Saturday, 12 July 2014

DIY Crossbow

Build Your Own DIY Emergency Crossbow

DIY Crossbow - The ZomBow.

So here it is my emergency crossbow build. The aim of this project was to show you how you can make your own homemade crossbow, with regular items found around the home. I used materials that virtually everyone should have access to, so you could easily make one for yourself. Just remember to stay safe and only use it in a safe manner.

This diy crossbow 'how to' will include what I've learnt along the way, including errors and improvement ideas. A quick reminder before we start, if you enjoy the video then don’t forget to give it a quick thumbs up and share a link to it with your friends - so let’s get to it.
Firstly watch the video to give you an overview of the DIY crossbow build.

Materials Needed:

  • Wood ( I used a reclaimed piece from a 77mm x 43mm length)
  • Gate latch
  • String
  • Screws
  • Metal rulers
  • Crossbow bolts
  • Wooden dowel
  • Copper saddle clip
  • Duct tape
  • Pencil

Tools Needed:

  • Router (you could use a file or chisel instead)
  • Router bit
  • Screw driver
  • Drill
  • Drill bits
  • Grind tool

Wood used for diy crossbow taken from an earlier project.

The wood I'm using is a scrap piece, claimed from my homemade t-shirt machine first seen in this video. To start I marked on my wood some channels for the bolt and string to sit in. I got the length for the bolt channel by sitting the bolt on top of the wood in the middle, leaving it slightly over hanging at the front, then marking out the position of the two channels with a pencil. I then used the rulers to draw straight lines from the marks I'd made.

Cutting out channels for crossbow bolt and string with router.

Next I needed to cut out those channels so I used my router, you could get the same result using hand tools like a chisel or file, but its going to take a lot longer. Its important that you stay true to the lines you've marked (as long as they are straight), as you don't want your cuts to be all over the place. The channel I cut as a guide for he bolt has imperfections, on account of me not being used to using a router. These slight flaws start to add up to reduction in the end result - I'll cover that more at the end of this post. These channels need to be cut deep enough to account for the bolts fletchings (those plastic wings at the back of the bolt) and to ensure the string can't accidentally fire.

Sanding edges.

When I finished routing out the crossbow bolt and string channels, I quickly cleaned up some of the rough edges with sand paper. It is important that you sand the edges, as they can cause snags and decrease efficiency. I would strongly advise sanding the edges of the channel holding the string, making them round. This will reduce the string jumping and snagging when being fired.

Metal rulers used as limbs for the homemade crossbow.

Then to make the limbs I took some metal rulers, taped them together with masking tape and drilled holes through them so I could attach them to the body of the diy crossbow. To attach them I marked through the holes I made in the rulers onto the wood and then pre-drilled to allow for the screws. At this point either limb was made up of two rulers and secured to the body of the crossbow with some 50mm screws.

Homemade crossbow.

With the limbs attached, I taped the rulers at the edges to stop them coming apart and added some string. At this point the ZomBow can fire bolts, but I made a few more tweaks to make the crossbow more efficient.

Latch has up and down motion need to fire crossbow.

Grinding a small piece off the back of the latch.

Our diy crossbow now has a trigger.

The DIY emergency crossbow trigger feels natural.

I wanted to add a firing trigger so I used this gate latch as it had the motion I wanted. I had to remove a small piece from the back and then I screwed it in place. This trigger does the job and it feels natural to fire it with your hand in this position. If you don't sand the string channel edges properly you'll notice the crossbow is tough to fire. Try not to place the latch too far forward, as you only want to make enough contact with the string to lift it up over the string channel.

Now one of our eagle eyed viewers noticed the bolt sometimes tips when fired (from this unfinished demo ZomBow video).

Diy crossbow bolt retention spring, made from a copper saddle clip.

Copper saddle clip made into a diy crossbow bolt retention spring.

So I crafted this little bolt holder using a copper saddle clip I had left over from my toy cannon build. By the way the people over at Make magazine liked our toy cannon project so much, that they put it in issue 40 of their magazine - so don’t forget to keep your eye out for that.

Wooden sight for our emergency crossbow made from a dowel.

But back to this build and another viewer suggested a sight for the ZomBow. So I made a very simple sight from a wooden dowel for our homemade crossbow. The sight is simply wedged into the hole in case I want to remove it, but you could glue it into position if you want.

Added more rulers to the limbs and used keyrings to attach the strings.

I also added some more rulers to the limbs for strength (it has 6 rulers per limb now in total) and attached my string to the limbs using keyrings. I swapped the masking tape bindings for duct tape and there you have it your emergency crossbow is complete.

DIY Crossbow Tips

While building this homemade crossbow I noticed that small things had effects on whether to increase or decrease performance.

Firstly I would ensure the channels used to guide the crossbow bolt and hold the string are sanded down. Any rough edges could cause the bolt to lose power through friction or could send it off at an unwanted angle. Likewise, the edges of the channel that holds the string should be sanded for similar reasons. I would recommend rounding off the edges of the string channel so it fires smoother.

I used keyrings to attach my string as they just made life easier when stringing the bow. But I feel them being free to move around is decreasing the crossbows efficiency. I would suggest going with my earlier solution before the video of making some sleeves for the string from plastic straws.

While still staying with the crossbow string I should say its important to have knots at either end that aren't going to undo. Because if they start to undo the string will slacken and hamper performance. Also I doubled over the string and twisted tightly as this winding adds strength to the string and make sure the two strings don't come apart when you fire the crossbow.

The bolt retention spring (made from the copper saddle clip) served two purposes. Firstly it holds the bolt in the crossbow, so you get it flying straighter upon firing due to it have a guiding hand. And secondly it acts as a guide for the string, making sure the string catches the crossbow bolt in the right way.

Homemade diy emergency crossbow.

Some of you may be thinking 'why didn't I just make a pvc bow?' and there are two reasons for that. Firstly I wanted to bring you something a bit different and secondly you can’t beat a zombie to death with a pvc bow - but you can with the ZomBow.

You could alter the design of this homemade crossbow to suit you, but if you do make one then share a picture with me on my facebook page or tweet it at GoRepairs.

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