"Håken" wrote in message
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try rec.motorcycles or a motor group
"Tim Wescott" skrev i melding
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Why is it that reed valves are so successful in high-performance
motorcycle two strokes yet are only used in teeny 'sport' class model
airplane engines? Is it just because you can't get suitable reed
material in such small sizes?

Inquiring minds want to know.

Two-stroke design has advanced a great deal since I was interested in it,
but the general idea of reed valves is that they allow a broader torque
range, with fairly even crank-filling over a wide range of rpm.

Disk-type or other crank-timed or piston-timed inlets produce a uniform
number of rotation-degrees of inlet opening, but that becomes a shorter
*time* of inlet opening as rpm increase. Thus, they lead to sharper torque
peaks, even though they may allow slightly greater peak horsepower at the
rpm for which they're tuned. But good reed-valve design hardly steals any
peak horsepower.

--
Ed Huntress