Desmodromic valve drive was often justified by claims that springs could not close valves reliably. There was once a time when Desmodromic valve technology was cutting edge and a necessary competitive advantage for Ducati in racing. Ducatisti around the world know that the red bikes have desmo valves. Not all of them can tell you what that means, exactly. The Greek words.

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Relevant discussion may be found on Talk: This would allow an engine to run at a higher rpm then a unit with a conventional spring poppet vslve. Several F1 engine constructors prototyped desmo systems of their own Ferrari and Cosworth, for example but did not pursue them.

In almost every poppet valve system, valves are opened via mechanical actuation.

Why things are the way they are: Desmodromic valves – RevZilla

Even with that said, most engines had their RPMs limited because continued operation above RPM would still cause spring breakage. The Mark 3 was the very first production Ducati to feature desmodromically actuated valves. A desmodromic valve is a reciprocating engine poppet valve that is positively closed by a cam and leverage system, rather than by a more conventional spring.

Inhowever, Fabio Taglioni, a Duc engineer, did develop a desmodromic valvetrain for a single. Among the many race victories of his early desmo twin, the legendary return of Mike Hailwood at the Isle of Man is perhaps the most memorable. It produce bhp and was installed in a speed-boat called “Irene I” which was named after his eldest daughter who had married Colonel Waite. Why do Harley-Davidsons have dry-sump engines?

This reduces engine efficiency and performance and potentially increases engine emissions. Today most automotive engines use overhead camsdriving a flat tappet to achieve the shortest, lightest weight, and most inelastic path from cam to valve, thereby avoiding elastic deemodromic such as pushrod and rocker arm.

Here you can desmoodromic explanations of almost everything about your car deskodromic how it works. With conventional cams, stress is highest at full lift, when turning at zero speed initiation of engine crankingand diminishes with increasing speed as inertial force of the valve counters spring pressure, while a desmodromic cam has essentially no load at zero speed in the absence of springsits load being entirely inertial, and therefore increasing with speed.


Varying valve duration is much more difficult to achieve using conventionally closed valves. Multistrada Pikes Peak. By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. Without Ducati, desmodromic valves would be a footnote in history, rather than active part numbers available desmldromic order.

Understanding the Operation of a Desmodromic Valve

The specific purpose of the desmodromic system is to force the valves to comply with the timing diagram as consistently as possible. Another possible disadvantage is that it would be very difficult to incorporate hydraulic valve lash adjusters in a desmodromic system, so the dezmodromic must be periodically adjusted, but this is true of typical performance oriented motorcycles as valve lash is typically set using a shim under a cam follower.

Today, most cams have mirror image symmetric profiles with identical positive and negative acceleration while opening and closing valves. Ducati’s use a unique method to open and close their valves. Panigale V4 and it marks a new and important chapter in Desmoromic history.

The desmodromi mass of a traditional valve with spring includes one-half of the valve spring mass and all of the valve spring retainer mass. A desmodromic valve, while complex in name, is a reciprocating engine valve that is closed by a cam system rather than springs. Mercedes Benz didn’t drop the idea of the desmodromic valve actuation because it performed better in ways that made the additional complexities worthwhile.

Shop Helmets Shop All. A special advantage of pneumatic springs is that they are highly progressive. Desmodromic systems remove the valve spring and generally supply another rocker.

The characteristic and universally used mushroom or “poppet” valves used in every 4-stroke engine will open during their down-stroke and close during their up-stroke, until they make contact with their seats in the cylinder head.

From Wikipedia, the free encyclopedia.

Desmodromic valve system

A farewell to air-cooled engines Lemmy. When a high-acceleration cam begins dewmodromic lift a valve, wire coils pile up against the spring retainer then rebound from it as the valve reaches one-quarter lift.

In this way, any lost energy is negligible, the performance curves are more uniform and dependability is better. Since those days, lift, velocity, acceleration, and jerk curves desmodgomic cams have been modelled by computer [6] to reveal that cam dynamics are not what eesmodromic seemed.

Note that Ducati still uses that, too! This increases the seat pressure of the valve the static pressure that holds the valve closed.


The system consists of a mechanical lifter mechanism that uses a second rocker arm to push the valve closed. He began in the s by designing Ducati singles, and in designed the prototype V4 Ducati Apollo. Simplicity and service intervals don’t matter. Desmodromic systems have to deal with the extra inertia from two rocker arms per valve.

Curved lever tappets [10] of desmodromic cams cause higher contact stress than flat tappets for the same lift profile, thereby limiting rate of lift and closure.

Joe is an journalist, who write primarily about politics in and around motorsport, specifically on the FIA Formula 1 World Championship. After World War II, when future Ducati engineer Fabio Taglioni wrote his original engineering-school paper on desmodromic valve drive, there was good reason to seek such a system: OK thanks for that.

Many of the reasons why modern cars have rev limiters draw back to cam and spring valve systems.

Desmodromic valve drive

An alternative to pneumatic Valvetrain design approaches used by other manufacturers in MotoGP; that – if implemented correctly – can also calve both weight savings and also cylinder head port geometry benefits. The highest peak of technology and Ducati design to reach the maximum perfomances. Share 0 Join the Discussion. When steel refinement was improved in the s, manufacturers were able to remove most impurities from the spring metals and greatly increase their durability.

On December 11,the Grand Prix Commission announced that the MotoGP class would switch to the 1, cc motor limit starting in the season. Less obvious secondary effects is that valve springs typically weigh as much as the valves which they actuate, that mean the total mass which needs to desmodromc moved by the actuation mechanisms belt, bearings, shafts also need to be larger in order to avoid fatigue failures.

This allows cylinder gases and pressure to escape prematurely, which causes a major decrease in engine performance and can cause the valve to overheat, possibly causing warping or catastrophic valve avlve or both. The drawback is that the engine vapve to work harder to open the valve at all engine speeds.

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