Bottle Rocket Pistol

Pocket-sized water bottle launcher.

There are plenty of bottle rocket plans out there, but I hadn't seen anyone use a quick release coupler as a launch mechanism before. Plus, all other launchers are so large, it seemed to me all you need is the coupler and a valve. I decided to make two so me and the girl can go to the park and have a shootout (after all, the bike pump is hers).

You will need:

A set of quick-release garden hose couplers (I had this idea while in an Ace hardware store, and as it happens, this brand works better than the Lowe's version which won't hold under pressure.)

Rubber tire valves (auto parts store)

4" of 1/2" PVC (Lowe's Depot)

1/2" PVC cap (ditto)

1/2" PVC to 3/4" NPT elbow (NPT= National Pipe Thread) (ditto)

1-2 liter bottle (I like seltzer.)

(not shown) extra garden hose gaskets

Supplies!

PVC cleaner and cement (Lowe's Depot)

Teflon pipe tape (I used the pink, which is thicker.) (ditto)

Tools

Saw (pretty much anything will cut PVC)

1/2" drill bit and something to make it spin

Channelock pliers

The point of this was to make a compact launcher, so cut just a little more than needed for the fittings.

Drill a 1/2" hole in the cap. I carved a flat on the cap to thin the PVC so the rubber tire valve will seat properly.

Stick the valve through the cap from the inside, grab it with pliers, and pull. A bit of dishwashing soap will help.

For those who are new to joining PVC, I'll explain the whole process. (Those who know, well, you aren't reading through each step, are you?)

If you've ever wanted to weld in your kitchen, here's your chance! PVC is joined by solvent welding. This just means that you put a goop on the joint that partially dissolves the plastic, jam it together, give it a quarter twist to ensure complete contact, then let the solvent evaporate and it's all permanently joined.

The cleaner is basically acetone to remove any oil contamination before you put the "cement" on.

Allow the joints to set up several hours before pressurizing the weapon.

So, the elbow is threaded 3/4" NPT (National Pipe Thread) the couplers are threaded GHT (Garden Hose Thread) (really), and the bottle is threaded WHK (Who the Hell Knows?), how are we going to get connections on all these to withstand 50+psi? Teflon pipe tape and brute force! (plus those extra garden hose gaskets).

The pink teflon tape is thicker than the white stuff, and we're going to need all the help we can get here. Put several wraps around the female coupler threads (clockwise!) and crank it into the elbow with channelock pliers. The incompatible threads will kinda mush together.

The thread on the bottle is further from matching with the GHT on the male coupler, so in addition to the Teflon tape, put an extra garden hose gasket in the coupler before threading it on (a total of two). As you crank it together, you will see the plastic stress a little. Get it tight, but don't bust the coupler.

Fill 1/2 to 1/3 with water, attach bike pump, pressurize to 40-50 psi, pull back the collar on the quick release to launch. (Extra points to those who can tell me who Gridley was.)

Thanks for the photos, Alice!