Return-Path: Received: from imf16aec.mail.bellsouth.net ([205.152.59.64] verified) by logan.com (CommuniGate Pro SMTP 4.2b7) with ESMTP id 310786 for flyrotary@lancaironline.net; Sat, 10 Jul 2004 18:13:06 -0400 Received: from [68.223.130.10] by imf16aec.mail.bellsouth.net (InterMail vM.5.01.06.08 201-253-122-130-108-20031117) with ESMTP id <20040710221237.PJOJ1705.imf16aec.mail.bellsouth.net@[68.223.130.10]> for ; Sat, 10 Jul 2004 18:12:37 -0400 User-Agent: Microsoft-Entourage/10.1.4.030702.0 Date: Sat, 10 Jul 2004 18:12:20 -0400 Subject: Re: [FlyRotary] Re: Three candidates for Turbo Failure From: Bulent Aliev To: Rotary motors in aircraft Message-ID: In-Reply-To: Mime-version: 1.0 Content-type: multipart/alternative; boundary="B_3172327943_51801521" > This message is in MIME format. Since your mail reader does not understand this format, some or all of this message may not be legible. --B_3172327943_51801521 Content-type: text/plain; charset="ISO-8859-1" Content-transfer-encoding: quoted-printable Both of John=B9s turbos were =B3Junkyard direct=B2 . Mine was also and I noticed considerable play while pushing up and down on the wheel. I=B9m sure at very high RPM the wheels get in some harmonic vibrations and it is matter of tim= e before they snap at the root. Just imagine your Dremmel tool at high RPM with the cutting wheel able to play in the chuck? I rebuilt my turbo and there is no end play at the wheels. Bulent >> > ... >> > ... It's the turbine wheel that failed, not the compressor wheel. On >> > each occasion the weld broke right at the base of the turbine wheel, t= he >> > wheel came off and blocked the exhaust outlet. >=20 > The *weld* broke? Does that mean that the shaft is > still intact? =20 >=20 > Someone else mentioned the term "friction weld"; I'm not > familiar with it. This is something different than > "interference fit"? >=20 > Gotta wonder what kind of stresses would cause that weld > to break. Is the shaft keyed? Maybe it should be - although > that would complicate balancing it. Perhaps balancing is > part of the problem. Maybe at umpteen thousand rpm, +/- .5 > gram isn't close enough. >=20 > Two senarios come to mind: (1) Turbine wheel heats up > faster than the shaft; develops a small amount of clearance > at the end opposite the weld; starts wobbling a little, too > much for the weld to absorb; (2) Turbine gets a little > wobbly at high speed; after sustained high speed operation, > the vibration overcomes the weld. >=20 > I don't quite understand why the only thing holding that > turbine wheel on the shaft is a *weld*. Isn't the turbine > Iconel or similar? Is the shaft also Iconel? If it isn't, the joint is > closer to being a brazing (in principle, > anyway). >=20 > My somewhat semi-random thoughts ... >=20 > Dale R. > COZY MkIV-R13B-NA #1254 >=20 --B_3172327943_51801521 Content-type: text/html; charset="ISO-8859-1" Content-transfer-encoding: quoted-printable Re: [FlyRotary] Re: Three candidates for Turbo Failure Both of John’s tu= rbos were “Junkyard direct” . Mine was also and I noticed consid= erable play while pushing up and down on the wheel. I’m sure at very h= igh RPM the wheels get in some harmonic vibrations and it is matter of time = before they snap at the root. Just imagine your Dremmel tool at high RPM wit= h the cutting wheel able to play in the chuck? I rebuilt my turbo and there = is no end play at the wheels.
Bulent

> ...
> ... It's the turbine wheel that failed, not the compressor wheel. On > each occasion the weld broke right at the base of the turbine wheel, t= he
> wheel came off and blocked the exhaust outlet.

   The *weld* broke?  Does that mean that the shaft is =
still intact?  

   Someone else mentioned the term "friction weld"= ; I'm not
familiar with it.  This is something different than
"interference fit"?

   Gotta wonder what kind of stresses would cause that weld =
to break.  Is the shaft keyed?  Maybe it should be - although that would complicate balancing it.  Perhaps balancing is
part of the problem.  Maybe at umpteen thousand rpm, +/- .5
gram isn't close enough.  

   Two senarios come to mind: (1) Turbine wheel heats up faster than the shaft; develops a small amount of clearance
at the end opposite the weld; starts wobbling a little, too
much for the weld to absorb; (2) Turbine gets a little
wobbly at high speed; after sustained high speed operation,
the vibration overcomes the weld.  

   I don't quite understand why the only thing holding that =
turbine wheel on the shaft is a *weld*.  Isn't the turbine
Iconel or similar?  Is the shaft also Iconel?  If it isn't, the j= oint is closer to being a brazing (in principle,
anyway).

My somewhat semi-random thoughts ...

Dale R.
COZY MkIV-R13B-NA #1254



 --B_3172327943_51801521--