Return-Path: Sender: (Marvin Kaye) To: lml@lancaironline.net Date: Tue, 03 Feb 2004 19:27:49 -0500 Message-ID: X-Original-Return-Path: Received: from imo-r06.mx.aol.com ([152.163.225.102] verified) by logan.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 2973914 for lml@lancaironline.net; Tue, 03 Feb 2004 19:00:23 -0500 Received: from Sky2high@aol.com by imo-r06.mx.aol.com (mail_out_v36_r4.12.) id q.45.45e95dd (18555) for ; Tue, 3 Feb 2004 19:00:17 -0500 (EST) From: Sky2high@aol.com X-Original-Message-ID: <45.45e95dd.2d519010@aol.com> X-Original-Date: Tue, 3 Feb 2004 19:00:16 EST Subject: Re: [LML] Re: Propeller Heads, Help! X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1075852816" X-Mailer: 9.0 for Windows sub 460 -------------------------------1075852816 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 2/3/2004 3:31:11 PM Central Standard Time, Epijk@aol.com writes: HOWEVER, it gives me the willies to consider a solid-crank IO-320 driving a CS-prop which had 7 inches chopped off the blades. Jack, That is the Hartzell design. It's a 84xx-14 --- 84 inch prop less 14 inches. It is just that they don't need all the excess metal when they carve it. <<>>>> There are no restrictions on the "carved prop". Note, however, that I use a Harmonic Damper (or dampener, if you wish). Plus, my most recent engine reincarnation has a heavier crank/flange. I find the smoothest operation above 2600 rpm, acceptable in the 2300-2550 rpm, and ugly in the below 2200 rpm range. Those poor pistons..... <<>> Yep. My concern too. Hartzell speaks through lawyers, so.... so far, nothing useful from them. The prop shop wasn't too concerned, but I am after 150 hours of high speed operation with that nick on one blade about 4 inches from the end. <<>>> Thanks, I'll go look. <<<) If you're determined to keep on flying this prop, you might consider having Hartzell do a vibration survey on your engine/prop/airframe combination. It's not cheap, but it sure beats the prospect of trying to land after the loss of a couple of inches off one blade tip (probably followed soon thereafter by the entire engine).>>> Good Idea. But I think I will contact the prop shop to see if we can make an arrangement about Hartzell carved blades. Scott Krueger AKA Grayhawk Sky2high@aol.com II-P N92EX IO320 Aurora, IL (KARR) "...as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns - the ones we don't know we don't know." D. Rumsfeld -------------------------------1075852816 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
In a message dated 2/3/2004 3:31:11 PM Central Standard Time, Epijk@aol= .com=20 writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>HOWEVER,=20 it gives me the willies to consider a solid-crank IO-320 driving a CS-prop= =20 which had 7 inches chopped off the blades.
Jack,
 
That is the Hartzell design. It's a 84xx-14 --- 84 inch prop less 14=20 inches.  It is just that they don't need all the excess metal when they= =20 carve it.
 
<<<a) The IO-320 crankshaft does not have the torsional-absorb= ing=20 counterweights which the higher-powered 360's have, and in certitfied form,=20= most=20 likely has a yellow band on the tach defining an RPM range best avoided due=20= to=20 harmful interwactions between the engine excitation and one or more natural=20 frequencies of the prop blades;>>>>>
 
There are no restrictions on the "carved prop".  Note, however, th= at I=20 use a Harmonic Damper (or dampener, if you wish).  Plus, my most recent= =20 engine reincarnation has a heavier crank/flange.  I find the smoothest=20 operation above 2600 rpm, acceptable in the 2300-2550 rpm, and ugly in the b= elow=20 2200 rpm range.  Those poor pistons.....
 
<<<c)  The lopping of your blades changed one or more of=20= the=20 blade natural frequencies (most likely causing them to increase), but the=20 magnitude of the change is unknown without a survey. The resulting change co= uld=20 easily cause a serious interaction between a blade frequency and the=20 second-order excitataion of your 4-cylinder engine, which could be stressing= =20 your blades to a level they cannot sustain;>>>
 
Yep.  My concern too.  Hartzell speaks through lawyers, so...= . so=20 far, nothing useful from them.  The prop shop wasn't too concerned, but= I=20 am after 150 hours of high speed operation with that nick on one blade about= 4=20 inches from the end.
 
<<<d) Metal props on direct-drive piston engines pose a daunti= ng=20 set of vibration problems, the solutions to which are non-trivial, but which= =20 include blade profiles, mass distributions, root thicknesses, and a host of=20 other factors, in order to avoid the harmful interactions described above.&n= bsp;=20 Consider the fact that a prop which is safe on a particular certified IO-360= =20 (8.7 compression, counterweighted engine) becomes UNSAFE after the STC'd=20 installation of 10:1 compression pistons (more on that and other prop facts=20= at=20 >>>>
 
Thanks, I'll go look.
 
<<<) If you're determined to keep on flying this prop, you mig= ht=20 consider having Hartzell do a vibration survey on your engine/prop/airframe=20 combination. It's not cheap, but it sure beats the prospect of trying to lan= d=20 after the loss of a couple of inches off one blade tip (probably followed so= on=20 thereafter by the entire engine).>>>
 
Good Idea.  But I think I will contact the prop shop to see if we=20= can=20 make an arrangement about Hartzell carved blades.
 
Scott Krueger=20 AKA Grayhawk
Sky2high@aol.com
II-P N92EX IO320 Aurora, IL=20 (KARR)

"...as we know, there are known knowns; there are things we kn= ow=20 we know. We also know there are known unknowns; that is to say we know there= are=20 some things we do not know. But there are also unknown unknowns - the ones w= e=20 don't know we don't know." D. Rumsfeld
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