Mechanical Monday – Geneva Mechanism

In all the years we build GBC we were always fascinated by the versatility and reliability of the Geneva mechanism. This mechanism, also known as a Maltese cross or trochoidal drive, is a mechanical linkage used in a wide field of application nowadays and for sure in the LEGO GBC madness we are in.

 

 

One of the key features of the Geneva mechanism is that it allows for intermittent or “stepped” movement of the shaft. This is accomplished by using a “locking” tooth that engages with the other teeth when the shaft is in a certain position, and then releases them when the shaft has moved a certain distance. This allows the shaft to rotate in discrete increments, rather than continuously.

The most common type of Geneva drive has four teeth, resulting in the follower moving in a stepped motion 4 times per revolution of the drive shaft. By adjusting the size and shape of the cam and the length and shape of the follower, the motion of the follower can be customized to fit the needs of a particular application. We have used it in our GBC 49 Geneva Drive (more on that below). The video here shows the cam to the right and the follower is the blue wheel on the left.

The Geneva mechanism has a number of advantages over other types of mechanical devices. It is simple and inexpensive to manufacture (in real life and to build in LEGO), and it is reliable and durable. It is also highly versatile, and can be used in a wide range of applications, from watches and clocks to machine tools and other mechanical devices in big automation processes.

 

 

 

History

The Geneva mechanism, as mentioned before also known as the Maltese cross or Geneva stop, is a system used to control the movement of a rotating shaft. It was invented in the mid-18th century in Geneva, Switzerland, and was first used in the watchmaking industry which was mainly located there. Here it was used to transfer rotary motion to the escapement mechanism of a watch. It has since been used in a wide range of mechanical devices, including printing presses, mechanical music boxes, and automated assembly lines.

The Geneva drive was first used in the watchmaking industry in the city of Geneva, Switzerland, in the late 16th century. It was used to transfer rotary motion to the escapement mechanism of a watch, which controls the rate at which the watch’s hands move.

The Geneva drive became widely used in watchmaking due to its simplicity and reliability. It was able to perform a wide range of functions with a minimum of parts, making it an essential tool for watchmakers.

Over time, the Geneva drive was also adopted for use in other mechanical devices, such as printing presses, mechanical music boxes, and automated assembly lines. It has also found a number of uses in the world of LEGO, particularly in Great Ball Contraption (GBC) machines.

 

Use Cases

In the world of LEGO, the Geneva drive has found a number of uses in Great Ball Contraption (GBC) machines. Overall, the LEGO GBC community is a creative and innovative group of builders who are constantly pushing the limits of what is possible with LEGO bricks and parts, in a technical part of view. The Geneva drive mechanism is just one example of the many ingenious solutions that GBC builders have developed to make their machines meet their goal.

 

GBC 49 Geneva Drive
We have used the mechanism in 2 GBCs at the moment but in the future we will for sure design new versions of this same principle to suit the need at that moment.
Recently we have released our GBC 49 Geneva Drive which uses this mechanism to make a full 4 step motion. LEGO has developed new parts which we found out are great to build a compact Geneva mechanism.

 

 

 

GBC 3 Ferris Ground
A golden oldie, and also not really shown in our current product range, is our retired GBC 3 Ferris Ground which also features a Geneva mechanism. Although this version works great it is not that elegant and compact as the version in our GBC 49 Geneva Drive.