Apply the Constraints to the Piston and Crank

1. Click the Home icon above the ViewCube for an isometric view of the model.
2. With the  Selection Shape Point or Rectangle and  Selection Select Surfaces commands active, click one of the two cylindrical surfaces at the outside diameter of the piston.
   • Hold down the Ctrl key and click the remaining outside diameter surface. The piston should appear as shown below.

     

3. Click Setup Constraints General Constraint.
   • Activate the Tx and Tz check boxes. The piston will only be free to translate in the Y direction.
   • Click OK.
4. Right-click the Part 3 heading in the browser (tree view) and choose Select Subentities Surfaces. All the surfaces or Part 3 are now selected. 
5. Click Setup Constraints General Constraint.
   • Activate the Tx check box.
   • Click OK. The crank will be free to move only in the Y and Z directions.  Though not absolutely necessary, this constraint will stabilize the crank by preventing any twisting or bending due to flexure of the joints and will make convergence of the solution a little easier.  

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