Grimm's Marble Runs 101

November 16, 2020

Guest post by BuildingWithRainbows

I don’t always have the emotional energy left at the end of the day for small world play, but building a marble run is always relaxing for me (and the kids (ages 4/7) normally want to take over before I get very far).  I’ll usually stick around as the support crew, keeping things lined up and stably stacked, but for the most part, once the first few ramps are in place, they’re off and running with it.  I started this one simply enough…and was very heavily embellished by the time the kids were done—but it still worked!  (Even if you couldn’t see the marble for the decorations).


As you start to assemble your marble run kit, there are lots of great sets you can work with.  To get you started I’ve tried to outline a few that would be a really good starting point and a give lot of flexibility.    There are lots of other sets that are also fantastic, but as you’re shopping and planning, consider these four main components: 

  • LIFT to get the start of the track up high (the marble needs some place to go)
  • BROAD SURFACES for the marbles to run on
  • SLOPES to get the marbles running and keep them going, and 
  • RAILS for the marbles to bump against

Many pieces can double up as more than one of these elements, but most runs need all four components. 

I think of these as great starter sets, but you don’t need all of them to build great runs, and you certainly can swap out for other sets to get a great effect.




The Grimm's Basic building set (4cm scale) is one of the most useful and flexible sets out there—the big pieces that have more than a single 4x4cm contact point with the ground make a great foundation when you’re building tall, and the arches are beyond cool when you can route the run both over the top and under the tunnel.  The 4x4 (large) Stepped Pyramid seems to find a way to make itself useful in almost everything, but having a variety of sizes is helpful to slot things in when you’re close, but not quite at the right height (the stepped counting blocks give you even more precision, but we really appreciate having those biggest pieces that are only in the stepped pyramid). 

Grimm's Basic Building Set

Grimm's Basic Building Set Grimm's large stepped pyramidLarge Stepped Pyramid




Because these marble runs often don’t have an indentation for the marble to follow down the length of the track, it's important to have a broad surface for the marble to roll on to allow for a little imprecision.  The Grimm's Building Boards are a nearly-essential component to marble runs.  If you have a large rainbow, you’ll want to have the Grimm's Natural Semi-Circles as well for a most satisfying corner rounding experience.  The Grimm's Natural Stacking Bridges are really fun for swoops and arches, but are a little harder to balance and integrate.

Grimm's Natural Building Boards Grimm's natural semi-circles Grimm's natural stacking bridge

For all three of these, while the rainbow colours are tempting on the shelf, I’d highly recommend the natural wood pieces to make it easier to find and track the marble as it moves down the course.  There is already SO MUCH colour coming in with the blocks, I really appreciate the natural pieces in marble runs (and have always been happy with them in other construction).

Grimm's Marble Runs, with natural elements



Every marble run needs something to get the ball rolling, and while you can do this by raising one end of a building board, it’s really helpful to have some sloping pieces to build and keep the momentum between components on a run.  We started out with the slopes set, and it has a lot of really good pieces, but it takes a bit of finesse to find the right angle for each situation.  Additionally, as many of them have “drop offs” at the bottom of the slope, you need to work a little harder to fit them in place smoothly.  More recently we added the stepped roofs, and in addition to making a marvelous sound, the consistent slope that always ends at “ground” level has been much easier to work with.


Grimm's rainbow stepped roofs    Grimm's Sloping Blocks

            Grimm's rainbow stepped roofs                                                 Grimm's Sloping Blocks                                



I love the simplicity of a run that doesn’t require any edges to keep the ball on track, but most builds need something to do the job.   To turn a full 180°, a Large Rainbow arch resting on a Semi-Circle is perfect.   On a long straight-away or in tight spots, the Colour Charts Rally pieces are narrow enough to give guidance and because the edges are flat, they stand pretty easily. When the ball is coming in with a lot of momentum, the rails do sometimes need to be weighted or backed up by heavier pieces to keep them in place.



Grimm's Large Rainbow  



   Grimm's Colour Charts Ralley


Grimm's Large Rainbow                                                                Grimm's Colour Charts Rally


This is one my 7yo built—you can see the narrow guides on the side and supported, heavier rail pieces where it turns corners.




We do most of our runs with the Grimm's “small balls” (12 in a set) as they have a good mix of weight for momentum, but not so much weight that they frequently knock the track out of place.  As the runs get bigger, they often get more fragile and then we use the smaller Grimm's marbles.  The set of larger 6 Grimm's balls (the ones that come in the egg carton) can be used in a few cases, but most of the time we find they have too much oomph and knock over the structure.

Grimm's Small Rainbow Balls                                                          Grimm's Wooden Marbles




This first run is a great one for getting the hang of how the balls move down the track, how they affect the track, and how you might need to tweak and adjust the track to keep the ball moving all the way to the end.  It uses just three sets- Classic Rainbow, the Semi-Circles and the Building Boards.


The arches of the Large Rainbow are first used to elevate the track, then again as rails and then finally to support the semi-circle rail.


The Building Boards are the main track in this one, and the Semi-Circles function both as tracks and as a rail.


I often prefer to work from end to start on runs as it seems to take less rework and adjusting that way.  Starting at the end of this one, here are a few things to keep in mind: when the ball is using and running along the semi-circle rail at the end of this run, it’s important that it lines up with, and does not overlap, the blue arch that it feeds, otherwise the ball will snag:


Similarly at the turn, the rail catches the ball close to where it comes in off the ramp.  Where the ball comes off the red arch, the arch is not on the very edge of the building board but instead ~1/4 of the way in, to release the ball so that it rolls down the middle-ish of the board:


Take a look!  You can see that as the ball runs its course, it bumps the pieces around a little bit.  Sometimes the little adjustment makes it run smoother the next time, sometimes you need to put it back.  When you find a position you like, you can weight the pieces by adding something on top or back them up with heavy parts so they stay in place.




This next run uses the Stepped Pyramid (large), Stacking Bridges, Sloping Blocks, Stepped Roofs, and Colour Charts Rally.  The Large Rainbow and Semi-Circles were used at the end to catch the ball so I didn’t have to keep chasing it after each run!



The more complicated a marble run set-up gets, the more important it is to start building from the end of the run, then make it longer by making it start a little higher, and a little higher, testing frequently as you go.


This one was built in 3 stages; always before moving on to build the next stage, the current section was tested and fine-tuned to ensure the marble stayed under control.

Stage 1 used Stepped Roofs and the 4th of the Stacking Bridge as track:


The Stepped Roofs are supported by Rally Charts to bring them above the catching tray, and the bridge is supported by two pieces from the slopes set.  Blocks from the Stepped Pyramid provides support for the green slopes.  Notice that the beginning and end of the bridge are at approximately the same height.  When the bridge “slopes” down, the ball gets moving too quickly.  When that happens, not only does it get out of control, you also don’t get the same sound on the Stepped Roofs at the end.

Stage 2 is very similar in construction except that stepped roofs lead into the bridge:


This one uses the next sized bigger of the Stacking Bridge; Sloping Blocks are used again to support the Bridge; and more pieces from the Stepped Pyramid to support the Stepped Roofs.  Again, notice that most of the total drop across this portion of the run comes from the slope (stepped roofs) at the start, and the Bridge begins and ends at approximately the same height.  The green Sloping Block after the bridge is just a tad lower than the edge of the bridge so the ball doesn’t snag and get stuck.

Stage 3 is similar in nature, but took more adjusting to get the heights right:


Again, the Sloping Blocks provide the supports for the bridge and the entry to the bridge, and the stepped pyramid provides the bulk of the elevation. In this segment, I also needed smaller height adjustments from the rally charts to get the height of the bridge and the slope just right. It took a little bit of guess and check work to find a slope and a height that would get the ball rolling and keeping it moving without sending it flying so fast that it skipped off the track.  

After getting the basic structure built, there’s some fine-tuning and detail work to add.  At the start, the top two slope pieces are set just a little bit apart.  This creates a straight track/ trajectory for the ball and helps start it moving in a straight path.  At each slope/ bridge/ steps interchange, make the transition as tidy and straight as possible to avoid redirecting the ball.


As you test the run, keep checking the transitions to ensure that the next portion of the run always starts below the previous.  Parts shift as you test them and you may have to reset portions of it more than once as you fine tune it.

Next, add rails wherever the ball seems tempted to pop of the track. For me rails were needed at the higher set of stepped roofs and in both lower bridges.


When you test the run and see the ball popping off the track, try to start the rails just a little before the spot the ball seems likely to veer off.   This reduces chances that it can snag on a small corner and bounce even farther off course.  Here, the “X” marks the spot the ball kept popping off the track for me, so I made sure the rails started a little earlier.


Be sure to turn on the sound for this one!

I always enjoy sound the ball makes bouncing down the steps.   When the ball moves too quickly it sort of skips over, so in this run I tried to control the momentum by limiting the slope of each section.   While it was in works, this one took quite a bit more adjusting throughout the build to keep it in good shape.  The kids usually love being in charge of fixing pieces that skootch out of alignment, and I love the lesson for them in how tiny adjustments can make a big difference!  My son also loves being the rail-builder—if he had his way we’d hyper-re-enforce every bit of the track!



This next run uses the Stepped Pyramid (large), Stacking Bridges, Rainbow, Semi Circles, Building Boards, Basic building set Stepped Roofs, and Colour Charts Rally.


This one I built alone, then left it out for the kids to find when they got home from a birthday party.

It bears repeating: the most effective way to build these is to start at the end!  If for no other reason, so your marbles don’t go all over the room as you build and expand!

As the runs get more complex, it's often smart to shift to the marbles instead of the small balls as they have less momentum for the speed and are less likely to bump pieces out of place.   This one here is built for the Grimm’s marbles (Grapat marbles probably work just as well, but we don’t have those).


Starting at the end, I used the 2nd and 3rd smallest bridges to create this swoop down, up and into the blue arch catcher.  Line up this join as smoothly as possible so the ball doesn’t snag, and then put the other end of the bridge on top of the semi-circle base of the catcher at the end.


The inverted bridge is supported by the smallest piece from the Grimm's Large Rainbow.  The smaller Semi-Circle is supported by the two yellow half-circles from the Grimm's Basic Building Set as well as a "2 cube” block.  The large semi-circle is supported by a green arch and a green elbow from the Basic Building Set.


A top view shows that the semi-circles are not fitted exactly to rainbow arches, but rather a bit bigger.  This gives wiggle room in case a piece gets bumped, and more space to set up the parts.  Notice that the green arch releases the ball towards the center of the swoop, and the ramp feeding the green arch drops the ball all the way inside the arch.  The ramp leading from the yellow arch to the green arch rests on the same piece that is supporting the upper platform so that the marble can move smoothly from one to the next.  The yellow rainbow arch hangs over onto the ramp to help establish the right trajectory.



The last piece of the run to build is the top—and its my favorite part!  The support for the bridge comes from the Basic Building Set (arch + two corners), and the support for the steps is made with pieces of the Large Rainbow.  Check out the alignment of the steps and the swoop if your marble is popping off the track a lot.


The jump is short—just barely enough space to pass a marble between, but the right spacing will vary depending on the exact angle of your swoop, so plan to adjust and check a few times.


The last step is adding the rails.  The first two at the top of top ramp are set at an angle to help catch and funnel the ball onto the course.  At the end, it opens a little to line up with the yellow arch.  Again, leaving the yellow arch, pay attention to how the arch and rails line up.


For the sake of an easy-to-watch movie, I spent extra time tweaking each bit of this so it would run smoothly without any rails, but with kids involved I’d recommend adding the rails.  

Happy Rolling!