18 Cylinder Radial Engine

Wright R-3350 Duplex Cyclone

Functioning 18 cylinder radial engine.

I tried to make a 7 cylinder radial engine but found out it was quite difficult (until I found a possibility with 3x5 lift arms, see my other project) so I started with a 6 cylinder engine. That was not too difficult after I succeeded in making the master rod needed.

Next, converting a row with 6 cylinders into a row with 9 cylinders showed possible but the cylinders are slightly unequally spaced (40.2°, 39.6°, 40.2° and so on instead of 40°) but that difference is way too small to notice. With an appropriate master rod and adding an additional row, I made a model representing an 18 cylinder radial engine, like i.e. the Wright R-3350 Duplex Cyclone engine. It runs very smoothly, as can be seen on the video of this engine swinging a four-bladed propeller on Album.

As mentioned, deleting one row or adding two rows makes it possible to make a 9 cylinder radial or even a model of the impressive 36 cylinder inline radial engine, the Lycoming XR-7755. There’s some screenshots and photos of these engines, next to the 18 cylinder engine.

I’m showing CAD models of the different engines that I made and added features on the smaller engines to simulate the rocker covers and push rods. They are not on the 36 cylinder engine since that one was liquid cooled. The design is mine and for the CAD models of that design, I used several bricks of which CAD files were made by DK. You can find examples of his beautiful work on GrabCAD.

Like the 28 cylinder engine of my other project, this is mostly a mechanical model but I hopeyou like this model anyway. In addition, https://en.wikipedia.org/wiki/Radial_engine offers lots of technical background information.

Evolution of the master rod is shown on one of the photos added, as well as the moving parts. Since the diameter of the stud on the rods is the same as the sphere on the designated piston rods, they are an ideal alternative, having a small diameter to avoid conflict with the cylinder heads.

I think this engine on a stand as on the photos above would make a nice item to display. Or one could use the engine to make a large model of an aircraft in which such 18 cylinder radial engine was used.

Enjoy!