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#1
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Re: Optimizing Air Cannon Range
Thank you all very much for your advice. Tonight I tested the cannon with 80PSI and shot a well rolled and rubber banded tee-shirt lubricated with talcum powder 25 yards. This is a significant improvement over last nights performance it is still lacking.
I'm not sure why the tubing would restrict our airflow. The opening from the tank to the tubing is 1/2 opening and I don't believe that can be modified with out significant structural changes to the tank itself. Since the tubing is a large diameter than this opening the tubing should not at all restrict the airflow no matter how long. I will however look into a butterfly valve. I am slightly worried about time however because the robot must be finished before 10/20 which is our homecoming game. Also does anyone know at a glance how fast could a butterfly valve open when actuated with a KOP pneumatic system? Also should be make a chamber of say 5" steel piping directly attached to the valve (which is directly attached to the cannon) to improve airflow; that is definitely an option. I believe (however I am often wrong) that because our cannon is 3 1/2' long (3" diameter) a chamber of 5" diameter piping 1'4" long would allow for complete expansion into the barrel. Would this have any significant effect on our efficiency? Thanks again, sorry for having so many questions. |
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#2
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Re: Optimizing Air Cannon Range
In addition to the questions above; Does anyone know a reliable supplier of butterfly valves?
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#3
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Re: Optimizing Air Cannon Range
Your valve is probably not that big of a problem right now, and our robot makes the horn sound as well, but functions just fine... What will definitely improve your performance would be finding a tank with an opening the diameter of the pipe you are using, as that is the only (major) bottleneck in your system right now.
![]() (Just included the gif for interest's sake ) |
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#4
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Re: Optimizing Air Cannon Range
If you're using a tank with a 1/2" hole, why not move most of your system down to about that?
We decided to go with a 3/4" Rain Bird Valve and 5/8" ID tubing since we knew the tank was a bottleneck. The advantage is we now have a higher psi rating on them all, and I'm not so afraid to take it up to 120 when the time comes anymore. Of course we're actually testing it today, we'll see how it goes. |
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#5
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Re: Optimizing Air Cannon Range
There are several things here:
*You want your air to move as easily as possible = use the biggest valve you can, and the biggest pipe/tubbing from the chamber to the valve to the barrel. In a perfect world, if you were using a 2" barrel, a 2" valve and 2" pipe from the chamber to the valve would be great. That may not be possible though. So, your 10 feet of 1" tubing is costing you a lot of power. *You want to release all of your air at once+ get the fasting acting valve you can find. A good solution is a sprinkler valve. These are electrically controlled, so you could use them with the FRC robot components. In a perfect world, you might use a large chamber, have a pipe come out of one end the same size as your valve, have that pipe turn 180 degrees, go into the valve which then goes right into the barrel. Really, you want as little extra pipe as possible. These t-shirt launchers are a lot like pneumatic potato guns. I suggest you explore this site for some quality information: This is a god example of an efficient gun that you might consider. http://spudtech.com/detail.asp?id=52 You may want to peruse the rest of the site for more information, especially the "links" tab. If you want more information about optimal chamber to barrel size ratios, PM me, there is much more info out there. |
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#6
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Re: Optimizing Air Cannon Range
I'm still skeptical of unmodified sprinkler valves. That's a heck of a restriction in your system if you can avoid it. Energy spent making your robot honk is energy that's not getting transferred to your shirt. I will admit, however, that you might not have a better option before 10/20. As you'd guessed, a large chamber connected directly to your valve would be much much more efficient.
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#7
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Re: Optimizing Air Cannon Range
Quote:
The plan is to test this manually as a comparison to the sprinkler valve and if it yields a better performance, the we will have to build in a festo solenoid activated pneumatic piston to open and close this valve remotely. We have a bit more time to prototype as we are shooting for, pun intended, the final game of the fall when the two schools who comprise our robotics team play each other Our current setup is in the CD media. bench prototype It shoots a tee shirt 25 yards downrange with a maximum altitude of 30 feet at a 45 degree angle and internal pressure of 110 psi. Performance is limited by a slow opening valve. We discovered this when we added a second valve to our set up and were testing the timing of the two opening together. We decided the mechanical operation of the pressure diaphram was not going to yeild consistant and tunable results for a simultaneous opening. APS Last edited by Andrew Schuetze : 02-10-2006 at 00:28. Reason: added CD media link |
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#8
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Re: Optimizing Air Cannon Range
I have found in my vast experience and long history of projectile launchers. the more kenetic energy you can put into a mass before it leaves your grip the faster and further it will go. i have completely given up on Compressed air and almost only use CO2. its cheap, available anywhere with paintball. and as long as there is Liquid CO2 present in the tank the gas maintains a pressure around 1100 PSI. the more pressure you have the smaller you can make your device and the more energy you can put into your projectile's mass. i have stop referring to my CO2 potato launchers as launchers and rather as potato sniper rifles. the vegetables come out of the barrel so quickly that at a range of about 30 feet potato's atomize upon impact of a hard surface. If you relay want to throw a t-shirt up into a crowd with compressed air alone you are going to need allot and I mean allot of it! and a very long barrel to transfer that energy to a shirt. if you want a device you can hold in your hand and shoot out into a crowd an long distances of 150 feet and beyond you simply need more pressure. But please be carefull and remember how Maude Flanders Died.
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#9
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Re: Optimizing Air Cannon Range
A sabot casing will greatly increase performance. There's allot on the web for water balloons. Co2 is much better than air, however it's high pressure and needs allot more care. Co2 has it's limits when when large volumes are released. The drop in pressure limits the flash rate. That's why nitrogen has taken over for serious paint ballers.
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#10
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Re: Optimizing Air Cannon Range
Quote:
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#11
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Re: Optimizing Air Cannon Range
We performed the test of a manual ball valve today during class. We doubled our range and added to the altitude achieved. The diaphragm based sprinkler valve opens too slowly and limits air flow as suspected. To make this a remote device on the robot we'll use a short throw pneumatic cylinder activated by a festo solenoid. I've got video of the test but no place to upload at the moment that the school filters will allow me access.
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#12
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Re: Optimizing Air Cannon Range
Finally got our cannon mounted, finished, and tested today. ~40 feet at 80 psi. We hope to extend the range later, but it will be more than good enough for Homecoming tommorow.
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#13
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Re: Optimizing Air Cannon Range
It may or may not be relavent now, but if you use CO2 it will be up around 800 psi.
EDIT: oops didn't see the second page of the thread. And aren't paintball gun tanks at around 800 psi? Last edited by John Gutmann : 16-10-2006 at 00:53. |
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#14
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Re: Optimizing Air Cannon Range
Quote:
wikipedia: "at room temperature it becomes a liquid at a pressure of 60 bar. A tank of liquid carbon dioxide provides a constant 60 bar pressure until the tank is close to being empty." 60 bar = 870.226 psi Last edited by Tytus Gerrish : 16-10-2006 at 10:17. Reason: inc0orrect info |
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#15
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Re: Optimizing Air Cannon Range
We just built an air cannon to fire confetti.. with a delrin projectile we got something like 80-90 ft of range..
I agree that the biggest problem is the valve.. We got a manual-open spinkler valve which seems to work better than the solenoids (which seems to "honk" as others have said) to be honest, the best solution is to use a large valve but those are hard to find, and diaphram types seem to open faster (from what I've read) we'll be improving our cannons (we have 2) so I'll keep posting. |
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