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So what is "Desmo" and why is it so cool?



If you're a motorcycle geek, you're probably aware that Ducati engines all use something called Desmo, but you may not understand why they use it or what it really is. Fortunately, we are here to help.

Desmo is short for desmodromic, and it refers to the way a pope
valve
The inside of an engine is controlled. In almost every four-stroke piston engine, the valves open via a camshaft and close with spring pressure coming from a valve spring. It's a well-known system, it works and it's quite simple. Therefore, the dominant system is in place today, even in high-speed racing cars and bikes, but that was not always the case.

The first mention of desmodromic valves comes from several 1

896 patents by Gustav Mees, but it was not until the 1910s that they were used with some real success in a marine engine which, thanks to desmo, dual magnetos and dual overhead valves (even some of a rarity at the time) were able to produce 300 horsepower.


Mercedes-Benz
in the 1950s, began to utilize desmo in its 8-speed racing engines, especially in the 300SLR racing cars that dominated events like the Mille Miglia and the W196 Formula 1 car. These engines were also used in two known 300SLR
coupes
also known as the Uhlenhaut coupons. In combination with Mercedes-Benz's advanced understanding of fuel injection, these racing engines showed themselves to be extremely powerful and reliable.

The famous 300SLR racing car used a fuel injected 3.0 liter straight-8 engine with desmodromic valves.


Rolf Unterberg / German Federal Archives

The appellation of desmodromic valve maneuvers during this time came mainly from the propensity of valve springs to snap or float at higher rpm, which often leads to catastrophic engine failures. This was mainly due to imperfect metallurgy and machining techniques.

Desmodromic valves solve these problems by using a second set of rocker arms and camshades to close the valves directly. This means that regardless of engine rotation, the possibility of valve flow is eliminated. However, it is not all sunshine and roses in desmo land. Additional machining and parts required for the system add cost, and the valve setting process is twice as complicated as it would be in a standard engine. These factors have resulted in desmo almost entirely falling out of favor among manufacturers.

The only manufacturer that sold with technology is Ducati, who started using it on behalf of its famous engine designer Fabio Taglioni in the company's 125cc big prix motorcycle. The technology was so successful that it led to a series of victories, and was implicated in the image of Ducati, even today. Each Ducati uses the technology, from their cheapest Scrambler models to the disastrously expensive factory's MotoGP bikes.

Is it necessary now? Not really. Is that cool? In the words of the famous Robert Evans, "You bet on what you have, it is." So now you know what Desmo is and how it works. Do you want to go on a Ducati and go for a rip? It certainly does for us so if you just excuse us …


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