So back when I was working as a Scenic Carpenter I built a lot of stuff from expanded polystyrene foam (which we, like most of the US and Canada, would refer to inaccurately as "styrofoam.") You could usually find pretty big chunks of it, although for larger projects you'd glue several together with wood glue, a caulk gun, or Great Stuff (spray foam insulation in a can).
I'm building up the body of one of the two robots out of foam. But the expanded stuff just doesn't seem to be around, at least not in other than the odd scraps left over from shipping boxes. Instead the local art and hardware stores carry extruded polystyrene, or as I've been calling it of late, "crunchy foam."
It is really horrible stuff. I searched for foam until I found something that looked like it would work, and I committed to this stuff -- thirty bucks of it so far, plus of course sculpting time. I wish I had kept searching. A few days later, I discovered you can get pink insulation foam from Home Depot. I might not have gone that way even then, since I have a rather small space to be handling a full sheet of material in! It wasn't until I had actually worked with it that I realized how horrible it was.
Anyhow. The craft foam crunches. It is way too easy to break, or to dent. It is very bad about glue; most of the glues I tried never seemed to dry and didn't hold well when they dried, either. The cells are large and open; gesso goes right into it. The only thing that seems to be filling the pores is spackle, and I'm using a ton of it. Which is kinda hurting the whole intent of using styrofoam (aka, the light weight).
The body of the first robot is currently a rather sorry looking mass of styrofoam and foamcore board, patched up with spackle and apoxie sculpt (for the larger holes). It looks like it is going to take several coats and a lot of sanding before I get that smooth glossy plastic look I want.
At this point I would lose no more than four hours if I were to throw out the existing robot, buy some pink foam, and start carving a new one from scratch. But it would cost more money, and money and time are both short on this.
The most frustrating part is that everything takes forever to dry. Again the hazards of not having a big shop to work in. In a proper shop, I could be laying out the other parts of the project. But this takes up so much of my available space, and makes so much of a mess, I am loathe to try to do anything else until I can get the body of the first robot completed. And I'm still looking at probably another two days of sanding, spackling, gesso'ing, and waiting for stuff to dry.
And what else is there to do? I might not bother putting servos or other electronics in the first robot. The controller that came with it is a two-channel job and I'd have to create not just a second radio link, but some way for the operator to run both at the same time. If nothing else, that means another battery or a bunch more connections to deal with. And this has to be set up, batteries charged, systems checked every performance for five weeks.
(Of course, I found some LED-equipped iPod speakers that would look just so cute as "eyes" -- but I'd need to take them apart and hack them to work, and they are a little small anyhow, and it might be simpler to make something from scratch...)
I am also not sure I like the look of the Ethafoam bumper I planned to add. It needs the bumper for what little protection it gives, though.
Robot #1 is using a $30 toy car for a chassis (as they say in the business, if it says "remote control" on the box it is a toy. If it says "radio control" is it a hobby class.) It has medium-hard knobby "outdoors" tires, a plastic chassis, a very light and springy suspension, and the controller is non-proportional; you get three choices -- fast, off, and reverse.
Fortunately, one of the discoveries made while investigating-by-building is that when weighted down with my new body, it settles down and seems to be decently controllable. I haven't quite put it to the test by trying to hit the marks at the theater, though...
Robot #2 is planned around a "radio control" chassis. A Tamiya Frog, in fact -- 1980's tech, but it has nice suspension and shocks, the typical Tamiya 540 motor. Unfortunately it is a bit of a stripped chassis. So I have ESC (electronic speed control) on order, I need to put one of my servos in for the steering, and of course I'm still hoping I can get the combination of Vex radio and Arduino to work.
I have no servo saver, and no idea yet what I'm doing about the battery pack. Nor have I tried yet to fit the frame of a new body around it. Robot #1, at least, the body appears to sit nicely enough on top that it will not have to be fastened down (meaning it is easy to pull it off to work on.) But Robot #2 looks like it will be more interesting.
Especially since -- after all, I've got that six-channel Vex to play with! -- it is intended to have the fully pan-and-tilt camera head.
My biggest problem, however, is paying rent while I'm working on this. I told them I was volunteering the labor. I also haven't brought the project to the point where I can get reimbursed for parts and supplies -- if worst comes to worst, and I don't have a working robot they want to use for the show, I might end up eating much of the cost. And that might be all I eat for the month of July!