This was the third attempt at a design for the PiWars 2022 Hungry Cattle Game. The top drum has three compartments, each of which hold 20% more rice than is required to half fill a trough. The drum rotates to align a compartment with the down-pipes, enabling the rice to flow.
Since each delivery is 20% too much rice, it is easy to be sure that enough rice has been delivered (so long as most of it arrives in the trough).
The design uses two down pipes to direct the flow of rice to the trough. This is so that PJD’s radiator grille mounted camera can still get a clear view of the trough (although the last bit of the drive is blinded by the bottom chutes).
In operation PJD deliberately pushes into the troughs so that two front mounted prongs can align the trough with the robot before the delivery takes place; this means that diagonal approaches to the troughs still work. As delivery takes place the robot turns the hopper back and forth through about 10o to make sure the rice doesn’t stop flowing.
Here is the video we submitted for the competition:
During the design process I wanted to measure the volume of rice held in each hopper. But I couldn’t see how to get Fusion 360 to tell me the volume of a void. Two minutes on the internet provided the answer; create a solid then use the hopper as a cutting tool to shape the new solid to the shape of the void (and hence the rice it could contain). Fusion will then tell you the volume of this new body. I could then extrude the top of the design until the volume was exactly 300,000mm3 (this being 20% more than the volume required to half fill a trough). The picture below shows the shape of the rice held within each of the three hoppers.
After trying the game a few times, an additional funnel shape was printed for the top of the drum. This made it easier to pour in the rice between rounds.