I made mine at http://techshop.ws
some two inch thick lumber, I used some scraps of 2x6 that I had lying around.
some large wooden dowel for the handle. I used 7/8" diameter.
some small wooden dowel for the axle. I used 1/2" diameter.
some leather or rubber scraps for the feet.
Jigsaw or bandsaw
drill bit the same size as your large dowel (forstner bit recommended)
drill bit the same size as your axle dowel
drill bit slightly larger than your axle dowel
compass to draw circles for the wheels
Step 1: Sketch and Cut Out the Pieces of the Duck
For aesthetic purposes I prefer the material of the wheels to be around 2/3rds the thickness of the body of the duck. If you're using the same raw material for both, now is the time to plane down the thickness.
The head and body need to have flat pieces where they will touch so that they can be securely glued, but the rest of the design can be free-handed.
When you're satisfied with the outline of your pieces, cut them out using a band saw. Leave a little bit of extra material around the outside of the wheels in anticipation of the next step.
Step 2: Get the Weels Round
If you DON'T have a wood lathe, the wheels are nearly impossible to cut into exact circles without a jig of some sort. Some people have good luck using a jig to rotate the wheel on the bandsaw, but I used a belt sander to round out the rough-cut wheels.
First, using a drill press to ensure a vertical hole, drill the hole for the axle in each wheel, sized so the axle would be a tight fit for the dowel. To preserve a nice exterior finish on the wheel, drill a pocket hole instead of drilling the whole way through.
Next we'll make an 'arm' piece. Find a piece of scrap wood longer than the radius of the circle and drill a hole through it just slightly larger than the axle dowel. The dowel should be able to turn without much effort, but should not be a close enough fit that it doesn't wobble in the hole. The tightness of the tolerance here will directly influence the roundness of your wheel.
Make a base for the arm by taking another piece of scrap wood that's slightly thicker than the thickness of the wheel and clamp the arm to the top of it. The bottom of the clamp should be under the lip of the table, holding the arm and base in position. You should now be able to slide a wheel underneath the arm with the axle hole facing up. Align the hole in the wheel with the hole in the arm and drop a dowel through the arm and into the wheel. You should now be able to spin the wheel in place without it moving around on the table.
Using this armature you can move the wheel towards the sander until it just barely begins to sand off material. Once the wheel is in contact with the sander, spin the wheel in place, removing all material at a uniform diameter. Keep removing material in this fashion until the wheel is the desired diameter.
Repeat this process for the second wheel.
Step 3: Prepare the Duck Body
Both of these holes need to be well aligned or the duck will drift to one side or the other like a bad shopping cart, and makes for a lousy toy.
Drill a hole near the bottom of the duck for the axle. It should be at least half an inch away from the bottom to be strong enough to not break when getting thrown around. It should also be positioned so that the duck can tilt forward and backwards a significant amount without bottoming out on its tail or chest so it can keep rolling through wide range of motion. You may want to adjust the outline of the body while determining he axle placement.
The angle of the hole for the handle is also something that should be considered. If it is too steep the toy will tend to get stuck on things like carpet edges since some of the child's pushing force is in the downward direction. However, too shallow an angle will put the toy too far ahead of the child for them to steer it easily. A 35 degree angle works quite well. Another item of consideration for the hole for the handle is where it should attach to the toy. I designed mine so that the handle points directly at the axle, directing all the mechanical force to the wheels as directly as possible. My theory was that pointing it higher or lower would cause the handle to 'kick' either up or down when the toy ran into something, possibly wrenching it from the child's hand.
In order to drill the hole at a totally weird angle in a totally weird shape, I took two 2x4s and clamped them to the sides of the body so the direction of the hole I wanted to drill was straight down. I could then clamp that entire contraption to the table of the drill press to hold it in place while I drilled the hole. I used a forstner bit instead of a spade bit. They just seem a little bit more precise, and deal better with an odd entry-angle.
Once the holes have been drilled, you may want to briefly revisit the belt sander to add a slight taper to the sides of the neck, just to give it some visual separation from the head once they're glued together, even though the pieces they're cut out of are really the same thickness.
Step 4: Add Feet to the Wheels
Draw a duck foot on a piece of paper. You may find it useful to slide the paper into the slot you cut on the wheel in order to give you an idea of how much material needs to be inside the wheel vs outside the wheel. Remember that the foot does not need to be confined to the width of the wheel, but can extend towards the outside of the duck. It cannot, however, encroach on the space between the wheel and the body of the duck or the wheels will bind.
Once you have drawn a foot, cut out that template and trace it onto a piece of leather or rubber. Flip the template over and trace a second foot. The two tracings should be mirror-images of each other. Cut them out. Pro tip: when cutting the feet, leave the material quite a bit wide where it will be at the back of the slot. This will give you something to grab onto when you're trying to pull the foot all the way to the back of the slot. Once the foot is seated and glued in place you can trim off the extra.
Dry-fit the feet to the slots. They should be pretty snug. If the slot is not wide enough for you to pull the material into it, you can use sandpaper to widen it. Fold a piece of sandpaper in half and run it back and forth in the slot. If that doesn't widen it enough, slide a piece of paper into the fold of the sandpaper, making it thicker. Keep adding paper as needed until you've widened the slot enough to nicely accommodate the feet.
Squirt a small amount of glue into the slots and insert the feet. Let dry. Trim off any of the foot material that hangs out of the wheel on the side that will face the body.
Step 5: Glue It Up
Once the glue has dried on the head, move on to the wheels. Cut a piece of dowel for the axle. Drip a small amount of glue into the hole of each wheel and spread it around with a toothpick to get good coverage. You don't want a lot of glue squirting out of the hole when you put the dowel in, or you'll end up with your wheel glued to the side of your duck. No fun. Thread the dowel through the body of the duck and then press a wheel onto each side. Make sure the wheels are on the correct sides with the feet facing the proper direction. Rotate the wheels in relation to each other so that the feet are pointing in opposite directions, i.e. when one is pointing straight up the other is pointing straight down. You can put some paper between the wheels and the side of the body as a spacer during the glue-up to ensure that you don't push the wheels too far onto the axle, pinching the body and causing the wheels to bind when they spin.
Once the wheels have dried, glue the handle into its hole as well. Before the glue dries, make sure the handle is perfectly lined up with the direction of travel. A mis-aligned handle will lead to a frustrated child whose toy keeps drifting into the wall.
You can probably overlap some of these gluing procedures, but keep in mind that the head will be easily disturbed while it dries, and its clamp will likely be in the way of installing the wheels.