Return-Path: Received: from [24.25.9.101] (HELO ms-smtp-02-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.2.8) with ESMTP id 612048 for flyrotary@lancaironline.net; Tue, 18 Jan 2005 15:34:50 -0500 Received-SPF: none receiver=logan.com; client-ip=24.25.9.101; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-185-127.carolina.rr.com [24.74.185.127]) by ms-smtp-02-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id j0IKYI4S014115 for ; Tue, 18 Jan 2005 15:34:19 -0500 (EST) Message-ID: <007501c4fd9c$d509a0c0$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" Subject: turbine Exhaust??????? - No! not turbo related Date: Tue, 18 Jan 2005 15:32:30 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0072_01C4FD72.EC016530" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0072_01C4FD72.EC016530 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable As I mentioned in my first e mail concerning my trip to Florida, my left = EGT was running 125 F higher than normal and my rpm choked at 6000 with = a small amplitude irregular vibration present. =20 A bit of background for those who may have missed some of the episode. I inserted special configured discs in my two 2" diameter "muffler" = tubes and discovered that while they did a great job of suppressing the = nose, unfortunately it took only one 4 minute flight to clearly = demonstrate they suppressed power equally well. Could only get 5200 rpm = in the air. After realizing (doing the calculations) that 2" dia mufflers did not = provide sufficient airflow (with my discs inserted) I switched to a 3" = dia tube (after doing the math that showed the discs would have more = open area than my 2" tubes (that sans discs I have flow with for over = 100 hours). Well, I inserted 5 of these discs using a threaded 5/16" stainless steel = rod (with nuts) to clamp the discs to the rod and maintain the spacing = between the discs. I then inserted this set up into the 3" diameter = tubes and closed them up. I knew I had better exhaust flow immediately as the static rpm increased = to 5800 rpm. The noise suppression was not as good as the 2" tube but = considerably better than my open tubes. The open tubes (as Tracy later = reminded me) produced at least 125 dB of noise where as the new set up = produced only 104 dB at the same distance from the aircraft at WOT. So = some improvement. In anycase, it was time to head to Florida and no more time to mess with = them. So I launched for one quick trip around the pattern to make = certain I had good take off power and then landed to check everything = out. One of my hangar neighbors mentioned that at WOT just before = launch, he would have sworn that I had a turbine due to the turbine like = sound he heard. Well, I didn't think anything of it as you know we = sometime refer to our rotary as a "poor Mans turbine" So I loaded up = and I launched for Florida on Wednesday last week. Well, the launch was fine with 5800 rpm - however, several things became = clear once I leveled off. 1. My right exhaust EGT was 125F higher than it had ever been (normally = my max is 1600F), it was reading 1725F, The right one was a bit higher = as well but not nearly as much 2. While the exhaust flowed fine at 5800 rpm, the flow choked the engine = at 6000 rpm. Well, I can fly fine on 6000 so I proceeded on down to = Tracy's 3. Along the way I also notice a low amplitude rapid vibration which did = not to seem to be directly engine related (like gears), but did seem = correlated - I also notice my coolant temps were running around 10F = higher than normal compared to the oil temps. Got down to Tracy's just fine but decided to take the mufflers off and = see what was happening. 1. It turns out that 2-3 of the discs in the left and possibly 1 in the = right tubes had been rotating at high rpms. Despite the fact that each = discs had been clamped in position by "Jam" nuts on each side. 2. The tremendous speed of their rotation was evident by the wallowed = deformed bell shape of stainless steel metal around the hole in their = center (though which the stainless steel threaded rod had been = inserted). Also all thread had been eroded away from the rod where the = discs had rotated. In one case the stainless steel nut had a "flange" = added to it by the tremendous temperature and force. 3. Looking at the inside walls of the .065 3" dia 304 tubes you could = see where the tips of the discs had been contacting the walls. The tips = of the discs were burnished also testifying to that contact - = undoubtedly the source of the vibration I felt. 4. One of the discs had been shattered and various other indications of = violence inside the tubes. So the "turbine" sound my neighbor had heard were undoubtedly those = spinning discs, that of course was also responsible for the impeding the = exhaust flow (like several windmilling props), which in turn choked the = power at 6000 rpm and caused the EGT to increase. With Tracy's kind help, I stripped all but two discs from each rod = (making certain that we paired discs which would want to rotate in = opposite direction (hopefully stopping any - or most rotation). Then = Tracy welded the discs, nuts and rod together. I inserted that = arrangement back into the 3" tubes, closed them up and flew the rest of = the flight with that arrangement. The trip to Lakeland and home would seem to indicate I have found a = satisfactory (for now) solution. I hit 6000 rpm static on take off this = morning and got up to 6600 rpm straight and level (which is 200 rpm more = than I got with the straight (empty) 2" tubes. I intend to make one = more modification by placing a cross feed tube between the entrance to = the two mufflers, the old "H" pipe hook up which according to many = sources, assists in lowering noise and improving power. If indeed this bears out as it now looks then the only other thing I may = consider is using .035 3" dia tubing rather than the .065 tubing I had = available. The .065 tube exhaust each weighed 9 lbs making it 18 lbs = total, using the thinner tubing would approximately half that weight. All in all - I consider the experiment a modest success but will = undoubtedly continue to experiment with the exhaust system {:>)_ Best Regards Ed Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com ------=_NextPart_000_0072_01C4FD72.EC016530 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
As I mentioned in my first e mail = concerning my=20 trip to Florida, my left EGT was running 125 F higher than normal and my = rpm=20 choked at 6000 with a small amplitude irregular vibration present.  =
 
A bit of background for those who may = have missed=20 some of the episode.
 
I inserted special configured discs in = my two 2"=20 diameter "muffler" tubes and discovered that while they did a great job = of=20 suppressing the nose, unfortunately it took only one 4 minute flight to = clearly=20 demonstrate they suppressed power equally well.  Could only get = 5200 rpm in=20 the air.
 
After realizing (doing the = calculations) that=20 2" dia mufflers did not provide sufficient airflow (with my discs = inserted) I=20 switched to a 3" dia tube (after doing the math that showed the discs = would have=20 more open area than my 2" tubes (that sans discs I have flow with for = over 100=20 hours).
 
Well, I inserted 5 of these discs using = a threaded=20 5/16" stainless steel rod (with nuts) to clamp the discs to the rod and = maintain=20 the spacing between the discs.  I then inserted this set up into = the 3"=20 diameter tubes and closed them up.
 
I knew I had better exhaust flow = immediately as the=20 static rpm increased to 5800 rpm.  The noise suppression was not as = good as=20 the 2" tube but considerably better than my open tubes.  The open = tubes (as=20 Tracy later reminded me) produced at least 125 dB of noise where as the = new set=20 up produced only 104 dB at the same distance from the aircraft at = WOT.  So=20 some improvement.
 
In anycase, it was time to head to = Florida and no=20 more time to mess with them.  So I launched for one quick trip = around the=20 pattern to make certain I had good take off power and then landed to = check=20 everything out.  One of my hangar neighbors mentioned that at WOT = just=20 before launch, he would have sworn that I had a turbine due to the = turbine like=20 sound he heard.  Well, I didn't think anything of it as you know we = sometime refer to our rotary as a "poor Mans turbine"  So I loaded = up and I=20 launched for Florida on Wednesday last week.
Well, the launch was fine with 5800 rpm = - however,=20 several things became clear once I leveled off.
 
1.  My right exhaust EGT was 125F = higher than=20 it had ever been (normally my max is 1600F), it was reading 1725F,  = The=20 right one was a  bit higher as well but not nearly as = much
 
2. While the exhaust flowed fine at = 5800 rpm, the=20 flow choked the engine at 6000 rpm.  Well, I can fly fine on 6000 = so I=20 proceeded on down to Tracy's
 
3. Along the way I also notice a low = amplitude=20 rapid vibration which did not to seem to be directly engine related = (like=20 gears), but did seem correlated - I also notice my coolant temps were = running=20 around 10F higher than normal compared to the oil temps.
 
 
Got down to Tracy's just fine but = decided to take=20 the mufflers off and see what was happening.
 
1.  It turns out that 2-3 of the = discs in the=20 left and possibly 1 in the right tubes had been rotating at high rpms. = Despite=20 the fact that each discs had been clamped in position by "Jam" = nuts on=20 each side.
 
2.  The tremendous speed of their = rotation was=20 evident by the wallowed deformed bell shape of stainless steel metal = around the=20 hole in their center (though which the stainless steel threaded rod had = been=20 inserted).  Also all thread had been eroded away from the rod where = the=20 discs had rotated. In one case the stainless steel nut had a "flange" = added to=20 it by the tremendous temperature and force.
 
3.  Looking at the inside walls of = the .065 3"=20 dia 304 tubes you could see where the tips of the discs had been = contacting the=20 walls. The tips of the discs were burnished also testifying to that = contact -=20 undoubtedly the source of the vibration I felt.
 
4. One of the discs had been shattered = and various=20 other indications of violence inside the tubes.
 
So the "turbine" sound my neighbor had = heard were=20 undoubtedly those spinning discs, that of course was also responsible = for the=20 impeding the exhaust flow (like several windmilling props), which in = turn choked=20 the power at 6000 rpm and caused the EGT to increase.
 
With Tracy's kind help, I stripped all = but two=20 discs from each rod (making certain that we paired discs which would = want to=20 rotate in opposite direction (hopefully stopping any - or most = rotation). =20 Then Tracy welded the discs, nuts and rod together. I inserted that = arrangement=20 back into the 3" tubes, closed them up and flew the rest of the flight = with that=20 arrangement.
 
The trip to Lakeland and home would = seem to=20 indicate I have found a satisfactory (for now) solution.  I hit = 6000 rpm=20 static on take off this morning and got up to 6600 rpm straight and = level (which=20 is 200 rpm more than I got with the straight (empty) 2" tubes.  I = intend to=20 make one more modification by placing a cross feed tube between the = entrance to=20 the two mufflers, the old "H" pipe hook up which according to many = sources,=20 assists in lowering noise and improving power.
 
If indeed this bears out as it now = looks then the=20 only other thing I may consider is using .035 3" dia tubing rather than = the .065=20 tubing I had available.  The .065 tube exhaust each weighed 9 lbs = making it=20 18 lbs total, using the thinner tubing would approximately half that=20 weight.
 
All in all - I consider the = experiment a=20 modest success but will undoubtedly continue to experiment with the = exhaust=20 system {:>)_
 
Best Regards
 
Ed
 
 
Rv-6A N494BW Rotary = Powered
Matthews, NC
eanderson@carolina.rr.com
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