I wanted to build some marble run building blocks for a 3-year old nephew as a Christmas present. I have always been into marble tracks and marble machines so maybe I got a little carried away. But I think adults will enjoy these blocks at least as much as the toddler.
I wanted the track segments to somehow interlock to form larger tracks. But I didn't want to add protrusions to the track segments or to the pieces that they rest on. So I drilled a hole in the ramps and supports to the diameter and half the depth of a marble. That way, a marble can be inserted between the ramps and supports to keep them from slipping around. I originally came up with this idea when I built my mobile tool stand.
Having the marble interlock to keep the segments from sliding around is important when the track goes around a corner. Without the interlock each marble would knock the piece on the left a little further from the incoming ramp.
I also had a problem that marbles didn't always make it around the corner. Sometimes they'd come too fast and would just overshoot the groove. I squared out the track at the top (you can just see it in the photo), which helps a bit.
The idea was to string together segments of tracks much like is shown in this photo.
I was still running into problems of marbles overshooting sometimes though. The little mini-bowl at left for example would often be overshot. Adding a right angle exit to some of the track segments really slows down the marbles and prevents overshoot. To make the right angle I just drilled a hole in from the side and glued a piece of dowel into the track to keep the marble from going straight.
Another way to slow down the marbles is to make a zigzag track. The marble takes a while to traverse down this one, plus it makes a neat noise as it bumps into all the obstructions.
A circular bowl is also good for slowing down the marble. This bowl works best if marbles are injected tangentially from the edge . The marble keeps going round and round until it loses its energy, and then exits through the hole in the middle. I came up with the bowl idea when I built my marble machine two
I had the idea of producing something similar to the bowl but in just one dimension. The marble enters on the left or right and rolls back and forth in the arched track until it loses its energy and settles at the bottom. A slight slope then leads the marble out the hole on the side.
Just for kicks, I made a curvy piece of track as well. It doesn't slow down the marble that much, but it sure looks cool. See my article about building these blocks to see how I made that one.
Every time a segment is added to the top, it needs to be higher up than the previous segment, so one is always building up. Sometimes it's desirable to build above existing tracks. I made these little bridge blocks to put on top of existing track segments. The marble can roll through the holes so the tracks below are not obstructed.
While testing the blocks, I realized that the set needed a whole lot of non-track blocks just to build up the supporting structure. I made a big batch of plain rectangular building blocks to help build up the structure. The big square blocks in the background are meant to be put vertically to gain height quickly. The longer flat pieces are useful to build up smaller height and to tie columns of the structure together.
Finally, made a lot of little "shim" blocks, which are useful to get things to line up properly. I didn't strictly follow a system of integer unit sizes like Lego does, so often there's odd height differences where shims come in handy.
As a box for the whole thing, I used one of my milk-crate inspired wooden boxes. If all the rectangular building blocks are stacked carefully in the bottom then it all fits even with the ramps dumped in loosely. But if I just dump the blocks in loosely, they won't fit. The box and blocks together ended up weighing about 15 kilograms.
The set is probably a little advanced for my three year old nephew,
but his parents are having a blast playing with the blocks. So
far, my newhew is mostly adept at knocking them down, although the track below
lasted surprisingly long before it was destroyed.
I made a YouTube video of the marble run in the first photo of this article.
Here is my nephew Sebbie playing with the tracks at christmas. He was three years old at the time.
I should add that he didn't build that track, though he was quite adept at knocking tracks down.
And another video explaining how the various marble run elements work.