Jon and Pete,
I have the same problem on two 912S engines on #3 and #1 cylinder.
One is clearly a tune problem which causes excessive vibration of the
muffler and clear engine shake...
The other was more interesting. The pipe and spring combination seems
to resonate during runs about 5000 RPM. I may have a harmonic problem.
Chris Piper (CKT) and I have discussed the problem and we are going to
stainless springs and then checking again, but the engine has a left to
right shake that causes the muffler to want to swing back and forth
under the engine, but of course the exhaust bolts and friction prevent
that, and the pipe seems to fail.
The spring fails then the pipe I expected went before the spring, but
don't know for sure. Tuning the engine was the first step. As we all
know, the 912S is a bit rough on start and stop, but generally smooth
once above 2500 RPM. However, with the fixed pitch props when entering
the pattern at 130 knots then throttling back for downwind, the prop (a
Warp Drive on an Airmaster manual not auto control) tends to vibrate a
bit during de-acceleration and the engine vibration is quite noticeable
in the feel, but not visually. We broke #1 spring and safety wire from
the vibration. #1 has an adjustable leg of course and did not crack the
pipe. But I am concerned. Something is vibrating at a harmonic down
there.
I am at a loss at the reason for the vibration crack on only one
cylinder. One would think it would affect more than one pipe. Our
checks were:
Does the silencer hit anything on the engine or frame? No.
Is the engine in tune. Yes
Is the prop balanced. Yes
Is the prop blade tracking true. Yes
Is the prop blade angle true. Yes
Is the pipe overcooled by ram air. Not really
Are the springs tight with no twist or torque imparted. Yes
Is the pipe securely seated in the silencer. Yes
Is the pipe over-torqued. No.
Does the crack start at a weld. Possibly.
Are the engine mounts sound and firm. Yes
Are the engine attach bolts and frame secure. Yes
I'm running out of ideas myself.
Regards and still looking for the solution:
Bud Yerly
Custom Flight Creations, Inc.
www.customflightcreations.com<http://www.customflightcreations.com/>
(813) 653-4989
----- Original Message -----
From: Pete Lawless<mailto:pete@lawless.info>
To: europa-list@matronics.com<mailto:europa-list@matronics.com>
Sent: Friday, August 24, 2012 2:58 PM
Subject: RE: Europa-List: Re: XS Exhaust System Cracks
<pete@lawless.info<mailto:pete@lawless.info>>
Hi Jon
My crack ran along the inside of the bend along the length of the
pipe,
rather than round it. It is noticeable that the crack is just along
the
bottom of the weld for the exhaust spring, though if that is anything
to do
with the problem I could not say.
We had fun with the CKT exhaust pipes last year 3 of the 4 flanges(?)
where
they bolt to the heads cracked off. The replacements are considerably
better welded.
I dealt with CKT direct for my replacements. Chris Piper is the man
to talk
to. 01884 242211 if you need the number.
Pete
PS I seem to remember G-TERN parked outside the hanger at Kemble?
-----Original Message-----
From:
owner-europa-list-server@matronics.com<mailto:owner-europa-list-server@ma
tronics.com>
[mailto:owner-europa-list-server@matronics.com] On Behalf Of JonSmith
Sent: 24 August 2012 19:20
To: europa-list@matronics.com<mailto:europa-list@matronics.com>
Subject: Europa-List: Re: XS Exhaust System Cracks
<jonsmitheuropa@tiscali.co.uk<mailto:jonsmitheuropa@tiscali.co.uk>>
Hi Pete, thanks for your reply. I should have said that mine already
is an
XS version, stainless steel by CKT. On mine its both the rear pipes
that
keep cracking (twice for both of them). The front ones have so far
been ok.
Attached is a photo of one of the rear pipes - the other was similar.
Cheers, Jon
--------
G-TERN
Classic Mono
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=381713#381713<http://forums
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