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I need HELP!

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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I need HELP!

Unread postAuthor: Sevenhawke » Sun Sep 26, 2010 6:42 pm

After reading over some of the posts on this site I am convinced this is the place to go. Here's the situation. I have a charity haunted house coming up at the end of October and they want something along the lines of a LOUD spud cannon. There will be no projectile involved (until later :lol:). It will have to run off of a compressor and lastly I need to try and make it automaticly go off at intervals. I am very handy as far as building things but I am out of my element when it comes to this. Any help (especially drawings) you guys can give me would be greatly appreciated. Last year because of this function we were able to feed 200 local families on Thanksgiving. Thanks again
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Unread postAuthor: saefroch » Sun Sep 26, 2010 6:55 pm

You're looking for a high pressure, high-efficiency piston valve without any significant barrel. I'd suggest steering away from PVC and just opting for a steel construction. Two solenoids on a timing circuit, such that one opens to fill, shuts, then the other opens and either pilots a sprinkler valve pilot or just directly pilots the piston valve. Pilot shuts, fill opens, and you're resetting for another BOOM.

Piston Valves Explained. Start your education there, pick a basic design, and we can help you once you've got more of an idea.

Do you have any size limitations?
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Unread postAuthor: POLAND_SPUD » Sun Sep 26, 2010 7:01 pm

No need to use two solenoid valves. Use a QEV (or a homemade piston valve) and a 3 way solenoid valve
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Unread postAuthor: Gun Freak » Sun Sep 26, 2010 7:09 pm

Put a tee on the end of the barrel with a hole in it. I know you won't be shooting anything but that is what makes the noise.
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Unread postAuthor: saefroch » Sun Sep 26, 2010 7:09 pm

I stand thus corrected. If you didn't HAVE to use the compressor I'd suggest a combustion since they're far scarier, but a pneumatic is capable of the same boom.
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Unread postAuthor: jackssmirkingrevenge » Sun Sep 26, 2010 11:26 pm

A large solenoid valve or home made piston valve will fit the bill, if you want to avoid electronics and the regular intervals you require aren't too long you could probably use a pop-off pilot.
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Unread postAuthor: Technician1002 » Sun Sep 26, 2010 11:44 pm

Rate of use (cycle time) will be an issue with the normal rate your visitor will travel the exhibit. Plan on using a smallish chamber. Instead of a loud report, most places simply use a solonoid valve feeding a 1/8th inch pipe, or simply have someone with an air hose with a blowgun on it. The sudden hiss is startling at close range.

With a loud report, you have to consern yourself with possible projectiles and OSHA sound levels. You want your attraction to be both fun and safe.

At high speed, even the noise of a popping balloon is plenty loud at close range. Loud sudden noise is possible at low pressure.

For a sudden bang, a simple slap stick works great. It consists of a hinge and two pieces of wood. They are simply clapped together. Loud, sudden, and effective.
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Unread postAuthor: Insomniac » Mon Sep 27, 2010 2:11 am

Yes, this really seems like an impractical and unsafe way to make a startling noise. Unless what you're looking for is a very loud bang from some distance away, I think there are better solutions than a pneumatic spudgun.
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Unread postAuthor: Crna Legija » Mon Sep 27, 2010 7:50 am

how long apart do you want the bangs, you could use one of these if you a solenoid to pilot a valve, it has 3 setting the longest is 36 min witch would probably be to frequent
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Unread postAuthor: Ragnarok » Mon Sep 27, 2010 7:59 am

Tech1002 is completely right.
The problem is, discharging piston valves indoors is a BIG no-no. These things can reach literally deafening noise levels even without echoes and contained pressure (i.e. when they're outdoors).

There is a world of difference between scaring someone and permanently deafening them. If you need a sharp, scary noise indoors, you can do it far more safely and efficiently than a spudgun.

But aside from help, the other thing you need is a different thread title. "I need HELP" is against forum rules on the basis that it's not descriptive.
For an example, "Help with Noisemaker" would however be acceptable.
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Unread postAuthor: Sevenhawke » Mon Sep 27, 2010 1:00 pm

Thanks for the input so far guys. I should be more clear on the venue though. This event is being held in a cornfield maze so you can understand my needing it to be loud and also why I don't want to use combustion. It will not be relatively close to the path. I would never risk injury to anyone.
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Unread postAuthor: POLAND_SPUD » Mon Sep 27, 2010 1:13 pm

Then get a QEV and a 3 way solenoid valve. A time relay or a 555 timer can be used to switch the valve on and off in a loop

ohh here is a video I made.
[youtube]http://www.youtube.com/watch?v=6cErmwrg6LI[/youtube]


[youtube]http://www.youtube.com/watch?v=wHDmZYGSjjo[/youtube]
And here I hooked it up to a solenoid valve that alternatively fills and pilots a QEV gun. Of course it doesn't have to work that fast - as you can see the relay I am using is adjustable (and most of them are adjsutable).

First check what is a relay, how they work and what types of them exist. Then check what kind of relay you need (one that switches on and off in a loop).

I know that the one I have is rather large but that's because it is old. What is more, the guts of them are usually quite small - the casing is that large because it is standardized to fit the DIN rail


Though, don't forget that relays are also used on cars
looky here ->
http://cgi.ebay.com/ebaymotors/2-Pin-Un ... ccessories

This one is probably non-adjustable (AFAIK there is a set rate at which indicators flash and it shouldn't be changed), but I've seen adjustable relays that are just as compact
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Unread postAuthor: Sevenhawke » Mon Sep 27, 2010 1:45 pm

Thanks for the reply POLAND_SPUD. I like the idea of using a relay to open and close the valve. What are you using to power it? Also what is a QEV? I'm looking at about 3-5 minute intervals for each shot. About enough time to have one group leave an area and another to come by.
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Unread postAuthor: Ragnarok » Mon Sep 27, 2010 2:01 pm

Sevenhawke wrote:I should be more clear on the venue though.

It helps, yes. When you've said "haunted house", the natural assumption is that it would be indoors.

~~~~~

Even with the concerns about indoors removed, you should still consider the decibel levels involved, even if it is a way from the path.
Personally, my recommendation would be to have it fairly near, but a relatively low dB level.

The reasoning here is that while it will sound just as loud where its meant to, the sound levels will drop off better with distance.

For example, if the device is 120 dB @ 1m, and 10 metres from the path, it will sound to be 100 db at the path, but 80 dB 100 metres away (excluding sounds being absorbed, and just calculating the fall off with distance).
However, if 110 dB @ 1m, and 3 metres from the path, it will still sound to be about 100 db to the intended listener, but only 70 dB at 100 metres off.

I'm just using arbitrary figures there for the sake of a calculation, but it should get across the main point - if quieter, but closer, it will sound the same to the intended listener, but will be less likely to give itself away in advance (spoiling the surprise). Add in some extra fall off for the corn absorbing the sound, and you could have a pretty healthy ratio between what the intended listener and anyone else would hear.

On a similar note, what would be better than just a timer would be a system that was triggered only when someone was in the right place.

Be it by "laser tripwire" or whatever, this would mean it would be best posed to surprise the right person, as opposed to it just firing at potentially irrelevant times (and again, risking ruining the surprise).
You'd probably still want a timer involved to stop the tripwire setting it off too regularly, but it's all fairly simple electronics.

~~~~~

Alternatively, although perhaps not in quite the right theme for this, what could be interesting is some trigger plate in the ground that loudly goes "clunk" when stepped on, then sets off a particularly loud noisemaker a few feet away (either as they step off it again, or after a second or two).
That would probably require things that were in the region of "too loud" though, even if it would be really effective.

After all, the trick to getting people scared is making them forget that it's fake - a good show with something like that would really break their scepticism.
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Unread postAuthor: POLAND_SPUD » Tue Sep 28, 2010 1:49 am

Thanks for the reply POLAND_SPUD. I like the idea of using a relay to open and close the valve. What are you using to power it?
there are relays that work on AC only, DC only and ones that accept both AC or DC
the one I used can run on DC and AC

here are a few links
http://www.magnecraft.com/library/secti ... Series.pdf (this one is pretty cool as it is a universal relay - you can choose between 10 different functions - among them the one you need)
http://www.allaboutcircuits.com/vol_4/chpt_5/3.html

I'm looking at about 3-5 minute intervals for each shot.

That shouldn't be a problem. Most relays allow to choose from less than 1 second to 60 minutes (some up to 60 days ;-) ). What is more, some have two knobs/potentiometers so you can adjust not one delay but two (so both the length of the signal and the delay between them, which makes sense for you as you have to energise the coil for just less than a second to fire a gun... no need to keep it in energised state for 10 minutes)

You can find relays on ebay and that's probably the best source as they are fairly cheap there. Though no one said that you can't buy them locally so give it a try too. But for a start make sure you know exactly what you need.

QEV stands for quick exhaust valve - it's a ready made piston valve
you can find some info on piston valves here:
http://www.spudfiles.com/forums/piston- ... t8157.html
ans see a pic of a QEV here:
http://www.spudfiles.com/forums/viewtop ... tml#299891




You'd probably still want a timer involved to stop the tripwire setting it off too regularly, but it's all fairly simple electronics.
Again it's a job fro a time relay. Sure you can build a 555timer but since you need to attach it to a relay anyway (as the 555 timer can't switch high currents itself) and build the thing yourself, put it in some project box or something then you might as well choose the simpler option and get a timer relay.

uhmm enough spoonfeeding you've got more info than you need in all those links :wink:
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