Introduction: Bungee Bazooka
Finalist in the
Make It Stick Contest 2
This is essentially a shoulder-mounted sling shot that shoots large homemade Nerf-type darts.
It can also be used to launch other things like tennis balls, golf balls, tomatoes, apples, and even raw eggs.
This is something I had been working on in the back of my mind for over a year, trying to figure out all the details. For some reason the challenge of making a homemade, self-contained, bungee-powered, multi-ammo launcher was incredibly intriguing to me. I had never seen anything like it, and thought it would make a great experimental project.
The finished product is by no means high-powered like a compressed air- or combustion-fueled cannon, but it still packs a decent punch for what it is, and has turned out to be extremely fun to play with.
Please note that most of the information and details for this project are contained in the photos in the form of notes (the little yellow boxes). If you plan to make one of these, be sure to study all the photos and their notes carefully.
Thanks for looking!
Step 1: Video!
Step 2: Tools and Materials
If you have access to a table saw, band saw, and drill press, it will simplify the making of some of the key wooden parts for this project. At minimum, you can get by with a circular saw, jigsaw, hand-held drill, a Dremel-type tool, and a few other basic hand tools. Specific tools are mentioned in the particular steps where they're needed.
Here is a finalized list of what I used to complete my Bungee Bazooka (some of which are shown in the photos above):
- 5 feet of 4" PVC sewer pipe (I've seen both green and white varieties. The wall on mine is 3/16" thick.)
- Two pulleys - for rope sizes up to 3/8". These must be the kind with a removable center pin, so you can take them apart and only use the actual pulley wheel. (Mine are made for ceiling/wall applications, and were purchased at an Ace Hardware store. The center hole in pulley wheel was 5/16".)
- Two 5/16", 3" long bolts with a section of smooth shaft on which the pulley wheels will spin.
- Handful of washers to match pulley wheel bolts. (I ended up using 14.)
- Two locking nuts to match pulley wheel bolts.
- Handful of key rings. Heavier-duty variety, four 1" size for bungee bands, and one 1 1/4" size for each dart. I got extras to replace ones that may break, and for making the sling for shooting non-dart projectiles (see steps 16 & 17). I got my keyrings at an office supply store.
- Two 3/16" quick links. Mine said "615 lbs. max load."
- Two 1/4" eyebolts, 2 1/2" long, with two washers and two locking nuts to match.
- One 3/16", 48" long metal rod (ended up only using about half of it.)
- Nine 1/4" carriage bolts, 2" long with matching washers and locking nuts. (Most were trimmed off with a Dremel once they were bolted in place. I bought them all long on purpose just to ensure they would all fit in their various applications.)
- About twenty 1-inch "pancake head" screws. I bought these at Ace Hardware. The screw head is thin enough that they can be used in the inside of the PVC pipe without them sticking up and being in the way. See the photo of them above.
- Two additional washers, one with a 3/16" inside diameter, and one with a 1/4" inside diameter
- Two U bolts designed for 1" pipe
- 8 feet of therapy resistance tubing. I had some blue Thera-Band that I used. You can get it from most medical supply stores, like this one online. I actually got mine from welding supply store.
- A small amount of hardwood (I used birch), and a small amount of plywood (I used some 1/2" and some 3/4")
- A small amount of craft foam
- Various adhesives: wood glue, original gorilla glue, epoxy, hot glue
- Foam tubes. I got mine at a thrift store, and I'm not sure what their original purpose was. The outside diameter is 1 3/4", and the inside diameter is 5/8". Smaller pool noodles would work great, as would foam insulation for pipes.
- Small amounts of webbing. I used some 1" and some 3/4". You can get this out outdoor stores, craft stores, and most hardware stores.
- Craft foam for fins
- Stiff wire, like hanger wire
- Tennis balls
- Some heavy fabric (for the sling)
Step 3: Main Tube Layout & Access Holes
Guidelines were laid out on the PVC tube for where I was going to cut the access holes in the top, and where I was going to attach the handles and other components to create the bazooka.
Begin by getting the circumference of the tube by wrapping a sheet of paper around it and marking where the paper overlaps.
Measure from the overlapped edge to the mark you made. This is the circumference. On the paper, lay out and make marks as needed for the location of where you will want guidelines on the tube, re-wrap the paper onto the tube, and transfer the marks onto the tube.
I placed four guidelines equally spaced on the tube, dividing it into quarters lengthwise with a top and bottom line, and a left and right line. I then added guidelines for the placement of the front handles, as well as the side cuts of the access holes.
A hole saw was used to cut out the corners of the access holes, and a jigsaw was used to make the straight cuts. These openings were sanded gently to take away the sharp edges.
Take a look at photo 3 in its original size (click on the box in the upper left corner) to see where all my marks were made to help layout my tube. If the circumference of your tube is close to 336mm as mine was, you can copy my measurements directly from that photo. If not, you will have to do some easy math to divide the circumference of your tube into equally spaced quarters, place marks on your paper, and create guidelines on your tube accordingly.
Step 4: Trigger Handle Build-up
The trigger handle was made by laminating three layers of 1/2" plywood. The center layer is laid out and cut to allow room for the trigger and accompanying parts to be installed inside of it later on.
The shape of this trigger handle/trigger mechanism housing went through various modifications throughout the project, as you may notice in some of the photos. The main thing that is needed is a spot for the trigger with room for it to slide back about 3/4", and a channel along the top for the metal rod to be housed that connects the actual trigger to the rear mechanism (see step 7 for lots of photos of this).
Be sure to examine all the photos and read the photo notes for dimensions and additional information.
Step 5: Ammo Ring Holding Pin
This piece was made from solid birch, with a short section of metal rod placed through the center of it. The metal rod is just a hair over the length of the diameter of the inside of the tube, and is place through a hole drilled through the block all the way flush to the bottom of the block of wood. It should protrude 1/2" over the top of this block of wood. The backside of this block should be sloped enough to accommodate the two sloped pins coming out of the shuttle piece shown in the next step.
The block was bolted in place with carriage bolts with the back edge exactly 3 1/2" from the back end of the PVC pipe.
All components made from hardwood are made from 1" stock, except for the actual trigger piece (more info on that in step 7).
Step 6: Ammo Ring Release Shuttle
This piece is made from solid birch. It slides backward when the trigger is pulled, and the two little rods lift the keyring off of the holding pin releasing the object to be fired. The release shuttle block is 2" inches long, 1 1/2" tall, and 1" wide.
There is slot cut into bottom of the PVC that is 2 1/2" long and just over 1/4" wide that begins immediately behind the block attached in the previous step, and extends toward the back of the pipe.
This ring release shuttle piece is bolted in place with a carriage bolt in the back and a smaller guide screw in the front. The bolt and screw are kept just loose enough so that the shuttle can slide freely in a long the slot made in the bottom of the PVC when the trigger is pulled.
Step 7: Trigger Mechanism
The trigger mechanism is completely housed in the trigger handle build-up, but not actually attached to it.
The trigger handle build-up is bolted to the PVC with a carriage bolt at the front and back. Please examine the photos for more detailed information.
Step 8: Front Handles
The front handles are made from a laminate of 1/2" plywood and 3/4" plywood. This was just the thickness that felt nicest.
These were bolted in place with carriage bolts.
Step 9: Pulley System Front End Assembly
The pulley front end assemblies are made from birch.
Various pieces were cut and pieced together with screws and glue to create a secure way to attach the pulleys to the front of the bazooka. These parts are crucial, and the pulleys must be placed in precisely the right spot for the bungee cord to travel as needed both inside and outside the bazooka. See photo notes for details.
Step 10: Pulley System Front End Mounting to Tube
The completed pulley brackets were screwed to the front end of the bazooka with pancake head screws. Epoxy was added prior to screwing them in place to add more strength. I'm not sure how well epoxy holds up on PVC, but I'm guessing not so well. The screws probably suffice by themselves.
If you look inside the front end of the bazooka in some of the photos, you can see a lot of extra holes . . these reveal how many tries it took till I got the pulley brackets attached precisely where I wanted them. (Turns out this was not as easy as screwing two flat items together, that's for sure!)
I didn't have a stubby-enough screw driver to get into the inside of the pipe to put all these screws in place, so I had to make my own. You can see it in the last two photos above. It is made from a plug of wood created by drilling out a hole with a hole saw. A phillip's driver bit was glued into a 1/4" hole with gorilla glue. This super mini screwdriver worked really well, and was the MVT of this project.
Step 11: Pulley System Back End
The pulley system back end is made from two pieces of 3/4" plywood that were glued together. These were laid out so the back piece inside diameter was equal to the inside diameter of the tube, and the inside diameter of the front piece was equal to the outer diameter of the tube. This created a lip so the tube butted right up against the back piece, to make it that much more secure.
This was epoxied and screwed in place with pancake head screws. Eye bolts were added lined up with the left and right tube guidelines, to which the bungee cords attach with quick links.
Step 12: Bungee Tubing Bands
I ended up using two 4-foot sections of blue thera-band for my bungee tubes. I experimented with bands created with the same length of amber surgical tubing, and with other lengths of both types of tubing, but concluded that the 4-foot blue tube worked the best.
Each end of tubing was wrapped over a keyring, and taped tightly in place with filament tape.
Step 13: Bungee Kickback Deflecting Loops
Without these, and the side tubes shown in the next step, the bungee cords would kick back and smack the shooter in the face.
These U bolts act as an initial deflection that force the bungee tubes to retract back parallel to the main tube itself, rather than whip wildly out to the sides.
Step 14: Bungee Kickback Deflecting Side Tubes
These side tubes keep the tubing from whipping all the way back and smacking the shooter in the face. They are made from 28-inch long pieces of 1" PVC.
Wooden brackets were made from plywood. The PVC is glued to the plywood brackets, and the brackets are screwed to the main tube.
Step 15: Wood Finish
All wood surfaces were finished with a few coats of brush-on polyurethane.
Step 16: Dart
The darts are basically a foam tube with a tennis ball on the end. The wires that stick out the sides attach to the front key rings on the resistance tubing on the bazooka, and transfer the pull of the tubes back down the webbing to the back key ring, which is attached to the holding pin at the back end of the bazooka. See photo notes for details.
Step 17: Sling for Alternate Ammo
The sling for alternate ammo is made from a piece of heavy canvas, some webbing, and some hand-bent wire hooks.
Well, I think that's about it. Thanks again for looking, and let me know what you think!
Step 18: Extra Photos
Here are a few more photos.
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