Original Posted By: "Egan, John"
Pietenpol-List: Corvair engine disassembly
Re: Pietenpol-List: Corvair engine disassembly
Original Posted By: Egan, John
William Wynne has a new disassembly video (I have not seen it yet) on the Corvair.It is supposed to explain a lot.Barry ----- Original Message -----
William Wynne has a new disassembly video (I have not seen it yet) on the Corvair.It is supposed to explain a lot.Barry ----- Original Message -----
Pietenpol-List: Corvair engine disassembly
Original Posted By: Kip and Beth Gardner
Re: Pietenpol-List: Corvair engine disassembly
Original Posted By: Jim Ash
Re: Pietenpol-List: Corvair engine disassemblyKip:I am anything but an expert but a quick search turns up:from:http://www.maddyhome.com/corvairsrch/me ... D140"There has been considerable discussion on this matter on the list. The consensus is that it is best to avoid rotating the studs when disassemblingthe engine, and the reason has to do with how the studs were installed inthe first place. "and"at one time it was suggested that they all be turnedout and the case helicoiled to ensure tight threading of the studs into thecase. That advice has changed, because it's best to try to maintain the existing stud-to-case fit."and WW on the issue:http://www.maddyhome.com/corvairsrch/me ... t=3D73"The stock thread on these studs is not compatible withhelicoils. It is a special thread known as a 3/8NC5. The stock studs have a fairlyhigh tolerance for tool marks. Even studs with vise grip marks would pullover 9,500 pounds in tension before permanently deforming."some more postings of interest on the issue:http://www.maddyhome.com/corvairsrch/me ... ks:michael silvius________________________________________________________________________________Date: Tue, 7 Mar 2006 22:34:18 -0500 (GMT-05:00)
Re: Pietenpol-List: Corvair engine disassemblyKip:I am anything but an expert but a quick search turns up:from:http://www.maddyhome.com/corvairsrch/me ... D140"There has been considerable discussion on this matter on the list. The consensus is that it is best to avoid rotating the studs when disassemblingthe engine, and the reason has to do with how the studs were installed inthe first place. "and"at one time it was suggested that they all be turnedout and the case helicoiled to ensure tight threading of the studs into thecase. That advice has changed, because it's best to try to maintain the existing stud-to-case fit."and WW on the issue:http://www.maddyhome.com/corvairsrch/me ... t=3D73"The stock thread on these studs is not compatible withhelicoils. It is a special thread known as a 3/8NC5. The stock studs have a fairlyhigh tolerance for tool marks. Even studs with vise grip marks would pullover 9,500 pounds in tension before permanently deforming."some more postings of interest on the issue:http://www.maddyhome.com/corvairsrch/me ... ks:michael silvius________________________________________________________________________________Date: Tue, 7 Mar 2006 22:34:18 -0500 (GMT-05:00)
Re: Pietenpol-List: Corvair engine disassembly
Original Posted By: Jim Ash
Re: Pietenpol-List: Corvair engine disassembly
Original Posted By: Tim Willis
Re: Pietenpol-List: Corvair engine disassembly
Original Posted By: "MICHAEL SILVIUS"
Subject: Re: Pietenpol-List: Corvair engine disassemblyWW suggests in his manual that unless the studs turn out or are pulled out or damaged(rust) that they can be re-used in modest applications such as a pietenpol.The top row of studs you're talking about shouldn't turn out and shouldn'tbe damaged or rusted because they were continuously bathed in oil inside thehead. I have dissassembled several engines and the only studs which have turnedor been damaged in any way are the lower ones. Usually they're rusted prettybadly. To make sure if one turns or not, take a white out brush and brushon a mark on the outer part of the stud and engine case. The rocker studs inthe engines I've worked on have been pretty easy to remove without disturbingthe case / stud fit.I plan to use my upper studs but replace most if not all of my lowers and helicoilthe lowers as well.Lot's of opinions on this - do you have WW book? If not, get it, ask him questions...He's happy to answer them and see that things are done right.Tom B.________________________________________________________________________________
Subject: Re: Pietenpol-List: Corvair engine disassemblyWW suggests in his manual that unless the studs turn out or are pulled out or damaged(rust) that they can be re-used in modest applications such as a pietenpol.The top row of studs you're talking about shouldn't turn out and shouldn'tbe damaged or rusted because they were continuously bathed in oil inside thehead. I have dissassembled several engines and the only studs which have turnedor been damaged in any way are the lower ones. Usually they're rusted prettybadly. To make sure if one turns or not, take a white out brush and brushon a mark on the outer part of the stud and engine case. The rocker studs inthe engines I've worked on have been pretty easy to remove without disturbingthe case / stud fit.I plan to use my upper studs but replace most if not all of my lowers and helicoilthe lowers as well.Lot's of opinions on this - do you have WW book? If not, get it, ask him questions...He's happy to answer them and see that things are done right.Tom B.________________________________________________________________________________
Re: Pietenpol-List: Corvair engine disassembly
Original Posted By: "tmbrant1(at)netzero.com"
Re: Pietenpol-List: Corvair engine disassemblyokit apears that the links I used last night did not work.but if you go to go to:http://www.maddyhome.com/corvairsrch/index.jspand do a search on "cylinder head studs" it turns up a god bit of discussion onthe issue.I tend to go directly to WW's posts and then follow up by steping back to the postinghe is responding, or making refference to.On page 2 of the search: (# 41)Lon of Corvairunderground writes:++++++++++++++++++++++++1) The threads on the block ends are a bit unusual in that they areactually a form of self-tapping thread. All 12 studs on each side of the case were installed into pre-drilled holes in one gang operation at thefactory. What this means is that a std 3/8-16 thread is not exactly acorrect repair.It is not uncommon for attempted stud repairs to "go wrong". Part ofthis is because the original method of stud installation yields a studthat is normally quite secure in the block. Various attempts to remove a stud and re-install it (whether with an insert or just simply screwingback in) will almost never duplicate the same result. The factoryoversize studs were intended to be used where a stud had simplyunscrewed. In the case where a stud was actually stripped (or pulled)out the factory answer was to get another block, rather than repair.+++++++++++++++++++++++++++++++++++++regarding the removal of studs:specifically look at: WW's (#74 Apr 5, 2004)The Mother Of All Head Stud Posts he writes:++++++++++++++++++++++++++++++++++Typical SituationsQ: I disassembled my motor, and it came apart easily. Should I be worriedabout my studs? None of them pulled out of the case.A: No. In most cases, your studs would be perfectly fine. If you wish to check them, you can borrow one of the tool sets from us.Q: The upper row of nuts were rusted on my motor. I used a breaker bar andimpact wrench to take them off. Are my studs ok?A: A lot of our testing says they're junk, and here's why: A stock head nutcan only take about 55 foot pounds of torque before the threads rip out. Youcannot damage a stud by overtightening it with a stock head nut. However, if thetwo are rusted together, and you're using aggressive tools, the bond betweenthe rusty nut and stud can easily transmit several times this amount of torquein reverse. We've found almost no weakened lower row studs, however,virtually all the studs that have rusty tops pull like taffy, frequently stretching25-30/1000 more at the same level of torque as an undamaged stud. These studsare wounded by being removed with aggressive methods. If you put a wounded studback in, and simply put a piece of pipe on it and torque the nut, it willtorque to the 35 foot pounds, but you will be proving nothing. Such a weakenedstud will not exert the same clamping force on the head as the undamaged ones.Iwould suggest any stud that takes more than 50 foot pounds of torque inreverse be looked at very carefully. Many people have seen Grace disassemble engineswith 1/2" air impact gun. This said, she knows the trick of hitting ittighter for a moment and then reversing it. In either case, we now replace alltheupper studs in all of our production engines.Q: Should I use a stock or oversize stud if the stud unscrews from the case?A: It depends on the fit. I'm a big advocate of Loctite 620 and it does afantastic job of holding somewhat loose studs in place, even at engine operatingtemperatures. It seals the oil in the non blind holes also. I read one postwhere someone mentioned helicoiling a hole, torquing a stud into it and gettingdrag torque with a stock stud. As said previously, these are incompatible withhelicoils unless they're modified. Helicoiled holes will need Loctite 620 toseal them in place, otherwise the stud would turn all the way into the case.Q: The tops of my studs are rusty, but the nuts came off without twisting thestuds. Should I replace the studs?A: Maybe not. A method to consider is milling the pad on the head where thenut sits down 1/8" to get the new nut to operate entirely on the clean part ofthe threads. We do this on a stud by stud basis on some engines. This may beof particular interest to people building 3100s who wish to avoid any type ofmod to the base of the studs.I saw a note where someone was commenting that it would be nice if someonetested helicoils in the case, strength of studs, etc. Someone did this years agoin great detail. There is no need for people to reinvent the wheel on thissort of stuff, nor question my judgment. I tested to destruction every type ofstud and insert repair, every combination of fasteners and lubricants. If yougo back in the photos and look at my cam test rig, you'll notice that it isbuilt on a case that has 24 ripped out stud holes in it. I do not believe thatanyone else ever engaged in this type of testing, and correlated it to whatpeople in the field needed to know.++++++++++++++++++++++++++++++++on page 7 of the cylincer head studs search our friend Oscar Z in a posting listedas:corvaircraft: engine teardownmakes some of the salient points on the issue as well.regards:Michael SilviusScarborough, Maine________________________________________________________________________________
Re: Pietenpol-List: Corvair engine disassemblyokit apears that the links I used last night did not work.but if you go to go to:http://www.maddyhome.com/corvairsrch/index.jspand do a search on "cylinder head studs" it turns up a god bit of discussion onthe issue.I tend to go directly to WW's posts and then follow up by steping back to the postinghe is responding, or making refference to.On page 2 of the search: (# 41)Lon of Corvairunderground writes:++++++++++++++++++++++++1) The threads on the block ends are a bit unusual in that they areactually a form of self-tapping thread. All 12 studs on each side of the case were installed into pre-drilled holes in one gang operation at thefactory. What this means is that a std 3/8-16 thread is not exactly acorrect repair.It is not uncommon for attempted stud repairs to "go wrong". Part ofthis is because the original method of stud installation yields a studthat is normally quite secure in the block. Various attempts to remove a stud and re-install it (whether with an insert or just simply screwingback in) will almost never duplicate the same result. The factoryoversize studs were intended to be used where a stud had simplyunscrewed. In the case where a stud was actually stripped (or pulled)out the factory answer was to get another block, rather than repair.+++++++++++++++++++++++++++++++++++++regarding the removal of studs:specifically look at: WW's (#74 Apr 5, 2004)The Mother Of All Head Stud Posts he writes:++++++++++++++++++++++++++++++++++Typical SituationsQ: I disassembled my motor, and it came apart easily. Should I be worriedabout my studs? None of them pulled out of the case.A: No. In most cases, your studs would be perfectly fine. If you wish to check them, you can borrow one of the tool sets from us.Q: The upper row of nuts were rusted on my motor. I used a breaker bar andimpact wrench to take them off. Are my studs ok?A: A lot of our testing says they're junk, and here's why: A stock head nutcan only take about 55 foot pounds of torque before the threads rip out. Youcannot damage a stud by overtightening it with a stock head nut. However, if thetwo are rusted together, and you're using aggressive tools, the bond betweenthe rusty nut and stud can easily transmit several times this amount of torquein reverse. We've found almost no weakened lower row studs, however,virtually all the studs that have rusty tops pull like taffy, frequently stretching25-30/1000 more at the same level of torque as an undamaged stud. These studsare wounded by being removed with aggressive methods. If you put a wounded studback in, and simply put a piece of pipe on it and torque the nut, it willtorque to the 35 foot pounds, but you will be proving nothing. Such a weakenedstud will not exert the same clamping force on the head as the undamaged ones.Iwould suggest any stud that takes more than 50 foot pounds of torque inreverse be looked at very carefully. Many people have seen Grace disassemble engineswith 1/2" air impact gun. This said, she knows the trick of hitting ittighter for a moment and then reversing it. In either case, we now replace alltheupper studs in all of our production engines.Q: Should I use a stock or oversize stud if the stud unscrews from the case?A: It depends on the fit. I'm a big advocate of Loctite 620 and it does afantastic job of holding somewhat loose studs in place, even at engine operatingtemperatures. It seals the oil in the non blind holes also. I read one postwhere someone mentioned helicoiling a hole, torquing a stud into it and gettingdrag torque with a stock stud. As said previously, these are incompatible withhelicoils unless they're modified. Helicoiled holes will need Loctite 620 toseal them in place, otherwise the stud would turn all the way into the case.Q: The tops of my studs are rusty, but the nuts came off without twisting thestuds. Should I replace the studs?A: Maybe not. A method to consider is milling the pad on the head where thenut sits down 1/8" to get the new nut to operate entirely on the clean part ofthe threads. We do this on a stud by stud basis on some engines. This may beof particular interest to people building 3100s who wish to avoid any type ofmod to the base of the studs.I saw a note where someone was commenting that it would be nice if someonetested helicoils in the case, strength of studs, etc. Someone did this years agoin great detail. There is no need for people to reinvent the wheel on thissort of stuff, nor question my judgment. I tested to destruction every type ofstud and insert repair, every combination of fasteners and lubricants. If yougo back in the photos and look at my cam test rig, you'll notice that it isbuilt on a case that has 24 ripped out stud holes in it. I do not believe thatanyone else ever engaged in this type of testing, and correlated it to whatpeople in the field needed to know.++++++++++++++++++++++++++++++++on page 7 of the cylincer head studs search our friend Oscar Z in a posting listedas:corvaircraft: engine teardownmakes some of the salient points on the issue as well.regards:Michael SilviusScarborough, Maine________________________________________________________________________________
Re: Pietenpol-List: GN-1 vs. Piet Airfoil-- rephrase the Question
Original Posted By: Hans Vander Voort
Subject: Re: Pietenpol-List: Corvair engine disassemblymy upper and lower are reversed.. to add to your confusion________________________________________________________________________________Subject: Re: Pietenpol-List: GN-1 vs. Piet Airfoil-- rephrase the Question
Subject: Re: Pietenpol-List: Corvair engine disassemblymy upper and lower are reversed.. to add to your confusion________________________________________________________________________________Subject: Re: Pietenpol-List: GN-1 vs. Piet Airfoil-- rephrase the Question
Original Posted By: harvey rule
Tim,Isn't the GN airfoil a Piper Cub airfoil (USA 35-b)?Michael Shuck wrote a Airfoil analyses between Pietenpol and Piper.See the matronics archives or the File share list, Ken Chambers listed itthere in April of 2005.It does not address the stall-landing speed issue but is very interestingreading.My Pietenpol stalls at about 28 Mph. (on Pitot tube ASI)But how accurate is my ASI ?I have made my own Johnson type Air speed indicator.And also have a panel mounted ASI with the traditional Pitot tube.The Johnson type, I calibrated by sticking it out of the window of a car.The Pitot tube ASI is calibrated by the factory.They both read different.As does my GPS speed which is of course is measuring ground speed, but nonethe less averaging up wind and down wind speeds do not produce the samereadings as the ASI's either.But they are all within 10% of each other, which to me is OK.Long story short, Air Speed measuring accuracy is subject to instrumentused and slow speeds are difficult to measure, 25 Mph vs 35 Mph both arevery, very slow.I would consider the 35 Mph as minimum controllable airspeed and a roughguide for test flying your own Pietenpol.In normal flight I use a 55 Mph approach speed (on Base and Final) whichgives me a good glide (with part throttle) and good response over allcontrols.When 6 feet over the runway cut the power to idle and the speed bleeds offquickly, she settles down at around 30 Mph.Hans________________________________________________________________________________Date: Wed, 08 Mar 2006 12:20:51 -0500
Tim,Isn't the GN airfoil a Piper Cub airfoil (USA 35-b)?Michael Shuck wrote a Airfoil analyses between Pietenpol and Piper.See the matronics archives or the File share list, Ken Chambers listed itthere in April of 2005.It does not address the stall-landing speed issue but is very interestingreading.My Pietenpol stalls at about 28 Mph. (on Pitot tube ASI)But how accurate is my ASI ?I have made my own Johnson type Air speed indicator.And also have a panel mounted ASI with the traditional Pitot tube.The Johnson type, I calibrated by sticking it out of the window of a car.The Pitot tube ASI is calibrated by the factory.They both read different.As does my GPS speed which is of course is measuring ground speed, but nonethe less averaging up wind and down wind speeds do not produce the samereadings as the ASI's either.But they are all within 10% of each other, which to me is OK.Long story short, Air Speed measuring accuracy is subject to instrumentused and slow speeds are difficult to measure, 25 Mph vs 35 Mph both arevery, very slow.I would consider the 35 Mph as minimum controllable airspeed and a roughguide for test flying your own Pietenpol.In normal flight I use a 55 Mph approach speed (on Base and Final) whichgives me a good glide (with part throttle) and good response over allcontrols.When 6 feet over the runway cut the power to idle and the speed bleeds offquickly, she settles down at around 30 Mph.Hans________________________________________________________________________________Date: Wed, 08 Mar 2006 12:20:51 -0500
Re: Pietenpol-List: Piet vs. GN-1 airfoil
Original Posted By: Tim Willis
early Gn-1's used a piper cub wing. some still opt to do that but most use themodifed Piet airfoil that is shown in the plans. The differences are in theleading edge of the airfoil. the GN-1 uses a more bluntly rounded edge. otherthan that the profile is the same. wing spar locations and other structuraldimensions are different but the overall shape is very close to a Piet airfoilDJ VeghDir. of Web DevelopmentEditor - Animator - Digital ArtistLarry John Wright, Inc.1045 E. University Dr.Mesa, AZ 85203480.833.8111 - Office602.743.5768 - Mobile"The Nation's Number One Retail Advertising Agency"Achieving Big Time Results for Local and Regional Retailers- ----- Original Message -----
early Gn-1's used a piper cub wing. some still opt to do that but most use themodifed Piet airfoil that is shown in the plans. The differences are in theleading edge of the airfoil. the GN-1 uses a more bluntly rounded edge. otherthan that the profile is the same. wing spar locations and other structuraldimensions are different but the overall shape is very close to a Piet airfoilDJ VeghDir. of Web DevelopmentEditor - Animator - Digital ArtistLarry John Wright, Inc.1045 E. University Dr.Mesa, AZ 85203480.833.8111 - Office602.743.5768 - Mobile"The Nation's Number One Retail Advertising Agency"Achieving Big Time Results for Local and Regional Retailers- ----- Original Message -----