figuring out what to say:
- once we settled on the four bar linkage design, we began construction of a simple prototype
- The rigid body holding the shovel was made of two linkages with a 3D printed shovel designed to be attached to the end
- So although the mechanism was functionally a 4-bar linkage, we made 6 linkages for the initial prototype
- For each prototype, we modeled the whole assembly as much as possible in CAD
- The linkages (including the ground linkage that held it all together) were laser cut out of acrylic and the bearings were then inserted into them
- For all of the bearings, we tried our best to have them press-fit into the linkages. However, due to the finnicky and sometimes inconsistent tolerances of the laser cutter as a result of factors such as the software trace feature and the laser diameter, the fit wasn't always perfect.
- Even with the same hole diameter for every cut, some of the bearing holes came out with a perfect press fit while others were too loose. Whenever the holes were slightly too loose, we would add a small dot of hot glue to the hole before inserting the bearing. This would force it to stay in place.
- In addition to the linkages, we laser cut a few circular spacers to add to the linkages' stack where they were necessary to prevent the linkages from crossing or colliding while moving
- We encountered an emergency complication for our first prototype, when we discovered the night before it was due that the steel shaft we were planning on using for the joints was made of hardened steel and would be impossible to cut on any of the equipment we had access too.
- With no other option, we resorted to using hot glue sticks for the first prototype's shafts.
- Because we had yet to finalize what the support structure would look like, we attached the initial prototype to a cardboard box full of dirt using dowels and hot glue.
- Overall, the first prototype was of pretty low construction quality due to the limited time it was constructed in before the deadline and the issue we encountered with the shaft last minute.
- However, it allowed us to test the digging motion and acted as a proof of concept for the main linkage design