The radial engine is unlike the typical automotive engines we normally feature here at EngineLabs; radial engines are typically used in aircraft to drive a propeller.

Rather than a crankshaft with offset throws, the radial engine uses a master-and-slave connecting rod assembly. The crankshaft is directly attached to only one connecting rod, and the others are pinned to the master rod with a plate and pin assembly that allows them to articulate properly and rotate around the crankshaft.

This hypnotizing video has no audio, and quite frankly, it’s unnecessary as the cycle of the engine’s operation provides all of the entertainment. We can see in the cutaway how each component of the engine interacts, especially in relation to the propeller on the back side of th.

As the engine rotates, we can observe the operation of the valvetrain in relation to piston movement and even how the spark lights off the mixture and when it does so.

Camshaft operation also works off the crankshaft – as the engine rotates, a ring is driven through gears from the crankshaft to actuate the pushrods, which open the valve much like a typical automotive engine through the use of a rocker arm and spring assembly.

The engine in this example is a single-row, seven cylinder Jacobs R-755 powerplant. It’s a four-stroke radial, and while you might think that a four-stroke requires an even number of cylinders, that’s the opposite of how a radial engine operates. Every other cylinder is fired in order of crankshaft rotation, with odd numbered cylinders first, then even numbered cylinders.

The video speeds up toward the end, showing the engine in dynamic operation and giving a true internal look at the inner workings of a radial engine. Neat stuff!