[Rick Osgood] has been busy making more scaring gags for Halloween. This week he’s sharing great ideas for an air horn and pneumatic jumping skeleton, both actuated by 24 V sprinkler valves. These two new gags can easily be activated using [Rick’s] cardboard floor plate switch and three 9 V batteries cleverly snapped together in series for a 27 V supply (we can’t resist dropping in this link to a 2196 V supply from 9 V batteries just for fun).
The air horn construction is quite unique using a latex balloon strategically located as a reed valve for the air to vibrate over as it rushes out making a very loud honking sound. [Rick] then connected his manual bicycle pump to an air supply so that when an air valve is actuated the bicycle pump handle with a skeleton wired to it pops up. It then lowers back down via a bleed hole in the air line. Both the air horn and pneumatic pop-up skeleton seem simple to construct and his tests show them functioning perfectly.
Being the air storage chambers are small the re-trigger setup seems too repetitive to be practical for a continuous stream of Trick-Or-Treaters. Perhaps one could hide an air compressor with a long feed line to supply the gags? Plus, using an air compressor would come in handy for other scary blasts of air. Of course you would want to lower the compressor’s output regulator to safe levels so you don’t risk blowing apart your pop-up skeleton rig or any pipes.
Follow along after the break to see how to build these two great gags and get some tips from Mr. Safety.
Mr. Safety advice: Keep the pressure very low in PVC pipes because the pipes can shatter unexpectedly, more so in cold weather or as the pipes age or are exposed to sunlight. We have seen others wrap PVC air chambers in a roll or two of duct tape just in case the chamber fails. DO NOT apply pressure to any glued pipes until they have dried for at least 24 hours, the parts will come apart violently if you apply pressure before fully dry. Finally, when working with pressurized chambers you really have to know the safety limits of the materials you plan on putting under pressure. It is always best to use commercially constructed and welded air tanks with labeled pressure ratings. Metal chambers will be rated for much greater pressures even when constructed from metal threaded pipes. Don’t forget, in the US at least, you can get a cheap air regulator and 125 psi 11 gallon portable air tank at Harbor Freight for your scare gags.
Stop using PVC with compressed air and stop posting hacks that showcase them!
Watch out guys we have a safety nazi on a site about hacking lol.
I’m not against showing the hacks on this site, but when the poster knows the build is unsafe (and anybody who’s a regular on this site probably does know about the issues with PVC pressure ratings) he should add the safety blurb. Part of the hacker spirit is sharing your hard-earned knowledge, and we should be learning from the people who’ve made the mistakes before us.
People like you piss me off. “Oh, let’s not worry about people not knowing enough to avoid maiming themselves! Reading those safety warnings is just too much work for me.”
The “safety nazi” is 100% right. PVC piping is not intended for pressurized air. If you spend a few minutes Googling, you can find plenty of examples of PVC turning into shrapnel with as little as 125 PSI.
stop telling me not to do something without telling my why!
Not only do I agree, I’ll tell you why: pvc pipe is rated for liquid pressure, not gas pressure. Unlike tubing/pipe rated for gas pressure (such as black iron or steel pipe) PVC pipe can and will rupture explosively and suddenly, turning into shrapnel. (Metal pipe deforms and will open a crack). Using PVC for air guns is ignorant and cheap and I too am very frustrated with people perpetuating this….and using those stupid sprinkler valves. ‘Course, once you go all-metal, you get a better gun–I’ve built them typically for around 300 psi.
And as for “Why does the PVC explode under gas pressure instead of liquid pressure?” question: The amount of energy in a pressurized fluid is the integral of the pressure times the change in volume when you compress it. Since liquids are generally incompressible, there’s no change in volume and hence no stored energy.
You’ll shoot your eye out kid!
Is that a trouble light reflector on that noise maker?
PVC Pipe and no warnings on why it has to be Pressure rated SCH / BAR / PSI / KPA and using two part pressure rated PVC WELD. Just asking to be a bomb
A good friend lost 70% of the vision in one eye when a pressuresed PVC pipe exploded and the shrapnel tore up his face. Eight years, four opreations and ongoing battles with work insurance companies prove it’s simply a bad idea to pressurise PVC piping. He also can’t enjoy 3D movies anymore.
Another friend lost 20% of his hearing in one ear and has constant tinnitus after somebody at his work thought it would be ‘funny’ to blow an air horn in his ear when he wasn’t expecting it. These things are the audio equivalent of lasers and same as you should never shine a laser beam in somebody’s eye, you should NEVER blow an air horn in somebody’s ear.
Precautions were taken in this build to limit pressure and therefore horn volume, but I can imagine plenty of people replicating this ‘hack’ on the cheap and not bothering with the safety valves. That would be a bad idea.
I’m not sure if it’s really wise to give little vandals itching to vandalize, extra justification to target your home over someone elses. A bit mean if toddlers end up being a target. A pancake type air compressor from Walmart is going to be safer that PVC, less work, and something that going to be useful all year
It seems like this same mechanism would work for opening a cabinet door (to my cat’s litterbox :) ). I’m thinking about using a pneumatic door-closing cylinder, a sprinkler valve, and a motion detector. Makes sense to me theoretically, but I’m not sure how to connect all the parts together. Any way you can do a posting on this with some detailed instructions and what I need to ask for at the Home Depot? I’d really, really appreciate it!