round lobe cams
round lobe cams
(OP)
http:// www.youtub e.com/watc h?v=inrBHH VVfng& feature=ch annel_page
hi, anyone knows how this works? are the valves piston like?
hi, anyone knows how this works? are the valves piston like?
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RE: round lobe cams
RE: round lobe cams
RE: round lobe cams
First hit on Google...
http://www.ducatidesmo.com/
Basic stuff.
Rod
RE: round lobe cams
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers for professional engineers
RE: round lobe cams
Mr. Decuir's claims about valvetrain friction are also incorrect. A cam and roller follower with spring closing would have the same friction (or possibly less) as this desmo system. The friction losses are mostly a function of the valvetrain inertia forces and the coefficient of friction at any sliding interfaces. The spring force only provides enough resistance to keep the follower in contact with the cam lobe.
Decuir's valve train components look like they are fairly heavy and would have greater inertias than a conventional valvetrain. So all other things being equal this desmo system would probably have higher mechanical losses.
Finally, although it's hard to tell from the video, this desmo system looks like it requires some force on the rocker arm to keep the valve closed. This means there is always some friction loss at each valve throughout the entire engine cycle. This is not true for a conventional valvetrain. When the valve is seated (ie. the follower is on the cam's base circle) there is no friction loss because there is a slight clearance between the follower and cam lobe. The exception being if there is some sort of hydraulic lash adjuster which does create a very small force.
You can see the details of this device in US Pat. application number 20080060596.
Go here http://patft.uspto.gov/
RE: round lobe cams
thanks for the replys guys, if someone has more info on these kind of desmos (round lobes, or crankshaft like) i'd be thankfull, dont want to invent something from the stone age.
RE: round lobe cams
RE: round lobe cams
I meant something that was already out there for ages and was so undoable that not even a caveman could make it work.
RE: round lobe cams
Old is not necessarily basic, simple or unsophisticated.
Pyramids, Colosseum, concept of democracy, the works of Archimedes, Socrates, Shakespeare, Galileo, Newton and da Vinci spring to mind.
I think the first 4 valve per cylinder twin cam st up was first used about 1912. Quite a few years before Toyota discovered the O2 advantage.
From old and probably unreliable memories, The Mercedes desmo I believe used a system where they used inertia in the valves to overcome the gap due to running clearance on the cam, then used cylinder pressure to keep the valve seated despite the clearance. I also believe that some use a light spring to hol the valve on the seat, especially at idle and cranking rpm for starting.
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers for professional engineers
RE: round lobe cams