This Simple Bot was inspired by a work by artist James Rouvelle, called Colony, in which a bunch of odd-shaped ellipsoids self-propel around their environment. It is my understanding that his bots were made by placing a vibrating motor freely inside of a Styrofoam ball that was then coated to give it an irregular shape. This dynamic makes his orbs fluctuate between wobbling in place and jerkily moving around the room. While this is a cool interaction, I was more interested in making something that had a more regular motion and was able to roll steadily about. Towards this end, I have created Rolly Bot. To simply explain, Rolly is basically an over-sized tennis ball with an over-sized bristlebot placed inside. This allows Rolly to be rolled in whatever direction the bristlebot inside so chooses to drive.
Step 1: Go Get Stuff
You will need:
(x1) An over-sized tennis ball
(x1) AAA double battery holder
(x2) AAA batteries
(x1) Vibrating motor***
(x1) Small scrub brush
(x2) Zip ties
(x1) Cutting pliers
(x1) Razor blade
(x1) Coping saw or hacksaw (not pictured)
***My vibrating motor came from a back massager from Walgreens. You can learn to make your own here.
(Note that some of the links on this page are affiliate links. This does not change the price of any of the items for sale. However, I earn a small commission if you click on any of those links and buy anything. I reinvest this money into materials and tools for future projects. However, you are obviously free to source the items as you please.)
Step 2: Chop Off the Handle
Remove the handle from your scrub brush with a pair of cutting pliers.
The surface should now be made completely flat. Use your cutting pliers to trim off any remaining plastic. If that proves too difficult, you can cut off any plastic stubs with a coping saw (or hacksaw).
Step 3: Power Switch
Put the batteries into the battery holder.
Place a small piece of paper between one end of a battery and the battery holder. This piece of paper will prevent the motor from turning on right away when we make the electrical connection in Step 5.
Step 4: Zip Tie
Place the battery holder atop the scrub brush and the motor atop the battery holder. Zip tie them all together. This may take a little bit of patience, but should be fine once you get the first tie pulled taught.
Step 5: Wire It Up
Twist together the black wire from the battery terminal to the black wire from the motor.
Next twist together the red wire with whatever color wire is remaining. This is typically a red wire, but in my case, the wire coming from the motor was blue.
The colors are not so important as a DC motor should typically be able to spin regardless of the orientation in which the positive and negative terminals from the batteries are connected.
(If the motor has no wires coming off of it, solder the red and black wires to its power lugs.)
Step 6: Surgery
Using your razor blade, carefully cut open a slit in the tennis ball large enough to pass the bristlebot through.
Step 7: Insertion
Pass the bristlebot through the slit. Pull out the blue tab from between the battery and the holder as to turn on power to the motor.
Your bot should now be free to roll around as it chooses.