3. CUT BELT GROOVES INTO THE SKATE WHEELS
3a. Gently clamp or strap your drill to a workbench as pictured.
Assemble a mandrel from a 7" bolt and some large (fender)
washers, to grip the skate wheel. When assembled, the entire
wheel must spin, not just the bearings.
3b. Chuck the assembly into the drill. The wheel should turn toward
you and the speed should be fairly fast. With a crosscut bastard file,
make a ¼"-wide flat on the wheel. Then switch to a rat-tail file to
cut the groove. Apply light and even pressure to the file.
4. ATTACH THE SKATE WHEELS TO THE DISKS
4a. Use a step drill bit to widen the hole in the acrylic disk to 7".
Be gentle, and go slowly, because acrylic is easily cracked.
4b. Remove the washers from the wheel and use the 7" bolt to
center the wheel against the disk. Drill four 1" holes through the
disk but not into the wheel. Then switch to a r" bit and drill partway into the wheel in 4 places. Finish the holes with a countersink.
4c. Remove the 7" bolt and drill the center hole out to ½" or 3"
using a step bit. You want the edges of the hole completely clear
of the rotating parts of the wheel bearing. Install 4 small countersunk screws. Tighten these so they just touch the disk. The disk
must remain as flat as possible.
5. CUT THE SECTORS
Decide how many sectors you’re willing to cut. I’m rather lazy and opted for fewer, 16 per disk. If you make
24 or 32, you’ll have to make them smaller but you’ll be rewarded with longer sparks.
Following the diagram at makezine.com/17/wimshurst, make
a template from a plastic milk jug, then trace each sector onto
aluminum tape. It’s a good idea to make some extra sectors to
practice with. Cut them individually; don’t be tempted to stack
multiple layers or your cuts will end up ragged and bleed charge
away into the air.
TIP: I found it easiest to use an X-Acto knife and straightedge to cut
the long sides, and then switch to scissors for the curved ends.