SpudFiles

Right hi guys,

I'm currently doing physics, maths and chemistry at a-level so i have a fairly good idea about the physical side of things, but on the subject of "spud cannons" i am a noob.

Firstly need to say thanks to Peter Hoare for getting me interested in this whole "spud cannon" idea.

My plan is to create a fairly simple pneumatic cannon using 22mm copper pipe and 3/4" compression fittings. A QEV would be nice, but i've also heard something about sprinkler valves being quite good too? It will be based on something similar to that which the aforementioned Peter Hoare built




The main difference would be having a blowgun valve as pilot trigger, and having interchangeable barrels (using compression fittings) for a variety of projectiles.


I'm just looking for any comments you vet's can make. In the future i would like to produce a double barrel shotgun style cannon.

welcome to spufiles!

I reccomend ditching the dodgy chamber shape and going for something slightly sleeker like Hotwired's Copperhead prime:
http://www.spudfiles.com/forums/copperh ... t6013.html

or Rag's HEAL

http://www.spudfiles.com/forums/heal-32 ... 11453.html

at least as far as the chamber layout goes, the fancy grips etc. are optional extras

or alternatively BtB's Sawn-off layout is decent too

http://www.spudfiles.com/forums/sawed-o ... t1342.html

then for a valve, you can't beat a 3/4" QEV for a 22mm barrel, although i would recommend using a chamber size one up from the barrel, so a 28mm chamber for a 22mm barrel, this allows decent volumes whilst still maintaining a sleek design and good flow characteristics.

Also are you UK based? because i can point you in the right direction of some QEV and fittings suppliers.

That's a lot of sweating you've done there..

This is a decent first cannon and presentation here at Spudfiles. Plan to spend a lot of time searching through the cannon showcases to see how similar designs were constructed. Yes, a sprinkler valve is readily available and can be utilized with surprising power. A sprinkler cannon would be the next natural progression in your cannon building. You could even replace the ball valve you have on this gun with one.

In any case, nice work and welcome to Spudfiles!

starman wrote:That's a lot of sweating you've done there..

This is a decent first cannon and presentation here at Spudfiles.

That's not his launcher, but what he'd like to build

Eeek, looks like you're right, JSR. I thought the first one was his and the second one was the other guy's.

Sorry for the faux credit given there Night Hawk. Now come up with one even better!

Aye im uk based, i was planning on changing the chamber layout too. Pete pointed me to Partridges for plumbing fittings and such, and for piping i will go to the local b&q. Im near sheffield if it helps?

Starman:- i plan to . Im just getting ideas and such together at the moment, exams and all are starting to pump up the pressure (geddit?).

I assume if you know pete then you will get your QEV and bits off him?

but B&Q should have what you are looking for, but i find that these guys have practically everything pipe and fitting wise, the prices are good and the postage is only £4 unless you buy their whole catalogue


http://www.bes.co.uk/

you should get a better price if you buy all the fittings from there (but remember the postage)

I might source the QEV from Pete or wherever he recommends. What is the view on having flexible pipes going from the QEV to the chamber?

I also very much like the copperhead.

Night Hawk wrote:What is the view on having flexible pipes going from the QEV to the chamber?

As long as everything's pressure rated, why not? Make sure it's at least as wide as your barrel though so as not to restrict flow and therefore performance.

I presume thats the golden rule with most things then? If its wider than the barell then its good?

Basically, consider this - it's no use having a massive valve if the connection between valve and chamber is a tiny hose, it's a chain-is-only-as-strong-as-its-weakest-link situation

I assume that you means you spoke to pete but met him through his site?
The type of cannon you build depends on what you want from it. If you're going for sheer power, do a design like pete's. If you want something that's good fun to shoot, go for something a little more like Hotwired's or Ragnorak's.
I've built both types of cannon, and while the sheer power is interesting, it isn't as fun as using something you can hold and aim.
All these guys are from the UK, and you might find it a little easier getting first time help specific to the UK from www.UKSGC.co.uk. There are a couple of memebers there who don't post here, and vice versa.

Sprinkler valves are rare and expensive in the UK, so you'll probably want to forget about them for the time being, but if you look http://www.uksgc.co.uk/forums/index.php?showforum=6 then there is a lot of information on the cheapest suppliers.

Yeah i know that site very well . And i met Pete though Alex. Umm well i suppose i will go for a rifle design of some kind.

Hey about the hose thing, if i ahve 4hoses each have a diameter of 5mm and my barrel is 2cm is that a strong restriction of flow or is it nearly as good as a 2cm hose?

john bunsenburner wrote:Hey about the hose thing, if i ahve 4hoses each have a diameter of 5mm and my barrel is 2cm is that a strong restriction of flow or is it nearly as good as a 2cm hose?

no, cross sectional is what you need to look at.
4*.25*.25*3.14=0.785 cm2
1*1*1*3.14=3.14cm2

only 1/4th as much flow than if you used 20mm pipe

of course, you could use 16 hoses...