Day 64 — Rube Goldberg Machine

Today I completed my Rube Goldberg machine. In this blog post I am going to explain how I went about designing it, how I built it, and show a video of it in action.

Initially I was unsure where to begin and how to go about this assignment. I decided to break it down into 6 components/ideas that I wanted to use and then go from there.

1. Firstly, I wanted to incorporate the robot, Elegoo, into my Rube Goldberg Machine.
2. Some sort of domino effect is always nice in a Rube Goldberg machine, so I wanted to include that.
3. Having already built a ping pong ball launcher, I thought that using that would be cool.
4. A “slide” to direct a ball along a certain pathway.
5. The principle of conservation of momentum; a nice way to increase the intricacy of the system and a demonstration of a crucial law in physics.
6. Finally, some sort of ball in the hole/cup finish to add a little pizazz.

I opted to add Elegoo in at the start as the initiator of the Rube Goldberg machine. By simply coding him to move forward briefly and then stop, I was able to achieve this. Below is the code I used, which I added into the void loop of the Tumbller and uploaded to the Arduino board of the robot. The millisecond timer tells it to move forward for 2.5 seconds and then stop.

Next, I used books as a substitute for dominos. By setting them up in order of smallest to largest and spacing them accordingly, it didn’t take long for me to create a nice domino effect.

Subsequent to that, I altered my ping pong launcher to remove the stock, trigger and part of the barrel. Using gorilla glue tape and a block of wood used to house knifes, I had my launching platform. I then taped a peg to the ground and used this to hold the rubber band and contain the potential energy of the elastic. The peg is placed so that once the final book falls, it will hit the peg and force it to open, releasing the potential energy and allowing the ping pong ball to be launched.

Following that, I built the “slide” for the golf ball. I removed the bottom parts off an old set of crutches and taped them together. Using books, I propped one end up to add potential energy to the golf ball. I placed a playing card in front of the golf ball, secured very loosely in place with tape, which is stuck to the underside of the “slide”. So loose, in fact, that a mere ping pong ball could hit it and displace it, allowing the golf ball to convert potential energy to kinetic energy and roll. This involved a lot of trial and error, to ensure the launcher would hit the card accurately each time, as I had no way of accurately measuring the forces contained in the rubber band.

Once the golf ball was released and could roll, the idea was that it would hit another golf ball and the principle of conservation of momentum would be observed, sending the second golf ball into a cup. A little bit of maths was involved here. Follow my calculations below, which I used Latex to produce.

From these calculations and trial and error (imperfect environment led to some discrepancies), I found that 15° was the minimum incline I could use for the “slide” which would give the second golf ball enough momentum to carry it over the lip of the cup for the grand finale.

Without further ado, here is the complete Rube Goldberg machine in action! It’s quite humbling that all of my time and effort only equated to 14 seconds, but overall I am pretty satisfied with how it turned out.

Thanks for reading and watching. This was my last assignment for my 3MEMS3 Design module so this is me signing off for a while. Fingers crossed I get a decent grade now!