This is a concept for a k'nex mine, meaning that it doesn't fire anything right now, but it is easy to modify it to fire k'nex pieces.
You will need:*
3 Blue Spacers
1 Tan Lock
1 Small Wheel
*All Numbers Approximate
**I didn't Know what to call these, they are often used as hands for the people
Step 1: Base
The first pic is the finished base, and the second pic is a close-up.
Step 2: Base Cont.
The first pic is the finished base, the second pic shows the rams. You will need a total of 8 rams.
Step 3: Top
Pic 1: The top
Pic 2: I don't know what to call it but it's really important
Pic 3: The bottom of Pic 2, note the tan lock
Pic 4: Putting Pics 1 and 2 together.
Step 4: Putting the Top and the Base Together
Attach the red connectors from the top to the green rods on the bottom. The other two pics just show that you need to attach the rams to the really important piece.
Step 5: Another Important Piece
Pic 1: Make this piece.
Pic 2: Attach Pic one to the pieces in Step 4
Pic 3: Make this piece.
Pic 4: Attach Pic 3 to Step 4.
Pic 5: Continuation of Pic 4.
Sorry about the blurry pics.
Step 6: Finished
It should look like this. Add rubberbands to the ram, white rods to the bottom of the base, and a string from the Really Important Piece to the Another Important Piece.
And for those of you who want to criticize Knex in general, don't, there won't ever be enough Knex guns or instructables so don't ask. Okay. I take that back. There are too many of the same kind. I never thought I would see the day......