Lego Technic Gravity powered Pendulum Clock with 12-hour striking mechanic

Taking Time
Lego Clock M/305N

Lego Technic Gravity powered Pendulum Clock
with 12-hour striking mechanic

Watch here the BTS-Video
   • BTS Creating the Lego Technic Gravity powe...  

The building period including the first prototypes spans from March 2018 until September 2019. The 3D Model was built, when the clock was almost finished. Filming took place from March to May of 2021. Video editing and the 3D-work was done from September until November of 2023.
As you can see, 'taking time' is starting to be a theme of greater scope in this project.

Parts:
I do not have an exact count of the parts. According to my 3D Model there are about 980 pieces. However, the 3D animation shows only the parts that are functional to the clocks mechanisms. So with all the additional structural elements i would guess that somewhere between 2200 and 2600 parts were used. Please consider this a wild guess. Besides the bell, the strings and steel balls in the weights only original LEGO parts were used. None of the parts were altered to support the clocks function.


Complications and Functions:
Skeleton-type clock construction
Modular concept
Three-handed clock
Anchor-Galileo-Hybrid-Kindish escapement
Gravity driven powertrain
Clock weight: 1.610 g
Bell weight: 784 g
Two automatic electrified rewind systems for clock and bell

Controls for:
Hand positions
Escapement lever resting position
Setting height position for weight auto-rewind frame
Clock/Bell-Offset (the little Bridge in between the two main structures)
Hour setting (bell intern) for striking release
Changing length of pendulum for fine tuning the speed

Auto Rewinding:
I decided at a very early stage that I want the weight to automatically rewind. Because why not. The motor is attached with a differential to the powertrain. While the clock is running and the weights are pulling the drivetrain the motor shut-down is blocking the exit in the differential so all the power provided by the weight is going to the clock. By falling slowly the weights extend an actuator with a little fork at the end. In this fork, a lever connected to the battery box has it's loose end with some play in both directions. The fork moves now forward until it touches and pushes the lever and starts the rewinding process. This makes sure, that while rewinding, it will take some time until the motor shuts off again. It is a bit hard to explain precisely. In the BTS-Video you will find some visual representation about said functionality.

Accuracy and Runtime:
Due to the tolerances between LEGO gears, there is quite a backlash building up until it shows its effect on the second hand, sometimes "hopping” back and forth. I tried to avoid this as much as possible but it is now what it is. The clocks offset after 24 hours was about 5-7 minutes. The longest uninterrupted runtime, with help of the automatic rewinding system, was close to 4 Weeks until the battery for the Clock rewinding ran dry and the weight drops on the floor eventually stop the clock.

A huuuuge helper to achieve this was Sariel's Gear Ratio Calculator. Thank you for putting this site up.
http://gears.sariel.pl/

Bell striking:
The striking complication was a real challenge and took several rebuilds. It is counting the hours up to 12. For the warning I used a little weight. The warning occours about 3,5 Minutes in advance of the actual striking. While the clock strikes, a flywheel with a clutch controls and balances the power input of the bells own powertrain so it runs smooth and serene. This actually works like a charm. For the principal mechanism i relied heavily on the following videos which I found on YouTube:

David Couch's Striking Mechanism in LEGO by @KEvronista
   • David Couch's Striking Mechanism in LEGO  

lego clock complication - striking train by @KEvronista
   • lego clock complication - striking train  

Meccano striking clock mechanism by @deeceefour
   • Meccano striking clock mechanism  

Without these Videos I would not have succeeded, that's for sure. Thank you.


Other inspirations which I inhaled while i was deep in the building phase:

LEGO skeleton clock - ver. 2 by @KEvronista
   • LEGO skeleton clock - ver. 2  

Make Your Own LEGO Skeleton Clock by @KEvronista
   • Make Your Own LEGO Skeleton Clock  

Lego Technic Congreve clock by @DrDudeNL
   • Lego Technic Congreve clock  

And more or less every other clock related video a could put my eyes on. Was it made of metal, plastic, wood, electric, very basic, totally over the top or something completely else. Thank you all for your videos.

Time left? Take a detour: marcobernd.de

Music
Monumental by alexbird (audiojungle.net)