If That Is A Piston, What Is This?

Why do motorcycle manufacturers make pistons as light as possible, getting rid of everything that isn’t necessary? The up-and-down motion of a piston produces a shaking force, and you can’t balance all the shaking force of an engine by simply adding counterweights to the crankshaft.
Why have pistons atrophied to almost nothing? In this example from a Honda CRF450R motocrosser, all we have is a thin disc that is enough to locate the piston rings, two bosses for the wrist pin that connects the piston to the connecting rod, and little skirts.
The up-and-down motion of the piston produces a shaking force. You cannot balance all the shaking force of an engine by adding counterweights to the crankshaft. You can reduce the vibration, but you can’t make it go away.
Also, in a very high-rpm engine, moving up and down as it does, the piston produces very large bearing loads. Those bearing loads translate into friction, which is subtracted from the horsepower that your engine can send to the rear wheel.
Manufacturers therefore make pistons as light as possible, getting rid of everything that isn’t necessary. This particular example is large, but the center of the dome is quite thin. What happens to the heat of combustion that is collected by this surface?
With traditional pistons, that heat is conducted out to the cylinder wall. But this piston dome is large and that is a great distance for heat to flow. Normally, to conduct all that heat away from the center of the dome, the dome would be thick-a broad avenue for heat.
Instead, a small oil jet is placed in the crankcase, which sprays oil underneath the piston, hits one side, splashes across under the dome, is deflected down the other skirt, and falls back into the crankcase. That oil cools the piston dome, allowing it to be made thinner.
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[@blipco5]

Fantastic! KC could describe the function of a door stop and make it interesting.

[@MelihCANBOLAT]

clever these humans

[@maximusmax4557]

I much prefer a miniskirt to a regular length skirt! In more ways than one! LOL

[@davesnothere512]

Love me some mini skirts.

[@gerry343]

Yippee! No creepy 'music' to spoil your video.

[@maximusmax4557]

Dude is old school, and realizes his target audience probably doesn't need constant visual or aural stimuli blasting into their head-holes 24/7!

[@kissmyaskew9844]

I'd love to hear his thoughts on Porches new 3D printed pistons. Also as someone here already mentioned, Hondas oval pistons.

[@maximusmax4557]

Why would a porch need a piston? And why do you need Kevin's opinion on Honda's oval piston design? Do you not know the reasons for it? There's plenty of info to be found on the Google...

[@naveen..873]

Sir, please make a video on thermal efficiency

[@upsidedowndog1256]

F1 tech on the motocross track!

[@jamesanderson2176]

Seems like I remember a TDC article discussing how tiny weight savings in the piston result in pounds off of an engine. I don't suppose you have a video on desmodromic valves in here?

[@cpuuk]

Any chance you can do a chat about the Honda NR750 oval piston?

[@billshiff2060]

It was no good. It was only a work around to get v8 performace from a v4 because the rules only allowed 4 cyl.

[@andrewsmactips]

Now THAT is technology.

[@mustafaYkhan]

Quite clever indeed

[@JackdeDuCoeur]

always good, always

[@angelocardoc]

Conventional piston...Yes...Old school. Search 'LiquidPiston X Engine' and see 3 power strokes per 1 RPM

[@samuelcaeiro7647]

god damned white balance!!