Puncher battles are a fun classroom activity that guarantee that students will innovate to win! By tuning the bar lengths of their puncher's 4-bar linkage, students can take advantage of "inverse leverage" to throw fast punches to knock their opponent's block off.

Step 1: Before Finishing Your Build, Tune Bar Lengths to Optimize for Punching

The above bar ratio of 2:4 means the fist's speed and distance traveled increases significantly

Step 2: We'll Build a Puncher in Stages, Starting With Bar 2

Step 3: Here Are the LEGO Technic Parts Used

Step 4: Assemble Bar 2

Step 5: Assemble Bar 1 (the Handle), and Add Bar 3

Be sure to use the yellow frictionless pins for joints designed to move!

Step 6: Add Bar 4

Step 7: Add a "Block" for Your Opponent to Knock Off

Step 8: Optional: Motorized Punchers

Punchers can also be motorized to make "battle bots". This can be done by programming a servo motor to do a partial rotation, or by adding a crank and a 6th bar as is done in the video above.