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kheindl(at)msn.com
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 Posted: Mon May 07, 2007 5:19 am Post subject: Melting silencer |
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The mod 72 has one good side benefit, it gives us the chance for a real
close inspection of the back of the engine and underneath. I had to remove
the silencer for better access to the firewall and two bottom frame bolts.
Here is what I discovered :
The bottom of the silencer , starboard side, an oval area of 30x90mm was
badly pitted with strong signs of having melted. The aluminum duct directly
underneath is similarly affected. I tapped the affected area with a hammer
to look for any weakness, but it appears to be still okay. The aluminum is
paper thin and needs to be patched.
My installation is a standard 912S fwf kit with stainless exhaust system and
Singleton firewall. I never experienced any temperatures (according to the
EIS) above the permissable ranges. The EGT probes are on the exhaust stubs
of cylinders 3 and 4. I never noticed anything unusual.
There is no other heat damage. The coolant pipe directly behind it to the
radiator shows no sign of anything unusual.
My questions are:
Has anyone ever experienced or heard of anything like this before ? What
could be the possible cause ? What is the melting point of stainless steel ?
There is no direct fresh air to the bottom of the engine. Some time ago I
had taped off the starboard NACA duct, as it was supposedly designed for the
914. There was no detrimental effect to the engine temperatures. I have now
opened up the precut flap in the starboard side of the alu duct, which will
divert some fresh air to the silencer. (I believe this flap was also
designed for the 914).
One very long shot : Could there be any electrical sparking between the two
surfaces, acting like a capacitor ? I just don't see how those high
temperatures could come from the exhaust gases without also burning the
outside of the fuselage etc.
I wonder if anyone knows. And any help greatly appreciated.
Karl
_________________________________________________________________
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terrys(at)cisco.com
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| Posted: Mon May 07, 2007 9:00 am Post subject: Melting silencer |
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Hi Karl,
We have a 912S powered XS and had problems with very high temperatures
under the cowl, near the muffler, hot enough to melt nylon tie wraps
(about 450 deg F melting point) and take the temper out of exhaust
retaining springs. We spent many months working on getting this under
control, doing many test flights with data logging of multiple in-cowl
temperatures. What we found was that air would stagnate around the
muffler, creating very high localized temperatures. Many things were
tried (some similar to what you have tried) until we finally found a
solution. We opened up the exit area for the engine compartment, closed
off the gills in the top cowl because they were letting cooling air
escape without cooling anything, and finally installed a baffle between
the foot wells to keep cooling air from just going around the back of
the engine without cooling much. These three mods forced the air to go
around the cylinders and then around both sides of the muffler.
This mod solved our in-cowl temperature problems and lowered our oil
temperatures about 20 deg F in the climb.
A write up of what we did can be found at;
http://terryseaver.home.comcast.net/N135TD_mods.htm
Look at the section titled: Engine compartment cooling
Regards,
Terry Seaver
A135/N135TD
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kheindl(at)msn.com
Guest
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| Posted: Mon May 07, 2007 9:25 am Post subject: Melting silencer |
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Hi Terry,
A very interesting comparison. But why doesn't everyone have this problem ?
I never noticed high temperatures, and then how can your case reach melting
point of stainless steel. And my affected area is very specific with no
scorching anywhere else.
I still have this theory about an electrical discharge between aluminum duct
and engine above. The duct, including radiators, is electrically isolated. I
assume that coolant and oil are not very good conductors.
Cheers,
Karl
[quote]From: "Terry Seaver (terrys)" <terrys(at)cisco.com>
Reply-To: europa-list(at)matronics.com
To: <europa-list(at)matronics.com>
Subject: RE: Melting silencer
Date: Mon, 7 May 2007 09:58:20 -0700
<terrys(at)cisco.com>
Hi Karl,
We have a 912S powered XS and had problems with very high temperatures
under the cowl, near the muffler, hot enough to melt nylon tie wraps
(about 450 deg F melting point) and take the temper out of exhaust
retaining springs. We spent many months working on getting this under
control, doing many test flights with data logging of multiple in-cowl
temperatures. What we found was that air would stagnate around the
muffler, creating very high localized temperatures. Many things were
tried (some similar to what you have tried) until we finally found a
solution. We opened up the exit area for the engine compartment, closed
off the gills in the top cowl because they were letting cooling air
escape without cooling anything, and finally installed a baffle between
the foot wells to keep cooling air from just going around the back of
the engine without cooling much. These three mods forced the air to go
around the cylinders and then around both sides of the muffler.
This mod solved our in-cowl temperature problems and lowered our oil
temperatures about 20 deg F in the climb.
A write up of what we did can be found at;
http://terryseaver.home.comcast.net/N135TD_mods.htm
Look at the section titled: Engine compartment cooling
Regards,
Terry Seaver
A135/N135TD
--
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ami(at)mcfadyean.freeserv
Guest
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| Posted: Mon May 07, 2007 11:53 am Post subject: Melting silencer |
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Was the "heat-stressing" opposite where one of the header pipes goes in to
the silencer i.e. where hot gases directly from the end of the header pipe
would impinge internally?
Duncan McF.
---
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kheindl(at)msn.com
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| Posted: Mon May 07, 2007 2:47 pm Post subject: Melting silencer |
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No, it was a little forward of that. Think of the temperatures. What is
stainless steel melting point ?
And if the heat came from the inside, why is not burned right through ?
Karl
[quote]From: "Duncan & Ami McFadyean" <ami(at)mcfadyean.freeserve.co.uk>
Reply-To: europa-list(at)matronics.com
To: <europa-list(at)matronics.com>
Subject: Re: Melting silencer
Date: Mon, 7 May 2007 20:52:44 +0100
<ami(at)mcfadyean.freeserve.co.uk>
Was the "heat-stressing" opposite where one of the header pipes goes in to
the silencer i.e. where hot gases directly from the end of the header pipe
would impinge internally?
Duncan McF.
---
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grahamsingleton(at)btinte
Guest
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| Posted: Mon May 07, 2007 4:25 pm Post subject: Melting silencer |
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Karl
stainless steel melts around 1550 deg C so it's highly unlikely you have
melting.
Karl Heindl wrote:
| Quote: |
The mod 72 has one good side benefit, it gives us the chance for a real
close inspection of the back of the engine and underneath. I had to
remove the silencer for better access to the firewall and two bottom
frame bolts. Here is what I discovered :
The bottom of the silencer , starboard side, an oval area of 30x90mm was
badly pitted with strong signs of having melted. The aluminum duct
directly underneath is similarly affected. I tapped the affected area
with a hammer to look for any weakness, but it appears to be still okay.
The aluminum is paper thin and needs to be patched.
My installation is a standard 912S fwf kit with stainless exhaust system
and Singleton firewall. I never experienced any temperatures (according
to the EIS) above the permissable ranges. The EGT probes are on the
exhaust stubs of cylinders 3 and 4. I never noticed anything unusual.
There is no other heat damage. The coolant pipe directly behind it to
the radiator shows no sign of anything unusual.
My questions are:
Has anyone ever experienced or heard of anything like this before ? What
could be the possible cause ? What is the melting point of stainless
steel ?
There is no direct fresh air to the bottom of the engine. Some time ago
I had taped off the starboard NACA duct, as it was supposedly designed
for the 914. There was no detrimental effect to the engine temperatures.
I have now opened up the precut flap in the starboard side of the alu
duct, which will divert some fresh air to the silencer. (I believe this
flap was also designed for the 914).
One very long shot : Could there be any electrical sparking between the
two surfaces, acting like a capacitor ? I just don't see how those high
temperatures could come from the exhaust gases without also burning the
outside of the fuselage etc.
I wonder if anyone knows. And any help greatly appreciated.
Karl
_________________________________________________________________
MSN Hotmail is evolving - check out the new Windows Live Hotmail
http://get.live.com/betas/mail_betas
|
--
Graham Singleton
Tel: +441629820187
Mob: +447739582005
| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Europa-List |
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kheindl(at)msn.com
Guest
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| Posted: Mon May 07, 2007 4:59 pm Post subject: Melting silencer |
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Hi Graham,
Thank you for that useful bit regarding temperature. I can assure you 100%
it is melted droplets of metal, and the aluminum underneath has melted away
almost completely. Was I hit by lightning maybe ? I did get into a
thunderstorm once.
Karl
ps: if Europe 04 send me a replacement silencer I will be happy to return
mine for inspection.
| Quote: | From: Graham Singleton <grahamsingleton(at)btinternet.com>
Reply-To: europa-list(at)matronics.com
To: europa-list(at)matronics.com
Subject: Re: Melting silencer
Date: Tue, 08 May 2007 01:25:26 +0100
<grahamsingleton(at)btinternet.com>
Karl
stainless steel melts around 1550 deg C so it's highly unlikely you have
melting.
Karl Heindl wrote:
>
>
>The mod 72 has one good side benefit, it gives us the chance for a real
>close inspection of the back of the engine and underneath. I had to remove
>the silencer for better access to the firewall and two bottom frame bolts.
>Here is what I discovered :
>The bottom of the silencer , starboard side, an oval area of 30x90mm was
>badly pitted with strong signs of having melted. The aluminum duct
>directly underneath is similarly affected. I tapped the affected area with
>a hammer to look for any weakness, but it appears to be still okay. The
>aluminum is paper thin and needs to be patched.
>
>My installation is a standard 912S fwf kit with stainless exhaust system
>and Singleton firewall. I never experienced any temperatures (according to
>the EIS) above the permissable ranges. The EGT probes are on the exhaust
>stubs of cylinders 3 and 4. I never noticed anything unusual.
>There is no other heat damage. The coolant pipe directly behind it to the
>radiator shows no sign of anything unusual.
>
>My questions are:
>
>Has anyone ever experienced or heard of anything like this before ? What
>could be the possible cause ? What is the melting point of stainless steel
>?
>
>There is no direct fresh air to the bottom of the engine. Some time ago I
>had taped off the starboard NACA duct, as it was supposedly designed for
>the 914. There was no detrimental effect to the engine temperatures. I
>have now opened up the precut flap in the starboard side of the alu duct,
>which will divert some fresh air to the silencer. (I believe this flap was
>also designed for the 914).
>
>One very long shot : Could there be any electrical sparking between the
>two surfaces, acting like a capacitor ? I just don't see how those high
>temperatures could come from the exhaust gases without also burning the
>outside of the fuselage etc.
>
>I wonder if anyone knows. And any help greatly appreciated.
>
>Karl
>
>_________________________________________________________________
>MSN Hotmail is evolving - check out the new Windows Live Hotmail
>http://get.live.com/betas/mail_betas
--
Graham Singleton
Tel: +441629820187
Mob: +447739582005
|
_________________________________________________________________
Reserve your place in history - Email Britain!
http://www.emailbritain.co.uk/
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