Project Air Cannon.
5x more power than a hairspray powered potato gun

3-19-05

Yesterday we found a valve stem to use for the compression chamber, and mounted it. We had to drill through the end cap of the pvc, then just push the valve stem into the cap. The stem works in a way so that you dont need to screw it in, or glue it. The additional pressure on the inside of the chamber will force it towards the outside thus securing it even more. As long as someone doesnt push it back into the chamber, we're fine (this would prove difficult though, the stem is lodged in there quite well, and after pumping it up to 100 psi it will be rock solid). All we have left is the electronic work, which might take some time to fix, because I'm having some problems with total voltage... it appears i might have to rewire some stuff. If all goes well, by tonight at 8:45 pm (24 hours after we glued the end cap on) we will be pumping it up for the first time. I plan to pump it up, then submerge it in the bathtub to check for leaks... if all goes well, we'll try to shoot it too.

This morning i did some calculations of volume, and the ratio of barrel volume to compression chamber volume. At the barrels current length of 61" or approx. 5ft the ratio of volume is 1:1.333. This is within our ideal range of 1:1 to 1:1.5. If I were to size the barrel for a 1:1 ratio, I would need a 81" barrel... which is 6'9".... a little long. I'll either scan the sheet i did the work on, or write something up later.

Lessons Learned
-Car tire valve stems arent always threaded... the one we used uses air pressure to hold itself in.
-Be careful tightening threads when it matters how the pipe sections end up. We had a bit of difficulty arranging the pipe sections so that the psi guage would be flush to the solenoid. I would recommend that you hand tighten everything, then tighten sections in intervals so you can see where everything is going to end up.

Pictures:

The end cap and the tire stem installed. Purple color is from pvc primer.

Final layout. Gotta wire the solenoid and we're done.

Current length of barrel. Yielding a 1:1.33 ratio.

3-16-05

A few days back Chris and I went to Puhls, Homedepot, and Ace Hardware and bought all of our materials. We have nearly everything, after 1 trip to HomeDepot, 4 trips to Puhls, and 1 trip to Ace. The solenoid sprinkler valve arrived today, so we fit everything together. All we need is a tire stem so we can pressurize the chamber. Once we have this part we can start teflon taping the threads and primer / glueing the PVC pieces together. We are also not sure where exactly to place the solenoid valve, as you can see in the pictures. I might put it ontop because it is closer to the projectile, and will add more section of pipe that will be pressurized. I will know by tomorrow when we start glueing. So far everything has gone relatively smooth except for finding the PVC... that was a bitch at times. I will label the parts in the pictures when I have time.

Lessons Learned:
-You can almost NEVER find a piece of PVC that goes directly from x to y. You have to go from x to x -1 to x - 1.5 and so on until you hit y. If I were to find an online hardware store where I could order any size of PVC to any size, I would be in heaven.
-Having friends that work at hardware stores is a very nice option.

Pictures:

Layout 1 put together. The black box will be fastened somewhere, and the wires form the solenoid will be wired into it.

Blown up view of layout 1.

Layout 2. The solenoid is closer to the projectile, and more pipe is pressurized.

3-10-05

Today I put wired the electronics together, and everything ready minus the wires that will go to the valve. If everything is right, all I have to do is solder a wire from the safety switch to the valve, and from the valve to the push button switch. I had a mishap with wiring and had to resolder a few things, and my dad also accidentally got burned by the soldering iron, but not too bad. lol. Pics later?

Lessons Learned:
-Molten solder + skin = pain
-Don't be an idiot, look over your schematics before you start soldering. Have a friend look at your schematics with a skeptical eye.
-Try to use good, prewound wire. I had to use some tiny-gauge wire that was laying around and it was a bitch to solder.
-Try to buy switches with large leads, preferably with holes in them to loop wire around.
-Solder with a buddy who can hold the wires in place, it will split your time in half.

Pictures:

First, my schematic along with soldering iron / solder / wire cutter / etc. This was actually after I reversed the things that I had messed up.

Close up of the rocker switch with leads soldered

Usually this next picture would show you that i fliped the switch and LED is now on, but the flash fuxored it. The LED was on, I swear

I taped everything up temporarily (have to add valve + wires) and shut the box

3-9-05

Today I went to Radioshack (yar) and bought the electronics stuff... I drilled holes in the project box and mounted the switches and LED. I ordered my solenoid valve also, so we'll see how long it takes to arrive. I ordered it from here

Lessons Learned:
-Be careful drilling large holes in plastic. Work your way up from a small drill bit to a larger one.
-If you have a large hole to drill in plastic, use the drill in reverse so it doesnt dig into the plastic quite as much. This worked out great for the push button switch.
-Radioshack rapes you on prices. If possible, buy online.

Pictures:

First, the black project box from radioshack. 6x3x2 with the forward rocker switch, ready LED, and momentary push button switch mounted. When I am finished wiring, you will flip the front switch, the LED will light up, then when you hit the momentary switch the solenoid will release the compressed air and the gun will fire.

From the inside of the box. As you can see I haven't wired anything yet.