This year I am featuring a cauldron creep and I am going to put a few shelves with ingredient bottles behind him. I wanted that display to be more dynamic than just old bottles with labels and I had a bunch of fishing lures so I figured a jar of squirming worms would be fun.
I went through several failed iterations to get this right from chain drives to micro magnetic FCG mechanisms. In the end, it was the simplest approach that actually worked. I haven’t stained the shelf yet and the motor mechanism will be hidden behind the wall.
Home Depot 5 sq feet ¼” plywood = $1.68
Electronics Goldmine 2 4.5” diameter plastic pulleys = $11.90
Electronics Goldmine 2 1.5” diameter plastic pulleys = $1.98
Magnet4less.com 4 1”x1/4” Neodymium cube magnets = $5.28
Magnet4less.com 6 1”x1/8” Neodymium cylinder magnets = $2.94
Magnet4less.com 6 ½”x1/8” Neodymium cylinder magnets = $1.20
Office Max 2 7” rubber band = $0.80
Office Max 1 2” rubber band = $0.01
Home Depot ½ oz plastic wood = $0.23
Home Depot 1.5” 0.5” PVC pipe = $0.02
Home Depot 1 2” x ¼” hex bolt = $0.18
Home Depot 2 2” brackets = $2.34
Home Depot 10 1 5/8” wood screws = $0.86
Home Depot 4 1” wood screws = $0.26
Home Depot 2 ¼” washers = $0.16
Home Depot 3 ¼” hex nuts = $0.18
Home Depot ¼ oz Gorilla Glue = $0.02
Radio Shack 6 4/40 machine screws = $0.29
Radio Shack 6 4/40 hex nuts = $0.40
Home Depot 3.5 feet 1.5 x ¾” pine board = $0.87
Home Depot 0.5 sq feet ½” pine board = $0.79
Home Depot 1.5 feet ¼” molding = $0.58
Academy 12 fishing lures = $2.55
All Electronics 1 45rpm gearmotor with pulley = ($9.75)
TOTAL = $35.51
I found a source of cheap magnets online. Now, a word of caution. If you go to this web page, you will be tempted to buy some very powerful magnets. I don’t recommend buying anything stronger than what I have listed here. Shortly after I ordered these, I was disappointed that I didn’t spring for the 2” x 2” x ½" cube, but I did get four 1” x 1” x ½" magnets. After playing with those for a while, I am afraid to have them in the house. They have the potential of some serious crushing injuries! The 1” x 1” x ¼” cube magnets have already bloodied me twice by jumping large distances at each other and pinching my finger (hard enough to draw blood). Thank god I didn’t go for the 2”.
Back to the prop.
I used my circle-cutter attachment for my Dremel and a beveled cutter to cut 6 beveled circles out of some ¼” plywood. I sanded the edges smooth and glued two each to my large pulleys. I did this to help keep the rubber bands from jumping off the track. I also cut two 1” squares in the top disk to hold the magnets. I glued one magnet in North up and the other one South up for both pulleys.
I cut one more smaller circle (not beveled) and glued the last two beveled disks to it. I now had a wooden pulley that I attached to the top of the motor pulley. Now, I could spin both pulleys with one motor. I used short pieces of ½” PVC pipe filled with Plastic Wood to hold the pulleys in place.
I made a frame around the edges of the shelf with the 1.5 x ¾” pine board. I put another piece of plywood over the top of the frame to finish up the shelf.
All I had to do now was to insert the smaller magnets into the heads of the fishing lures. I put one magnet in each by carefully making a hole lengthwise through the worm’s “mouth” with a straight piece of coat hanger and inserting the magnet through the hole. You do have to get the magnet pretty deep into the lure or it will eventually push itself back out. That’s it. You are good to go.
Again, this shelf will be beside the cauldron creep you see in the background and the motor will be hidden.
Seriously, be careful with those magnets!