Original Posted By: "Greg Cardinal"
Pietenpol-List: Alternative Engines
Pietenpol-List: Alternative Engines
Original Posted By: Ken Beanlands
"Rodger & Betty Childs" Considering the Honda engine, the rated hp is developed at a very highrpm and if it was direct drive would have to be limited to around 3000rpm to keep the blade tips from going supersonic. At 3000 rpm the engine may only be producing 25~30 hp which is is inadequate. So toget the full hp that the engine is capable of producing, you would need aprop reduction unit so the engine could turn 8~9000 rpm and the proponly 2500 rpm. Such a unit would have to be custom made for theengine or in other words, would cost a lot of money.Then there is the subject of harmonics which if not considered and dealtwith could lead to broken crankshafts, soiled pants, cold sweats andvanishing money.But don't let that stop you, that's how we got to the moon and back, andPietenpols were and continue to be an important stop along the way. Also,BMW boxer engines are turning up in a/c more frequently now, albiet, atthe lighter end of the scale.RodgerOne piece wing 95% complete ________________________________________________________________________________Date: Thu, 21 Sep 2000 10:12:45 -0600 (MDT)
"Rodger & Betty Childs" Considering the Honda engine, the rated hp is developed at a very highrpm and if it was direct drive would have to be limited to around 3000rpm to keep the blade tips from going supersonic. At 3000 rpm the engine may only be producing 25~30 hp which is is inadequate. So toget the full hp that the engine is capable of producing, you would need aprop reduction unit so the engine could turn 8~9000 rpm and the proponly 2500 rpm. Such a unit would have to be custom made for theengine or in other words, would cost a lot of money.Then there is the subject of harmonics which if not considered and dealtwith could lead to broken crankshafts, soiled pants, cold sweats andvanishing money.But don't let that stop you, that's how we got to the moon and back, andPietenpols were and continue to be an important stop along the way. Also,BMW boxer engines are turning up in a/c more frequently now, albiet, atthe lighter end of the scale.RodgerOne piece wing 95% complete ________________________________________________________________________________Date: Thu, 21 Sep 2000 10:12:45 -0600 (MDT)
RE: Pietenpol-List: Alternative Engines
Original Posted By: owner-pietenpol-list-server(at)matronics.com
Mike, One other avenue you might want to explore is the corvair engine.Bernie used them on the piets he built after 1960. Easy conversion andplenty of power.Carlps nice to the wallet also-----Original Message-----
Mike, One other avenue you might want to explore is the corvair engine.Bernie used them on the piets he built after 1960. Easy conversion andplenty of power.Carlps nice to the wallet also-----Original Message-----
Re: Pietenpol-List: Alternative Engines
Original Posted By:
Hi Guys Though I would add some input to the engine discussion. Besides weightyou must consider the power transmission.I don't mean gears although we can get into that. The old slow draggyairframes, like the Pietenpol, benefit from as large a thrust diameter asfeasible. In other words a big relatively coarse propeller turning slowly.The smaller engines in use today make their horsepower at a higher rpm andwith less torque. Smaller props at higher rpm let the engine turn faster tomake more HP but don't necessarily transfer the power to thrust as well. Horsepower is a measurement of the rate of doing work. One Horsepoweris 33,000 ftlbs of work done in one minute.Torque is usually measured infoot pounds. (pounds feet for you engineering types) To get the unit ofhorsepower we need to figure out how far the engine moves its load in onerevolution. Since the unit of torque is foot pounds, the engine moves itsload 6.28 ft per rev. The circumference of a circle with a radius of onefoot. If we divide the standard HP figure of 33,000 by 6.28 and round thingsoff a bit we get a constant of 5252. with this information and a dyno we canmeasure the torque developed multiply it by the rpm divide it by theconstant 5252 and come up with the HP.HP = Torque x RPM / 5252If you remember some algebra (no, you don't get that from swimming with yourgirlfriend in a quarry) you can change things around and find out whattorque you get at a particular rpm.Torque = HP x 5252 / RPM Now an old A engine is 200.5 cu.in. and makes its 40 HP at about 2000RPM. Now 40 x 5252 / 2000= 105 ft lbs. Not much you say, you try to pullthat torque wrench around the circle at 2000 rpm!Now, although I have owned several Honda Goldwing's, I don't remember atwhat rpm the HP rating was taken, but if we assume it is high in the RPMband for a relatively small displacement 1000 or 1200 cc engine approx (74cu in) and we apply the math, I'm sure we will find the torque to be muchless than a slow running engine of the same HP. The point of all this isthat almost any engine can be made to deliver its power, at what ever outputRPM we want, by using reduction gearing. Many aircraft engines use reduction gears, RR Merlins, Allisons, Prattand Whitney, Continentals and Lycoming have all built engines using thisprinciple. The engine is made to run at the RPM that produces the mosttorque with the prop turning at the most efficient RPM to tranfer that powerareodynamically. Most of the small aircraft we play with use direct drive,large bore, high torque, low speed engines to eliminate the need to gear theengine to turn a big prop slowly. Now if you take that motorcycle engine figure out what RPM it needs torun to provide the TORQUE required to swing a big prop and run it in thatgear, perhaps you could remove all the other unnessacary gears and savesome weight. You will still have an engine that runs very fast to providethe power needed to fly. It will work but it means a lot of extracomplexity. If you check out the archives or in the BPA Newsletters you will findreference to A's that easily produce 60 + HP. Not too bad for an airframethat will fly on 33 HP. I have always liked the sound of a slow runningengine swinging a big prop. Wonder what would happen if you worked on a setof light weight headers and cammed an old A to increase the torque and makeit quieter. A stealth Peit?John Mc----- Original Message -----
Hi Guys Though I would add some input to the engine discussion. Besides weightyou must consider the power transmission.I don't mean gears although we can get into that. The old slow draggyairframes, like the Pietenpol, benefit from as large a thrust diameter asfeasible. In other words a big relatively coarse propeller turning slowly.The smaller engines in use today make their horsepower at a higher rpm andwith less torque. Smaller props at higher rpm let the engine turn faster tomake more HP but don't necessarily transfer the power to thrust as well. Horsepower is a measurement of the rate of doing work. One Horsepoweris 33,000 ftlbs of work done in one minute.Torque is usually measured infoot pounds. (pounds feet for you engineering types) To get the unit ofhorsepower we need to figure out how far the engine moves its load in onerevolution. Since the unit of torque is foot pounds, the engine moves itsload 6.28 ft per rev. The circumference of a circle with a radius of onefoot. If we divide the standard HP figure of 33,000 by 6.28 and round thingsoff a bit we get a constant of 5252. with this information and a dyno we canmeasure the torque developed multiply it by the rpm divide it by theconstant 5252 and come up with the HP.HP = Torque x RPM / 5252If you remember some algebra (no, you don't get that from swimming with yourgirlfriend in a quarry) you can change things around and find out whattorque you get at a particular rpm.Torque = HP x 5252 / RPM Now an old A engine is 200.5 cu.in. and makes its 40 HP at about 2000RPM. Now 40 x 5252 / 2000= 105 ft lbs. Not much you say, you try to pullthat torque wrench around the circle at 2000 rpm!Now, although I have owned several Honda Goldwing's, I don't remember atwhat rpm the HP rating was taken, but if we assume it is high in the RPMband for a relatively small displacement 1000 or 1200 cc engine approx (74cu in) and we apply the math, I'm sure we will find the torque to be muchless than a slow running engine of the same HP. The point of all this isthat almost any engine can be made to deliver its power, at what ever outputRPM we want, by using reduction gearing. Many aircraft engines use reduction gears, RR Merlins, Allisons, Prattand Whitney, Continentals and Lycoming have all built engines using thisprinciple. The engine is made to run at the RPM that produces the mosttorque with the prop turning at the most efficient RPM to tranfer that powerareodynamically. Most of the small aircraft we play with use direct drive,large bore, high torque, low speed engines to eliminate the need to gear theengine to turn a big prop slowly. Now if you take that motorcycle engine figure out what RPM it needs torun to provide the TORQUE required to swing a big prop and run it in thatgear, perhaps you could remove all the other unnessacary gears and savesome weight. You will still have an engine that runs very fast to providethe power needed to fly. It will work but it means a lot of extracomplexity. If you check out the archives or in the BPA Newsletters you will findreference to A's that easily produce 60 + HP. Not too bad for an airframethat will fly on 33 HP. I have always liked the sound of a slow runningengine swinging a big prop. Wonder what would happen if you worked on a setof light weight headers and cammed an old A to increase the torque and makeit quieter. A stealth Peit?John Mc----- Original Message -----
Pietenpol-List: Alternative Engines
Original Posted By: "Carl Loar"
Subject: Pietenpol-List: Alternative Engines MIDNIGHTRIDER-@webtv.net.ETAsAhQDKqQSWVeXuAzVvcBU2J4mDcfJ7wIUbGCfZsFiVkugE7P3LIQ+BHgll74Thanks for all the input guys. I plan on building a Piet. Right now I'mgetting all the woodworking tools together. I'm purchasing a bandsaw andtablesaw this weekend. I'm a motorcycle jock and my wife's a licensedpilot. I've got her riding motorcycles now so I guess I'm going to learnto fly airplanes. I flew hanggliders for ten years so I am not new toflying. I'm a motorcycle mechanic so I'm very familiar with mostmotorcycle engines. What I don't know is how much of a load a prop putson a crankshaft and that type of information. If and when my Piet iscompleted my wife and I will flying together most of the time. Our totalcombined weight is around 350lbs. Will the Model A engine fly us both onhot marginal days? Thanks, Mike S.________________________________________________________________________________
Subject: Pietenpol-List: Alternative Engines MIDNIGHTRIDER-@webtv.net.ETAsAhQDKqQSWVeXuAzVvcBU2J4mDcfJ7wIUbGCfZsFiVkugE7P3LIQ+BHgll74Thanks for all the input guys. I plan on building a Piet. Right now I'mgetting all the woodworking tools together. I'm purchasing a bandsaw andtablesaw this weekend. I'm a motorcycle jock and my wife's a licensedpilot. I've got her riding motorcycles now so I guess I'm going to learnto fly airplanes. I flew hanggliders for ten years so I am not new toflying. I'm a motorcycle mechanic so I'm very familiar with mostmotorcycle engines. What I don't know is how much of a load a prop putson a crankshaft and that type of information. If and when my Piet iscompleted my wife and I will flying together most of the time. Our totalcombined weight is around 350lbs. Will the Model A engine fly us both onhot marginal days? Thanks, Mike S.________________________________________________________________________________