X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mx2.magma.ca ([206.191.0.250] verified) by logan.com (CommuniGate Pro SMTP 4.3.4) with ESMTPS id 989477 for flyrotary@lancaironline.net; Wed, 08 Jun 2005 22:31:26 -0400 Received-SPF: none receiver=logan.com; client-ip=206.191.0.250; envelope-from=ianddsl@magma.ca Received: from mail1.magma.ca (mail1.magma.ca [206.191.0.252]) by mx2.magma.ca (8.13.0/8.13.0) with ESMTP id j592Ubxn021452 for ; Wed, 8 Jun 2005 22:30:38 -0400 Received: from binky (ottawa-hs-64-26-156-111.s-ip.magma.ca [64.26.156.111]) by mail1.magma.ca (8.13.0/8.13.0) with SMTP id j592UXkP030820 for ; Wed, 8 Jun 2005 22:30:37 -0400 Reply-To: From: "Ian Dewhirst" To: "Rotary motors in aircraft" Subject: RE: [FlyRotary] Re: coolant leak Date: Wed, 8 Jun 2005 22:30:33 -0400 Message-ID: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0002_01C56C79.AF1D68F0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.6604 (9.0.2911.0) Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 This is a multi-part message in MIME format. ------=_NextPart_000_0002_01C56C79.AF1D68F0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Hi Al, I agree that maintaining residual pressure due to a compression leak in a piston engine is close to impossible, the type of gaskets used don't allow this to happen, once you breach the head gasket seal you have a coolant leak and it is quite likely the coolant will flow into the combustion chamber after the engine is stopped. On a rotary engine things are a bit different. It is quite possible to have sufficient combustion pressure that some of the gasses push past the o-rings that seal the combustion chamber from the coolant jacket, these gasses are vented to the atmosphere by the cap. When the engine is turned off with the cooling system pressurized the seal acts as a check valve and does not allow the coolant to flow back into the combustion chamber. This soft failure can carry on for quite a while. Probably the best test for rotary combustion chamber o-rings would be to crank the engine with the injectors off while watching the coolant pressure gauge, if the gauge bumps of the pin with the cumprssion strokes then you are pretty much guaranteed that you have an internal sealing problem; might be the seals or the irons or the rotor housings. I've called them o-rings but they are actually trapezoid rings :-) -- Ian -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]On Behalf Of al p wick Sent: Wednesday, June 08, 2005 10:05 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: coolant leak I've got sensors up the wazoo....some on my plane too. I record this info every few milliseconds. Calibrated sensors. So here is what I see. If I want my cooling system to operate at 24 psi, all I have to do is fill my swirl pot to the top with coolant. If I don't want it to see that high pressure, I just leave around a cup of air at the top of swirl pot. With my cup of air, it never exceeds 7 psi. Why? Air is compressible, coolant is not. When you first fire up engine, pressure is 0, relative to atmosphere. It takes around 8 minutes for pressure to slowly climb to 1 psi. The fluid level starts to rise too. All pressure increase is due to expansion of coolant due to heat. Coolant is not compressible, and can greatly increase force against the contained cooling system. After you shut off your engine, the 7 psi gradually drops over the next few minutes. It only takes around 12 minutes for the system to develop a vacuum relative to atmosphere. At that point the little valve in the radiator cap opens and allows fluid or air to flow into system. (Check out your rad cap, can you find both valves?) Logically, from that point on, you can't have a pressurized system. There is no added energy supplied to the system. With one exception: If you have compression leak into cooling system. But even that should have limited duration. Also, if you had a cooling sys that was normally under pressure, then none of the vehicles would be able to replenish their coolant. They rely on the atmospheric pressure to exceed the coolant pressure 12 minutes after shutdown. That's what forces that liquid in our "overflow" bottle to enter radiator. I'd double check my gage calibration if seeing pressure on startup. When I did ground testing with compression leak, this pattern would change. 1 second after full throttle, the pressure would jump to 24 psi, fluid level max out, temperature still cold. This would last for only 5 seconds. This entrained air then had profound effect on the entire cooling sys. I think that was the most interesting part. -al wick Artificial intelligence in cockpit, Cozy IV powered by stock Subaru 2.5 N9032U 200+ hours on engine/airframe from Portland, Oregon Prop construct, Subaru install, Risk assessment, Glass panel design info: http://www.maddyhome.com/canardpages/pages/alwick/index.html On Wed, 8 Jun 2005 18:05:23 -0700 "Al Gietzen" writes: Some of the coolant is going to vaporize. This pressurises the system. Some of that vapor will never go back into solution so there should be pressure in the system even when cold. Dave; this may be the weak link in your logic chain. Why would some of the vapor not re-condense? I hope there is some other reason for the pressure. I'd hate for you to have to tear open the engine. Al Gietzen ------=_NextPart_000_0002_01C56C79.AF1D68F0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable
Hi Al,=20 I agree that maintaining residual pressure due to a compression=20 leak in a piston engine is close to impossible, the type of gaskets = used=20 don't allow this to happen, once you breach the head gasket = seal you have a=20 coolant leak and it is quite likely the coolant will flow into = the=20 combustion chamber after the engine is stopped.  =
 
On a=20 rotary engine things are a bit different. It is quite possible to = have=20 sufficient combustion  pressure that some of the gasses push past = the=20 o-rings that seal the combustion chamber from the coolant jacket, these = gasses=20 are vented to the atmosphere by the cap.  When the engine is turned = off=20 with the cooling system pressurized the seal acts as a check valve and = does not=20 allow the coolant to flow back into the combustion = chamber.  This=20 soft failure can carry on for quite a while.
 
Probably the best test for rotary combustion chamber = o-rings would=20 be to crank the engine with the injectors off while watching the coolant = pressure gauge, if the gauge bumps of the pin with the cumprssion=20 strokes then you are pretty much guaranteed that you have an = internal=20 sealing problem; might be the seals or the irons or the rotor=20 housings.
 
I've=20 called them o-rings but they are actually trapezoid rings=20 :-)
 
--=20 Ian
-----Original Message-----
From: Rotary motors in = aircraft=20 [mailto:flyrotary@lancaironline.net]On Behalf Of al p=20 wick
Sent: Wednesday, June 08, 2005 10:05 PM
To: = Rotary=20 motors in aircraft
Subject: [FlyRotary] Re: coolant=20 leak

I've got sensors up the wazoo....some on my plane too. I record = this info=20 every few milliseconds. Calibrated sensors. So here is what I = see.
 
If I want my cooling system to operate at 24 psi, all I have to = do is=20 fill my swirl pot to the top with coolant. If I don't want it to = see that=20 high pressure, I just leave around a cup of air at the top of swirl = pot. With=20 my cup of air, it never exceeds 7 psi. Why? Air is compressible, = coolant is=20 not.
When you first fire up engine, pressure is 0, relative to = atmosphere. It=20 takes around 8 minutes for pressure to slowly climb to 1 psi. The = fluid level=20 starts to rise too. All pressure increase is due to expansion of = coolant due=20 to heat. Coolant is not compressible, and can greatly increase force = against=20 the contained cooling system.
 
After you shut off your engine, the 7 psi gradually drops = over the=20 next few minutes. It only takes around 12 minutes for the system to = develop a=20 vacuum relative to atmosphere. At that point the little valve in the = radiator=20 cap opens and allows fluid or air to flow into system. (Check out your = rad=20 cap, can you find both valves?)
 Logically, from that point on, you can't have a = pressurized=20 system. There is no added energy supplied to the system. With one = exception:=20 If you have compression leak into cooling system. But even that should = have=20 limited duration.
Also, if you had a cooling sys that was normally under pressure, = then=20 none of the vehicles would be able to replenish their = coolant. They rely=20 on the atmospheric pressure to exceed the coolant pressure 12 minutes = after=20 shutdown. That's what forces that liquid in our "overflow" bottle = to=20 enter radiator. 
 
I'd double check my  gage calibration if seeing pressure on=20 startup.
 
When I did ground testing with compression leak, this pattern = would=20 change. 1 second after full throttle, the pressure would jump to 24 = psi, fluid=20 level max out, temperature still cold. This would last for only 5 = seconds.=20 This entrained air then had profound effect on the entire cooling sys. = I think=20 that was the most interesting part.

-al wick
Artificial intelligence in cockpit, Cozy IV = powered by=20 stock Subaru 2.5
N9032U 200+ hours on engine/airframe from = Portland,=20 Oregon
Prop construct, Subaru install, Risk assessment, Glass panel = design=20 = info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html
=
 
 
On Wed, 8 Jun 2005 18:05:23 -0700 "Al Gietzen" <ALVentures@cox.net> = writes:

 

Some of the coolant is = going to=20 vaporize.  This pressurises the system.  Some of that = vapor will=20 never go back into solution so there should be pressure in the = system even=20 when cold. 

 

Dave; = this may be=20 the weak link in your logic chain.  Why would some of the vapor = not=20 re-condense?  I hope there is some other reason for the = pressure. =20 I’d hate for you to have to tear open the = engine.

 

Al=20 Gietzen

 

 
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