X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from an-out-0708.google.com ([209.85.132.249] verified) by logan.com (CommuniGate Pro SMTP 5.2.3) with ESMTP id 2978739 for flyrotary@lancaironline.net; Sat, 21 Jun 2008 21:40:31 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.132.249; envelope-from=wdleonard@gmail.com Received: by an-out-0708.google.com with SMTP id b38so395216ana.81 for ; Sat, 21 Jun 2008 18:39:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to :subject:in-reply-to:mime-version:content-type:references; bh=u95CGKNU0po+x7N/RHqkSaZbLYKFnqciSzL1Mds1jJI=; b=OksXkyyyerD4zWuf/SsZHDJUhskSpN/6kRfpjgwCnmY3H0AyQWGIUmXR4Y4/cYmDLs f7Ha6INoPzARtsoqYRAFRnpR5jva1ZpuAtqvud4vrzORdx4vl7zaR7cIwSwscJBTtuKB Y1WV9yY+pAsJzEvvHmc/p8NbYwN1OMNW+HQ98= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:in-reply-to:mime-version :content-type:references; b=BpiMHXUaJzf0hvhLZUSHQSB3beiY36TfGj+EuzbnmYIXpPY5IQsvqeYC7yJAMMn57z eAZQk3V1IuO9P5s5OYnooJOV5fyzThwhkQcIMdiTciL5bVXBfJzD/s9cY+c3/nUg6qhe IsrNr4zAaeEzeB/dtDSl+dyFKB/hXcHeh8qXI= Received: by 10.100.226.6 with SMTP id y6mr9410547ang.115.1214098791111; Sat, 21 Jun 2008 18:39:51 -0700 (PDT) Received: by 10.150.145.16 with HTTP; Sat, 21 Jun 2008 18:39:51 -0700 (PDT) Message-ID: <1c23473f0806211839l1af9d8a4m9924d59a703fc68d@mail.gmail.com> Date: Sat, 21 Jun 2008 18:39:51 -0700 From: "David Leonard" To: "Rotary motors in aircraft" Subject: Re: [FlyRotary] Re: Another Turbo Bites the dust In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_1974_24721586.1214098791070" References: ------=_Part_1974_24721586.1214098791070 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Good point about the oil feed Ed. In fact, when my first turbo went, the folks on the ground saw all that smoke and reported that we were on fire... we were not on fire, but there was plenty of oil both inside the exhaust on spilling onto the outside of it. So after that I installed an electric switch that I can use to cutoff oil flow to the turbo from inside the cockpit. Interesting, with this failure there was no smoke or oil leakage (yet), but I will flip the switch for the flight home and cut off the oil supply. Thanks for the reminder! --=20 David Leonard Turbo Rotary RV-6 N4VY http://N4VY.RotaryRoster.net http://RotaryRoster.net On Sat, Jun 21, 2008 at 4:58 PM, Ed Anderson wrote: > In my opinion, one of the things that we tend to not pay sufficient > attention to is the extent of the demand we are putting on turbos. Witho= ut > getting into the specifics of boost ratios vs ambient pressure, suffice i= t > to say that a turbo compressor has to work considerably harder at altitud= e > to maintain the same pressure ratio in the manifold. > > > > The ambient air pressure is of course less at 8000 MSL therefore densit= y > less as well and the turbo simply has to turn faster to create the same > amount of boost pressure out of the less dense air. The only way the tur= bo > can do that is to turn faster at altitude. So you have that hot rotary > exhaust pushing those small turbine blades, faster and faster. > > > > As we have discovered, the stock RX-7 turbo succumbs quickly to those > stresses (simply not designed for them). Even with the TO4 compressor mo= d, > which clearly helps by reducing the turbine rpm needed to produce X boost= , > the stock turbine and bearing just do not appear up to the stress for lon= g > duration =96 although 130 hours is better than I thought the stock bearin= gs > would do. > > > > > > A precaution I would take before flying back with the turbo that conditio= n > is to disconnect and plug the oil line to the turbo. Should the bearing > have taken a worst beating 0r continues to deteriorate, you would not wan= t > to be dumping that precious engine oil into the exhaust =96 although ther= e > should be plenty of smoke to tell you when that condition occurred =96 if > there is anybody around in West Texas to let you know {:>). So I would > disconnect and plug the oil line and coolant line to the turbo =96 just t= o > make certain no leaks occurred. > > > > Just my 0.02. Glad, nothing more happened to the engine or you, Dave. > > > > > > Ed. > > > > > > > > Ed Anderson > > Rv-6A N494BW Rotary Powered > > Matthews, NC > > eanderson@carolina.rr.com > > http://www.andersonee.com > > http://members.cox.net/rogersda/rotary/configs.htm#N494BW > > http://www.dmack.net/mazda/index.html > ------------------------------ > > *From:* Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] *O= n > Behalf Of *George Lendich > *Sent:* Saturday, June 21, 2008 6:24 PM > *To:* Rotary motors in aircraft > *Subject:* [FlyRotary] Re: Another Turbo Bites the dust > > > > > > It's amazing how fast 130 hrs goes when you are having fun.:-) > > I took off the exhaust today and too a look. One of the blades on the > turbine wheel is gone, but the axle seems otherwise intact, though it may= be > off kilter and that is what is causing the resistance when I try to turn > it. So I am to sure if the problem was primarily the bearing, or overhea= t, > or overspeed. According to my calculations, turbine speed should have be= en > well within the green area. (way down around 60k RPM - near the bottom of > the chart.) > > One difference with this fligh... I usually run well lean of peak, but > this particular leg I was running a little late so I decided to push it u= p a > bit by running a best power setting. I figured I was OK because I was hi= gh > enough that I was only showing 21" MAP. But the failure happened in desc= ent > when I kept best power as I came lower and the engine RPM came up to abou= t > 6300 (more exhaust available). > > Combination of higher than normal EGT's and 'you number is up, turbo'??? > > Dave Leonard > > Dave, > > I follow your threads carefully as you have put so much into the Turbo > installation, I don't know anyone who has done more but I'm sure there ar= e, > it's just we/I am not aware of them. From what your saying, I think your > right on the money - heat is the killer (in this case). > > > > I personally would like you to try something remote as per suggestions by > others. I think Paul's idea is sound, but may be still to close to the he= at > for my liking. > > George (down under) > > > > > > __________ Information from ESET NOD32 Antivirus, version of virus > signature database 3206 (20080621) __________ > > The message was checked by ESET NOD32 Antivirus. > > http://www.eset.com > ------=_Part_1974_24721586.1214098791070 Content-Type: text/html; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Good point about the oil feed Ed. In fact, when my first turbo went, the fo= lks on the ground saw all that smoke and reported that we were on fire... w= e were not on fire, but there was plenty of oil both inside the exhaust on = spilling onto the outside of it. 

So after that I installed an electric switch that I can use to cutoff o= il flow to the turbo from inside the cockpit.   Interesting, with= this failure there was no smoke or oil leakage (yet), but I will flip the = switch for the flight home and cut off the oil supply.

Thanks for the reminder!

--
David Leonard

Turbo Rotar= y RV-6 N4VY
http://N4VY.RotaryR= oster.net
http://RotaryRoster.ne= t

On Sat, Jun 21, 2008 at 4:58 PM, Ed Anderson= <eanderson@carolina.rr.com= > wrote:

In my opinion, one of the things t= hat we tend to not pay sufficient attention to is the extent of the demand we are putting on turbos.  Without getting into the specifics of boost ratios= vs ambient pressure, suffice it to say that a turbo compressor has to work considerably harder at altitude to maintain the same pressure ratio in the manifold.

 

  The ambient air pressure is= of course less at 8000 MSL therefore density less as well and the turbo simply= has to turn faster to create the same amount of boost pressure out of the less dense air.  The only way the turbo can do that is to turn faster at altitude.  So you have that hot rotary exhaust pushing those small tur= bine blades, faster and faster.

 

  As we have discovered, the = stock RX-7 turbo succumbs quickly to those stresses (simply not designed for them= ).  Even with the TO4 compressor mod, which clearly helps by reducing the turbi= ne rpm needed to produce X boost, the stock turbine and bearing just do not ap= pear up to the stress for long duration =96 although 130 hours is better than I thought the stock bearings would do.

 

 

A precaution I would take before f= lying back with the turbo that condition is to disconnect and plug the oil line t= o the turbo.  Should the bearing have taken a worst beating 0r continues= to deteriorate, you would not want to be dumping that precious engine oil into= the exhaust =96 although there should be plenty of smoke to tell you when that condition occurred =96 if there is anybody around in West Texas to let you know {:>).  So I would disconnect and plug the oil line and coolant line to the turbo =96 just to make certain no leaks occurred. 

 

Just my 0.02.  Glad, nothing = more happened to the engine or you, Dave. 

 

 

Ed.

 

 

 

From: Ro= tary motors in aircraft [mailto:fl= yrotary@lancaironline.net] On Behalf Of George Lendich
Sent: Saturday, June 21, 2= 008 6:24 PM


To: Rotary motors in aircraft
Subject: [FlyRotary]= Re: Another Turbo Bites the dust

 

 

It's amazing how fast 130 hrs goes when you are having fun.:-) =

I took off the exhaust today and too a look.  One of the blades on the turbine wheel is gone, but the axle seems otherwise intact, though it may b= e off kilter and that is what is causing the resistance when I try to turn it.  So I am to sure if the problem was primarily the bearing, or overheat, or overspeed.  According to my calculations, turbine speed should have been well within the green area. (way down around 60k RPM - nea= r the bottom of the chart.)

One difference with this fligh...  I usually run well lean of peak, bu= t this particular leg I was running a little late so I decided to push it up = a bit by running a best power setting.  I figured I was OK because I was high enough that I was only showing 21" MAP.  But the failure happened in descent when I kept best power as I came lower and the engine R= PM came up to about 6300 (more exhaust available).

Combination of higher than normal EGT's and 'you number is up, turb= o'???

Dave Leonard

Dave,

I follow your threads carefully as you have put so much into the Turbo installation, I don't know anyone who has done more but I'= ;m sure there are, it's just we/I am not aware of them. From what your saying, = I think your right on the money - heat is the killer (in this case).

 

I personally would like you to try something remote as per suggestions by others. I think Paul's idea is sound, but may be still t= o close to the heat for my liking.

George (down under)

 



__________ Information from ESET NOD32 Antivirus, version of virus signatur= e database 3206 (20080621) __________

The message was checked by ESET NOD32 Antivirus.

http://www.eset.com



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