Rube Goldberg Machine Development

Hugo Zieg
4 min readApr 27, 2021


The first and arguably most difficult part of the Rube Goldberg machine is to decide the final task that it should complete. After many nights of long hard thought I decided that the mundane task of mixing coffee powder and milk before adding the water was just too much to be troubling myself with every time I made coffee. Now the task was to create an overly complex and impractical machine that would revolutionise the way the world make coffee forever more. Done away with are the Nesspresso machines of old replaced by a machine controlled by the mighty robot Steven

Steven on his way to change the coffee game

I decided I wanted to mix the milk and coffee in two separate chain reactions triggered by the same initial caused by Steven’s response to the command to make the coffee.

Now since I have decided the start and the finish points of the reaction it was time to create the main entertainment value of the machine….. the middle reactions. Since I wanted Steven to start both reactions simultaneously I needed to keep in mind that the first reaction of each individual chain would have to be triggered by a single stimulus that was caused by Steven.

I chose to create the machine out of materials that I could find in the workshop and around the house and repurpose to suit the tasks that I needed to perform within my machine. On top of this I wanted to use a simplified version of my launcher in this machine.

Here is a schematic of the coffee powder side

I decided that the first reaction of the coffee powder side would be a marble run as this would be easy to trigger by a pin being pulled due to a previous reaction caused by Steven. The marble would then run down a series of tubes before triggering a domino run which would then use a lever arm reaction to trigger the coffee powder launcher. In order to make the coffee powder launch into the cup reliably I filled tea bags with non dissolvable coffee powder so the weight of coffee powder was always the same.

I decided to build the two reactions on the one piece of plywood board
Marble race made out of a combination of wood and PVC pipe
First draft of the powder side complete

Using a digital suitcase weigh-scale I found that the weight required to pull the launcher trigger was 1.2 kg to reduce the mass needed I extended the handle from 0.15m to 1m this reduced the weight needed to 0.18kg however after more testing it was found the weight required to fall into the cup is 250g minimum this is due to the friction where the string runs over the screws.

Next I decided to build the milk side before fine tuning the entire machine to function as one unit.

Schematic of the milk side of the machine

In this machine the milk will be tipped into the cup by using a water bottle to tip the platform the platform required a weight of 1.2 kg to tip when the friction from the string is taken into consideration this equates to 1200ml of water to be in the bottle to cause the reaction therefor i will use a 1.75l bottle and will fill it to the brim as this will give more than enough force to tip the milk. Next thing to worry about is tripping the stop valve this takes a weight of 3kg to make the valve completely open to allow maximum water flow. I therefore used an old 5kg rectangular battery from an auxiliary power supply device. This will make the valve open quickly after the retaining string is cut. The scissors required about 1.5 kg of force to cut the retaining string this is too much to be caused directly by Steven’s electrical motors. Now the real problem solving must be done.

Schematic of the initial reaction that will trigger the start of both machines
First iteration of the combined machines
Initial mounting position of Steven
New position of Steven with weight trigger device and the domino element replaced by a marble run

In the final design the domino element was replaced with a marble run as the dominos were prone to falling at inopportune times is the board shook. Also i decided to use three marbles 2 small and one big. The two small were released first and should be enough to trigger the weight falling into the cup however the third large marble was used as a safety net to guarantee the weight falling. I also added a spout to the launcher that would direct the powder into the cup.

For the purpose of the video I used water instead of milk as I thought the use in the building of the machine would be quite wasteful!!