X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.121] verified) by logan.com (CommuniGate Pro SMTP 5.2.14) with ESMTP id 3749863 for flyrotary@lancaironline.net; Wed, 08 Jul 2009 17:15:15 -0400 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.121; envelope-from=eanderson@carolina.rr.com Received: from computername ([75.191.186.236]) by cdptpa-omta04.mail.rr.com with ESMTP id <20090708211436118.DUZS2041@cdptpa-omta04.mail.rr.com> for ; Wed, 8 Jul 2009 21:14:36 +0000 From: "Ed Anderson" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: Spreadsheet for Prop Tip Speed PropTipSpeedCal.xls Date: Wed, 8 Jul 2009 17:14:55 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0021_01C9FFEF.9D83FFB0" X-Mailer: Microsoft Office Outlook, Build 11.0.5510 Thread-Index: AcoABO4410KetEugQiaLWfx4PxQJqgAC3QVg X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 In-Reply-To: Message-Id: <20090708211436118.DUZS2041@cdptpa-omta04.mail.rr.com> This is a multi-part message in MIME format. ------=_NextPart_000_0021_01C9FFEF.9D83FFB0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Hi Bernie, Certainly not an expert here, but my understanding is that at the atmospheric altitudes we fly at that air temperature is the dominant factor governing the speed of sound, not density, not humidity, not pressure - at least not significantly. But, then my interpretation could be wrong. Forward speed of the aircraft is a factor to consider as others have pointed out. I know that compressibility effects start long before a shock wave is created at the speed of sound, the latter which you certainly want to avoid. I imagine that the shape of the object probably has a lot to do with it not to mention that you have the radial speed component and the horizontal speed component all interacting. Airflow around the prop is probably being affected long before the speed of sound - but, how long I simply don't know. I would suggest research on the internet on the topic. Ed 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 Berniehb7448@wmconnect.com Sent: Wednesday, July 08, 2009 3:46 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Spreadsheet for Prop Tip Speed PropTipSpeedCal.xls In a message dated 7/8/2009 8:32:41 AM Central Daylight Time, eanderson@carolina.rr.com writes: Subj:[FlyRotary] Spreadsheet for Prop Tip Speed PropTipSpeedCal.xls Date:7/8/2009 8:32:41 AM Central Daylight Time From: eanderson@carolina.rr.com (Ed Anderson) Sender: flyrotary@lancaironline.net (Rotary motors in aircraft) Reply-to: flyrotary@lancaironline.net (Rotary motors in aircraft) To: flyrotary@lancaironline.net (Rotary motors in aircraft) File:PropTipSpeedCal.xls (28672 bytes) DL Time (49333 bps): < 1 minute Hi folks, Attached is a spreadsheet for calculation of propeller tip speed both static and moving through the air. Thanks to Bernie and Bill for the equations - I have not attempt to verify the equations, but they appear to be accurate and further more if you put zero airspeed in the moving prop equation, you get the same calculated values as the static prop - so appears they are in agreement and accurate. You may change any value shown in color Blue - the rest of the spreadsheet is protected so folks don't accidentally erase an equation in a cell by putting a number in it. But, you can view the equations in each cell, so if someone wants to duplicate it unprotected - have at it. Enjoy Ed The message is ready to be sent with the following file or link attachments: PropTipSpeedCal.xls Note: To protect against computer viruses, e-mail programs may prevent sending or receiving certain types of file attachments. Check your e-mail security settings to determine how attachments are handled. __________ Information from ESET NOD32 Antivirus, version of virus signature database 3267 (20080714) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html ----------------------- Headers -------------------------------- Return-Path: Received: from rly-ma04.mx.aol.com (rly-ma04.mail.aol.com [172.20.116.48]) by air-ma02.mail.aol.com (v124.15) with ESMTP id MAILINMA023-8a14a549fe81f3; Wed, 08 Jul 2009 09:32:41 -0400 Received: from logan.com (mail.logan.com [207.58.244.114]) by rly-ma04.mx.aol.com (v124.15) with ESMTP id MAILRELAYINMA043-8a14a549fe81f3; Wed, 08 Jul 2009 09:32:24 -0400 X-Virus-Scanned: clean according to Sophos on Logan.com X-ListServer: CommuniGate Pro LIST 5.2.14 List-Unsubscribe: List-ID: List-Archive: Precedence: list Message-ID: Reply-To: "Rotary motors in aircraft" Sender: "Rotary motors in aircraft" To: "Rotary motors in aircraft" From: "Ed Anderson" Date: Wed, 8 Jul 2009 09:32:04 -0400 MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_NextPart_000_0000_01C9FFAE.F4671B00" X-Original-Message-Id: <20090708133145097.FYNB19322@cdptpa-omta02.mail.rr.com> Subject: [FlyRotary] Spreadsheet for Prop Tip Speed PropTipSpeedCal.xls X-AOL-IP: 207.58.244.114 X-AOL-SCOLL-SCORE:0:2:480857184:93952408 X-AOL-SCOLL-URL_COUNT:0 That spreadsheet is really cool! I did not know about what affects speed of sound (humidity, etc.), I thought it would be air density (altitude). Because of such arbitrary influences that can't be accounted for in a formula, I would probably "red-line" the RPM at no more than 100 MPH below speed of sound. Those influences could, at times, change the formula speed of sound while you are flying, so that your prop RPM could enter the speed of sound range just by chance of changing air properties. In my sample formula, you can see what the difference in RPM can do. Add 500 RPM, and it puts your prop tips a hair away from speed of sound. Do you think a 100 MPH below speed of sound limit is reasonably safe? Thanks, Bernie ------=_NextPart_000_0021_01C9FFEF.9D83FFB0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Hi = Bernie,

 

Certainly not an expert here, but = my understanding is that at the atmospheric altitudes we fly at that air temperature is the dominant factor governing the speed of sound, not = density, not humidity, not pressure – at least not significantly.  = But, then my interpretation could be wrong.

 

Forward speed of the aircraft is a = factor to consider as others have pointed out.  I know that = compressibility effects start long before a shock wave is created at the speed of sound, = the latter  which you certainly want to avoid.  I imagine that the = shape of the object probably has a lot to do with it not to mention that you = have the radial speed component and the horizontal speed component all interacting.  Airflow around the prop is probably being affected = long before the speed of sound – but, how long I simply don’t know.  I would suggest research on the internet on the = topic.

 

Ed

 

From: = Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Berniehb7448@wmconnect.com
Sent: Wednesday, July 08, = 2009 3:46 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Spreadsheet for Prop Tip Speed = PropTipSpeedCal.xls

 

In a message dated 7/8/2009 8:32:41 AM Central = Daylight Time, eanderson@carolina.rr.com writes:



Subj:[FlyRotary] Spreadsheet for Prop Tip Speed = PropTipSpeedCal.xls
Date:7/8/2009 8:32:41 AM Central Daylight Time
From:    eanderson@carolina.rr.com (Ed Anderson)
Sender:    flyrotary@lancaironline.net (Rotary motors in aircraft)
Reply-to:    flyrotary@lancaironline.net (Rotary motors in aircraft)
To:    flyrotary@lancaironline.net (Rotary motors in aircraft)

File:PropTipSpeedCal.xls = (28672 bytes) DL Time (49333 bps): < 1 minute



Hi folks,

Attached is a spreadsheet for calculation of propeller tip speed both = static
and moving through the air.  Thanks to Bernie and Bill for the = equations - I
have not attempt to verify the equations, but they appear to be accurate = and
further more if you put zero airspeed in the moving prop equation, you = get
the same calculated values as the static prop - so appears they are in =
agreement and accurate.

You may change any value shown in color Blue - the rest of the = spreadsheet
is protected so folks don't accidentally erase an equation in a cell by =
putting a number in it.  But, you can view the equations in each = cell, so if
someone wants to duplicate it unprotected - have at it.

Enjoy

Ed



The message is ready to be sent with the following file or link = attachments:

PropTipSpeedCal.xls


Note: To protect against computer viruses, e-mail programs may prevent =
sending or receiving certain types of file attachments.  Check your = e-mail
security settings to determine how attachments are handled.


__________ Information from ESET NOD32 Antivirus, version of virus = signature
database 3267 (20080714) __________

The message was checked by ESET NOD32 Antivirus.

http://www.eset.com



--
Homepage:  http://www.flyrotary.com/
Archive and UnSub:   http://mail.lancaironline.net:81/lists/flyrotary/List.html =


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Subject: [FlyRotary] Spreadsheet for Prop Tip Speed =  PropTipSpeedCal.xls
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That spreadsheet is really cool!  I did not know about what affects = speed of sound (humidity, etc.), I thought it would be air density (altitude). Because of such arbitrary influences that can't be accounted for in a = formula, I would probably "red-line" the RPM at no more than 100 MPH = below speed of sound. Those influences could, at times, change the formula = speed of sound while you are flying, so that your prop RPM could enter the speed = of sound range just by chance of changing air properties.

In my sample formula, you can see what the difference in RPM can do. Add = 500 RPM, and it puts your prop tips a hair away from speed of sound.

Do you think a 100 MPH below speed of sound limit is reasonably safe? =

Thanks, Bernie

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