X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail13.syd.optusnet.com.au ([211.29.132.194] verified) by logan.com (CommuniGate Pro SMTP 5.2.0) with ESMTPS id 2785848 for flyrotary@lancaironline.net; Mon, 10 Mar 2008 17:29:59 -0400 Received-SPF: pass receiver=logan.com; client-ip=211.29.132.194; envelope-from=lendich@optusnet.com.au Received: from george (d58-105-155-27.dsl.nsw.optusnet.com.au [58.105.155.27]) by mail13.syd.optusnet.com.au (8.13.1/8.13.1) with SMTP id m2ALTBtt026621 for ; Tue, 11 Mar 2008 08:29:12 +1100 Message-ID: <000f01c882f5$c9c6b360$1b9b693a@george> From: "George Lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Anyone have an RD-1C for sale? Date: Tue, 11 Mar 2008 07:29:12 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_000C_01C88349.9A6A2D00" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Antivirus: avast! (VPS 0657-0, 12/12/2006), Outbound message X-Antivirus-Status: Clean This is a multi-part message in MIME format. ------=_NextPart_000_000C_01C88349.9A6A2D00 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MessageRusty, Your absolutely correct about the frequency and that you must keep that = out of the operating range - however my concern is the large torque = reversals that accompany that frequency. As I see it there are two parts to this equation, so although I lean to = the harder rather than softer damper it's because the large torque = reversals may be still reversing while your trying to push them forward, = the shorter you keep the reversal ( to a point) the less this conflict = will occur - I believe I have discussed this before. Now this doesn't mean I am looking at rock hard dampers, it just means I = will look at different material such as Polyurethane the same stuff used = in 4WD shackle rubbers and although you can get it in different = densities the standard material is approx Shore 93. Although I'm not sure my assessment is correct, I am still working = toward this as my solution, I mention it only as a possible option. George (down under) 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 Hi George, 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. = 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 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 A man of your means may wish to opt for the aluminium end housings, =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 Cheers, Rusty=20 -------------------------------------------------------------------------= ----- No virus found in this incoming message. Checked by AVG.=20 Version: 7.5.518 / Virus Database: 269.21.7/1322 - Release Date: = 9/03/2008 12:17 PM ------=_NextPart_000_000C_01C88349.9A6A2D00 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message
Rusty,
Your absolutely correct about the = frequency and=20 that you must keep that out of the operating range - however my concern = is the=20 large torque reversals that accompany that frequency.
 
As I see it there are two parts to this = equation,=20 so although I lean to the harder rather than softer damper it's because = the=20 large torque reversals may be still reversing while your trying to push = them=20 forward, the shorter you keep the reversal ( to a point) the less this = conflict=20 will occur - I believe I have discussed this before.
 
Now this doesn't mean I am looking at = rock hard=20 dampers, it just means I will look at different material such as = Polyurethane=20 the same stuff used in 4WD shackle rubbers and although you can get it = in=20 different densities the standard material is approx Shore = 93.
 
Although I'm not sure my assessment is = correct, I=20 am still working toward this as my solution, I mention it only as a = possible option.
George (down under)
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=20 talking about single rotors.  Two and three rotors have them = too. =20 You can make the coupling loose/soft, to lower the frequency, or = tight/hard to=20 raise the frequency.  Either will work just fine, as long as you=20 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
 
 
 

No virus found in this incoming message.
Checked by AVG.=20
Version: 7.5.518 / Virus Database: 269.21.7/1322 - Release Date: = 9/03/2008=20 12:17 PM
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