Introduction: Knex Heavy Crossbow

About: K'nex is my thing!
Well folks, this is a little project I've been working on very half-heartedly for ages. It was originally going to be a concept gun, and it was half done I tried to build it for performance as well. So, I got this slightly odd cannon-ish crossbow.

Anyway, the two main new things I put into this gun are the bending limbs, which I have found have actually increased power by a large amount, as well as making it look cool. The other thing was the repeating mechanism I've had bouncing around my head for a bit.

So, all in all, it's a huge, repeating, missile-launching crossbow. It gets 100 feet of range from its sitting position with the elastics shown. More could easily be added, but I didn't. Don't ask me why, I don't know.


Video to come.

Step 1: A Few Things...

I got a few things to say before you get started.

1: This is a difficult build. Its complicated, tricky, and overall requires a fair bit of skill. I would not recommend building this as a first project, or anywhere near that mark for that matter.

2: This gun is mostly a concept idea. If you are building this just for the sake of building something that can chuck lumps of knex great distances, this is good, but there are certainly other guns out there that will do the same, whilst being more piece efficient, smaller, easier to build... I'd try some of cannons if that be what you are looking for.

3: Just a little something that I always do... Building is much more enjoyable and relaxing if you are prepared. Sounds dumb I know, but I always build to my favorite music, in my favorite chair with a dish of cookies and some tea, and I always, always have all the pieces I need with me. Part counts are my best friends. It makes it so much more pleasant than crouching on the floor trying to find the pieces to put together this and that.

4: For all you people who will be asking: "Oh boy oh boy, there must surly be 4 more versions coming out soon!", tough beans. There will be no other versions, though I may try my luck with making a rod shooter with this mechanism. That won't end up looking much like this though, if I ever do build it.

Anyway, if you made it through that and still wish to build, best of luck to you!

Step 2: Parts List

Crunch time. Here's where you will find out if you have the pieces to make my crossbow. I know, I know, the number of pieces is catastrophic, but hey, as I already said, I made this mostly as a concept weapon, so take it easy...

I made separate parts lists for the bipod, in case you don't have enough pieces for the gun, you can scrap the bipod to save a few parts if you wish.

All numbers will almost undoubtedly be incorrect by some margin, forgive me.

For the bi-pod...

Green - 71
White - 58
Blue - 7

Dark grey - 12
Light grey - 4
Red - 9
Green - 8
Yellow - 31
Orange - 24
White - 7

For the gun...

Dark grey - 26
Light grey - 25
Red - 64
Green - 138
Orange - 114
Yellow - 283 (ouch...)
White - 40
Blue - 6

Green - 635
White - 155
Blue - 54
Yellow - 37

Black wheel (for the handle, smallest in photo) - 6
Blue spacer - 102
Silver spacer - 55
Hinges - 2
Medium wheels (largest in photo) - 4
Black Y connectors - 13
Tan Clip 22
Small grey wheel - 2 (photo)
#64 elastics - 13
#32 elastics - 6

Step 3: Bi-pod

This bi-pod really isn't too good, but it supports its weight, and gets the job done, so... Good enough. I had made a few folding ones but they were very wobbly.

1: Make this
2: View from the side
3: Make these
4: Build this
5: Put it onto the other bit
6: Put the other side of that thingy on
7: Build a mirror opposite
8: Connect them with the part you made first
9-11: Build this chunk with the aid of the next three photos
12: Add it to the top of the other part
13: Another view
14: And another view

Step 4: Bow

This is the step for the bow. For some reason, it ended up epic long, but it should be easy to follow.


1: Build these two
2: Build this chunk. Its 4 layers thick, and there are y connectors on both sides of that blue rod
3: Yep... Its still 4 layers thick
4: Snap the first bit onto the second bit like so
5: Slide two medium wheels over the rod
6: Put the other identical piece on the other side
7: Build another
8: Make these two bits
9: Build this chunk. Be sure to get all the blue rods
10: Add the two bits you just made
11: Gather all these pieces
12: Clip em all onto the part you made previously
13: Add all the rods
14: Build these four pieces
15-18: Build this chunk from the photos provided
19: Put the four bits you made onto the chunk you built just now
20: Gather TWO #64 elastics. I know it shows 3, dont pay attention to that
21: Double each one up once, and put it in the bow like so. This will require removing a few pieces for a moment.
22: Wrap them around like so
23: Add the first chunk to the second chunk. This will be tricky.
24: Close up. Not that the Y connectors are attached to the blue rods
25: Everybody's favourite part... Build a mirror opposite! Yay!
26: Add the ends. You'll need to remove the blue rod on the yellow connector, put it through the red rods, and re-connect.
27: Take the elastics from the main part and get them onto that yellow connector. Once again, you will need to take out a few pieces to get the elastics in.
28: Do the same with both sides
29: Tie 4 strings of 3 #64 elastics.
30: Take the four strings, and put two on top of each other onto a blue rod
31: Using more demolition, add that blue rod onto the yellow connector
32: If you did that right, This is what it should look like
33: Do the same with the other bow. You should get two joined bow pieces.


Step 5: The Front

...For a lack of anything better to call it... Its the part that goes in-between the bow and is at the front of the barrel.

1: Build this piece
2: View from the top
3: Upside down
4: Build these four bits
5: Snap two of them onto the part you made first
6: View from the top
7: Make this one
8: Straight up
9: Upside down
10: Snap in the two bits you made earlier

Step 6: Upper Barrel

The title says it all.

Oh, the cliché...

1-3: All photos of this barrel bit. Shouldn't be too tricky, it helps to build each line of yellow connectors individually though, I can say that.

Best of luck!

Step 7: Lower Barrel

I'm afraid this wont be another 3 photo step... The lower barrel includes the magazine. Good luck.

1: Build these two panels. There is a dark grey connector snapped in on that white rod in between the yellow and the wheel. It doesn't matter which direction it is going in.
2: Flipped around
3: Gather together these bits. Note the whites on the left-hand panel
4: Add the two together
5: Put the other panel over top
6: Build this track. Note the pieces on the left end
7: The normal end
8: The "abnormal" end
9: That same end upside down
10: Blurry photo of the same thing
11: Add in the mag! You may want to take off a few rods from the top of the mag and put them back in once you have it roughly in place.
12: Epic close up. Yes, definitely epic
13: Slap on the outer panels you built first
14: From the top
15: String together your 6 #32 elastics as so
16: Wrap the elastic around the wheels like so at its midway point
17: Slide them into the yellow connector slots on the connector one from the far end.

Bravo. Keep going!

Step 8: Handle and Mag

Here you will, (you will, won't you...?) build the handle and the other side of the magazine wall.

1: Build all the items in the photograph
2: Slide the shown bits over the shown bit
3: Add the other identical panel over top
4: Snap the two small pieces onto the yellow rod on both sides
5: Add one silver and one blue spacer onto that rod (both sides)
6: Build all this junk
7: Slide said part over the one with the blues on it
8: Add the other similar blue-less part on as well
9: Add on that piece to the chunk you just made. Do it on both sides
10: Slide the blue through the red connectors that are a part of the slide (not the ones connected to the green connector) and snap in the three pieces as shown.
11: Make all the shown bits (sorry for the blur)
12: Snap the two handle parts together
13: Add in the parts with the spacers like so
14: Slide a blue rod through the yellows and snap in that mutated oodammo
15: Add a blue spacer and snap on arms to the blue rod (do on both sides)
16: Add the wheels to the handle. You can use the other type of wheels too, but these ones work better, so use them if you have them.

Step 9: Trigger Mechanism

This is the actual stopper for the trigger, and some other random stuff for the stock.

1: Build this little chunk
2-4: Make this little block as well using the next three images.
5: Make these bits
6: And these ones
7: Snap the one piece in like so
8: Slide on that piece
9: Snap on the second panel
10: Add spacers
11: Put on the rail
12: Connect the two parts
13: Slide a blue rod through that red connector
14: Snap in 3 light grey connectors
15: Put your head in a position to see this
16: Add an elastic (any kind) as shown.

Step 10: This and That

Here are just a few other bits and pieces you will add on in a moment.

1: Yup. 4 of them.
2: Four again
3: Spacers on the hidden side, too
4: ...
5: Build these two
6: And these two parts.

That was easy.

Step 11: Put It All Together

Big step, but probably the funnest.

1: All the pieces you should have
2: Start by connecting one bow arm to one of the front track pieces. Doesn't matter which one
3: That connection from another view
4: Connect the other side. The elastics should be pulling now, and will need to be held in place until the next part goes in.
5: Put the other front bit in
6: Add the lower barrel to the track with the blue 3d connectors on it
7: Close up of the connection
8: And add the upper barrel
9: Add that little part that you made in the handle like so
10: Close up of something, not sure what its showing that you don't know about though...
11: Slap on the handle. Then connect it
12: Close uppy action
13: Uber close uppy action
14: Random photo
15: And put in the end bit
16: Put in the trigger mechanism. Its on the top barrel
17: View from on top
18: Slide the dark grey connectors from the trigger onto the blue rod as shown
19: Connect it up at the back with the back end of the trigger
20: IaC FAIL! I forgot to add this elastic earlier... Its a #64. Take apart the track inbetween the mag walls and wrap it around on top.
21: Put it on the inside of the handle, and reassemble everything. Sorry, guys.
22: Add the side walls to the stock
23: See how that all works together...
24: Not sure what this photo is for... Make sure your crossbow looks like this, I guess :-p
25-27: Add in those really long orange parts.
28: Add that part you made in "this and that"
29: Put the rails on too
30: And slide in the top part
31: View from the top
32: Take two blue rods from the barrel that were on the blue 3d connectors and put them through the top of the bipod as shown.
33: Snap the blue rods back. Your bipod is now attached
34: Flip it right side up. You are nearly finished!
35: Twist the barrel so that you can slide that piece you made in "this and that" into the barrel. The dark grey connector should be facing the back of the gun, on the lower side.
36: Twist the red connector on top like so
37: Take the #64 elastic and put it over the yellow connectors slot, like so
38: Put the red connector back on.

Good work! Now just to fire it!

Give yourself a high five, and a cookie. And send me one while you are at it.

Step 12: Loading + Firing

Here's the fun part.

1: Ammo. Build it
2: Rig the mag pusher like so, The elastic goes into the slot in the yellow connector
3: Take out the pusher and put it somewhere that's not in the way
4: Put all the ammo in (its direction is not important) and put the pusher back on top
5: Draw the strings back and hook them onto the trigger wheels. A piece of ammo should slide into position.
6: Pull the trigger! Repeat for each piece of ammo.


Step 13: Done!

Nothing much to say here, except well done, thank you, and good night.