Introduction: Spring-Powered Crutch Rifle

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About: I make stuff, or at least I try. When I'm am not making things, I enjoy learning what I can in the areas of history, religion, electronics, and 3D printing.

Hi all.

I've had this old aluminum crutch lying around in my garage for months, and seeing that I wasn't planning on breaking my leg anytime soon, I decided to re-purpose it. And what better way to re-purpose a crutch than into a projectile propelling weapon of war?

Yes, this spring-powered rifle can actually propel physical objects through the air. For projectiles, you can use used pens, pencils, Nerf darts, sticks...and countless other objects.

Step 1: What You'll Need

Tools You'll Need:

- Pliers (you may also want some needle-nose pliers and a pair of channel locks)

- Powered Screwdriver

- Small Drill Bit (I used a 3/32 in)

- Hack Saw

Materials You'll Need:

- Aluminum Crutch

- Zip Ties

- Nickle (or similarly sized coin)

- Duct Tape

- Deadbolt Strike (or similar metal bracket)

- Drapery Curtain Rod Bracket (or similar metal bracket)

- A few Screws

- One small Bolt with Washer and Nut

- Compression Spring (the larger the spring the more powerful the rifle)

- some short pieces of PVC Pipe

- Two Eye Screws

- A small length of wire or thin cable

Step 2: Disassemble the Crutch

Before you start building anything, you must first take apart the aluminum crutch. Push in the push buttons and slide the adjustable lower part of the crutch completely out of the larger piece. Then pull off plastic end cap. Keep these pieces handy, we will be using them later.

Step 3: Modifying the Barrel

The middle tube of the crutch, the one with the holes in it, will be the barrel and firing chamber of the rifle. Some of the holes will need to be blocked off to allow the firing pin, which will have a push button lock, to slide from the first hole to the last hole smoothly. Loop some zip ties around the barrel; centering them on the holes they are covering. Cover all the holes except the one nearest the front of the barrel and the two nearest the end of the barrel. Pull the ties nice and tight so that the push button with not be able to catch on these holes as it slides by. Ideally, you should use one large zip tie for every hole; however, I only had short ones on hand so I used two per hole. Trim the zip ties after they are tightened sufficiently.

Step 4: Preparing the Firing Chamber

By popping off the plug at the rear end of the barrel, you can see that there is a bolt inside this end of the tube. The firing spring will compress against this when cocking the rifle. I wanted some sort of flat surface to cover the bolt so that the firing spring wouldn't be slipping around on it. A nickel, as you can see, is just a little too small to fit snugly in the barrel, so I enlarged it a bit with some duct tape. Cut a small strip of tape and wind it around the coin. Then fold the edges over against the coin's faces. After adding three stripes of duct tape, the nickel should fit nicely into the barrel. You can use the small adjustable part of the crutch that you removed earlier to push the coin down the barrel until it is sitting above the bolt. Replace the end plug when finished.

Step 5: Assembling the Firing Mechanism

The Firing Mechanism is made out of two metal brackets. I used this deadbolt strike and drapery curtain rod bracket because I had them on hand, but you could make this simple mechanism with similar metal brackets. First, using some pliers bend the deadbolt strike at both ends until they form right angles with the middle part. Then proceed to bend the ends of the curtain rod bracket inward until the ends are somewhat flat. Mount the curtain rod bracket on the deadbolt strike and secure them in place with a bolt, washer, and nut. The curtain rod bracket should be able to pivot around the bolt securing it to the strike.

Step 6: Installing the Firing Mechanism

After you have assembled the firing mechanism, mount in on the side of the barrel as shown. The lower flat surface of the deadbolt strike should be against the pipe under the barrel, and the flat end of the curtain rod bracket should be able to pivot into the second to last hole on the barrel. This will allow the bracket to push in the push button on the firing pin, and thus fire the rifle. Use a small drill bit (I used a 3/32 in.) to drill a small pilot hole, then secure the mechanism to the barrel with a screw. If needed, add an additional screw to keep the deadbolt strike from pivoting from its position.

Step 7: Making the Firing Pin

Alright, now get that adjustable crutch piece you removed earlier, the end of this will be the rifle's firing pin. First, using a pair of pliers remove one of the push buttons from the tube. Line this up with the one still in place and make a mark on the tube just beyond its endpoint. Using a hack saw, cut the tube along the marked line. Now you have two separate pieces. The shorter piece with the remaining push button will be the firing pin; The longer piece will be used as a ramrod when cocking and loading the rifle. Drop your compression spring down the barrel, then insert the firing pin and push it down the barrel with the ramrod. Make sure the remaining push button is on the same side of the barrel as the firing mechanism.

Go ahead and test the firing mechanism and the firing pin. Push the firing pin down the barrel until the push button pops into the second to last hole (the hole the firing mechanism is set to). Remove the ramrod. Now push the curtain rod bracket against the firing pin's push button. This should release the push button and the compressed spring should shoot the firing pin to the front of the barrel. If it works, congratulations; you're almost done with your crutch rifle.

Step 8: Securing the Ramrod

Because you'll have to use the ramrod for every shot, it's probably a good idea to attach it to the rifle so it's always on hand. Find a small piece of PVC pipe that fits snugly over the ramrod and cut it to about 3 inches in length. Then, using a saw or some snippers, cut a small rectangle out of each end of the pipe. Slip it over the ramrod and line in up under the barrel. When you have it where you want it, mark the place on the crutch. After drilling pilot holes, screw the pipe onto the crutch with one screw in to middle of both of the rectangular cut-outs. Slide the ramrod into place.

Step 9: Creating the Trigger Assembly

Get another 3 1/2 inch piece of PVC pipe, this will be the trigger of the rifle. Screw another curtain rod bracket onto one end of the pipe. The pipe should still be able to pivot freely around this screw. Then, after drilling pilot holes, screw the curtain rod bracket onto the bottom rail of the crutch about an inch in-front of the crutch handle. Now you must simply attach the trigger to the firing mechanism. Again, after drilling pilot holes, screw two eye screws into the top rail of the crutch. Take a length of wire and tie it first to the firing mechanism, then thread it through the eye screws. Finally, thread it into the trigger and fasten it around the screw that the trigger pivots on. Trim any excess wire. When you pull the trigger, the firing mechanism should now pivot into its respective hole on the barrel and release the firing pin.

Step 10: Use and Enjoy

Congratulations! You've completed your Spring-Powered Crutch Rifle. Now you're ready to use it.

To load and fire gun, first, push the firing pin down the barrel with the ramrod until the push button clicks into the correct hole. Remove the ramrod and slide it into its sleeve. Then, drop your projectile down the barrel, aim and fire.

Thanks for reading this instructables post, and enjoy.

jlaake