X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from smtp1.av-mx.com ([137.118.16.57] verified) by logan.com (CommuniGate Pro SMTP 5.3.4) with ESMTP id 4178944 for flyrotary@lancaironline.net; Thu, 25 Mar 2010 18:12:10 -0400 Received-SPF: pass receiver=logan.com; client-ip=137.118.16.57; envelope-from=res12@fairpoint.net Received: from main (dblt-74-209-35-215.gtcom.net [74.209.35.215]) (Authenticated sender: res12@fairpoint.net) by smtp1.av-mx.com (Postfix) with ESMTP id 15B17291268 for ; Thu, 25 Mar 2010 18:11:33 -0400 (EDT) Message-ID: From: "Richard Sohn" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Rotating Disc Vibration nodes was [FlyRotary] Re: Adaptor plate rivets Date: Thu, 25 Mar 2010 17:11:49 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0094_01CACC3E.4175FA90" 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 This is a multi-part message in MIME format. ------=_NextPart_000_0094_01CACC3E.4175FA90 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable 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_0094_01CACC3E.4175FA90 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Your comments remind me of my initial = experience on=20 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 with=20 designing and building a much stiffer flywheel, which is still there.=20
FWIW
 
Richard Sohn
N2071U
----- Original Message -----
From:=20 Ed=20 Anderson
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 and=20 checked my rivets on my R1C, will do that this weekend.  However, = there=20 is one possibility for the cause of the smoking rivets that I have not = heard=20 addressed and that is vibration nodes of a rotating disc.  There = is the=20 possibility that if the disc were in some oscillatory mode that the = smoking=20 rivets might be caused by with the rivets  being at the nodes of = certain=20 modes (like that?) of vibration which could be causing the holes in = the discs=20 to be sliding up and down the shaft of=20  rivet.

 

In the end, = it may be=20 important to know what is causing this.  The 20Bs should be = smoother than=20 the 13Bs, on the other hand, they do have a different firing = frequency. =20 For the same RPM the number of firing pulses from the 20B are 1/3 = higher than=20 the 13B over the same time period.   That could possibly = induce=20 vibration nodes in the disc that the 13B (which has longer duration = between=20 firings pulses).  The long time between firings in the 13B might = permit=20 the mass/structure of the assembly to dampen the amplitude of any such = induced=20 vibration  between firings pulses =96 where  not so for the = more=20 frequent pulses of the 20B.   The higher the frequency of = the input,=20 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=20 finite analysis package sitting on their computer.  =   Just a=20 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,=20 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 = [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 two=20 thick washers, one under the head and one under the nut.  I = mainly wanted=20 to ensure that the shank went all the way through both pieces. =  You might=20 be able to use AN-5.5A or even AN-5A bolts if you use only one thin = washer=20 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 I'll=20 have to remove them all in order to replace the AN-6A bolts with = AN173-6A's.=20  I'm hoping the bolts arrive by this weekend so I can start = putting=20 everything back together.=20  

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

 

Al

 

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