Redline (formerly the Beater thread)

Jay Honeck wrote:
However, the part of the question I was referring to was if you *shortened*
the prop. Part of the original post implied that you would be able to
simply *increase* the engine's redline RPM if you shortened your prop,
regardless of engine limitations. I don't believe this is true.

I think at that point, you'd be getting into limitations of the engine
components (with some tolerance).



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Shorten the prop, lengthen the prop, change the pitch and you will
necessisarily change the placement of the redline on the tach.
No you won't. Redline is engine speed related only. Redline has a fixed rpm
no matter what you attach or change at the output shaft (in our case a
propeller). Take the prop off and use full throttle... the engine will most
certainly reach redline, the same redline you had before you removed the
prop. Redline speed does not change. The engine has a point where spinning
it faster starts floating valves and causing damage. This is a constant
speed. If you change the pitch and/or increase size of the prop, the engine
won't be able to spin the large prop up to redline. This doesn't mean the
engine won't have huge amount of stress on it trying to do so. It won't
reach redline, but redline remains at the same speed.

Richard

"EDR" wrote in message
...
Interesting that many have not defined the origin of the placement of
the "red line" on the tachometer.

I don't know where to look it up, but I suspect it has something to do
with prop tip speed (as one poster mentioned).


Change the pistons (bore); change the rods (stroke); change the rings
(compression); change the induction system; change the exhaust (back
pressure) and you change the torque of the engine, again altering the
redline.