Potato cannon, spud gun, tater tosser, starch useful resource deployment facilitators… They’ve quite a lot of names, however if you happen to grew up in a rural space, likelihood is you had one, knew somebody who had one, or yearned to construct your individual diy potato cannon. These PVC gadgets, fueled by Aqua Internet hair spray, are able to propelling a humble potato lots of of yards. The satisfying, and giggle-inducing, “fwoomp” of a potato being launched over the timber by no means will get outdated. The largest drawback with the old-school launchers was that hair spray makes a sticky mess contained in the cannon and may foul the igniters, in addition to the threads on the cap used to shut the again of the combustion chamber.
Utilizing the fundamental design of 1 I made years in the past, in addition to numerous on-line assets, I constructed a brand new, improved potato cannon that does away with the hair spray. As a substitute, this launcher makes use of propane, exactly metered and injected into the combustion chamber, to offer extra constant efficiency.
It’s a bit extra sophisticated to construct than the outdated Aqua Internet-powered launchers, nevertheless it appears to be like much more spectacular, like one thing out of a steampunk or sci-fi graphic novel.
Now, earlier than we present you the way this potato cannon was constructed, we must always tackle the elephant within the room. Make no mistake, potato cannons will be harmful if not dealt with or constructed fastidiously. Whereas the Bureau of Alcohol, Tobacco, Firearms and Explosives has decided that potato weapons or cannons are authorized to make use of and personal*, when used with potatoes for leisure functions, your state or municipality might have legal guidelines relating to their use or possession. It’s your duty to know the legal guidelines in your jurisdiction relating to potato cannons.
*The ATF definition of firearms, damaging gadgets, and gadget exemptions. Wikipedia has an entry relating to spud gun legality.
Just about not one of the elements utilized in setting up this potato launcher are getting used for his or her supposed goal. Nevertheless, launchers have been constructed for years utilizing these supplies, and the scale of the combustion chamber is conservative, in order to not push the bounds of the supplies used. The barrel, fittings, and combustion chamber of this launcher are all manufactured from schedule 40 PVC, which is pressure-rated. Don’t use schedule 40 PVC pipe that’s labeled mobile core (additionally referred to as foam core). Strong core schedule 40 pipe ought to be used. When gluing PVC pipe and fittings for a potato launcher, apply primer on the joints to make sure sturdy joints and wait no less than 24 hours for the pipe cement to treatment earlier than use.
Easy methods to Construct a Potato Cannon
The 1st step: Assemble the combustion chamber and barrel.
You’ll want the next elements to assemble the combustion chamber and barrel:
- 4-in. schedule 40 PVC pipe (10 ¼-inches lengthy)
- 4-in. schedule 40 PVC feminine adapter
- 4-in. schedule 40 PVC male adapter
- 4-in. schedule 40 PVC coupling
- 4-in. x 2-in schedule 40 flush bushing (x2)
- 2-in. x 1 ½-in. schedule 40 bushing (x2)
- 1 ½-in. schedule 40 PVC pipe (36-inches lengthy)
- PVC pipe cement and primer
You should definitely use the purple PVC primer on each the pipe fittings and pipe over the whole floor that shall be joined with the pipe cement.
Step two: Assemble the meter pipe.
Propane will solely ignite when at a 2.2-9.6 % gasoline to air combination. So, the meter pipe is used to inject a exact quantity of propane into the combustion chamber to maintain the combination proportion at about 4.5 %. If you wish to design a different-sized potato cannon, extra info and a helpful calculator for gas volumes will be discovered right here.
When assembling threaded pipe fittings, you should definitely use the yellow PTFE thread sealing tape on the threads. These are the elements you will must assemble the meter pipe:
- 3⁄8-in. black malleable iron, road elbow
- 3⁄8-in. black metal shut nipple
- 3⁄8-in. brass gasoline valve (x2)
- 3⁄8-in. x 6-in. black metal nipple
- 3⁄8 in. x 1⁄4 in. hose barb
- Yellow PTFE thread sealing tape
Step three: Assemble the propane valve and regulator.
You will want these elements to assemble the propane valve and regulator:
- Air valve regulator, ¼-in. NPT
- Bernzomatic torch head
- ¼-in. MIP x 1/8-in. FIP brass bushing
- ¼-in. x ¼-in. brass coupling
- ¼-in. x ¼-in. hose barb
- ¼-in. high-pressure gas line (12 inches)
- Yellow PTFE thread sealing tape
Step 4: Set up the meter pipe, propane cylinder, and valve meeting.
Other than the elements you have already assembled, you will additionally want:
- 14.1 oz. propane cylinder
- Scrap of wooden ¾-in. thick
- 7-in. hose clamps (x3)
- 12mm hose clamps (x2)
Step 5: Assemble and set up the deal with.
The deal with meeting will home a grill igniter that shall be used as a set off. These are the elements you will must put it collectively:
- ¾-in. PVC pipe (24-in. lengthy)
- ¾-in. PVC elbow (x3)
- ¾-in. PVC tee
- ¾-in. metal pipe hanger straps (x2)
- Grill igniter
- #8 x ¾-in. sheet steel screws (x4)
- #8 x 2 -in. pan head screws (x2)
Step six: Assemble and set up the combustion chamber vent.
The powered vent ensures you may have a contemporary provide of air every time you reload the potato cannon. After you have fired the cannon, some exhaust shall be left within the chamber, which can throw off the air-to-propane ratio. So, after the cannon is fired, open the vent, evacuate the exhaust, refill the combustion chamber with contemporary air, and shut the vent.
To assemble the facility vent, you want the next elements:
- 1 ½-in. PVC ball valve
- 40mm cooling fan
- 9-volt battery clip
- 9-volt battery snap connector
- 9-volt battery
- Momentary contact push button change
- #6 x ¼-in. sheet steel screws (x4)
- Small scrap of sheet steel
Step seven: Check for leaks.
As soon as every thing is assembled, you will want to check the steel pipe fittings for leaks. To do that, combine up some soapy water in a twig bottle. Open the entrance yellow gasoline valve, the black propane valve, and the silver regulator valve till the gauge reads about 90 PSI. Spray every place the place fittings be a part of. In case you see any bubbles, tighten the fittings till they cease.
Step eight: Hearth your potato cannon.
Wait no less than 24 hours after gluing the PVC elements of the potato cannon earlier than making an attempt to fireplace it. On the primary firing, I positioned a sheet of plywood between the cannon and myself and reached over to fireplace it. As soon as I fired it a pair occasions, I eliminated the plywood.
Brad Ford has spent most of his life utilizing instruments to repair, construct, or make issues. Rising up he labored on a farm, the place he realized to weld, restore, and paint gear. From the farm he went to work at a traditional automotive supplier, repairing and servicing Rolls Royces, Bentleys, and Jaguars. At present, when he is not testing instruments or writing for Fashionable Mechanics, he is busy maintaining with the initiatives at his outdated farmhouse in japanese Pennsylvania.