Return-Path: Received: from mail.viclink.com ([66.129.220.6] verified) by logan.com (CommuniGate Pro SMTP 4.2.5) with ESMTP id 567063 for flyrotary@lancaironline.net; Tue, 14 Dec 2004 09:37:06 -0500 Received-SPF: none receiver=logan.com; client-ip=66.129.220.6; envelope-from=pjmick@viclink.com Received: from viclink.com (p019.AS1.viclink.com [66.129.192.19]) by mail.viclink.com (8.11.7/8.11.7) with ESMTP id iBEEaK678882 for ; Tue, 14 Dec 2004 06:36:20 -0800 (PST) Message-ID: <41BEF9ED.40607@viclink.com> Date: Tue, 14 Dec 2004 06:34:22 -0800 From: Perry Mick User-Agent: Mozilla/5.0 (Windows; U; Win98; en-US; rv:1.0.1) Gecko/20020823 Netscape/7.0 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: Dynamic balance References: Content-Type: multipart/alternative; boundary="------------080603070300000605050609" --------------080603070300000605050609 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit 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 >> >> --------------080603070300000605050609 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit 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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