TL/DR: In this post, I talk through my process of designing the components for my marble machine components and give lots of design alternatives. If you want just a brief overview, here’s your one-page instruction manual. If you want all the details, read on. You can also skip to the bottom for videos of marble machines in action.

Goal

For a long time, I’ve thought about adding a peg board style “ball wall” to my classes, like this one from Exploratorium in San Francisco. They have peg boards on the wall, and a supply of pegs, ramps, and other components. (Here’s a Time lapse video of the machine in action.)

The general goal is to assemble a track where you start the ball at the top, and it tumbles its way down the ramps to the bottom without falling off the tracks.

This is a super simple idea that leads to a really rich and engaging learning experience! (Especially when it’s collaborative – two kids working together, or a parent and child working together.)

It’s a great “tinkering” exercise: You set up something that you think will work, then test it. If it doesn’t work at all, you try something new. If it almost works, or it works 3 tries out of 5, then you tweak it – make a minor adjustment, then test it again. Once you have one component working, you add another component and test again. Each step is quick and easy to build, and easy to test, so it’s easy to keep trying again. (Learn more about how this fits within a constructionist theory of learning in Exploratorium’s Activity Guide.)

If you have a child who tends to be perfectionist, and gets easily frustrated with “failures”, then it’s important to introduce this as a trying-things-out activity. The goal is not to build something specific, it’s to just keep playing at each component till it works. We laugh when it fails and the ball falls off the track, we cheer at each success.

In my classes, we already do lots of ramp play and have lots of marble runs, but it is time to give this one a try! I am confident this will work well in my lower elementary age class (5 to 8 year olds), and am curious to see how it goes with my preschool age kids (3 to 6 year olds.) I teach a co-op style class, so there are always plenty of adults to help.

Since we share our space with other classes, I need free-standing boards, not a permanent wall space, and I needed to find good options for all the other components. Here’s what I’m experimenting with now:

The Board / Wall

Exploratorium has great sets of instructions for how to build a freestanding board. (FInd them on Instructables or page 7 – 12 of this guide or they have a video of the process in the Coursera class materials.)

Although in theory, I know basic woodworking and this should be do-able, in reality, it’s been a long time since I really built things, so making the board became an intimidation barrier to me doing this activity.

Eventually I went looking for other options. On Amazon, I found lots of affordable metal display racks. And cost-wise, I could get a rack for about what it would cost me to buy the materials for building the Exploratorium style.

I chose a 2 foot by 5 foot metal pegboard on wheels (they have other sizes and options too). This is quite tall for preschoolers, so most of the time, I plan to split it into two boards, by adding these legs. I also got a pair of smaller 12″x16″ pegboards. (There are also many options for wall mounted pegboards.) Both have 1/4″ holes, spaced 1″ apart, so all the accessories will be compatible with either board option.

These pegboards are nice quality, with smooth edges, and seem durable. The tall display rack seems pretty sturdy – like it won’t tip over easily – but I won’t know till I’ve got it in the classroom with kids! (I do plan to lock the wheels, and put it nearish a wall to reduce tip potential.)

Since the boards are steel, that means you can use magnetic accessories on them, and I will also be able to use them with my Tumble Trax components, and the DIY marble run I made from PVC pipes.

Pegs / Hooks

The tall board came with ten 4″ white hooks. I ordered an accessory kit that included five 2″ hooks and five 4″ hooks. I prefer the 2″ hooks – there’s no need for the larger size. There is a little learning curve for kids figuring out how to insert these hooks in the board.

I also ordered some magnetic hooks. They are 2.5″ or 3″ with the base. I don’t love these – the hook screws into the base, and it comes unscrewed easily, and the base is small enough to be swallowed by a toddler. But there are lots of other magnet hooks available. If it turns out that the kids in my classes have a hard time inserting the hooks, I will look into different magnet hook options.

The magnets have a strong enough hold to use with a ping-pong ball, but the heavier shooter marble knocks them out of place. (See the video.)

Exploratorium uses 1/4″ wooden dowels – they trim them to 4″ lengths, and use a pencil sharpener to taper the ends to make them easier to insert. With these metal peg boards, those tapered ends just mean that the peg tips in the hole and falls out. I tried sanding them down – it’s a lot of work and has the same issue. I tried 3/16 and 5 mm dowels but they’re too small.) So, no luck with finding pegs kids can just push in.

Ramps / Tracks

I have two types of wood tracks: we already had Kodo ramps, and the 1′ ramps work well on the peg boards. (I love these ramps for ramp play in general – the basic set is $159 and well worth that.) I also like that these are wide.

But it’s cheaper to start with cove molding. I got the hemlock 9/16 x 1 9/16 from my local lumberyard, Dunn Lumber. (They have a 9/16 by 2 1/4 that you can order online.) It’s $2.88 for 8 feet, so you can get 16+ ramps for $6. They will cut it for you. I had them cut it into one foot lengths for the large peg board. You would want 6 – 9 inch legs for the smaller peg boards. You will definitely have to spend a little time sanding them, as the ends can be a little splintery, and I wanted the sides to feel smoother for my kiddos.

Here are alternatives I think could work, but I have not tested them! Home Depot has a 9/16 by 1.5 inch hemlock – online you have to order a 10 pack though, which is $200… but maybe you could find it smaller quantities in store? (Or maybe this design would work??) On Amazon, white 1/2 x 1 3/4 seems workable, poplar 3/4 x 2 5/8 – wider and more expensive, or these, which are much wider.

The Kodo ramps are 2″ wide by .75″ deep, versus the Dunn 1.56″ by .56″ of the cove molding, but they work fine.

You could choose to use pool noodles or foam pipe insulation cut in half lengthwise. (Someone made lovely ramps with PVC pipe cut lengthwise and 3D printed parts, but that’s way outside my skill set.) Or for a short term but free plan, you could cut paper towel tubes lengthwise.

What if ramps slip off hooks?

With the wood ramps on the smooth hooks, I found that if you had a slight angle (like the lower hook was one row (one inch) lower than the upper hook, the ramps would stay on the pegs easily. If set to a steeper angle, they would slip off. There are three fixes for that:

• You can wrap rubber bands around the hooks to make them grippier.
• I made a groove in the bottom of each ramp that you can rest over a hook and that helps it not slip. (I used a small round file and made the groove 1.5 inches from one end.) This works well for moderate inclines – like the angle made when one end is 2″ higher than the other end.
• For steep inclines, I cut boba straws into short lengths, and taped them to the bottom of one end of the ramp. You slide that over the top hook and it holds well.

Balls

This marble machine will work well with: pingpong balls, “super balls” – the bouncy balls like you get from a gumball machine, and 1″ shooter marbles. (I don’t like to use regular / non-shooter size marbles that are about 5/8″ because we share our classroom with toddler classes and I don’t want them to discover a stray marble we missed at clean-up time.)

You can use the Kodo wood balls with the tracks and Kodo tubes, but they won’t fit through TP or paper towel tubes or accordion tubes. You could try golf balls – I think they are so heavy they would knock ramps off hooks.

The choice of ball has a major impact: pingpong balls are really forgiving – they tend to stay on the track well. Bouncy balls can be a little wild and unpredictable, and work better in tubes they can’t escape from than on ramps. Shooter marbles are heavy, so they can knock the tracks out of place, and they also build up a lot of momentum so you’ll need strong bumpers! A magnet bumper is fine for ping-pong ball, but I usuallly use cardboard tubes for marbles. Over time, let your kids try all the options, because they’ll learn a lot from figuring out how to adapt to each type of ball.

Classroom management tips

Don’t put out too many balls at once!! If a kid has 20 balls, they take one and test – it falls off the track, and they let it roll across the room. They get a new ball, they test… pretty soon you have 20 balls rolling around the room.

If each kid only has one ball, then every time it falls off the track, they fetch it back and use it again and again.

In some non-carpeted rooms, the balls will keep on rolling all over. You can up some kind of barrier to contain them – even a thick rope or hose laid out in a circle around the marble machine can help contain them.

Tubes

It is also fun to have tubes, where the ball disappears in one end and re-appears out the other. There is less margin for error with them, as the ball has to be perfectly lined up to enter, so they are more challenging.

We happen to have Kodo tubes. I hang them on the pegboard with a pegboard paper towel holder. You can do a very slight angle with these – like a 1″ decline.

You can use toilet paper cores and paper towel tubes. You can also get accordion tubes. Note, the typical accordion sensory tubes are not big enough!! You need extra large 1.5″ diameter tubes for shooter marbles and bouncy balls. (The ping-pong balls won’t fit through them.)

The accordion tubes I fasten on with re-useable zip ties. (For the lower bends, you can often just prop them in place resting on a hook.) For the cardboard tubes, I use a holepunch to make holes, then fasten them on with: twist ties, pipe cleaners, paper fasteners or zip ties. Here’s what those look like on the back side of the board. (Note, I only had 2″ paper fasteners handy – smaller ones would work better.) I have not yet tested this in my classroom, so I don’t know which of these options will be easiest for kids to manage.

You can also tape tubes on.

The End Point

At the end of the ball run, instead of just having the ball roll across the floor, it’s more satisfying if it ends in a container. (And less chaotic with fewer balls rolling across the room.) Anything works for this! A cup or bowl, a basket, a small cardboard box. I used a slinky I had handy…

In my pegboard accessories kit, there was a cup in a cup holder and a basket and both these worked well as endpoints. (note: this particular kit has a fail – the brackets that are supposed to hold the basket don’t work. But, it’s easy to attach the basket with zip ties or pipe cleaners.)

Bumpers

Whenever you have a switchback (the ball was rolling to the left and now you want it to roll to the right), it is tricky to make that work. If you get the angles just right, and the ball drops into the right space at the right speed, it works.

However, it often doesn’t work. Often the ball jumps the track.

You can add bumpers so that anywhere the ball comes off track A, it will bounce off the bumper and land on track B. One of the easiest methods is to build bumpers with cardboard. (Exploratorium also uses craft foam and flexible plastic sheets, but why do that when cardboard is free and recyclable!)

I use TP tubes, whole or cut in half lengthwise. They can be tied on with zip ties, twist ties, pipe cleaners, paper fasteners… or just tape them on.

You could use a peg stuck in just the right place (I used a plastic straw – just squished the end a bit to fit in the hole.) You can make a foam block and stick a peg through it. Or, since the board is magnetic, try out your magnetic items and see what works! My magnet blocks and Magna-tiles did not work – they weren’t strong enough, so when the marble bumped them they slid away. My Magformers gears work, so do magnet wands. But my favorite is MAGMEN3. Magnets are excellent bumpers for pingpong balls and bouncy balls, but the heavier marbles plow right through them.

Slow or Re-Direct Force

There are also lots of ways to slow things down (helpful if your ball keeps flying off the track) or re-direct force (as bumpers do…) You can see videos of these in action at the bottom of the post.

You can hang a clothespin off a hook – when the ball brushes by it, the speed slows a little.

You can put a cork on the track – it slows the roll of the ball down as the ball pushes it away.

You can add friction to a ramp – put on sandpaper, bubble wrap or speed bumps.

You could use an angled pipe joint or elbow joint (copper or PVC). Or, I like the simple approach of cutting a hole in a cardboard tube – this kind of acts like a bumper and the next ramp in one piece. The ball rolls through the hole, hits the back of the tube, and rolls down.

You can also make a seesaw. Tape a piece of boba straw on the bottom of the ramp (near the center for a first class lever.) Then place it over a hook. It will immediately flip upside down. 🙂 You’ll need to block one of the ends so it can’t flip. Here’s an example. When the ball rolls down the ramp and lands on the end of the seesaw, the weight tips the lever and dumps the ball in the tube.

Other Ideas

Really, almost anything goes! For example, here I use items from the pegboard accessory set – the shelves become ramps, the paper towel holder holds an empty tube at an angle for the ball to roll through, in the cup holder I put a cup I had cut the bottom out of, another cup is turned sideways for the ball to roll in and roll out and the end point is the basket.

Funnels are great, but you need to get a funnel with a wide opening. These can be set in a cup holder ring on the pegboard. They can drop down into a big container easily. If they are dropping down to a ramp, I found it was hard to get them close enough to the board to land well, so I made little cardboard ramp to guide the ball or aligned it with a hole in a tube and taped it to keep them aligned.

You can try adding musical elements – bells on strings that ring when a ball passes by; elements that make “tink” sounds when the ball hits, and so on. Some people have added electric components so falling balls turn switches on and off.

I think there are also ways to incorporate fun stories into this to enhance the invitation to play. Like when you’re doing a farm theme, maybe putting a chicken at the top, a nest at the bottom and offering white pingpong ball “eggs” to slide down? Halloween themed bouncy balls?

Facilitating Play

The less time you spend talking and the more time they spend doing, the better.

So, just introduce the activity with just enough info that they know how to put one ramp on the board so the ball rolls into the end point, and the idea of putting another ramp on. Then step back and let them try! They will soon discover the need for bumpers and for ways to help the ramp not slip off the peg, so you can also quickly demonstrate those core skills, then step away again.

Encourage kids to work on one element at a time, not try to build a whole structure first and then test. Teach them to test early and often. Make sure one element works before adding the next.

It can work best to start at the bottom! Can they roll the ball down one track and into the end point container? Once that works, add an element just above that. Once that level works with getting the ball to the endpoint, move up another layer.

When they get frustrated, it’s tempting to jump in and solve the problem for them. Think of frustration as learning that’s about to happen. If you give them space, they may get there on their own, or you could ask them to describe the problem to you and they might solve it as they describe it, or you might say “I wonder what would happen if….” or “I notice that up here you solved a similar problem this way – what might you try here?” You might introduce a new material that might help solve their problem – “I wonder if a bumper would help?” “I notice this keeps sliding out of place – do we have some way to fasten something so it stays in the same place?” (Find more facilitation tips in Exploratorium’s guide.)

Ask them to present their successful designs to other people to show off their work. Ask what was the hardest thing for them to make work. (You’ll notice that’s where they have the most pride – succeeding at something that was hard.)

How far can they take it?

Video

Here is a video with sample set-ups, and machines in action. Pause it for closer looks.

Challenges

When kids have mastered the basics, here are some possible challenges you could issue to encourage them to take it to the next level (from Exploratorium):

• make the run from the top of the board to the bottom as slowly as possible
• make the marble travel uphill for a section
• make a loop-de-loop
• make an elevator to bring the marble back up to the top, or
• use multiple marbles for chain reactions.
• Can you split the pathways so some marbles go one way and some go the other way?
• Can you design something that wraps around from the front of the board to the back. (Video example.)
• Can you create a device where there is a cup mounted on a pivot – the ball drops in the cup, and it pivots around and drops the ball down. (See video in middle of this page.)

Learn More

This is only one approach to a pegboard style marble machine. Check my Pinterest board for lots of other examples.

Exploratorium also has an online class on Coursera titled Tinkering Fundamentals, which is excellent, and has a lot more information about the marble machine.

You may also be interested in my posts on “Lots of Ways to Learn to Build“, “Build a Wind Tube” and “Build a Scarf Cannon.“

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