Of course I wouldn't laugh. Some of mine are horribly crude. Just thrown together as sort of a rainy day project when I had some pvc parts laying around just begging to be used. Throwing one together is a fun way to waste some time. This big gun was more expensive then I would pay. Only if I had the parts laying around. Here's the story. I had a friend who decided he wanted to build a spudzooka to show off at a family reunion. He is not very good at building this type of thing so I offered to help. He funded the whole project - around $175. I just did the work. He used it at his family reunion and then just gave it to me. I was happy as he had never told me he was planning on giving it to me.
There are only a few innovative things I had to come up with, all related to the propane. I had tried propane in the past but, like you tapwater, had little success. Ether always worked better. (works like aquanet but cleaner and a bit more powerful) My friend wanted to use propane so i had to think of a way to make it work. After some thought I decided that I needed a way to accurately measure it - not just count the seconds the valve is open. The way I accomplished this was to use two valves at the tank. Open the first valve and let it pressurize the gap and you have a consistent way to measure. By changing the distance between the valves you can tune it. Between that and the chamber, I decided to use a short length of the lowest pressure rated hose I could find as a safety. If the safety valve at the tank got left open, then the hose would surely bust making sure it couldn't blow up anything more dangerous. Another thing that is important is to plumb the propane into the chamber ABOVE the ignitor. (toward the muzzle of the gun, which will be elevated for most shots) Propane sinks in air so this seems to work much better. I still had some problems igniting consistently, so I wired up the ignitor to spark in three different places in the chamber. This seemed to fix it. One last thing is that I needed a valve that opens the camber to the air. If you open that valve, and then shove the potato down the barrel, it shoves air in - refreshing the chamber. This way you never have to screw the endcap off. Other then that it's your typical design. If you screw the propane rig off it would look like a normal one but bigger.
I really need to get a picture of the beast. Soon as I decide to buy a new camera I'll get it up.
One interesting thing is that a few of my friends who are welders, on a rainy day, decided that they would weld a bunch of metal from the scrap pile together to make a turret for me. It mounts the gun in the back of my truck! While being HORRIBLY IMPRACTICAL, it is freakin awesome looking. You can swing up, down, and a full 180 degrees easily. And if you take the time to jump over the support, you can swing it a full 360. The impractical comes in the form of the barrel sticking so far out that you can't load it from the truck. If only it was breech loaded! Plus it would probably only take me about 10 minutes to get arrested if I drove down the road with it mounted. I once had some kids offer me $500 for it. They saw the rig when I was messing with it in the driveway. I'm sure they had some hilarious, though highly illegal, driveby's planed. One kid asked if it would fire eggs and another asked if you could shoot a roll of toliet paper and get it to unroll nicely as it flew. Don't quite know how that last one would ever happen.
Man I need to find something better to do then sit here tpying. I wonder if I have any pvc laying around...
