Soccer Shootout- Jonathan and Kyle’s Midterm Project | ENGI 210: Prototyping and Fabrication

The basis of our midterm project originates around a soccer penalty shootout. We wanted to create a mechanical model in which a soccer ball and a goalie would travel and meet at the right side of a goal. The mechanical movement is based from movement 92: https://507movements.com/mm_092.html.

The first step of the project was to get the brainstorming done for gate 1. We visualized what kind of movements from 92 would be necessary and what connecting gears would be necessary to sync up the motions of the goalie and soccer ball so that the soccer ball would travel double the distance of the goalie yet remain in phase. With movement 92, the distance in which the goalie/ball (the green block) moves is dependent on the diameter of the gear to which it is attached. At this point, we also thought that since the ball was troubling double the distance, it needed to travel double the distance in order to sync up with the goalie. This was incorrect- I will come to this later. After doing some simple trigonometry calculations, we had our basic design:

The next step was to develop the gears and mechanical parts from cardboard as a low fidelity prototype. We utilized gear generator, and after a small learning curve, we were able to figure out what gears we wanted. We also generated some small pieces, such as spacers and arms that would be necessary for our project. We also printed out some open top boxes/tracks that would guide the motion of the goalie/soccer ball using the same website as the laser cutting box project. Overall this generated a very poor model of the final mechanical movements. The strength of cardboard severely limited the realisticness of the final model but was enough to prove that our idea would work. For example, we had to hold down a lot of the pieces by hand which made it difficult to operate the model.

After the cardboard prototyping we moved to wood to begin the final model. Here, we became more diligent in measuring the tolerances of the wood and getting the dowels, bearings, and spacers to have a very tight fit so we could have a good model without having to glue everything down. We did some tolerance tests for both the bearing and dowel diameters. This later became a slight issue; laser availability caused us to cut on both machines, so the epilog pro generated some cuts with tighter tolerances. This was solved however, with the use of files to sand the holes a bit bigger.

After using the bandsaw to get a cleaner cut of the dowels and printing the gears and tracks, we realized there was a mistake in gear sizes during assembly. The gear on which the soccer ball rested was half the diameter of the goalie’s gear. This meant that the soccer ball would travel double the angular speed as the goalie, when we wanted it to travel double the tangential speed. This doubling of the tangential speed was accomplished by the larger circle (double the diameter of the goalie’s gear) to which the ball was attached, so there was no need to half the size of the ball’s gear. Thus, the goalie and ball’s gear should be the same size in order for them to sync up. We reprinted this gear and move on.

We also then developed the base and top plates to hold everything down. This involved cutting holes for the bearings and dowels, and also openings for the goalie and ball to protude. We ended up deciding to glue the dowels inside of the bearings using epoxy so they would get a smooth rotation and tight fit. The outside of the bearings would then be epoxied into their press fit holes. Doing a full assembly, we got a very smooth, strong mechanical model. We had to be careful that the tracks were not offset even a little bit to the side because that would cause friction in the model. Looking back, we could have just cut the tracks a bit bigger.

We then worked on the metal piece, which was the handle/crank. I wanted to make an ellipse shape that would have two holes in it, so I made the illustrator file. Upon importing the file into torchmate, I realized that those holes would be too small for the plasma cutter to cut, so I had to back up and just cut the outer perimeter of the ellipse. That was pretty straightforward. I then cut the holes using the drill press to get a clean hole. For post processing, I used the angle grinder, sandblaster, sandpaper, and then green spray paint. The difficulty with this was that I accidentally left some deep scratches on the surface with the angle grinder which were a bit difficult to remove.

After TA approval, the next step was to start post-processing. We found a color of stain we liked and disassembled all the parts. We took the pieces outside and stained them and allowed them 24 hr to dry.

After staining, we started gluing the gears and dowels into place with spacers to reduce friction. The issue was that the wood glue would directly impact the ball bearings so the spacers could not be as tight to the bearings as we wanted.

Moving on to vinyling the field, many designs of the field were too big to fit on transfer paper and so parts of the field were cut and stuck on individually. The original plan was to leave gaps between the green vinyl to spray paint white like an actual field. We taped up the green vinyl to create the straight line of paint and as a means of prevention.

However, the spray paint seeped through the tape and stuck onto the vinyl. At this point, both the wooden areas and the vinyl had splatters of paint so some parts of the vinyl needed to be redone. Instead of painting white lines, we opted to also vinyl the white lines to cover the disaster paint job.

We also spray painted the ball to create a white base for the soccer ball and vinyl cut the hexagons to stick onto the ball. We realize that vinyl is not the best for 3D objects. We also vinyl cut a design for the goalie as a contrast to the ball and field.