Return-Path: Received: from rwcrmhc13.comcast.net ([204.127.198.39] verified) by logan.com (CommuniGate Pro SMTP 4.2b8) with ESMTP id 324948 for flyrotary@lancaironline.net; Sat, 17 Jul 2004 16:14:55 -0400 Received-SPF: error receiver=logan.com; client-ip=204.127.198.39; envelope-from=bhcishere@comcast.net Received: from theboss (c-24-126-219-69.we.client2.attbi.com[24.126.219.69]) by comcast.net (rwcrmhc13) with SMTP id <20040717201423015003j5eje>; Sat, 17 Jul 2004 20:14:23 +0000 Message-ID: <00d401c46c3a$aa3d8d00$0100a8c0@madhouse.home> From: "Bryan" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: 11th test flight Date: Sat, 17 Jul 2004 13:14:26 -0700 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00D1_01C46BFF.FC090AA0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1437 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1441 This is a multi-part message in MIME format. ------=_NextPart_000_00D1_01C46BFF.FC090AA0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable From my understanding, when aluminum expands, it expands in all = directions and when it cools it contract in all directions. = Unfortunately, with the rotor housing firmly clamped between the side = housings it is not able to expand in that direction but will readily = contract during cooling. If the temperature had been high enough to = cause a high rate of expansion then cooling will require an equal rate = of contaction thus leaving a rotor housing samller in one dimension. ----- Original Message -----=20 From: Ed Anderson=20 To: Rotary motors in aircraft=20 Sent: Saturday, July 17, 2004 12:55 PM Subject: [FlyRotary] Re: 11th test flight Dale, Not being a rotary engine mechanic, I only know that one of things = that you were to check for after a case of "overheating" was "shrinkage" = of the aluminum rotor housing. I never heard an explanation for why = this supposedly happened but the thing you were to check for was the = width of the housing. There were minimum specs which if below = supposedly rendered the rotor housing "Bad". I do know that when I took = my first engine apart after overheating it to the point that the inner = coolant seals failed, I measured and found one of my housings right at = the limit - now it may well have been at that point before I ever ran = the engine as I did not measure it before hand. The only thing I could ever think of that might cause this (assuming = it was caused by overheating) is that we have 17 of those big bolts = holding that pancake together which compress the rotor housing between = the iron housings. If it go hot enough supposedly that clamping = pressure could cause the aluminum to weaken sufficiently to partially = collapse the housings coolant chambers and reduce the width of the = housing. But, that was just my take on it. =20 Now with the later engines I have not heard about this shrinkage = problem - so whether it was an "old wives tale" or there was some = substance to it that has been overcome by better castings/alloy , I = really do not know. Ed Thanks Ed, I value your insights. I know that seal chatter was an early development problem with the = wankel, but thought that Mazda had pretty much made it a thing of the = past with modern materials, geometry, and springs. I did not realize = that this was a temperature dependent problem, that we still had to deal = with. Also, not quite sure what you mean re: "shrinkage of the aluminum = rotor housings"? It can't shrink with heat. By this do you mean that, = that having exceeded some elasticity limit, the aluminum cannot return = to it's original specs upon shutdown once it has been overheated? = Wouldn't it thus be oversize? Please explain ... this sure sounds like = an "engine killer". Thanks, Dale Smith --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.719 / Virus Database: 475 - Release Date: 7/13/2004 ------=_NextPart_000_00D1_01C46BFF.FC090AA0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
From my understanding, when aluminum = expands, it=20 expands in all directions and when it cools it contract in all = directions. =20 Unfortunately, with the rotor housing firmly clamped between the side = housings=20 it is not able to expand in that direction but will readily contract = during=20 cooling.  If the temperature had been high enough to cause a high = rate of=20 expansion then cooling will require an equal rate of contaction thus = leaving a=20 rotor housing samller in one dimension.
----- Original Message -----
From:=20 Ed=20 Anderson
Sent: Saturday, July 17, 2004 = 12:55=20 PM
Subject: [FlyRotary] Re: 11th = test=20 flight

 Dale,
 
    Not being a rotary = engine=20 mechanic, I only know that one of things that you were to check for = after a=20 case of "overheating" was "shrinkage" of the aluminum rotor = housing.  I=20 never heard an explanation for why this supposedly  happened but = the=20 thing you were to check for was the width of the housing.  There = were=20 minimum specs which if below supposedly rendered the rotor housing=20 "Bad".  I do know that when I took my first engine apart after=20 overheating it to the point that the inner coolant seals failed, I = measured=20 and found one of my housings right at the limit - now it may well have = been at=20 that point before I ever ran the engine as I did not measure it before = hand.
 
The only thing I could ever think of = that might=20 cause this (assuming it was caused by overheating) is that we have 17 = of those=20 big bolts holding that pancake together which compress the rotor = housing=20 between the iron housings.  If it go hot enough supposedly that = clamping=20 pressure could cause the aluminum to weaken sufficiently to partially = collapse=20 the housings coolant chambers and reduce the width of the = housing.  But,=20 that was just my take on it. 
 
Now with the later engines I have not = heard about=20 this shrinkage problem - so whether it was an "old wives tale" or = there was=20 some substance to it that has been overcome by better castings/alloy , = I=20 really do not know.
 
Ed
 

Thanks Ed,  I value your = insights.

I know=20 that seal chatter was an early development problem with the wankel, = but=20 thought that Mazda had pretty much made it a thing of the past with = modern=20 materials, geometry, and springs.  I did not realize that this = was a=20 temperature dependent problem, that we still had to deal = with.

Also,=20 not quite sure what you mean re: "shrinkage of the aluminum rotor=20 housings"?   It can't shrink with heat.  By this do = you mean=20 that, that having exceeded some elasticity limit, the aluminum = cannot return=20 to it's original specs upon shutdown once it has been=20 overheated?   Wouldn't it thus be oversize?   = Please=20 explain ... this sure sounds like an "engine=20 killer".

Thanks,

Dale Smith
 

---
Outgoing mail is certified Virus=20 Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: = 6.0.719 / Virus Database: 475 - Release Date:=20 7/13/2004
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