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.
Step 2: Flower Power
Use a drill to put a pilot hole the diameter of your dowel in the center of the back of your flower. Glue a small section of dowel into the flower that will become the driveshaft. It will be trimmed to fit later. I used a polyurethane glue (GorillazMiko brand...not really) because it expands and cures rigid providing support for the shaft. You can still use a big blob of white/yellow glue instead.
CAUTION: Use latex/rubber gloves when working with polyurethane glue. That GorillazMiko glue goes everywhere. It sticks to everything and you cannot get it off your hands and everything else you touch trying to get it off. It's still a favorite though.
When the glue is dry, get your special helper to paint the fanciful flowers. When the paint is dry, bend the flower petals in a deliberate pattern going the same way all around to simulate a propeller or pinwheel.
Paint your paint stirrer green which will be the "stem" of the flower. Drill a hold to accomodate the flower driveshaft. Use sandpaper/file/drill to make the hole just a tad larger so the flower spins freely in it.
Assemble the flower drive as shown in the pictures. You want to sandwich the cardboard with washers where the bolts go through. Build up spacing with a nut and a washer. Use more polyurethane glue to atttach the drive wheel to the flower axle. Saw off the excess length of dowel protruding in the back so it will not bind against the drive rod later.
Step 3: Time to tune this Harley...
Put the parts together and leave the last nuts on the bolts a little loose so you can see if it moves correctly and make any adjustments. You will need to attach the "flower stem" to the body so that the flower driveshaft is somewhat level with the drive bolt on the head part. Just attach one bolt to the flower stem on the body so that it can pivot as you make adjustments.
Try to spin the flower and see where you will have to mark out and drill out a slot for the headbolt. If the head drops too much to the side, just glue up stop pieces to limit its movement.
When everything turns, the head moves correctly from side to side and nothing binds, fix the position of the flower stem by drilling a pilot hole and attaching the second nut/washers/bolt.
I used lock washers in some places but it is easier to add a drop of polyurethane glue on the bolt thread to lock it in. Your whirlygig would disintegrate as the vibration and movement tends to loosen the nuts.
You can then attach everything to a garden stake or pole so that it can rotate like a weathervane to catch the wind. For demonstration purposes, I stuck a U-shaped wire staple used for staking out weed control ground cloth in the bottom so I could stand it up in the soil.
Step 4: Time to take it out for a little spin...
I think my flower petals should have been larger or needed to have the pinwheel shaped scoop to catch the wind. The single layer cardboard fins didn't hold up to being shaped after being painted. Plastic vanes would have been better. If you plan on leaving this thing outdoors, you should dunk everything in polyurethane clearcoat to water resist it before it is assembled.