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#1
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PSRU design advantages
This is probably going to open old wounds. What I would like is experienced
input on the advantages, for economic, efficiency and longevity etc. of different types of redrives. I am leaning towards a cog-belt reducer in a 6 cylinder, liquid cooled, configuration driving a long drive shaft to the prop. |
#2
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PSRU design advantages
"ADK" wrote in message news:X6TXf.28774$%H.11944@clgrps13... This is probably going to open old wounds. What I would like is experienced input on the advantages, for economic, efficiency and longevity etc. of different types of redrives. I am leaning towards a cog-belt reducer in a 6 cylinder, liquid cooled, configuration driving a long drive shaft to the prop. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Warning,Warning, Danger, Danger, Will Robinson! Yep, that is a really big can of worms. The redrive is not as big a problem as you think. You get into a mess when you start talking about long drive shafts. Torsional resonance has brought many of the great minds of the flying industry to their knees. No joke. I don't have all of the links at hand, but someone here does. Start by googling torsional resonance. Then, be afraid. Be very afraid. I you don't get afraid, keep looking, until you get afraid, because you need to get afraid, or you don't understand the problem. -- Jim in NC |
#3
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PSRU design advantages
Morgans wrote:
"ADK" wrote in message news:X6TXf.28774$%H.11944@clgrps13... This is probably going to open old wounds. What I would like is experienced input on the advantages, for economic, efficiency and longevity etc. of different types of redrives. I am leaning towards a cog-belt reducer in a 6 cylinder, liquid cooled, configuration driving a long drive shaft to the prop. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Warning,Warning, Danger, Danger, Will Robinson! LOL Yep, that is a really big can of worms. The redrive is not as big a problem as you think. You get into a mess when you start talking about long drive shafts. I'd recommend (ADK) research on the BD-5 drivetrain (redrives and long driveshafts). Not unsurmountable, but a certainly a big can of worms as you (Jim) state. Efficiency isn't directly affected. Weight may be affected. Longevity will be either good or very short (vibration), but not in between. |
#4
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PSRU design advantages
("Morgans" wrote)
Torsional resonance has brought many of the great minds of the flying industry to their knees. No joke. I don't have all of the links at hand, but someone here does. Start by googling torsional resonance. Then, be afraid. Be very afraid. I you don't get afraid, keep looking, until you get afraid, because you need to get afraid, or you don't understand the problem. I'm not skeer't AND I don't understand the problem. I thought the (rubber?) (toothed?) (cog?) belt redrives absorb? dampen? out a lot of those problems - even, to some extent, the slightly longer shaft kind of problems. Add a three bladed wooden prop, and you're golden. g No? Next I tackle Mu-1 issues... Montblack "Get out of the house. Now! That [post] came from your basement." Fooled them. We don't have a basement. Ha! "Then get out of your house, an F5 twister is coming down the street! Now be afraid..." |
#5
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PSRU design advantages
"Morgans" wrote in message ... "ADK" wrote in message news:X6TXf.28774$%H.11944@clgrps13... This is probably going to open old wounds. What I would like is experienced input on the advantages, for economic, efficiency and longevity etc. of different types of redrives. I am leaning towards a cog-belt reducer in a 6 cylinder, liquid cooled, configuration driving a long drive shaft to the prop. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Warning,Warning, Danger, Danger, Will Robinson! Yep, that is a really big can of worms. The redrive is not as big a problem as you think. You get into a mess when you start talking about long drive shafts. Torsional resonance has brought many of the great minds of the flying industry to their knees. No joke. I don't have all of the links at hand, but someone here does. Start by googling torsional resonance. Then, be afraid. Be very afraid. I you don't get afraid, keep looking, until you get afraid, because you need to get afraid, or you don't understand the problem. -- Jim in NC Yes, Sir! Lots of old wounds, etc, etc ... Actually, I believe that a driveshaft can be part of the problem, solution, or both--although, in and of itself, I agree that a long driveshaft is far more likely to be a problem than a solution. Also, don't forget that all resonance applied through the engine mount to the airframe will still apply--there is a famous "Contact!" magazine article describing some of both problems during the [attempted] development of the BD-5. The point here is that, although a loss of power is the most obvious And keep in mind that, although the redrive is not a source of torsional resonance, the redrive is not inherently dampening. However, many redrives can be a source of considerable shear and bending loads applied to the crankshaft. I don't know how much is too much in either case. As additional food for thought: I was a long time advocate of automotive conversions, but I am now leaning away from them--as well as from many of the more modern engine packages now available. I believe that they can be just about as reliable in service, and that the probable weight penalty is acceptable--if a slightly heavier airplane does the same job, burns a little more fuel, and has a lower initial cost; it may still be the best value, especially if you enjoy the education that you will achieve through the development work. However, I am now leaning back toward the "traditional" type certified engines because it may be much easier to get approval for IFR operation. For some time to come, at least in the US, TFRs are going to continue as a fact of life; and an IFR flight plan gives that greatest assistance in staying out of difficulty on cross country flights. Just my $.02, and YMMV. Peter |
#6
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PSRU design advantages
How would one of the composite props, such as an IVO or Warp drive fair in
an application such as I have described? Especially using a 3 or 4 blade prop. Also I want to use a segmented drive shaft so that each of two sections are reduced in length over a single long shaft. Would not using a 6 cylinder higher reving engine also be an advantage over a lycoming for torsional vibration or would the concern only change in frequency? "Peter Dohm" wrote in message ... "Morgans" wrote in message ... "ADK" wrote in message news:X6TXf.28774$%H.11944@clgrps13... This is probably going to open old wounds. What I would like is experienced input on the advantages, for economic, efficiency and longevity etc. of different types of redrives. I am leaning towards a cog-belt reducer in a 6 cylinder, liquid cooled, configuration driving a long drive shaft to the prop. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Warning,Warning, Danger, Danger, Will Robinson! Yep, that is a really big can of worms. The redrive is not as big a problem as you think. You get into a mess when you start talking about long drive shafts. Torsional resonance has brought many of the great minds of the flying industry to their knees. No joke. I don't have all of the links at hand, but someone here does. Start by googling torsional resonance. Then, be afraid. Be very afraid. I you don't get afraid, keep looking, until you get afraid, because you need to get afraid, or you don't understand the problem. -- Jim in NC Yes, Sir! Lots of old wounds, etc, etc ... Actually, I believe that a driveshaft can be part of the problem, solution, or both--although, in and of itself, I agree that a long driveshaft is far more likely to be a problem than a solution. Also, don't forget that all resonance applied through the engine mount to the airframe will still apply--there is a famous "Contact!" magazine article describing some of both problems during the [attempted] development of the BD-5. The point here is that, although a loss of power is the most obvious And keep in mind that, although the redrive is not a source of torsional resonance, the redrive is not inherently dampening. However, many redrives can be a source of considerable shear and bending loads applied to the crankshaft. I don't know how much is too much in either case. As additional food for thought: I was a long time advocate of automotive conversions, but I am now leaning away from them--as well as from many of the more modern engine packages now available. I believe that they can be just about as reliable in service, and that the probable weight penalty is acceptable--if a slightly heavier airplane does the same job, burns a little more fuel, and has a lower initial cost; it may still be the best value, especially if you enjoy the education that you will achieve through the development work. However, I am now leaning back toward the "traditional" type certified engines because it may be much easier to get approval for IFR operation. For some time to come, at least in the US, TFRs are going to continue as a fact of life; and an IFR flight plan gives that greatest assistance in staying out of difficulty on cross country flights. Just my $.02, and YMMV. Peter |
#7
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PSRU design advantages
ADK
Look up Molt Taylor and his Aerocar system. He used a pusher arrangement and seemed to have most of the problems solved with long shaft back to prop. His bird may still be flying some place to exhibitions? Am sure someone will jump in here and give data on his bird and how he coupled shaft to engine with a "power glide" clutch or some such. It allowed a small amount of slippage at each power stroke to prevent the pulse being transmitted to drive shaft and prop as I recall. Best of luck with a difficult problem. Big John `````````````````````````````````````````````````` `````````````````` On Sun, 02 Apr 2006 16:39:19 GMT, "ADK" wrote: This is probably going to open old wounds. What I would like is experienced input on the advantages, for economic, efficiency and longevity etc. of different types of redrives. I am leaning towards a cog-belt reducer in a 6 cylinder, liquid cooled, configuration driving a long drive shaft to the prop. |
#8
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PSRU design advantages
ADK wrote:
How would one of the composite props, such as an IVO or Warp drive fair in an application such as I have described? Especially using a 3 or 4 blade prop. My cure the problem. May create it. Also I want to use a segmented drive shaft so that each of two sections are reduced in length over a single long shaft. May solve the problem. May create it. Would not using a 6 cylinder higher reving engine also be an advantage over a lycoming for torsional vibration or would the concern only change in frequency? The concern is about frequency. Not power. Not absorbtion. Not dampening. Not anything except frequency. If the power pulses generated by the engine or turbulence around the propeller (the ONLY excitation sources available in flight), or any of the harmonics of the two matches the natural frequency of the prop/drivetrain combination, you'll have a short useful life for the drivetrain. -- This is by far the hardest lesson about freedom. It goes against instinct, and morality, to just sit back and watch people make mistakes. We want to help them, which means control them and their decisions, but in doing so we actually hurt them (and ourselves)." |
#9
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PSRU design advantages
("Big John" wrote)
Look up Molt Taylor and his Aerocar system. He used a pusher arrangement and seemed to have most of the problems solved with long shaft back to prop. His bird may still be flying some place to exhibitions? http://www.airventuremuseum.org/coll...%20Aerocar.asp EAA site with links at the bottom: *Taylor Aerocar Design and Construction *Taylor Aerocar Manufacturers History *Taylor Aerocar Specifications *Taylor Aerocar Virtual Exhibit http://www.goldenwingsmuseum.com/Aircraft.html Golden Wing's Museum Collection http://www.goldenwingsmuseum.com/Air...ero%20Car.html 1954 Taylor Aero Car/Aerocar. http://www.goldenwingsmuseum.com/Photo's/Aero%20Car-2.jpg Bigger pic Montblack It would fly tomorrow - after some minor touch ups and an annual. Don't know when it's scheduled to go up again. They take the car out and run around the airport from time to time. School kids love the Aero Car during their tours. It last flew maybe 5 years ago. Maybe 6? |
#10
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PSRU design advantages
"Montblack" wrote It would fly tomorrow - after some minor touch ups and an annual. Don't know when it's scheduled to go up again. They take the car out and run around the airport from time to time. School kids love the Aero Car during their tours. It last flew maybe 5 years ago. Maybe 6? I'm almost positive that I have seen it fly at OSH, within the past 3 years. Last year, perhaps? It was in the 1:00 PM showcase. -- Jim in NC |
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