X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail.globalsuite.net ([69.46.103.200] verified) by logan.com (CommuniGate Pro SMTP 5.2.0) with SMTP id 2784576 for flyrotary@lancaironline.net; Sun, 09 Mar 2008 20:11:42 -0400 Received-SPF: none receiver=logan.com; client-ip=69.46.103.200; envelope-from=rusty@radrotary.com X-AuditID: c0a8013c-aa0fcbb000004b31-9a-47d47c961773 Received: from DELLRD1 (unknown [209.114.234.11]) by mail.globalsuite.net (Symantec Mail Security) with ESMTP id D5BB94DC007 for ; Sun, 9 Mar 2008 18:11:01 -0600 (MDT) From: "Russell Duffy" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: Anyone have an RD-1C for sale? Date: Sun, 9 Mar 2008 08:10:24 -0500 Message-ID: <004801c881e6$f10b9b30$09b812c6@DELLRD1> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0049_01C881BD.08359330" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3198 X-Brightmail-Tracker: AAAAAA== This is a multi-part message in MIME format. ------=_NextPart_000_0049_01C881BD.08359330 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable I'm all for agreeing to disagree, as well you know, but I'm still = looking at making the damper harder, rather than softer as in the 2 rotor.=20 =20 Hi George, =20 The way I understand it, there's always a resonant frequency, and not = just because we're talking about single rotors. Two and three rotors have = them too. You can make the coupling loose/soft, to lower the frequency, or tight/hard to raise the frequency. Either will work just fine, as long = as you get the frequency outside of your operating range. =20 =20 Unless you can be SURE your resonant frequency is well outside your operating range, it's much safer to go with the lower frequency = approach. Consider the amount of energy that's available at 2000 rpm vs 8000. At 2000, the drive rattles, and at 8000, the drive breaks. Didn't Everett Hatch break a number of drives this way? =20 =20 Again, I'm not a mechanical engineer, so this may be totally wrong, but = it's the way I "understand" it. My fear of a harder damper is that it might look great up to the static rpm I can run on the ground, but then fail catastrophically when the prop is unloaded in flight. If I'm going to = break something, I'd rather it be at idle :-) =20 =20 A man of your means may wish to opt for the aluminium end housings, =20 =20 When I can order a set of "in-stock" aluminum housings online, without having them custom made, I'll be real interested. The parts I have will work just fine for now. =20 =20 Cheers, Rusty=20 =20 =20 =20 ------=_NextPart_000_0049_01C881BD.08359330 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Message
I'm all for = agreeing to=20 disagree, as well you know, but I'm still looking at making the damper = harder,=20 rather than softer as in the 2 rotor. 
 
Hi=20 George,
 
The way = I understand=20 it, there's always a resonant frequency, and not just because we're = talking=20 about single rotors.  Two and three rotors have them too.  You = can=20 make the coupling loose/soft, to lower the frequency, or tight/hard to = raise the=20 frequency.  Either will work just fine, as long as you get the = frequency outside of your operating=20 range.  
 
Unless you can = be SURE your=20 resonant frequency is well outside your operating range, it's much safer = to go=20 with the lower frequency approach.  Consider the amount of energy = that's=20 available at 2000 rpm vs 8000.  At 2000, the drive rattles, and at = 8000,=20 the drive breaks.  Didn't Everett Hatch break a number of drives = this=20 way? 
 
Again, I'm not a = mechanical=20 engineer, so this may be totally wrong, but it's the way I "understand"=20 it.   My fear of a harder damper is that it might look = great up=20 to the static rpm I can run on the ground, but then fail = catastrophically when=20 the prop is unloaded in flight.  If I'm going to break something, = I'd=20 rather it be at idle :-)  
 
A man of your = means may=20 wish to opt for the aluminium end housings,  
 
When I can order a set = of=20 "in-stock" aluminum housings online, without having them custom made, = I'll be=20 real interested.  The parts I have will work just fine for=20 now.  
 
Cheers,
Rusty
 
 
 
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