I thought about cutting out the main shapes from hardboard/masonite or thin plywood but that involved getting out the heavy power tools and making a mess. I saw a few instructables on people layering cardboard to use as a building material so I thought I would give it a try. It turns out to be inexpensive, strong, and easily cut and shaped such as forming it for the drive parts. Don't worry about exact tolerances in cutting out parts or the diameter of the holes we drill. We are making this up as we go along. This is afterall cardboard we are working with, we're not building a Bimmer.
Get a hold of the Instructables Robot graphic. Print out the large image of the robot which can be found here
. Print out two copies with the image scaled to fit a regular letter or A4 page.
Trim around the pictures so that you can glue it on a layer of cardboard. On the first picture, trim off the head. One the second picture, trim around the head but keep an oblong section below it where the pivot and drive bolts will attach.
After it dries, cut that out from the cardboard with a razor knife or strong utility shears. Trace the shape again on cardboard. You should try to change the orientation of the grain of the cardboard(the direction the internal ribs or ridges are running) as you trace the new part. Glue or laminate this to the first layer. For the main body, add on two more layers so it is four layers thick.
If you use scrap cardboard from IKEA boxes, you may want to add on one or two more layers for thickness and strength. We need all the layers for the proper spacing of the mechanical linkage. When the grain of each of the layers go in a different direction, it adds to the strength the same way they manufacture plywood.