Handheld Rocket Launcher!!

Back when I was in High School (early 90s) boredom inspired me to create a handheld rocket launcher out of miscellaneous parts I found in my dad's garage. It worked spectacularly.... ONCE. After that I never got it operational again, and it eventually found its way back into the pile of parts. Recently I have been feeling exceedingly nostalgic and for the past few years I've felt the urge to create a new & improved version. So I now proudly present to you, The Handheld Rocket Launcher Mk II.

 

PLEASE NOTE: The legality of this item falls into a bit of a grey zone (similar to potato cannons) The state of Arizona is especially interesting since Model Rockets are legal, but any type of firework or sparkler is not. DO NOT aim this at ANY living thing!! USE COMMON SENSE and SAFETY if you choose to build/use one of these. It is for educational and entertainment only, as it has no practical value at all. To put it bluntly, don't be an idiot with this thing. I'm not responsible for any accidents you may incur.

The Launcher is powered by a 9 volt battery. The power has an illuminated safety switch and will not fire unless the switch is "armed." Pull the trigger and a current is passed through the copper barrel as well as a steel washer at the base of the barrel. If a properly constructed "Missile" is loaded at this time, it will complete the circuit, lighting the igniter and the Missile will be launched from the barrel.

1" dia x 24" copper pipe

1" threaded copper adapter
1" threaded pvc cap

piece of leather (optional)

wood, 2 1/2" x 24" x 1/4"

 

Wood screws #4 x 5/8"

#12 x 2" Machine bolt w/ nut (not shown)

18 Gauge speaker wire (I also used other smaller wires as well)

Insulated ring terminal (2 different sizes)

2) fender washers 1/8"X3/4"

Momentary contact Push button

Illuminated toggle switch

9volt clip

1" insulated clamps

Steel Rivet 1/8" dia x 1/2" grip

Drill

Jigsaw

Miscellaneous drill bits (including 1/2" & 1") (not shown)

Screwdriver

Dremel (Required for virtually EVERY project!)

Needle nose pliers

Wire Strippers

Torch

Rivet Tool (what's the proper name for this??)

Soldering Iron (optional but recommended)

Ohmmeter (optional but recommended)

Hot glue gun (optional but recommended)

Solder the copper fitting to the pipe.

It's recommend to coat the end of the pipe and the inside of the fitting with Flux prior to soldering. It helps the solder flow into the joint.

Using the torch heat the fitting, not the pipe itself.

Once hot enough the solder will melt and be sucked into the joint.

Wipe down with a rag and let cool.

Using the supplied PDF layout, mark out the pieces onto the wood as shown.

Start by cutting the strip with B, C, & D off. I used a jigsaw, but a table saw would have been much better for this step.

Cut out pieces A & B next.

To create a perfect curved end to B & C, clamp them to a working surface, and then drill out the circle using a 1" bit.

Do not drill the holes for the buttons yet!

Mark out the locations of the button holes and ends on the wood pieces. You will need these lines to locate the holes for the screws.

 

Be sure to stagger the holes in such a way that they don't enter any of the button holes, and they won't hit each other. I went a bit overboard with the holes. You'll see in photos of the final product I didn't need this many. Use your own discretion on this step.

 

Since the heads of the screws have a taper on them, we'll need to countersink the holes a bit. If we don't there is a good chance the screws will split the wood. I used a small boring bit on the dremel to create the countersinks.  

 

Assemble the handle. Be sure to use pilot holes for the screws so that the wood does not split! 

Drill the button holes using a 1/2" bit, keeping them as centered as possible. 

I decided on a whim to stain the handle. Definitely not required but adds to the "cool factor" ( an important quality in all of my instructables)

For me, this was the most difficult part of the build. Take your time on this step.

Take the two 1" clamps, and if yours are insulated, remove the insulation.   Bend them so both legs are an equal lengths. 

Next, position them over the barrel and onto the handle in such a way that the bracket will hold the handle flush. Drill a 7/32" hole through the handle. It will have to be located so as to miss both switches. On my prototype it was a little bit loose, and I had to resort to using the hot glue gun to keep the handle from slipping around on the barrel.

Open up the handle and install the electronics per the attached schematic.

Make sure the threads on your buttons are long enough to penetrate the wood. I almost had to countersink my trigger!

When you have it put together, pull the speaker wire almost all of the way apart. Cut the positive lead to just a few inches long and attach a ring terminal large enough to go over the #12 bolt. The negative lead should be about 16" long

Once wired up, it is recommended you test the system using your ohmmeter. Set it to 10V DC test and connect it to the end terminals. You need to verify there is ONLY a charge when both the safety switch is on AND the trigger is pushed. This is a very important step. You do NOT want this thing firing unexpectedly.   The safety switch should illuminate when it's "armed".

To eliminate the possibility of a short, I filled the button terminals with hot glue. Next, scuff up the top of the battery clip and using wood glue, attach it to piece "D". I used cellophane tape to secure it in place while the glue dried. 

I chose to "port" the barrel for a couple of reasons. First it (hypothetically) will reduce turbulence for the missile by allowing the gases to escape from the sides of the barrel instead of competing for room at the mouth of the barrel. Other than that, it looks rather cool, and I'm anticipating short flames/smoke shooting from them. ("cool factor")

 

Begin by printing the attached template and taping it to the end of the barrel. Start each port with an 1/8" hole, and then enlarge to a 3/16" bit. Do not apply too much pressure with the drill or you could deform the barrel.

 

After the holes are drilled take your dremel or a file, and spend the time to make the inside of the barrel smooth again. If it's not smooth enough the fins of the missile might get caught and it wouldn't be pretty.

With the handle reassembled cut a small notch in the arch above the safety switch with your dremel. 

Lay the wires in this notch and then attach the handle to the barrel with your 1" clamps and bolt. Slip the positive lead ring terminal over the bolt. Wrap the negative lead around the barrel a few times and cut to the desired length. Attach the smaller ring terminal to the negative lead.

Drill a 1/8" hole in the cap. Widen it slightly.

Starting from the outside, the rivet should pass through the ring terminal, a washer, a piece of cardstock (more on that in a second), through the cap, and then secure the second washer inside the cap.

 

The cardstock was a good idea that didn't work well at all. I wanted the ring terminal to be able to spin on the rivet. I had planned on ripping the cardstock out but the rivet gripped too hard and I never got it out. Perhaps if I had put the cardstock on the other side of the washer it would have worked better.

 

After this step is complete get out your ohmmeter again. Set it to 10V DC and touch the positive probe to the barrel and the negative to the inside washer on the PVC cap. Verify that you are getting 9 volts when the trigger is pulled.

Pack of rocket engines (with igniters and plugs)

Printed templates from step 6

Thin conductive tying wire.

Any standard size rocket engine will work. I had some B4-4s laying around that I used. The ideal rocket would be a C engine used for glider rockets. These have no ejection charge, so they have a better power to weight ratio.

 

Cut out the fins and nosecone templates. Bend the fins in a series of peaks and valleys as shown. Wrap and glue around the TOP of the rocket engine. These cannot go at the bottom of the rocket or it will not sit properly inside the PVC cap. Next, cut out and glue the nosecones on as shown.

 

Install the igniter as you normally would using the plastic plug. Remove the tape holding the leads together. Bend one lead up the side of the rocket. Twist the other lead into a coil-spring. These leads MUST NOT TOUCH or it will not fire. Cut a piece of tying wire and loop it against the straight lead, securing in place with a small piece of tape. This tying wire must bend outward as shown to ensure it makes contact with the copper barrel.

It works, but the rockets weren't nearly as stable as I had hoped.  Possible solutions? Perhaps using different strength engines would help. Or creating a longer missile by taping a used engine to the front of a fresh engine?   Weighting the nosecone? 

 

The escaping gases actually stung my hand a little bit. (but didn't singe any hairs) 

 

The rocket has to be cleaned out at least a little between shots. If there is too much residue in the barrel the ignition wires can't pick up the current.

 

Have fun and be sure to let me know any improvement ideas you have!

 

(If you enjoyed this instructable please rate it, and be sure to check out my other projects!)