Add features to the Skeleton model

1. Open crank_piston_skel.prt in Part mode.

2. Ensure that the length units of the part are set to millimeters to match those of the other components in the assembly.

3. Select the button to create default datum planes.

4. Create a sketched datum curve that represents the overall length of the assembly. Select DTM3 datum plane, and select the button. Select the button from the Sketched Datum Curve dialog box.

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5. Sketch the curve so that one endpoint of the curve is aligned to DTM1, as shown in Figure 2–10.

Figure 2–10

6. The first component in the assembly, bearing_journal_main.prt, is aligned to DTM1 of the skeleton. Rename DTM1 to reflect this alignment. Double-click on DTM1 in the model tree and rename the datum plane to [BJL].

The endpoint of the line should be aligned to DTM1.

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7. Create a datum plane offset from datum plane BJL. Use an offset dimension of [-107]. This locates the first instances of the piston, piston_pin, and connecting_rod components. See Figure 2–11.

8. Rename this datum plane to [PCR1].

Figure 2–11

9. Sketch a datum curve on datum plane PCR1 that controls the motion of the first piston. Use PCR1 as the sketching plane and DTM2 as the top reference. Use DTM3 and DTM2 as sketching references.

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10. Sketch the two line entities first and dimension them as shown in Figure 2–12. Create the circle to represent the path of the rotation.

Figure 2–12 A dimension symbol can

be changed from the default (e.g., d12) to help identify the dimension when it is modified and used in relations.

11. When the feature is completed, change the symbol of the angular dimension. Select the datum curve and click Edit in the pop-up menu.

12. Select the angular dimension and click Properties in the pop-up menu. From the Dimension Text tab, change the name of the dimension to [crank_angle] using the Name field. The sketch appears as shown in Figure 2–13.

Sketch the two linear entities first and then sketch the circle. The diameter of the circle should be driven by the length of the shorter line.

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Figure 2–13

13. Select the button to create two datum points. Create the datum points through the vertices of the datum curve shown in Figure 2–14.

Figure 2–14 Press the <Ctrl> key while

selecting the references to select multiple references for the axis.

14. Select the button to create a datum axis. Create the datum axes normal to datum plane PCR1 and through one of the datum points just created. Create a second datum axis normal to datum plane PCR1 and through the other datum point created in the previous step.

Select these two vertices to create the datum points.

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15. Rename the axes using the names shown in Figure 2–15. These axes are used as assembly references.

Figure 2–15

16. Create a datum plane offset from datum plane BJL by a distance of [-117]. Rename this new datum plane to [CRJ]. This plane is used to locate the connecting rod journal component. The sketch appears as shown in Figure 2–16 (axes display has been

disabled for clarity).

Figure 2–16

17. Create a datum plane offset from datum plane BJL. Use an offset dimension of [-127]. This locates the second instances of the piston, piston_pin, and connecting_rod components. Rename this datum plane [PCR2].

18. Create a datum plane offset from datum plane BJL. Use an offset dimension of [-163]. This locates the bearing_journal_short.

Rename this datum plane [BJS].

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19. Sketch a datum curve on datum plane PCR2 that controls the motion of the second piston. Use PCR2 as the sketching plane and DTM2 as the top reference. Select the four sketching

references shown in Figure 2–17. Sketch the two lines segments and the circle.

Figure 2–17

Select these four sketching references:

1. Point PNT1 2. Top half of circle 3. Bottom half of circle 4. DTM3

Sketch these entities:

1. Circle 2. Line 3. Line

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The completed feature appears as shown in Figure 2–18.

Figure 2–18

20. Create two datum points through the vertices of the datum curve shown in Figure 2–19.

Figure 2–19

Select these two vertices to create the datum points.

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21. Create two datum axes. Make them normal to datum plane PCR2 and through the datum points just created. Rename the axes using the names shown in Figure 2–20.

Figure 2–20

22. Create an axis at the intersection of datum planes DTM2 and DTM3. Rename the axis to [CRANK], as shown in Figure 2–21.

Figure 2–21

23. The skeleton model is now complete. Save the part and close the window.

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