X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [206.46.252.44] (HELO vms044pub.verizon.net) by logan.com (CommuniGate Pro SMTP 4.3c5) with ESMTP id 944798 for flyrotary@lancaironline.net; Sun, 15 May 2005 13:11:05 -0400 Received: from verizon.net ([71.99.145.54]) by vms044.mailsrvcs.net (Sun Java System Messaging Server 6.2 HotFix 0.04 (built Dec 24 2004)) with ESMTPA id <0IGJ007D0JQC1WOG@vms044.mailsrvcs.net> for flyrotary@lancaironline.net; Sun, 15 May 2005 12:11:01 -0500 (CDT) Date: Sun, 15 May 2005 13:10:57 -0400 From: Finn Lassen Subject: Re: [FlyRotary] Re: Prop balancing? In-reply-to: To: Rotary motors in aircraft Message-id: <428782A1.9090000@verizon.net> MIME-version: 1.0 Content-type: multipart/alternative; boundary=------------000808070903030300000301 X-Accept-Language: en-us, en References: User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.4) Gecko/20030624 Netscape/7.1 (ax; PROMO) This is a multi-part message in MIME format. --------------000808070903030300000301 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Cheap man's way: I'm sure you have access to an oscilloscope. Mount a position pickup (for prop) and connect to trigger input. Get an accelerometer (http://www.analog.com/en/prod/0,2877,ADXL105,00.html, or similar - I bought mine from Newark many yers ago) and hook up to Y-input. Mount on tip of PSRU (or remove PSRU and mount on engine to check its balance). You'll need some filtering circuit like a tunable notch filter. Actually doen't have to be tunable - adjust RPM to hit the notch. I tried it with only the accelerometer and no filtering circuit and couldn't read through it. Actually not sure if the G range doesn't have to be bigger, like 20 Gs - seem to remember signal being clipped with the 5-G sensor. Some of our physists on the list can undoubtledly answer that. Finn Russell Duffy wrote: > I'm not familiar with the Chadwick unit, but it probably operates on > the same principle using a vibration sensor on the engine and an > optical sensor to pick up reflective tape on one prop blade. No reason > it shouldn't work. > > > Thanks for the info Perry. The Chadwick was just as you describe, > a vibration/optical sensor that mounted to the redrive plate, and a > piece of tape on the prop. The guy who was running it admitted that > it was probably something he just didn't know how to set. The unit > actually belongs to his son, but he's working two jobs, and I never > see him anymore. > > At least it's good to know that it should probably work. > > BTW, does anyone have any idea how much these things cost? I assume > "a lot". > > Cheers, > Rusty > > > --------------000808070903030300000301 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit Cheap man's way:
I'm sure you have access to an oscilloscope.

Mount a position pickup (for prop) and connect to trigger input.

Get an accelerometer (http://www.analog.com/en/prod/0,2877,ADXL105,00.html, or similar - I bought mine from Newark many yers ago) and hook up to Y-input. Mount on tip of PSRU (or remove PSRU and mount on engine to check its balance).

You'll need some filtering circuit like a tunable notch filter. Actually doen't have to be tunable - adjust RPM to hit the notch.

I tried it with only the accelerometer and no filtering circuit and couldn't read through it. Actually not sure if the G range doesn't have to be bigger, like 20 Gs - seem to remember signal being clipped with the 5-G sensor. Some of our physists on the list can undoubtledly answer that.

Finn

Russell Duffy wrote:
Message
I'm not familiar with the Chadwick unit, but it probably operates on the same principle using a vibration sensor on the engine and an optical sensor to pick up reflective tape on one prop blade. No reason it shouldn't work.

 
Thanks for the info Perry.  The Chadwick was just as you describe,  a vibration/optical sensor that mounted to the redrive plate, and a piece of tape on the prop.  The guy who was running it admitted that it was probably something he just didn't know how to set.  The unit actually belongs to his son, but he's working two jobs, and I never see him anymore.  
 
At least it's good to know that it should probably work.  
 
BTW, does anyone have any idea how much these things cost?  I assume "a lot". 
 
Cheers,
Rusty
 
 
  
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