On Tue, 19 Sep 2006 12:11:19 -0400, newsreader
wrote:

On Tue, 19 Sep 2006 10:53:19 -0500, pittss1c
wrote:


But running it that RPM would take the TBO down drastically. I grew up
in Miami, and used to hang around Tamiami airport. All those Pitts
guys used to overspeed their engines like that. And most of them got
around 300 hours before they needed to overhaul their engines.
Those kinds of RPMs are okay for racing and aerobatics, but be ready
for a very early overhaul.

Are you sure about the RPM's contribution to the 300 Hr overhaul?
I would imagine that crank stress due to gyro maneuvers, and full power
climbs followed by immediate power off maneuvers might be a more
dominating factor to short time between overhauls.

Mike



I've also heard that the guys installing 10 to 1 pistons are only
getting 300 hours before overhaul. I'm building a Glasair 3, and know
some other builders that have done that. It brings the power up to
about 330, from 300hp. But to me isn't worth it. It enters into
unknowns in regard to engine/propeller harmonics, drastically cuts
down on the TBO, and does who knows what to the crank, bearings, and
other engine parts. I talked to the late Bob Herendeen about that
when he had just finished his G-3, and he said he did nothing to boost
the engines power beyond what it was designed for. For reliability. I
can only imagine that running up into the RPM's you are talking about
could only involve similar stresses to the engine.

2500 continuous and 2750 rpm tops is set where it is because engines
that loaf along at that get to TBO.

TBO -time between overhauls- is a certified engine concept. take the
engine over 2750 and there is no TBO because you have just negated the
certification requirements.
What I was getting to with brown eyes is that the engine is capable of
doing a lot more than the pedestrian RPM's that get you the 2000 hours
between teardowns. If you want the rpm's and the hp then accept that
you are now driving an experimental engine with no known service
history. ....which really is no different from his much loved car
engines.
Stealth Pilot