X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from poplet2.per.eftel.com ([203.24.100.45] verified) by logan.com (CommuniGate Pro SMTP 5.3.4) with ESMTP id 4178973 for flyrotary@lancaironline.net; Thu, 25 Mar 2010 18:24:57 -0400 Received-SPF: none receiver=logan.com; client-ip=203.24.100.45; envelope-from=lendich@aanet.com.au Received: from sv1-1.aanet.com.au (mail.aanet.com.au [203.24.100.34]) by poplet2.per.eftel.com (Postfix) with ESMTP id 9B17B173879 for ; Fri, 26 Mar 2010 06:24:20 +0800 (WST) Received: from ownerf1fc517b8 (203.171.92.134.static.rev.aanet.com.au [203.171.92.134]) by sv1-1.aanet.com.au (Postfix) with SMTP id 96C7FBEC004 for ; Fri, 26 Mar 2010 06:24:14 +0800 (WST) Message-ID: <26DDD10D345C4AECB36AA23935F7D81F@ownerf1fc517b8> From: "George Lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Rotating Disc Vibration nodes was [FlyRotary] Re: Adaptor plate rivets Date: Fri, 26 Mar 2010 08:24:14 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0077_01CACCBD.B87EBF80" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5843 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 X-Antivirus: avast! (VPS 100325-1, 03/25/2010), Outbound message X-Antivirus-Status: Clean This is a multi-part message in MIME format. ------=_NextPart_000_0077_01CACCBD.B87EBF80 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Richard, I was thinking about that was well for the single, I figured some extra = rotating mass wouldn't hurt in smoothing the torsional vibrations of the = single. What thickness did you settle on. I figured you used the manual = diameter ring gear. George ( down under) Your comments remind me of my initial experience on the SOOB, about = ten years ago. I initially used a flexplate for a flywheel. After the = first 20hrs flying, I found the flexplate cracked around the flange, = where it was riveted to. There was no load going through the flexplate = in my design, all it did was holding the starter ring gear. I solved the = problem with designing and building a much stiffer flywheel, which is = still there.=20 FWIW Richard Sohn N2071U ----- Original Message -----=20 From: Ed Anderson=20 To: Rotary motors in aircraft=20 Sent: Thursday, March 25, 2010 2:03 PM Subject: [FlyRotary] Rotating Disc Vibration nodes was [FlyRotary] = Re: Adaptor plate rivets Have not gone out and checked my rivets on my R1C, will do that this = weekend. However, there is one possibility for the cause of the smoking = rivets that I have not heard addressed and that is vibration nodes of a = rotating disc. There is the possibility that if the disc were in some = oscillatory mode that the smoking rivets might be caused by with the = rivets being at the nodes of certain modes (like that?) of vibration = which could be causing the holes in the discs to be sliding up and down = the shaft of rivet. =20 In the end, it may be important to know what is causing this. The = 20Bs should be smoother than the 13Bs, on the other hand, they do have a = different firing frequency. For the same RPM the number of firing = pulses from the 20B are 1/3 higher than the 13B over the same time = period. That could possibly induce vibration nodes in the disc that = the 13B (which has longer duration between firings pulses). The long = time between firings in the 13B might permit the mass/structure of the = assembly to dampen the amplitude of any such induced vibration between = firings pulses - where not so for the more frequent pulses of the 20B. = The higher the frequency of the input, the stiffer structure that can = be caused to vibrate. A vast over simplification, but thought I would = throw it out just incase somebody had a finite analysis package sitting = on their computer. Just a WAG. =20 Here is an URL that provides a drawing of how such nodes might form = on a disc =20 = http://demonstrations.wolfram.com/NormalOscillatoryModesOfRotatingOrthotr= opicDisks/ =20 Ed Anderson Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com http://www.andersonee.com http://www.dmack.net/mazda/index.html http://www.flyrotary.com/ http://members.cox.net/rogersda/rotary/configs.htm#N494BW http://www.rotaryaviation.com/Rotorhead%20Truth.htm -------------------------------------------------------------------------= --- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] = On Behalf Of Mark Steitle Sent: Thursday, March 25, 2010 2:25 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Adaptor plate rivets =20 Al, =20 I had a bunch of AN-6A bolts, so I used them with two thick washers, = one under the head and one under the nut. I mainly wanted to ensure = that the shank went all the way through both pieces. You might be able = to use AN-5.5A or even AN-5A bolts if you use only one thin washer under = the nut. =20 =20 Mark S. =20 On Thu, Mar 25, 2010 at 11:22 AM, Al Gietzen = wrote: To answer your question about the washers, I used thick washers on = both sides. But I'll have to remove them all in order to replace the = AN-6A bolts with AN173-6A's. I'm hoping the bolts arrive by this = weekend so I can start putting everything back together. =20 Normally washers are needed only under the side that you're turning = to apply the force; unless needed to provide shimming or a more uniform = or larger surface. The -6A length has a 3/8" grip length, and I assumed = the plate was 1/8" and the flange =BC". If the thickness is less I may = have to get some more, or thicker, washers. =20 Al =20 ------=_NextPart_000_0077_01CACCBD.B87EBF80 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 Richard,
 I was thinking about that was = well for the=20 single, I figured some extra rotating mass wouldn't hurt in smoothing = the=20 torsional vibrations of the single. What thickness did you settle on. I = figured=20 you used the manual diameter ring gear.
George ( down under)
Your comments remind me of my initial = experience=20 on the SOOB, about ten years ago. I initially used a flexplate for a = flywheel.=20 After the first 20hrs flying, I found the flexplate cracked around the = flange,=20 where it was riveted to. There was no load going through the flexplate = in my=20 design, all it did was holding the starter ring gear. I solved the = problem=20 with designing and building a much stiffer flywheel, which is still = there.=20
FWIW
 
Richard Sohn
N2071U
----- Original Message -----
From:=20 Ed Anderson
To: Rotary motors in = aircraft=20
Sent: Thursday, March 25, = 2010 2:03=20 PM
Subject: [FlyRotary] Rotating = Disc=20 Vibration nodes was [FlyRotary] Re: Adaptor plate rivets

Have not = gone out=20 and checked my rivets on my R1C, will do that this weekend.  = However,=20 there is one possibility for the cause of the smoking rivets that I = have not=20 heard addressed and that is vibration nodes of a rotating = disc.  There=20 is the possibility that if the disc were in some oscillatory mode = that the=20 smoking rivets might be caused by with the rivets  being at the = nodes=20 of certain modes (like that?) of vibration which could be causing = the holes=20 in the discs to be sliding up and down the shaft of=20  rivet.

 

In the = end, it may=20 be important to know what is causing this.  The 20Bs should be = smoother=20 than the 13Bs, on the other hand, they do have a different firing=20 frequency.  For the same RPM the number of firing pulses from = the 20B=20 are 1/3 higher than the 13B over the same time period.  =  That=20 could possibly induce vibration nodes in the disc that the 13B = (which has=20 longer duration between firings pulses).  The long time between = firings=20 in the 13B might permit the mass/structure of the assembly to dampen = the=20 amplitude of any such induced vibration  between firings pulses = =96 where=20  not so for the more frequent pulses of the 20B. =   The higher=20 the frequency of the input, the stiffer structure that can be caused = to=20 vibrate.  A vast over simplification, but thought I would throw = it out=20 just incase somebody had a finite analysis package sitting on their=20 computer.    Just a WAG.

 

Here is = an URL that=20 provides a drawing of how such nodes might form on a=20 disc

 

http://demonstrations.wolfram.com/NormalOscillatoryMo= desOfRotatingOrthotropicDisks/

 

Ed=20 Anderson

Rv-6A = N494BW Rotary=20 Powered

Matthews, = NC

eanderson@carolina.rr.com

http://www.andersonee.com

http://www.dmack.net/mazda/index.html

http://www.flyrotary.com/

http://members.cox.net/rogersda/rotary/configs.htm#N494BW

http://www.r= otaryaviation.com/Rotorhead%20Truth.htm

From:=20 Rotary motors in = aircraft=20 [mailto:flyrotary@lancaironline.net] On=20 Behalf Of Mark Steitle
Sent: Thursday, March 25, = 2010 2:25=20 PM
To: = Rotary motors in aircraft
Subject: [FlyRotary] Re: = Adaptor plate=20 rivets

 

Al,

 

I had a bunch of AN-6A bolts, so I used = them with=20 two thick washers, one under the head and one under the nut.  I = mainly=20 wanted to ensure that the shank went all the way through both = pieces.=20  You might be able to use AN-5.5A or even AN-5A bolts if you = use only=20 one thin washer under the nut.  

 

Mark S.

 

On Thu, Mar 25, 2010 at 11:22 AM, Al = Gietzen <ALVentures@cox.net>=20 wrote:

To = answer your=20 question about the washers, I used thick washers on both sides. =  But=20 I'll have to remove them all in order to replace the AN-6A bolts = with=20 AN173-6A's.  I'm hoping the bolts arrive by this weekend so I = can start=20 putting everything back together.=20  

Normally washers=20 are needed only under the side that you=92re turning to apply the = force;=20 unless needed to provide shimming or a more uniform or larger = surface. =20 The -6A length has a 3/8=94 grip length, and I assumed the plate was = 1/8=94 and=20 the flange =BC=94.  If the thickness is less I may have to get = some more,=20 or thicker, washers.

 

Al

 

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