Return-Path: Received: from mail.viclink.com ([66.129.220.6] verified) by logan.com (CommuniGate Pro SMTP 4.2.5) with ESMTP id 566751 for flyrotary@lancaironline.net; Tue, 14 Dec 2004 01:03:49 -0500 Received-SPF: none receiver=logan.com; client-ip=66.129.220.6; envelope-from=pjmick@viclink.com Received: from viclink.com (p089.AS1.viclink.com [66.129.192.89]) by mail.viclink.com (8.11.7/8.11.7) with ESMTP id iBE634362342 for ; Mon, 13 Dec 2004 22:03:04 -0800 (PST) Message-ID: <41BE81A2.4030405@viclink.com> Date: Mon, 13 Dec 2004 22:01:06 -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: Dynamic balance References: Content-Type: multipart/alternative; boundary="------------090404070102000907030203" --------------090404070102000907030203 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit > > > > > >>"Perry Mick" wrote: >> >>""" >>I've tried 4 times now to use a computerized dynamic balance >> system, but it won't converge on a solution. It always worked perfectly >> >> >with > > >> my direct-drive fan. So it mustn't like geared engines. I'm going to >> >> >trial- > > >> and-error it by moving a fender washer (weight) from one prop bolt to >> >> >the > > >> next and see if the vibration level readout increases or decreases, and >> >> >try > > >> to find a minimum. >>""" >> >>I'm curious, Perry, if a fender washer might not be overkill... last guy >> >> >I > > >>saw had a prop dynamically balanced it took a short #6 screw to get the >> >> >job > > >>done. Given the size of prop bolts and their associated fender washer >> >> >size, > > >>aren't you concerned that will be _too much_ mass? I'd think that much >> >> >weight > > >>fladdling around off-center out there at 2000+ rpm would make matters >> >> >worse, > > >>not better. Like I said, just curious (and concerned). >> >> >> >My experience with these electronic balancers is: >a) if you can't get a consistent reading, something is out of spec, a loose >engine mount, worn bearing, off-center mounted/drilled/bored prop >b) balancer out of calibration > >c) Generally it takes me about 5 runs to go from an initial run down to >about 0.02 to 0.05 IPS, if it takes more runs and values continue to jump >around "the clock", something is not right, a or b. > >My 5cents, > >Thomas J. > > > 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 --------------090404070102000907030203 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit 

  
"Perry Mick" <pjmick@mail.viclink.com> wrote:

"""
I've tried 4 times now to use a computerized dynamic balance
  system, but it won't converge on a solution. It always worked perfectly
    
with
  
  my direct-drive fan. So it mustn't like geared engines. I'm going to
    
trial-
  
  and-error it by moving a fender washer (weight) from one prop bolt to
    
the
  
  next and see if the vibration level readout increases or decreases, and
    
try
  
  to find a minimum.
"""

I'm curious, Perry, if a fender washer might not be overkill...  last guy
    
I
  
saw had a prop dynamically balanced it took a short #6 screw to get the
    
job
  
done.  Given the size of prop bolts and their associated fender washer
    
size,
  
aren't you concerned that will be _too much_ mass?  I'd think that much
    
weight
  
fladdling around off-center out there at 2000+ rpm would make matters
    
worse,
  
not better.  Like I said, just curious (and concerned).

    
My experience with these electronic balancers is:
a) if you can't get a consistent reading, something is out of spec, a loose
engine mount, worn bearing, off-center mounted/drilled/bored prop
b) balancer out of calibration

c) Generally it takes me about 5 runs to go from an initial run down to
about 0.02 to 0.05 IPS, if it takes more runs and values continue to jump
around "the clock", something is not right, a or b.

My 5cents,

Thomas J.

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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