The Rocking Dish

Feeling unbalanced? Then this will fit right in!

The rocking dish is a wobbler, a plate where you can try to balance mugs with washers with toys with styrofoam heads. There's room for everything at the table, but it just has to be situated the right way.

I loved making this for my class because it allows students to play with balance and motion in a freeform way. There are adjustable levers, fulcrums, and the ever-tilting game of balance and distance. It is based on an a wonderful exhibit at the Exploratorium called "The Unstable Table" which I wanted to make for under $10.

Let's get wobbly.

• What: The Rocking Dish
• Where: Here, now over there! OH NO!
• Time: ~ 45 minutes to make
• Concepts: balance, center of gravity, motion, levers, fulcrums
• Cost: $9
• Materials:
  • Wood Balls x 3 (two of them are optional, I bought 1 1/4" ones)
  • Dowel (any one that can support a bit of weight)
  • Wide Washer (wide enough to allow range of motion for ball)
  • Washer weights (for balance on dowel)
  • Wood for table
  • Dish (any circle of plastic or wood will do)
  • Screws
• Tools:
  • Wood Saw
  • Drill
  • Sander (optional)
  • Hot glue gun / hot glue

Here we G-G-G-G-O!!!!!

Start by cutting a piece of dowel that will be the main lever of your unbalanced dish. I made mine about 24" long, which worked great. Next up, drill a hole in a wood ball that matches your dowel diameter. Go about halfway through.

Next, mount it on the dowel and either sand or cut it so the top is flat. Make sure to be careful to line it up with the whole on bottom!

It's going to wobble, but it still needs a center.

Drill another wood ball all the way through making sure to go right through the middle. When mounting it on the dowel, you can decide what position you want. Closer to the top could mean more balance, but less range of motion. I slid my fulcrum 3/4 to the top of the dowel, and hot glued it there.

Test it out with how it rolls around on the wide washer. You want it to have a good freedom of motion.

For the balancing act, our lever is going to need some weight.

Use heavy washers on the lower end of the dowel to keep the unbalanced dish a little bit balanced. After putting on some washers, drill another wood ball halfway through and slide it on bottom as a stopper. You can always take it off later to add, subtract, or move weight around.

Now we have a pretty nifty lever!

Circles are great, and any will do. Have a plastic plate? A wooden disc? An old frisbee? It all works!

Find the center of the circle using this great method, and then drill through. Take your wood ball with the plate side, and pre-drill a tiny bit so you can screw on the plate. Add a washer to keep everything steady.

You can make any style supporting table you like!

I made mine simply, and here's how. Measure the distance from the central fulcrum to the bottom of the lower ball. We'll want the legs to be at least that long. Add a couple inches, and cut four 2x4 pieces to make legs. Mine were about 18" long.

Cut a thinner piece of wood into a rectangle or square that's wide enough to not be hit by the lower part of the lever as it tips here and there. Mine was approximately 12"x24".

Find a spade bit that's just smaller than the wide washer used for the fulcrum and drill a hole through in the middle. Perfect!

Drill and screw to attach the legs to your table top, and then use some hot glue to attach the washer at the fulcrum. You, good person, have an unstable dish!

Now you can do anything. It's like a balancing seesaw in two dimensions.

Here are some things that I like trying:

• How many objects can you fit on?
• Can you balance a heavy one with several light ones?
• Can you balance three objects placed in a triangle?
• Try adding or subtracting washers from the bottom of the lever. What happens?
• Try ungluing the central fulcrum and re-gluing it somewhere else on the dowel. What happens?

Unbalanced isn't bad. It's just always moving. Have fun, get wobbly, and keep exploring.