Introduction: K'nex AST Rifle
Special Rifle Design Featuring Rapid-fire Capability
Weight: ~500 grams
Ammo Type: 13 centimeter Red Rod
Range: 10 meters
Firing Interval: 1 second
Mag Capacity: 17
Mag Reload Time: 20 seconds
Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.
Step 1: Gather Materials
- 20 White
- 31 Yellow
- 11 Green
- 6 Red
- 20 Orange
- 3 Light Grey
- 13 Grey
- 8 Brown
- 1 Grey
- 23 Red
- 10 Yellow
- 4 Blue
- 48 White
- 65 Green
- 1 rubber band (works best with one from head of broccoli)
- 3 doubled regular rubber bands. (Twist to "8" and down to double)
- Tape (clear)
Step 2: Side Layer Template
This shows the side of the gun without the center layer, which is the next step. Do not start building this layer, but use this as a reference to attach pieces to the center layer.
You will need 2 of these for the sides of the rifle.
Step 3: Construct Center Layer
Begin building this center layer. This is the lower portion of the gun barrel. If you plan on using this gun for a long time, you may want to cover the marked portion with 3 layers of clear tape. Over time, the firing pin will cut into the joints of the pieces. You may start putting down tape from the right side up to the yellow piece.
Step 4: Combined Layers Template
This diagram shows the position of the three layers. Do not start building the layer from Step 2 yet.
Step 5: Combine Layers
So you probably figured out why I suggested not building the side layers. Now you can easily attach the connectors from the side layers to the white rods.
Step 6: Construct Firing Pin and Trigger
See notes for construction details.
Step 7: Complete Trigger - Top View
Top view of trigger once attached to frame. Note the brown hubcap connectors used to secure the ends of the blue rods.
Step 8: Construct Lower Trigger
Once you have completed the upper portion, begin construction of the bottom of the trigger. Put a blue rod through the greys that are attached.
By now, the trigger should act like a hinge if correctly constructed. It should be able to move up and down, with the red connector stopping on the barrel but moving freely upward.
Step 9: Trigger Unit
Attach this unit to the blue rod space from previous step.
Step 10: Attach
Attach the unit built in Step 9 to the space on the blue rod in Step 8.
Step 11: Final Components
Attach the rubber band, brown hub cap connectors in front of the magazine, and firing mode toggle. The toggle consists of an orange connector with blue rod. Grey and brown connectors attached to rod vertically.
Step 12: Use / Troubleshooting / Mods
The grey and brown connector under the trigger serve as the firing mode toggle (must point down).
1. When both are pulled back, the trigger will not drop down. This is the rapid-fire mode, which allows the user to discharge the weapon repeatedly.
2. When both are pushed forward, the trigger is able to drop down once the firing pin is pulled back far enough. Once it drops, slowly release the firing pin. Now the weapon can be discharged any time by pulling the trigger. Do not suddenly release firing pin as it may damage the pieces.
1. When pulling back the firing pin, it abruptly stops/jams.
1. This is because the K'nex rods have grooves in them. When the bullet and firing pin are pulled in opposite directions, the grooves will cause it to jam. This can be fixed by taping the front of the firing pin. Ensure the tape is smooth.
If you are confused, take two rods, pull against each other and notice how they stop near the ends because the grooves stop.
2. The lowest orange connectors on the magazine are always breaking.
2. This is because when you pull the firing pin, you are pushing down to far. The firing pin is now crooked and upon release it hits the magazine instead of the bullet. This will only happen in rapid-fire mode.
3. The bullets aren't even making it out of the barrel! I hate you, faust, your gun is horrible!
3. You might have built the rifle incorrectly, or you are using weak rubber bands. Find the suggested rubber band or half twist 3 regulars to compensate. Attach regulars so they are taut before the pin is pulled. Also try the mods.
4. Rubber bands often break.
4. See rubber band suggestion in #3.
1.Fold paper and stuff it between the lowest orange connectors of the cartridge. Tape it up to secure. The firing pin will sometimes hit the connector and over time will cause it to break. This will prevent the orange connector ends from breaking.
2. Also tape the back region so the firing pin will not cut into the pieces. Notice the damage caused at the orange/green joint. Alternatively you can tape the entire length of the barrel.
3. Note the yellow connector of firing pin. Somehow smooth the back by paper stuffing or something so the rubber band will not be unevenly stressed when pulling back. Will lengthen life of rubber band.