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Hi everyone, I am part of team 254 for robotics, and we are undergoing a summer project that is building a t-shirt cannon. The toughest part of our research so far is finding a good ($200 and less) solenoid valve for the cannon. We want one with good air flow and response time.
Our plan is to have a revolver/Gatling style cannon similar to this:
It will be mounted on a driving base and be unmanned during operation. We need some benchmark numbers to work with for the solenoid valve specs.
I wouldn't build it with a solenoid if I were you; they are too expensive for their poor performance. If you want to stick with electronics, you should build a piston valve and actuate it with a solenoid 3-way valve
I love lamp
Appalling lack of imagination on the part of the mascot. One would be inclined to level the thing at the assembled cheerleaders, "All of you, locker room, NOW!"
That gatling gun is energy inefficient and depends on high pressure gas expanding as it goes through the valve to provide the volume to eject the shirt at moderate speed. They do not show the poor range in the video, but they have to move it to the sideline to reach into the stands.
I went to their website and found their promo video. They shoot at the 300 section, but watch the video closely at about 40 seconds and again at 1:20. The shirts are falling below the 200 section. You can see them fall in front of the box seats. They are not hitting the 300 section at all.
For the speed that valve cycles, I would not be surprised if they are using a high speed modulating valve.
A valve such as this one will handle the volume required for the task and is fast enough. Warning, these high speed valves are expensive.
If you use 1 cubic foot of air per shirt launch, the valve can flow 200 cubic feet per minute. Higher gas efficiency can be gained by using a small surge tank and fast diaphraghm valve to provide a higher average pressure on the shirts when launched by providing the volume of air in a higher flow shorter duration blast.
As far as shooting at cheerleaders, for safety, it it very possible the launcher is not adjustable in angle. It is designed to safely lob shirts into the stands and is unable to shoot anyone at close range.
Edit, I just found a good frame showing the way this launches shirts. The shirts are not blown out of the tubes, but are sucked into the barrel with a venturi ring and a high pressure jet of air. See photo of the screen cap from the video below. That cannon works on high pressure air and air jets at the back of the barrel that sucks the shirts from the magazine into the barrel.
They most likely are not using a high speed valve. Instead they are turing on the flow and letting it rip.
Last edited by Technician1002 on Tue Jul 20, 2010 12:07 am, edited 1 time in total.
In no way was I suggesting that the young ladies should actually be shot at! I'm just saying, when someone is staring down a bore the size of a drainpipe, you can be very... persuasive
I found a better video of the launcher in action. It is not using a high speed valve, You can see the initial puff as the valve opens and then begins to launch shirts. It is clear in this video that none of the shirts made it into the 200 section. The mount is easy to see. The angle is not adjustable.
Thanks for the advice everyone. Technician1002, We now have a better idea of what we want to do for the actual air release. We are thinking about using a scuba tank at around 3000psi, and then use a regulator to drop it down to 200-300psi. We want the regulator to let the air flow into an accumulator, and then use a piston to control a ball valve.
We are now wondering what a good benchmark for the air flow for the regulator and ball valve would be. I looked at one of your earlier posts here:
http://www.spudfiles.com/forums/dive-ta ... 21383.html
We are going to probably have some rotating barrels of some sort so we can have automatic firing, but do you guys have any idea of general numbers and air flow so rapid fire can happen?
you don't need a ball vale... but a dcv + QEV/piston valve
Children are the future
unless we stop them now
A SCUBA tank will work, the difficulty as you recognize is getting proper volume delivered in a very short time. This places the problem of what size accumulator can we use? The smaller the accumulator, the higher the pressure needs to be ( the efficiency goes up. ) If you want to hit the 300 section (insane power requirement) you will want an accumulator at most a gallon in size. (we hit the back of the 300 section with 3 gallon and under 40 PSI). With an accumulator about a gallon in size, you will need about 60-80 PSI to hit the 300 section with a huge valve. (2 inch).
Fairly simple math will find the volume of air you need for each shot. The volume of the container is used each time you add one bar of pressure to it. For example the 1 gallon would use 1 more gallon to raise the pressure to 1 bar, 2 gallon to 2 bar etc. To charge the 1 gallon accumulator to 80 PSI would need 5.5 gallons of air. Multiply the air per shot times the number of shots per minute rate. This will give the gallons per minute you need (It's a lot.)
Use of an online volume conversion can give the SCFM from gallons/minute.
Finding a regulator that can deliver that volume will be a challenge. You may have to re-design the accumulator size to match your desired rate of fire and lower your distance expectations to match.
The marshmallow cannon at 100 PSI launches shirts 200 feet with a 3 foot barrel. The accumulator is about 54 cubic inches. It uses a 1 inch valve. A 1.5 inch sprinkler valve on that size tank may be an option, but sprinkler valves are not well known for fast cycle times.
Due to reload times, it may be a good idea to simply have an accumulator and valve for each barrel. Load the barrels, charge the accumulators in parallel and use a commutator (look it up) to switch the firing power to each barrel in sequence. This would be my recommendation.
One of the local schools near here built a bank of robotic t shirt barrels. They use a single large accumulator and used a manifold to feed the individual barrels. Their video is here.
The lone barrel on top is the accumulator. Each barrel has it's own firing solenoid. The regulator is high enough volume to keep up with the fire rate.
For efficiency of air use, I highly recommend a small accumulator, minimal plumbing between the accumulator and barrel(s) and the biggest fastest firing valve you can get your hands on.
I can get you in touch with the Tigard robotics instructor if you need to ask questions about their launcher. I'm sending the email and name by PM.
[quote="Technician1002"] The mount is easy to see. The angle is not adjustable.
If you actually take a look at the front of the frame at 0:11 second mark you can see about 6 holes drilled through the SHS with a lug to adjust the angle of the barrel so i think it is adjustable. Either way the cannon is not as effective as you would want.
Also why not make the power adjustable so instead of moving the gun around the floor you could change power levels for different areas eg. front seats 100psi and top 2nd level seats 200psi. This would save having to move the gun and somebody running around trying to fill it with extra t-shirts.
We found a regulator (Modern Engineering Co. Inc., Meco, Type P, P-1-L) at our lab, and we were wondering how to determine its volume flow.
@Technician1002, Thanks for the contact info to the Tigard robotics.
I wonder, could you make a cloud style T-shit launcher...
Well, looks like this thing got off the ground!
Very nice. Well done. I think their specification page is in error on the 150 Yard range. Their valve CV is much less than mine. Their range may be right for balls, but not shirts.
They are using a 1 inch valve and list the specs as;
1" NPT MAC Solenoid Valve at ~17.0 cV Flow Capacity with a 23 ms Response Time
From their video, they are getting shirts from center court to the end of the floor, or about 70 feet with shirts.
Their rate of fire is very impressive.
Edit, I found another gatling shirt gun online. It is not robotic.
They probably regged the pressure down or changed the timing on the valves to limit flow. I imagine it's not so fun catching t-shirts bouncing off the walls
edit: Their 'first test' video seems to be shooting them closer to 100yards, hard to tell. 150 yards does seem like a stretch with that valve unless they can push the pressure above 150PSI (which doesn't seem likely if their reg only goes as high as 150PSI) and/or increase the valve dwell time.
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