The goal of this lab is to use SolidWorks to put together a mechanism. The lab is in two parts. In the first part you will work individually to put together a model for which I designed all of the parts. For the second part, you will work as a team and choose one of your own to design and build (within SolidWorks).
In this part of the lab you will put together a model of a Jesus Lizard (a lizard that can run across the surface of the water). The model closely follows the design at http://www.societyofrobots.com/robot_jesus_lizard.shtml.
The leg model we will use is a four bar linkage. Four bar linkages are often used because they can change simple rotary motion (e.g., supplied by a simple) to rather complex trajectories while the linkage remaining rigid. A three bar linkage cannot change shape; a five bar linkage is not rigid. Two examples follow.
Example 1: The linkage below (originally from http://www.mines.edu/fs_home/dgolson/mce302-1.html in September 2008, but the link is dead now) has four bars. One bar is fixed (between A0 and B0 - labeled link 1), one that rotates (link 2 - which rotates about A0), and two that move in other paths. Note that link 3 is triangular (triangle ABC). Point C moves in a somewhat elongated closed path, while point B moves back and forth.
Example 2: This example shows that a rather complex (in this case a distorted "figure 8") path can be derived from a simple four bar linkage.
The four bar linkage we will use is shown below (from http://www.societyofrobots.com/robot_jesus_lizard.shtml). The image shows the linkage in two positions (one black and the other cyan) and shows the path of the foot in red. Note that the path is meant to mimic that of the lizard, but the rest of the mechanism is not based on the lizards anatomy (e.g., lizards don't have limbs that rotate 360 degrees).
To develop the SolidWorks model download the following parts (shown on model below) and save them to your desktop or other convenient location:
Work individually to put together the SolidWorks model as described below for 30 minutes, and get as far as you can. After that, you will work in groups. You may start the group work as soon as everybody on your team finishes the individual work. If you finish early, feel free to explore other SolidWorks functions, or check your email..., but please don't start the group work until everybody is finished with the individual part.
Start SolidWorks and go to "". On the left of the screen you will get an "Insert Component" area. Go to "Browse..." and choose the Lizard Body part. Change the view to "Back" so the lizard is facing to the left (this isn't necessary, but makes it is consistent with the drawing above).
Now go to "", and choose the lowerLink part.
Now select one of the holes in the link and the lower left hole on the body (using the CTRL key so you can select the second element) and either select "" or choose the paper clip icon on the toolbar.
If your mate has the body parts overlapping:
you'll have to reverse the mate alignment.
If your mate turns out to just give you a "concentric" mate (i.e., the holes line up, but the surface of the bar is not against the surface of the body), you may also need to add a "coincident" mate between the two surfaces. Hit the green check mark to finalize the mate.
You should now be able to "grab" the link (by holding down the left mouse button) and rotate it about the mated holes
Repeat with the upper link and the hole in the upper left of the lizard body.
Last, add the leg above the other two links, with the long end pointing down.
You should now be able to move the leg around.
At this point you may move on to part 2 (below) for the teamwork, or continue on to animate the lizard (as time permits). To animate, click on "New Motion Study" in the top menu. Then choose an electric motor from the toolbar at the top of the Motion Study window and affix it to the lower leg. Hit the "Play" button to see the leg move.a motor from the toolbar at the top of the Motion Study window and affix it to the lower leg. Hit the "Play" button to see the leg move.
If you change the animation, you will have to recalculate the motion (the leftmost button does this).
You can do any of the following (refer to the SolidWorks documentation for help on these features).
You can also experiment with rotating the part (my final animation - running and (for last few seconds) spinning ).
You may start the group work as soon as everybody on your team finishes the individual work. If you finish early, feel free to explore other SolidWorks functions, check your email..., but please don't start the group work until everybody is finished with the individual part.
Work as a group to design and implement a mechanism of your choosing. You may start as soon as everybody on your team is done with the Jesus Lizard mechanism, but please don't rush anybody
Please don't continue beyond this point until everybody on your team is done with the first part. I want you all to look at mechanisms, and choose one, together.
When working as a team, try to make sure everybody feels comfortable contributing. Take turns at the computer (don't always have the best person at the computer running it). Some ideas for mechanisms:
There is, effectively, no write-up this week. You should select one person from your group and post everything to moodle from his/her account. You just need to complete your design and...