Ran across this - R-4360 doc.

http://www.geocities.com/Pentagon/Quarters/4980/engine9.html

One thing I found interesting is that the gear reduction unit is 0.375:1
(certainly propeller:engine) - planetary and spur (so it says)?  Said
the other way, that ratio is 1:2.67.  This engine is typically rated at
2700RPM, which gives a prop RPM of 1012 - slow.  Gives you an idea of
how slow it needs to be for efficiency and sound output when converting
that much hp to thrust.

Someplace else I ran across an R-2800 doc which showed that it used a
ratio of 0.45:1 (1:2.22)..  It's rated at 2800RPM, which gives 1260RPM
at the prop.

These are engines used on nice, potentially quiet, fast airplanes, with
big props.  And have good fuel economy.  No ducted fans.


Regards,

Matt-



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