Without having the proper engineering tools such as a CAD designer, 3D wireframe simulator, lasercutter, waterjet, exotic titanium and carbon fiber parts, metal fabrication shop, and a wind tunnel, I proceded to make this using my frugal material of choice, box cardboard from the recycling bin, a bunch of washers/nuts/bolts, glue, a wood dowel and a bunch of spare paint stirrer sticks gotten free everytime you buy a pail of paint. I'm sure you could substitute K'nex parts here or do a steampunk version but this one is my Instructables Robot entry for the Flower contest inspired by the contest Robot itself.
Step 1: A body of work, get jiggy...
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.