I started the design process by drawing the linkages in Solidworks to better visualize how the mechanism would work and make sure the Grashof condition was met and link 1 could rotate 360 degrees.
I then laser cut the linkages from clear and black acrylic to reduce friction. I created pink joints using M4 bolts and lock nuts to securely fasten the links together while still allowing them to rotate freely. I attached the links to a clear acrylic back plate with a slot that the slider could freely slide in. Through rotating the assembly with my hands, I noticed that the minimum distance between pins 2 and 3 was quite small, and it created a region of relatively high torque required to move the mechanism.
Video: Moving iteration 1 of the mechanism with my hands
Moving on to the next iteration of the mechanism, I wanted to accomplish a few goals:
- Add bearings into joints 2 and 4 to reduce friction
- Add another layer of the base plate to the other side of the linkages to strengthen the fixed pin joint and slider to reduce friction
- Add a place for a motor to automate the mechanism
- Make the mechanism stand on its own
To do this, I made a new CAD assembly of the new and improved version, re-did the analysis, and laser cut the new parts.
I added bearings in the linkages as shown below:
Here are some close-ups of the pin joints with laser cut spacers:
I also laser cut a D-shaped hole into link 1 to attach to the D shaft of the motor, and I laser cut feet for the mechanism to make it stand and support the off-center weight of the motor.
Below is a video of the motorized mechanism in action.