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  • - We've talked about engines before,

  • and I don't know if I'll ever get tired of it.

  • The air gets compressed by the piston,

  • and the spark...

  • What?

  • No, stop it!

  • There's no piston here!

  • What if I told you we could skip all of that crap?

  • Not worry about turning downward force into rotational force

  • and cut the size of the gall dang engine in half?

  • That's the Wankel rotary engine!

  • In 1951, Felix Wankel got this idea in his head

  • that if you put a triangular rotor in a well-designed

  • circely, oval-ish shape, you could make an engine

  • that took care of intake, compression, combustion,

  • and exhaust, just like the traditional piston-drive

  • Otto Cylce engine.

  • And because it's a spinning motion, you wouldn't need

  • to worry about crankshafts and valves and timing belts

  • and lifters and all that crap that other people

  • are goofin' around with.

  • He had some trouble getting it right, though.

  • So it was in 1961 that Mazda, intrigued by this idea,

  • helped him out, and here's how it works.

  • A curved triangle sits in the engine.

  • It's what'll drive the driveshaft, which is also weird.

  • Instead of a piston, this magic triangle is called a rotor,

  • because it spins.

  • The rotor sits inside of a housing and rotates

  • around a fixed gear attached to the housing.

  • This gear makes sure that the rotor follows the right path,

  • so it's not just floating around in there.

  • The rotor then spins an eccentric output shaft,

  • and this is what'll give the car moving.

  • You can call it a driveshaft if you want,

  • I'll know what you're talking about.

  • But just the names of the parts should let you know

  • that the Wankel rotary engine plays by its own rules.

  • Now that we know the parts, let's see how they fit together

  • and make the boom.

  • We'll start with the intake.

  • As the triangle-shaped rotor draws away from the wall

  • of the housing, it's creating a vacuum.

  • As it passes the intake hole, it continues to pull away

  • from the wall, drawing the air-fuel mixture

  • into the chamber it's creating, just like a piston

  • would draw air in on its intake stroke.

  • When the peak of the rotor passes the intake port,

  • well, now that chamber's sealed.

  • The rotation of the triangle, still sealed against

  • the housing, begins to compress the air-fuel mixture

  • as it continues its rotation.

  • When the air is as compressed as it can be and the rotor

  • has just a bit more mass on the other side of the chamber,

  • a spark triggers the combustion.

  • The combustion chamber is long.

  • If there's only one plug, the flame would spread too slowly

  • to be effective at producing power.

  • Most rotary engines have two sparkplugs.

  • When the sparkplugs ignite the air-fuel mixture, kapow!

  • It forces the rotor to move in a direction

  • that allows the combustion reaction to expand,

  • continuing the rotor's journey around the housing.

  • The combustion gasses continue to expand, moving the rotors

  • and creating power, until the peak of the rotor

  • passes the exhaust port.

  • Just like the rotor compressed the air-fuel mixture

  • against the wall with the sparkplugs, on this side

  • of the housing, the rotor pushes the exhaust gasses

  • out of the exhaust port.

  • And if you look at the other point of the triangle,

  • the rotor is beginning to draw air into the intake chamber

  • just as it's finishing with the exhaust down here!

  • So the cycle continues, over and over and over

  • and over and over and over, and it continues to go

  • over and over and over.

  • But unlike the jerky up-and-down motion of the pistons,

  • the rotor moves, just like my favorite band,

  • in one direction.

  • You don't know you're beautiful

  • There's so much rubbing going on between the rotor

  • and the housing that that gave Wankel a lot of problems

  • as he was designing.

  • Engineers realized that a hole to let in the engine oil

  • would reduce wear on the rotor and housing.

  • Also, to make sure that no chamber of the combustion cycle

  • loses pressure, apex seals cap the point of the triangle.

  • These tweaks are what took Wankel's early underwhelming

  • experiments from curiosity to practicality.

  • And look at this triangle!

  • With three sides, as soon as one side begins,

  • let's say, combustion, another side is completing

  • exhaust while the third side is drawing in air and gas!

  • So, unlike a traditional piston-driven engine,

  • which would need three cylinders to do that,

  • like the rare but very real in-line three, you only need

  • one active component, the rotor, to have three stages

  • of engine combustion occurring simultaniously.

  • The way Mazda did it on their engines,

  • like what powered the RX7 and RX8,

  • was to put two rotors that complimented each-other,

  • so when one rotor was entering combustion,

  • the other was about to enter combustion.

  • You can see how evenly a Wankel rotary engine

  • can deliver power versus the herky-jerky up and down

  • of a piston-driven engine.

  • This evenly-driven rotational force spinning the rotors

  • drives the output shaft.

  • The output shaft has round lobes mounted eccentrically,

  • meaning they're offset from the center line of the shaft.

  • Each rotor fits over one of these lobes.

  • The lobes act sort of like the crankshaft

  • in a piston engine.

  • As the rotor follows its path around the housing,

  • it pushes on the lobes.

  • Since the lobes are mounted eccentric to the output shaft,

  • the force that the rotor applies to the lobes

  • creates torque in the shaft and makes it spin.

  • This makes the eccentric shaft move three turns

  • for each turn of the rotor, and that's why these engines

  • can create such high rev.

  • (engine revving)

  • And if you check out the horsepower versus torque video,

  • you'll know horsepower is how quickly

  • force can be produced.

  • A high-revving engine doesn't need as much torque

  • to generate more horsepower,

  • because it's delivering it so quickly.

  • And, like Mazda did with the RX7, they can be turboed,

  • just like any other engine.

  • And again, because they're revving so high, a turboed Wankel

  • doesn't have to worry half as much about lag!

  • Some lag!

  • So, what are some other benefits of a rotary engine?

  • First, there's fewer moving parts.

  • No lifters, no push rods, no camshafts.

  • All those little things that can go wrong in

  • a traditional engine simply aren't there in a Wankel,

  • so they can't break.

  • In a two-rotor Wankel, you got two rotors and one e-shaft

  • to worry about, that's it.

  • And that means these engines can rev higher

  • and not bust any of those intricate parts.

  • And also?

  • You don't need four, five, six cylinders,

  • you've got an engine delivering consistent power,

  • making awesome noises!

  • (engine revving)

  • And taking up half the room of other engines!

  • Oh!

  • And sometimes, when it gets moving really quick,

  • you get this!

  • (backfiring)

  • That is pretty cool!

  • But that's also a drawback.

  • Wankels use a lot of gas because they have

  • a low compression ratio.

  • When they get moving like that, they make those

  • sweet-ass flames 'cause they're shooting out exhaust gasses

  • with unburnt hydrocarbons.

  • That's not good for fuel economy,

  • and it's not good for the air!

  • Also, remember how they're lubed with oil

  • throughout the housing?

  • That oil burns when it's hot.

  • That means more burnt less clean hydrocarbons,

  • which is tough for emissions.

  • You remember how they sealed up the different chambers

  • created by the rotor.

  • Remember, from before?

  • Uh, yeah.

  • You can blow an apex seal, and if that happens...

  • (screaming)

  • Those chambers bleed into one another

  • and you lose most of the benefits that made you fall in love

  • with your screaming rotary engine in the first place.

  • Between being different and being good,

  • Wankel rotaries are pretty rad.

  • Wankel rotary engines!

  • If you like the way we show how things work

  • on Science Garage, then you really need to check out

  • Brilliant.org.

  • Brilliant is math and science enrichment learning.

  • It's engaging, and instead of just getting talked at

  • about how thing worked, Brilliant is set up

  • to let you really get in there and apply

  • what you're learning.

  • The sequences lead you to thought-provoking,

  • challenging problems, and that helps you understand

  • concepts at a deeper level.

  • Actively solving problems becomes an addictive,

  • interactive experience, and I gotta tell you,

  • it's pretty cool.

  • How do you think the brain trust we just talked about

  • created the Wankel rotary engine?

  • They had a deep understanding of physics

  • and practical application and problem-solving,

  • just like the courses at Brilliant.org.

  • A great place to start is with Physics of the Everyday.

  • This course gets into how things work, things you use

  • every day, just like we do here on Science Garage!

  • To learn more about Brilliant,

  • go to Brilliant.org/sciencegarage and sign up for free!

  • Also, the first 200 people to go to the link

  • will get 20% off their annual premium subscription!

  • I'll see you there!

  • Brilliant!

  • And follow me on Instagram, @bidsbarto,

  • and follow Donut, @donutmedia.

  • We got shirts like this, and we got new designs comin' soon.

  • Guys, we do this every Wednesday!

  • Make sure you subscribe, hit the yellow button

  • so you get notifications!

  • Like the RX7, you can learn about turbochargers here,

  • and you can learn about the RX7 in this episode

  • of Up to Speed!

  • Don't tell my wife these engines can be a hassle,

  • 'cause I'm trying to get one.

- We've talked about engines before,

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B2 US rotor engine rotary combustion piston shaft

Rotary Engine | How It Works

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    OolongCha posted on 2020/08/25
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