How I created it
I started by creating the cylinders and I made 4 of them. Then I started making the pistons the right size and I made two holes in the opposite side of the pistons to put a paperclip through which then it would be able to hold the connecting rod.
The crankshaft was more difficult to design. I used a special shape in tinkercad that allowed me to move it around a certain way, so I used that shape to design the crankshaft. I copy and pasted that shape two more times so then I would have a crankshaft. The two shapes on the end I edited them so they would stop half way up. For the connecting rods I made a thin long cylinder with two different sized tubes on the ends. The smaller tube would be the one with the paperclip going through it, and on the other side the bigger tube would be connected to the crankshaft.
The last thing I made was a box that would go around everything because I needed something that would hold everything up. I put a hole in either side of the box that the crankshaft would be held up by. On either side of the crankshaft I put cylinders connected to it so then you put those through the holes in the box.
Putting it together
To put it together you take 4 paper clips then take the pistons and connecting rods, and take the connecting rod line it up in the piston so the paper clip goes through all the holes and holds the connecting rod up. Then do this three more times. After that take the crankshaft and the other end of the connecting rod and loop it through the crankshaft 4 times for the different pistons. Then you can put the crankshaft through the box and you should be able to spin the crankshaft and you will see the pistons go up and down.
Some problems I ran into
I ran into quite a bit of problems and doubted my design a little bit along the way. I had to sand basically everything so they would fit inside each other. I had to reprint the connecting rods because the first time the little hole didn’t print and the second time it didn’t print again so I then just drilled a tiny hole in the rod so the paperclip would then be able to go through everything. Just today one of the tiny holes that I drilled broke because I drilled it too close to the edge. I was able to fix it with tape and It still works just as well! Everything is able to be taken apart again and put back together, except for the super glued stuff.
Thanks for reading!