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Springless Valvetrain?
Can these actually work?
http://www.youtube.com/watch?v=GXIdOTkJhEY |
"Desmodromic", first invented in the 1800's, used in engines in the Indy 500 in the very early 1900's. Modern application, Ducati motorcycle engine. This is yet another example of the desmodromic valve actuation. The valve action can be direct or indirect via a camshaft which both opens AND closes the valve. Mercedes Benz, 1955 300SLR, desmodromic valve actuator! There is nothing new under the sun... :D
http://upload.wikimedia.org/wikipedi..._desmo_8x6.jpg |
Unlike the "desmo" of ducati, the pushrod "springless valvetrain" makes no mention nor demonstrates how the pushrod (which is also now a "pullrod") actually works.
All the normal push only contact points, pushrod cup seats and rods have to pull as well now, as well as the very intricate camshaft lifter setup. And by the looks of the lifter, has no rotation so does it have a roller follower or a "foot" like a SOHC engine with rockers. I cannot see long term use of this setup. And/or high rpm failure. |
nothing new under the sun
the point of the "desmo" valve train is preventing valve float at super high RPM.
This setup was invented out of desperation about 99 years ago when steel valve springs were primitive. Ducati still runs this setup but only as an idiosyncracy. The ultra high RPM systems in use in Indy cars running over 20,000 RPM use air pressure as a valve spring although modern steel springs would work. They are using air pressure because at low RPMs less pressure is needed and by using air it is easy to modulate pressure in the system. Low RPM = less air presure,high RPM= high pressure. The reson for lower pressure at lower RPM is less friction on valve train components and less stress. |
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