Introduction: Knex Heavy Cannon

Picture of Knex Heavy Cannon
Here it is: my cannon. It shoots large missiles, and shoots them hard. It is powered by 48 rubber bands, tied together into 8 strings of 6. It is 2 feet wide (on the bow) and 5 feet long.  It has an average range of about 100 feet shot from the resting position. It uses a ton of pieces, I know, though I might work on a smaller version later. If you do build my cannon, please know that I am in no way responsible for any damage done with it.

I have made a few other versions of this gun. Check them out!

Step 1: Pieces

Picture of Pieces

Here is where you'll find out whether you have enugh pieces to make my cannon. It uses a lot!

Just so you know, this list may be subject to counting errors.

Dark grey--------80
Light grey--------28
Yellow------------326 (ouch!)
Purple------------349 (woof!)
Blue--------------255 (dang!)

Red--------120 ( If you have them, 3 of those can be tan)
White------505 (choke!)
Green-----532 (dies)

Other Pieces:
Tan Cap-------------2
Black y connector-10
Silver spacer-------39
Blue spacer--------64
9 Hole panels-----8 (see second and third picture)
Medium Wheels--8

Toatal: 2820!

Parts list for the ammo



Step 2: The Bow

Picture of The Bow

This is the bow. Build it.

1: What you are about to build
2: Make these
3: The same thing flipped around
4: A close up. The connector inside is a light grey, the 2 pronged one
5: Make this. The stand attaches to it
6: Another view of that thing
7: Lower Part of the lower bow. Make sure to get all the greens on there.
8: Just so you can see the white rods
9: Same as last picture, Upside down
10: Upper part of the lower bow. This goes on top of what you just made
11: Close up of the front
12: Upper part of the upper bow. Remember the reds and green connectors on top
13: Same as last photo, upside down
14: A little close up of the back of that one
15: Just in case you can't see very well......
16: Lower part of the upper bow
17: Same thing upside down.
18: A close up of the side. The grey connector goes through the red rod on which all the rubber bands are strung.
19: You'll never guess what this is.....Another close up!
20: Close up
21: Upper and Lower upper bows put together. No tricks here
22: Upper and lower lower bows put together
23: Just showing you that the red rod goes through the grey connector
24: A close up of the connection at the front
25: Get ready to attach the upper and lower bows as shown
26: And finally put together
27: Attach the wheels at the ends as shown
28: Attach the white and blue rods to the light grey connector in between the wheels
29: A bad picture of that connection
30: Attach that long piece you made at the beginning on the bottom of the bow as shown. this will Attach to the stand later
31: Just another photo of that connection

Thats the bow!

Step 3: Stringing the Bow

Picture of Stringing the Bow

I find that this is the best time to string the bow. Later, the accesories and the barrels get in the way and make this task much more difficult, so, do it now!

You need to use #64 Elastics in this gun. 48 of them, to be exact. These are the normal thick ones, that are used for most usual houhold deeds. You can easily get these for about $2 at any office store. If you cant get your hands on any of these, you will have so mix and match with other rubberbands. Anyway...

1: You will need to knot the elastics together. Do so as shown.
2: Pull it tight
3: Put the next elastic over the other like so,
4: Pull it through,
5: Pull the other on through,
6: And tighten.
7: Keep going untill you have a 6 elastic long string,
8: And make 8 more!
9: To string the bow, you will need to remove a couple of pieces. you should then slip 2 rubberbands over the red rod, and put them on one wheel.
10: Attatch the other end to somwhere by the grey rod for safekeeping
11: Do it again, and add the grey clip and attatch it to the white rod
12: Put the pieces you took out back on.
13: The elastics at the other end
14: Repeat the drill on the other side
15: And put it all back together
16: Strung bow!

Step 4: The Stand

Picture of The Stand

This is the stand. It pivots up and down, and has a bit of give-and-go side to side. It holds 4 pieces af ammuniton, and locks them in lightly.

1: The stand
2: Make these
3: Make these as well
4: Make two of these
5: Another picture of the same thing
6: Build these side panels
7: And this thing
8: That thing again
9: Make this
10: Put that thing together with the thing you made in the last picture
11: Add side panels
12: Put those tracks in
13: Add those weird things as shown
14: put in those ones you made first (make sure that they are the right way around)

Step 5: The Upper and Lower Barrels

Picture of The Upper and Lower Barrels

These are the barrels. Nothing special about them, Just a slide for the ammo to travel down.

1: The Upper barrel, upside down
2: The upper barrel, right side up
3: A view of the right end
4: A view of the middle
5: And a view of the left end
6: Just so you can see where to put the reds
7: The lower barrel right side up
8: The lower barrel upside down
9: The right end
10: And say hello to the left end

Step 6: Trigger System

Picture of Trigger System

This is the trigger system. It is relatively complicated, probably the most so on this cannon. It has to be able to hold a great deal of weight in two stages. First, while you are loading, the elastics are wrapped around the red rods at the back, so the must be very secure. Once the bullet is at the back and locked in, all the elastic pull is put on it, so it too, has a very secure holding mechanism. It is released by simple bulling back the large knob on top. If you didn't get that, don't worry, there will be better explanations later on.

This step has been split up into a few smaller substeps for your convenience.
1: What you are about to make
2: Build this little part
3: Then make this
4: Another view of that thing. There are blue spacers on every yellow rod
5: A view from the bottom. Make sure that all the rods are lined up
6: Build this
7: And tape it up. Make sure the tape is not obstructing the hole
8: Make this little guy
9: That thingy upside-down
10: Another view....
11: A view from the back...
12: From the top...
13: Add the pin to that weird thingy with a blue rod and a blue cap (can be tan)
14: Put the handle on top
15: A view of that connection. Make sure all the rods are lined up and attached in there correct places
16: Put it on that thing you made first
17: Now make this. It is the upper part of the back of the slide
18: A view of the end
19: And from below
20: A view from a different angle. Remember the whites on the end
21: The lower back slide. Prettymuch the same
22: A view from the end
23: A view from an angle again
24: The biggest chunk of this mechanism. Your about to make it
25: Make this back part. Remember those pieces inside
26: A view of the back of the back part
27: Looking inside it for a better view
28: Looking inside the top for a better view of that
29: the other part of the main mechanism. There are blue and white rods on all of the yellow connectors.
30: Just so you can see that
31: A close up of the front
32: A close up of the top (upside down)
33: The top from the back (still upside down)
34: The bottom (close up and upside down)
35: Just so you can see the whites
36: The back part and the main part
37: And that connected. Yay!
38: Added the knob thingy
39: Added the bottom slide...
40: That connection....
41: Added the top slide
42: And a close up of that connection
43: Looking down that barrel
44: Add an elastic on top. It should only be strong enough to pull the knob all the way down, no more.

Sorry about that step being atrotiously long. Lol.

Step 7: Extras

Picture of Extras

None of these are strictly nessicary, but they help when you are using the cannon, and make it look a lot cooler.

1: Chin rest. You use it when you are looking through the sights
2: Chin rest upside down
3: A view from the back
4: One of the sights. Only put green rods in the first row of connectors and the last.
5: The sight from underneath
6: Another picture
7: The other sight, identical to the other one except for the greens on the end
8: Build these

You'll put all these on in the next step.

Step 8: Assembley

Picture of Assembley

This is the fun part. You get to put it all together. I don't think it should be too hard. Onwards!

1: Exploded view. Sorta. These are all the bits you should have
2: Connection of the bow to the stand. Notice how everything lines up nice and neatly
3: Same as last picture, except from the front
4: Add the lower barrel. Easy
5: Just a little close up of that connection
6: Add the upper barrel. Also easy
7: A handy-dandy close up of that connection too
8: Connect the trigger. Its looking pretty cool now!
9: Picture of that last connection. Sorry its a bit fuzzy
10: Attach the side panels to the barrel. Do so on both sides
11: That looks awesome now
12: Attach the cheek rest. This also covers up some of the ugly upside-down connectors underneath
13: Just putting those greens in place
14: Another picture of that cheek rest
15: Attach the rear sight just behind the row of reds. Notice how the reds on the ends of the sights are lined up all nice and neatly
16: Attach the other sight with the greens facing forward
17: Woa, you got yourself a seriously good looking cannon there!

Step 9: Ammo, Loading and Firing

Picture of Ammo, Loading and Firing

To Be truthful, this is difficult, and takes a bit of getting used to. Once you get a hang of it though, you can reload in under 30 seconds. Be very careful when doing this, make sure everything is exactly as I say it should be.

1: Were going to make the ammo first. Make these
2: And make this.
3: Close up of the end
4: And another one
5: Add one of those bits you made first on top
6: And the other one on the bottom
7: Finished bullet
8: Pull back the bottom 2 strings (the ones on the bottom wheel) to where shown
9: Hook it around the lower red rod as shown. Do the same on the other side
10: Take the next two strings (the ones on the wheel second from the bottom) and put them on the upper red red rod as shown is the picture
11: Take the 2 strings second from the top and put them on the upper red rod
12: Take the last two strings (which are on the top) and put them on the lower red rod. To will have to switch the upper string beneath the lower string somewhere around the middle of the bow. You can do that however you want.
13: Take your ammo and slide it in the front as shown
14: Slide it all the way to the back (which should look precicley as shown)
15: Pull back the knob on the back so the tan or red rod slides out of the way
16: Push the ammo into the now vacant spot where the red was. Then push the knob down so that the rod goes through the connectors on the back. Make sure it goes down as far as possible.
17: Take the elastics and put them on the tips of the white rids as shown. they can also go onto the yellow connectors if you need to. Be VERY, VERY SURE that none of the elastic strings are in front of any of the rods on the back. Failure to do this can and will result in misfiring and a lot of broken pieces.

Your loaded! So is your cannon! Be sure to shoot with extreme caution, never point it at anything valuable, such as a family member. I do not assume any responiblilty for and damage caused my this cannon.

Because I love making videos I added one of a close up of the trigger system when firing.

Step 10: Finished!

Picture of Finished!

Your done! Not much to say here, exept be extremely careful. And I mean it. You could really do some damage if you are not wary of what can go wrong.

Well, an a happier note, your finished! Feel free to ask any questions. Thanks!



soepie7 (author)2016-07-09

What's up with the smaller versions?

Forgotten_Memories (author)2016-06-13

WOW! Thats pretty powerful! Great job!

The Knex Inventor (author)2016-06-05

Nice! BTW, what happened to the other versions of this? (micro, nano, handheld, etc.)

autumsawesome (author)2016-04-12

Here is a link to an Instructable of a Crossbow that I made, that is based off of this one.

Building crossbows is really fun (:

Knextrain10 made it! (author)2015-11-17

I made it and it is AMAZING!!!!!

Knextrain10 (author)Knextrain102016-01-07

I still have it together

shortclient52 (author)2015-05-03

im ordering the parts to make it

shortclient52 (author)2015-05-03


Dr MonkeyMan (author)2015-02-04

Aint nobody going to rob my house tonite!

Yttrium (author)2015-01-29

Very nice cannon. I bet very few people have the pieces to build it. Since I build ball machines, though, I most definitely have enough.

degah12 (author)2015-01-24

This inspired me to building on instructables

I dont have NEARLY enough peices though. not even enough to make the handheld one

EpicMinecrafter870 (author)2014-12-04

add a white rod to the front of the shell to make it more aerodynamic. Also, DEFINITELY USE IN KNEX CTF.

whispersync (author)2014-11-03

yes they are

knexpert4life (author)2014-11-02

I love this gun i made this gun about 3 months ago and already i demolished a plant pot,exploded my knex box and a solid piece of wood!?? Best thing I've ever made

knex akbar (author)2014-05-31

reading the comments i'm not so sure if it's safe to build this thing...

Don't worry about that, it is very safe. As long as you be careful, because of it's structural integrity you will be fine. It's scary at first, but don't worry about it, just go ahead and do it! =D

I'm not worried about destroying something i'm worried about breaking my knex pieces XD

Hazza4531 (author)2014-07-02

I built this at a friends house over the holidays, fired the first shot which promptly went through a window, had to take it to pieces again :(

Everliving2000 (author)2014-06-24

Pretty much tripling the size of this, and it is HUGE, and it is almost done! =D

Everliving2000 (author)2014-05-22

Screw rubber bands! I use surgical tubing! IT IS INSANE, FOR I HAVE MADE A BIG MOD. >=) It shoots around 200-300 feet... I need more blocks of wood, nuff said.

I_am_Canadian (author)2011-09-01

You broke a window with it!?

That must have been cool. I wish I had been there :-)

spazgadget (author)I_am_Canadian2011-10-28

I accidentally fired off the V4 inside, and it put a dent in a SOLID BRICK WALL! Here's a pic:

TheBatchies (author)spazgadget2013-04-13

I call absolute BS. No way in hell a toy can go through a wall. You just took a few brick inches and put the, on a rug.

K'nex isn't really a toy anymore. If you look at some of the things it can do, with the right design and the right power, you would be absolutely astonished. I've had a K'nex gun that went straight through 3 soda cans and out the other side, completely destroying the cans. K'nex is a toy, but has the potential to become a deadly weapon.

ralphkidsguns (author)spazgadget2012-01-03

wall is shocked as to why you would shoot it?

I_am_Canadian (author)spazgadget2011-10-28


spazgadget (author)I_am_Canadian2011-10-28

indeed. i can only hope that when i finish this one, my cat doesn't stroll into the room and knock the trigger! KABOOM-SKI!

i used 80-something bands...
i modded the bow to have more torque, and i changed the barrel to have less friction. THEN i added WD-40 onto the barrel (a lubricant oil) and fired.

Power: it went through a fence, and out the other side, still going fast...

range: miles. and miles. and miles.

overall: absolutely f**king AWESOME!!!

Videos!? I want to see it, sounds fantastic!

knexinventer made it! (author)2014-02-02

Here is a pic of the one i built from this instructable.

cookwthebest92gs (author)2014-01-25

I just finished this build and love it!

soccer9112 (author)2013-04-05

Who has built this cannon yet? If anyone has built this yet please put a pic up.

Mace! (author)soccer91122013-07-30

I built it years ago. I have a picture somewhere but on a different computer.

BleSam112233 (author)2012-08-01

It is so amazing how you can just sit down and make this from scratch... or your imagination.... but imagination sounds wrong...

Cheers my friend :-) My origional ideas generally need quite a lot of refining before they are presentable though..

Well, it does feel good to sit down with your K'nex and make something from scratch and get it right the first time.

Certainly, but for me at least, that doesn't happen often.


knexerr (author)2013-06-12

I gonna build this thing and i have al de peaces, i am sure of that. But i don't no what he meens with the light and grey connectors and te tan cap things. Please help me somebody. With pictures is the handiest.?

knexerr (author)2013-06-12

Wich part do you meen with the tan cap, the light grey connectors andvthe dark grey connectors???

danielhone9 (author)2013-04-08

I wanna build it as its epic but I haven't got the pieces

soccer9112 (author)2013-04-05

who has has built this cannon yet?

cinnes1 (author)2013-03-29

In the parts list you havent included white connectors? Hom many would i need?

I_am_Canadian (author)cinnes12013-03-31

Ahh, I always miss something.. My guess would be around 20 or 30.. If you have enough yellow and 3d connectors, you WILL have enough white connectors though I am certain.

petey2000 (author)2013-03-25

how smart are you

OZKNEX22 (author)2013-03-08

Same I'm on this step

OZKNEX22 (author)2013-03-07

My fingers are killing me right now

dozer789 (author)2013-02-10

Wow, cool gun! I am going to build it sometime soon if i have the pieces, -_-. 5 Stars!

I_am_Canadian (author)dozer7892013-02-10

Cheers! Let me know if you do end up building.. Best of luck!

dozer789 (author)I_am_Canadian2013-02-13

I am going to build it sometime when i count and inventory my K'nex pieces so i know how many of every kind of piece i have so i can figure out if i can build things a lot faster.

About This Instructable




Bio: K'nex is my thing!
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