I recently started experimenting with GBC machines build out of LEGO.

Ball bearings are ideal as balls (have a lot of momentum due to their weight), but are also impacting on the LEGO bricks hard enough that (eventually) they make the plastic crack. (This limits what you can do in the GBC design. You need to avoid large drops or high-speed bumps into end-stops.)

So I'm currently using glass marbles for balls at the moment.

Ideally I would like to use LEGO for the balls.
I realize they would be very lightweight which poses some design issues for some of the mechanisms, but finding solutions to that is part of the fun.

Unfortunately I don't seem to be able to find either single piece LEGO balls or sets of multiple LEGO pieces (like 2 half-domes) that together form a proper ball.

I'm looking for a ball shape with a diameter of at least 2 studs. (Between 2 and 3 studs would be perfect for my purpose, but somewhat larger would be fine too.)
I'm OK with something that has a hole into which an axle, pin or stud can be fitted.
I'm NOT OK with a stud sticking out, because that would affect the rolling behavior too much. A recessed stud that doesn't stick out beyond the outline of the sphere would be OK.

If a true ball/sphere is possible in LEGO, what piece(s) do I need ?

  • 3
    Defining "GBC machine" in the question may be helpful. Searching implies "Great Ball Contraption." Jun 5, 2022 at 22:10

3 Answers 3


There are several ball designs that fit your needs (and are commonly used for GBC machines) - a selection :

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  • 4
    These are larger than the question was asking for, but for completeness it's also worth mentioning the larger 6.5 stud duplo balls, most famously used with an Indiana Jones set to recreate an iconic scene from Raiders of the Lost Ark. Jun 4, 2022 at 16:16
  • 1
    @Nathan, perhaps add this as an answer ? Also note that the duplo balls come in robotic and education sets... Jun 4, 2022 at 17:56
  • 2
    I had no idea I had so many options. I've never been into Bionicle stuff so I had no idea these existed, but the Bionicle balls fit my use-case perfectly as I'm currently using 16-17mm glass marbles. And they are readily and cheaply available on BrickLink in a whole range of marble-like color-patterns. I've just ordered a whole bunch of them.
    – Tonny
    Jun 5, 2022 at 8:55
  • Yeah, I assume I am not alone wishing the GBC standard had called for the much cheaper Zamor spheres. I still regret not buying just a boatload of basketballs when I saw them in a bin at LegoLand California about a decade ago.
    – RSchulz
    Jun 8, 2022 at 3:16

If we're going to mention much larger spheres and sphere-like objects (and I don't see why not), there's also:

  • 60934 Bionicle Tridax Pod Half


  • 61287 Cylinder Hemisphere 2 x 2 with Cutout (I know it as Jack Sparrow's globe)


  • 98107 Cylinder Hemisphere 11 x 11, Studs on Top (usually decorated)


  • 852171 Phantoka Ball Shooter, along with 852279 Accessory Pack EVA Balls (neither of which I'd ever known of before today)



  • 1
    If we are wanting to be comprehensive, there is also the Magnet Ball, Technic Ball Joint (I know you mentioned in your comment), Technic Ball Steel, and two of these halves can be connected with a tyre. Jun 6, 2022 at 23:25
  • @MatthewJensen oops, I forgot about the Magnet Ball (which I think I have from some portion of that Harold Potter set) and the Ball Turret half. But those Steel Ball pieces were a surprise! I wonder how many GBC components one of those would destroy.
    – RSchulz
    Jun 8, 2022 at 3:14
  • 1
    The magnet ball could be interesting for GBC's, being weighted to one side to potentially make some cool kinetic effects. One could maybe design a 'stronger' GBC layout for the steel guys! Jun 8, 2022 at 4:52
  • I wonder if I should include the Jurassic World Gyrosphere <bricklink.com/v2/catalog/catalogitem.page?P=20455>
    – RSchulz
    Jun 21, 2022 at 23:28

Also Lego set 7029 has a plastic "boulder" that could be an option.

  • 3
    I looked at the inventory on BrickLink.com, and the only sphere is the Zamor sphere that Sander De Dycker already mentioned. There's the Technic "ball", but it's rather non-spherical, so I didn't include it in my answer either. Or are you thinking of some other piece?
    – RSchulz
    Jun 6, 2022 at 2:52

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