We’re using 0.188" nom. (3/16") Lexan cut on a bandsaw. Substitute any ol’ saw for a bandsaw. Don’t saw too quickly or feed too slowly or, as with a wide majority of plastics, it will start to melt and gum up. Easy peasey.
12 mm birch plywood. Cuts nice with a table saw. Screw the electronics parts down with wood screws. Quick and easy. If you need to drill a hole, the shavings are non-conductive. We used it even back when we used to make the rest of the robot out of metal. We do sometimes do some cutouts or partial cutout/rib patterns with a router.
We like to have a solid surface on the bottom of the robot when there is any chance it could be tipped over and another robot could run into the bottom, like this year. I’m toying with the possibility of cutting a set of ribs out next year on a CNC router (if I can find access to one) and then fiberglassing it. It will depend on the game and on what the weight / cost / hassle trade-off analysis ends up saying.
Most people use waterjetted aluminum, which is then sometimes powder coated. I think it is probably 3/16 or 1/8 aluminum.
My team, on the other hand, is using black carbon fiber honeycomb (1/4" cell width). it comes sandwiched between two other peices of carbon fiber. it is very strong, light, and you can mount electronics right to it because it isnt conductive. be careful though, you must use VERY big washers when mounting to it so you dont pull the bolt right through it.
My team mounts electronics with Velcro on a 1/8" plastic base plate (I’m not sure if it’s ABS or polycarb off the top of my head). This year, the plastic plate was held to the frame with more Velcro and (rather ugly) plywood struts to keep it from flexing.
By “Belly Pan”, I assume you mean to put electronics on?
We tried some 1/8" aluminum laser cut for us (rev A had serious warping, although rivets fixed it. They built a fixture of some sort for rev B). It works pretty well if you use nylon screws to attach your electronics. I hear the new cRIO is coated so that it’s non-conductive, but it’s fairly easy just to toss a thin sheet of plastic underneath. We had to cut out our belly pan due to weight constraints though, and now our electronics are sitting on some 1/8" lexan.
If you don’t have access to waterjet/CNC facilities, you could just stick a thin aluminum plate on the bottom. The NERDS used .060" Aluminum for a bellypan in 2008; nice and sturdy with lots of real estate to attach stuff.
1/4" plywood works wonders, lightweight and cheap! currently my material of choice for something like an electronics board/bellypan. We’re sporting quite a bit of plywood on the Falcons’ robot this year.
We use a material called verolite which is what greenhouses are made out of, it is essentially corrugated polycarbonate. We choose this material for several reasons
.5 inches thick (roughly) means that despite being incredibly light, it has excellent rigidity.
2.17 per square foot from our supplier makes it substantially cheaper than other materials.
It is non conductive, machinable with wood shop tools, doesn’t splinter or crack(it is spry enough that it would take an enormous amount of force to reach its ultimate yield point.
our dual belly pans(one on top of the other) weigh < .1 lbs each, and the 15mm thick variety of verolite that we use is stronger than half inch thick particle board by far, and although it flexes more it has higher ultimate yield properties than almost any type of plywood.
This year almost 2 full 4*12 sheets made it onto the robot.
FRC2168 has been using this stuff the last few years: McMaster 84825K89
I learned about it while at college with FRC229, they used it for their ramps back in 2007. It’s listed as Noncorrugated Panels, is about 1/4" but the stuff is super light weight and can handle a good amount of weight.
Note: I’ve heard it called Polygal, but I believe that is the whole Kleenex vs tissue paper argument.