One of the simple and basic principles of GBC is motion. Therefore, it’s important that I spend a couple of lines explaining you how to bring motion to your module.

Usage of Lego Technic motor is a must in GBC
Usage of Lego Technic motor is a must in GBC

Of course, motion can come from you, manually rotating one of the wheels, giving to the module the bit of rotation it needs to move some of your balls. However, the best way to action your balls at a regular speed remains the usage of Lego Technic engine, which becomes nearly a must-have when dealing with GBC.

I must confess that when I started with GBC, the last image I had about Lego engine was the old battery pack that was supplying power to my fist Lego train (yes… guess my age!) Outdated, somehow… But it was my pleasure to see that, if some brand new engines and motorized parts have popped up, the basic fundamentals were still intact: A battery pack, powered by standard AA batteries, with a standard 3 positions interrupter (stop, start, reverse), linked to a standalone engine rotating at stable speed.

However, one big difference with my childhood engine is without any doubt the power it delivers. As a small experiment, I have tried to plug my old Lego motor to a freshly made GBC module. It was worth the try… to confirm that if you own an old Lego motor (from the 80’s), you’ll have unfortunately to invest if you really want to bring motion to your GBC modules.

Lego is proposing several kinds of motor, each one having a letter indicating power capabilities, a bit like a T shirt size. This way, the M-motor will deliver you standard power. And the more you go along letters, the more power you’ll get out of the motor.

By experience, a standard M-motor will allow you to run most of GBC modules, even a large majority of the masterpieces. However, in case you have complex gearing/wheel structure or if your rotation is spread across numerous zones of your GBC module, going for a L or an XL motor might be required.

'8293-LEGO® Power Functions Motor Set' is perfect to acquire your first motor
‘8293-LEGO® Power Functions Motor Set’ is perfect to acquire your first motor

To begin with GBC building, here are some pieces of advice regarding motors: ➡ Start with a standard M-motor. This is plenty enough for most of your buildings. ➡ When buying motors, do not necessary start with (an expensive) Mindstorms set but rather with simple standard motor pack (well. It’s anyway a free world dude) ➡ The Lego set “8293 – LEGO® Power Functions Motor Set” is good value to start. Even though you might not need the lights and the switch, this set will offer you a battery pack and a basic M-motor. That is enough for you to start ➡ Purchase some extra cables and motors directly on Lego Shop website. Used Lego motors are, on the most popular Lego marketplaces, not really cheaper than the ones one can buy on the official Lego website… (they are even sometimes more expensive !)



While experimenting with GBC modules, you’ll quickly discover that the parts velocity can differ from one location within the module to another, even though the motor rotation speed is constant. This is brought by the gearing reduction/gearing up of wheels, one of the basic principles of GBC module “physics”. As you will see, these speed adaption principles are heavily used by GBC module builders to orchestrate the motion speed within various parts of the module.

Gearing up
Gearing up
Several options are offered to you to alter the rotation speed delivered by the motor: ➡ The first option, and from far most common one, is to play with wheels to increase or decrease the rotation speed delivered out of the motor. Honestly, that is what makes GBC module so fascinating: the fact that a simple motor can steer an all-in-motion module (Ball Factory v2 from Akiyuki is the more impressive illustration of this!). That is what you’ll commonly meet while following building instructions. Note: to support you in gearing, I advice you to have a look at the following web page called LEGO™ Gear Ratio Calculator. The page allow you to virtually assembly wheels and give you some precious information about the speed, torque and rotation ratio. It also gives you some hints to place your wheels
Use the Train Speed Regulator to modulate motor rotation speed
Use the Train Speed Regulator to modulate motor rotation speed
➡ A second option is to use a Lego Electric Train Speed Regulator 9V (reference 4548). This part will not allow you to have a different velocity in various parts of the module. However, it will allow you to regulate the overall rotation speed that you want to see delivered to your module. You will often see such regulator appearing on the videos showing GBC modules, which proves it’s a must-have.



Using intensively your GBC module could be quite power consuming (even though I must say I was positively surprised by the low power consumption of the M-motor, which last quite a while with my initial set of batteries). You might want therefore to find an alternative solution to power your engines.

In my opinion, the following options are on the table:

➡ Use the standard battery-pack powered by standard AA batteries. It’s the cheapest option on the short run, but it might become expensive if you are plugging several motors onto the same battery pack (by the way, yes you can do this: 4 M or 2 XL motors on the same battery pack) or if you are keeping your module constantly in motion (for an exhibition for instance).

'8878-LEGO® Power Functions Rechargeable Battery Box' is useful if you are looking for constant power supply
‘8878-LEGO® Power Functions Rechargeable Battery Box’ is useful if you are looking for constant power supply
➡ Use standard battery-pack powered by rechargeable batteries. The price of the rechargeable battery (you need 6) will augment significantly the initial bill; however, it’s a one-shot cost as you will not have to pay for some extra AA batteries later. I would consider this as the best option

➡ Buy a Lego power supply (”8878-LEGO® Power Functions Rechargeable Battery Box’ is useful if you are looking for constant power supply) to plug your motors. This is the most expensive option as the price of the device is a bit…over-valuated (despite the first class quality you always get from Lego). For me, it’s an excellent compromise if you do want to exhibit your module over a fair or show as power flow is delivered in a non-stop and constant way. Pay attention to ‘45517-Transformer 10V DC’ being mandatory for this battery to work… (an expensive additional line on the bill)

➡ Last but not least (I’ve kept the best option for the end), use the “4548 – Lego Electric Train Speed Regulator 9V” I’ve mentioned in the previous chapter. This option offers you, for a good price, constant power, that you can even modulate. It’s a AA battery free option. If you do not forget to also buy the associated adaptor, you have here a must-have option (for home or exhibitions)! If you choose this option, do not forget to buy a “8886 Extension Wire (20 cm)” or a “8871 Power Functions Extension Wire (50 cm)” as these two wires are the only ones which can plug on the Train Speed Regulator 9V.

Lego M-motor is convenient and efficient enough for your first buildings
Lego M-motor

1. The “8293–LEGO® Power Functions Motor Set” is good value to start 2. Find directly on the Lego Shop website the motors and cables you need 3. Use the wheels to adapt the rotation speed in various parts of your GBC module thanks to gearing

Adapt the power supply to your needs:
Speed Regulator 9V

1. Start with standard battery-pack powered by standard AA batteries 2. Enter into another dimension thanks to the “4548 – Lego Electric Train Speed Regulator 9V” (with adaptor and specific wire) that you can find of Lego marketplaces at a decent price



  1. The standard M motor rotates why too fast for most GBC’s, so tend to go for a slower XL motor which also has far more torque. Could also use the in-between L motor but tend to be double the price of XL as smaller 3 stud diameter popular for powering motorized cars. Even then will typically still need to gear down the XL motor. Going back to 80’s Technic the most common method is to use an 8 gear in the XL motor to drive a 24 gear to reduce the speed by a third.
    If you wish to control the speed directly forget the 4548 as hard to find so expensive and need transformer. Instead go for the new power-up motors which have controllable speeds using downloadable app. These are more economical to obtain within recent flagship sets than purchasing individually.
    Finally, if starting with little Technic inventory and no motors, purchasing a new Mindstorms robot inventor kit 51515 is probably the best way into GBC as well as learning about the new Spike technology.

  2. Just starting out. Looking at the electric train controller on ebay which I can get box only from Europe at good value, and the cables you mention are cheap enough to buy. You mention a specialist transformer in the section above for the rechargeable power box, but do you need a specialist transformer for the train controller please?
    Its a UK one I am after


    1. Hello kazbloom,
      yes, you also need a special transformer for the train controller.
      I advise you to look at BrickLink, searching using reference 4548


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