Two questions from a new cannon builder

[jared555]

I have been reading on the forums here for some time but just now am truly planning on doing something soon.

I am hoping to build a pneumatic cannon in the near future and had a couple questions.


At what point does firing a cannon indoors (no ammo) become a) A risk to hearing and b) Risking damage to parts of the room you are in. I am not asking about the thing exploding. I am referring to the sudden increase in pressure in the room.


Also, for someone who has no air compressor available what would be recommended for a new compressor? (I do have uses for it other than sending projectiles flying at high speed, so things like a refrigerator compressor are not an option..... yet)


Ok.... it is more than two questions..... What costs are involved if you want to use a high pressure nitrogen or co2 cylinder instead of a compressor? (Tank rental, refills, etc.)


I have a few very nice locations I can use for playing with a cannon. The only thing that would suck is retrieving whatever ammo I was using.

[LCTChamp]

Why would you ever want to shoot a cannon indoors? It usually isn't a hearing risk until you get to really high pressures (Above 175 psi). I don't really understand the second question. There is not enough air in a pneumatic tank to increase the room pressure more than a couple psi if that. Co2 tanks can become quite expensive. You have to get a regulator which can be $100 dollars or more. What size co2 tank are you referring to?

[cheeseboy]

OK, regarding the first question on indoor safety unless you live in a room that's airtight -or close to it- it won't be a problem, the only possible way to damage things when test firing indoors without ammo is the air blowing stuff around and possibly damaging it, this is more pronounced in smaller caliber cannons (anything less than an inch). In answer to the second question on air compressors I can't offer specific models and brands and such as I am guessing that you are an American so things there differ by some, but what I can offer is that you buy a petrol one, besides being portable they are more readily available and can run for longer times without cool down, if you didn't have other reasons for wanting one I would recommend just using a floor pump, I used one when I started and have now adapted it to high pressure, but they are very cheap and as long as you have a pressure gauge as easy (if not easier) to use than a compressor as no power is required and such. for the last question are you talking about scuba tank sized cylinders? well if you are make sure to get a quality regulator like the ones used in paintball as they are sometimes adjustable and can be used from the first plastic ball valve cannon to the QEV piloted copper marble gun which will save you money in the end. in response to the costs, buy a tank, not only does that let you use it more often, it pays for itself, as the rental prices will eventually reach the price of the tank as long as you get it cheap, filling the tank will differ in price depending on weather you fill it your self with a pump, or get it filled to high pressure with a specific gas, if you do, fill it with helium I haven't tried but I will improve performance because it is a lighter gas. and finally for ammo that is the reason for potatoes being so popular, you can leave them on the ground and they will biodegrade, there are many other options for ammo that you don't have to pick up but they vary according to barrel size.

edit: wow I wrote a ***load of stuff better add a smiley :sad5:

[Mateo]

if you mean dry firing the cannon indoors, then i doubt it would hurt anything in the room. you would need some crazy high pressure to break something. but if you load the cannon with something like a bolt, then dont shoot it inside unless you are prepared to patch up a hole in the wall.

[jared555]

Indoors: more low pressure tests than anything (before dragging it out of town for actual use)

And I was referring to the larger size tanks that you can get at a welding supply shop, etc. (I forget the proper size). And on cost of filling - I was asking about the cost of getting it filled at a gas supply shop (welding or otherwise) with helium/nitrogen/co2

[jared555]

if you mean dry firing the cannon indoors, then i doubt it would hurt anything in the room. you would need some crazy high pressure to break something. but if you load the cannon with something like a bolt, then dont shoot it inside unless you are prepared to patch up a hole in the wall.

I could always take the screen out of the window and see how far down the street I could shoot a tennis ball.....

EDIT:
I figured I would add this in.... I am 19 now and have been reading quite a bit about this (along with other things like high voltage, tesla coils, etc.) since I was 12-13 so I DO know the danger involved in many of the projects I am hoping to try in the future.

[iisthemuffin]

Try not to double post. Personally I don't care but it is against the rules. Use the edit button instead.

Even though your trying to help him out, this is almost as annoying as double posting. You tried to correct someone without offering anything useful to the topic.

Anyway. Depending on what you want the compressor for a small oiless compressor will do fine. They dont get very high pressure but they are still very useful. i just got a small one for christmas myself. It has a max pressure of 100 psi. It takes a while to fill up the tank its self but stays full for a long time when it runs. I got mine for 50 dollars at Harbor Freight. It was on sale.

http://www.harborfreight.com/cpi/ctaf/d ... mber=97080

[Pookydarts]

G'day! Welcome to spudfiles! (I'm actually another newbie, this is my first post!)

Part 'B' is the easiest one to answer,
...unless you're thinking of propelling bowling balls for your first project..., I wouldn't worry about pressuring up a room.

Obviously don't expell compressed air at glass, living things, your mum's china cabinet, or priceless crystal chandeliers.

Best thing is build one, start dry firing at low pressures and build up in small increments, you'll soon get a 'feel' for what not to point it at.

(Oh! And don't 'dry fire' combustions at carpet!)

Safety glasses are always a good idea.

As for hearing protection, some of the other members had better advise, i've had some loud combustions, but i'm new to pneumatics and only play around in the small calibre / 60-120psi zone and havn't needed earplugs yet.

In pumps, surprising power can be had from a bike pump, a cheap 12V automotive compressor, or an industrial shed compressor, I worked backwards through this series and was gobsmacked when I saw what the humble bike-pump could achieve.

I built piston valves for my first (and second) pneumatics but my last two guns were (and next ten will be,) sprinkler valve guns! So simple and reliable!

Anyhow, enjoy!

[jared555]

Try not to double post. Personally I don't care but it is against the rules. Use the edit button instead.

Even though your trying to help him out, this is almost as annoying as double posting. You tried to correct someone without offering anything useful to the topic.

Anyway. Depending on what you want the compressor for a small oiless compressor will do fine. They dont get very high pressure but they are still very useful. i just got a small one for christmas myself. It has a max pressure of 100 psi. It takes a while to fill up the tank its self but stays full for a long time when it runs. I got mine for 50 dollars at Harbor Freight. It was on sale.

http://www.harborfreight.com/cpi/ctaf/d ... mber=97080

Thank you. And in response to lctchamp, thanks for letting me know but I did read the rules. It is just instinct to hit reply when I am responding to someone elses response (he responded while I was typing the first reply)

[Gippeto]

So far, I've about $400 in my N2 setup. It will put out 4000psi.

The cost of CO2 setups will vary considerably depending on outlet pressure, and capacity.

If you only need 120psi, a Kobalt style regulator from a building store will serve your needs. They use regular paintball tanks.

Another option for paintball tanks is the Palmers Pursuit "Stabilizer". It's fully adjustable 0-800psi, and will also work with hpa tanks.

http://www.palmer-pursuit.com/online-ca ... ilizer.htm

For a welding supply type bottle, expect to pay $100 or more if you want high pressure output.

Shopping for N2, I found that lease costs of the bottles vary widely depending on whom you phone.

Call around, and get some local quotes.

The P.P. Stabilizer and a hpa tank seem like the best bang for the buck, unless you really want more than 800psi.

[MrCrowley]

1) With a piston valve 1.5" and above, as little as 100psi, they can effect your hearing a fair amount if in a small room.

I dry fire my piston cannon all the time without a barrel (it's noiser without the barrel) in my garage when i'm testing at only 80psi, and the sound is deafening.

If you're in a smaller room with the door close, the sound will also be similar. It will also effect any object with a few meters that isn't fixed to a surface or too heavy.

The part about the increase in pressure is nothing to worry about. Like said above, unless you're in a sealed room, you wont notice a difference. Even if you were in a sealed room with a chamber the size of a welding tank, there'd hardly be a difference at all i'd imagine.

If you're getting a new compressor, i'd recommend at least a 21 litre tank (5 gallon) with a minimum of a 1.5HP motor. I personally have a 2HP compressor and 21 litre tank and it takes a few minutes to get to 115psi.

CO2 and Nitrogen tank costs depend on where you live. In America I imagine it'd be fairly cheap. I know a Canadian member 'DYI' uses nitrogen tanks, I can't recall if he rents or owns the tank but he does get it refilled. He has some big cannons that use a lot of nitrogen and at one stage the cannon was costing him a few dollars in nitrogen per shot in relation to filling cost and possible renting cost.

I think it's about $50USD a year to rent the tank, and then $20 for a refill. That's just what I recall from other members, so it is subject to change.

Just incase you missed the posting rules:
http://www.spudfiles.com/forums/viewtop ... tml#136508

[Gippeto]

Costs vary GREATLY.

My tank cost $69 to lease for a year, $140 for the contents, and another $50 for a well used wheeler to move the thing around.

[DR]

Also, for someone who has no air compressor available what would be recommended for a new compressor?

Who needs a compressor... at all?

<img src="http://i42.tinypic.com/103a4id.jpg">


"Compressor Chamber" is fabricated from 4" SCH40 PVC Pipe. Each 18" length of pipe (approx.) is equal to 1 gallon capacity.

V1 (Valve 1) is a 1/4" Ball Valve. - Attached to it, are any fittings that you may find in your area, to step it up to a 3/4" NPT Male thread... The 3/4" NPT Male thread, is so that you can attach your "Compressor Chamber" to a common garden hose.

Turn the hose bib on and open V1. - As the water level rises inside of the Compressor Chamber, it displaces the air inside. The air pressure will increase, the pressure in your launcher's chamber is equal to the water pressure coming out of your hose bib.

So long as the Compressor Chamber's volume exceeds your launcher's chamber volume, there is no risk of accidently getting water inside your launcher's chamber. - Not that it would ruin anything, regardless.

The pressure coming out of most hose bib's, typically runs between 30-70 psig. - More than adequate for your "low-pressure" tests.

When your finished charging your launcher, V2 (Valve 2) may be opened, to drain the Compressor Chamber... It's entirely up to you, how big to make your Compressor Chamber. - Hypothetically - If your Compressor Chamber volume is a little more than twice your launcher's chamber volume, than you could fill your launcher twice, before emptying the water. +3 times the volume, 3 shots, and so on.

[starman]

Who needs a compressor... at all?

That's a cool alternative to a compressor, but still ties you down to your backyard...my biggest problem with large bore pneumatics.

[jared555]

Thanks for all the information. In response to DR..... how many times larger would the compressor chamber be than the cannon chamber to start to get close to the maximum psi possible?

That also made me think.... what about the drill powered water pumps? Would they a) be useful for pumping water in that situation or b) could they pump air at any kind of pressure? Even just pumping water that would allow multiple reuses of the water rather than just dumping it