# Articulation

## Compound Gears

1. Create a new folder called Compound.
2. Download SpurGear-6-20.SLDPRT from the web and save it in Compound.
3. Open SpurGear-6-20 in SolidWorks.
4. Do "Save As Copy and Open" and save the part as SpurGear-12-20.
5. Click on Manage Equations and set the pitch diameter to 12.
6. Edit the hole sketch and set all the hole distances to 0.45 inches.
7. Save the part.
8. Do "Save As Copy and Open" and save the part as SpurGear-12-40.
9. For SpurGear-12-40, click on Manage Equations and set the number of teeth to 40.

10. Save the part.

11. Make a BackingPlate part 6 inches by 6 inches.
12. Add three 1/8 inch diameter holes in an L-shape, spacing 2.5 inches.
13. Save the part and create an assembly from it.

14. Insert a SpurGear-12-20 and mate it to the left hole.
15. Insert a SpurGear-12-40 and mate it to the right hole.
16. Add a 20:40 gear mate.

17. Create a new part called GearSpacer: a disk 1.25 inches in diameter.
18. Add 1/8 inch holes, one at the center and one 0.45 inches above it.

19. Insert GearSpacer into the assembly and mate it to the top hole in the backplate.
20. Insert a new SpurGear-12-20 and mate it to the top of the SpurGear-12-40 using both holes, so that the two gears are rigidly attached.
21. Insert a new SpurGear-12-40 and mate it to the top of the Spacer using both holes.
22. Add a 40:20 gear mate betweeen the new SpurGear-12-40 and SpurGear-12-20 instances.

23. Verify that rotating the left gear results in a 4:1 reduction for the top gear.
24. Verify that rotating the top gear produces a 1:4 speedup in the bottom gear.

## Articulated Arms

1. Download LittleManVee and save it as LittleManArt.
2. Create a new part.
3. Sketch a bar 2 inches long and 1/2 inch wide. Add horizontal and vertical centerlines.
4. Put three 1/8 inch diameter holes at the center and 1/8 inch in from each edge.
5. Extrude to 1/8 inch depth and fillet the corners to 0.2 inch.
6. Color the part red.
7. Save as ArmSeg.

8. Delete the Arms in the assembly.
9. Change the link lengths to 6 inches.
10. Open the Torso and rescale the part so the shoulder distance is 2.75 inches.
11. Replace the arms with pairs of ArmSeg instances mated at the end circles.
12. Mate the links to the distal ends of the arms.
13. Verify that turning the gears moves the arms.

### First Motion Analysis

14. Switch to the motion analysis tab.
15. Change the type from Animation to Motion Analysis.
16. Add a rotary motor attached to the small gear and set it to 40 rpm.
17. Run a motion analysis study and observe the chaos.

### Pin

18. Create a new part called Pin.
19. Sketch a cylinder 1/4 inch in diameter and extrude to a depth of 1/4 inch.
20. On the back side of the cylinder sketch a cylinder with a diameter of 1/8 inch and extrude to a depth of 1/4 inch.
21. Color the pin yellow.

22. Place pins on the backplate to limit the travel of the links.
23. Mate the links against the backplate and set them to Fixed.
24. Return to the motion study tab.
25. Add Solid Body Contacts between each link and its pin.
26. Click calculate and observe the results.

### Slotted Link

27. Create a new part called SlottedLink.
28. Sketch a horizontal rectangle 1.875 inches long and 1/4 inch high.
29. Add a horizontal centerline.
30. Sketch a slot 0.75 inches long on the centerline, with one focal point 1/8 inch in from the right edge of the rectangle.
31. Set the slot radius to 1/16 inch.
32. Add a 1/8 inch diameter hole at the other end of the rectangle, 1/8 inch in from the edge.
33. Extrude to a depth of 1/8 inch.
34. Fillet the corners with a 1/16 inch radius.

35. Switch back to the assembly.
36. Put a pin in the central hole of each upper arm segment.
37. Add a SlottedLink.
38. Mate the hole in the slotted link to the central hole in the distal arm segment.
39. Use a slot mate to mate the slitted link to the pin in the upper arm segment.
40. Do the same for the other arm.
41. Move the parts to check range of travel, and reposition the limit pins as necessary.

42. Return to the Motion Study tab.
43. Add Solid Body Contacts between each slotted link and pin.
44. Click Calculate and observe the results.

Dave Touretzky
Last modified: Wed Mar 29 16:44:49 EDT 2017