X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imo-d20.mx.aol.com ([205.188.139.136] verified) by logan.com (CommuniGate Pro SMTP 5.2.14) with ESMTP id 3749335 for flyrotary@lancaironline.net; Wed, 08 Jul 2009 11:48:21 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.188.139.136; envelope-from=WRJJRS@aol.com Received: from imo-da03.mx.aol.com (imo-da03.mx.aol.com [205.188.169.201]) by imo-d20.mx.aol.com (v107.10) with ESMTP id RELAYIN2-34a54bf8d14f; Wed, 08 Jul 2009 11:47:25 -0400 Received: from WRJJRS@aol.com by imo-da03.mx.aol.com (mail_out_v40_r1.5.) id q.c58.499b4b85 (37116) for ; Wed, 8 Jul 2009 11:47:18 -0400 (EDT) Received: from smtprly-ma01.mx.aol.com (smtprly-ma01.mx.aol.com [64.12.207.140]) by cia-ma01.mx.aol.com (v124.15) with ESMTP id MAILCIAMA012-5c494a54bf7e366; Wed, 08 Jul 2009 11:47:18 -0400 Received: from webmail-mx06 (webmail-mx06.sim.aol.com [64.12.137.16]) by smtprly-ma01.mx.aol.com (v124.15) with ESMTP id MAILSMTPRLYMA017-5c494a54bf7e366; Wed, 08 Jul 2009 11:47:10 -0400 References: To: flyrotary@lancaironline.net Subject: Re: [FlyRotary] Re: INJECTION OIL IN FUEL Date: Wed, 08 Jul 2009 11:47:10 -0400 X-AOL-IP: 205.188.169.201 In-Reply-To: X-MB-Message-Source: WebUI MIME-Version: 1.0 From: wrjjrs@aol.com X-MB-Message-Type: User Content-Type: multipart/alternative; boundary="--------MB_8CBCDFA7D857D06_13B4_2D0_webmail-mx06.sysops.aol.com" X-Mailer: AOL Webmail 43735-STANDARD Received: from 66.253.96.220 by webmail-mx06.sysops.aol.com (64.12.137.16) with HTTP (WebMailUI); Wed, 08 Jul 2009 11:47:10 -0400 Message-Id: <8CBCDFA7D49E20A-13B4-15F@webmail-mx06.sysops.aol.com> X-Spam-Flag:NO ----------MB_8CBCDFA7D857D06_13B4_2D0_webmail-mx06.sysops.aol.com Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii" Bernie, ?Your calculations are correct,but remember that the given figure for the SOS is in 0% humidity and standard air temp. With normal humidity levels and higher temps I've seen figures as low as 680 mph for the speed of sound. It would be wise to give yourself a bit more head room than 18 mph. Your prop efficiency just goes to s%&t if the tips go supersonic so giving it a wide berth is a good idea. ?Your belt question: Yes a belt thats twice as wide will generally carry twice the HP. The alignment of the sprockets ant the quality of the bearings to carry that load? are MUCH more critical. By the way if you are trying to use Gates toothed belts for a PSRU make sure you NEVER even SAY the word airplane. They will refuse sale to you. It is a company policy that they will not support sales to any aircraft system. Bill -----Original Message----- From: Berniehb7448@wmconnect.com To: Rotary motors in aircraft Sent: Tue, Jul 7, 2009 6:45 pm Subject: [FlyRotary] Re: INJECTION OIL IN FUEL This is what I figured out as my "formula": Max Prop RPM & Speed of Sound 1 Mile = 5,280 Feet Speed of Sound = ?768 mph (I think this is at sea level barometric pressure, I haven't figured out what happens with altitude.) pi = 3.1429 6 FT (72") D (Diameter) Prop CIRCUMFERENCE = ?pi X D = ??3.1429 ?X ?6 ft ?= 18.857 ft Circumference 1 RPM = 18.857 ft/Minute at prop tip With 2:1 PSRU Reduction, calculate by prop RPM and Circumference: Prop RPM 3,000 (Engine RPM 6,000) = ?56,571 ft/Minute = 10.714 miles/minute = 642.84 MPH (768 MPH - 642.84 MPH ?= 125.16 MPH under Speed of Sound) Prop RPM 3,500 (Engine RPM 7,000) = ?66,000 ft/Minute = 12.5 miles/minute = 750 MPH (768 MPH - 750 MPH ?= 18 MPH under Speed of Sound) ================================================ I paid enough attention in my math classes to think I've got it right. Here's one for you: Does a cogbelt PSRU's powerlimit increase with a wider belt? Like, for example, if a two incher can handle 150 HP, then you might need a four inch belt to handle 300 HP. Something like that? Here's another: One maker put an engine RPM limit on the PSRU, and I'm thinking it has to do with the capability of the bearing at the input end. Maybe because these bearings are sealed - they don't run in an oil bath. Thank you, Bernie. ----------MB_8CBCDFA7D857D06_13B4_2D0_webmail-mx06.sysops.aol.com Content-Transfer-Encoding: 7bit Content-Type: text/html; charset="us-ascii" Bernie,
 Your calculations are correct,but remember that the given figure for the SOS is in 0% humidity and standard air temp. With normal humidity levels and higher temps I've seen figures as low as 680 mph for the speed of sound. It would be wise to give yourself a bit more head room than 18 mph. Your prop efficiency just goes to s%&t if the tips go supersonic so giving it a wide berth is a good idea.
 Your belt question: Yes a belt thats twice as wide will generally carry twice the HP. The alignment of the sprockets ant the quality of the bearings to carry that load  are MUCH more critical. By the way if you are trying to use Gates toothed belts for a PSRU make sure you NEVER even SAY the word airplane. They will refuse sale to you. It is a company policy that they will not support sales to any aircraft system.
Bill


-----Original Message-----
From: Berniehb7448@wmconnect.com
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Tue, Jul 7, 2009 6:45 pm
Subject: [FlyRotary] Re: INJECTION OIL IN FUEL

This is what I figured out as my "formula":

Max Prop RPM & Speed of Sound

1 Mile = 5,280 Feet

Speed of Sound =  768 mph (I think this is at sea level barometric pressure, I haven't figured out what happens with altitude.)

pi = 3.1429

6 FT (72") D (Diameter) Prop

CIRCUMFERENCE =  pi X D =   3.1429  X  6 ft  = 18.857 ft Circumference

1 RPM = 18.857 ft/Minute at prop tip

With 2:1 PSRU Reduction, calculate by prop RPM and Circumference:
Prop RPM 3,000 (Engine RPM 6,000) =  56,571 ft/Minute = 10.714 miles/minute = 642.84 MPH
(768 MPH - 642.84 MPH  = 125.16 MPH under Speed of Sound)
Prop RPM 3,500 (Engine RPM 7,000) =  66,000 ft/Minute = 12.5 miles/minute = 750 MPH
(768 MPH - 750 MPH  = 18 MPH under Speed of Sound)
================================================
I paid enough attention in my math classes to think I've got it right.

Here's one for you: Does a cogbelt PSRU's powerlimit increase with a wider belt? Like, for example, if a two incher can handle 150 HP, then you might need a four inch belt to handle 300 HP. Something like that?
Here's another: One maker put an engine RPM limit on the PSRU, and I'm thinking it has to do with the capability of the bearing at the input end. Maybe because these bearings are sealed - they don't run in an oil bath.
Thank you, Bernie.
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