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#31
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On 13 Aug 2004 14:10:13 -0500, Todd Pattist
wrote: It's that and the fact that you can't keep on increasing the prop diameter - you run out of ground clearance, exceed material limits or hit the inefficiencies of supersonic tips. As I mentioned, that's why the prop designer came up with such a strange looking planform. The prop is wide where it's most efficient (aproximately halfway out from the hub where the prop speed is way below sonic speed) and can produce the greatest thrust, then narrows down rapidly from that point from both leading and trailing edges, then the leading and trailing edges get to running roughly parallel before they stop abruptly at the tip which is squared off. As I mentioned, since the tip is moving the fastest, it's smart to present very little for the air to get draggy about at that point. Some props have rather wide tips, which get hugely draggy at high rpms, and also produce a lot of noise. This things is very odd looking but produces good thrust while being quieter than most props. Corky Scott |
#32
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On Thu, 12 Aug 2004 at 11:01:06 in message
, Corky Scott wrote: The designer of the prop I mentioned wrote in the article about the fallacy of single bladed prop. Regardless the dubius advantage of biting into clean air, the problems associated with the unbalanced thrust produced by the single blade spinning around, despite it being counter balanced weightwise, are for all practical purposes insurmountable. This is successfully been done at model scale, where the effective diameter is more important and High Mach numbers are not used. This is especially true of rubber powered models where the high torque needs a large diameter slow turning airscrew. The mass balance is angled backwards so the offset thrust can be, to some extent, be balanced. -- David CL Francis |
#33
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David CL Francis wrote in message ...
On Thu, 12 Aug 2004 at 11:01:06 in message , Corky Scott wrote: The designer of the prop I mentioned wrote in the article about the fallacy of single bladed prop. Regardless the dubius advantage of biting into clean air, the problems associated with the unbalanced thrust produced by the single blade spinning around, despite it being counter balanced weightwise, are for all practical purposes insurmountable. This is successfully been done at model scale, where the effective diameter is more important and High Mach numbers are not used. This is especially true of rubber powered models where the high torque needs a large diameter slow turning airscrew. The mass balance is angled backwards so the offset thrust can be, to some extent, be balanced. I have seen a motorglider at a couple of airshows that has a single- blade counterweighted propeller. In this case the purpose is to make the engine and prop stowable in the gliding mode. The propulsion as- sembly is mounted on a mast above and behind the pilot, and pivots backwards into a well in the fuselage. The drill is to rotate the prop till the blade is pointing straight down, then lower the mast assembly into the well and close the bay doors. It obviously works - I watched the owner take off and fly away. Whether or not it is satisfactory would be for those who fly it to decide. I haven't heard any comments either way David Johnson |
#34
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In my own experience with American Greens, they oppose anything that
THEY don't do, while demanding outrageous privileges from government. Example: $4 million to have a bicycle lane across the Dumbarton Bridge in San Francisco Bay. Maybe three people a week use it. Iowa City spent a hundred thousand dollars (or more) installing "bicycle lifts" on the front of all city buses. These contraptions allow the bus driver to stop, get out, and "easily" load a bicycle onto a rack mounted on the front of the bus. The Greens insisted that this would encourage the use of public transportation (which has been a financial catastrophe here -- we could literally buy each rider a car for less tax money), and rammed the issue through our sheepish city council. As most of us knew all along, they (like the buses) are rarely used -- thankfully. Each time they ARE used, the bus -- which, of course, must stop at curbside, blocking the traffic lane -- sits for up to 5 minutes while the poor driver wrestles the bike onto the rack. I often wonder how much gas those 25 cars idling behind the bus are "saving" thanks to the Greens. But, of course, we're the idiots for letting them control the agenda... -- Jay Honeck Iowa City, IA Pathfinder N56993 www.AlexisParkInn.com "Your Aviation Destination" |
#35
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In my own experience with American Greens, they oppose anything that THEY don't do, while demanding outrageous privileges from government. Example: $4 million to have a bicycle lane across the Dumbarton Bridge in San Francisco Bay. Maybe three people a week use it. Iowa City spent a hundred thousand dollars (or more) installing "bicycle lifts" on the front of all city buses. These contraptions allow the bus driver to stop, get out, and "easily" load a bicycle onto a rack mounted on the front of the bus. The Greens insisted that this would encourage the use of public transportation (which has been a financial catastrophe here -- we could literally buy each rider a car for less tax money), and rammed the issue through our sheepish city council. As most of us knew all along, they (like the buses) are rarely used -- thankfully. Each time they ARE used, the bus -- which, of course, must stop at curbside, blocking the traffic lane -- sits for up to 5 minutes while the poor driver wrestles the bike onto the rack. I often wonder how much gas those 25 cars idling behind the bus are "saving" thanks to the Greens. But, of course, we're the idiots for letting them control the agenda... -- Jay Honeck Iowa City, IA Pathfinder N56993 www.AlexisParkInn.com "Your Aviation Destination" Jay, you'd enjoy the HOV lanes on the Long Island Expressway (LIE), Long Island NY. Tthe LIE, like many other urban roads, is called by locals the world's longest parking lot. Here's the fun thing. It's 4 lanes plus an HOV lane along much of its length. The HOV lane, however, takes two lanes of width, the lane itself, then transition and buffer areas. HOV traffic is MUCH less than 1/5 of the traffic, I'd guess 1/20th is a better guess, but it owns 1/3 of the real estate. It gets even better. The HOV lanes are only enforced during times of high traffic flow! The times when the extra pavement could really be used by the people going and coming from work, it's denied them. Of course, at times when traffic is sparce, anyone may use the HOV lanes. Now don't get me started on those damned walls along radways to control noise! |
#36
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"Jay Honeck" wrote
Iowa City spent a hundred thousand dollars (or more) installing "bicycle lifts" on the front of all city buses. These contraptions allow the bus driver to stop, get out, and "easily" load a bicycle onto a rack mounted on the front of the bus. We have bike racks on all of our buses here in the Tampa Bay Area. I use them frequently, and despite the Mercedes Diesel parked in my carport, I consider my bicycle my main means of transportation within Tarpon Springs and Pinellas County. We also pulled-up the old railroad tracks and paved a bike-jog path for the entire 34 mile length of the county. On my 68th birthday, I biked both directions (68 miles)in 6 hours. Our bus drivers never touch the bikes, one must view a 10-15 minute training video, pay for a photo ID card, and display it to the bus driver each time that the bike rack is used. As most of us knew all along, they (like the buses) are rarely used -- thankfully. Each time they ARE used, the bus -- which, of course, must stop at curbside, blocking the traffic lane -- sits for up to 5 minutes while the poor driver wrestles the bike onto the rack. Our bikes racks are so heavily used that the county is in the process of upgrading the 2-bike racks to 3-bike racks. It takes this old man only about 15 seconds to load and unload my bike from the rack while the other passengers are boarding. What comments do you have about the mandatory wheelchair lifts that we also have on all of our busses? Using them does require driver assistance and probably about 5 minutes per use. I don't think that any one of those wheelchair users ever thought that one day they would be in that position. I think that it is admiralable that the citizens of Pinellas County have chosen to help these citizens remain independant in their transportation needs. But, of course, we're the idiots for letting them control the agenda... And I thank you very much! :-) I have found that as I age, I become much more considerate and understanding of the needs of others. Bob Moore |
#37
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"Bob Moore" wrote in message . 8... I think that it is admiralable that the citizens of Pinellas County have chosen to help these citizens remain independant in their transportation needs. If I needed help to remain independent I wouldn't consider myself independent. |
#38
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"Bob Moore" wrote in message . 8... "Jay Honeck" wrote Iowa City spent a hundred thousand dollars (or more) installing "bicycle lifts" on the front of all city buses. These contraptions allow the bus driver to stop, get out, and "easily" load a bicycle onto a rack mounted on the front of the bus. We have bike racks on all of our buses here in the Tampa Bay Area. I've never seen a hydraulic one however. I've never seen a driver put a bike in one either. If you're the type to be able to ride a bike, you're usually able to lift it up into the rack yourself. |
#39
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"Steven P. McNicoll" wrote in message thlink.net...
"Bob Moore" wrote in message If I needed help to remain independent I wouldn't consider myself independent. Unless you are living hundreds of miles from other people and surviving by using tools that you made with your own bare hands, you are not independent. Everyone depends on other people to one degree or another. At some point in your life, unless you enjoy sudden death, you will be depending on other people more and more as your body and mind decline. Then maybe you will appreciate the point that Bob Moore made. |
#40
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"lowflyer" wrote in message om... Unless you are living hundreds of miles from other people and surviving by using tools that you made with your own bare hands, you are not independent. Everyone depends on other people to one degree or another. At some point in your life, unless you enjoy sudden death, you will be depending on other people more and more as your body and mind decline. Then maybe you will appreciate the point that Bob Moore made. Do you think you'll ever appreciate the point I made? |
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