What are the conditions for the existence of the crank in the hinged four bar mechanism

Sum of rod lengths: The sum of the lengths of the shortest and longest rods of a planar four-bar mechanism is less than or equal to the sum of the lengths of the other two rods.

In the hinge four-bar mechanism, if a rotating pair can become a whole rotating pair, one of the two components it is connected to must be the shortest rod, and the length relationship of the four components satisfies the sum of the rod lengths.

After selecting one of the components as the frame, the component that is directly linked to the frame is called the connecting rod, the component that is not directly connected to the rack is called the connecting rod, the component that can do the whole rotation is called the crank, and the component that can only swing back and forth in a certain angle range is called the rocker. If the two members connected by the rotating pair can be rotated relative to each other in the whole circle.

1. One of the connecting rods and frames must be the shortest rod in the four-bar mechanism;

2. The sum of the shortest rod and the longest rod length should be less than or equal to the sum of the other two rods (usually called the rod length and condition).

Crank - A connecting rod that rotates around the rotating pair on the frame.

The conditions for the hinge four-bar mechanism to have a whole rotation pair (the necessary condition for the existence of the crank) are: the sum of the length of the shortest rod and the longest rod is less than or equal to the sum of the lengths of the other two rods;

A crank is made up of the shortest rod and its adjacent edges.

The basic properties of the hinge four-bar mechanism: the sum of the lengths of the shortest rod and the longest rod is less than or equal to the sum of the lengths of the other two rods, and one of the connecting rods and the frame must be the shortest rod.

The four-bar mechanism of all the virtual spring moving pairs is called the hinged four-bar digging bureau mechanism, which is the basic form of the plane four-bar mechanism, and the other four-bar mechanisms can be regarded as evolving on the basis of it. In the hinged four-bar mechanism, according to whether the connecting rod can be rotated in a whole way, it can be divided into three basic forms, namely crank rocker mechanism, double crank mechanism and double rocker mechanism.

After selecting one of the components as the frame, the component that is directly linked to the rack is called the connecting rod, the component that is not directly connected to the rack is called the connecting rod, the component that can do the whole rotation is called the crank, and the component that can only swing back and forth in a certain angle range is called the rocker.

If the two components connected by the rotating pair can rotate relative to each other in the whole circle, it is called the rotating pair, and vice versa. In the hinged four-bar mechanism, according to whether the connecting rod can be rotated in a whole way, it can be divided into three basic forms, namely crank rocker mechanism, double crank mechanism and double rocker mechanism.

The plane hinge four-bar mechanism is the most representative one of the plane four-link mechanism. Its classification is far from covering all types of institutions in much of the literature, and there is no strict taxonomy. In this way, the problems are: incomplete understanding of the institution; Influence the usefulness of the institution.

The three basic forms of a hinged four-bar mechanism are: crank rocker mechanism, dual crank mechanism, and twin rocker mechanism. Their main characteristic difference is that different components are used as the frame, and different motion forms are obtained, which is referred to as the rack change.

No, there is a double crank mechanism, and the shortest rod is the frame.

1. The sum of the rod lengths is that the sum of the lengths of the shortest rod and the longest rod of the plane four-bar mechanism is less than or equal to the sum of the lengths of the other two rods.

2. In the hinged chain four-bar mechanism, if a rotating pair can become a whole rotating pair, one of the two components it is connected to must be the shortest rod, and the length relationship of the four components satisfies the sum condition of the rod length.

3. In the hinge with the existence of the whole pair.

In the four-bar mechanism, the rotating pairs at both ends of the shortest rod are whole rotating pairs. At this moment, if the shortest rod is taken as a frame, a double crank mechanism is obtained, and if any connected member of the shortest rod is taken as a frame, a crank rocker mechanism is obtained.

If the member opposite the shortest rod is taken as the frame, a double rocker mechanism is obtained.

4. If the four-bar mechanism does not meet the condition of the sum of the rod lengths, no matter which component is selected as the frame, the obtained mechanism is a double-rocker mechanism.

To sum up: the condition for the existence of a crank in a planar four-bar mechanism is the length relationship of the four rods, and the frame determines whether a crank will be present or not.

No, there is a double crank mechanism, and the shortest rod is the frame.