I finished my gunmaker apprenticeship project. Maybe I can graduate to "gunmaker"now???

A little fun here. Probably verboten with the rules. But it's a single shot and dare I say; a fine gun. So maybe the moderators, that are allowing all the other BS that goes on this site now, will allow this little diversion.

About 5-6 weeks ago, I made a kind of a test mule for a pneumatic tennis ball launcher. I was just testing the concept and it was a crude setup of a pipe of the right size an irrigation valve and a small fire extinguisher tank, all in a straight line. With a 100 psi, it launched a ball down the street pretty far and more importantly, with great finess. My plan was to make a double tennis ball launcher.

Well, the best laid plans... The neighbors were down for our little daily happy hour and dog playdate. The wife, husband and daughter all shot it and were thrilled. Later the wife asked if I could make a bespoke piece for her husband as she was at a loss as to what to give him for Christmas. I figured 'what the heck' sure I'd build one. Something simple and quick. That was what? 5-6 weeks ago? I think I have a time card at my friend's shop now. They start at 6 a.m.. I made that starting time exactly zero times. Somewhere around 8 to 10 am is my comfort time.

The design evolved over the first few weeks and kinda jelled into this O/U design. Somewhere along the path, the client changed from tennis ball caliber to small potato and assorted veggie caliber.

These pictures show it "in the white" as it is now. The "client" was shown the fully assembled article for the first time tonight. Originally, I was "contracted" to just make it and she would finish it in a flat dark earth rattle can finish. But when shown it, she was so taken with the machined and fabricated finish that she wanted it to show. So, we're currently undecided on "in the white" or a chromic anodize color.

Enjoy.
[img]https://i.imgur.com/KWZtgUQ.jpg?1[/img]

[img]https://imgur.com/a/2dADVwy[/img]

Too cool, dude. How are the shots going to be regulated as to amount of air release per pull of the "trigger", Chuck? Tank/shot capacity?
JR

No self respecting gunmaker would have built something like that in less than two years Chuck.

Daddy, I want one!!!

How does the trigger work, Chuck? I assume it's incorporated into that irrigation valve.

Also, what's your rate of twist? I assume you know that a round ball requires very little twist rate to stabilize.

SRH

Nice work- what analysis Stainless steel did you use. Tig welds, right? OK- a tennis ball has the same dia= ball after ball-etc. But small potatoes are not uniform in dia, density, weight, etc. so how do you establish a MBD factor to allow for that?? Just wondering is all. RWTF

John, it's a single shot, total tank dump.

Stan, The trigger is a simple air bleed valve that vents the diaphram chamber and allows the valve to open, the same as when the irrigation valve solenoid lifts and vents. The bore is smooth. I'm retiring from my short career as a gunmaker. The hours are long and the money is short. Now seeking a new career that has less hours, more money and more libations.

RWTF, No stainless was harmed in the construction, except possibly the female flare nut and sleeve. The tank was a blue propane torch tank that I removed the base from and soldered in some 1/8" NPT brass bungs and drilled out the neck, the tank fitting is a modified pipe fitting in which I modified by single point threading the 1"-20 thread internally to fit the tank, The Irritrol valve is plastic, the trigger guard is cold rolled mild steel, The AR-15 grip fitting is aluminum machined from a block, the tube assembly is steel, the back of the barrel has an aluminum fitting machined to fit a -12 flare and thread into the bore of the barrel with 32 threads per inch, the barrel is 2" x .065" aluminum, the barrel shroud is 2.5" x .065 aluminum tube, the aluminum picatinny rail is contour machined to fit the shroud, and the barrel to tank clamp is machined from 1/2" aluminum plate.

It took a couple hundred dollars in materials, not counting any scrap and ideas that didn't work. Labor and span time was probably 6 weeks at about 25 hours a week on average. Design work was on the fly mostly and the rest spent over a good cab or beer.

The wife of the recipient originally wanted to do some work to it to put some of her labor into this gift for her husband and thought she'd paint it FDE (dirt color), but after seeing it cleaned up and nearly finished, she thought it should show the metal work. So, she's asking me for counsel here. I'd have all the aluminum anodized in playful toy like colors, but she's still on "tacti-cool" looks. Maybe we'll leave it bare except for painting the steel parts.

Anyway, it was a fun project. But I'm happy to be finished.

Wow! Bobby

That is way to cool. Adam from myth busters fame doesn't have anything on you for innovation & craftsmanship!

Probably better have lots of liability insurance if giving those away. A good umbrella policy too. Just in case the unexpected happens.....

How do you fill the tank?
We used to make them out of beer cans and use lighter fluid for propellant.
Spino would have approved. Loved to chase squirrels and tennis balls.


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Leshiy 2

I think Chuck is still in CA, and this state, in its infinite wisdom, has made it a crime to use a combustion-propelled spud gun. Compressed air is OK, but the old school hairspray guns have disappeared.

I used to hunt at a duck club that had the occasional poacher problem. We had a barn up on a hill, from which we could see most of our hundreds of acres of ponds after the leaves fell off the trees. The Saturday afternoon poachers would sometimes find themselves bombarded by flying potatoes, launched quietly from an ABS pipe fueled by hairspray.

I'd have it dipped (immersion graphics) in digital desert camo. I'm not big on shiny guns ....... even a tennis ball gun. But in the end, it's what makes the customer happy. I mean, it's important for repeat business. Word of mouth advertising and all ...............

SRH

Lighter fluid is all well and good, but white gas for a camp stove works more better! You do need to use steel beer cans.

The tank is filled with a simple schrader valve. Propane tanks typically have over 200 psi in them. I've run this one to 180 on my off-road portable compressor.

The projectiles are whatever you can stuff in a 2"x .065" wall tube. Small russet potatoes, apples, etc. My interest in it originally was for a tennis ball launcher to send a ball down the block for the dogs. I really don't have a desire for launching spuds or similar, but that's what the consignee wanted.

That would be very unexpected. So much so, that I think I need to focus on more likely scenarios.

I'm pretty sure that it is the BATF that frowns mightily on potato guns that are fueled by combustible products such as hair spray (lacquer and thinner). Perhaps a replica pre-revolutionary flintlock black powder potato gun would be legal though.

If making potato guns illegal seems petty, think about this...When we were kids, one of my Dad's neighbors called the cops on us because we were flinging apples with a stick. Actually, he thought it was his civic duty to call the cops on us about twice a week. For some reason, he reminded me of our own Gladys Kravitz, aka old colonel.

On this pneumatic potato gun, it might not be a bad idea to incorporate a pressure relief valve set to a safe working pressure, even though most air compressors won't exceed 180 psi. I'd imagine that British potato guns are subject to proof laws.

So, from someone who's never even seen a potato gun, what's the range of those things, fueled by hairspray or compressed air?

SRH

google pumpkin chucking, crazy stuff. They throw pumpkins hundreds of yards with compressed gas.

So, for all the questions about spud gun legality, ATF says they aren't firearms as long as they are muzzle loaded and used for recreational purposes. CA AG policy (never heard of any prosecution) is that a spud gun that burns something as a propellant, meets the definition of a firearm. Other states and municipalities may have their own definition.

However, this is why I made a compressed air spud gun. As with any common item, as long as it is used in a manner not to intend harm on a person, it isn't a weapon. The nature of this particular design limits the power to pressure attainable in the tank, which apparently is much less than combustion spud guns. My design is not unlike some of the rock concert T-shirt launchers used to put a T-shirt out in the crowd. It wasn't designed to be particularly powerful. I actually don't know how far it will push a spud as I haven't shot it where I could see where it lands. I made it because I like making things. It has "tacti-cool" features because that was what my neighbor wanted. It was made more to put a smile on someone's face than functional use.

I have in mind to make a sxs tennis ball launcher using a couple large diameter carbon fiber tubes and a trigger plate from an old sxs shotgun. But my current dog didn't like the noise from my tennis ball test mule. So, that novelty is shelved.

For you guys that want to put a tennis ball out there 1/4 mile, there are $50 hairspray tennis ball cannons on Amazon.

Needs a plenum so you can make it multi shot without having to fill the tank after every shot. Or some weirdo neighborhood kid that doesn’t mind pumping it up after every shot. Mount a go pro on the rail to make videos to entertain the double gun bbs.
http://tuhsphysics.ttsd.k12.or.us/Research/IB07/GramRecoSire/index.htm


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Air is cheap. Clean, dry compressed air not so much.

Must be a regional thing, but, our combustion power launchers were always fueled with automotive starting fluid, not hairspray. I can’t remember the last time I saw a can of hairspray, but, there is starting fluid in the shop.

Ether is handy for getting tires mounted on rims, too.

Best,
Ted

Stan, I haven't seen a potato gun in use for probably 20 years or so, but a friend made one with a barrel of 2" PVC pipe around 42" to 48" inches long, The combustion chamber was made from a 4" tee with a reducer, and it used an igniter from an old gas grill. I never measured the range, but I'd guess it was launching a good sized potato at least 250 yards or better. And when he managed to hit the side of a barn about 200 yards away, it splattered the spuds and made a very loud thump. I'm surprised they didn't break the old chestnut siding boards. It was impressive enough that I was a bit concerned about the chamber pressure that was involved. A potato weighs a lot more than a tennis ball, and I wondered what the burst pressure of those schedule 40 fittings would be.

We also learned that you could dump a little calcium carbide and water into an empty metal 5 gallon tar or paint bucket, and crimp the lid closed. The fuse was a paper soda straw crimped closed. When the acetylene that formed detonated, it would open the bucket at the seam and launch the lid almost out of sight, and the sound was deafening.

The beer can guns were simply noise-makers, and with the cans opened at both ends and taped together to form the barrel, they came apart at the seams pretty quickly if you tried firing even lighter projectiles. The pumpkin chuckers SKB mentions above are very impressive to see too.

To answer RWTF's earlier question about sizing a potato or apple to the bore... The muzzle of the PVC barrel is sharply tapered so that it cuts the projectile of choice down to a perfect bore size fit as it is rammed down the barrel. No wadding is necessary. Sometimes I really wonder how we lived past adolescence.

Was not my gun, but one of our more creative members put together a length of ABS pipe with a combustion chamber and igniter. Overall length was about 3-4 feet and it was surprisingly accurate after the first ranging shot. Since we were launching from a hill, it seemed to carry 300-400 yards on a good day, using premium hairspray.

A cousin's son had a PVC pipe potato launcher, that if memory serves, was fueled by starting fluid with a barbeque igniter. The one and only time I saw it was when I was at my cousins cabin and we were shooting the potatoes across the river that flowed past the cabin. We could easily hit the opposite shore, at least 150 yds away.

It happened to be during the heat of summer and there were a bunch of weekend warrior tubers floating the river. I think when they approached the cabin and saw us firing the potato gun, they got a bit nervous, at least from the looks we were getting from some of them.....no tubers float device were sunk!

Probably all of the tubers were not locals. The locals use the river for fishing, fly or otherwise and they (the tubers) probably thought we were some N ID rednecks out to terrorize them!

That's a darn cool set-up you put together Chuck!

This thread makes me miss Miller. He'd be providing us a calculation for the ballistic coefficient of a potato.

Did you ever make acetylene bombs? Get the cutting torch perfectly dialed in, snuff the flame out on the bench, and fill balloons with the gas. We usually put the ballon in a paper bag, and lit the bag on fire after dark. Spectacular homemade firework.

One kid’s Dad was a pipe insulator, and always had some sort of industrial contact cement you couldn’t buy at a store on hand. We would paint the inside of a cardboard box with the stuff, quickly tape the box shut, and launch it into a bonfire at night.

Everything I like is illegal.

Best,
Ted

Ted, at one job years ago, my co-worker filled a heavy black 55 gallon trash liner with acetylene, and a splash of oxygen for good measure. The igniter was a flashlight bulb that had the glass broken with pliers. He soldered about 100 feet of two conductor wire to the bulb, and taped that inside the filled bag. He set it outside the plant, and used a 6 volt lantern battery to light the exposed filament from inside the building. You would have thought a gasoline tanker had exploded from the sound of it, and it shook dust off of the trusses.

I saw the aftermath of a slightly smaller version of acetylene in a trash liner. It ripped a steel commercial man-door off the hinges and bent it badly. That was a practical joke that went a bit overboard, and the millwright who did it told me he thought he was permanently deafened afterward. It would be a great noisemaker for the Fourth of July, but with a plastic bag containing something that explosive, I kinda worry about static electricity setting it off while taping it closed. At very least, I'd expect ruptured eardrums from the concussion.

Probably the governor on our projects was the fact that welding gasses have always been expensive, and we were too young to buy them.

Pinch a couple balloons worth off the old man’s torch tanks ? That would work, but, filling a 55 gallon bag with the stuff would have gotten us busted.

Or, killed. The percussion from a good sized balloon going off is fearsome. 55 gallons? BATF would be there.

Best,
Ted

In a past life, we would fill trash bags with a mix of oxy-acetylene and shoot them. Just about anything larger than a 22 would set them off, they were so unstable. One night a friend was filling one by hand and we surmised his poly shirt generated a static spark to the bag and boom. It blew off his shirt, burned all the hair off his chest, eyebrows and arms and knocked him on his arse. He was pretty much unharmed except for his hearing.

Another venture with the same crowd and same era, we inflated a weather baloon (remotely) with couple hundred yds of hose, and detonated it on a dry lake with a surplus piezoelectric bomb trigger and a broken flash bulb. That one rocked to desert floor and had a visible shockwave.

Then there was the 3000 psi water rocket...

Definitely an era of stupid antics

He he he

Candles set at 10 foot all around a 20 pound propane tank down in a dry playa.

No clouds, no wind.

From a sizable distance, shoot off the valve.

YEEEE HAWWWW

LONG time ago

Once upon a time I was going in the house on a late fall afternoon, when a neighbor "flew" into my drive in his p/u and yelled to see if I had a disc harrow hooked to a tractor. I nodded yes and he said "Larry Purvis' house is on fire and my hayfield is right behind it with many rolls of hay sitting in it. Please come quick and harrow a firebreak around the house."

I rolled the IH 1466 over there asap and begin making laps around the sides and back of the house, between it and the hayfield, trying to grind up the thick sod. The house was in full blaze and I noticed a 300 gal. LP tank in the yard. I was passing very close to it and the paint on the outside began smoking from the heat. One pass, as I got right beside it, the pressure relief valve let go............... my wash lady knew something serious had occurred.

SRH

Something like this? Not a lot of difference between pumpkins and potatoes in launch mode.