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This article is from Issue 70 of Woodcraft Magazine.
Make a mechanical marvel with scrollsawn parts
Creativity comes from all sorts of inspiration. Lately, I’ve developed an addiction for making creatures to match wacky clip-on lampshades for my animated lamps. When I found a shade with palm fronds, I knew that I had to design a project featuring some long-necked herbivore. A pair of giraffes fits the bill nicely.
For me, the scrollsaw work is only a beginning of the creative process. What I enjoy most is giving life to my projects via simple cams, gears, and other shop-made mechanisms. In this instance, a cam and pair of linkages convert a small electric motor’s rotational movement into the gentle side-to-side sway of the animals’ heads and necks.
Scrollsawing the parts isn’t rocket science. (For convenience, PDF files of full-sized Plans and a Cut List can be downloaded from woodcraftmagazine.com.) Assembling the parts so that they work like they should requires some mechanical ingenuity. For this reason, these pages focus on what you’ll need to do after the parts have been cut.
By switching a few parts you can go from the jungle to the Jurassic Period. You’ll also find the patterns for this brontosaurus-themed variation on our website.
Cams spin while giraffes grin
Don’t let the mechanism throw you…if you can saw to a line, you can tame this project. Baltic birch plywood is the best material to use for this project’s wooden parts.
How it Works
With each rotation of the motor’s drive shaft, the outer edges of eccentric cams rise and fall. The linkages ride on top of the cams, converting the cams’ circular movement into the side-to-side sway of the animals’ heads.
Basic Construction Sequence
- Download the full-size patterns and glue them to plywood.
- Cut the parts on a scrollsaw and sand the edges smooth.
- Make the base.
- Paint the parts and skin the giraffes and backdrop.
- Machine the cams and linkages and assemble the lamp.
The paper hide, motor, and hardware needed to make this project are available in kit form. See the Buyer’s Guide on p. 67.
Skinning the beasts
Rather than attempting to paint the giraffe’s spots, I skinned the beasts using animal-print paper purchased from a stationary store. (A sheet of giraffe hide is included in the parts kit. See the Buyer’s Guide on p. 67.) For the backdrop, I searched online for a “jungle image” and printed a pattern out on high-quality paper. The finishing technique I used is called decoupage. This sounds fancy, but I’ve found this method is an easy and efficient way to add detail and color that I couldn’t accomplish with just a brush.
Simply paint the edges and visible faces, and then apply a paper facing to the body parts and backdrop. I prefer making my own adhesive by mixing equal parts white glue and water. (I use the same watered-down white glue for sticking patterns in place prior to sawing. Unlike when using contact adhesive, the patterns rub off easily with a damp sponge.)
While waiting for the paint to dry, I made my base from plywood, pegboard, and cherry hardwood. Since the top will be painted, you can use whatever wood you have on hand.
Paint and stick. After painting the outer edges, brush the watered down glue onto the bare wood, then lay on the paper skin. Burnishing the paper onto the wood with a paper towel works out bubbles and ensures a good bond.
Trim the skin. When cutting the paper flush with the parts, I prefer a mini box knife. For a close shave, extend the blade so that the blade—not the knife—registers against the edge of the part. When trimming the corners, I find that making smaller tangential cuts can be easier than following the curve.
Use tape to tame the paint. Painting the parts before assembly and taping the edges keeps paint from getting where it shouldn’t. Leave the interior faces of the parts bare to ensure a good glue bond.
Making & installing the cams
The double-cam mechanism is where the mechanical magic starts. To ensure the smoothest possible operation, this part must be machined precisely. My sanding and assembly process corrects any discrepancies that might sneak in from an errant saw cut and ensures a perfect glue-up. After assembling the cam, as shown below, drill a hole into the center of the motherboard, and then glue the gaskets and motor to the back face, as shown in the figure. Finally, connect the double cam to the spacer with a 1⁄4-20 machine screw and a lock washer.
Making & installing the linkages
The two linkages are nothing more than three wooden discs joined together by a pair of aluminum rods, but as with the cams, precision is key.
Use my saw-and-sand technique to “turn” your discs to 1". Next, use the jigs shown below to complete the assembly. (Both jigs are included with the full-sized patterns.) Permanently affix the rods to the discs using epoxy or cyanoacrylate (CA) glue.
Final assembly & wiring
Attach the axle supports to the top of the base, top it off with paint, and you’re ready for final assembly. First, glue the lamp’s base to the top of the box and insert the PVC pipe. Press-fit the head and neck assemblies on their axles, and give the cam a few test turns. Once you are certain that the heads sway like they should, adjust the cam and glue the neck to the axle, as shown at right. Next, add the bodies, and then connect the motor and socket wires to a lamp cord, as shown below. Finally, screw the back in place.
Give ’em a lift. Set shims under the feet to minimize the gap where the body meets the neck before gluing it in place with a few drops of CA glue. The body is sized to provide a little wiggle room. If necessary, you can use 1⁄4" washers as spacers to shim the body out so that it’s flush with the neck.
Wiring it up. Join the motor and lamp socket wires to the lamp cord with wire nuts and electrical tape.
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