PROJECTS: AIR ROCKET
5. MAKE THE AIR HOSE
AND TEST THE LAUNCH SYSTEM
5a. Now we’re going to assemble and attach the air hose to the launcher. First,
strip the rubber off the tire valve. You can use fine sandpaper to clean off the
valve so it’s shiny.
5b. Slip the tiny hose clamp over the hose and insert the tire valve into the
hose. Push it in as far as you can. Tighten the hose clamp over the tube and
valve using a socket or screwdriver. This connection was the Achilles’ heel in
my prototype launcher. Granted, it was exciting to have the hose explode off at
75psi, hissing wildly like a snake, but, for the sake of reliability, I’ve strengthened
it by using the mini hose clamps.
Slip the second mini hose clamp over the other end of the hose, and push the
hose end onto the 6" hose barb. Tighten the clamp over the hose and barb.
If you find the clamp too big and you’re not able to get it really tight, wrap the
barb in rubber from a bike inner tube and then tighten the clamp over that.
5c. Attach the bicycle pump to the tire valve and pressurize the system to about 75psi. Keep an eye on the
gauge and listen for any hissing. The pressure should stay at 75psi. If you find leaks, fix them and try again.
Release the pressure by pressing the launch button (with the battery connected). Be careful when you
do this — wear eye protection and stand clear of the pressure chamber.
If the pressure doesn't release when you press the button, tighten down the solenoid (the black thing with
the wires coming out) on the sprinkler valve. You may also need a larger battery (one with more amps) to
trigger the solenoid under pressure.
If you’re still having problems with your electrical system, most valves have a manual trigger you can
flip to release the pressure. If you’re up this close to the valve you may want hearing protection as well.
Be very careful that your head is away from the launch tube.
6. BUILD THE ROCKET ASSEMBLY STAND
Mark the center of a 5½" scrap of 2× 6
lumber. Drill a q" hole 1" deep in the
center. This is where a drill press is
really handy. Then twist a 13" length of
½" PVC pipe into the hole. Add masking
tape to the base of the pipe, if needed,
to get a snug fit.
110 Make: Volume 15