Introduction: Bar of Soap Rube Goldberg Machine

This Rube Goldberg machine is meant to drop a bar of soap with at least ten steps. The one made here is using preexisting shelves, however, a pegboard or cardboard taped to the wall may work too.


-Paper towel/toilet paper tubes - amount varies on space

-2 golf balls

-pencils (or a similar object)


-tall and light object (ex: deodorant)


-6 domino-like things (ex: eyeshadows) - amount varies on space

-painter's tape

-string or ribbon

-small cups


-ping pong ball

-two lipsticks

-tape roll

Step 1: Step 1: Toilet Paper Roll Starting Point

First tape a paper towel roll to the wall at a slant. This is so the object you use (a chapstick used in the video) can gain momentum when sliding down.

Step 2: Step 2: Domino Effect

Next, place two domino-like objects (eyeshadows shown here) parallel to each other with one of them facing the opening of the toilet paper tube from the first step. About two inches are in between, but that depends on the height of the objects used. You should test the distance needed in between each object by knocking them down prior to the final testing of the whole machine to save time, mark the spots that work with a pencil.

Step 3: Step 3: Seesaw

To make this seesaw, take a ruler and tape a lipstick or similarly shaped object in the middle so it can rock back and forth like a real seesaw. Place this so that the end sticking up is right next to the second eyeshadow from the previous step. The other end should be near the ledge of the shelf and tilted down. Again, test this step to make sure it is in the right position and mark with a pencil.

Step 4: Step 4: Launch the Ping Pong Ball

Just above the lowered end of the seesaw, tape a sideways cup to the ledge of the shelf as seen in the picture. Only tape the lip of the cup so it can be tilted up by the seesaw. Once in place, add a ping pong ball.

Step 5: Step 5: Ping Pong Ball Goes Down the Tube

Next, tape a paper towel tube from one shelf to the next. Make sure the top end is lined up with the cup from the previous step so the ping pong ball can smoothly transfer into the tube (this may take some fiddling). Prop up the lower end if needed (depending on speed and angle of ping pong ball) with an object underneath.

Step 6: Step 6: Guide

If your ping pong ball does not exit the tube in a straight line, add a guide by taping a pencil or similarly shaped object to the shelf to make it go in the right direction.

Step 7: Step 7: More Dominos

Similarly to the second step, take more domino-like objects (eyeshadows again) and place them as far apart as needed (depending on height). I am only saying domino-like objects instead of actual dominos because the steps require a good amount of force. Large dominos may work too.

Step 8: Step 8: Hit Marble

At the end of the chain of eyeshadows, place a tall object (lipgloss used here) to tap marble off the ledge. If the lipgloss doesn't touch the marble, add a bumper to extend the reach.

Step 9: Step 9: Catch Marble

Cut a paper towel tube in half and tape inside up to the wall. This is so the marble can be caught when dropped off the ledge.

Step 10: Step 10: Tube Tunnel

Connecting to the end of the trap in the previous step, create a downward-sloped tube tunnel using paper towel tubes and toilet paper tubes (depending on the length of the wall). This step requires the most fiddling to get right, so make sure to test properly before the final run.

Step 11: Step 11: Pulley

Using the shelf above, tape a tape spool to the underside to create a place to hang the string of the pulley. On one end, connect a basket using a small cup and another piece of string as shown in the picture. The other end should connect to the underside of another small cup connected to the last shelf. Similarly to the cup used with the ping pong ball, only tape the lip of the cup to the shelf, so the cup can be tilted. Then place a golf ball into the sideways cup. If the marble is not heavy enough to lift the second cup, add weight to the first cup until the tipping point is almost met (meaning the marble will be enough to cause the golfball to fall).

Step 12: Step 12: Golfball to Golfball

Directly underneath the lip of the cup on the shelf, create a ramp using a ruler propped up with a lipstick or similarly shaped object. As done before, make a guide using pencils, tape, and tubes. At the end of the ramp, place another golf ball to be hit by the first golf ball.

Step 13: Step 13: Drop the Soap

At the other end of the shelf in direct line with the golfball, place a small, round object (ex: yoyo) and a tall, light object (ex: deodorant). Again, continue your guides so the golf ball doesn't fall out of line. The force of the golfball should bump the yoyo into the deodorant, finally hitting the carefully balanced bar of soap on the edge of the shelf, dropping the bar of soap.