did not have enough pressure to fill it up.

These results are will a pvc ball valve.

[MrCrowley]

Yes, sprinklers do give you better performance, but with piston guns all you need is a blowgun.

You're wrong. Shutup if you don't know what you are talking about.

A blowgun only works well with very small bore cannons, the larger the pilot valve the better. Even if it was a 6" ball valve, it wouldn't hurt performance, only increase it.

Not only are sprinkler valves easier to trigger, they provide far better performance.

Chances are a blowgun wont even work with this cannon. Very hard to trigger 2" piston valves with one, and even if you do the performance will be poor. You shouldn't criticise for a large pilot valve, only for a small one. Bigger is better.

bamaboy2006,
See my PM I sent you. Anymore questions, feel free to ask

I'm looking forward to seeing some pictures and videos, happy my plans were enough to not only inspire you to make a cannon, but enough to make a working one.

[bamaboy2006]

Thanks for all the help and the quick replies. I am currently out of the country on business right now but when I return I will take some pictures and try to get the leaking problem fixed.

It could be the bolt so I will try that first.

I made a 3" slug out of plywood before I left and bolted it together and shot it out of my 2" barrel. This thing completely destroyed 3/4" plywood and made the gun kick like crazy.