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 pin 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
Reduce the maximum torque needed to move the mechanism past the high-torque zone
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.

The effect of adding bearings was twofold. To fit the bearings, I needed to widen the links and increase the distance between pin 2 and the fixed pin to avoid a collision. This had the effect of lowering the maximum torque needed from the motor. 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 vertically and support the off-center weight of the motor.

Below is a video of the motorized mechanism in action.

Browser not supported