X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from m12.lax.untd.com ([64.136.30.75] verified) by logan.com (CommuniGate Pro SMTP 4.3.4) with SMTP id 985231 for flyrotary@lancaironline.net; Sun, 05 Jun 2005 10:08:23 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.136.30.75; envelope-from=alwick@juno.com Received: from m12.lax.untd.com (localhost [127.0.0.1]) by m12.lax.untd.com with SMTP id AABBLGB2SANAGDEJ for (sender ); Sun, 5 Jun 2005 07:07:12 -0700 (PDT) X-UNTD-OriginStamp: L941HVjjYzDhN3itp//mkGRPakqR9u0jEMDFiKBIxMk67fcZD8V0eg== Received: (from alwick@juno.com) by m12.lax.untd.com (jqueuemail) id KUQ3922H; Sun, 05 Jun 2005 07:06:55 PDT To: flyrotary@lancaironline.net Date: Sun, 5 Jun 2005 07:06:19 -0700 Subject: Re: [FlyRotary] Re: sand casting porosity Message-ID: <20050605.070625.2932.1.alwick@juno.com> X-Mailer: Juno 5.0.33 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary=--__JNP_000_46c2.3981.7035 X-Juno-Line-Breaks: 8-6,8,17-18,23-24,29-40,42-43,47,52-53,60,63,66-72,74-75,78,81,84,88-89,92-93,95,99-100,102-103,108-110,112-113,117-118,123-124,131-132,137-140,145-146,150-160,162,167,171-172,178,181-185,193-194,198-199,201-202,204-205,208-209,211-212,217,226-238,239-32767 From: al p wick X-ContentStamp: 67:33:4124150433 X-MAIL-INFO:396e6ed727ebe77ace1b47d77f470aab17c71e476afa8acb276a1ec76a0e6a8ea34b8b6b6eead70bd75f270f0acf7b0f7aeb02 X-UNTD-Peer-Info: 127.0.0.1|localhost|m12.lax.untd.com|alwick@juno.com This message is in MIME format. Since your mail reader does not understand this format, some or all of this message may not be legible. ----__JNP_000_46c2.3981.7035 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit There is a valuable lesson in problem solving here George. Very familiar pattern that really does apply to our rotary opportunities. Here's what I suggest. Don't tell your foundry guy you are discussing this with someone, that will just get him defensive. Instead, ask him:"How do you know the quantity of hydrogen in the alloy?". He's going to give you some theoretical based statement. So tell him"Pretend I'm the hydrogen fairy and the quantity just doubled in that bath, how would you know it's actually double?" You'll likely find he doesn't really know. He'll say "We could blah blah", but you ask him how often they MEASURE it and you'll start to appreciate they have no facts that prove hydrogen affects their casting process. It's all just theory. All of us tend to make decisions based on theory. An important key to success in problem solving is to just find a simple way to convert the theory to facts. This is rarely done. So when someone says:" I think this will make things better", you need to say :"Lets prove it....let's do the opposite and see if it gets worse!" So here's the deal, the foundry guy knows that the hydrogen level increases if you raise the temp of aluminum. That's a theory, it's true. But it's not significant. It's not the thing that affects the outcome. Just because something is true does not mean it's significant. You have to also test the idea for significance. Yes, familiar with nitrogen bubbling. -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 Sun, 5 Jun 2005 16:44:16 +1000 "George Lendich" writes: Al, All good info, it's good to talk to someone in the know. We have looked into the vent and riser potential and this has been optimised. Shrinkage defects can be eliminated with the right number of risers, in the right places especially in (as you say) thicker areas of thin castings. There is a strategy for eliminating Hydrogen from molten aluminium and that is to purge with Nitrogen ( Nitrogen bonds to hydrogen molecules - so I'm led to believe) through a ceramic wand ( immersed in the aluminium) for approx 20/30 minutes. Have you tried this method to eliminate the possibility of hydrogen? George ( down under) Oh, why didn't you say it was sand cast? 90% probability your porosity was shrinkage porosity, nothing to do with hydrogen. You sure want to avoid shrinkage in high stress areas. It's most likely to develop at inside corners near thick sections of casting. A good foundry can take action to minimize risk. Depends on details, but they can add vent, or riser as needed. We also used special sand for optimum qualities. But it would likely be unnecessary for your application. I conducted a number of statistically designed experiments to optimize the process. The goal being to reduce the likelihood of shrinkage defects. Total blast doing that kind of stuff. The nature of shrinkage porosity is that it comes and goes. So most foundries have hard time identifying contributing causes and optimizing. Lot of statistical noise. Good luck in your endeavor! -al wick On Sun, 5 Jun 2005 13:18:44 +1000 "George Lendich" writes: Al, There's reasons for my enquiry, which involves castings for Aviation use. My initial challenge was a multi use bellhousing to accommodate Aussie PSRU and that of Tracy's unit. It doubles as a engine mount and accommodates 5 ( maybe more) starter types and has to be light and strong. This requires strong thin wall castings. Usually thin walled castings require pressure injection technology. This is expensive and not cost effective because of the projected low demand, probably one to 2 hundred (at most), in an initial 2/3 year period. I settled on sand cast technology, but because of the thinness of some of the pattern, the aluminium is heated beyond it's recommended melting temps, to allow for easier running into thinner area before the temps are reduced by the sand casting process. The initial trial did identify obvious porosity, throughout the pattern although later trials, being carried out in the USA have yet to identify any significant reduction in the projected strength requirements. My development partner in the States, Butch as he is affectionally know throughout the Industry - is an Aviation Engineer. This design has been thoroughly tested on Finite Element Analysis, was CAD designed, with myself making the pattern to exacting tolerances, due to design restrictions and as Butch's exacting demands - he's a hard man to please! Although this took some considerable time ( approx 12 months) the pattern was completed and the prototypes done, by a very competent foundry. If I can quote Butch's recent remarks to me " The Bellhousing arrived safe and sound (Excellent Packaging)..... Very Robust to say the least, should be able to handle 800hp at least. It has been Ultrasonically analysed for density and voids, point load tested and torque twisting along both the horizontal and vertical axis. Needless to say it passed with "Flying Colours!! Do you see a pattern developing here? Research design and testing by competent authority!! - even the packaging! To a unenlightened onlooker, on initially first seeing this bellhousing, their response might be this design might not meet what we normally accept as a bell-shaped design i.e. form not meeting design requirements etc. etc. This is the type of development work carried out by many Experimental designers - but not necessarily communicated to everyone to this degree. I won't say this is true in all Rotary installations, but I will say there is much in the way of skilled and talented builders involved in the process of the Rotary development. The point I'm trying to make is, although I believe your risk analysis is valid, I believe it is only valid when the information you base your assessment is correct and complete. Often a valid assessment can be completely turned on it's head when seemingly correct information is found to be incomplete, therefore making the initial assessment completely useless. I believe some assertions, on this discussion group, have pointed to this possibility. BTW I'm on the look out for any good foundries around the East Coast Nth of Washington, who could carry out this Bellhousing work ' Cost Effectively', for the US market, if you know of any I would love to hear about it. One of the problems on supply to the USA, is the 'Tyranny of Distance'. George ( down under) I only did hydrogen experiments with permanent mold castings(thick wall parts), so unsure if it applies to other types. But the experiments were conclusive. Hydrogen was absolutely trivial. It was shrinkage porosity which dominates the mechanical properties. Hydrogen porosity develops round voids, shrinkage voids tear. I suspect the myth continues regarding hydrogen. I did those experiments over 10 years ago. It gave us huge advantage over competition. We focused on methods to reduce shrinkage defects. Ended up out performing our competition. That was a blast. I miss those challenges. -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 Sat, 4 Jun 2005 08:32:19 +1000 "George Lendich" writes: I've had a look at Al Wicks approach and for me it leaves a lot of unanswered questions. I have the benefit of being a ( now retired) Government Logistics manager, trained in Quality Assurance, Occupational Health and Safety, Risk management and of course procurement. I had a good deal of experience within the medical logistics field. This basic approach gives a basic guide provided you get your facts straight and work on with the right information - I can't see this being done with the Rotary. Perhaps he has done quite well with the Subaru - who would know. Al if your on here would you please elaborate on the statement on Aluminium - the information to me is that Hydrogen is indeed the major problem with non- injection cast aluminium. Especially if it involves elevated thin pour castings - the elevated temperature draws hydrogen from the air and releases it as bubbles in the aluminium, the higher the humidity the greater the chace of Hydrogen porosity. As we all know porosity is the primary cause of strength reduction in a cast aluminium piece. I understand there are other causes of porosity, but am unsure of what they all are. George ( down under) Ernest Christley wrote: Jim, Al is not following his own process (I think I alluded to this previously). First, you have to ask, "How many failures have accurred due to a faulty CAS?" That's a fair question. Do you know? Does anyone? If so, Who? Seems there was a thread around that just a month or two ago. Intuitively, I would say that CAS would be a single point of failure, important enough to be remediated. The text below is copy and pasted from http://www.maddyhome.com/canardpages/pages/alwick/risk.html The key phrase is the last sentence. We are going to do an FMEA. What is the goal we are trying to achieve with this process? It’s to make sure we place our efforts on the facets which need it. Put another way, it’s making sure we don’t waste time and effort on insignificant items, while ignoring the truly important items. There are only three pieces to the puzzle. In the case of CAS (just my guess) 1) If the component failed, how serious would that effect the airplane? catastrophic 2) What is the probability of the component failing? Undetermined. Start with doing some research at NAPA et al and repair shops around how many they sell. 3) What is the likelihood that you would notice the problem before failure? I'd guess very VERY remote. You may have heard statements like “You have to replace component x on your engine before installing into an airplane because it represents a single point failure”. Meaning that if x fails, there is no backup component. That statement is not meaningful until you assess all three questions above. Exactly. Al's question is "... to what extent are "we" using his methodology. My own guess would be "not much ...". Single point(s) of failure in Tracy's ignition (and fuel control) systems - if there are any - would be a case in point. As would redundant fuel pumps powered by a single source, and charging systems that are not sufficiently redundant and with appropriate indicators. If one DOES have a single point of failure (and there are inevitably many) we must be sure that that component is sufficiently robust to give us all confidence that it will NOT fail. >> Homepage: http://www.flyrotary.com/ >> Archive: http://lancaironline.net/lists/flyrotary/List.html -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 ----__JNP_000_46c2.3981.7035 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
There is a valuable lesson in problem solving here George. Very = familiar=20 pattern that really does apply to our rotary opportunities.
Here's what I suggest. Don't tell your foundry guy you are discussing = this=20 with someone, that will just get him defensive. Instead, ask him:"How = do=20 you know the quantity of hydrogen in the alloy?". He's going to give = you=20 some theoretical based statement. So tell him"Pretend I'm the hydrogen = fairy and=20 the quantity just doubled in that bath, how would you know it's actually=20 double?" You'll likely find he doesn't really know. He'll say "We could = blah=20 blah", but you ask him how often they MEASURE it and you'll start to = appreciate=20 they have no facts that prove hydrogen affects their casting process. It's = all=20 just theory.
 
All of us tend to make decisions based on theory. An important key to= =20 success in problem solving is to just find a simple way to convert the = theory to=20 facts. This is rarely done. So when someone says:" I think this will make = things=20 better", you need to say :"Lets prove it....let's do the opposite and see = if it=20 gets worse!"
 
So here's the deal, the foundry guy knows that the hydrogen level = increases=20 if you raise the temp of aluminum. That's a theory, it's true. But it's not= =20 significant. It's not the thing that affects the outcome. = Just=20 because something is true does not mean it's significant. You have to also test the idea for significance.
 
 
 Yes, familiar with nitrogen bubbling.

-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 Sun, 5 Jun 2005 16:44:16 +1000 "George Lendich" <lendich@optusnet.com.au>=20 writes:
Al,
All good info, it's good to talk to someone in the = know. We=20 have looked into the vent and riser potential and this has been= =20 optimised. Shrinkage defects can be eliminated with the right number of=20 risers, in the right places especially in (as you say) thicker areas of = thin=20 castings.
There is a strategy for eliminating Hydrogen from = molten=20 aluminium and that is to purge with Nitrogen ( Nitrogen bonds to hydrogen= =20 molecules - so I'm led to believe) through a ceramic wand ( immersed in = the=20 aluminium) for approx 20/30 minutes. Have you tried this method to = eliminate=20 the possibility of hydrogen? 
George ( down under)
Oh, why didn't you say it was sand cast? 90% probability your = porosity=20 was shrinkage porosity, nothing to do with hydrogen. You sure want to = avoid=20 shrinkage in high stress areas. It's most likely to develop at inside=20 corners near thick sections of casting. A good foundry can take action = to=20 minimize risk. Depends on details, but they can add vent, or riser as=20 needed. We also used special sand for optimum qualities. But it would = likely=20 be unnecessary for your application.
I conducted a number of statistically designed experiments to = optimize=20 the process. The goal being to reduce the likelihood of shrinkage = defects.=20 Total blast doing that kind of stuff.
The nature of shrinkage porosity is that it comes and goes. So = most=20 foundries have hard time identifying contributing causes and optimizing= . Lot=20 of statistical noise.
 
Good luck in your endeavor!
 
-al wick
 
 
On Sun, 5 Jun 2005 13:18:44 +1000 "George Lendich" <lendich@optusnet.com.au>= =20 writes:
Al,
There's reasons for my enquiry, which involves = castings=20 for Aviation use. My initial challenge was a multi use bellhousing to= =20 accommodate Aussie PSRU and that of Tracy's unit.
It doubles as a engine mount and = accommodates 5 (=20 maybe more) starter types and has to be light and strong. This = requires=20 strong thin wall castings.
Usually thin walled castings require pressure = injection=20 technology. This is expensive and not cost effective=20 because of the projected low demand, = probably one=20 to 2 hundred (at most), in an initial 2/3 year period.
I settled on sand cast technology, but = because of=20 the thinness of some of the pattern, the aluminium is heated beyond = it's=20 recommended melting temps, to allow for easier running into thinner = area=20 before the temps are reduced by the sand casting=20 process. 
 
The initial trial did identify obvious porosity,= =20 throughout the pattern although later trials, being carried out in = the USA=20 have yet to identify any significant reduction in the projected = strength=20 requirements.
 
My development partner in the States, Butch as he= is=20 affectionally know throughout the Industry - is an Aviation=20 Engineer.
This design has been thoroughly tested on Finite = Element=20 Analysis, was CAD designed, with myself making the pattern to = exacting=20 tolerances, due to design restrictions and as Butch's exacting = demands -=20 he's a hard man to please!
 
Although this took some considerable time ( = approx 12=20 months) the pattern was completed and the prototypes done, by a very= =20 competent foundry.
 
If I can quote Butch's recent remarks to me <= STRONG>"=20 The Bellhousing arrived safe and sound (Excellent Packaging)..... = Very=20 Robust to say the least, should be able to handle 800hp at least. It = has=20 been Ultrasonically analysed for density and voids, point load tested= and=20 torque twisting along both the horizontal and vertical=20 axis.
Needless to say it passed with "Flying=20 Colours!! 
 
Do you see a pattern developing here? Research = design=20 and testing by competent authority!! - even the=20 packaging!
 
To a unenlightened onlooker, on initially first = seeing=20 this bellhousing, their response might be this design might not = meet=20 what we normally accept as a bell-shaped design i.e. form not meeting= =20 design requirements etc. etc.
 
This is the type of development work carried out = by many=20 Experimental designers - but not necessarily communicated to = everyone=20 to this degree. I won't say this is true in all Rotary installations,= but=20 I will say there is much in the way of skilled and talented builders= =20 involved in the process of the Rotary development.
 
The point I'm trying to make is, although I = believe your=20 risk analysis is valid, I believe it is only valid when the = information=20 you base your assessment is correct and complete. Often a valid = assessment=20 can be completely turned on it's head when seemingly correct = information=20 is found to be incomplete, therefore making the initial assessment=20 completely useless. I believe some assertions, on this discussion = group,=20 have pointed to this possibility.
 
BTW I'm on the look out for any good = foundries=20 around  the East Coast Nth of Washington, who could carry out = this=20 Bellhousing work ' Cost Effectively',  for the US market, = if you=20 know of any I would love to hear about it. One of the problems = on=20 supply to the USA, is the 'Tyranny of Distance'.
George ( down under)
 
 
I only did hydrogen experiments with permanent=20 mold castings(thick wall parts), so unsure if it applies to other = types.=20 But the experiments were conclusive. Hydrogen was absolutely = trivial. It=20 was shrinkage porosity which dominates the mechanical properties.=20 Hydrogen porosity develops round voids, shrinkage voids tear.= =20  
 
I suspect the myth continues regarding hydrogen. I did those=20 experiments over 10 years ago. It gave us huge advantage over=20 competition. We focused on methods to reduce shrinkage defects. = Ended up=20 out performing our competition. That was a blast. I miss those=20 challenges.
 

-al wick
Artificial intelligence in cockpit, Cozy IV = powered=20 by stock Subaru 2.5
N9032U 200+ hours on engine/airframe from=20 Portland, Oregon
Prop construct, Subaru install, Risk assessment= ,=20 Glass panel design=20 info:
http://www.maddyhome.com/canardpages/pages/alwick/index.= html
 
 
On Sat, 4 Jun 2005 08:32:19 +1000 "George Lendich" <lendich@optusnet.com.au= >=20 writes:
I've had a look at Al Wicks approach and for = me it=20 leaves a lot of unanswered questions. I have the benefit of being= a (=20 now retired) Government Logistics manager, trained in = Quality=20 Assurance,  Occupational Health and Safety, Risk management = and=20 of course procurement. I had a good deal of experience within the= =20 medical logistics field.
This basic approach gives a basic guide= =20 provided you get your facts straight and work on with the right=20 information - I can't see this being done with the Rotary. = Perhaps he=20 has done quite well with the Subaru - who would know.
 
Al if your on here would you please elaborate= on the=20 statement on Aluminium - the information to me is that Hydrogen = is=20 indeed the major problem with non- injection cast aluminium.= =20 Especially if it involves elevated thin pour castings - the = elevated=20 temperature draws hydrogen from the air and releases it as = bubbles in=20 the aluminium, the higher the humidity the greater the chace of=20 Hydrogen porosity.
As we all know porosity is the primary cause = of=20 strength reduction in a cast aluminium piece. I understand there = are=20 other causes of porosity, but am unsure of what they all=20 are.
 
George ( down under)
Ernest=20 Christley wrote:
Jim, = Al is=20 not following his own process (I think I alluded to this=20 previously). First, you have to ask, "How many failures have= =20 accurred due to a faulty CAS?"  = That's a=20 fair question.  Do you know?  Does anyone?  If= so,=20 Who?  Seems there was a thread around that just a month = or=20 two ago.   Intuitively, I would say that CAS would be a= =20 single point of failure, important enough to be=20 remediated.  The text below is copy and pasted=20 from  http://www.maddyhome.com/canardpages/pages/alwick/risk.html= =20 The key phrase is the last sentence.

We are going to = do an=20 FMEA. What is the goal we are trying to achieve with this = process?=20 It=92s to make sure we place our efforts on the facets which = need=20 it. Put another way, it=92s making sure we don=92t waste time= and=20 effort on insignificant items, while ignoring the truly = important=20 items.

There are only three pieces to the=20 puzzle.   In the case of CAS = (just=20 my guess)

1) If the component failed, how = serious=20 would that effect the airplane?  catastrophic

2) What is the=20 probability of the component failing? Undetermined.  Start with doing some = research=20 at NAPA et al and repair shops around how many they=20 sell.

3) What is the likelihood that you would= =20 notice the problem before failure?  I'd=20 guess very VERY remote.

You may have heard=20 statements like =93You have to replace component x on your = engine=20 before installing into an airplane because it represents a = single=20 point failure=94. Meaning that if x fails, there is no backup= =20 component. That statement is not meaningful until you assess = all=20 three questions above.
Exactly.&= nbsp; Al's=20 question is "... to what extent are "we" using his=20 methodology.  My own guess would be "not much ...". = ;=20 Single point(s) of failure in Tracy's ignition (and fuel = control)=20 systems - if there are any - would be a case in point.  = As=20 would redundant fuel pumps powered by a single source, and=20 charging systems that are not sufficiently redundant and with= =20 appropriate indicators.  If one DOES have a single point= of=20 failure (and there are inevitably many) we must be sure that = that=20 component is sufficiently robust to give us all confidence = that it=20 will NOT fail.

>>  Homepage:  http://www.flyrotary.com/

>>  Archive:   http://lancaironline.net/lists/flyrotary/List.html
 
 

-al wick
Artificial intelligence= in=20 cockpit, Cozy IV powered by stock Subaru 2.5
N9032U 200+ hours on=20 engine/airframe from Portland, Oregon
Prop construct, Subaru install= ,=20 Risk assessment, Glass panel design=20 info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html<= BR>
 
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