Amanda, a private pilot in Minnesota, writes: I was reading about the early aviation engines, and with the rotary engine, the entire engine spun. How on earth did that work with getting spark to the cylinders? Obviously cables were out…
Fabulous question!
They used a version of old-fashioned distributor-cap “points.” The magneto (usually just one on these early engines) was attached to the airplane, and had a little contact point that stuck out a bit. Each cylinder had a sister contact. As the cylinders spun past, each in turn made contact with the mag’s point, transferring a spark from the mag to the spark plug of the cylinder.
Most of these engines also had only a single plug in each cylinder — redundancy was for the future!
Having the whole engine spin on a fixed crankshaft also makes other technology we are used to impractical. For instance, no carburetor. Fuel and air – along with lubricating oil – got sucked up into each cylinder through the crankshaft, which was hollow, thanks to the vacuum effect of the spinning engine.
Oh, and no carb, no throttle. You landed by interrupting the flow of power between the mag and the cylinder to “cut” the engine using what was termed a “blip” switch to toggle power on and off as needed for the approach.
And one final fun fact: With the cylinders spinning, there’s no way to have exhaust pipes. The exhaust is just belched out of each cylinder and “spun” into the slipstream. And into the pilot’s face.
And these engines used castor oil mixed with gasoline for lubrication. Since the engine spewed the castor oil out in the exhaust straight back to the pilot, the pilot breathed in a swallowed plenty of it during flight. Castor oil is a very effective laxative. It gives new meaning to the old adage “I’d rather be on the ground wishing I was in the air than in the air wishing I was on the ground”.