Introduction: Pump-Action Rocket Gun
This is an awesome gun. It is very fun and not that difficult to make. It is also very cheap. The entire thing including a bunch of ammo could easily be made for ~$20, or much less if you already have a lot of the stuff ( you probably do). I spent about $15 but a lot of what I spent it on is extra and can be used on other things. I broke this instructable down into two parts: rockets and launcher, because it involves a lot of steps ( I didn't divide it into two i'bles though, just this one).
-This is in the Krylon contest because it's painted with Krylon.
-This is in the "launch it" contest because it launches rockets.
-This is in the Celestron space challenge because it uses rocket propulsion. And it would work in space I think.
Quote from ATF relating to the legality of this project:
"...As defined in 26 USC subsection 5845(f) (2) the term destructive device includes any type of weapon by whatever name known which will, or which may readily be converted to, expel a projectile by the action of an explosive or other propellent, the barrel or barrels of which have a bore of more than one-half inch in diameter, except a shotgun or shotgun shell... The term 'destructive device' shall not include any device which is neither designed nor redesigned for use as a weapon ; any device, although originally designed for use as a weapon, which is redesigned for use as a signaling, pyrotechnic , line throwing, safety, or similar device; surplus ordnance sold, loaned, or given by the Secretary of the Army pursuant to the provisions of section 4684(2), 4685, or 4686 of title 10 of the USC; or any other device which the Secretary of the Treasury or his delegate finds is not likely to be used as a weapon, or is an antique or is a rifle which the owner intends to use solely for sporting purposes. ..."
This quote is from: http://www.launchpotatoes.com/index.php?act=viewDoc&docId=7
I think that means this is legal as long as it is not used as a weapon.
Step 2: The Rockets
Gather all the parts you need:
-1/2" PVC tube
-Dowel that is slightly larger in diameter than the PVC tube
-Empty pop cans or aluminum flashing
-Ingredients for rocket fuel
-Optionally Iron Oxide or Aluminum/Magnesium powder
-Electric match (see https://www.instructables.com/id/Fireworks-Igniter/ )
-Black powder ( https://www.instructables.com/id/Gunpowder-1/ ),
-Impact fuses ( https://www.instructables.com/id/Impact-FuseExploding-Arrow/ )
-Electric cooker thing
-Pan or bowl that can be used on stove-top
-OPTIONAL: bench grinder, lathe, dremmel/small grinder cutter driller.
Step 3: Motor Tubes
-Cut a piece of 1/2" PVC tube 3.5" long. Use sandpaper to get at least one end flat and smooth. This will be the motor tube. About 1/4" to 1/2" in from both ends of the tube, grind a groove into the inside of the tube all the way around. That helps lock the nozzle and end cap in place.
-Cut 2 pieces of dowel, one that is at least as long as the motor tube and another that is about 1.5" long. Grind one end of each of these into a cone shape and smooth the surface with sand paper. Then grind the surface of the long one until it fits in the motor tube. These will form the nozzle mold.
-Mix up some of the water putty and put it in the smooth end of the tube to a depth of about 3/4". Then put the Nozzle mold pieces into either side of the glob of putty and let it harden. The mold pieces will release more easily if you put some oil or grease on them before they touch the putty.
-Once the water putty has hardened, drill a 1/8" hole through the center to finish the nozzle. Set it aside to harden completely.
Step 4: Make the Propellant
-Cut a 2 inch long piece of the 1/2" PVC tube. This will be the mold for the propellant grain.
-Weigh out your ingredients. There are a lot of different recipes that people have come up with but I chose this one to use on this because it's simple and proven to work.
-5 parts potassium nitrate
-2.5 parts sucrose (regular sugar)
-1 part corn syrup
-Then add to that 0.5% to 1% by weight of rust if you chose. It makes it burn faster.
I made a 68 gram batch then added ~0.4 grams of rust.
-Put all the ingredients into your cooking bowl and add enough water to make it into slop. Go outside.
-Boil the mixture till it starts to become a play dough-like glob. Then turn the heat way down and keep stirring it and moving it around. There is some possibility of it igniting at this point if you have the heat on too high and don't stir it.
-Every few minutes, take a small piece and smash it flat between your fingers. Let it cool completely, then bend it and see if it snaps or just bends. When it snaps you know that enough water has been removed from the mixture. Burn a small sample to make sure it is good before you invest time in the next steps.
-Take a ~9 or 10 gram chunk of the hot propellant and form it around a 1/4" metal rod like a screw driver or drill bit. Then push it into the mold tube and pack it in with a stick (with the 1/4" rod still in it). It helps to put some vegetable oil in the mold and on the rod before you do that so you can get the propellant back out.
-Once it cools, pull out the quarter inch rod and hammer the propellant grain out of the mold tube. Then store it in an air tight container.
Step 5: Load the Fuel and Igniter
-Chose one of your fuel grains and push it into the motor tube. Make sure it goes all the way down.
-Put an electric match ( https://www.instructables.com/id/Fireworks-Igniter/ ) into the motor tube above the fuel grain and centered above the hole. Use fine enamel-coated copper wire instead of the thick stuff shown in that instructable.
-Cut out a cardboard circle the size of the inside of the tube. Being careful to not smash the match, push the cardboard circle into the motor tube and hot glue it into place. If there is more than 1/2 inch or so left above the cardboard, fill it with hot glue until there is only 1/2 inch left at the top.
-Fill the remaining section of motor tube with water putty. If you want this rocket to explode when it hits something, stick an impact fuse ( https://www.instructables.com/id/Impact-FuseExploding-Arrow/ ) into the putty before it hardens.
-Pour a small amount (5 to 10 milligrams) of black powder into the motor through the nozzle to help with ignition. Put a small piece of masking tape over the nozzle hole to protect the fuel from outside air since it is hygroscopic.
Step 6: Finish the Rocket
-Cut the fins out of the thin metal sides of aluminum cans. Look at the picture for shape and size. You will need 3 per rocket.
-Bend a curve into it parallel to the long side so it will lay almost flat against the rocket when laid on it like in the 4th picture.
-Lay each fin on the rocket so the small end is lined up with the back (nozzle end) edge of the rocket. Tape along the angled edge. Then wrap tape all the way around just above the fins so the fins won't peel off from the front. Cut the small section of tape at the front edge of each fin that is holding it from opening.
-Air blowing from the front of the rocket should make the fins open and the fins will give the rocket spin and drag in the back to keep it flying straight.
-Cut a 1.25 to 1.5 inch circle out of cardboard. Cut it and glue it to form a cone whose base is as big around as the rocket. Glue it onto the front of the rocket. If you put in an impact fuse you can fill it with black powder if you want. If you use black powder don't use the traditional 75:15:10 recipe because it burns slow and leaves KNO3 residue. Use a 70:20:10 mix. Be careful to not smash or set off the impact fuse when pushing it through the black powder in the cone.
Step 7: The Launcher
-1" PVC tube
-Scrap cardboard and cardboard tubes
-Thin aluminum or copper (just a small amount, a couple square inches)
-Push button switch
-9v battery and connector
-The same dowel from the last part
-3 smallish magnets
-Hot glue gun
-Dremmel tool (or a file and patience)
-Scissors and knife
Step 8: Barrel and Reload Mechanism
-Cut a 22.5 inch long piece of the 1" PVC tube. Put a mark 5 inches in from one end and another mark 4.5 inches beyond that. Half of the PVC tube should be cut out in the area between these marks. Smooth out the edges around the opening.
-Cut an 11 inch piece of dowel and a 1/2 inch piece of the 1" PVC tube. Glue the 1/2 inch long ring to one end of the dowel. Try to keep the dowel centered in the ring as the glue hardens. Glue a ceramic magnet that is about the same size as the dowel to the other end of the dowel.
-Cut two 6 inch pieces of a cardboard tube that fits over the 1" PVC tube. Lay them parallel to each other and glue them together. Glue cardboard caps over the ends of one of them.
-Cut two 18 inch pieces of 1/16" steel wire and straighten them out. Slide the dowel into the 1" PVC tube from the back (end closest to the opening cut in the side) so that the magnet end of it is just behind the opening. Slide the cardboard tubes that are glued together onto the front of the PVC tube with the capped one on the side of the tube with the opening cut in it. Push them back to just in front of the opening. Glue one end of one of the steel wire onto the the cardbard tube that is slid over the PVC pipe and glue the other end to the PVC ring at the back of the dowel. Flip the whole thing over and glue the other wire on the other side.
Step 9: Electronics
-Measure 3 inches in front of the opening in the bottom of the PVC and put a mark. Put another mark 1 inch beyond that.
-Cut two 1 inch by 1/2 inch rectangles of aluminum flashing or other thin aluminum, then trim them into a roughly paraboloid shape. These will be the electrical contacts that touch the foil on the rockets. Bend the tip of the curved end a little so it wont snag the rockets.
-Drill/cut slots just behind the marks that the aluminum contacts can fit in. Using a dremmel with a drill bit, carve grooves iinto the surface of the tube as shown in the 3rd picture for wires to lay in so they don't prevent the front cardboard tube handle thing from sliding.
-Cut wires in the shape of the grooves. They should extend back to behind the opening that was cut into the tube when laid in the grooves.
-Hot glue the aluminum contacts into the tube so they slant toward the front and stick out on the inside about 1/4 inch. They should both stick out as close to the same amount as possible on the inside.
-Put the wires in their grooves. Stick the ends under the parts of the aluminum contacts that are showing, press the aluminum down and wrap about two layers of masking tape over each joint.
-After you get the wires on, make a 1/3 cylinder out of two layers of cardboard and glue it on at the back of the travel of the sliding cardboard tubes as a stopper.
-Solder the switch and battery to the wires as shown on the 8th picture.
-Cut a 5 inch piece of cardboard tube at about 15 degrees off of perpendicular. This will be the handle.
-Make a hole 1/2 inch or so down from one end of the tube on the side of the acute angle and glue the switch into it.
Step 10: Magazine
This will be a non-removable box magazine with a 3 to 5 round capacity (depending on how stiff the springs are and whether one rocket is stored in the barrel). It is reloaded through a detachable lid at the bottom.
-Special materials you will need are springs and velcro.
-Draw the outline shown in the first picture onto a flat piece of corrugated cardboard. The cutout along the outside edges. Score the first layer of the cardboard with a knife along the inside lines.
-Fold it along the scored lines and glue the 1/2 inch wide tab to the inside of the part that it meets up with. Put hot glue along the corners (on the outside) where you scraped through the paper to strengthen it.
-Do the same thing to make the removable cap shown in pictures 3 and 4. Make sure it fits over the bottom of the main part of the magazine you just made.
-Get two springs that are about 1/2" to 3/4" in diameter and 6 inches long. Mine are two halves of one spring from a broken airsoft gun. The springs can be stretched if they are a little too short.
-Glue the two springs into the bottom of the magazine's cap about 1/4 of the way in from each end. Glue a cardboard rectangle that is about 1/2" by 4" onto the top of the springs.
-Hot glue a 3 inch long strip of hook-type velcro on the middle of each side of the main box of the magazine. Make sure both velcro strips are above the part that the cap will cover. Glue an 8 inch long strip of loop-type velcro across the middle of the outside of the cap. Then glue a strip of cardboard over the bottom of the cap to stiffen it.
Step 11: Finnish the Launcher
-Cut two 4.5 inch pieces of steel wire and bend them like shown in the picture. Glue them on like in the next picture and glue strong magnets onto them. This will make it so the slider mechanism doesn't open without being pushed.
-Glue a small smooth piece of plastic at the bottom of the back of the opening in the PVC tube to keep the dowel from sagging and catching on the front edge of the opening.
-Glue on the handle and a trigger guard. Glue a strip of strong cardboard so it hangs down in front of the push button switch as a trigger. This will make the trigger easier for your finger to find and make it less touchy by requiring a little travel of the trigger before the switch is closed.
-Make a cardboard cover to go over the whole thing and protect the mechanism. It should be 29 inches long. It is half of a cardboard tube about 2 inches wide with some flat cardboard strips that are 1.25 inches wide glued to the side. On the inside there are some ribs which are carefully shaped to match where they will mount. Do not put any ribs where the front cardboard tubes are sliding or in the back where the dowel moves through.
-Glue on the magazine. It should completely cover the opening that was cut into the bottom of the 1" PVC tube.
-Paint it whatever color you want. I used Krylon flat black.