Video: How a radial engine works—an amazing cutaway in motion

Jacobs radialBecause a picture is worth a thousand words, here’s a video that shows—with perfect clarity—the basic operation of a radial engine. It’s fun and fascinating, check it out. 



Our recent story featuring a homebuilt radial engine constructed from Volkswagen components sparked some great discussions on various social media channels around the web. What are the ins and outs of radial engine design? How do radials differ from standard four-stroke engines, and how are they similar? What’s going on in there, anyway?

So we’re following up with a video that shows, simply and clearly, the basic mechanics of a radial engine—in this case a Jacobs R-755, a conventional single-row, seven-cylinder unit. The cutaway will make several aspects of radial operation beautifully evident, for example cylinder number and firing order. A true four-stroke radial has an odd number of cylinders, and it will fire every other cylinder in order of crankshaft rotation, odd numbers first, even numbers second. Watch for the electric lamps in the cutaway model that provide simulated firing events.

The cutaway’s motion at multiple speeds also provides viewers with a feel for the basic dynamics and balance of master-and-slave rod operation. As we demonstrated with our recent video on driveshaft angle and phasing, we’re big fans of simple, clear technical presentations without needless complication and technobabble, and your response tells us that you are, too. Please enjoy the video.


3 thoughts on “Video: How a radial engine works—an amazing cutaway in motion

  1. Thanks MCG. I always knew how basic operation of how the engine worked, but never understood how the connecting rods attached to the crank. It’s kind of like watching a hula dancer. The thing that always freaked me out, was high in the sky, in a dogfight, all that is going on while the pilot is trying to outguess his opponent’s next move, with their lives depending on that engine to function. Really pretty simple.

  2. You guys are sharp. There’s more about radials we hope to cover down the road. For example, each cylinder is a slightly different stroke. Also, since all the cylinders are on the same crank throw, there is no horizontal couple. All the imbalance is in one vertical plane per row.

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