Props M41 (SPNKR) T-shirt/Air Cannon

[Benton188]

Hey everyone. So Obi_Jeff_Kenobi came up with this crazy idea of building a SPNKR rocket launcher and designing it to also function as a T-shirt cannon for conventions. Truthfully, I thought he was insane for such an idea, but here we are later and I'm going to attempt to build the darn thing lol. Obi_jeff is working on his own schematics for the one he wants to build, but I've went ahead and picked up almost all the parts for mine:

There are maybe 1 or 2 pieces I have to wait for in the mail, but I plan on getting most of the assembly for the main and reserve tanks done while I wait. Here's to hoping this actually works and doesn't, literally, blow up in my face =)

 

[Chernobyl]

I'd be wary of creating functioning props designed to actually eject things at conventions - there are a lot of rules set up specifically to avoid people from bringing in any props that have the potential to cause injury, and I don't find it particularly likely that you'll be allowed to fire that weapon at a crowd. In principle, however, it sounds to be an interesting build, and I'd like at least to see what you come up with.

 

[peterthethinker]

just a heads up.
technicality the law most lands would define PVC air tanks as a pressure vessel and it needs to be burst tested .
ASME has some guidelines for the boiler and pressure code

Here is a OSHA guide on air systems.
http://orosha.org/pdf/pubs/fact_sheets/fs44.pdf
that's the legal mumbo/

they allow wrapped PVC ....... thats easy!

from a standpoint of overbuilt is better in most cases here is a idea to reduce the risk ..
Hoop wrap the tank. ..... take fiberglass strips and hoop wrap and bias and radial wrap the thing . ( the barrel is not a issue just the accumulators.)



I am gonna guess you are gonna run 120 PSI.....
a SCBA tank with about a 1/4 inch wrap can take 4500.
You are never gonna get a perfect wrap as a machine can for HP air tanks but at the very least you have added 2X the pressure rating.
That few layers of glass will go a long way in De fragging the pipe.

http://www.engineeringtoolbox.com/pvc-cpvc-pipes-pressures-d_796.html
If you can build it to a 800-1200 PSI spec then its" goof proof ".


Have fun with the air canon !

Peter

 

[Benton188]

I'd be wary of creating functioning props designed to actually eject things at conventions - there are a lot of rules set up specifically to avoid people from bringing in any props that have the potential to cause injury, and I don't find it particularly likely that you'll be allowed to fire that weapon at a crowd. In principle, however, it sounds to be an interesting build, and I'd like at least to see what you come up with.

I've definitely thought about this before I started building it. I know of a lot of conventions that don't even allow Nerf guns on site even if they are unloaded and with no clip. I would only take this prop to locations where I would be permitted to either carry it unloaded, or with permission of use from the convention staff itself. I'm hoping that the fact of having to manually fill it with air, and therefore not be able to fire without the chamber filled would be enough for me to just free carry it around conventions, but that's all on their call. And I've built it to solely run on air pressure as opposed to everyone else telling me to use Co2, which I told them it would definitely NOT be allowed on convention grounds.

just a heads up.
technicality the law most lands would define PVC air tanks as a pressure vessel and it needs to be burst tested .
ASME has some guidelines for the boiler and pressure code

I am gonna guess you are gonna run 120 PSI.....
a SCBA tank with about a 1/4 inch wrap can take 4500.
You are never gonna get a perfect wrap as a machine can for HP air tanks but at the very least you have added 2X the pressure rating.
That few layers of glass will go a long way in De fragging the pipe.

Thanks for the link. I'll have to read up on it, but I was able to find someone who has already built a similar air cannon on Instructibles. The max PSI I'm going to dump into this thing will only be about 40-60psi. 3" diameter Sch. 40 PVC is rated for upwards of 210PSI, the tubing I'm using has the same rating, and the sprinkler flow valve has upwards to 300. I really made sure I did my research before heading into this venture lol.

 

[peterthethinker]

Sweet!
Yea 60 lbs is a ton less of a issue at 3 inch.

Peter..

 

[hacxor]

Make sure you lightly sand, and use both primer and glue. All PVC glue is not the same. Some are rated a lot higher than others. Just my 2 cents. But you are right, I don't think you need to go any higher than 60psi to shoot a t-shirt.

But I'm looking forward to seeing this thing built. I think it is a great idea. Good luck!


Sent from my iPhone using Tapatalk

 

[eiros]

i had thought about this exact idea ages ago lol, or a potato gun

 

[Benton188]

I'm still awaiting the sprinkler valve to be delivered to my local Home Depot. In the meantime, I've gotten the frame, front handle, reserve tube, main tube, and launch barrels completed.

 

[Benton188]

Part came in about 4 days ago, since then I've been really cranking out this project to get it done in time for this weekend. Here is a pic of the inner workings of the cannon and all the wiring involved. I added a kill switch so no-one can pull the trigger accidentally and have it fire. Most it does with an empty chamber is a loud thump and a puff of air no greater than one of those hand air blasters you see at county fairs. Eventually I plan on replacing the kill switch for a key switch for even more added security, but for now this will do. Just a few more pieces to add, another coat of paint, and she'll be ready to go. Oh, and I'll be sure to put a video up of test firing it =)

 

[Benton188]

She's all built =) I may change the paint scheme later on to better match game accuracy, but for now it'll do. I'm still experimenting with the correct amount of psi and placement of the t-shirt inside the barrel to get maximum distance. I will still post a video soon showing a demonstration of how it all works. Stay tuned =)

 

[Benton188]

No major update this time. I've been working double shift duty at work so I haven't gotten a chance to make a demo video yet =/ However, in the meantime I've been looking into picking up a mini air compressor like so: http://www.harborfreight.com/12-volt-250-psi-compact-air-compressor-4077.html
It's small enough to easily fit inside the main housing along side the sprinkler valve, and weighs virtually nothing. Plus it's super cheap so if it breaks I won't feel bad about it lol. I'm currently trying to figure out if I can run the compressor off of an 8 AA battery configuration. The voltage is there, but I'm not sure if the 200ma is enough to power this thing or not. If anyone has any knowledge on how to adapt what would normally be powered by a car battery to be powered by smaller batteries, please let me know.

 

[Redshirt]

No major update this time. I've been working double shift duty at work so I haven't gotten a chance to make a demo video yet =/ However, in the meantime I've been looking into picking up a mini air compressor like so: http://www.harborfreight.com/12-volt-250-psi-compact-air-compressor-4077.html
It's small enough to easily fit inside the main housing along side the sprinkler valve, and weighs virtually nothing. Plus it's super cheap so if it breaks I won't feel bad about it lol. I'm currently trying to figure out if I can run the compressor off of an 8 AA battery configuration. The voltage is there, but I'm not sure if the 200ma is enough to power this thing or not. If anyone has any knowledge on how to adapt what would normally be powered by a car battery to be powered by smaller batteries, please let me know.

It will be LOUD! Especially mounted next to your head. I doubt that AA batteries will handle the draw. I downloaded the instruction manual and unfortunately they did not give an amp rating. Look at the wires running from the cigarette lighter to the compressor. The Chinese wouldn't put on any heavier gauge wire than necessary. That wire is good for 30 amps. You might want to consider building a backpack with a small motorcycle battery and the compressor (packed in sound deadening insulation) mounted there with a detachable hose running to the launcher.

An alternative direction is to build it to take 40 mm airsoft shells and use those to fire the T-Shirts (or rockets). My grenade launcher fires the small nerf rockets about 120 feet.

Redshirt

 

[Benton188]

While on lunch today I crunched the numbers.....and they weren't pretty. A string of 8 AA batteries inter linked in series produces 12V....but only 200mah (.2amps/hr). The compact compressor normally runs off a 12V car port which draws in 15amps just on start up! In short, the batteries would be drained in less than a second. I looked into other batteries such as a mini 12V 10amp battery, which they do come very cheap, but weigh about 6-8 pounds. This launcher is already quite heavy enough without the extra weight of the battery and then the compressor on top of that. So I'm foregoing the whole compressor idea and getting back to the basics of man power. The little hand bike tire pump I have right now is just a cheap one from Dick's, so I'm going to shop around for a floor pump instead. They may not be as small and portable, but they crank out a lot more air pressure faster than a hand pump can do.

 

[Redshirt]

You can work the hand pump into the front grip of the SPNKR to make it work like a Super Soaker. Still, find an airsoft shop locally or a serious player to look at using the grenade shells to power this. You may find this as an easier solution.

Redshirt

 

[hopkins77]

Hello everyone, I am very new to all of you veterans, but I might be able to help with the air issue. Have you considered using a hp paintball tank for the air supply? You can usually find a 68/4500 for 50 or 60 dollars on ebay. The best regulator for your application (in my opinion) would be the one kobalt made a few years back. The item number is166441. It screws right to the top of a co2 or hp tank, and will regulate the output pressure from 0 to 150 psi. When I bought mine it was like 90 dollars but you can find them now for 60. Just a thought. By the way, sweet launcher!!

 

[Benton188]

Demo Video is up: