Original Posted By:> Fisherman Caye
Please forgive me if this is information that you already have, it's thebasic relationship between the throttle and power:When the manufacturers of an engine generate the horsepower curve, that isthe power generated at full throttle. They use a varying load to maintainthe engine at a specific revolutions per minute (rpm). The loads requiredto hold at the range of rpm's are then plotted. Again, this is all for fullthrottle.Granted, all 3.3 liter / 200 ci engines, at full throttle, have thecapability to produce about the same maximum horsepower (let's say about60hp) at the same rpm (let's say about 2300 - PLEASE don't use these numbersfor design, they are just for conversation). It's a function of the volumeof air and fuel that the engine will pump at a given rpm. When I stated"about the same horsepower", several other things come in to play that makesthe engine more efficient at specific rpm's, such as timing and compressionratio, but I'm ignoring these factors here.Now if you throttle this airflow, you completly change your horsepowercurve. Where you could get 60hp, you only get 30hp due to the restrictedairflow into the combustion chambers. All the Model-A drivers will tell youthat there is no way to get 60hp out of their stock engine, it's due to thelimited airflow in the intakes and that cute little carb sitting on theside. To increase horsepower on that thing, you've got to let it breathe;add a bigger carb, straighten the intakes for smooth flow, and put a specialgrind on the cam to add duration. You do the opposite of all this when youput a half closed throttle plate in the way of the flow.What you ultimately want to do is operate at 2300 rpm due to the prop speedlimitations. That's done not by restricting air into the engine, it's doneby installing a prop that requires 60hp to turn it at 2300 rpm. As I saidbefore, an engine at full throttle can only produce a certain horsepower ata specific rpm. That prop becomes the load that keeps the engine fromspinning any faster. This is achieved because as rpm's increase, the powerrequired to spin that prop increases faster than the engines ability togenerate power. For conversation, this hypothetical prop requires 80hp at2600rpm but the engine only produces 75hp at 2600rpm so it becomesimpossible to the engine to get there. When a 70% cruise setting isapplied, the engine and prop find that rpm that generates a ballance betweenpower required and power available, usually a few hundred rpm's less.When you are driving down the road with an engine turning 2300 rpm, thatdoes not mean that it requires 60hp to do that as a horsepower curve shows.The published horsepower curve is only for full throttle. To push a car orvan down the road really only takes about 20-30 hp.Robert HainesDu Quoin, Illinois / Murphysboro, Illinois
Pietenpol-List: Throttle and power
RE: Pietenpol-List: Throttle and power
Original Posted By: owner-pietenpol-list-server(at)matronics.com
Well put, Robert.One fact that always seems to surprise people is that an engine is mostefficeint at full throttle, even though it is consuming fuel at its maximumrate. At partial throttle, the engine is forced to "pump" the mixture intothe cylinders, drawing against the vacuum in the intake manifold. At fullthrottle the intake manifold is at or very near atmospheric pressure,requiring minimal work to suck the mixture past the intake valves. With asupercharger, manifold pressure is greater than atmospheric and the mixtureis actually pushed into the cylinder past the open intake valves (Oh God,please don't let anyone even think of supercharging a model A), allowingmore power.Jack -----Original Message-----
Well put, Robert.One fact that always seems to surprise people is that an engine is mostefficeint at full throttle, even though it is consuming fuel at its maximumrate. At partial throttle, the engine is forced to "pump" the mixture intothe cylinders, drawing against the vacuum in the intake manifold. At fullthrottle the intake manifold is at or very near atmospheric pressure,requiring minimal work to suck the mixture past the intake valves. With asupercharger, manifold pressure is greater than atmospheric and the mixtureis actually pushed into the cylinder past the open intake valves (Oh God,please don't let anyone even think of supercharging a model A), allowingmore power.Jack -----Original Message-----
Re: Pietenpol-List: Throttle and power
Original Posted By: "Robert Haines"
----- Original Message -----
----- Original Message -----
> Pietenpol-List: Throttle and power
Original Posted By: Fisherman Caye
one Horsepower is 550 ft pounds of work per second. It is a ratio between torque and RPMs . You can have a high RPM low torque engine which puts out X amount of horsepower or you can have low RPM high torque engine ( Model A ) which puts out the same amount of horse power. 65 horsepower from a 1.3 liter suzuki is the same as 65 HP from a Continental BUT you would have to run a major reduction drive on the Suzuki to trade RPMs for torque sufficiently to turn a 6 foot prop and run it at punishingly high piston speeds to maintain that torque. Like the old hotrodders used to say "there's no substitute for cubic inches"Only problem is big cube engines are heavy. Amazingly the "A" is relatively light for 200 cubic inches. Maybe ya'll have already said this in a different way....Just my subect so had to add my two cents. Ed G.>From: "John Dilatush" >Reply-To: pietenpol-list(at)matronics.com>To: >Subject: Re: Pietenpol-List: Throttle and power>Date: Fri, 1 Feb 2002 09:47:04 -0700>>>----- Original Message ----->From: "Robert Haines" >To: >Subject: Pietenpol-List: Throttle and power>>Robert,>>Your explanation for the relationship between throttle opening and the>horsepower curve is excellent! Pardon me if I might add one other thing.>>There seems to be a popular misconception that only torque is important, >not>horsepower. The fact is that ONLY horsepower is the factor that makes an>airplane take off and climb as evidenced by the formula for rate of climb:>>Thrust hp available x 33,000 / Weight of aircraft, = rate of climb>>Thrust hp available (excess hp x prop efficiency)>Weight of aircraft is in pounds>Rate of climb is in ft per min.>Excess horsepower is the hp that is available over and above that required>for level flight.>>Notice that torque is not mentioned. Torque along with rpm, at wide open>throttle as you have pointed out is only one of the factors that go into>horsepower. With a high reving engine you also need to have a prop>reduction unit so as to achieve the required horsepower with a reasonable>prop speed.>>Cheers,>>John Dilatush NX114D, still working on the duplicator to make the prop.>>>> >> > Please forgive me if this is information that you already have, it's the> > basic relationship between the throttle and power:> >> > When the manufacturers of an engine generate the horsepower curve, that >is> > the power generated at full throttle. They use a varying load to >maintain> > the engine at a specific revolutions per minute (rpm). The loads >required> > to hold at the range of rpm's are then plotted. Again, this is all for>full> > throttle.> >> > Granted, all 3.3 liter / 200 ci engines, at full throttle, have the> > capability to produce about the same maximum horsepower (let's say about> > 60hp) at the same rpm (let's say about 2300 - PLEASE don't use these>numbers> > for design, they are just for conversation). It's a function of the>volume> > of air and fuel that the engine will pump at a given rpm. When I stated> > "about the same horsepower", several other things come in to play that>makes> > the engine more efficient at specific rpm's, such as timing and>compression> > ratio, but I'm ignoring these factors here.> >> > Now if you throttle this airflow, you completly change your horsepower> > curve. Where you could get 60hp, you only get 30hp due to the >restricted> > airflow into the combustion chambers. All the Model-A drivers will tell>you> > that there is no way to get 60hp out of their stock engine, it's due to>the> > limited airflow in the intakes and that cute little carb sitting on the> > side. To increase horsepower on that thing, you've got to let it >breathe;> > add a bigger carb, straighten the intakes for smooth flow, and put a>special> > grind on the cam to add duration. You do the opposite of all this when>you> > put a half closed throttle plate in the way of the flow.> >> > What you ultimately want to do is operate at 2300 rpm due to the prop>speed> > limitations. That's done not by restricting air into the engine, it's>done> > by installing a prop that requires 60hp to turn it at 2300 rpm. As I >said> > before, an engine at full throttle can only produce a certain horsepower>at> > a specific rpm. That prop becomes the load that keeps the engine from> > spinning any faster. This is achieved because as rpm's increase, the>power> > required to spin that prop increases faster than the engines ability to> > generate power. For conversation, this hypothetical prop requires 80hp >at> > 2600rpm but the engine only produces 75hp at 2600rpm so it becomes> > impossible to the engine to get there. When a 70% cruise setting is> > applied, the engine and prop find that rpm that generates a ballance>between> > power required and power available, usually a few hundred rpm's less.> >> > When you are driving down the road with an engine turning 2300 rpm, that> > does not mean that it requires 60hp to do that as a horsepower curve>shows.> > The published horsepower curve is only for full throttle. To push a car>or> > van down the road really only takes about 20-30 hp.> >> > Robert Haines> > Du Quoin, Illinois / Murphysboro, Illinois> >> >> > >>> >> >>>________________________________________________________________________________Date: 1 Feb 2002 10:13:43 -0800
one Horsepower is 550 ft pounds of work per second. It is a ratio between torque and RPMs . You can have a high RPM low torque engine which puts out X amount of horsepower or you can have low RPM high torque engine ( Model A ) which puts out the same amount of horse power. 65 horsepower from a 1.3 liter suzuki is the same as 65 HP from a Continental BUT you would have to run a major reduction drive on the Suzuki to trade RPMs for torque sufficiently to turn a 6 foot prop and run it at punishingly high piston speeds to maintain that torque. Like the old hotrodders used to say "there's no substitute for cubic inches"Only problem is big cube engines are heavy. Amazingly the "A" is relatively light for 200 cubic inches. Maybe ya'll have already said this in a different way....Just my subect so had to add my two cents. Ed G.>From: "John Dilatush" >Reply-To: pietenpol-list(at)matronics.com>To: >Subject: Re: Pietenpol-List: Throttle and power>Date: Fri, 1 Feb 2002 09:47:04 -0700>>>----- Original Message ----->From: "Robert Haines" >To: >Subject: Pietenpol-List: Throttle and power>>Robert,>>Your explanation for the relationship between throttle opening and the>horsepower curve is excellent! Pardon me if I might add one other thing.>>There seems to be a popular misconception that only torque is important, >not>horsepower. The fact is that ONLY horsepower is the factor that makes an>airplane take off and climb as evidenced by the formula for rate of climb:>>Thrust hp available x 33,000 / Weight of aircraft, = rate of climb>>Thrust hp available (excess hp x prop efficiency)>Weight of aircraft is in pounds>Rate of climb is in ft per min.>Excess horsepower is the hp that is available over and above that required>for level flight.>>Notice that torque is not mentioned. Torque along with rpm, at wide open>throttle as you have pointed out is only one of the factors that go into>horsepower. With a high reving engine you also need to have a prop>reduction unit so as to achieve the required horsepower with a reasonable>prop speed.>>Cheers,>>John Dilatush NX114D, still working on the duplicator to make the prop.>>>> >> > Please forgive me if this is information that you already have, it's the> > basic relationship between the throttle and power:> >> > When the manufacturers of an engine generate the horsepower curve, that >is> > the power generated at full throttle. They use a varying load to >maintain> > the engine at a specific revolutions per minute (rpm). The loads >required> > to hold at the range of rpm's are then plotted. Again, this is all for>full> > throttle.> >> > Granted, all 3.3 liter / 200 ci engines, at full throttle, have the> > capability to produce about the same maximum horsepower (let's say about> > 60hp) at the same rpm (let's say about 2300 - PLEASE don't use these>numbers> > for design, they are just for conversation). It's a function of the>volume> > of air and fuel that the engine will pump at a given rpm. When I stated> > "about the same horsepower", several other things come in to play that>makes> > the engine more efficient at specific rpm's, such as timing and>compression> > ratio, but I'm ignoring these factors here.> >> > Now if you throttle this airflow, you completly change your horsepower> > curve. Where you could get 60hp, you only get 30hp due to the >restricted> > airflow into the combustion chambers. All the Model-A drivers will tell>you> > that there is no way to get 60hp out of their stock engine, it's due to>the> > limited airflow in the intakes and that cute little carb sitting on the> > side. To increase horsepower on that thing, you've got to let it >breathe;> > add a bigger carb, straighten the intakes for smooth flow, and put a>special> > grind on the cam to add duration. You do the opposite of all this when>you> > put a half closed throttle plate in the way of the flow.> >> > What you ultimately want to do is operate at 2300 rpm due to the prop>speed> > limitations. That's done not by restricting air into the engine, it's>done> > by installing a prop that requires 60hp to turn it at 2300 rpm. As I >said> > before, an engine at full throttle can only produce a certain horsepower>at> > a specific rpm. That prop becomes the load that keeps the engine from> > spinning any faster. This is achieved because as rpm's increase, the>power> > required to spin that prop increases faster than the engines ability to> > generate power. For conversation, this hypothetical prop requires 80hp >at> > 2600rpm but the engine only produces 75hp at 2600rpm so it becomes> > impossible to the engine to get there. When a 70% cruise setting is> > applied, the engine and prop find that rpm that generates a ballance>between> > power required and power available, usually a few hundred rpm's less.> >> > When you are driving down the road with an engine turning 2300 rpm, that> > does not mean that it requires 60hp to do that as a horsepower curve>shows.> > The published horsepower curve is only for full throttle. To push a car>or> > van down the road really only takes about 20-30 hp.> >> > Robert Haines> > Du Quoin, Illinois / Murphysboro, Illinois> >> >> > >>> >> >>>________________________________________________________________________________Date: 1 Feb 2002 10:13:43 -0800
Pietenpol-List: Throttle and power
Original Posted By: "John Dilatush"
Ed,I guess we are saying esentially the same thing in a different way, butthe old saying of " you can't beat cubic inches" is really not valid. Itoo, when building hot rods and racing used to believe this as thegospel, but came to understand it only to be valid in a limited sense.Think of it this way: an engine is nothing more than a sophisicated airpump. The more air/fuel mixture you can pump through it in a giventime, the more horsepower is developed. Remember that horsepower is afunction of time and work. So if you have a large displacement engineturning at a slower rpm, the amount of air/fuel mixture can be equaledby a small displacement engine running at a higher rpm, because thetotal amount of air/fuel going through the engine is the same. Therefore asuming equal combustion efficiency, both can produce the samehorsepower. A good example are the formula one cars that have smalldisplacement engines turning perhaps 10,000 rpm and producing 6 or 7hundred hp.In aircraft the limiting factor is the tip speed of the propeller. Therefore a limited displacement engine which needs a high rpm toproduce the horsepower has to have the rpm reduced to a figure thatallows the prop to turn at an efficient rpm.One reference, (Eric Clutton) uses the formula "that the propeller tipspeed should be aprox four times the speed of the aircraft for maxefficiency. (actually 3.93). This applies to all speeds andconfigurations". When I worked it out for my Pietenpol, using a 76"prop, the rpm should only be 1304 rpm!I apologize for being so wordy about the subject, but hope that thismight be helpful for the members on the list now building Piets, andconsidering using auto conversions.Cheers,John Dilatush, NX114D, now working on a propeller duplicator.Salida, Colorado________________________________________________________________________________
Ed,I guess we are saying esentially the same thing in a different way, butthe old saying of " you can't beat cubic inches" is really not valid. Itoo, when building hot rods and racing used to believe this as thegospel, but came to understand it only to be valid in a limited sense.Think of it this way: an engine is nothing more than a sophisicated airpump. The more air/fuel mixture you can pump through it in a giventime, the more horsepower is developed. Remember that horsepower is afunction of time and work. So if you have a large displacement engineturning at a slower rpm, the amount of air/fuel mixture can be equaledby a small displacement engine running at a higher rpm, because thetotal amount of air/fuel going through the engine is the same. Therefore asuming equal combustion efficiency, both can produce the samehorsepower. A good example are the formula one cars that have smalldisplacement engines turning perhaps 10,000 rpm and producing 6 or 7hundred hp.In aircraft the limiting factor is the tip speed of the propeller. Therefore a limited displacement engine which needs a high rpm toproduce the horsepower has to have the rpm reduced to a figure thatallows the prop to turn at an efficient rpm.One reference, (Eric Clutton) uses the formula "that the propeller tipspeed should be aprox four times the speed of the aircraft for maxefficiency. (actually 3.93). This applies to all speeds andconfigurations". When I worked it out for my Pietenpol, using a 76"prop, the rpm should only be 1304 rpm!I apologize for being so wordy about the subject, but hope that thismight be helpful for the members on the list now building Piets, andconsidering using auto conversions.Cheers,John Dilatush, NX114D, now working on a propeller duplicator.Salida, Colorado________________________________________________________________________________
> Pietenpol-List: Throttle and power
Original Posted By: "Skip Gadd"
Yes Ray -- and two strokes "bang" twice as much per RPM number than 4 strokes.And never forget the HP per pound weight importance! Big Cubes means heavy!!Then there is max power ratings. People "think" because an engine is ratedfor "automotive" purposes at a number -- say 100 HP -- that is the same forin an airplane. It is not -- maybe -- if your lucky -- half of that.But the outboards are rated at true max power -- just like a "real"airplane engine is.Your never going to beat that Yam outboard engine -- no matter how youtwist and turn -- but I enjoy watching your self bashing over this issue.Anything but do what I suggested -- love it!!Trying to save that buck -- eh?? How about wasting it all on what willnever work??My advice -- mortgage the house and by a real -- designed for -- airplaneengine!Peter>------- Start of forwarded message -------> >Subject: Pietenpol-List: Throttle and power>To: "ED GRENTZER" >From: "John Dilatush" >Date: Fri, 1 Feb 2002 19:57:24 -0700>>>Ed,>>I guess we are saying esentially the same thing in a different way, but>the old saying of " you can't beat cubic inches" is really not valid. I>too, when building hot rods and racing used to believe this as the>gospel, but came to understand it only to be valid in a limited sense.>>Think of it this way: an engine is nothing more than a sophisicated air>pump. The more air/fuel mixture you can pump through it in a given>time, the more horsepower is developed. Remember that horsepower is a>function of time and work. So if you have a large displacement engine>turning at a slower rpm, the amount of air/fuel mixture can be equaled>by a small displacement engine running at a higher rpm, because the>total amount of air/fuel going through the engine is the same. >Therefore asuming equal combustion efficiency, both can produce the same>horsepower. A good example are the formula one cars that have small>displacement engines turning perhaps 10,000 rpm and producing 6 or 7>hundred hp.>>In aircraft the limiting factor is the tip speed of the propeller. >Therefore a limited displacement engine which needs a high rpm to>produce the horsepower has to have the rpm reduced to a figure that>allows the prop to turn at an efficient rpm.>>One reference, (Eric Clutton) uses the formula "that the propeller tip>speed should be aprox four times the speed of the aircraft for max>efficiency. (actually 3.93). This applies to all speeds and>configurations". When I worked it out for my Pietenpol, using a 76">prop, the rpm should only be 1304 rpm!>>I apologize for being so wordy about the subject, but hope that this>might be helpful for the members on the list now building Piets, and>considering using auto conversions.>>Cheers,>>John Dilatush, NX114D, now working on a propeller duplicator.>Salida, Colorado>>> >------- End of forwarded message ------->>>_________________________________________________>FindLaw - Free Case Law, Jobs, Library, Community>http://www.FindLaw.com>Get your FREE @JUSTICE.COM email!>http://mail.Justice.com> ------- End of forwarded message -------FindLaw - Free Case Law, Jobs, Library, Communityhttp://www.FindLaw.comGet your FREE @JUSTICE.COM email!http://mail.Justice.com________________________________________________________________________________
Yes Ray -- and two strokes "bang" twice as much per RPM number than 4 strokes.And never forget the HP per pound weight importance! Big Cubes means heavy!!Then there is max power ratings. People "think" because an engine is ratedfor "automotive" purposes at a number -- say 100 HP -- that is the same forin an airplane. It is not -- maybe -- if your lucky -- half of that.But the outboards are rated at true max power -- just like a "real"airplane engine is.Your never going to beat that Yam outboard engine -- no matter how youtwist and turn -- but I enjoy watching your self bashing over this issue.Anything but do what I suggested -- love it!!Trying to save that buck -- eh?? How about wasting it all on what willnever work??My advice -- mortgage the house and by a real -- designed for -- airplaneengine!Peter>------- Start of forwarded message -------> >Subject: Pietenpol-List: Throttle and power>To: "ED GRENTZER" >From: "John Dilatush" >Date: Fri, 1 Feb 2002 19:57:24 -0700>>>Ed,>>I guess we are saying esentially the same thing in a different way, but>the old saying of " you can't beat cubic inches" is really not valid. I>too, when building hot rods and racing used to believe this as the>gospel, but came to understand it only to be valid in a limited sense.>>Think of it this way: an engine is nothing more than a sophisicated air>pump. The more air/fuel mixture you can pump through it in a given>time, the more horsepower is developed. Remember that horsepower is a>function of time and work. So if you have a large displacement engine>turning at a slower rpm, the amount of air/fuel mixture can be equaled>by a small displacement engine running at a higher rpm, because the>total amount of air/fuel going through the engine is the same. >Therefore asuming equal combustion efficiency, both can produce the same>horsepower. A good example are the formula one cars that have small>displacement engines turning perhaps 10,000 rpm and producing 6 or 7>hundred hp.>>In aircraft the limiting factor is the tip speed of the propeller. >Therefore a limited displacement engine which needs a high rpm to>produce the horsepower has to have the rpm reduced to a figure that>allows the prop to turn at an efficient rpm.>>One reference, (Eric Clutton) uses the formula "that the propeller tip>speed should be aprox four times the speed of the aircraft for max>efficiency. (actually 3.93). This applies to all speeds and>configurations". When I worked it out for my Pietenpol, using a 76">prop, the rpm should only be 1304 rpm!>>I apologize for being so wordy about the subject, but hope that this>might be helpful for the members on the list now building Piets, and>considering using auto conversions.>>Cheers,>>John Dilatush, NX114D, now working on a propeller duplicator.>Salida, Colorado>>> >------- End of forwarded message ------->>>_________________________________________________>FindLaw - Free Case Law, Jobs, Library, Community>http://www.FindLaw.com>Get your FREE @JUSTICE.COM email!>http://mail.Justice.com> ------- End of forwarded message -------FindLaw - Free Case Law, Jobs, Library, Communityhttp://www.FindLaw.comGet your FREE @JUSTICE.COM email!http://mail.Justice.com________________________________________________________________________________
RE: Pietenpol-List: Throttle and power
Original Posted By: owner-pietenpol-list-server(at)matronics.com
I've been lurking here for a while. I have been building a Piet/GN-1 forquite a while now. Or perhaps I should say that I need to get back tobuilding it!The engine game is one of my passions. I instruct apprentices on themaintenance of large diesel engines. Ed is quite right about 550 ft lbs persecond to be used as the accepted standard for HP.In our aircraft we need to consider that the airframe is not going to flyconsiderably faster with more hp. Its draggy nature is part of its charmthat attracted us all in the first place.HP is the rate of doing work. Torque does the work. The time factor ismeasured in revolutions per minute. If we multiply 550 by 60 seconds we get33000 ft lbs of work done in one minute. So,?, how far does your engine moveits load in one revolution of the crank? Torque for us is measured inPounds Feet or foot pounds, sounds better. 1 foot radius, 2 foot diameter, XPi, 3.14159, gives us a distance of 6.28 feet per rev.33000/6.28318=5252 Now we can use some formulas.Hp= torque X rpm/5252 , Handy, but with out a dyno how can you know thetorque? Changing the formula around we can get the torque formula T = hp x5252/ rpm Now it is well known that a 40 hp Ford A is capable of getting two of us ina Piet off of the ground. Does it ever sound, smell and feel neat! So if itis turning at 2200 and the HP is assumed to be 40 then the torque would be95ftlbs.For comparison a VW making 40hp @ 3600rpm is by the formulas only making58.3 ftlbsTo turn fast enough to make 40hp the VW has to have a shorter lever/prop.The thrust disk now is too small for the draggy airframe. Kinda like thewrong gear ratio. It is erelavent to the crankshaft how long the lever is.It puts out torque in foot pounds. The A works well in a Piet because it candeliver adequate torque for the prop disk needs. The Corvair in a piet workstoo but not at its full potential. It isn't nessecary to run them as fast asthey could go. The larger prop limiting the engine to a lower rpm providessufficent thrust to fly.The point of all this?It doesn't matter to the engine if it is a Model A a boat or a Piet, or a RRMerlin or a Highway tractor. The engine only provides the torque at rpm. Ifthe load can be moved at a higher speed the engine can develope more poweruntil its power output capability balances with the load. (Displacement,breathing, mixture, timing and prop pitch and dia. all affect this.) Groundvehicles use transmissions to allow this to happen. If the engine can dothe required work with direct drive it is a simpler solution. For usexperimental types if we can swing the same size prop as an A 65 at the samerpm then we must be making the same hp. The Fords are available and Fun.Continentals etc are made for this. (I haven't flown either enough to judgehow wing position and fuselage moment affect the flight, comments?) Thereare a lot of engines out that with work and re-drives could be made to work.I went to the old BPA website looking for the A dyno test specs but the werenot available anymore. If I remember rightly the biggest gain in power onthe Fords was in the breathing.John, up in Cold Canada, almost ready to shelve the Cirrus and go back to myModel B-----Original Message-----
I've been lurking here for a while. I have been building a Piet/GN-1 forquite a while now. Or perhaps I should say that I need to get back tobuilding it!The engine game is one of my passions. I instruct apprentices on themaintenance of large diesel engines. Ed is quite right about 550 ft lbs persecond to be used as the accepted standard for HP.In our aircraft we need to consider that the airframe is not going to flyconsiderably faster with more hp. Its draggy nature is part of its charmthat attracted us all in the first place.HP is the rate of doing work. Torque does the work. The time factor ismeasured in revolutions per minute. If we multiply 550 by 60 seconds we get33000 ft lbs of work done in one minute. So,?, how far does your engine moveits load in one revolution of the crank? Torque for us is measured inPounds Feet or foot pounds, sounds better. 1 foot radius, 2 foot diameter, XPi, 3.14159, gives us a distance of 6.28 feet per rev.33000/6.28318=5252 Now we can use some formulas.Hp= torque X rpm/5252 , Handy, but with out a dyno how can you know thetorque? Changing the formula around we can get the torque formula T = hp x5252/ rpm Now it is well known that a 40 hp Ford A is capable of getting two of us ina Piet off of the ground. Does it ever sound, smell and feel neat! So if itis turning at 2200 and the HP is assumed to be 40 then the torque would be95ftlbs.For comparison a VW making 40hp @ 3600rpm is by the formulas only making58.3 ftlbsTo turn fast enough to make 40hp the VW has to have a shorter lever/prop.The thrust disk now is too small for the draggy airframe. Kinda like thewrong gear ratio. It is erelavent to the crankshaft how long the lever is.It puts out torque in foot pounds. The A works well in a Piet because it candeliver adequate torque for the prop disk needs. The Corvair in a piet workstoo but not at its full potential. It isn't nessecary to run them as fast asthey could go. The larger prop limiting the engine to a lower rpm providessufficent thrust to fly.The point of all this?It doesn't matter to the engine if it is a Model A a boat or a Piet, or a RRMerlin or a Highway tractor. The engine only provides the torque at rpm. Ifthe load can be moved at a higher speed the engine can develope more poweruntil its power output capability balances with the load. (Displacement,breathing, mixture, timing and prop pitch and dia. all affect this.) Groundvehicles use transmissions to allow this to happen. If the engine can dothe required work with direct drive it is a simpler solution. For usexperimental types if we can swing the same size prop as an A 65 at the samerpm then we must be making the same hp. The Fords are available and Fun.Continentals etc are made for this. (I haven't flown either enough to judgehow wing position and fuselage moment affect the flight, comments?) Thereare a lot of engines out that with work and re-drives could be made to work.I went to the old BPA website looking for the A dyno test specs but the werenot available anymore. If I remember rightly the biggest gain in power onthe Fords was in the breathing.John, up in Cold Canada, almost ready to shelve the Cirrus and go back to myModel B-----Original Message-----
Re: Pietenpol-List: Throttle and power
Original Posted By: clif