Return-Path: Received: from out006.verizon.net ([206.46.170.106] verified) by logan.com (CommuniGate Pro SMTP 4.2.5) with ESMTP id 567335 for flyrotary@lancaironline.net; Tue, 14 Dec 2004 13:03:53 -0500 Received-SPF: pass receiver=logan.com; client-ip=206.46.170.106; envelope-from=rotary.coot@verizon.net Received: from [67.227.200.74] ([65.239.43.12]) by out006.verizon.net (InterMail vM.5.01.06.06 201-253-122-130-106-20030910) with ESMTP id <20041214180324.BJQY7873.out006.verizon.net@[67.227.200.74]> for ; Tue, 14 Dec 2004 12:03:24 -0600 Mime-Version: 1.0 X-Sender: res0c5l1@incoming.verizon.net Message-Id: In-Reply-To: References: Date: Tue, 14 Dec 2004 10:07:53 -0800 To: "Rotary motors in aircraft" From: Ken Welter Subject: [FlyRotary] Re: Dynamic balance Content-Type: multipart/alternative; boundary="============_-1109074773==_ma============" X-Authentication-Info: Submitted using SMTP AUTH at out006.verizon.net from [65.239.43.12] at Tue, 14 Dec 2004 12:03:22 -0600 --============_-1109074773==_ma============ Content-Type: text/plain; charset="us-ascii" ; format="flowed" I think your right that the redrive damper is giving false readings, Ideal would be to spin the prop on an electric motor, what rpm do you need to balance it ?? Ken >I did that too way back when. I was told I need to run it's output >through a spectrum analyzer. Audio frequencies so an audio spectrum >analyzer would work. You could input to the audio card in a PC and >use a PC audio spectrum analyzer. >The balancer has an optical sensor that picks up from a reflective >piece of tape placed on one blade, to use as a zero reference for >blade position and determine RPM. > >Finn Lassen wrote: > >>Early on I hooked up an accelometer to an oscilloscope. It sure was >>a mess - very hard to discern any fundamental frequency. My >>conclusiion was that I needed a prop pickup to trigger the scope >>and perhaps a notch filter so I would only be looking at the >>fundamental frequency of the prop. I never did get back and try it. >> >>Finn >> >>Perry Mick wrote: >> >>> >>>I've used the balancer many times before with no problem on >>>direct-drive. I think it's getting confused by harmonics or beat >>>frequencies between the engine and redrive. For a first step it >>>usually asks for 20-30 grams at a certain radial position, the >>>fender washer is about right. This is on the prop bolt circle >>>(4.75 inches?), not out at spinner diameters. It will just be >>>moved around the six locations temporarily to see if the vibration >>>gets worse or better. >>> >>>Perry --============_-1109074773==_ma============ Content-Type: text/html; charset="us-ascii" [FlyRotary] Re: Dynamic balance
  I think your right that the redrive damper is giving false readings, Ideal would be to spin the prop on an electric motor, what rpm do you need to balance it ??
  Ken





I did that too way back when. I was told I need to run it's output through a spectrum analyzer. Audio frequencies so an audio spectrum analyzer would work. You could input to the audio card in a PC and use a PC audio spectrum analyzer.
The balancer has an optical sensor that picks up from a reflective piece of tape placed on one blade, to use as a zero reference for blade position and determine RPM.

Finn Lassen wrote:
Early on I hooked up an accelometer to an oscilloscope. It sure was a mess - very hard to discern any fundamental frequency. My conclusiion was that I needed a prop pickup to trigger the scope and perhaps a notch filter so I would only be looking at the fundamental frequency of the prop. I never did get back and try it.

Finn

Perry Mick wrote:

I've used the balancer many times before with no problem on direct-drive. I think it's getting confused by harmonics or beat frequencies between the engine and redrive. For a first step it usually asks for 20-30 grams at a certain radial position, the fender washer is about right. This is on the prop bolt circle (4.75 inches?), not out at spinner diameters. It will just be moved around the six locations temporarily to see if the vibration gets worse or better.

Perry

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