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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If you want to know more or refuse the use of some or all cookies click here. In fact, in the first part of the decade, to lure Taglioni to the company, Ducati General Manager Giuseppe Montano grimly laid his cards on the table.
Ducati: Moto, MotoGP & Superbike
Share 0 Join the Discussion. As with a metal spring design, the cam operates a finger follower that presses against the end of the valve stem to open the valve. Sign up using Email and Password. Official Formula One information are available at www. Navigation Search Phone Cart. While the design can be noisy, it is typically overridden by road noise from tires and other engine components such as intake and exhoust noise. Desmodromic valve drive was often justified by claims that springs could not close valves reliably at high speed and that the forces caused by suitably strong springs exceeded what cams could withstand.
Service and Maintenance Services. Well, most of the problems conventional valve springs have been solved through improved metallurgy and design. You can learn a lot from this site. It must work against the momentum of the valve opening and closing, and that force still depends on the effective mass of the moving parts.
Servicing Duc valves isn’t appreciably harder than any other make, and they’ve gotten their adjustment intervals to a point where I feel they’re pretty reasonable relative to conventional poppet valves. Valve springs broke at random as an era of rising rpm opened. Naturally, there are packaging and usability constraints galore, but removing valve springs from the equation could make changing cam duration on demand possible.
This can cause rapid end-to-end bouncing of the spring coils, greatly increasing the number of fatigue cycles the wire must endure. This generates so much hash noise that the second derivative acceleration was uselessly inaccurate. While it can be more expensive to maintain than traditional spring actuated valve systems, there are many aftermarket precision machined components which can extend the maintenance interval to that of the almost magical spring actuated systems in comparable engines.
Breakage was solved largely by way of vacuum induction melting — a metal-refining process that helped remove the impurities that weakened early valve springs. It still requires springs to be implemented properly and reliably; defeating one of its most commonly considered benefits.
Retrieved from ” https: Ducatis still use desmodromic valve systems today, but the company has patented many proprietary improvements.
Anyway, in desmodromic valve sistem there is a small spring.
So the big question is why? Titanium valve supplier Del West is also a provider of pneumatic-spring technology. Normally, the valve is operated by a “cam” systemwhich controls valve opening down-strokewhile the valve “return”, i.
When desmodromic valves were first developed, springs were a much greater limitation to engine performance than they are in the modern manufacturing climate.
One cam and actuator to open the valve and the other set to close the valve.
However, a desmodromic system must deal with the inertia of the two rocker arms per valve, so this advantage depends greatly on the skill of the designer. 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: Varying valve duration is much more difficult to achieve using conventionally closed valves.
However, some high speed in terms of engine RPM motors now employ asymmetrical cam profiles in order to quickly open valves and set them back in their seats more gently to reduce wear. Thus desmo eliminates the usual problems with springs read onwhile the absence of conventional spring load saves some frictional loss at low to mid-rpm.
The system consists of a mechanical lifter mechanism that uses a second rocker arm to push the valve closed. The new Hypermotard offers pure fun and adrenaline. The space under this piston contains nitrogen gas at a moderate pressure, such as psi. Schweiz de Schweiz fr Schweiz it.
The closing cam and second set of rocker arms are visible in this diagram and should give you a pretty good idea of how the desmo system differs from a conventional setup. 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. For now, though, desmo valves are an engineering solution of the past that is part of Ducati’s identity in the present.
The desmodromic valve actuation system that Ducati have some patents for is considerably different than the first desmodromic valve actuation systems that were invented and aforementioned. New Burlington Books, Copyright: The Illustrated Encyclopedia of Motorcycles, Editor: Valve float is effectively eliminated and valve timing is perfect throughout all the full rev range.
This increases the seat pressure of the valve the static pressure that holds the valve closed. And in the future? This led to the Ducati Imola Desmo, and the s and s production Ducati V-twin motorcycles.
I think it’s possible that things could shift so that desmo valves once again have a performance edge.
These avoided resonance but were ungainly to locate inside cylinder heads. Formula 1 engine manufacturers use a pneumatic system to close the valves to allow for very high RPM without valve float.
He didn’t draw a salary for that six months. Site valev relatively new, but great fun, with great discussion forumFormula 1 news and forum.