What is identified by the first digit in the symbol number of a moving joint?

In the context of moving joints in machinery, the first digit of the symbol number identifies the type of joint and its specific characteristics. When that first digit is '1', it indicates that the joint is categorized as a hinge joint. Hinge joints are capable of allowing rotational movement around a single axis, much like a door hinge, which is critical for many mechanical applications.

This method of categorization helps to standardize the identification of joints, making it easier for engineers and technicians to communicate about the types of movements and constraints that different joints will exhibit. By defining the joint type based on the first digit, it simplifies the design and troubleshooting processes.

The other digits correspond to different types of joints or configurations, which are not associated with a hinge function, thus differentiating them from the specific behavior indicated by the first digit being '1'. This systematic approach is vital for understanding the functionality of mechanical systems and the interactions between various components.