Desmo valvetrain

Interesting , Is the part about disadvantages .
The part about valve Jerk , caught my eye as that was the technique used on the ol'Flathead .
Valve train Dynamics are more complicated then first Glance .
 
Shaw, I actually rode a Ducati Desmo and it was pretty darn fast and the thing that I noticed was that there was no metallic noise from the engine. I think the design was a little different. I believe it used a second complimentary cam to pull the valve back to the seat. "J", it was great... The problem was that it was VERY expensive to build and did require some checking (valve train) and this is probably the reason it was not jumped on by the racing arena. You could get a valve spring engine to run just about as well for a lot less investment, but make no mistake about it, if it were a little cheaper to build, there would be a lot of racers running them.
 
I too have ridden a desmo Ducati for a few years. What techbigdog says is spot on. The system sure isn't cheap, but it was cool that you could not float the valves, even when you reved it a bit beyond the red line.
 
tecbigdog said:
Shaw, I actually rode a Ducati Desmo and it was pretty darn fast and the thing that I noticed was that there was no metallic noise from the engine. I think the design was a little different. I believe it used a second complimentary cam to pull the valve back to the seat. "J", it was great... The problem was that it was VERY expensive to build and did require some checking (valve train) and this is probably the reason it was not jumped on by the racing arena. You could get a valve spring engine to run just about as well for a lot less investment, but make no mistake about it, if it were a little cheaper to build, there would be a lot of racers running them.
Click to expand...
Performance wise it has been very hard to beat those Ducati engines so the design works, but yes, not cheap. That's the only issue with some out of the box designs. It is cheaper to keep building what has been used and built for years. That doesn't mean that it doesn't work or is unreliable.
 
I researched this along with a lot of other designs.

I researched camless systems and the entire system relies the most on being able to control sitting the valve back into the seat without bounce, or slamming it in and breaking the head off, or many other issues.

For this design to have been around since the 50's and actually works as well as it does, is absolutely phenomenal. I'm not sure if most understand how complex this system really is and the forces it controls. The weeks and hours I spent researching and reading white paper after white paper on this among other systems was really enlightening to some different aspects of engines. Even though this system obviously uses Cams, it's still incredibly complex for what it is. The thousands of hours they had to spend back in those days before computer assisted designs and being able to build a system like this even in modern times still amazes me.
 
Last edited:
The intention of the original post was to stir a little conversation from those who had already saw it. And get the gray matter going, in case a completely different problem could use a similar solution.
I see some are not put off because 'everyone else" hasn't seen the need for such things.
Probably some small iteration is in use around you in an unnoticed application.

I spent my youth in the hayfield, using purely mechanical contraptions to do various jobs.
This summer, I revisited on of those things.
The mechanical dump rake.
An incredibly simple device which uses ground speed power to lift and release a dumping motion. Originally conceived when horsepower truly involved horses!

I get to thinking how many simple mechanisms have been replaced by overly complicated electric/computer/hydraulic devices, in the name of progress.

Just some thoughts.

Ps. The original patent for the desmo valvetrain was from the 1800s, in case some did not catch that.
 
You must log in or register to reply here.
Back
Top