To Enable Gravity
Select the Enable gravity check box on the External loads tab of the Analysis Definition dialog box when calculating DOF or running a dynamic, static, or force balance analysis. The enabled gravity effect is slightly different depending upon the type of analysis you run.
Dynamic and static analyses:
• A default value of 1 is assigned to a body with density in a mechanism assembly unless you set another value. Click
Mass Properties in
Mechanism Design or set the density in Assembly mode.
• If your mechanism includes bodies for which you have not assigned mass, you will not be able to run a dynamic or static analysis. This includes bodies and subassemblies comprised entirely of datum curves or surface features, as well as massless, volumetric bodies.
• If you do not select the Enable gravity check box, gravity will be zero, regardless of the values specified in the Gravity dialog box.
Force balance analysis:
• Clear the Enable gravity check box to assume a mass of 1 for bodies with no mass, and then run a force balance analysis without assigning mass to all bodies.
• If you select the Enable gravity check box, you must specify a mass value for all the bodies in your mechanism before you can run a force balance analysis.