The Shortbow: a K'nex Nerf Crossbow Pistol

This is just something I made for fun a while ago that I thought I'd share. It's not as fancy as some of my previous bow designs, but it's still fun to use. It is a lot smaller and easier to load than my other designs so far, which makes it work pretty well as a sidearm.

Supplies

Connectors:

White: 1

Yellow: 18

Green: 10

Red: 5

Orange: 12

Gray single-slot: 2

Rods:

Green: 26

White: 11

Blue: 9

Gray: 2

Other:

Small wheel hubs: 2

Blue spacers: 4

Y-clips: 8

Rubber band: 1 - about 3" unstretched

Elastic string: 1 - about 30" unstretched

Step 1: The Firing Rail and Trigger

The crossbow starts with the firing rail. The trigger is integrated directly into the rail this time, so it's easier to condense the two parts into a single step.

1. The rail starts with these two center pieces and a pair of blue rods.
2. The pieces connect as shown. The two Y-clips will go on the front of the crossbow.
3. These are the outer rails.
4. An extra blue rod will be needed for attaching them.
5. The green rods on the back will be used for mounting the trigger.
6. These components form a ratchet wheel that will hold back the bow.
7. Here is the wheel.
8. The ratchet wheel will go on the back of the rail.
9. Here is the assembled firing rail.
10. The trigger begins with the components shown here.
11. The direction that the white rod and red connector are facing is important.
12. The green connectors will go on those green rods from earlier.
13. Here is the assembled system. If you flip the trigger over, the red connector should engage the white connector like a ratchet.
14. Here is a side view of the trigger.
15. These orange connectors will be used to attach the grip.
16. Here they are assembled onto the rail.
17. These will make loading the bow a bit easier.
18. Attach them to the back of the rail so that the bow can only go over the top of the ratchet.
19. This is what it should look like at the end of this step.

Step 2: The Handle and Some Structural Reinforcements

Here is the crossbow's grip and a few extra frame reinforcements. The reinforcements aren't strictly necessary, but they do make it stable, and they look nice.

1. The handle begins with these pieces here.
2. These pieces assemble to form the outer sides of the grip.
3. The blue rod on top connects to the orange connectors on the rail, and the white rods attach to the green connectors.
4. Here is the outer grip attached to the trigger mechanism.
5. Here is a back view of the connection.
6. The inner grip consists of the two pieces here.
7. They will go between the outer grips to act as spacers. The yellow connectors will keep the trigger from collapsing all the way into the grip.
8. Here they are attached to the grip.
9. Attaching a blue rod across the back of the grip will hold it all together.
10. These connectors will form part of the structural frame under the rail. Both sides are identical. Attaching the green connectors first makes the connection easier.
11. After the connectors have been attached, the blue and green rods will complete the frame.
12. Here is the completed structural frame.
13. Here is what the crossbow should look like at the end of this step.

Step 3: Finishing It Up

Here we add the bow and string it up.

1. The bow begins with these two pulleys and the gray rods.
2. Here is the assembled bow.
3. One of the gray rods attaches to the Y-clips on the front of the crossbow.
4. Here is the assembled crossbow frame.
5. Here is another view of the assembled frame.
6. Stringing the bow begins with a slipknot tied near the end of the elastic string. Make sure it is tied so that pulling on the long end of the string tightens the loop.
7. Put the loop over one of the white rods on the underside of the bow and pull it tight.
8. The string will loop around the bottom of the crossbow to the other pulley, then across the top of the firing rail, around the first pulley, and back to the underside.
9. Tie a slipknot in the other end just like before, pull it around the pulleys, and attach it to the other white rod.
10. When the knot is pulled tight, it should look like this.
11. Here is the bow after it has been strung up.
12. The small rubber band starts around the back of the trigger.
13. The other end of the rubber band goes over the yellow connectors in front of the trigger.
14. Here is the trigger with the rubber band on it.
15. To load the bow, simply draw the string across the wheel on the back and place a dart on the rail in front of it.

I hope you like this, and I hope you have fun.