X-Virus-Scanned: clean according to Sophos on Logan.com X-PolluStop: No license found, only first 5 messages were scanned Return-Path: Received: from mail06.syd.optusnet.com.au ([211.29.132.187] verified) by logan.com (CommuniGate Pro SMTP 5.1c.1) with ESMTPS id 1210757 for flyrotary@lancaironline.net; Wed, 28 Jun 2006 18:40:01 -0400 Received-SPF: none receiver=logan.com; client-ip=211.29.132.187; envelope-from=lendich@optusnet.com.au Received: from george (d220-236-206-198.dsl.nsw.optusnet.com.au [220.236.206.198]) by mail06.syd.optusnet.com.au (8.12.11/8.12.11) with SMTP id k5SMd1D8013025 for ; Thu, 29 Jun 2006 08:39:05 +1000 Message-ID: <002901c69b03$a934e120$c6ceecdc@george> From: "george lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: damage report Date: Thu, 29 Jun 2006 08:39:03 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0026_01C69B57.7A036260" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 This is a multi-part message in MIME format. ------=_NextPart_000_0026_01C69B57.7A036260 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Lynn, I have a question - a guide would be appreciated, a rule of thumb even! Understanding that heated air ( caused one way or another) has a = contributing factor to detonation at what sort of compression would you = expect to see detonation starting to occur on an average day ( = temperature wise) at sea level. Secondly, given a 10:1 compression at what temperature would you expect = to see detonation, on an average day, at sea level. Is there any graph that shows the relationship to compression, inlet = temp, engine temp and altitude as a guide to possible detonation events. I would think something like this would be handy to have available to = everyone, with perhaps an adjustment value for different fuels. George (down under) ----- Original Message -----=20 From: Lehanover@aol.com=20 To: Rotary motors in aircraft=20 Sent: Thursday, June 29, 2006 12:04 AM Subject: [FlyRotary] Re: damage report In a message dated 6/28/2006 7:51:23 A.M. Eastern Daylight Time, = eanderson@carolina.rr.com writes: LARGER QUESTION: It is obvious to me that a LOT of heat was = generated to melt the rubber plugs on BOTH sides of the rotor. Does = anyone care to venture a guess as to why that rotor was so much hotter = than the other? The EGTs were within a few degrees most of the time. I = will double check the oil jet that cools the rotor tomorrow.=20 The three piece seals are more trouble prone than the two piece. I = would go to two piece 3MM Tracy seals. The recut of the grooves to 3MM = will remove any wear problems. It looks to me like a detonation episode. However the look of the = pieces should be more granular as in a stress fracture, unless the = engine ran for some time after the failure. Once the compression goes = down the detonation problem becomes less likely to re-occur and looking = at gages will show nothing. The rear housing runs hotter all of the time. Detonation is charge = temperature dependant. This is very hard to do in a NA engine unless the = coolant temp has been very high. This is also what happens when all of = the air is not removed (very hard to do) an engine. In turbo engines with the boost up it is common. Boosted engines = change compression ratios and displacement all of the time.=20 Failures in the rear housing are far more common at high power = settings including failed dowel tubes once over 450 HP. The housings are = twisting in the opposite direction from the crank. And detonation helped = along from the temp difference in the housings.=20 If you have two or more plugs in any engine you have filled in one of = the blocks in the quiz on how can I make this pig detonate.=20 An ignition event that occurs after the planned (timed) ignition and = remote from the first plug firing. So if there are two plugs, and they = both fire at the same time, then there will be a flame front collision = every time, that is of little note. My opinion is that the bigger the = spread between leading and trailing the worse it is. If the rotor housing is overheated and the oil temp is high (rotor = face temps controlled by oil temp) then the stage is set for an event. = Detonation will occur remote from the first plug to fire and usually = closer to an apex seal. By the time the overheated mixture is compressed = into the corner over a seal and it goes off before the flame front can = get to it, it is not the smooth slow flame front like burning a thin = layer of leaves on the ground. It is a shotgun blast.=20 The Lambda sensor can hear it. You can hear it. You dads pickup truck = did it all the time. That tinkling sound going uphill in top gear. it can shatter an apex = seal like glass. Note that Ken disables his trailing ignition during his nitrous shot. = Why, do you ask?=20 To eliminate detonation. I am distressed by reports of high coolant temps and oil temps on = climb out going unchecked and being done with regularity.=20 If you run across the freeway often enough, eventually you will be = killed. It is so easy to avoid. Intake the coolest air possible. Maintain acceptable operating temps, = oil and coolant. Tune climb power to rich of best power. Why does a O-550 use 23 GPH to = take off and climb out, and then lean to 12 GPH for cruise at the same = RPM? Fuel cooling and lower flame front speed, and lower CHTs. =20 In a boosted street engine, the controller snatches away ignition = advance with each Lambda hit. Is there a clue here? =20 The highest heat is right at the best power setting. (just rich of = peak EGT). So if it hurts when you do that.....don't do that. Make the = transition from climb mixture, richer than best power, to cruise = mixture, leaner than 50 degrees lean of peak power, quickly, so as not = to spend many RPM at (or even near) best power. Or have one controller = for takeoff and climb and the other for cruise. Since intake air temp is the culprit, perhaps insulated the intake = runners is in order. Or a blast tube blowing on them. Intake air temp = includes heat of compression in the chamber. That is why boosted engines = are more likely to detonate. That is also why they have an inter-cooler = to remove heat from the intake air. That is also why they inject water = at high boost numbers. Or water and alcohol in big radials at military = power.=20 High compression rotors? more likely than lower compression rotors. = (because the heat of compression is higher) Ignition advance later (less likely) ignition advance sooner (more = likely). Note that the controller takes out advance when the Lambda = sensor hears detonation.=20 Adjust advance to show some percentage of RPM below max for any = situation. A 13B makes more power right up to 39-40 degrees of advance, = but it adds a ton of extra heat along with a small amount of extra = power. But power it does make, and if you just watch for more RPM as you = advance the timing, you will tune for way too much advance, and more = heat than you can dispose of.=20 Keep in mind that flame front speed in feet per second has a time = function. So?=20 Unless there is one of those emergencies where real short engine life = is not going to be a factor, roll in that throttle slowly. Detonation is = more likely at high load lower RPM, than at high load high RPM. (remember dads pickup) The propeller is always in top gear. We raced for years on 20-22 degrees total and made good power up to = 9,000 RPM. That is on crap for gas. On 100LL you can go well above that = in a 13B, maybe 26-28 degrees. If you get a dose of car gas with alcohol = in it, remember that for any situation it is leaner than 100% gasoline. = I have fried more than a few of these. It got too expensive after a = while so I quit doing it. Lynn E. Hanover =20 ------=_NextPart_000_0026_01C69B57.7A036260 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Lynn,
I have a question - a guide would be appreciated, a rule of thumb=20 even!
 
Understanding that heated air ( caused one way or another) has a=20 contributing factor to detonation at what sort of = compression=20 would you expect to see detonation starting to occur on an average = day (=20 temperature wise) at sea level.
Secondly, given a 10:1 compression at what = temperature=20 would you expect to see detonation, on an average day, at sea = level.
Is there any graph that shows the relationship to compression, = inlet temp,=20 engine temp and altitude as a guide to possible detonation events.
I would think something like this would be handy to have available = to=20 everyone, with perhaps an adjustment value for different = fuels.
George (down under)
----- Original Message -----
From:=20 Lehanover@aol.com
Sent: Thursday, June 29, 2006 = 12:04=20 AM
Subject: [FlyRotary] Re: damage = report

In a message dated 6/28/2006 7:51:23 A.M. Eastern Daylight Time, = eanderson@carolina.rr.com=20 writes:
LARGER QUESTION:  It is obvious to me that a LOT of heat = was=20 generated to melt the rubber plugs on BOTH sides of the rotor.  = Does=20 anyone care to venture a guess as to why that rotor was so much = hotter than=20 the other?  The EGTs were within a few degrees most of the = time. =20 I will double check the oil jet that cools the rotor tomorrow.=20
The three piece seals are more trouble prone than the two piece. = I would=20 go to two piece 3MM Tracy seals. The recut of the grooves to 3MM will = remove=20 any wear problems.
 
It looks to me like a detonation episode. However the look of the = pieces=20 should be more granular as in a stress fracture, unless the engine ran = for=20 some time after the failure. Once the compression goes down the = detonation=20 problem becomes less likely to re-occur and looking at gages will = show=20 nothing.
 
 The rear housing runs hotter all of the time. Detonation is = charge=20 temperature dependant. This is very hard to do in a NA engine unless = the=20 coolant temp has been very high. This is also what happens when all of = the air=20 is not removed (very hard to do) an engine.
 
In turbo engines with the boost up it is common. Boosted engines = change=20 compression ratios and displacement all of the time.
 
Failures in the rear housing are far more common at high power = settings=20 including failed dowel tubes once over 450 HP. The housings are = twisting in=20 the opposite direction from the crank. And detonation helped along = from the=20 temp difference in the housings.
 
If you have two or more plugs in any engine you have filled in = one of the=20 blocks in the quiz on how can I make this pig detonate.
 
An ignition event that occurs after the planned (timed) ignition = and=20 remote from the first plug firing. So if there are two plugs, and they = both=20 fire at the same time, then there will be a flame front collision = every time,=20 that is of little note. My opinion is that the bigger the spread = between=20 leading and trailing the worse it is.
 
 If the rotor housing is overheated and the oil temp is high = (rotor=20 face temps controlled by oil temp) then the stage is set for an event. = Detonation will occur remote from the first plug to fire and usually = closer to=20 an apex seal. By the time the overheated mixture is compressed into = the corner=20 over a seal and it goes off before the flame front can get to it, it = is not=20 the smooth slow  flame front like burning a thin layer of leaves = on the=20 ground. It is a shotgun blast.
The Lambda sensor can hear it. You can hear it. You dads pickup = truck did=20 it all the time.
That tinkling sound going uphill in top gear. it can shatter an = apex seal=20 like glass.
 
Note that Ken disables his trailing ignition during his nitrous = shot.=20 Why, do you ask?
 
To eliminate detonation.
 
I am distressed by reports of high coolant temps and oil temps on = climb=20 out going unchecked and being done with regularity.
 
If you run across the freeway often enough, eventually you will = be=20 killed. It is so easy to avoid.
 
Intake the coolest air possible. Maintain acceptable operating = temps, oil=20 and coolant.
 
Tune climb power to rich of best power. Why does a O-550 use 23 = GPH to=20 take off and climb out, and then lean to 12 GPH for cruise at the same = RPM?=20 Fuel cooling and lower flame front speed, and lower = CHTs.  
 
In a boosted street engine, the controller snatches away = ignition=20 advance with each Lambda hit. Is there a clue here?  
 
The highest heat is right at the best power setting. (just rich = of peak=20 EGT). So if it hurts when you do that.....don't do that. Make the = transition=20 from climb mixture, richer than best power, to cruise mixture, leaner = than 50=20 degrees lean of peak power, quickly, so as not to spend many RPM at = (or even=20 near) best power. Or have one controller for takeoff and climb and the = other=20 for cruise.
 
Since intake air temp is the culprit, perhaps insulated the = intake=20 runners is in order. Or a blast tube blowing on them. Intake air temp = includes=20 heat of compression in the chamber. That is why boosted engines are = more=20 likely to detonate. That is also why they have an inter-cooler to = remove heat=20 from the intake air. That is also why they inject water at high boost = numbers.=20 Or water and alcohol in big radials at military power.
 
High compression rotors? more likely than lower compression = rotors.=20 (because the heat of compression is higher)
 
Ignition advance later (less likely) ignition advance sooner = (more=20 likely). Note that the controller takes out advance when the Lambda=20 sensor hears detonation.
 
Adjust advance to show some percentage = of RPM below=20 max for any situation. A 13B makes more power right up to 39-40 = degrees of=20 advance, but it adds a ton of extra heat along with a small amount of = extra=20 power. But power it does make, and if you just watch for more RPM as=20 you advance the timing, you will tune for way too much = advance, and=20 more heat than you can dispose of. 
 
Keep in mind that flame front speed in feet per second has a time = function. So?
 
Unless there is one of those emergencies where real short engine = life is=20 not going to be a factor, roll in that throttle slowly. Detonation is = more=20 likely at high load lower RPM, than at high load high RPM.
(remember dads pickup) The propeller is always in top gear.
 
 
We raced for years on 20-22 degrees total and made good power up = to 9,000=20 RPM. That is on crap for gas. On 100LL you can go well above that in a = 13B,=20 maybe 26-28 degrees. If you get a dose of car gas with alcohol in it, = remember=20 that for any situation it is leaner than 100% gasoline.  
 
I have fried more than a few of these. It got too expensive after = a while=20 so I quit doing it.
 
Lynn E. Hanover  
 
 
 
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