An attempt to create a solar orbit out of Lego and simulate the movement of celestial bodies
Designing a Lego orrery | Marian's Blog
https://marian42.de/article/orrery/
According to Marian, the idea of making a solar orrery out of LEGO was inspired by a model of the Earth, Moon, and Sun orbits designed by Jason Aleman, who creates architectural and LEGO assembly models and kits, in 2016. Aleman's solar orrery can be seen in the following movie.
LEGO Orrery - Earth, Moon and Sun - YouTube
Inspired by Aleman's model, Marian is working on building a Lego orrery of his own design. Marian first focused on the Earth's axis of rotation. The Earth's axis of rotation is tilted at 23.5 degrees to the orbital plane. This means that the axis of rotation in an orrery does not point straight up, so the mechanism that rotates it must also be positioned at an angle. Furthermore, since this axis always points in the same direction, not only does the Earth itself rotate, but the part that supports the Earth also needs to keep rotating to maintain the orientation of the axis.
So Marian used angled connectors to build a tilted holder for the Earth. Here's the Earth-side mechanism of the LEGO orrery:
The plane of the Moon's orbit is also slightly tilted to the plane of the Earth's orbit, rather than parallel to it. The actual tilt is 5.15 degrees, which would be barely noticeable even if it were modeled accurately. However, Marian said that the inclination of the Moon's orbit plays an important role in explaining when solar eclipses occur, so it would be useful to model the inclination of the Moon's orbit.
To recreate the motion of the moon, which is at an inclination of 5.15 degrees around the tilted Earth, it is necessary to make the moon move up and down around the Earth. Marian says he got a hint for this mechanism from the following movie, which recreates
A Lego Technic Tellurion - YouTube
As a result, Marian's model below incorporates four mechanisms that rotate at a constant speed: the Earth, a base for the Earth that rotates to keep the Earth's tilt in place, the Moon, and the Moon's tilted ring.
Looking at Marian's LEGO orbit from below, the rotation mechanism is arranged as follows: There are four mechanisms: the Earth, the Earth base, the Moon, and the Moon's tilt ring, and the main arm adjusts the gear sequence to reproduce the cycle of the Earth orbiting the Sun, which takes about 365.25 days.
In this case, Marian created a LEGO gear sequence calculator to calculate how the available gears can be combined to achieve the desired transmission ratio.
Lego Gear Ratio Calculator
https://marian42.de/gears/?targetratio=17/23&error=default&incl2d=false&gears=default
In the end, Marian's LEGO orrery has 70 gears arranged as shown below. Since friction increases little by little with each gear added, it was a big challenge to 'make the orrery move smoothly.' As a result, by fine-tuning the gears through detailed calculations, the Earth's orbital period is within 0.18% compared to the actual value, and the Moon's rotation and revolution periods are within 0.1%.
Once the moving parts were complete, the base to house the motor and other components was created. The first base they created was abandoned due to the extremely loud motor noise. To improve the usability of the orrery, they considered the design of the base as an artistic challenge rather than a technical one. Below are the base designs that Marian considered during production.
You can see how the Lego orrery that Marian finally completed works in the following movie. The design of the base is designed to rotate the arm by moving a lever rather than a motor.
Sun Earth Moon Orrery (Lego MOC-88534) - YouTube
Marian is also planning to design a way to recreate the same LEGO orrery using fewer parts, as well as ideas for replicating the revolutions of not only the Sun, Earth, and Moon but all of the planets in the solar system, and to assemble an orrery designed using acrylic sheets rather than being limited to LEGO parts.
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