Intro: Improvised Crossbow
The materials I used to make this were what I had on hand and everything on this crossbow was either found or constructed by myself. The only thing I bought to pay for this was a couple of wood screws, bolts, and O clamps. The only power tool I used to make this was a battery operated drill. This crossbow is part of a thiem I came up with to give an understanding of improvising should a catastrophic disaster ever happen where one would need to survive off of only what they could find, weather it be urban or wilderness. The tools I use were only used to speed along production of this item.
Since I used what was on hand, I will also give suggestions to other materials that I have had better results from, but can still be scavenged.
This article is for reference only, and I am not responsible for any injury for caused by the reproduction of this item.
Step 1: Outline
I apologies for the grainy appearance of this picture, I was experiencing some focus issues with my camera, but it gives you an idea of the lay out. The sections are broken down into; Bow, Stock, Trigger Assembly, And Buttstock. Here is a list of materials you will need to make this Item. The items that appear after a "/" are alternate materials that would be better suited performance wise.
2 Graphite Poles / 1" PVC
Electrical Tape / Duct Tape
4 O Clamps (not needed if PVC is used)
2 12' strands 550 Paricord "Guts" / Artificial Sinew
2 1x2x1.5 wood strips (preferably pine for easier working)
5 1" Drywall or Wood Screws
1 Wire Coat Hanger
2.5"x1" Sturdy Piece of Sheet Metal
JB Weld /Bicycle Seat Adjuster
Soda Can Cut and Flattened Into Sheet Metal (Not Needed With Bicycle Seat Adjuster)
4" Cut of Steel Banding
1 Ten Penny Nail
3 1/8"x2" Bolts or Any Other Item to be Used As a Stud
1"x6"x12" Piece of wood
Flat Head Screwdriver
Drill w/Drill Bits
Knife or Wood Chisel
Step 2: The Bow
I have had greater success using PVC for this step, and I recommend if you have it available, then use it. The problem I encountered with the graphite poles, is that they are round and tend to shift and offset the bow. This causes it to loose tension on the bowstring and in turn makes for a less effective weapon.
If you were to use PVC you would need a 1" or 1 1/4" x 3 feet. Find the center and measure out from the center about 1 inch either way. This will give you a 2 inch handle from where to start. You will need a saw that does not taper (like the PVC blade from a saws-all). Ordinary hack saws will cause you to saw at an angle that will cut clean through before the cut reaches the end of the PVC.
Starting from the middle you cut an angle until you reach the center of the pipe, then cut lengthwise down the center until you reach the end of that half. Begin an other cut on the opposite side and repeat the previous. You can't go wrong, it will look like a 3 foot pvc bow with a 2 inch handle in the middle when your done.
I cut my graphite poles to 28.5 inches. The rods themselves are 1/4 inch, and I used 2. I made them staggered to even out the tension. Like I said, this crossbow was made with what I had available. If you were to use graphite poles, I wouldn't recommend this if you can help it. Instead cut 2 poles evenly at about 3 feet each, then use the O clamps to connect them. After this wrap them with electrical or duct tape.
Attaching the Bow
Align the center of the two poles with the "muzzle" end of the stock. Drill 2 holes in the center so you can screw the bow into the stock. Use 2, 1 inch drywall screws to attach the bow. The same goes for the PVC bow if you decide to use it instead.
I make ALL my bowstrings from waxed nylon, unless I am reproducing an authentic recurve or short bow. In craft stores its also known as "Artificial Sinew." Ancient bowyers used animal sinew to make bowstrings. Sinew is a tendon, found in the legs of deer elk, and other game animals. Artificial sinew is a commercial reproduction of this tissue.
To make a bowstring suitable for this bow take a piece of nylon (I used 550 cord "guts") and tie it to one end. It does not need to be tight, this will come later.
Run the string to the opposite end, loop it around, and run it back again. Do this about 3 or 4 times until you have the end of your nylon cord on the opposite end of where you started, and be sure to leave about 8 inches of slack. It should look like you have 3 or 4 strands of cord.
Take the slack and tie a knot at the base of the loop. Wrap any excess cord around the bowstring and tie it off.
Now bend the bow and remove the loop on the end you just tied. Spin the entire bowstring until it shortened to about 6 inches below the notches.
Bend the bow and re attach to the notch. You may have to do this a few times because the string has to settle to the tension of the bow. The more you spin the string the tighter it will become and the more power you will have, but be careful not to over flex the bow.
The stock and buttstock are the two easiest parts to craft. The stock is made from 1x2's and joined with drywall screws. A small area at the rear is carved out for the trigger assembly. I took each 1x2 and cut a slit half way to the middle by about 5.5 inches long on each one. When you join the 2 boards together, it makes a space about an inch wide. Plenty of room for a trigger, and an area to attach the buttstock to the stock.
Saw a track a little deeper than the trigger area to allow for movement of the trigger claws.
The trigger assembly consist of the following parts; trigger, trigger extension, trigger claws, and resetting spring.
I constructed the trigger from a soda can, and JB Weld. The soda can acts as a reenforcement to prevent the JB Weld from cracking. Two holes were drilled just under the axle hole on the front side of the trigger.
The trigger extension, made from a wire coat hanger, was placed inside the two holes. A better device to use for a trigger would be a bicycle seat adjuster. Its shaped like a trigger, and is more sturdy than a self made trigger.
The trigger claw was made from a single piece of sheet metal cut to the size of the trigger area on the stock, but with enough extra on the edges to keep it well inside the track. The trigger claws move down below the trigger area, when the trigger is pulled, and release the bowstring. They come back up from the resistance of the resetting spring. The crossbow is then ready to replucked and loaded.
I made the resetting spring from a piece of steel banding. One end was curled until it was cylindrical, and the other was flexed under the upper tab of the trigger claw. The resetting spring is not necessary, but makes for a quicker reload. The weight of the plucked bowstring, however, is enough to hold the claws up until the trigger is pulled, as I have seen with previous crossbows I have made.
Step 5: Buttstock
The buttstock is simple. Its purpose is to allow you to stabilize the crossbow against your shoulder for better accuracy. This means as long as it still serves its purpose it can be as complex or as simple as you want to make it. Always make sure you can fit a small part of it in the trigger assembly area securely. I took a 3/4 x 4 x 15 inch and made 2 cuts that equal a 90 degree angle. A 2.5 x 2 inch tab was left on the front and that is the area I placed into the trigger assembly area to secure it to the stock. Its as simple as it can get.