Original Posted By: "Jack Phillips"
Subject: Pietenpol-List: Piston burningI had a thought on the model A piston burning problem today. I spent 17years as a Diesel Mechanics instuctor. Most piston crown cooling is doneby the oil splash on the bottom of the piston crown.Most heavy duty diesel engines actually have nozzels that squirtpressure oil on the bottom of the piston crowns, if a nozzel ismisaligned they will burn a piston every time. With a splash oiledengine like the "A" heavily loaded like in a climb and in a nose highattitude maybe they are just not getting enough oil splash to cool thepiston crowns. A lean mixture would further aggrevate the situation.Just a thought that mike's comments about the Pabligas ( sp sorry) Pietgot me thinking about today. But I would be willig to bet it is at leasta contributing factor. Ed Grentzer________________________________________________________________________________
Pietenpol-List: Piston burning
RE: Pietenpol-List: Piston burning
Original Posted By: owner-pietenpol-list-server(at)matronics.com
I'm sure you're right, Ed. Another string of discussions currently going onconcerns changing an A-65 to an A-75 or A-80, and one of the big differencesis the pistons and the drilled connecting rods which squirt oil on theinside of the piston crown. The difference in the pistons is a web ofcooling fins on the inside to transfer the extra heat to that extra oil.Jack Phillips-----Original Message-----
I'm sure you're right, Ed. Another string of discussions currently going onconcerns changing an A-65 to an A-75 or A-80, and one of the big differencesis the pistons and the drilled connecting rods which squirt oil on theinside of the piston crown. The difference in the pistons is a web ofcooling fins on the inside to transfer the extra heat to that extra oil.Jack Phillips-----Original Message-----
RE: Pietenpol-List: Drilling perpendicular holes
Original Posted By: owner-pietenpol-list-server(at)matronics.com
That's the same technique I used and it works great. I used a 3x3 block ofsteel and put several different sizes in it.Fast and handy.CarlPlease visit my website atwww.megsinet.net/skycarl-----Original Message-----
That's the same technique I used and it works great. I used a 3x3 block ofsteel and put several different sizes in it.Fast and handy.CarlPlease visit my website atwww.megsinet.net/skycarl-----Original Message-----
Re: Pietenpol-List: Piston burning
Original Posted By: "Jack Phillips"
The A-80 is really not a viable option. It had higher compression, morepiston rings. It pretty much shook itself to pieces. Besides, it needs asmaller diameter prop to turn the higher RPMs needed to get the horsepower.Slow airplanes don't do well with small diameter props. To maximize thrust,you need the biggest prop possible turning at the slowest rpm possible.Think about how a helicopter with 100 HP can lift two people straight upwith a slow turning monster propeller.The A-75 is more viable but the pistons are getting hard to come by. Thecarb uses a 1-3/8" venturi instead of a 1-1/4" venturi. the jet isdifferent too.Again, to get the horsepower, it is necessary to turn higher rpms which isnot what you want.Chris BobkaMinneapolis----- Original Message -----
The A-80 is really not a viable option. It had higher compression, morepiston rings. It pretty much shook itself to pieces. Besides, it needs asmaller diameter prop to turn the higher RPMs needed to get the horsepower.Slow airplanes don't do well with small diameter props. To maximize thrust,you need the biggest prop possible turning at the slowest rpm possible.Think about how a helicopter with 100 HP can lift two people straight upwith a slow turning monster propeller.The A-75 is more viable but the pistons are getting hard to come by. Thecarb uses a 1-3/8" venturi instead of a 1-1/4" venturi. the jet isdifferent too.Again, to get the horsepower, it is necessary to turn higher rpms which isnot what you want.Chris BobkaMinneapolis----- Original Message -----
Re: Pietenpol-List: Piston burning
Original Posted By: "Ed G."
Put a Model "B" crank in the A. It is drilled for full pressure oiling.----- Original Message -----
Put a Model "B" crank in the A. It is drilled for full pressure oiling.----- Original Message -----
Re: Pietenpol-List: Piston burning
Original Posted By: "Christian Bobka"
Chris,I am the fifth owner of a GN-1 powered by an A-80turning a 69 x 39 McCauley metal prop.The McCauley was trimmed down to 69" becauseof a prop strike on another airplane. Then it wasinstalled on the GN-1. The owner used the planeto deliver newspapers to rural areas of SouthTexas.I have been seriously thinking replacing the metalprop with a new 72 x 42 wooden prop. I have a videoof the airplane with two large men (previous ownerswho were over 200 pounds each) easily taking offfrom a small field. The plane was originally builtwith a 72 x 42 wooden prop but was replaced withthe McCauley prop by the next owner.Reading your post, you are saying the A-80 performsbetter with a smaller diameter propeller. What sizewould you recommend? I really don't think I am getting80 horses out of it. The tachs are not that accurate.Thanks.Mike KingGN-177MKDallasI have an A-80 in my GN-1. I am the fifth owner----- Original Message -----
Chris,I am the fifth owner of a GN-1 powered by an A-80turning a 69 x 39 McCauley metal prop.The McCauley was trimmed down to 69" becauseof a prop strike on another airplane. Then it wasinstalled on the GN-1. The owner used the planeto deliver newspapers to rural areas of SouthTexas.I have been seriously thinking replacing the metalprop with a new 72 x 42 wooden prop. I have a videoof the airplane with two large men (previous ownerswho were over 200 pounds each) easily taking offfrom a small field. The plane was originally builtwith a 72 x 42 wooden prop but was replaced withthe McCauley prop by the next owner.Reading your post, you are saying the A-80 performsbetter with a smaller diameter propeller. What sizewould you recommend? I really don't think I am getting80 horses out of it. The tachs are not that accurate.Thanks.Mike KingGN-177MKDallasI have an A-80 in my GN-1. I am the fifth owner----- Original Message -----
> > Pietenpol-List: Piston burning
Original Posted By: mboynton(at)excite.com
Re: Pietenpol-List: Piston burning
Original Posted By: "Mike King"
Use the longest prop that give you good clearance and the tip speed remainsabout 90% of sound. You control the rpm possible by the selection of theprop pitch. That is the quick and dirty prop selection.If you feel you aren't getting full power out of your A-80 then have thepitch of your prop reduced. This is easy if it is metal. Your should seeat full throttle cruise about red line which is listed by Continental as2700 rpm at sea level. If you can't get 2700 and you are at a low altitudelike 1000 msl then you have too much pitch. If you get more rpm then itwill climb better but you will have to run higher rpm for cruise.----- Original Message -----
Use the longest prop that give you good clearance and the tip speed remainsabout 90% of sound. You control the rpm possible by the selection of theprop pitch. That is the quick and dirty prop selection.If you feel you aren't getting full power out of your A-80 then have thepitch of your prop reduced. This is easy if it is metal. Your should seeat full throttle cruise about red line which is listed by Continental as2700 rpm at sea level. If you can't get 2700 and you are at a low altitudelike 1000 msl then you have too much pitch. If you get more rpm then itwill climb better but you will have to run higher rpm for cruise.----- Original Message -----
Re: Pietenpol-List: Piston burning
Original Posted By: Cy Galley
The "B" is not drilled. It does however have pressure oiled mains. The crankis large enough to have it drilled. I can send photo's and a description tothose interested off of the list. I also agree that the Ford engines aresuitable but they need mods. Many repro pistons sold to fit are cast slottedskirt pistons. They have been known to fail! I had that happen this summerto my Model AA truck. Some folks have been fitting pistons from small blockV8 engines. They are cam ground and usually forged. The cam ground fitallows better skirt cooling.The comments about large props and slow engines are right. The Fords are 200cu in stock and produce peak torque at only 1000 rpm.the A was rated at 40 hp and the B with a tougher crank was turned faster toproduce 50 hp. The limiting factor for getting more out of the Fords isintake induction design. Flat heads just don't breath well.John McOil cooling is a great idea but fuel mixture is equally important.----- Original Message -----
The "B" is not drilled. It does however have pressure oiled mains. The crankis large enough to have it drilled. I can send photo's and a description tothose interested off of the list. I also agree that the Ford engines aresuitable but they need mods. Many repro pistons sold to fit are cast slottedskirt pistons. They have been known to fail! I had that happen this summerto my Model AA truck. Some folks have been fitting pistons from small blockV8 engines. They are cam ground and usually forged. The cam ground fitallows better skirt cooling.The comments about large props and slow engines are right. The Fords are 200cu in stock and produce peak torque at only 1000 rpm.the A was rated at 40 hp and the B with a tougher crank was turned faster toproduce 50 hp. The limiting factor for getting more out of the Fords isintake induction design. Flat heads just don't breath well.John McOil cooling is a great idea but fuel mixture is equally important.----- Original Message -----
Re: Pietenpol-List: Piston burning
Original Posted By: "Mike King"
Mike,If you turn up to the full rated rpm of the A-80 which is 2700, then (at sealevel) you are making 80 horsepower. Period. Now, the horspower needs tobe converted into thrust. This must be done as efficiently as possible. Itis all a matter of how much air mass can be pulled from in front of the propdisc, and pushed behind it. Imagine a cylinder of air that is being movedfrom front to back at 90 mph which is 132 feet per second. If the prop is78 inches in diameter (6.5 feet), then the cylinder's volume is(6.5/2)(6.5/2)(3.14)(132) = 4378 cubic feet moved in a second. If you had a66 inch diamter prop (5.5 feet), then the volume would be 3134 cubic feetmoved in a second. Just a foot difference in prop diameter makes for a hugedifference in the amount of air the prop can move behind it at a givenairspeed. The larger diameter prop compared to the small diameter prop hasless interference from the nose of the airplane because more of the discarea is unperturbed by structure behind it. Also, the part of the propellerthat does most of the work is the outer half of the blade because thecorrect airfoil shape near the hub is less important than strengthconsiderations near the hub.Picking a prop is black magic and voodoo. Even the pros will trade outloaner props til you find one that you like and then they will make a copyof it for you.As Cy Galley said: get the biggest prop you can considering groundclearance and tip speed (90% of sonic). then try out different pitchesuntil you can get 2700 rpm at wide open throttle at or near sea level. Thatis how you find the best prop for your ship. Sure, many props will work okbut they are not the optimum.I usually like to get a little more than rated rpm in level flight (like2750 if I had an A-80). This makes for a lower cruising speed (5 mph) (suboptimum) but for more sprightly climb and takeoff performance.Maybe Cy Galley can steer you toward Eric Clutton and his book on propmaking (and other useful stuff).Comments Cy?chris bobkaMinneapolisEAA tech counselor----- Original Message -----
Mike,If you turn up to the full rated rpm of the A-80 which is 2700, then (at sealevel) you are making 80 horsepower. Period. Now, the horspower needs tobe converted into thrust. This must be done as efficiently as possible. Itis all a matter of how much air mass can be pulled from in front of the propdisc, and pushed behind it. Imagine a cylinder of air that is being movedfrom front to back at 90 mph which is 132 feet per second. If the prop is78 inches in diameter (6.5 feet), then the cylinder's volume is(6.5/2)(6.5/2)(3.14)(132) = 4378 cubic feet moved in a second. If you had a66 inch diamter prop (5.5 feet), then the volume would be 3134 cubic feetmoved in a second. Just a foot difference in prop diameter makes for a hugedifference in the amount of air the prop can move behind it at a givenairspeed. The larger diameter prop compared to the small diameter prop hasless interference from the nose of the airplane because more of the discarea is unperturbed by structure behind it. Also, the part of the propellerthat does most of the work is the outer half of the blade because thecorrect airfoil shape near the hub is less important than strengthconsiderations near the hub.Picking a prop is black magic and voodoo. Even the pros will trade outloaner props til you find one that you like and then they will make a copyof it for you.As Cy Galley said: get the biggest prop you can considering groundclearance and tip speed (90% of sonic). then try out different pitchesuntil you can get 2700 rpm at wide open throttle at or near sea level. Thatis how you find the best prop for your ship. Sure, many props will work okbut they are not the optimum.I usually like to get a little more than rated rpm in level flight (like2750 if I had an A-80). This makes for a lower cruising speed (5 mph) (suboptimum) but for more sprightly climb and takeoff performance.Maybe Cy Galley can steer you toward Eric Clutton and his book on propmaking (and other useful stuff).Comments Cy?chris bobkaMinneapolisEAA tech counselor----- Original Message -----
Re: Pietenpol-List: Piston burning
Original Posted By: "Christian Bobka"
Sounds good to me. One warning... Static rpm is very deceptive. It is levelflight rpms that Chris and I have been talking about.----- Original Message -----
Sounds good to me. One warning... Static rpm is very deceptive. It is levelflight rpms that Chris and I have been talking about.----- Original Message -----
> > > Pietenpol-List: Piston burning
Original Posted By: "Ignitor"