Actually, for the very High end engines or very High RPM engines, Rod
"Stretch" does become a factor in High compression engines. When valve to
Piston clearance is critical and VERY close, Rod materials come in to play
and the loaded stretch of the rod is critical. When the Piston is thrust up
into the cylinder, reaching max velocity at approximately 90 degrees BTDC,
it will tend to want to continue in that direction until another force is
acting upon it. (One of Newton's laws), As the rod is trying to pull on
the Piston, the rod will stretch just a bit, and will increas with
RPM..These are facts that must be taken into consideration if building a
VERY HOT engine. All of the custom Piston companies will have specs on this
factor for performance oriented rods.
Rich
>Let me introduce you to another physicist, Robert Hooke (1635-1703), the
>author of Hooke's law which simply states that there is a linear
>relationship between stress (force applied) and strain (elongation or
>compression) produced; that us up to the "elastic limit" where, as you say,
>permanent changes occur. Engineers use Young's modulus, "tensile" strength,
>"yield" strength and "failure" limit to more finely dice this idea, but
>this is, as they say, "beyond the scope of this discussion".
>>Theo Smit
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