Ballista Design Instructions

These are the instructions to make a ballista. The materials required are here below. Not all of these materials will be used.

*Disclaimer - The diagrams are not proportional, they are just there to give a rough idea on what the object should look like.

The materials are:

3— 2” x 4” x 8’ long Stud (Common); 1.5” x 3.5” x 8’ (Actual)

50’ length— ¼” diameter Braided Polypropylene Rope

Wood Glue

Assorted nuts, bolts, washers

Wood screws

¾” x 3 ½” Lag Screws

Take one of the provided 8’ 2x4 and cut it into 3 pieces, each measuring 28.75” in length, set aside the remaining 9.75” for later.

Lay one of the 28.75” perpendicular to the other 28.75” 2x4, directly at the middle point (14.375”). Both should be laying on the flattest, widest part. It should look like an uppercase T.

Ensuring the vertical plank is at the midpoint of the horizontal plank, add wood glue to the top of the vertical plank and let it set. It doesn’t need to be completely dry, just make sure the pieces aren’t sliding around. From there you will need to use a pocket hole jig, screwing two screws into either side of the wood. You should now have 4 screws connecting the two pieces of wood together.

Take the remaining 9.75” long plank that we set aside in step 1 and cut it in half along the longest length, you should now have two blocks that measure 1.5”x3.5”x4.875”

Take one of the blocks and, using two wood screws, screw, it into the top left face of the horizontal board, the top left part of the T. Make sure it’s flush before you screw it in, and line up the block so it lays ON TOP of the horizontal board with no overhang. It should be laid so that the length is 1.5”, the width is 3.5”, and the height is 4.875”.

Repeat step 5 with the other leftover block. This time attaching it to the top right face of our T.

Now drill one hole all the way through the face of the plank, it should have a diameter of 0.5”. This should be 4.5” to the left of the block on the right. It should also be drilled in the middle part of the face, so 1.75” from the top of the horizontal plank, 1.75” from the bottom of the plank.

Repeat step 7, this time placing the hole 4.5” to the right of the block on the left.

Drill 2 more 0.5” holes, placing one 0.5” to the left of the hole from step 7 (the hole on the right) and placing our second hole 0.5” to the right of the hole from step 8 (the hole on the left). Remember, these holes need to be placed in the middle of the plank’s face, and they need to go all the way through the plank.

Take the 3rd 28.75” 2x4 that we cut out in step 1 and screw it on top of the blocks, this will create our crossbar and give us an extra thick T top. The new plank should fully occlude the original horizontal plank and should be laid in the same orientation as the original plank.

Bust out the drills again, we’re making more holes. Drill 4 holes in the new plank, directly above the holes we drilled in steps 7-9, all of the new holes will also be 0.5” in diameter. So from left to right, the first hole is 6” from the left edge/4.5” right of the left block, the second hole is 0.5” to the right of the first hole, the third hole is 0.5” left from the fourth hole, and the fourth hole is 6” left of the plank’s right edge/4.5” left of the right block. After everything is said and done, you should have a clear line of sight through the holes.

Now take our second 8’ 2x4 out and cut out 1’ from the plank, leaving you with one plank measuring 1.5”x3.5”x1’ and another plank measuring 1.5”x3.5”x7’, set this plank aside, we will be working exclusively on the 1’ plank for this next step.

Cut the plank in half lengthwise, then in half again, you should now have two planks measuring 1.5”x0.875”x1’ and one plank measuring 1.5”x1.75”x1’, set this plank aside, we will be working on the two planks with the width of 0.875”. Having these planks separate should make the next step easier.

Now you will need to make cylinders out of these 2 planks, each one with a diameter of .75”. Be aware that you may have to shave off the excess in later steps. Once finished you should have 2 cylinders with a diameter of .75” and a length of 1’.

Take the 1.5”x1.75”x1’ we set aside in step 13 and cut it in half along the width, you should now have 2 planks measuring 1.5”x1.75”x6”. Now cut each of those pieces in half again until you’re left with 4 planks measuring 1.5”x1.75”x3”

Take the 1.5”x1.75”x1’ we set aside in step 13 and cut it in half along the width, you should now have 2 planks measuring 1.5”x1.75”x6”. Now cut each of those pieces in half again until you’re left with 4 planks measuring 1.5”x1.75”x3”

Before we do anything with the cylinders we need to create the stand for our ballista. We will do this by taking the 7’ 2x4 we set aside in step 12 and cutting 1’ out from it, setting aside the 6’ plank.

Now take our 1.5”x3.5”x1’ plank and; using a pocket hole jig, attach the plank to the very front of the ballista with one screw on either side, it should be flush with the boards and should make a stubby capital T when looking on from the front. You’ll also want the wider, 3.5” part to be the face at the front, the plank should line up quite well with the plank we mounted to create the original uppercase T.

Take out the 6’ 2x4 we set aside in step 17 and cut out two 1’ planks from it. This will leave you with one 4’ 2x4 and two 1’ 2x4s, set the 4’ 2x4 aside as we will not be using it for these next steps.

Now take 2 feet of our Polypropylene rope and thread it through the rightmost holes on our T. Then take the rope and push it back in on itself through the same holes, be careful not to pull it too far though, as you’ll want to have a little loop of rope near the bottom hole.

Now take 2 feet of our Polypropylene rope and thread it through the rightmost holes on our T. Then take the rope and push it back in on itself through the same holes, be careful not to pull it too far though, as you’ll want to have a little loop of rope near the bottom hole.

Insert another 1.25” diameter rod up at the top of the rope this time, tying the rope down onto the top rod and suspending the rope in place. Feel free to use whatever knot keeps it secure and feel free to double-knot for added security. You will need to leave a little slack for this next step.

Take one of the 1’ 2x4s from step 19 and insert it in between the rope, you can now wholly tighten(we’re talking REALLY tight)the rope at the top and cut off the excess rope at the top, this should leave the plank suspended within the rope.

Repeat steps 20-23 on the left-most hole, you’ll be using up the remaining 2 1.25” diameter rods and the remaining 1’ 2x4, you should still have both of the .75” diameter rods and the 4’ 2x4.

Take the 4’ 2x4 we had leftover from step 19 and cut a 32.25” plank out from it, setting the remaining 15.25” 2x4 to the side

Cut that plank in half along the skinniest length, leaving you with two planks measuring 0.75”x3.5”x32.25”. Set one of the planks aside, and then cut the other one in half again along the same length, you should now have two planks measuring 0.375”x3.5”x32.25”.

Mark the halfway point of the wood’s length, right at the 16.125” mark, and drill a 0.5” diameter hole 2.5” up from that. So drill the hole 16.125” from the longest edge and 2.5” up from the side edge right on the face of the first plank, drilling the hole all the way through. Then drill another 0.5” hole 1” to the right of the first hole, remaining even and level with the original hole. Repeat this until you run out of space on the board, you should have somewhere between 8-12 holes on one half of the plank, the exact amount doesn’t particularly matter, as long as the holes 2.5” up from the edge of the board and all of the holes are level.

Repeat step 27 on our second board, the holes will need to match up exactly with each other, it might help to stack the board on top of each other and drill all the way through, you should have a clear line of sight through the holes in the boards.

Slide one of the planks onto the ramp face, this will be the left wall of the ramp, lay it on its side such that the faces of the plank are facing outwards and inwards. You’ll want the half with holes near the back of the ballista, and the holes themselves should be closer to the ceiling than to the floor. Once the prerequisites are met and the board is placed flush on the left side of the ramp, screw in 5 screws from the bottom of the ballista up into the plank. One screw at each end, one in the middle, and one screw each in-between the middle screw and the outer screws. You’ll likely need to use 3” wood screws or something in that neighborhood, just make sure it’s not so thick it can't fit within the smaller planks of the ramp’s walls.

Repeat step 29 for the right ramp wall. Again making sure the half of the board with the holes is at the back of the ramp and the holes themselves should be closer to the ceiling than the floor.

Take the 15.25” 2x4 plank we set aside in step 25 and cut off a 4.5” chunk, once again leaving the remaining 10.75” of wood to the side.

You’ll need to cut the block of wood once more, cut 1 inch off of the side that measures 3.5”, this will leave you with a block of wood measuring 1.5”x2.5”x4.5”. Discard the smaller piece.

Now take the block of wood and drill a 0.5” hole through the side of the rectangle measuring 1.5”, drill the hole all the way through and drill it 4” up from the base of the rectangular prism we’ve created.

Drill another 0.5” hole 2.5” up from the base of the block, the same face of the block as our first hole, and make sure it goes all the way through. This will be what our firing pin goes through to keep this block secure, you’ll want to make sure this new hole is level with the holes we drilled on the planks back in steps 27 and 28. Like I said this will be what our firing pin goes through so you’ll want a clear line of sight through this second hole and the sets of holes we drilled for the ramp’s walls.

We’re almost there, now we’ll be attaching the ropes and the launching block. To do this first you’ll need to carve out a slit on the ends of our launching arms (the planks in between the taught rope from step 23). The slits will need to be roughly an inch deep, 0.5” wide, and going all the way through the wood. Again you’ll be doing this on the ends of our planks.

Now take a 2” wood screw and drill it on the outside face of the launching arm. You’ll want to drill it roughly 0.25” out from where the slit ends on the outer face. YOU WILL NOT BE SCREWING THIS SCREW IN ALL THE WAY. Just wanted to make sure you didn’t get to screwing upon first glance at this step, I probably would. Instead you’ll want to leave about half an inch of screw sticking out. Do these steps on both of our launching arms, screwing the screw in on the outer faces of both.

Making sure the launching arms are rotated as outwardly as possible, (you may need to rotate the winch mechanism for the arms clockwise) tie the end of your polypropylene rope spool to one of the screws heads we’ve left sticking out, threading the rope through the slit on the first launching arm, and then taking the rope through the slit on the other. From there you’ll want to cut the rope off and leave enough for excess to tie another knot around the screwhead. Don’t tie it off quite yet though, we’ll need to do something else first, so for now just leave the one end tied and the other end of the rope dangling about.

With the block we made in steps 31-34, thread the rope through the hole at the top, you may need to use a toothpick or some small splinter of wood to guide it all the way through the hole.

Finally, place the block in the ramp (with the holes on the sides of course) and tie the other end of the string on our screwhead. The rope should be fairly straight and have little to no slack in its current position, pulling back on the block should take considerable effort and the wood arms should move back as you pull the wood block back.

Hooray! We are (almost) done, we just need to make the firing pin and we’ll be done. Take the leftover wood from step 31 and cut off 5”. This will leave you with a piece of wood measuring 1.5”x3.5”x5”.

From there, we’ll chop off .75” from the shortest side, cut off 2.75” from the second shortest side. This will leave you with a rectangular piece of wood measuring .75”x.75”x5”.

Now you just need to chop and sand until you’ve created a cylinder with a diameter of 0.45” and a length of 5”, this will act as our firing pin. You’re finished! Now if you wanna test it just pull back on the wood block to your desired distance, slot the firing pin through the nearest hole to lock it in place, and then as soon as you’re ready to fire, pull it out and let er’ rip!If/when the winch for the launching arms starts to slip and don’t create enough tension, insert the 0.75” rods into the holes at the front of the Ballista to physically block the launching arms’ winch from moving.