When it comes to weight, the sort of mentality “Is the juice worth the squeeze” doesn’t really apply. Every little bit counts- do you use washers on your fasteners?- you don’t anymore! Can you replace a bolt with a rivet or a nylon bolt? - then do it. All these little things add up very quickly so go get your drill and a 1/2" or 9/16" drill bit and have at it! Don’t forget your deburring tool.
We removed substantial weight with 3/16 drill holes this year, almost 8000 in total. There are also about 500 2 inch diameter holes on our robot. Total weight savings were something like 10LBS, I guess it worked as this is our lightest robot in years.
To lose some weight this year, we’ve started pocketing. For those unfamiliar with the term, its basically using a mill to turn thick metal into thin metal in selected areas. It looks great, and is much more effective than normal cheese holing, because you can remove a lot more metal without greatly compromising structural integrity.
Depending on your construction methods, some simple tricks can net you some big savings. Switch any 1/8" wall tube to 1/16" wall. You’ve essentially saved 50% of the weight of the tube. Go to smaller fasteners/rivets/velcro where possible. Decorative Panels and or Protective shields don’t need to be 1/8" Thick Lexan where 1/16" or even thinner will suffice. Depending on the hardware you use (This is most useful when dealing with a lot of larger fasteners, 1/4-20 or above) cut any excess threads off of bolts - no need to have 1/2" of threads sticking out of the nut.
Much of that advice is taken from IKE’s paper, but some if from personal experience. Your results may vary.
A couple of our students over the years have played ice hockey and donated their broken carbon fiber sticks instead of trashing them. Occasionally a section of it makes an appearance on a robot, just make sure it doesn’t take an impact from the wrong direction!
The entire roof assembly of our Breakway bot was carbon fiber stick as the ridge with a piece 1/32 Lexan riveted to it.