Original Posted By: steve(at)byu.edu
To all,Last night I re-read B.H.P.'s article on the corvair conversion. In oneparagraph he states three different Max. full throttle RPM acchievements.What gives? Does anyone with the article understand what he was saying. TheRPMs he listed were 2600, 2900, and 3300. How can he acchieve threedifferent maximums, unless he changed something and didn't change hisarticle? All this acchieved with the Tilotson carb which he admitted was toosmall and a larger one should be used. At 3300 he managed 120 MPH. He musthave had some pitch on that prop., and if he did how could he have gotten3300 RPM. It doesn't make any engineering sense to me. Perhaps someone canenlighten us.A.O.G.Domenic________________________________________________________________________________
Pietenpol-List: Bernie's article
Pietenpol-List: Re: Bernie's article
Original Posted By: John Greenlee
Subject: Pietenpol-List: Re: Bernie's article>Domenic,>>I'm not sure of Bernie's testing schedule, but this may help.>Engine rpm is related to prop pitch and total output in the same way that acars>gearing and rpm go together. You can't "lug" the engine and you can't>over-speed it and get good results.>Think of drive reduction units as the equivelant of long crank throws andnarrow>cylinders. They are essentially the same, a larger mechanical advantage>operating over a longer time.>A Ford "A" motor has a long(er) throw, and operates happily at a lowerspeed>with more torque and less horsepower than the Corvair. Intake efficiency,>combustion chamber design and compression ratio also affect the mix, so>everybody lay off me with the flames okay?>A Corvair has a shorter throw (and other differences) and is happy at ahigher>speed.>The Corvair would "lug" the big "A" prop and not perform worth beans. Youcan>fix this by reduction gearing (been done but costly and heavy) or using a>smaller prop direct allowing a higher rpm to get into the more efficientrpms>for the engine.>The smaller prop then runs faster and moves a smaller disc of air morequickly>to produce a somewhat more total thrust.>Again, you allow the engine to run at an efficient speed and allow somemethod>of mechanical advantage... crank stroke, reduction gearing or prop speedto put>the HP into the slipstream.>Bernie found that shorter props and higher rpm allowed the Corvair to runat>it's design speed, about twice the "A"'s and put out close to it's rated>horsepower (some say 95, some 110, I'd guess about 65 or 70 myself).>The game is to allow the engine to run at it's more efficient speed withoutthe>prop tips exceeding mach 1 at the given altitude and speed. This is acritical>limit as if the prop exceeds this factor a bunch of the generated HP starts>going not into forward motion, but into the producton of airport reduction>noises!>Bernie reduced the prop lengths on his Corvairs (and gradually increasedrpms)>until he got some damn decent results..>Today, 3300 to 4000 rpm sounds about right to me for the Corvair. Mightmake>sense to look at three bladed props too, but I'm not too happy about the>esthetics and they are difficult to carve in the backyard garage.>Bottom line is that Bernie's Corvair motor represented a real advance inpiston>engine efficiency that was later picked up by generations of VW poweredSonerai,>Volksplanes, KR's and a bunch of new NASA turbine ships with short, weird>looking props.>Bernie did it all. Had all the t-shirts, went there, did all that stuff.>>LLN>>BELLISSIMO, DOMENIC wrote:>>> To all,>>>> Last night I re-read B.H.P.'s article on the corvair conversion. In one>> paragraph he states three different Max. full throttle RPM acchievements.>> What gives? Does anyone with the article understand what he was saying.The>> RPMs he listed were 2600, 2900, and 3300. How can he acchieve three>> different maximums, unless he changed something and didn't change his>> article? All this acchieved with the Tilotson carb which he admitted wastoo>> small and a larger one should be used. At 3300 he managed 120 MPH. Hemust>> have had some pitch on that prop., and if he did how could he have gotten>> 3300 RPM. It doesn't make any engineering sense to me. Perhaps someonecan>> enlighten us.>>>> A.O.G.>> Domenic>>________________________________________________________________________________
Subject: Pietenpol-List: Re: Bernie's article>Domenic,>>I'm not sure of Bernie's testing schedule, but this may help.>Engine rpm is related to prop pitch and total output in the same way that acars>gearing and rpm go together. You can't "lug" the engine and you can't>over-speed it and get good results.>Think of drive reduction units as the equivelant of long crank throws andnarrow>cylinders. They are essentially the same, a larger mechanical advantage>operating over a longer time.>A Ford "A" motor has a long(er) throw, and operates happily at a lowerspeed>with more torque and less horsepower than the Corvair. Intake efficiency,>combustion chamber design and compression ratio also affect the mix, so>everybody lay off me with the flames okay?>A Corvair has a shorter throw (and other differences) and is happy at ahigher>speed.>The Corvair would "lug" the big "A" prop and not perform worth beans. Youcan>fix this by reduction gearing (been done but costly and heavy) or using a>smaller prop direct allowing a higher rpm to get into the more efficientrpms>for the engine.>The smaller prop then runs faster and moves a smaller disc of air morequickly>to produce a somewhat more total thrust.>Again, you allow the engine to run at an efficient speed and allow somemethod>of mechanical advantage... crank stroke, reduction gearing or prop speedto put>the HP into the slipstream.>Bernie found that shorter props and higher rpm allowed the Corvair to runat>it's design speed, about twice the "A"'s and put out close to it's rated>horsepower (some say 95, some 110, I'd guess about 65 or 70 myself).>The game is to allow the engine to run at it's more efficient speed withoutthe>prop tips exceeding mach 1 at the given altitude and speed. This is acritical>limit as if the prop exceeds this factor a bunch of the generated HP starts>going not into forward motion, but into the producton of airport reduction>noises!>Bernie reduced the prop lengths on his Corvairs (and gradually increasedrpms)>until he got some damn decent results..>Today, 3300 to 4000 rpm sounds about right to me for the Corvair. Mightmake>sense to look at three bladed props too, but I'm not too happy about the>esthetics and they are difficult to carve in the backyard garage.>Bottom line is that Bernie's Corvair motor represented a real advance inpiston>engine efficiency that was later picked up by generations of VW poweredSonerai,>Volksplanes, KR's and a bunch of new NASA turbine ships with short, weird>looking props.>Bernie did it all. Had all the t-shirts, went there, did all that stuff.>>LLN>>BELLISSIMO, DOMENIC wrote:>>> To all,>>>> Last night I re-read B.H.P.'s article on the corvair conversion. In one>> paragraph he states three different Max. full throttle RPM acchievements.>> What gives? Does anyone with the article understand what he was saying.The>> RPMs he listed were 2600, 2900, and 3300. How can he acchieve three>> different maximums, unless he changed something and didn't change his>> article? All this acchieved with the Tilotson carb which he admitted wastoo>> small and a larger one should be used. At 3300 he managed 120 MPH. Hemust>> have had some pitch on that prop., and if he did how could he have gotten>> 3300 RPM. It doesn't make any engineering sense to me. Perhaps someonecan>> enlighten us.>>>> A.O.G.>> Domenic>>________________________________________________________________________________
Pietenpol-List: Re: Bernie's article
Original Posted By: Alan Laudani
Domenic,I'm not sure of Bernie's testing schedule, but this may help.Engine rpm is related to prop pitch and total output in the same way that a carsgearing and rpm go together. You can't "lug" the engine and you can'tover-speed it and get good results.Think of drive reduction units as the equivelant of long crank throws and narrowcylinders. They are essentially the same, a larger mechanical advantageoperating over a longer time.A Ford "A" motor has a long(er) throw, and operates happily at a lower speedwith more torque and less horsepower than the Corvair. Intake efficiency,combustion chamber design and compression ratio also affect the mix, soeverybody lay off me with the flames okay?A Corvair has a shorter throw (and other differences) and is happy at a higherspeed.The Corvair would "lug" the big "A" prop and not perform worth beans. You canfix this by reduction gearing (been done but costly and heavy) or using asmaller prop direct allowing a higher rpm to get into the more efficient rpmsfor the engine.The smaller prop then runs faster and moves a smaller disc of air more quicklyto produce a somewhat more total thrust.Again, you allow the engine to run at an efficient speed and allow some methodof mechanical advantage... crank stroke, reduction gearing or prop speed to putthe HP into the slipstream.Bernie found that shorter props and higher rpm allowed the Corvair to run atit's design speed, about twice the "A"'s and put out close to it's ratedhorsepower (some say 95, some 110, I'd guess about 65 or 70 myself).The game is to allow the engine to run at it's more efficient speed without theprop tips exceeding mach 1 at the given altitude and speed. This is a criticallimit as if the prop exceeds this factor a bunch of the generated HP startsgoing not into forward motion, but into the producton of airport reductionnoises!Bernie reduced the prop lengths on his Corvairs (and gradually increased rpms)until he got some damn decent results..Today, 3300 to 4000 rpm sounds about right to me for the Corvair. Might makesense to look at three bladed props too, but I'm not too happy about theesthetics and they are difficult to carve in the backyard garage.Bottom line is that Bernie's Corvair motor represented a real advance in pistonengine efficiency that was later picked up by generations of VW powered Sonerai,Volksplanes, KR's and a bunch of new NASA turbine ships with short, weirdlooking props.Bernie did it all. Had all the t-shirts, went there, did all that stuff.LLNBELLISSIMO, DOMENIC wrote:> To all,>> Last night I re-read B.H.P.'s article on the corvair conversion. In one> paragraph he states three different Max. full throttle RPM acchievements.> What gives? Does anyone with the article understand what he was saying. The> RPMs he listed were 2600, 2900, and 3300. How can he acchieve three> different maximums, unless he changed something and didn't change his> article? All this acchieved with the Tilotson carb which he admitted was too> small and a larger one should be used. At 3300 he managed 120 MPH. He must> have had some pitch on that prop., and if he did how could he have gotten> 3300 RPM. It doesn't make any engineering sense to me. Perhaps someone can> enlighten us.>> A.O.G.> Domenic________________________________________________________________________________
Domenic,I'm not sure of Bernie's testing schedule, but this may help.Engine rpm is related to prop pitch and total output in the same way that a carsgearing and rpm go together. You can't "lug" the engine and you can'tover-speed it and get good results.Think of drive reduction units as the equivelant of long crank throws and narrowcylinders. They are essentially the same, a larger mechanical advantageoperating over a longer time.A Ford "A" motor has a long(er) throw, and operates happily at a lower speedwith more torque and less horsepower than the Corvair. Intake efficiency,combustion chamber design and compression ratio also affect the mix, soeverybody lay off me with the flames okay?A Corvair has a shorter throw (and other differences) and is happy at a higherspeed.The Corvair would "lug" the big "A" prop and not perform worth beans. You canfix this by reduction gearing (been done but costly and heavy) or using asmaller prop direct allowing a higher rpm to get into the more efficient rpmsfor the engine.The smaller prop then runs faster and moves a smaller disc of air more quicklyto produce a somewhat more total thrust.Again, you allow the engine to run at an efficient speed and allow some methodof mechanical advantage... crank stroke, reduction gearing or prop speed to putthe HP into the slipstream.Bernie found that shorter props and higher rpm allowed the Corvair to run atit's design speed, about twice the "A"'s and put out close to it's ratedhorsepower (some say 95, some 110, I'd guess about 65 or 70 myself).The game is to allow the engine to run at it's more efficient speed without theprop tips exceeding mach 1 at the given altitude and speed. This is a criticallimit as if the prop exceeds this factor a bunch of the generated HP startsgoing not into forward motion, but into the producton of airport reductionnoises!Bernie reduced the prop lengths on his Corvairs (and gradually increased rpms)until he got some damn decent results..Today, 3300 to 4000 rpm sounds about right to me for the Corvair. Might makesense to look at three bladed props too, but I'm not too happy about theesthetics and they are difficult to carve in the backyard garage.Bottom line is that Bernie's Corvair motor represented a real advance in pistonengine efficiency that was later picked up by generations of VW powered Sonerai,Volksplanes, KR's and a bunch of new NASA turbine ships with short, weirdlooking props.Bernie did it all. Had all the t-shirts, went there, did all that stuff.LLNBELLISSIMO, DOMENIC wrote:> To all,>> Last night I re-read B.H.P.'s article on the corvair conversion. In one> paragraph he states three different Max. full throttle RPM acchievements.> What gives? Does anyone with the article understand what he was saying. The> RPMs he listed were 2600, 2900, and 3300. How can he acchieve three> different maximums, unless he changed something and didn't change his> article? All this acchieved with the Tilotson carb which he admitted was too> small and a larger one should be used. At 3300 he managed 120 MPH. He must> have had some pitch on that prop., and if he did how could he have gotten> 3300 RPM. It doesn't make any engineering sense to me. Perhaps someone can> enlighten us.>> A.O.G.> Domenic________________________________________________________________________________
Pietenpol-List: Re: Bernie's article
Original Posted By: Larry Neal
Good a.m. guys,My limited understanding of aerodynamics adds this bit of info:Draggy airframes like Pietenpols, biplanes, and WW I fighters work betterwith gosh-awful long props turning low rpms. Clean slick designs likeNemesis like short props turning fast. Therefore, the Corvair and VW arebest at home in a faster airplane. The Corvair will fly the Piet finebecause it has an overabundance of power relative to what is necessary.I've always wondered how a Corvair would work out in a Taylor Titch(designed for an 85 Cont.)I understand some of the rotaries from WWI turned only maybe 1500 rpm -- butmade a BUNCH of thrust with the big long paddle props attached.An engineer could take what I just said and put it into some sort oftechnical speech. He would sound more intelligent than I but would probablyagree with what preceeds.John-----Original Message-----
Good a.m. guys,My limited understanding of aerodynamics adds this bit of info:Draggy airframes like Pietenpols, biplanes, and WW I fighters work betterwith gosh-awful long props turning low rpms. Clean slick designs likeNemesis like short props turning fast. Therefore, the Corvair and VW arebest at home in a faster airplane. The Corvair will fly the Piet finebecause it has an overabundance of power relative to what is necessary.I've always wondered how a Corvair would work out in a Taylor Titch(designed for an 85 Cont.)I understand some of the rotaries from WWI turned only maybe 1500 rpm -- butmade a BUNCH of thrust with the big long paddle props attached.An engineer could take what I just said and put it into some sort oftechnical speech. He would sound more intelligent than I but would probablyagree with what preceeds.John-----Original Message-----
Pietenpol-List: Re: Bernie's article
Original Posted By: Michael King
Domenic,I'm not sure of Bernie's testing schedule, but this may help.Engine rpm is related to prop pitch and total output in the same way that acarsgearing and rpm go together. You can't "lug" the engine and you can'tover-speed it and get good results.Think of drive reduction units as the equivelant of long crank throws andnarrowcylinders. They are essentially the same, a larger mechanical advantageoperating over a longer time.A Ford "A" motor has a long(er) throw, and operates happily at a lower speedwith more torque and less horsepower than the Corvair. Intake efficiency,combustion chamber design and compression ratio also affect the mix, soeverybody lay off me with the flames okay?A Corvair has a shorter throw (and other differences) and is happy at ahigherspeed.The Corvair would "lug" the big "A" prop and not perform worth beans. Youcanfix this by reduction gearing (been done but costly and heavy) or using asmaller prop direct allowing a higher rpm to get into the more efficientrpmsfor the engine.The smaller prop then runs faster and moves a smaller disc of air morequicklyto produce a somewhat more total thrust.Again, you allow the engine to run at an efficient speed and allow somemethodof mechanical advantage... crank stroke, reduction gearing or prop speed toputthe HP into the slipstream.Bernie found that shorter props and higher rpm allowed the Corvair to run atit's design speed, about twice the "A"'s and put out close to it's ratedhorsepower (some say 95, some 110, I'd guess about 65 or 70 myself).The game is to allow the engine to run at it's more efficient speed withouttheprop tips exceeding mach 1 at the given altitude and speed. This is acriticallimit as if the prop exceeds this factor a bunch of the generated HP startsgoing not into forward motion, but into the producton of airport reductionnoises!Bernie reduced the prop lengths on his Corvairs (and gradually increasedrpms)until he got some damn decent results..Today, 3300 to 4000 rpm sounds about right to me for the Corvair. Mightmakesense to look at three bladed props too, but I'm not too happy about theesthetics and they are difficult to carve in the backyard garage.Bottom line is that Bernie's Corvair motor represented a real advance inpistonengine efficiency that was later picked up by generations of VW poweredSonerai,Volksplanes, KR's and a bunch of new NASA turbine ships with short, weirdlooking props.Bernie did it all. Had all the t-shirts, went there, did all that stuff.LLNBELLISSIMO, DOMENIC wrote:> To all,>> Last night I re-read B.H.P.'s article on the corvair conversion. In one> paragraph he states three different Max. full throttle RPM acchievements.> What gives? Does anyone with the article understand what he was saying.The> RPMs he listed were 2600, 2900, and 3300. How can he acchieve three> different maximums, unless he changed something and didn't change his> article? All this acchieved with the Tilotson carb which he admitted wastoo> small and a larger one should be used. At 3300 he managed 120 MPH. He must> have had some pitch on that prop., and if he did how could he have gotten> 3300 RPM. It doesn't make any engineering sense to me. Perhaps someone can> enlighten us.>> A.O.G.> Domenic________________________________________________________________________________
Domenic,I'm not sure of Bernie's testing schedule, but this may help.Engine rpm is related to prop pitch and total output in the same way that acarsgearing and rpm go together. You can't "lug" the engine and you can'tover-speed it and get good results.Think of drive reduction units as the equivelant of long crank throws andnarrowcylinders. They are essentially the same, a larger mechanical advantageoperating over a longer time.A Ford "A" motor has a long(er) throw, and operates happily at a lower speedwith more torque and less horsepower than the Corvair. Intake efficiency,combustion chamber design and compression ratio also affect the mix, soeverybody lay off me with the flames okay?A Corvair has a shorter throw (and other differences) and is happy at ahigherspeed.The Corvair would "lug" the big "A" prop and not perform worth beans. Youcanfix this by reduction gearing (been done but costly and heavy) or using asmaller prop direct allowing a higher rpm to get into the more efficientrpmsfor the engine.The smaller prop then runs faster and moves a smaller disc of air morequicklyto produce a somewhat more total thrust.Again, you allow the engine to run at an efficient speed and allow somemethodof mechanical advantage... crank stroke, reduction gearing or prop speed toputthe HP into the slipstream.Bernie found that shorter props and higher rpm allowed the Corvair to run atit's design speed, about twice the "A"'s and put out close to it's ratedhorsepower (some say 95, some 110, I'd guess about 65 or 70 myself).The game is to allow the engine to run at it's more efficient speed withouttheprop tips exceeding mach 1 at the given altitude and speed. This is acriticallimit as if the prop exceeds this factor a bunch of the generated HP startsgoing not into forward motion, but into the producton of airport reductionnoises!Bernie reduced the prop lengths on his Corvairs (and gradually increasedrpms)until he got some damn decent results..Today, 3300 to 4000 rpm sounds about right to me for the Corvair. Mightmakesense to look at three bladed props too, but I'm not too happy about theesthetics and they are difficult to carve in the backyard garage.Bottom line is that Bernie's Corvair motor represented a real advance inpistonengine efficiency that was later picked up by generations of VW poweredSonerai,Volksplanes, KR's and a bunch of new NASA turbine ships with short, weirdlooking props.Bernie did it all. Had all the t-shirts, went there, did all that stuff.LLNBELLISSIMO, DOMENIC wrote:> To all,>> Last night I re-read B.H.P.'s article on the corvair conversion. In one> paragraph he states three different Max. full throttle RPM acchievements.> What gives? Does anyone with the article understand what he was saying.The> RPMs he listed were 2600, 2900, and 3300. How can he acchieve three> different maximums, unless he changed something and didn't change his> article? All this acchieved with the Tilotson carb which he admitted wastoo> small and a larger one should be used. At 3300 he managed 120 MPH. He must> have had some pitch on that prop., and if he did how could he have gotten> 3300 RPM. It doesn't make any engineering sense to me. Perhaps someone can> enlighten us.>> A.O.G.> Domenic________________________________________________________________________________