On 1/23/2025 9:50 AM, cyclintom wrote:
On Mon Jan 20 21:09:32 2025 Frank Krygowski wrote:
On 1/20/2025 7:30 PM, cyclintom wrote:
On Mon Jan 20 13:17:00 2025 Frank Krygowski wrote:
There's a little history on the "Talk" page regarding desmodromic
valves. Here's that "Talk" page:
https://en.wikipedia.org/wiki/Talk:Desmodromic_valve#Disputed_section:_Disadvantages
I don't see enough to make a confident judgment.
Jobst knew an awful lot about desmodromic valves which I suppose he got acquainted with at Porche trying to eliminate valve float. If you got him talking on the subject you couldn't shut him off. He believed they were the cure for everything,
I think you have that backwards. I suppose I could be wrong. Andrew can
probably clarify.
Frank, you are forever forgetting that I knew Jobst. At ride breaks I would actually listen to him. Do you even know what desmodromic valves mechqanisms are? What can you tell us all about the clearamnces between the actuation cam and the retraction
cam? Maybe you can get Andrew to tell us that he knows moew about things than people who were actually there? Tell us again that roads are built by gas taxes.
I thought this was all well known.
Here's the system:
https://motofomo.com/desmodromic-valves-everything-to-know/
Back in The Ancient Days (1960s), most people concerned with
high performance engines (or amateur putzes like me) and the
engineering community believed that the limit to higher revs
was 'valve bounce'. It was posited in simple physics that
the inertia of the valve mass changed direction too quickly
for the valve springs to respond adequately. Stiffer springs
of course lead to faster wear especially on cam lobes and
hollow stem valves or exotic metal valves led to other problems.
Ducati's desdromonic valve system was an attempt to get
around all that by eliminating the valve springs. It does
that with a cost of complexity and wear but it does actually
work. (the basic idea is very old but Ducati refined and
popularized it)
Eventually, high speed video showed that the 'common wisdom'
was not actually correct. It was an harmonic effect, not a
simple inertia of mass problem. Variable coil valve springs
and other refinements were developed to dramatically reduce
the effect.
I frankly can't recall Mr Brandt's specific issue with Wiki
but his factual corrections, along with his usual snark and
denigration, were not successful.
--
Andrew Muzi
am@yellowjersey.org
Open every day since 1 April, 1971
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