Aaron Klapheck's Website

Click on Display Settings

Under grid click show grid, turn gravity off, under units set the length to mm.

Display the edit toolbar located in toolbars.

click the Cylinder icon.

Build a cylinder in Nastran.

Set the cylinder dimensions to the following: radius = 5mm, height = 400mm.

Set the position to the following: x = 0, y = 0, z = 200.

Copy this cylinder. After copying this cylinder paste it into the model.

Change the height of the cylinder to 800mm.

Position this cylinder to the following location: x = 400, y = 0, z = 180 (location of point C). The angle this part makes with the x-axis is 36.9 degrees (obtained form the problem) which is 53.1 degrees with reference to the vertical axis (the complement).

Copy body[1] again and paste it into the virtual model.

Fix the position of body[1] and body[2].

Change the height of body[3] to 500mm.

Click the Move button.

Move the cylinder in question (body[3]) to approximately midway between body[1] and body[2].

Click the Rotate button.

Rotate the cylinder so that it is horizontal.

Using the Move and Rotate commands to position body[3] so that one of its ends is close to body[1].

Rotate your view around so that you can see the "top" surface of body[3] and can also see body[1]. Then click Spherical Joint on Slot from the pull down menu.

Select the "top" surface of body[3].

Then select body[1] (anywhere on the cylinder). Once you click body[1] a message box will appear. Make sure that the Face-to-face ratio button is selected then click OK.

Notice that the spherical joint is sliding on the wrong axis. This problem will be solved next.

The small pane on the left of the screen is called the Object Browser. Left click on the spherical joint inside the Object Browser and select Properties.

Have this joint slide along the Y-axis. Note: the coordinate axes are defined in terms of the object selected not the overall world axes which can usually be seen in the lower right of the screen.

Notice that after this change has been made the spherical joint changes from a solid ball to a wire frame ball. Whenever a constraint is wire-frame it means that it is not working. In order to activate a constraint right click on it in the Object Browser and click Join.

For this case we want to assemble both body[1] and body[2] so that they are both touching each other. Make sure the Assemble ratio button is selected then click OK

Position the other end of body[3] (the "bottom" face) so that is is next to body[2]. Before adding constraints to these two bodies notice that body[1] is too short so that the joint constraint is floating in air. We will fix this problem first.

The problem is that body[1] is too short so simply increase its height to 800mm.

Make the same spherical joint connecting the bottom face of body[3] to body[2] using the same steps mentioned previous.

Notice that this slot is defined along the wrong axis. Simply change the spherical joint to slide along the Y-axis as done previously. This works because the axes are defined in terms of body[2]. After this last step rejoin the spherical joint.

At this time you may notice that the two joints are not centered. To center them select each of the two points that define the position of the joint and center them. To do this select the Properties of each coordinate making up the joint from the Object Browser.

Center coordinate[6] by setting the x, y, and z coordinates the those shown in the picture.

Center coordinate[5] by setting the x, y, and z coordinates the those shown in the picture.

Once this is done then re-join the spherical joint.

Repeat the process for the second spherical joint so that it appears as it does in the picture to the left.

The next step is to apply a velocity to the second spherical joint. this can be done by selecting the Linear Actuator from the drop down menu.

Select the "top" surface of body[2].

Then select body[3].

Select one of the two points defining the actuator and set it to the coordinates shown in the picture to the left.

Define the velocity of the Linear Actuator to 200mm/s.

The finished physical model should resemble the picture to the left.

The next step is to measure the various positions and velocities of certain coordinates. We first do this by selecting coordinate[9].

After selection of the coordinate then measurement of the position of this coordinate will then be achieved by making the following menu selections depicted in the picture to the left.

Next we select coordinate[5].

Then we measure its velocity.

The final model including measurement devices is shown to the left.

The motion of the disk

The final animation should resemble what is shown by clicking on the picture to the left.

After running the model, position the horizontal dashed line so that the position along the z-axis of coordinate[9] is approximately equal to zero (zero is along the "y-axis" in the graph). Movement of the dashed line is done by cycling the frames of the movie until a desired point is reached. Note the coordinate in the bottom left of the graph shows where the curser is located. For the picture to the left the curser is located on the point where the dashed line hovers directly above the intersection of the zero point and z-position (or pretty close to it). Once the dashed lines are nearly on the intersection (-1.13mm is very close to zero) then we look at the velocity, which is the next step.

The velocity of the spherical joint (representing collar B in this case) is given in the lower left of the graph and is shown to be -336mm/s, which is very close to the theoretical value of -333mm/s. If we wanted to get better accuracy we could have used more frames per second for the animation (note that this will take more time and computing power).