6-Cylinder Radial Engine

Boy is this fun! Today's model is a 6-cylinder radial engine:

It's made with two layers of 1.44mm (rather thin) and one layer of 5.28mm (about 1/4" thick) acrylic. The pistons, link arms, and star-plate in the center are all cut in-place in operational arrangement (as in the CAD file above). In other words, you can simply slide it out of the laser cutter (being careful not to let any of the parts drop) and it works. Here is the main layer in raw form, with the protective film still on:

Getting the top and bottom plates screwed on is a bit tricky, but here it is all assembled:

The disk in the center is basically the crank shaft bearing. It's the rotation of the big disk within the cutout circle that keeps the crank shaft rotating about its center. The offset hole then caries the star plate around its orbit, operating the six pistons in order. (A certain wag who shall remain nameless complained that there were no operating valves, so I declared it to be a 2-stroke engine whose valves are just holes (not shown) in the cylinder walls.)

What blows me away is how smoothly this thing operates. I did not trim, sand, polish, or in any way manipulate any of the operating parts: everything is exactly how the laser cutter left it. All I did was add the nuts and bolts to hold it all together. Watch this!

Who needs a fidget spinner when you have a 6-cylinder spinner?

Although I had always been planning to make some engine models, I admit that the details of this one were inspired by this really cool cardboard version. Which reminds me that I need to add some engraved details around the cylinders.

Meanwhile, my cotton field is doing nicely. I weeded it this afternoon and it's looking good. A transparent cotton gin is next in the list of projects for the laser cutter.