Return-Path: Received: from fed1rmmtao10.cox.net ([68.230.241.29] verified) by logan.com (CommuniGate Pro SMTP 4.2b7) with ESMTP id 310761 for flyrotary@lancaironline.net; Sat, 10 Jul 2004 17:45:46 -0400 Received: from smtp.west.cox.net ([172.18.180.57]) by fed1rmmtao10.cox.net (InterMail vM.6.01.03.02 201-2131-111-104-20040324) with SMTP id <20040710214515.UGUZ13283.fed1rmmtao10.cox.net@smtp.west.cox.net> for ; Sat, 10 Jul 2004 17:45:15 -0400 From: Dale Rogers To: "Rotary motors in aircraft" Subject: Re: [FlyRotary] Re: Three candidates for Turbo Failure Date: Sat, 10 Jul 2004 17:45:16 -0400 MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="----=____1089495916650_VnwCDM'lcL" Message-Id: <20040710214515.UGUZ13283.fed1rmmtao10.cox.net@smtp.west.cox.net> This is a multi-part message in MIME format. ------=____1089495916650_VnwCDM'lcL Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Hi All, Re: > From: "John Slade" > Date: 2004/07/10 Sat AM 10:38:18 EDT > To: "Rotary motors in aircraft" > Subject: [FlyRotary] Re: Three candidates for Turbo Failure > > ... > ... 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, the > 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 joint is closer to being a brazing (in principle, anyway). My somewhat semi-random thoughts ... Dale R. COZY MkIV-R13B-NA #1254 ------=____1089495916650_VnwCDM'lcL Content-Type: text/html; name="reply" Content-Disposition: inline; filename="reply"
>loose compressor wheels
I'm afraid incorrect terminology may have sent you off in the wrong direction. 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, the wheel came off and blocked the exhaust outlet.
Thanks for all the brain work. Very interesting stuff.
Regards,
john
 
------=____1089495916650_VnwCDM'lcL--