This is a simple yet effective knex grenade that when thrown fires blue rings up to a radius of 4 metres.

Step 1: The Pieces

You need:

5 yellow rods
6 blue rods
4 white rods
20 green rods

3 white connecters
12 green connecters
12 grey connecters
2 orange connecters
2 black connecters
1 sphere connecter

some blue rings
rubber band

Step 2: The Base

Just basically make whatever is on screen it is pretty self explanantory.

Step 3: The Middle

Now just connect the green connecters to the sphere like how it is done in the picture.

Step 4: The Middle

Make this star type thing and then slide it down the blue and yellow rods like in the picture.

Step 5: The Top

Now for the top and the hammer, the picture is pretty clear, just follow it

Step 6: The Grenade

Now all you have to do is connect the top to four of the blue rods and slide the hammer down the middle with the two guide rods slid down the side yellow rods aswell.

Step 7: The Finale

Now just add the rubber band from the top to the hammer. To load it up, hold the hammer down with one hand and with the other insert the blue rings onto the middle rod. To stop it from firing, place a orange connecter to jam it in place. To fire it turn the orange connecter till it almost pops off then just throw it on the ground and the force of the hit should set it off.

Good Luck