Planar and Spatial Kinematic-Chains.

Kinematic-chains that you can represent on one plane are 'Planar Mechanisms'. If you must use more than one Plane, then the mechanism is said to be a 'Spatial Mechanism'.

The examples in this topic help you identify whether the mechanism you want to model is planar or spatial.

See also: Mechanism

Note: We will learn how to add 'Solids' to Parts in Tutorial 3 and Tutorial 4.

Example Planar and Spatial Mechanisms

Concealed Door Hinge

A Six-bar mechanism.

This mechanism allows the door to rotate by 180º and also hides the mechanism within the door and door frame. There are usually two or three hinges on each door.

All the Parts can be represented on one Mechanism-Plane.

In MechDesigner, it is a Planar mechanism.


A four-bar mechanism, and a cam.

A Slot-Cam rotates a shaft by 90º. A block on the shaft holds the stem of a vacuum cup, with the stem at 90º to the shaft.

As the shaft rotates about its axis, the stem of the vacuum cup also rotate about its axis.

In MechDesigner, it is a Spatial mechanism.

Car Boot or Bonnet (Trunk or Hood in USA)

There is a six-bar mechanism at each side of the Boot or Bonnet. (Trunk or Hood).

There is also a 'Spring Damper' between two of the Parts in this model. You can model this dyad with an RPR dyad. Even though one end of the Spring Damper looks like a Ball-Joint, you can model it as a Pin-Joint.

In MechDesigner, it is a Planar mechanism.

Garage Door

In this model, there is a six-bar planar guidance mechanism at each side of the garage door.

In MechDesigner, it is a Planar mechanism.

Kitchen Cabinet Door Hinge

There is a hinge at the top and bottom of the kitchen cabinet door.

This hinge is a six-bar Planar Mechanism.

In MechDesigner, it is a Planar mechanism.

Simple 'Bell-Cranks', with levers on different Planes

The cam-follower lever may be offset to the lever that is the 'crank' to the slider.

In MechDesigner, the cam-follower lever and the crank are modelled with one Part.

In the machine, the two levers are often physically two separate lever, with a part at each end of a shaft.

In MechDesigner, it is a Planar mechanism.

Tutorials and Reference Help Files for MechDesigner and MotionDesigner 14.2 + © Machine, Cam, Mechanism, and Motion Design Software by PSMotion Ltd