Here’s the spudgun I’ve been designing for awhile.
I've posted various threads about bits and pieces of it. I intend to document (with pictures) the build process, and post destruction pics and hang time test results when it's finished.
It’s an over/under combustion made of cellular core ABS. I’ve pressure tested most of these components (not these exact ones, but identical ones [same manufacturer]) to 100psi and I feel safe using them in a combustion. Also, the failure characteristics of ABS are much cleaner than those of PVC – AKA less shrapnel.
My objectives for this cannon were to make it:
Over/under, obviously
Breech loading (no more ramrod’ing potatoes down the barrel!)
Ball-valve vented (no more removing a cleanout between shots!)
Built cleaner and more professionally (No duct tape/rats nests of wires)
Safer (Only holes in the combustion chamber are where a pipe and fitting overlap)
More reliable (Stun gun and spark strip ignition, in addition to the usual propane meter)
More user friendly (recoil pad, better grips)
As lightweight as possible (failing here if anywhere….)
I wanted to use a 2” ball valve for venting, but had a 1.5” laying around, and decided to save the $15. This cannon is built largely from spare parts and parts robbed from old cannons (Don’t worry, I didn’t unglue any fittings to salvage them).
The combustion chamber is 20" and roughly 250ci. This provides a 1.25:1 ratio for a 10' golf ball barrel (coming soon
). Should be nice and loud with shorter barrels, too.The recoil pad will consist of a big piece of black foam rubber zip-tied to the U bend (back end) of the gun.
The spark strip is still a work in progress. It's a piece of copper-clad circuit board with 4, 1/8" spark gaps, mounted vertically in a piece of 1.5" pipe cut lengthwise, which will be glued (with non-permanent glue) to the inside of the chamber.
The cannon is currently dry-fitted together (no pieces glued) for two reasons:
A) I want to get your opinions about it before I glue it and make it permanent
B) I have to wait until it warms up. ABS glue and krylon paint don’t work well at 25 degrees Fahrenheit.
Here are the plans I originally intended to work from:
However, I already had a few parts, so I varied a bit from the plans.
Here are pictures of the cannon, with parts separated and dry-fitted, and pics of the “donor gun” I’m taking the propane meter and handles from.
New over/under gun, parts exploded view:
The 4”-2” reducer that connects the ball valve to the chamber will not be glued; it will be attached with bolts. See notes below.
Close-up of barrel put together:
Barrel exploded view:
Note, the barrel (1.5” pipe) passes through all 3 fittings. The “ridge” in the 2”-1.5” reducer is dremeled out, but it’s still a nice tight fit.
Breech knife to cut potatoes:
Barrel rest:
The barrel rest is a short section of 2” pipe with “grooves” filed/sanded into it to make it fit snugly against the 4” chamber below it, and the ring of 2” pipe above it. This allows the 1.5” barrel to turn inside the 2” rings, and holds it securely in place. There are grooves cut in the 2” barrel-holder rings to keep the plastic zip ties from moving. Zip ties are strapped down tight with plyers. I’m building a second set of barrel holder rings for a 2” sch80 barrel (golf balls anyone?).
Note, there are two barrel rests total, though the pictures only show one. Both are made now, but I only had one done when I took the pics. The second one sits about 10” back from the first one, towards the U bend.
Over/under gun dry fit together:
Breech open
Breechclosed
Valve end
One of my objectives was to minimize holes in the chamber, included those for wiring. Here’s how I’ll pass the wires for the spark strip and fan through the chamber. Where the back (valve-side) bell reducer is attached to the chamber, 4 of the bolts will have this setup:
The stun gun circuit, safety, and fire switches will be contained in the rear handle. The battery and switch for the fan will be contained in the front handle.
The entire gun will be painted glossy black when everything is glued and secured.
Here are pics of my faithful old gun which will be donating it’s propane meter and rear handle to the new over/under gun.
This gun is years old. I built it back when I was 14 or 15. It’s seen 600-700 potatoes through it, and had the police called on me three times (The cops all thought it was awesome, too). It served me very well. It’s shown here with a short “noise-maker” barrel. I have barrels upto 10’ long for it that will be adapted for the breech-loading system on the new gun.
Note the unregulated propane setup. It works wonderfully.
Open the needle valve from the torch and the first (tank-side) ball valve, leaving the second (chamber-side ball valve) closed. Wait for the gauge to read 50psi, and close the first valve, then open the second valve to vent the “shot” into the chamber. Close the second valve and open the first, and repeat the process (two “shots” at 50psi seems to be the right mix). Turn off the ball valve and vent the propane from the meter pipe when you’re finished shooting.
Anyway, Please give me your opinions on this setup before I glue it. If you have any additions or suggestions to make, PLEASE GO FOR IT! I want this gun to be as nearly perfect as possible; I don’t intend on ever building another combustion spudgun.
Peace,
Pete Zaria.
, As soon as I read the thread title "Pete Zaria's..." I knew it had to be good. Don't worry you didnt disapoint me 
. Nice job on the barrel support and make sure to paint that ball valve 
Looks funny b/c its white 
I like the way it is, Don't see any reasons to change the design layout. Do you know how much it will weigh when finished propane and all? Oh and make sure to remove those barcode stickers 
