From: Epijk@aol.com
Message-ID: <d6.802644d.2860cd57@aol.com>
Date: Tue, 19 Jun 2001 11:44:23 EDT
Subject: Re: 345hp lycoming
To: aaronmay82@lycos.com, lancair.list@olsusa.com
MIME-Version: 1.0
Content-Type: text/plain; charset="US-ASCII"
Content-Transfer-Encoding: 7bit
Reply-To: lancair.list@olsusa.com

          <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>>
          <<  Lancair Builders' Mail List  >>
          <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> 
>>
In a message dated 6/18/2001 6:10:35 PM Pacific Daylight Time, 
aaronmay82@lycos.com writes:

<< I am just beginning to build my 
 know-how when it comes to all things kitplanes, and have stressed that by
 preluding most posts with the classic "open for scrutiny" line. >>

Aaron:

Here's another bit of info which I thought of after I replied yesterday.

A recent Hartzell vibration survey revealed an interesting situation. There 
is a certain Hartzell propeller which is certified on a Lycoming IO-360-A3B6D 
for a specific aircraft. This engine is rated at 200HP, and is equipped with 
8.7:1 compression ratio pistons (LW-10207-S) and 6th and 8th order torsional 
counterweights. In that configuration, the propeller blade stresses were 
acceptable.
 
However, there is an STC which allows the installation of the Lycoming 10:1 
pistons (LW-11487-S from the HIO-360-D1A) to increase the engine power 
output. Hartzell discovered that the installation of those STC'd pistons 
significantly altered the torsional characteristics of the IO-360-A engine, 
to the point that it drove the blade root stresses beyond the endurance limit 
of the material. That engine, with its pendulous torsional absorber 
counterweights, might be expected to be "torsionally tolerant" (for a 
4-cylinder engine). The fact that a relatively small change in engine 
configuration caused such a significant change in vibratory stress gives some 
insight into just how critical this engine/propeller interaction can be, and 
the kind of risks people take making changes to this stuff without 
understanding what's involved.

Jack Kane
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
LML website:   http://www.olsusa.com/Users/Mkaye/maillist.html
LML Builders' Bookstore:   http://www.buildersbooks.com/lancair

Please send your photos and drawings to marvkaye@olsusa.com.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>