Lego GBC Tower Crane (Bridge Module) is a Utility Module for bridging gaps in  Table Layouts and was designed by Lawrie George.

The module stands over 80″/200cm tall (when on a table) and spans gaps of 36″/91cm, it is fully self-supporting and uses a 750gram counter-weight to balance the jib.

Idea and Research

My research was broken into finding real life cranes I could style my model from and search for key mechanisms to use.

The dimensions of the Crane are based on Stuarts bridge module, which is designed around a standard doorway 80″x30″.
I also took queues from Philo’s tower crane in regards to stringing the trolley.


Once I had settled on the idea of a Tower Crane the next step was to create a prototype that would confirm that a structure of this size was even possible.

As you can see from the photo all the main elements are in place, the tower, jib, counter-jib, and counter weight.

Night Lighting

The module is setup for nighttime running using a mix of my custom Lego UV/Led lights, and 12V DC LEDs wired to Lego plugs.


Videos of the development and operation of this module.

  1. Inspiration and Prototype – 0:0
  2. Digital Design – 1:26
  3. Ordering Parts – 3:44
  4. Building – 3:56
  5. Assembly – 5:54
  6. Running – 9:00

An early testing video.


The Mast and Jib were made up of identical sub-assemblies, making the basic structure quick to assemble.


  • The crane is designed to fold up and fit in a lamp style box, this makes setup and teardown very quick with the tradeoff being space needed for transport and storage.

Stringing Trolley

  1. Attach string to side of trolley opposite pulling direction
  2. Thread the string around the tensioner and run in through the middle of the jib
  3. Run the cord around the inner pulley on the jib
  4. Wrap the thread around the drum 3 times.
    1. This when tensioned provides enough friction to move the trolley.
  5. Run the string under the jib and attach to opposite side of the trolley.
    1. Ensure the spring is ½ way depressed to provide tension.

Stringing Hook

  1. Attach the string to the drum gear.
    1. Wind 2-3 turns around the drum
  2. Run the string under the boom and over the trolley pully
  3. Thread through hook.
    1. With the crane assembled, ensure the hook touches the ground
  4. Thread over the other pulley on the trolley
  5. Attach string to side the pin at the end of the jib

Weaving Catch Net

Nets are woven together using string to form a cone shape.

There are 3 rows

  1. 7 nets
  2. 3 nets
  3. 2 nets

Balancing the Jib

The jib needs a counter weight of 750grams to balance effectively.

The counterweight is designed to take Lego train weights but can also be filled with other objects to achieve the required weight.


Pieces Cost Difficulty
>3000 $$$$ Complex

A render of the completed model.

Revisions to the digital model

For this module, I have maintained the digital design and you can read about the changes below.

  • Update design of anti-jam kicker to have more weight
  • Raise the hight of the lift conveyor to give balls more time to drop
  • add more chain guides to stop chain jams at bottom
  • Add a ram to eject balls that return down after triggering the anti-jam kicker.
  • Increase counterweight size to fit 14 train weights
  • Add a blue double pin to the end of every liftarm to brick connection
  • Add missing inner bracing to bottom of mast
  • Remove bracing that was fouling with input
  • Add missing bracing to top of mast
  • Add pins to reduce bowing under load
  • Fix two pins in same hole
  • Fix missing connector
  • Some improvement to order of assembly steps
  • Change gear transfer between crane and input bit as knob-wheels were jamming.
  • Add a clutch on the input bin drive
  • Increase the height of the catch arms at the end of the boom
  • Shorten the Jib stay to make the boom flatter
  • Add additional lift arms to reduce load on jib support axle
    Make support axle longer
  • Increase Counter-Jib ballast weight to 750g to flatten the jib
  • Stop flag from rotating
    Note: bar should be swapped for tube if the light is lit up
  • Space IR receiver out more to stop it fouling on motor when jib is folded down
  • Fix pin misalignment indrawing
  • Add ½ pins to stop liftarm from moving
  • Modify Platform to accept downlights
  • Make drivers cab removable for easier packing
  • Remove battery pack as it is inaccessible during shows.Requires cable run down mast instead
  • Change Jib Pivot to stop it fouling on tower platforms
  • Add a positive stop for motor rotation of hook up/down motion
  • Split out ramp for packing
  • Change gearbox design to
    • Support removal for packing
    • Have auto up/down mechanism
    • Be disconnected from input bin
  • Reduce size of tabs on counter weight to make more room for battery
  • Increase bracing on top
  • Additional lift arm bracing in top
  • Remove last guide lift arm as the balls fouled with it when going around the gear
  • New counter jib tie design
  • New jib tie design
  • Updated Kicker to an anti-jam design
  • Updated jib end to improve drop accuracy and stop balls bouncing off the top
  • Add more wheels to trolley to stop jamming while moving
  • Tensioner for trolley in-out rope
  • Update Chain links to have a spacing of 9 between pins and a total of 233 links (9 x 26 = 234 – 1 = 233), this gives a top speed slightly faster than 1 ball per second and will allow the crane to keep ahead of surges.
  • Add initial wedge to guide balls to chain
  • Add more black support liftarms to inner structure
  • Increase strength of bottom support frame
  • Drive gearbox update
  • Update input bin to include agitator
  • Change output ramp design
  • Add feet to tower
  • Add braces to increase tower rigidity
  • Add remote for trolley movement and hook up down (from Sariel’s design)
  • Wheels stop chain from moving and the pins jamming on the tower
  • Ball guide stops balls from falling off pins
  • Change the cab opening so the mini-figure can be replaced