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[70.193.206.192]) by mx.google.com with ESMTPS id h38sm57833130ani.7.2013.02.17.06.03.04 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sun, 17 Feb 2013 06:03:08 -0800 (PST) Subject: Re: [FlyRotary] Re: That damn O-ring again! References: From: Tracy Content-Type: multipart/alternative; boundary=Apple-Mail-A007CA40-CC08-4EF1-935C-FF9B140358D2 X-Mailer: iPad Mail (10B141) In-Reply-To: Message-Id: <0804DBC8-3500-41D0-9BFF-033348B2C605@gmail.com> Date: Sun, 17 Feb 2013 09:02:58 -0500 To: Rotary motors in aircraft Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (1.0) --Apple-Mail-A007CA40-CC08-4EF1-935C-FF9B140358D2 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Todd, I'm wondering what the 'recommended' fix was that you tried first. Li= ke Mark, I'm also wondering where the counterbore for the O-ring went. The problem as I understood it (on series 4 engines which most are using) wa= s originally caused when the engine was re-assembled using Mazda's replaceme= nt gasket set that has a front cover gasket MUCH thicker than the original. = This spaces the front cover about .015" farther away from the counterbore a= nd allows the o-ring to expand out into the gap where it it sheared by the e= dge of the counterbore when the oil pressure spiked on a cold start. The fix that Racing Beat recommended to me was used and documented in the co= nversion guide. It was to NOT use the gasket at all and use Ultra Gray RTV g= asket maker instead. This worked for 856 hours on my original engine and n= ever failed. =20 As always, YMMV. Tracy Sent from my iPad On Feb 17, 2013, at 7:35 AM, Lehanover@aol.com wrote: > The problem is that the front cover is very flexible and there is no faste= ner near this junction. (Thank you Mazda) > On a cold start the oil pressure at this junction can far exceed the pop p= ressure of the stock pressure relief valve located at the base of the rear i= ron. On some models of front iron there is a relief valve just below this ju= nction set at 140 pounds. This is to protect the oil cooler, which is a good= idea but is too high a pressure to keep the junction from pushing open and r= eleasing the "O" ring. =20 > =20 > The object of the thick glass reinforced white washer (probably Teflon or N= ylon) fitted at this junction was to create added pressure between the alumi= num and the cast iron. It's a spacer. > =20 > If Mazda had left the aluminum tube .060" taller than the gasket surface O= r installed a fastener close by, they would never have had this problem > =20 > This was a Mazda fix for the problem that had some success. The washer too= k up some space and then a thicker "O" ring was installed to do the sealing.= The washer might have done some sealing if oil had slipped past the "O" rin= g, but it could have been made of any sturdy material. Steel or aluminum. > =20 > Later versions of the front cover gasket had extensions of hard paper that= fit around the washer. (And did nothing). Later still a composition gasket w= ith a stainless face replacing the washer. There was never an attempt to fix= the cause. Just cheap gags to prevent the outcome. > =20 > Your fix looks just fine. I would make the ID of the brass tube just a bit= bigger and taper the ends for less drag. Oil goes through here at a fairly h= igh rate. > =20 > I have not seen how this was done on FD or Renesis engines. > =20 > Lynn E. Hanover > =20 > In a message dated 2/17/2013 5:57:16 A.M. Eastern Standard Time, msteitle@= gmail.com writes: > Todd,=20 >=20 > What happened to the counter-bore in the front iron? Did your model not h= ave a counter-bore? It appears to have been filled in with Devcon (or JB)? = The walls of the counter-bore are supposed to hold the o-ring in place and p= revent it from being forced out under pressure. At least that's my understa= nding of how it works. =20 >=20 > =46rom the pictures, it appears that the thick-wall bushing will be chokin= g off much of your oil flow, possibly causing other problems (bearing failur= e). >=20 > Mark S. >=20 > On Sun, Feb 17, 2013 at 1:34 AM, Todd Bartrim wrote: >> Hello All; >> It's been awhile since I last posted, though I've been reading almost eve= ry post to sort of keep up with the latest developments. >> The last time I flew I was seeing lower oil pressures around 35-40 ps= i, so I decided to pull the front cover the other day. I had previously had a= complete O-ring failure so had done the recommended fix at the time. When I= pulled it the other day, everything looked good but obviously wasn't. I rec= alled Chris having a repeat of this last fall so searched the archives and f= ound a reference to him pushing a small cylinder in there. There was also a p= revious post where Lynn commented on somebody else's idea of a Teflon washer= being a good idea. So I've decided to do both. Attached pics should show in= better detail than I could explain. I've done a trial fit, but will await c= omments before I assemble with sealant. >>=20 >> Todd Bartrim >>=20 >> C-FSTB >>=20 >> -- >> Homepage: http://www.flyrotary.com/ >> Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/Lis= t.html >=20 --Apple-Mail-A007CA40-CC08-4EF1-935C-FF9B140358D2 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable
Todd, I'm wondering what the 'recommen= ded' fix was that you tried first.  Like Mark, I'm also wondering where= the counterbore for the O-ring went.

The problem a= s I understood it (on series 4 engines which most are using) was originally c= aused when the engine was re-assembled using Mazda's replacement gasket set t= hat has a front cover gasket MUCH thicker than the original.   This spa= ces the front cover about .015" farther away from the counterbore and allows= the o-ring to expand out into the gap where it it sheared by the edge of th= e counterbore when the oil pressure spiked on a cold start.

The fix that Racing Beat recommended to me was used and documented i= n the conversion guide.  It was to NOT use the gasket at all and use Ul= tra Gray RTV gasket maker instead.   This worked for 856 hours on my or= iginal engine and never failed.   

As alw= ays, YMMV.

Tracy

Sent from my iPad

On Feb 17, 2013, at 7:35 AM, Lehanover@aol.com wrote:

=
The problem is that the front cover is very flexible and there is no=20= fastener near this junction. (Thank you Mazda)
On a cold start the oil pressure at this junction can far exceed the po= p=20 pressure of the stock pressure relief valve located at the base of the rear=20= iron. On some models of front iron there is a relief valve just below this=20= junction set at 140 pounds. This is to protect the oil cooler, which is a go= od=20 idea but is too high a pressure to keep the junction from pushing open and=20= releasing the "O" ring.  
 
The object of the thick glass reinforced white washer (probably Teflon o= r=20 Nylon) fitted at this junction was to create added pressure between the alum= inum=20 and the cast iron. It's a spacer.
 
If Mazda had left the aluminum tube .060" taller than the gasket=20 surface  Or installed a fastener close by, they would never have had th= is=20 problem
 
This was a Mazda fix for the problem that had some success. The washer t= ook=20 up some space and then a thicker "O" ring was installed to do the sealing. T= he=20 washer might have done some sealing if oil had slipped past the "O" ring, bu= t it=20 could have been made of any sturdy material. Steel or aluminum.
 
Later versions of the front cover gasket had extensions of hard paper t= hat=20 fit around the washer. (And did nothing). Later still a composition gasket w= ith=20 a stainless face replacing the washer. There was never an attempt to fix the= =20 cause. Just cheap gags to prevent the outcome.
 
Your fix looks just fine. I would make the ID of the brass tube just a b= it=20 bigger and taper the ends for less drag. Oil goes through here at a fairly h= igh=20 rate.
 
I have not seen how this was done on FD or Renesis engines.
 
Lynn E. Hanover
 
In a message dated 2/17/2013 5:57:16 A.M. Eastern Standard Time,=20 msteitle@gmail.com writes:
Todd, =20

What happened to the counter-bore in the front iron?  Did your m= odel=20 not have a counter-bore?  It appears to have been filled in with Devc= on=20 (or JB)?  The walls of the counter-bore are supposed to hold the o-ri= ng=20 in place and prevent it from being forced out under pressure.  At lea= st=20 that's my understanding of how it works.  

=46rom the pictures, it appears that the thick-wall bushing will be c= hoking=20 off much of your oil flow, possibly causing other problems (bearing=20 failure).

Mark S.

On Sun, Feb 17, 2013 at 1:34 AM, Todd Bartrim <= span dir=3D"ltr"><bartrim@gmail.com> wrote:
Hello All;
It's been awhile since I last posted, though I've been=20= reading almost every post to sort of keep up with the latest=20 developments.
    The last time I flew I was seeing lower oil pressures= =20 around 35-40 psi, so I decided to pull the front cover the other day. I h= ad=20 previously had a complete O-ring failure so had done the recommended fix= at=20 the time. When I pulled it the other day, everything looked good but=20 obviously wasn't. I recalled Chris having a repeat of this last fall so=20= searched the archives and found a reference to him pushing a small cylin= der=20 in there. There was also a previous post where Lynn commented on somebod= y=20 else's idea of a Teflon washer being a good idea. So I've decided to do=20= both. Attached pics should show in better detail than I could explain. I= 've=20 done a trial fit, but will await comments before I assemble with=20 sealant.

Todd Bartrim

C-FSTB
<= /div>
--
Homepage:=20  http://www.flyrotary.com/
Archive and UnSub= :   http://mail.lancaironline.net:81/lists/flyrotary/List.html


= --Apple-Mail-A007CA40-CC08-4EF1-935C-FF9B140358D2--