X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from rwcrmhc12.comcast.net ([216.148.227.85] verified) by logan.com (CommuniGate Pro SMTP 4.3.4) with ESMTP id 1009095 for flyrotary@lancaironline.net; Tue, 21 Jun 2005 13:38:37 -0400 Received-SPF: none receiver=logan.com; client-ip=216.148.227.85; envelope-from=n3773@comcast.net Received: from rv8 (c-24-21-140-241.hsd1.or.comcast.net[24.21.140.241]) by comcast.net (rwcrmhc12) with SMTP id <2005062117374201400ag72ve>; Tue, 21 Jun 2005 17:37:42 +0000 Message-ID: <003f01c57688$17ab9dc0$f18c1518@rv8> Reply-To: "kevin lane" From: "kevin lane" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Prop balancing Date: Tue, 21 Jun 2005 10:37:52 -0700 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0038_01C5764D.46E50260" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 This is a multi-part message in MIME format. ------=_NextPart_000_0038_01C5764D.46E50260 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Messageyou can join the RV Homewing, now chapter 105, and use their = $4000 balancer for free. guess that doesn't help all you southerners = though. Kevin Lane Portland, OR e-mail-> n3773@comcast.net ----- Original Message -----=20 From: Russell Duffy=20 To: Rotary motors in aircraft=20 Sent: Tuesday, June 21, 2005 9:59 AM Subject: [FlyRotary] Re: Prop balancing What G-force and frequency range are we talking about?=20 See attached chart of acceleration limits. =20 Do you find an RPM of high amplitude and work there.=20 The manual suggests a low cruise setting for the rpm. I'm not sure it = matters much, but you need to reproduce the same rpm from one run to the = next for best results. =20 What sort of weights do you put on the prop?=20 None. You put the permanent weights on the spinner back plate, but = the temporary weights generally go under the spinner attachment screws = on the outside of the spinner. On Lycomings, you can put them on the = flywheel, since there are already holes every 30 degrees. =20 =20 I assume placement is amount is trial and error.=20 Yep, no equipment required :-) Kidding. =20 Does this approach work on a three-blade?=20 Absolutely. Any info on how this is done appreciated=20 Using the professional equipment, it's pretty easy. Basically, you = set up one vibration sensor, vertical, as close to the prop hub as you = can get (I've got a bracket that clamps to the nose of the redrive). = You also set up an optical tach, with a piece of reflective tape on one = blade. Pick an rpm, and the analyzer tells you what the peak = acceleration reading is, and how many degrees from the tape mark it = occurred at. It then suggests a temporary weight that should be = attached, and tells you what position to install it. If you think about this, you will realize that the distance the sensor = is from the prop, and the distance the weight is from the center of the = prop hub both make a difference on how much weight is required. The = program doesn't know any of these variables up front, and doesn't care. = It initially picks a weight that it knows will make a measurable change, = then you install it, and re-run the test. From the change that was = made, using a known weight, the program can now calculate what the real = weight should be to make the change required. Each time, the old = weights are removed, and the new weight is installed where the program = suggests The program will continue to work well, even if you don't do exactly = what it says, as long as you are honest, and tell the program what you = really did. For example, if it says put 15 grams at 355 degrees, and = you have a spinner hole at 360, then put 15 grams at 360, and enter that = for the actual weight in the program. If you have a hole at 30 and 60 = degrees, and it wants weight at 39 degrees, you can tell it to split the = weight, and give it the two locations you have available. It will then = tell you how much weight to put in each location to make the equivalent = weight. Pretty handy. =20 When you get to .06 ips or less, you have to convert the temporary = weights to permanent ones. For that, you measure the radius the = temporary weights are located, and the radius you want to install the = permanent weights, and the program will tell you how much to adjust the = weights for the new location. =20 Or maybe Rusty has purchased the professional equipment by now and = wants to rent it out J.=20 We have vibration analyzers similar to this for measuring site = environmental qualifications for MRI scanners, and it takes just a few = trips on the FedEx plane to convert a new piece of equipment to junk. = In other words, there will be no renting, or shipping of equipment, but = I can certainly offer a reasonably priced balance job if you bring your = airplane to 2R4. Send all your experimental Lycoming friends too, since = those are simple :-) Cheers, Rusty (fighting Al's font for control) -------------------------------------------------------------------------= ----- >> Homepage: http://www.flyrotary.com/ >> Archive: http://lancaironline.net/lists/flyrotary/List.html ------=_NextPart_000_0038_01C5764D.46E50260 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message
you can join the RV Homewing, = now chapter=20 105, and use their $4000 balancer for free. guess that doesn't help = all you=20 southerners though.
Kevin Lane  Portland, OR
e-mail-> n3773@comcast.net
----- Original Message -----
From:=20 Russell=20 Duffy
Sent: Tuesday, June 21, 2005 = 9:59=20 AM
Subject: [FlyRotary] Re: Prop=20 balancing

What G-force and = frequency range=20 are we talking about? 
 
See attached chart of acceleration = limits. =20
 
Do you find an RPM of = high=20 amplitude and work there. 
 
The manual suggests a low cruise setting = for the=20 rpm.  I'm not sure it matters much, but you need to reproduce the = same=20 rpm from one run to the next for best results. =20
 
What sort of weights = do you put=20 on the prop? 
 
None.  You put the permanent weights on the spinner = back=20 plate, but the temporary weights generally go under the spinner = attachment=20 screws on the outside of the spinner.  On Lycomings, you = can put=20 them on the flywheel, since there are already holes every 30=20 degrees.    
   
I assume placement is = amount is=20 trial and error. 
 
Yep, no=20 equipment required :-)  = Kidding.
   
Does this approach = work on a=20 three-blade? 
 
Absolutely.
 
Any info on how this = is done=20 appreciated 
 
Using the=20 professional equipment, it's pretty easy.  Basically, = you set=20 up one vibration sensor, vertical, as close to the prop hub = as you=20 can get (I've got a bracket that clamps to the nose of the = redrive).  You=20 also set up an optical tach, with a piece of reflective tape on one=20 blade.  Pick an rpm, and the analyzer tells you what = the peak=20 acceleration reading is, and how many degrees from the tape mark = it=20 occurred at.  It then suggests a temporary weight that should be=20 attached, and tells you what position to install=20 it.
 
If you think=20 about this, you will realize that the distance the sensor is from = the=20 prop, and the distance the weight is from the center of the = prop hub=20 both make a difference on how much weight is required.  The=20 program doesn't know any of these variables up front, and doesn't = care.  It initially picks a weight that it knows will make a = measurable change, then you install it, and re-run the = test.   From=20 the change that was made, using a known weight, the program can=20 now calculate what the real  weight should be to make the = change=20 required.  Each time, the old weights are removed, and the = new=20 weight is installed where the program=20 suggests
 
The program=20 will continue to work well, even if you don't do exactly what it says, = as long=20 as you are honest, and tell the program what you really did.  For = example, if it says put 15 grams at 355 degrees, and you have a = spinner hole=20 at 360, then put 15 grams at 360, and enter that for the actual weight = in the=20 program.  If you have a hole at 30 and 60 degrees, and it=20 wants weight at 39 degrees, you can tell it to split the = weight, and=20 give it the two locations you have available.  It will then tell = you how=20 much weight to put in each location to make the equivalent = weight. =20 Pretty handy.  
 
When you get to=20 .06 ips or less, you have to convert the temporary weights to = permanent=20 ones.  For that, you measure the radius the = temporary=20 weights are located, and the radius you want to install the permanent = weights,=20 and the program will tell you how much to adjust the weights for = the new=20 location.    
 
 =20 Or maybe Rusty has = purchased the=20 professional equipment by now and wants to rent it out = J. 
 
 We have=20 vibration analyzers similar to this for measuring site environmental=20 qualifications for MRI scanners, and it takes just a few trips on = the=20 FedEx plane to convert a new piece of equipment to junk.   = In other=20 words, there will be=20 no renting, or shipping of equipment, but I can certainly offer a = reasonably=20 priced balance job if you bring your airplane to 2R4.  Send all = your=20 experimental Lycoming friends too, since those are=20 simple :-)
 
Cheers,
Rusty (fighting=20 Al's font for = control)
 
 

 

 

 

 

>>  Homepage: =20 http://www.flyrotary.com/
>>  Archive:  =20 = http://lancaironline.net/lists/flyrotary/List.html
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