Rube Goldberg: How-to Build a Multi-Track Ball Feeder

A step by step STEAM tutorial on how to build a Rube Goldberg Track Feeder from your own toys or household materials.

This is an easy technique for your next Rube Goldberg Machine. You can make it from your own stuff. A track feeder can change the direction and position of a rolling ball. Each track “feeds” the ball onto the next one. In the example above, I’m using Hot Wheels tracks, but I’ll also show you how I make tracks from cardboard, rubber bands, or even the tops of books. You can use anything that a ball will roll on. For our purposes, think of a track as a tilt-able flat surface with walls on the sides to keep the ball from rolling off.

This post is intended to teach one specific Rube Goldberg technique, and also to illustrate the idea that every complicated machine is made from simpler parts. Simple parts can be mixed and matched, through many different materials and uses. Consequently, the more we build skills and understanding about these simple parts, the more reliable our more complex machines can ultimately become.

Materials

Find, or make your own materials for building this project. Here are some suggestions:

  • Hot Wheels or other type of car tracks if you have them
  • Cardboard, plus scissors or craft knife, and ruler, if you want to make your own tracks
  • Blocks, or other objects to support tracks, and for blockers to deflect the ball.
  • Rubber bands
  • Ping pong ball, marble, or other small ball.
  • Popsicle sticks, dominoes, pencils, – or any objects to act as blockers
  • Assorted other things you think of or find to use!
image: Rube Goldberg Track Feeder Technique Materials
The basic materials

Gather Materials and Choose a Space to Work.

A floor or a table work well. You may not have all the same materials, so use what you do have – in other words, be creative, and make this project your own way. How it works is not dependent on specific materials, but on understanding the basic ideas behind it.

Rube Goldberg Machines begin with the end in mind.

Whether I’m building a big chain reaction from lots of different parts, or just one simple part, I almost always start at the end, working my way backwards. This method is so valuable that I tend to use it for each individual part. So with a track feeder, I prefer to start building from the bottom; that’s where the ball ends up – the “output”.

So the first track I build will be the last track the ball rolls down; let’s call it track Z. This ramp will be the output of your machine – the place where the ball ends up. If making a ramp seems simple, it really is, and it is the basis for the whole project! A ramp, or an inclined plane, is a tilted flat surface (and the most basic type of Simple Machine.)

image: Rube Goldberg Track Feeder Plan

I incline track Z by placing a domino, block, or other object underneath one end of it, then I begin building the next part. I use bigger blocks, dominoes, other household objects, and different kinds of building toys to make platforms for my tracks.

Make the First Ramp – Track Z.

image: Rube Goldberg Track Feeder Single Track
One Track Feeder – boring!

Add More Tracks, Platforms, and Blockers.

Let’s build another one. This is track Y, which will feed the ball onto the higher end of track Z. As a ball rolls down track Y, and falls onto track Z, it hits a blocker. The “blocker” absorbs some of the force, allowing the ball to change direction and continue on down the next track. If the blockers are small, they may get knocked over as the ball hits them – this effect makes things more interesting, at least to me.

image: Rube Goldberg Track Feeder Double Track
Two Track Feeder

Now add track track X, track V, etc…Each additional track is just another inclined plane, resting upon one or more supporting platforms – in the pictures above, my platforms are made from wooden blocks, but you can use any stable object you happen to have.

image: Rube Goldberg Track Feeder Triple Track
Three Track Feeder
image: Rube Goldberg Track Feeder Quadruple Track
Four Track Feeder

Tips & Tricks for your Rube Goldberg Track Feeder

Rubber Bands Add Friction!

More about rubber bands: I often wrap rubber bands around the blocks that I rest the tracks upon, in order to add friction which keeps the track from slipping. The more gently your ramps are sloped, the less of a problem you’ll have with slippage, but even so, the rolling of the ball might knock some tracks out of alignment with each test of your machine. Rubber band friction can really help keep things in place, which will make your machine more reliable. Some people like to use tape, but I prefer rubber bands because I can use them over and over again.

image: Rube Goldberg Track Feeder Rubber Bands for Friction
Rubber bands add friction and resist unwanted motion!

Keep Tracks Separate

Notice that I keep some distance between tracks, so they don’t touch each other. Each time you test or run your machine, your tracks may move slightly, slipping out of position. You are already minimizing this factor by using rubber bands for friction, and using simple, sturdy platforms, but keeping some distance between your tracks will make it even less likely that they will overlap each other. Otherwise, overlapping will likely cause the ball to get stuck in place.

image: Rube Goldberg Track Feeder Leave gaps between tracks

Simplify, Simplify!

A complex machine is made from simple parts. If the part is doing something more than, or different from what I want it to do, then I need to simplify it. I’ve included two examples to show you what I mean.

image: Rube Goldberg Track Feeder 
A track supported by an unsteady tower of dominoes
An unsteady platform

1) This tower of dominoes is not a simple platform. Rather than provide a solid, stable support, the dominoes may slip, slide, rock back and forth, and ultimately fall apart. In other words, the platform will be in motion, which is not what I want! To fix this, I made the part simpler by replacing the dominoes with a single block.

image: Rube Goldberg Track Feeder 
A track supported by a steady block with rubber bands for friction
A steady platform
image: Rube Goldberg Track Feeder 
A track that is too steep may slide off it's support
Too steep!

2) This steep ramp is not a simple part. The track will slide off because there is not enough friction. to fix this, I made the part simpler by adding another block to make the ramp less steep, and also by adding rubber bands for friction. Now when a ball rolls on the ramp, the ramp itself is less likely to be in motion.

image: Rube Goldberg Track Feeder 
A track supported by two steady blocks with rubber bands, and with a gentle slope, won't slip.
Gentle Slope

In Rube Goldberg, and in Life: Plan, Build, Test, and Improve; Learn From Your Failure Points, & Try It Again!

As you build, test, and test again. It may work this time, but not the next. Analyze the differences. Of course each failure is an opportunity to learn, and the more failures you can learn from now, the more success you’ll have later on, because you’ll have developed more understanding and better skills. So don’t despair! Feel your feelings, and then get up and try again… Growth mindset means we can acknowledge our failures, while allowing for future learning, growth, and success. Say, “It doesn’t work…YET! I can’t do it…YET!

The Terrible Failure!

Alternate Builds: Make Your Own Tracks From Cardboard

If you don’t have plastic car tracks, or if you just enjoy making things from scratch, try making cardboard tracks for this project. I prefer cereal box, or cracker box cardboard – lightweight, but plenty sturdy for this purpose. I cut the boxes into strips, fold up the sides using a ruler or other straight edge, and I’ve got a new supply of tracks!

Image: Cutting cardboard into strips to make tracks for Rube Goldberg Machines
Cereal or cracker box cardboard is lightweight and easy to cut and fold
Image: folding cardboard strips on a ruler to make tracks for Rube Goldberg Machines
Precise measurements are not always necessary, but I like a straight edge to fold along!
Image: after we've folded cardboard strips on a ruler to make tracks for Rube Goldberg Machines
Fold up the sides
A cardboard track for Rube Goldberg Machines
Voila! A cardboard track!

In the next video, see how I’ve used cardboard tracks and other household objects to make different kinds of track feeders.

Alternate Builds: Include Household Objects in Your Track Feeder

Notice some different properties for each type of object. In the first video of this section, the cardboard tracks fit right in with the home-made feel of this build. In the second video, see how rubber bands can be stretched around lids and books to make great tracks, too.

Alternate Builds: Booktop Track Feeder

In the final video, see how the tops of hard cover books make their own track feeder. The tallest book feeds the next tallest, on and on, all the way down to the shortest book. Each book is inclined gently with a domino, pencil, small plank, or other object. Use dominoes for blockers, or anything else you can find.

What Have You Discovered?

An engineer is someone who learns the best available science, and puts it to work. And the more you put it to work, the more science becomes available for you to learn. You’re learning by doing – that’s hands-on learning!

I hope you enjoy building a Multi-Track Ping-Pong Ball Feeder as part of your next Rube Goldberg Machine I’d love to see what you come up with – stay in touch!

Jay Mankita, PlayfulEngineers.com

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