Introduction: Tar and Feather Gun
The Tar and Feather Gun* is for you. Live out all of your Bugsy Malone fantasies with this fun and messy contraption:
As far as I know, this has a fairly unique design among water (well, foam) guns in that it has a breech-loaded cartridge mechanism. The beauty of this is that you can quickly reload with a variety of ammunitions in pre-filled containers. More importantly, once you've fired the gun you can eject the depleted cartridge from the rear of the gun with an extremely satisfying *ka-chunk* sound.
Read on to find out how I built it!
There are quite a few things that can go wrong when you're building and playing with this gun. You'll be using sharp things to cut plastic. You'll be playing with drills, saws and toxic glues. You'll be putting a home-made pressure chamber under a lot of internal stress. And yes, you'll be shooting your friends in the face. Please be sensible. Wear safety goggles and use your tar and feather gun responsibly.
Whatever you do, don't leave the gun lying around loaded during an MIT frat party. Otherwise this will happen:
*a.k.a. "the personal pneumatic variable payload delivery device"
Step 1: Materials
For the gun:
- 2" PVC tube - 11 inches
- 1.25" PVC tube - 7 inches
- 2" PVC cap x 1
- 1.25" PVC cap x 2
- 1.25" PVC 45° connector x 1
- 1.25" PVC straight connector x 2 (note: these should fit snugly inside a length of 2" tube)
- Bicycle pump
- Old bicycle inner tube, including valve
- 1/4" brass bushing
- 1/4" right-angle bend that can screw onto the bushing
- 1/4" ball valve with lever (must be able to open and close easily and smoothly)
- 5/16" vinyl tubing - 12 inches
- 1/4" plywood - 12 inches x 6 inches
- Assorted scrap wood
- 2 small but powerful neodymium magnets
- 3 feet of stiff spring wire
- 2 small hinges and matching screws
- 1 sachet of sugru
- Plumbing putty
- Hot glue
- "Amazing Plumbing Goop" or some equivalent sealant
- Self-bonding silicone "rescue tape"
For the cartridges:
- 1.5" PVC tube - 33 inches (note: this should fit inside a length of 2" tube, with just enough room to slide freely)
- Toilet tissue
- Adhesive tape
- Assorted fillings, e.g. shaving cream, Jell-o, flour, etc.
Step 2: Pressure Chamber
For the sake of compactness, I initially decided to have the pressure chamber contained within the grip (or stock) of the gun. Once I started building it, I soon realised that it would be much simpler for the pressure chamber to be the grip.
The basic shape of the grip is made from two lengths of 1.25" PVC tube (3 inches and 4 inches), joined by a 45° connector and capped at both ends.
Ultimately, my decision for the size and shape came down to how comfortable it felt resting in my hand. If you're building this yourself, take some time to adjust the lengths accordingly so that you have a comfortable grip.
Step 3: Measuring for Holes
The pressure chamber needed two carefully drilled holes, one for the bike inner tube valve and the other for the pressure outlet to the trigger and barrel. I say "carefully drilled" because they needed to form tight enough seals to maintain the chamber's pressure.
For the pressure outlet, I drilled a hole through the 3" length of PVC tube and corresponding hole through the end cap, so I could thread the brass bushing tightly through both pieces. I drilled another hole further along the 3" tube, at 90° to the first, just big enough to force a bike inner tube valve through.
Before drilling any holes, I made sure that there was enough room to attach the bike pump and the lever valve without causing problems when the whole thing was assembled.
Step 4: Drilling Holes in the Pressure Chamber
The actual drilling was very straightforward with a pillar drill. Notice in the fourth picture here that the hole in the PVC tube is slightly larger than that in the cap. This is so that the collar of the brass bushing fit snugly inside the hole in the PVC tube, while the (thinner) threaded neck of the bushing barely squeezed through the cap.
Step 5: Gluing It All Together
Once I had everything neatly aligned, I glued the bushing and the inner tube valve in placed with superglue then Plumbing Goop. Lots and lots of Plumbing Goop.
From experience, I can tell you that this is probably the most important step to get right. If you're trying this and you feel that any of the joins are at all loose, undo them and start again. That might mean cutting a whole new batch of PVC tubing, but it will be worth it. If this pressure chamber can't hold pressure, then the gun becomes pretty useless.
Step 6: The Cartridges
To make the cartridges, I cut six 5.5-inch lengths of the 1.5" PVC tubing and sanded down any rough ends so that they wouldn't tear their covers later.
Step 7: Barrel
The barrel was made from an 11-inch length of 2" PVC tube, sawn at a 45° angle about 1.5 inches from one end. You can see here how it was designed to fit on top of the pressure chamber, then open downward to allow the user to insert and remove cartridges.
Step 8: Making a Spring
To my mind, the coolest part of this entire project is the cartridge ejection mechanism. It's so satisfyingly chunky and robust that I found myself wasting a lot of time in the lab violently ejecting empty cartridges at myself and those around me.
The key to the ejection mechanism was having a good spring. Since I thought I'd be unlikely to find a large (but not too powerful) compression spring that fit neatly inside the barrel of the gun, I decided to make my own. To do this, I took a three-foot length of stiff spring wire and wound it tightly around a length of 1.25" PVC tube. In order to keep one end anchored, I poked it though the side of the tube (see picture).
Having made a basic coil, I wound it again around a slightly thinner piece of dowel to tighten it.
There are much better ways to make springs involving drills, lathes or even specialized spring-turning devices. For my purposes, a rough and ready hand-twisted spring was perfectly fine. The pictures below show a slightly wonky-looking spring. I actually made a second, neater one that was used in the final device.
Be warned, though: if you try this, please wear safety goggles, thick gloves and something with sleeves. Also, it's probably better to hold the loose end of the spring wire with a pair of pliers or even a small vice. If you accidentally let go of the spring while you're winding it (and you will), it will whip round like a frenzied snake and try to bite out your eyes. Trust me, it's not pleasant.
Step 9: Anchoring the Spring
I anchored the spring inside the barrel of the gun by passing it through a pair of holes drilled just inside the barrel's non-diagonal opening.
Step 10: The "plunger"
The next step was to give the loose end of the spring a good surface with which to push cartridges. I wanted a short length of tubing that would be able to slide smoothly up and down the inside of the barrel with as little sidewards motion as possible, so I took a 1.25" PVC straight connector and sawed off a ring about an inch from the end.
To make sure it didn't stick inside the barrel, I narrowed it very slightly by sanding it with a Dremel.
I attached the loose end of the spring to this "plunger" by drilling two holes lengthways along the connector's walls and passing the spring wire through both.
Step 11: The Mouth Guard
At this stage, I noticed that when I pushed the plunger all the way into the barrel, the spring tended to protrude from the open end of the barrel and become tangled. To get round this, I narrowed the opening of the barrel slightly by trimming another piece of the 1.25" PVC straight connector and gluing it in place.
Step 12: The Plunger Guide
I now had a spring-loaded plunger that would shoot out of the gun's barrel and bounce around like a jack-in-the-box whenever it was released. While this was a lot of fun to play with, it didn't make for a very convenient reloading mechanism, so I had to find a way to keep the plunger inside the barrel.
I used one of the cartridges I had cut earlier to gauge how far I wanted the plunger to move, then marked a guide on the side of the barrel. I then used a Dremel with a cutting disc attachment to cut out a slot in the barrel.
I drilled another two holes in the side of the plunger (not shown) and pushed a short U-shaped piece of thick wire outwards through them, so that the plunger was held in place within the span of the slot (see the ends of the wire poking out in the fifth image). I later covered these loose ends with a lump of sugru for the sakes of appearance and safety.
Step 13: The Fixed End of the Barrel
Now that I'd made the ejection mechanism for the barrel, I needed to make the fixed end off which it would hinge. A much simpler piece to make, this was just another 1.25" PVC straight connector glued into the short end of the barrel and a 2" PVC cap glued over the rear.
I drilled a hole large enough to insert the vinyl tubing and glued it in place with more Plumbing Goop.
There was still quite a large cavity inside this piece, which was undesirable for maintaining a good head of pressure. I solved this by filling the cavity with plumbing putty and poking a hole through it so that air could still flow, just through a narrower channel.
Step 14: The Hinged Frame
I used plywood to construct a simple frame that would hold the various PVC components of the gun together.
I sketched the pieces on paper first, folding them in half to make sure they were symmetric, then traced them onto wood and cut them out with a jigsaw. I used two small brass hinges here to make the main body of the frame.
Step 15: Mounting the Barrel on the Frame
I hand-cut several small plywood ribs that would fit snugly around the barrel and attach to the frame.
I glued all of these in place with superglue, creating a neatly opening and closing barrel with as little gap as possible between the two parts.
Step 16: Mounting the Pump on the Grip
To attach the bicycle pump to the pressure chamber, I cut a piece of scrap wood into shape and glued it between the two components. As the pump itself grips the inner tube valve quite tightly, this was mostly to provide a bit more rigidity during pumping.
Step 17: Putting It All Together
I cut a few more pieces of plywood to connect the plywood barrel frame to the grip, then glued these in place. After that, I used Plumbing Goop to fix the vinyl tube in place on the open end of the lever valve.
Step 18: Locking the Barrel Closed
To keep the barrel closed tightly, I again used plywood to mount a pair of powerful neodymium magnets above the hinged opening.
I then used sugru to improve the seal where the two parts of the barrel meet and to cover the ends of the wire that were sticking out through the plunger guide.
Finally, I used silicone rescue tape to cover all of possible leakage points in the pressure chamber before leaks could appear.
And, just like that, I had a working Tar and Feather Gun!
Step 19: The Bandolier
To help me out on the battlefield, I made a very simple bandolier out of duct tape.
I started by making one long loop of tape, then backing it with another strip so that neither surface was sticky. I then added twelve little tags of tape, two for each cartridge. Together, two of these tags reach about halfway around a cartridge's circumference.
To fix the cartridges in place, I used strips of masking tape. That way, I could easily rip each one off the bandolier without dislodging any of the others.
Step 20: Filling the Cartridges
- Shaving cream
- Medical waste (a mixture of raspberry Jell-o, chocolate pudding and shredded tortillas)
- Tar and feathers (shaving cream dyed black with food dye and actual feathers)
First, cover one end with a single sheet of toilet paper and tape it in place with a thin strip of duct tape.
Upturn the tube and fill it from the bottom up. If you're using shaving cream, pipe it right down into the bottom using a straw or you'll find that it only fills the top half of the cartridge.
Once it's full, cover the other end with another sheet of toilet paper and tape it up.
For the tar and feathers, I alternated layers of shaving cream and feathers within the cartridge so that the feathers were pushed out by the foam, but not slicked down and blackened by it. I found that it helped to cut up the feathers with scissors so that they didn't get stuck in the barrel.
A note on the fillings
I originally intended this gun to fire water rather than various types of gunk. However, I struggled to find a way of sealing the cartridges tightly enough that they would not leak, but not so tightly that they wouldn't be burst open by the gun's air pressure. I tried using wax paper, aluminum foil, cling film and a few other materials without success. In the end, I realised that using gels, foams and powders is much easier as they can all be sealed with tissue paper without major leakage.
If anyone comes up with a good method for sealing cartridges of water, please let me know. Better yet, upload a video!
Step 21: Loading and Firing
- Make sure the ball valve is closed.
- Tear a cartridge off from your bandolier.
- Open the breech.
- Load the cartridge into the gun.
- Close the breech.
- Pump up the pressure.
- Aim and fire.
- Snap open the breech and eject the empty cartridge.
Here's the demo video again:
I'd like to give a huge thank you to SHIFT! for volunteering to be the victim of a merciless gunge execution. He took it all with immense grace and good humor that went far beyond the call of duty. Good man.
Thanks also to jessyratfink, randofo and StumpChunkman for assisting with shooting the video!