X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail14.syd.optusnet.com.au ([211.29.132.195] verified) by logan.com (CommuniGate Pro SMTP 5.2c1) with ESMTPS id 2554793 for flyrotary@lancaironline.net; Tue, 04 Dec 2007 01:30:38 -0500 Received-SPF: none receiver=logan.com; client-ip=211.29.132.195; envelope-from=lendich@optusnet.com.au Received: from george (d58-105-147-234.dsl.nsw.optusnet.com.au [58.105.147.234]) by mail14.syd.optusnet.com.au (8.13.1/8.13.1) with SMTP id lB46ThLM015669 for ; Tue, 4 Dec 2007 17:29:45 +1100 Message-ID: <001d01c8363f$12334a90$ea93693a@george> From: "George Lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Giving up on single rotor Date: Tue, 4 Dec 2007 16:29:47 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_001A_01C83692.E28F0CD0" 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_001A_01C83692.E28F0CD0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MessageOk Al, I can understand that now that you have explained it further. All we have to do is marry up the frequency of the single rotor, one = pulse per shaft rotation, to that of a known damper. We know that the more outward (to the edge of the flexplate) and the = softer the damper the better for the 2 rotor, 2 pulses per shaft = rotation . I believe that Richard's suggestion that the damper for the single be = closer to the centre of the flexplate. George (down under) I don't have any expertise on this subject. But I do play around with = harmonic vibrations all the time in physics lab. I understand aspects = from statistical point of view too. Here's my wild theory: Apply torque wrench to the damper. Also measure the angle of that = wrench as you apply torque. You would end up with chart that says: at 1 = degree, you have 5 lbs. At 3 degrees you have 18 lbs. Etc. If you change = the durometer of ONE of your dampers, you change the above numbers AND = the frequency response of the unit. Using above numbers you should be = able to predict effect and test a whole bunch of frequency responses. = That would allow you to tune the device to optimize the damping. It gets = you away from the "Aha!" approach of experimenting. Converts your ideas = into numbers.=20 Just an idea. I could be totally full of it. -al wick ----- Original Message -----=20 From: George Lendich=20 To: Rotary motors in aircraft=20 Sent: Sunday, December 02, 2007 3:05 PM Subject: [FlyRotary] Re: Giving up on single rotor Al, It sounds like you might be right - but I wish I had an idea of what = your talking about in regard to torque V angle of deflection. I do my best but you have me beat on this one. George ( down under) ----- Original Message -----=20 From: Al Wick=20 To: Rotary motors in aircraft=20 Sent: Monday, December 03, 2007 1:19 AM Subject: [FlyRotary] Re: Giving up on single rotor Instead of using durometer in this case. I think it would be = better to measure torque vs. angle of deflection. Using torque wrench = and simple angle measure device. If you graphed this, you would end up = with a chart that defines frequency response of the damper. Goal to have = damper frequency response that's out of phase with the worst torsional = pulses.=20 Once you've measured frequency response, you could then tune it = with durometer tweaks. So you might end up with 2 dampers at 50 = durometer, 2 at 40, to obtain your ideal frequency response of system. I've always been drawn to having damper that has more than one = frequency response. You never see designs like that. So with mild TV, it = would respond one way. Suddenly it would have different response with = larger TV. Both responses out of phase. They use this method with = electronics and I've seen a few auto clutch dampers utilizing the = concept.=20 FWIW al wick ----- Original Message -----=20 From: George Lendich=20 To: Rotary motors in aircraft=20 Sent: Saturday, December 01, 2007 10:46 PM Subject: [FlyRotary] Re: Giving up on single rotor Righ-t-o Rusty! Thanks George ( down under) So what durometer is your gut feeling now that you went this = far?=20 Hi George, I don't think you can compare the durometer of one damper to = another, because the physical size is as important as the hardness of = the rubber. The Autoflight drive uses a stock Centaflex coupler that's = only available in 50 and 60 durometer. It's a fairly large diameter, = and thick coupler. 50 was better than 60, but two 50's (effectively 25) = in series was way too soft. Maybe a 40 would be good, but it doesn't = exist. =20 Richard seems to be having better luck with the Hirth drive. = Two strokes are rough at low rpms, so perhaps they already have the = right damper for the job. I also suspect his engine has softer power = pulses at low rpms. It's a 12A for one, and PP for another. PP is = great at high rpms, but not know for good power down low. It's the best = theory I have. =20 Cheers, Rusty =20 ---------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG Free Edition.=20 Version: 7.5.503 / Virus Database: 269.16.11/1161 - Release = Date: 30/11/2007 12:12 PM -Al Wick Cozy IV powered by Turbo Subaru 3.0R with variable valve lift and = cam timing.=20 Artificial intelligence in cockpit, N9032U 240+ hours from = Portland, Oregon Glass panel design, Subaru install, Prop construct, Risk = assessment info: http://www.maddyhome.com/canardpages/pages/alwick/index.html -------------------------------------------------------------------------= - No virus found in this incoming message. Checked by AVG Free Edition.=20 Version: 7.5.503 / Virus Database: 269.16.11/1161 - Release Date: = 30/11/2007 12:12 PM -Al Wick Cozy IV powered by Turbo Subaru 3.0R with variable valve lift and cam = timing.=20 Artificial intelligence in cockpit, N9032U 240+ hours from Portland, = Oregon Glass panel design, Subaru install, Prop construct, Risk assessment = info: http://www.maddyhome.com/canardpages/pages/alwick/index.html -------------------------------------------------------------------------= ----- No virus found in this incoming message. Checked by AVG Free Edition.=20 Version: 7.5.503 / Virus Database: 269.16.11/1161 - Release Date: = 30/11/2007 12:12 PM ------=_NextPart_000_001A_01C83692.E28F0CD0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message
Ok Al,
I can understand that now that you have = explained=20 it further.
 
All we have to do is marry up the = frequency of the=20 single rotor, one pulse per shaft rotation, to that of a known=20 damper.
 
We know that the more outward (to the = edge of=20 the flexplate) and the softer the damper the better for the 2 = rotor, 2=20 pulses per shaft rotation .
 
I believe that Richard's suggestion = that the damper=20 for the single be closer to the centre of the flexplate.
 
George (down under)
I don't have any expertise on this = subject. But I=20 do play around with  harmonic vibrations all the time in physics = lab. I=20 understand aspects from statistical point of view too. Here's my wild=20 theory:
 
Apply torque wrench to the damper. = Also measure=20 the angle of that wrench as you apply torque. You would end up with = chart that=20 says: at 1 degree, you have 5 lbs. At 3 degrees you have 18 lbs. Etc. = If you=20 change the durometer of ONE of your dampers, you change the above = numbers AND=20 the frequency response of the unit. Using above numbers you should be = able to=20 predict effect and test a whole bunch of frequency responses. That = would allow=20 you to tune the device to optimize the damping. It gets you away from = the=20 "Aha!" approach of experimenting. Converts your ideas into numbers.=20
 
Just an idea. I could be totally full = of=20 it.
 
-al wick
----- Original Message -----
From:=20 George Lendich
To: Rotary motors in = aircraft=20
Sent: Sunday, December 02, = 2007 3:05=20 PM
Subject: [FlyRotary] Re: = Giving up on=20 single rotor

Al,
It sounds like you might be right - = but I wish=20 I had an idea of what your talking about in regard to torque V angle = of=20 deflection.
I do my best but you have me beat = on this=20 one.
George ( down under)
----- Original Message ----- =
From:=20 Al = Wick
To: Rotary motors in = aircraft=20
Sent: Monday, December 03, = 2007 1:19=20 AM
Subject: [FlyRotary] Re: = Giving up on=20 single rotor

Instead of using durometer in = this case. I=20 think it would be better to measure torque vs. angle of = deflection. Using=20 torque wrench and simple angle measure device. If you graphed = this, you=20 would end up with a chart that defines frequency response of the = damper.=20 Goal to have damper frequency response that's out of phase with = the worst=20 torsional pulses.
 
Once you've measured frequency = response, you=20 could then tune it with durometer tweaks. So you might end up with = 2=20 dampers at 50 durometer, 2 at 40, to obtain your ideal frequency = response=20 of system.
 
I've always been drawn to having = damper that=20 has more than one frequency response. You never see designs like = that. So=20 with mild TV, it would respond one way. Suddenly it would have = different=20 response with larger TV. Both responses out of phase. They use = this method=20 with electronics and I've seen a few auto clutch dampers utilizing = the=20 concept.
 
FWIW
 
al wick
----- Original Message ----- =
From:=20 George Lendich =
To: Rotary motors in = aircraft=20
Sent: Saturday, December = 01, 2007=20 10:46 PM
Subject: [FlyRotary] Re: = Giving up=20 on single rotor

Righ-t-o Rusty!
Thanks
George ( down = under)
So what durometer is = your gut=20 feeling now that you went this far? 
 
Hi=20 George,
 
I = don't think you=20 can compare the durometer of one damper to another, because = the=20 physical size is as important as the hardness of the = rubber.  The=20 Autoflight drive uses a stock Centaflex coupler that's only = available=20 in 50 and 60 durometer.  It's a fairly large diameter, = and thick=20 coupler.  50 was better than 60, but two 50's = (effectively 25) in=20 series was way too soft.  Maybe a 40 would be good, = but it=20 doesn't exist.  
 
Richard seems=20 to be having better luck with the Hirth drive.  = Two=20 strokes are rough at low rpms, so perhaps they = already have the=20 right damper for the job.  I also suspect his engine has = softer=20 power pulses at low rpms.  It's a 12A for one, and PP for = another.  PP is great at high rpms, but not know for good = power=20 down low.  It's the best theory I=20 have.  
 
Cheers,
Rusty=20  

No virus found in this incoming message.
Checked by = AVG Free=20 Edition.
Version: 7.5.503 / Virus Database: 269.16.11/1161 = -=20 Release Date: 30/11/2007 12:12 = PM
-Al Wick
Cozy IV powered by Turbo Subaru 3.0R with = variable valve=20 lift and cam timing.
Artificial intelligence in cockpit, = N9032U 240+=20 hours from Portland, Oregon
Glass panel design, Subaru install, = Prop=20 construct, Risk assessment info:
htt= p://www.maddyhome.com/canardpages/pages/alwick/index.html

No virus found in this incoming message.
Checked by AVG = Free=20 Edition.
Version: 7.5.503 / Virus Database: 269.16.11/1161 - = Release=20 Date: 30/11/2007 12:12 PM
-Al Wick
Cozy IV powered by Turbo Subaru 3.0R with variable = valve lift=20 and cam timing.
Artificial intelligence in cockpit, N9032U 240+ = hours from=20 Portland, Oregon
Glass panel design, Subaru install, Prop = construct, Risk=20 assessment info:
htt= p://www.maddyhome.com/canardpages/pages/alwick/index.html

No virus found in this incoming message.
Checked by AVG Free = Edition.
Version: 7.5.503 / Virus Database: 269.16.11/1161 - = Release Date:=20 30/11/2007 12:12 PM
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