BeatleBeater Build Log


What happens when the waterjet breaks…

With the waterjet broken until after winter break, one weekend I thought it’d be fun to see how much that actually slows down my robot production speed.

From experience, I found that I could design, waterjet, and assemble a new battlebot in about two days (even school days), with plenty of time to spare.

It turns out milling only slows me down to three days for everything (albeit with a lot more effort).

I’ve always been fascinated by beater bars and it seemed like the perfect type of robot to make on our Bridgeport.

For the beater, I started with a 4″x 3″x 3/4″ billet of  6061 and milled an asymmetric pocket. As usual, I wanted maximum “bite” out of my weapon so it would only have one “tooth”. I used some 3/8″-16 bolts for teeth and for balancing. Balancing was done with a pretty brute force approach in Solidworks. Essentially, I moved the center of mass above and below the axis of rotation by adding/removing less and less material until it was balanced within half a thousandth (more accurate than our DRO).

mmmmm that outside surface finish

The weapon uses 3/8″ ID vex flanged bearings and is belt driven off a Prop Drive 28-30. (pulleys and bearing holder will be made out of aluminum eventually)

The rest of the robot is made out of 1/4″ aluminum we found on a ‘science machine’ (some sort of broken gene sequencer?) the night before I started.

img_0682Before scotch brite




The top and bottom panels were just band sawed/drilled 1/4″ UHMW

The robot worked great and is much lighter than expected, weighing only 2lbs 9 oz. I’ll add this to my army of beetles for Mass Destruction and probably let someone who didn’t finish their robot drive it.


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