spud gun question ... UPDATED with pics

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oops......sorry about the size. Can't do much with it on this old computer.


A free fired .22lr casing to whoever guesses who the trigger man is......
 
Cazach said:
After the rig is built, wrap the chamber and barrel transition areas with multiple layers of duct tape. This will help reduce the chance of a big KB if you get overzealous with the propellant:eek:

Getting "overzealous" is only a problem if you have a propellant that has its own oxidizer built in (like powder does). If you're using some kind of hydrocarbon (ether, gas, etc.), there's a specific ratio of air to propellant that will produce the most efficient burn (for gasoline, IIRC, it's 24:1 air:gas). If you put too much in, you can "flood" the chamber, too much propellant and not enough oxygen to burn off all the propellant.

~GnSx
 
I had a compressed air version of this built from a small air compressor and an exercise bike. There were pix posted over on the rallying Point forum. Not as portable as the hairspray-powered version, but a guarenteed cure for juvinile obesity. Takes 2 min or so to pump up to 65PSI.

2" barrels will launch an empty caulk tube with a 2 in long 3/8" bolt and nut in the front for ballast. 1.5" works well for spuds, 1-1/4" fits a "d" cell battery, 1" fits a c-cell, 3/4" fits a marble, and 1/2" fits AA cells.

Aqua-Net unscented is the best and cheapest traditional propellant because it has the least amount of sticky goo to hold your hair in it. Compressed air has no residue.
 
I use 4 inch for the chamber and 2 inch for the barrel. Chamber is 12-16 inches long and barrel is ~3feet. It's small so it is easier to carry around, but still packs good power and range. Mine will shoot black walnuts 150 yards easy.

Needed:
glue
primer/cleaner
1 foot of 4 inch pvc pipe (pressure rated)
3 feet of 2 inch pvc pipe (pressure rated)
"2 inch to 4 inch pvc adapter" (pressure rated)
4 inch clean-out and screw plug (pressure rated)
2 dry wall screws
Coleman lantern sparker
drill
pocket knife
screwdriver (optional)
saw (not needed if pipe is precut to size)
rasp (optional)
wood chisel or jig saw (optional to make board/wrench)
Board 2-3 foot long and 4-5 inches thick (optional- decking works well)

Use the aforementioned coleman sparker. Drill a hole in the side of the chamber and screw it in. It is best to do this first.

Assemble like they said---like a bottlenecked round. Test fit all peices and clean before glueing. When glueing turn a peice a 1/4 turn to help smear the glue. Let the glue cure before shooting.

Drill two holes into the end of the barrel and screw in two screws ( I use drywall screws). The screws prevent the potato from sliding into the chamber.

Wrap the chamber with old blue jean material or wire screening as an added percaution. Just wrap it around the chamber and tape the ends with duct tape.

Use propane from a propane torch as fuel. It's the cleanest and cheap and a small tank will last a long time. Experiment with how long (3-5 seconds usually) you spray fuel into the chamber. Weather affects power. Remove plug. Insert torch end. Turn on torch breifly, then remove and screw in plug.

Use a peice of board (decking works fine) with a square hole cut in it the size of the square on the clean out plug. Cut the hole around 3 inches from the end to avoid splitting. The plug will get stuck sometimes and the board can be used like a wrench.

Bevel the "crown" of the barrel by removing the outside edge with a rasp. This will cut the potato to the "caliber" of the barrel for a good fit. Use the board wrench to gently pound it in.

Use a miter box to cut the pipe straight and clean edges with a sharp pocket knife.

loosely wadded up newspaper makes good "blanks".
 
Billl ~

What are you using for a valve & trigger on that?

pax
 
From my estimation, ABS is probably better than PVC, since it has thicker walls and the other reasons listed in that website bentioned earlier. Besides, it already comes molded in Tactical Black.:D

Which reminds me, I will have to post some pics of the EBR spudgun we built about 10 years ago. Tactical black ABS, 24"x3" chamber, 36"x1.5" barrel, custom welded grip assembly with collapsing stock, ventilated barrel shroud (like a Ma Deuce), under-barrel ramrod storage, and a crude "sniper-scope" (PVC pipe with crosshairs).

The neighbor who helped us build it has several in camo ("Jungle Spud Mk I-IV" stenciled on them) one even has a compensated barrel.

The magazine fed version is still in development.:evil:

ETA: the bevel is a good idea for properly fitted potatoes, instead of smashing it in with a board, I suggest twisting it in, then using the ram-rod. Be careful not to cut your hands if the bevel is sharp (it will need to be re-sharpened every few hundred rounds).

Also, a better method of shooting "blanks" is to simply cover the muzzle with masking tape, load propelland charge and fire. Makes a really loud BANG!.

Impressive muzzle flash at night.
 
1 1/4 inch bore barrels will shoot a foosball at near supersonic speeds if your chamber to barrel ratio is right. Yes, it'll penetrate plywood easily.

Schedule 40 PVC is the way to go if you can't get ABS.

Regards,
Rabbit.
 
Lots O' Duct tape

Several years ago I watched my roommate pull his LOADED spud gun from his trunk to show off for a new girlfriend. Did I say that it was loaded and had been for a few WEEKS. Lucky for him when we all made them we COVERED them with heavy layers of black duct tape. He jammed on the BBQ grill igniter a few times and the thing BLEW UP under his arm. Lucky for him the tape kept the pieces together and saved him from any real harm. He had a dinner plate sized bruise on his side and a few cuts on his arm.
The potato became glued in the barrel, this caused the little explosion thing...

It you use the coleman lantern igniter, make sure you secure it REAL GOOD. I have seen where they will slide out of the side the length of the stem and give a pretty good pop to your hand.

Also look for sprays that do not have water in the ingredients, they work well..

Good luck
 
There are various arguments in ABS vs PVC.

Some examples...

ABS is more pliable and flexible than PVC, and thus is more likely to tear or split in the event of an overpressure, while PVC is harder, and therefore tends to crack or shatter.

ABS doesn't weaken due to exposure to ultraviolet light, PVC breaks down (if you build a PVC gun, you need to paint it.) in UV radiation. ABS and PVC can both be dissolved by various chemicals, this can be a consideration in propellant selection for combustion guns.

PVC piping is pressure tested, so you know exactly how much it can take and how you can establish a margin of safety (key, especially for pneumatic type guns).

etc., etc.

I've always used PVC. Don't have anything against ABS, or anything, just always did the PeeVeeCee thang.

~GnSx
 
I usually

sharpen the muzzle to help in cutting into the 'tater.
Old WD-40, before they changed the propellant to carbon dioxide works great.
Night time you can see a nice flame come out.
Good luck.
 
Starter fluid has always worked best for me - mixture is critical but it is clean burning and so no goo residue. Hate hair spray.! I regularly make around 200 yards.

My 2" version has two reducers such that we finish up with a 90º bend of 6" as a combustion chamber - combustion seems way more reliable in the curved chamber - and my crossed wires for spark ar placed well in.

Re the chamfer - I recommend a chamfer which is 90% external and 10% internal - this means the potato slug is cut a fraction oversize and so when rammed in is a real good fit. I have pics if wanted.
 
Spud shooter

I have made 1 or 2.

The grill ignitor is the best way to light it, get the one that has the threaded extension that looks like a spark plug. You should not just use the handle as you end up with circular ring burns on your palm. Simply drill the cap and make a spark plug looking device in it.

1 1/2" barrel with a 3 inch chamber works nice, 10-12 inch chamber, 18-26 inch barrel.

1 1/2" PVC barrel can use 1 liter Mountain Dew caps as a wad, shoot anything that will fit and you can usually find the cap 20 ft away. Small rocks will kill birds.

Sharpen the INSIDE of the barrel so that the spud is forced into the barrel for a good seal.

Aqua net is the cheapest, a $1.79 can (huge) will last most of a summer.

Ether and WD tend to flood and can be too powerful.

NEVER use LP, or Acetylene.

BE SURE to use the tapered adapters and NOT bushings, Bushings are not pressure rated.

Also Clear glue and purple primer is a must.

Bad ideas include, but are not limited to:
Lighter fluid coupled with Nitrous Oxide.:evil:
 
'nother vote for Aqua Net

I've used many propellants but the hairspray is the most consistent. Do make your chamber from 4" pipe, about 8 or 10" long for good air to fuel ratio. Chamfer muzzle as described above.

Be careful--these things have some power. And you'll need muffs, because they'e as loud as a 12 ga.
 
Also

1 1/2" pipe for barrel is best.

You can use crabapples, cherries etc. first ramming down a balled paper 'wad' then the fruit then an over-wad. Voila: shotgun.
 
My second spudgun used a 2" id barrel...

reason: an old sock, cut into "rings" worked very well for wadding around a golfball, or a small ice ball (made from a water baloon, filled to a 1.75" diameter) and frozen...

golfballs and iceballs were capable of a GOOD 200 yard shot, and almost 100 yards with reasonable accuracy...

and, not that I'D know FIRSTHAND, but i was informed that an iceball at 50 yards would all but obliterate a plastic mailbox... :rolleyes:
 
please be careful!

I know most people probably already know this but since no one metioned it, potato guns can be very dangerous and have to be made CORRECTLY. I made one when I was a bit younger and used it with no problems until my best friend's dad came home early one day from work and told us he had just recieved word that his friends son was just killed when his potato gun exploded and caused pvc shrapnel to slice the young man's throat open. I promtly got rid of mine and stay away from them, you never know just how much pressure you are creating in the chamber. I am sure some people are very smart and know exactly what they are doing, but if novices make mistakes they could have dire consequences. Please be careful and have a safe Christmas. Happy holidays!
 
Alright, I'll spill on the latest design successfully employed by my family, a breech-loader with a removable chamber.

5'x2" barrel, 1.5'x4" chamber, with a lantern starter for firing. The barrel and the cap that attaches it unscrews from the chamber. The very back of the barrel protrudes about 3 inches into the chamber (about 5 inches from where it's actually held by the cap which screws into the chamber) and is sharpened somewhat to hack away excess 'tato(e). The barrel screws into the chamber, and a seal is accomplished by a combination of silicone grease fairly regularly applied to the threads and a cardboard gasket, also with silicone grease. The endcap of the chamber screws in and out for the spraying in of propellant. It takes about... mm.. a quarter second burst of starter-fluid from the spray-can to get the best bang.

The reloading process goes something like so:

Fwack!!

unscrew the barrel portion, unscrew the endcap (so the chamber can "air out" )

Whack a 'tato(e) of appropriate girth onto the breech.

Screw the barrel back onto the chamber

give the chamber a quick squirt of propellant

immediately screw the endcap on

place base of gun on hip.

Fwack!

~GnSx
 
GunnySkox said:
There are various arguments in ABS vs PVC.

Some examples...

ABS is more pliable and flexible than PVC, and thus is more likely to tear or split in the event of an overpressure, while PVC is harder, and therefore tends to crack or shatter.

ABS doesn't weaken due to exposure to ultraviolet light, PVC breaks down (if you build a PVC gun, you need to paint it.) in UV radiation. ABS and PVC can both be dissolved by various chemicals, this can be a consideration in propellant selection for combustion guns.

PVC piping is pressure tested, so you know exactly how much it can take and how you can establish a margin of safety (key, especially for pneumatic type guns).

etc., etc.

I've always used PVC. Don't have anything against ABS, or anything, just always did the PeeVeeCee thang.

~GnSx

Use grey UV stabilized PVC (Electrical Conduit) to get around the UV issue, Grey stuff is more plyable than white for less shattering, and I believe it is available in a Sch 40 and 80 rating. Could be wrong on that. Or for a little more cha ching, go get the yellow polyethelene that is used on Gas lines, it is more chemical resistant and stronger than PVC. does better in the cold as well. Does have to be heat welded together though. But I have always done things a little over the top.

www.mk1studio.com

I have been considering making one out of aluminum tube that we have left over from an aircraft intake manifold project we have been working on. I also have some 2" carbon fiber tubes left over from a project that never came to fruition. I have never made one but all the stories on this thread have me gettin' misty eyed.
:evil:
 
Just finished stuffing stockings (poor Santa has to stay up later every year...)

Giggling,

pax
 
2nd, 3rd + Hell yeah. Or at least, Pax please use your considerable literary talents to describe the Christmas morning and subsequent foray with the assembled heavy weapon.
 
The valve on the pedal powered gun is a 1" sprinkler system valve that comes with a small lever on the front to override the solenoid, so I don't need power to fire it. 24VAC sprinkler valves will work fine on 12 VDC.
 
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