X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: <13brv3@bellsouth.net> Received: from imf17aec.mail.bellsouth.net ([205.152.59.65] verified) by logan.com (CommuniGate Pro SMTP 5.0.6) with ESMTP id 916695 for flyrotary@lancaironline.net; Sat, 07 Jan 2006 13:47:44 -0500 Received-SPF: pass receiver=logan.com; client-ip=205.152.59.65; envelope-from=13brv3@bellsouth.net Received: from ibm57aec.bellsouth.net ([65.6.194.9]) by imf17aec.mail.bellsouth.net with ESMTP id <20060107184656.HMBP23346.imf17aec.mail.bellsouth.net@ibm57aec.bellsouth.net> for ; Sat, 7 Jan 2006 13:46:56 -0500 Received: from rd ([65.6.194.9]) by ibm57aec.bellsouth.net with ESMTP id <20060107184655.QOUP8357.ibm57aec.bellsouth.net@rd> for ; Sat, 7 Jan 2006 13:46:55 -0500 From: "Russell Duffy" <13brv3@bellsouth.net> To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: RD-1B Service alert & Rusty's damper question Date: Sat, 7 Jan 2006 12:46:56 -0600 Message-ID: <000001c613ba$bc646a20$6101a8c0@rd> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C61388.71CC6B20" 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 V6.00.2900.2527 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C61388.71CC6B20 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Rusty was asking the dimensions and durometer of the rubber dampers in = the drive. I think the question was aiming to change durometer in order to change the resonant frequency on his one rotor installation. The = diameter of dampers is 1.374" and durometer is currently 50. I don't think = changing this will significantly change the fundamental (lowest order) resonance = that occurs at low speed (idle area). This is primarily affected by the = system lash. The dampers significantly affect only higher order harmonics = which can't often be felt but can be very destructive to the drive train. =20 =20 Bottom line is I think it would be a wasted effort to change the rubber dampers. =20 =20 Thanks for the info, and comments Tracy. It's a bit too soon to panic, because I just haven't had enough chance to see where the vibrations = really occur. Unfortunately, it looks like it's going to be in the low to mid = 2000 rpm range, which will be a problem. I hope to run it some more tomorrow afternoon (or yesterday, depending on when this message arrives). =20 =20 Since you say the system lash affects the fundamental resonance, would = it be reasonable to enlarge the bolt hole in the rubber dampener just a bit, = to allow a bit more lash at that point? That should be easy to do, and I'm sure I could buy a few extra stock dampeners from you if it doesn't work out. =20 =20 Thanks, Rusty (010706/1247) =20 Off to cabinet and shelving hell... =20 ------=_NextPart_000_0001_01C61388.71CC6B20 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Message
Rusty was asking the dimensions and durometer of the = rubber dampers in=20 the drive.  I think the question was aiming to change = durometer in=20 order to change the resonant frequency on his one rotor = installation.  The=20 diameter of dampers is 1.374" and durometer is currently 50.  I = don't think=20 changing this will significantly change the fundamental (lowest order) = resonance=20 that occurs at low speed (idle area).  This is primarily affected = by the=20 system lash.  The dampers significantly affect only higher order = harmonics=20 which can't often be felt but can be very destructive to the drive = train. =20
 
Bottom line is I think it would be a wasted effort to change the = rubber=20 dampers.
 
 
Thanks=20 for the info, and comments Tracy.  It's a bit too soon to panic, = because I=20 just haven't had enough chance to see where the vibrations really=20 occur.  Unfortunately, it looks like it's going to be in the low to = mid=20 2000 rpm range, which will be a problem.  I = hope to run=20 it some more tomorrow afternoon (or yesterday, depending on when this = message=20 arrives). 
 
Since=20 you say the system lash affects the fundamental = resonance, would it be=20 reasonable to enlarge the bolt hole in the rubber dampener = just a bit,=20 to allow a bit more lash at that point?  That should be easy = to do,=20 and I'm sure I could buy a few extra stock dampeners from you if it = doesn't work=20 out. 
 
Thanks,
Rusty=20 (010706/1247)
 
Off to=20 cabinet and shelving hell...
  
------=_NextPart_000_0001_01C61388.71CC6B20--