RPMS AND SPRINGS

["Thomas Baumen" <thmelda@xxxxxxxxxxxxx>]

"""Hi!    I always have thought that redlines on tachometers (of 4 stroke
       engines) were limited by spring technology, above that RPM the
       springs can't close the intake or exhaust valves fast enough.
       this, of course, is not a problem in desmodromic  engines which
       have positive mechanical opening and closing of the valves, but
       I've only seen on Ducati Desmo motorcycles.
             has anyone seen a desmodromic motor in an automobile?
jAk doskow     '74 115  '91 164  '92 canoe  etc.""""""""""""""""""""""""""""

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The spring seat pressure or the force that holds the valve against the seat
is one of the limiting factors in RPMs. Consumer oriented automobile have to
last longer miles than race engines. Therfore lighter seating pressures are
needed to avoid premature where on the head and valves. Your average car
probably has a seat pressure of about 70 to 100 lbs. A high performance
motor may go as high as 300 or more but will not last 200,000 miles....more
like 5000.But it will rev considerably higher.
 I have never seen a desmodromic system in a automobile although I am sure
it has been tried and probably with success. It however is not as simple to
maintain for dealers or the home mechanic and is also more expensive to
manufacture.

Thomas Baumen

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