Desmodromic Valves????????
Thread Starter
Burning Brakes
Joined: Nov 2004
Posts: 1,028
Likes: 0
From: San Antonio Texas
Desmodromic Valves????????
was just watching the speed channel. they had a show about an old Mercedes 300 from the 50's that was used in road racing. it had "desmodromic" valves. my understanding is that these valves have 2 camshafts. one opens the valve, like on any other engine but the other closes the valve. so, NO valve springs, no lash, no valve float at high rpm's, etc. sounds like a winner to me. why don't they use these on cars today? are there inherent problems with them??
Instructor
Joined: Oct 2004
Posts: 173
Likes: 0
From: Hattiesburg MS
Originally Posted by greyghost79
was just watching the speed channel. they had a show about an old Mercedes 300 from the 50's that was used in road racing. it had "desmodromic" valves. my understanding is that these valves have 2 camshafts. one opens the valve, like on any other engine but the other closes the valve. so, NO valve springs, no lash, no valve float at high rpm's, etc. sounds like a winner to me. why don't they use these on cars today? are there inherent problems with them??
Thread Starter
Burning Brakes
Joined: Nov 2004
Posts: 1,028
Likes: 0
From: San Antonio Texas
Originally Posted by bbeck
never heard of them- I'd like to hear more about them
just do a google search using "desmodromic" valves and you'll get a bunch of hits. there must be a down side to using them in cars. maybe they don't stand up to long term use??? just good for racing and rebuilding???? advantages seem obvious, but must be some disadvantages not discussed on the show.
Melting Slicks
Joined: Dec 2000
Posts: 2,198
Likes: 2
From: Eastern Connecticut
They were a good solution given the metals of the day, but modern springs will rev higher than the desmo motors did. It makes for a heavy valve train, lots of loading at high rpm. Plus you have to adjust the lash (both sides) often. Joe
Racer
Joined: Jun 2003
Posts: 368
Likes: 1
From: Lititz PA
Mercedes invented desmodromic valve activation. Ducati perfected it. Its advantage is speed and precision. Ducati is king of piston speed (they need to be running Vtiwns against Vfives,fours etc). On F1 cars they went with pnematic valves.
Advanced
Joined: Jun 2004
Posts: 96
Likes: 0
From: Novelty OH
fun stuff!
My friend has a Ducati 916 with the aforementioned valve train... what a ride! Engineering perfection IMHO and beautiful to boot. 105RWHP on a 380 pound bike = fun as hell
No springs.... cams open and close valves. Requires valve service every 1000 miles I believe. Insane maintenance and insurance costs prevent him from riding it often.
Dry clutch takes some getting used to.. sounds odd on a bike. Has a muscle car tone when you get on it from the v-twin.
The following link may possibly contain offensive pictures. It also has some good shots of the bikes. I hope linking it isn't considered against forum policies.. if it is I'll delete it right away.
http://www.bikepics.com/ducati/916/96/pics.asp
-Matt
No springs.... cams open and close valves. Requires valve service every 1000 miles I believe. Insane maintenance and insurance costs prevent him from riding it often.
Dry clutch takes some getting used to.. sounds odd on a bike. Has a muscle car tone when you get on it from the v-twin.
The following link may possibly contain offensive pictures. It also has some good shots of the bikes. I hope linking it isn't considered against forum policies.. if it is I'll delete it right away.
http://www.bikepics.com/ducati/916/96/pics.asp
-Matt
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