Reaper Crossbow




About: I seem to like building crossbow shaped objects.
So here it is, one of my greatest crossbows ever (V5 in the series), it employs four rubberband strings, which uses a completely new double trigger system, which holds arrows that are at full power and if one wants a little less power, one can lock two arrows in the trigger and use 2 rubberband strings for each arrow.

The absolute full power of this monstrosity is reached by removing the trigger system, which enables it to use 4(!) arrows, which it can fire in a rain of doom (One could call it a repeater crossbow actually). And if one does not use the trigger one needs to put the Reaper on your arm, otherwise it is too heavy to hold on to with one arm.

The distance it fires outside is like most long range knex guns very dependent on the wind, if the arrow has a good tailwind it can get ~200 feet without trigger.

Don't forget to rate :D
Enough talking, now get building :o

A video of the Reaper shooting at chipwood.
It pierces straight through it is not cardboard :D

Step 1: The Pieces List

Minimal Pieces Needed:


Blue 3d connector: 88
Purple 3d connector: 60
Yellow connector: 51
Red connector: 8
Green connector: 4
White connector: 16
Light grey connector: 10
Orange connectors: 18
Grey connectors: 2


Green rods: 113
White rods: 130
Blue rods: 82
Yellow rods: 6
Red rods: 29


Wheels: 8
Blue spacers: 12
Grey spacers: 8
Rubberbands: 12

Recommended Pieces Needed:


Blue 3d connector: 88
Purple 3d connector: 60
Yellow connector: 73
Red connector: 12
Green connector: 10
White connector: 16
Light grey connector: 10
Orange connectors: 24
Grey connectors: 2


Green rods: 117
White rods: 161
Blue rods: 94
Yellow rods: 22
Red rods: 33
Grey rods: 6
Bendy grey rod: 6


Wheels: 8
Blue spacers: 12
Grey spacers: 8
Rubberbands: 16
Small panels: 6

And ofcourse "some" extra pieces for arrows.

Step 2: Building the Bow

Only build what is centered on the picture and I will use a letter system to help putting it together.

Picture 1: Start off by building this 1st lower bow part(A) Don't forget the green rods on top!

Picture 2: Build this 2nd lower bow part(B).

Picture 3: Build these higher bow parts(C).

Picture 4: Add the parts A and B together. Which is now called AB.

Picture 5: Add a red rod to the part AB.

Picture 6: Add these blue rods to the part AB.

Picture 7: Add the parts C to AB as shown.

Step 3: Rubberbands Onto the Bow

This step is pretty frustrating, because putting on 4 strings of rubberbands is very hard ( Needs to go one by one unless you are good with knots :D ).

Picture 1: Add these to the bow (ABC).

Picture 2: There are 4 rubberband strings here, one is already on the bow.

Picture 3: Pick up one string of rubberbands and force them behind the wheels and put them onto the blue rods, do this 4 times and on both sides.

Picture 4: This is how it should look like.

Be very careful with the rubberbands....unless you liked this step alot :).

Step 4: Building the Handle

An easy step to recover from the last one :P

Picture 1: Build these outer two parts (D).

Picture 2: Build the middle piece (E).

Picture 3: Connect the white rods of the outer parts (D) to the middle part (E).

Picture 4: Add all the red rods (to DE) as shown on this picture.

Picture 5: Connect the handle (DE) and the bow (ABC) to each other as shown in the picture.

Picture 6: It should look like this.

Step 5: The Trigger System

Picture 1: Build these parts (F).

Picture 2: Connect the parts (F) like following.

Picture 3: Same as picture 2.

Picture 4: Build this part (barrel) (G).

Picture 5: Same as picture 4.

Picture 6: Build these two triggers (H).

Picture 7: Same as picture 6.

Picture 8: Add the triggers (H) to the barrel part (G)

Picture 9: Two triggers connected (GH)

Picture 10: Build these little parts.

Picture 11: Add them to (GH).

Picture 12: Same as picture 11.

Picture 13: Put a rubberband here.

Picture 14: Sorry for blurry picture, just fit as many red rods as you see fit (to part F), but don't forget the marked ones. And don't forget to put the trigger (part GH) in :P

Picture 15: Same as picture 14.

Picture 16: Connect the trigger (GH) to the handle (DE), which is connected to the bow (ABC).

Step 6: Extra Support and Decoration

I would recommend building the extra support, as I haven't used it without it :P

Picture 1: Build these pieces for decoration.

Picture 2: Attach them like so to get a very clean looking crossbow :D

Picture 3: This is the extra support. I am not sure, but I think one can change the bendy rods for normal rods.

Picture 4: Attach them like so.

But what's that? There is more? Go to the next step. :P

Step 7: Types of Ammo and Loading

Wow, it can fire too! :o

Picture 1: Read the markers to see their power and speciality.

Picture 2: How a standard ordnance trigger arrow is loaded.

Picture 3: How one loads two standard ordnance trigger arrows at the same time.

Picture 4: Where to snap off the trigger.

Picture 5: How to hold without trigger.

Picture 6: How to load a multi arrow shot.

Picture 7: Fully loaded and ready to do some nasty damage :P

I am not liable for any damage you cause with this massive thing and never fire a piercing arrow at living creatures as it may pierce through flesh (Not going to test that lol..)



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      Leather Challenge
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      Pie Contest

    293 Discussions


    8 years ago on Step 2

    Hello i know this is very old now but i was wondering if the grey spacers = 3 blue spacers because when i put from bottom to top with the wheels like this if it is correct 1 grey spacer, 3 blue spacers,2 wheels, 2 blue spacers, 2 wheels, 1 grey spacer, 3 blue spacers. When i try and connect part ab and c together it doesnt fit help thanks

    3 replies

    Reply 8 years ago on Step 2

    Wow, I took bad pictures ;x

    Bottom to top:
    2 grey spacers
    2 wheels
    2 blue spacers
    2 wheels
    1 grey spacer
    3 blue spacers

    Its a 'red' rod in size.
    4 wheels
    3 grey spacers
    5 blue spacers


    Reply 8 years ago on Step 2

    Thank you for replying so quickly I had it in the order you said but when it's put together ab + c with the red rods with stuff between it, doesn't clip together because it's to big I have taken out some spacers to make it fit also what size rubber bands did you use thanks once again


    Reply 8 years ago on Step 2

    These rubber bands did not have any size rating, just cheap standard ones.

    You want rubber bands that are pretty thin, the length does not matter, as you may make the handle longer to compensate for longer rubber bands.


    10 years ago on Step 5

    omg, can you please update pictures 10-15, cos I have absolutely no idea how to put the trigger bit onto part F

    2 replies

    Reply 10 years ago on Step 5

    I am sorry, but have you seen when I made the instructable? By now its already taken apart...and why didn't people complain before?...Onky option is to look more carefully =/


    8 years ago on Introduction

    is it possible for me to build this with less wheels ( i only have 4 :( )

    other than dat nice gun!

    blak jeroe2

    8 years ago on Introduction

    hey wicky. i made changed my reaper and know it have new abilyties. - new trigger system (1 bullet trigger but it shoots even farther) -handle (so i can run with it easyr and easy for trigger system) - the bow ( it is a lot stronger now i cccan show u the picturres tomorrow

    blak jeroe2

    8 years ago on Introduction

    i made this one to it's fantastic. i killed abird with a piercing arrow. i have add 1 piece it's a standart so "the reaper" that standart make it easier to shoot from te ground. wickky if you agree with it i can let you see. wicky you're fantastic at making knex weapon

    1 reply
    Wickyblak jeroe2

    Reply 8 years ago on Introduction

    Feel a bit sorry for that bird..but its in the name of science! =x Might pick up building again soon, haven't touched knex for at least 4 months.


    8 years ago on Step 1

    this is a awesome crossbow shot through my wall snd i killed a squirel today

    WickyJoseph Mendoza

    Reply 9 years ago on Introduction

    I have build loads of mini versions, just none posted, here is three different ones, 1 after the blockhead, 1 after the reaper and one is just a random one.

    I can make a better one as soon as my k'nex is unpacked from moving =/

    P.S.: It would be hard to make it smaller than #1 though =o

    100_4796 (Large).JPG100_4740 (Large).JPGCrossbow V4.5 001 (Medium).jpg
    Joseph MendozaWicky

    Reply 9 years ago on Introduction

    could u make an instructable for the mini blockhead.Thats probably the only thing i could make.


    8 years ago on Introduction

    first i want to say this is the best knex gun/ crossbow ever and secondly with the normal arows i put the vertical so i use both sets of bands, it has a crazy whistling sound as they fly through the air