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#101
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Actually, I read somewhere that the US Navy is converting its steam
catapults to linear electric motors to get finer control over the launch. I also suspect that it reduces the manpower required to operate the "cat". Bill Daniels "Bob Johnson" wrote in message ... Hi Bruce -- That's a very welcome correction to my hazily-remembered version of a second-hand report of what the 454 c.i. engine torque/hp/rpm chart looks like. This is the kind of info I was looking for and thanks for providing it! In all our past kicking around of the ideal winch prime mover, here's one that sounds silly but might rate at least an engineering investigation -- a recip steam engine! If I recall correctly, the steam engine develops max torque at stall. What got me thinking about that was the fact that the Navy gets 66,000 lb Super Hornets flying in about the same three seconds that it takes us to get airborne. And they do it with steam, not because it's handy, but that's probably the only practical way to get it done. BJ Bruce Hoult wrote: In article , Bob Johnson wrote: Our engine is petrol fueled. Despite Google's best efforts, I have not yet located a Torque/HP/RPM curve for our very common 7.4 L engine, but have heard that it develops max torque and HP at about 3000 RPM and further that the curves are fairly flat at this point. You are making some totally contradictory and inconsistent claims there. If max torque and max HP occur close together then they must both drop off precipitously after that. If the torque curve is flat then HP will be increasing linearly with RPM, max torque and max HP will be very far apart. It is quite likely that you do have maximum torque at around 3000 RPM, but if for example the torque curve is flat enough that the torque at the 5000 RPM redline is still 60% or more of that at 3000 RPM then that (redline) is exactly where maximum power will be. -- Bruce |
#103
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I love it! The boiler could provide the permanent thermal off the top of the
launch too! Ian "Bob Johnson" wrote in message ... Hi Bruce -- That's a very welcome correction to my hazily-remembered version of a second-hand report of what the 454 c.i. engine torque/hp/rpm chart looks like. This is the kind of info I was looking for and thanks for providing it! In all our past kicking around of the ideal winch prime mover, here's one that sounds silly but might rate at least an engineering investigation -- a recip steam engine! If I recall correctly, the steam engine develops max torque at stall. What got me thinking about that was the fact that the Navy gets 66,000 lb Super Hornets flying in about the same three seconds that it takes us to get airborne. And they do it with steam, not because it's handy, but that's probably the only practical way to get it done. BJ Bruce Hoult wrote: In article , Bob Johnson wrote: Our engine is petrol fueled. Despite Google's best efforts, I have not yet located a Torque/HP/RPM curve for our very common 7.4 L engine, but have heard that it develops max torque and HP at about 3000 RPM and further that the curves are fairly flat at this point. You are making some totally contradictory and inconsistent claims there. If max torque and max HP occur close together then they must both drop off precipitously after that. If the torque curve is flat then HP will be increasing linearly with RPM, max torque and max HP will be very far apart. It is quite likely that you do have maximum torque at around 3000 RPM, but if for example the torque curve is flat enough that the torque at the 5000 RPM redline is still 60% or more of that at 3000 RPM then that (redline) is exactly where maximum power will be. -- Bruce |
#104
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OK, the threads on this topic are branching out pretty good, so again I feel the
need to post that most if not all of the collected wisdom in the world concerning ground launch in all of its phases is already available in one place. This place is between the covers of one slim volume by the same name and was authored by the great Derek Piggott. I just Googled "ground launch piggott" and up popped maybe a half dozen people who wanted to sell me one. The first was NSM, our National Soaring Museum: http://www.soaringmuseum.org/estore/...353463656.html Get one today! (Book, that is) And after you read it, don't go out and "do this at home" as they say. Get somebody that knows how to show you the ropes (har, har) and then the book will make much more sense. Disclaimer--- I own stock in both Piggott Enterprises and NSM. Just kidding BJ Brian Case wrote: If someone wanted to do the world of ground launch a great favor, they would start a web site where the collective wisdom of the world could be displayed so that anyone wishing to undertake winch launch could go there and get an education. Ok it may not be the collective wisdom of the world. But there is quite a bit of information on winch launching at: http://www.northwestsoaring.com/sitemap.shtml Let me know if I am missing anything really important about Winch Launching here. Brian Case CFIIG/ASEL |
#105
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Gonna take a California Governor-sized battery and alternator combo down there
in the nuclear engine room! Using my handy-dandy winch horsepower spreadsheet, solving for required launching force is an incredible 218,000 pounds and over 50,000 horsepower! Of course the engines are in full AB, but still --- Other numbers are a "ground run" of 306 ft and a peak acceleration of 3.3G in 2.4 sec. I can see that they have already provided the Super Hornet with a pretty stout nosegear. That's where their "cg hook" is, I believe. BJ Bill Daniels wrote: Actually, I read somewhere that the US Navy is converting its steam catapults to linear electric motors to get finer control over the launch. I also suspect that it reduces the manpower required to operate the "cat". Bill Daniels "Bob Johnson" wrote in message ... Hi Bruce -- That's a very welcome correction to my hazily-remembered version of a second-hand report of what the 454 c.i. engine torque/hp/rpm chart looks like. This is the kind of info I was looking for and thanks for providing it! In all our past kicking around of the ideal winch prime mover, here's one that sounds silly but might rate at least an engineering investigation -- a recip steam engine! If I recall correctly, the steam engine develops max torque at stall. What got me thinking about that was the fact that the Navy gets 66,000 lb Super Hornets flying in about the same three seconds that it takes us to get airborne. And they do it with steam, not because it's handy, but that's probably the only practical way to get it done. BJ Bruce Hoult wrote: In article , Bob Johnson wrote: Our engine is petrol fueled. Despite Google's best efforts, I have not yet located a Torque/HP/RPM curve for our very common 7.4 L engine, but have heard that it develops max torque and HP at about 3000 RPM and further that the curves are fairly flat at this point. You are making some totally contradictory and inconsistent claims there. If max torque and max HP occur close together then they must both drop off precipitously after that. If the torque curve is flat then HP will be increasing linearly with RPM, max torque and max HP will be very far apart. It is quite likely that you do have maximum torque at around 3000 RPM, but if for example the torque curve is flat enough that the torque at the 5000 RPM redline is still 60% or more of that at 3000 RPM then that (redline) is exactly where maximum power will be. -- Bruce |
#106
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In article ,
Bob Johnson wrote: In all our past kicking around of the ideal winch prime mover, here's one that sounds silly but might rate at least an engineering investigation -- a recip steam engine! If I recall correctly, the steam engine develops max torque at stall. That is true, and it is also true of many electric motors. Unfortunately, I suspect that if they are strong enough with the glider flying at 60 knots then they will be far *too* strong at the start! -- Bruce |
#107
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I believe a German club has recently built themselves a DC winch using
dozens of automotive type batteries. Haven't heard how they have done with it, though. BJ Bruce Hoult wrote: In article , Bob Johnson wrote: In all our past kicking around of the ideal winch prime mover, here's one that sounds silly but might rate at least an engineering investigation -- a recip steam engine! If I recall correctly, the steam engine develops max torque at stall. That is true, and it is also true of many electric motors. Unfortunately, I suspect that if they are strong enough with the glider flying at 60 knots then they will be far *too* strong at the start! -- Bruce |
#108
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Yes, but would you get up at 3am to stoke it
At 20:24 30 October 2003, Tango4 wrote: I love it! The boiler could provide the permanent thermal off the top of the launch too! Ian 'Bob Johnson' wrote in message ... Hi Bruce -- That's a very welcome correction to my hazily-remembered version of a second-hand report of what the 454 c.i. engine torque/hp/rpm chart looks like. This is the kind of info I was looking for and thanks for providing it! In all our past kicking around of the ideal winch prime mover, here's one that sounds silly but might rate at least an engineering investigation -- a recip steam engine! If I recall correctly, the steam engine develops max torque at stall. What got me thinking about that was the fact that the Navy gets 66,000 lb Super Hornets flying in about the same three seconds that it takes us to get airborne. And they do it with steam, not because it's handy, but that's probably the only practical way to get it done. BJ Bruce Hoult wrote: In article , Bob Johnson wrote: Our engine is petrol fueled. Despite Google's best efforts, I have not yet located a Torque/HP/RPM curve for our very common 7.4 L engine, but have heard that it develops max torque and HP at about 3000 RPM and further that the curves are fairly flat at this point. You are making some totally contradictory and inconsistent claims there. If max torque and max HP occur close together then they must both drop off precipitously after that. If the torque curve is flat then HP will be increasing linearly with RPM, max torque and max HP will be very far apart. It is quite likely that you do have maximum torque at around 3000 RPM, but if for example the torque curve is flat enough that the torque at the 5000 RPM redline is still 60% or more of that at 3000 RPM then that (redline) is exactly where maximum power will be. -- Bruce |
#109
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Yes, but would you get up at 3am to stoke it Who would't want to stroke the wench at 3am? |
#110
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There once was a non-BGA soaring site/club in East Anglia in the UK. The
operator was named Fred, but the surname escapes me and I believe he passed away in the 1980's. By all accounts he operated a steam winch though I never met him nor saw it in action. I believe that operation was dwindling and may have ceased operations about 1980. Any stories out there? Frank Whiteley "Bob Johnson" wrote in message ... Hi Bruce -- That's a very welcome correction to my hazily-remembered version of a second-hand report of what the 454 c.i. engine torque/hp/rpm chart looks like. This is the kind of info I was looking for and thanks for providing it! In all our past kicking around of the ideal winch prime mover, here's one that sounds silly but might rate at least an engineering investigation -- a recip steam engine! If I recall correctly, the steam engine develops max torque at stall. What got me thinking about that was the fact that the Navy gets 66,000 lb Super Hornets flying in about the same three seconds that it takes us to get airborne. And they do it with steam, not because it's handy, but that's probably the only practical way to get it done. BJ Bruce Hoult wrote: In article , Bob Johnson wrote: Our engine is petrol fueled. Despite Google's best efforts, I have not yet located a Torque/HP/RPM curve for our very common 7.4 L engine, but have heard that it develops max torque and HP at about 3000 RPM and further that the curves are fairly flat at this point. You are making some totally contradictory and inconsistent claims there. If max torque and max HP occur close together then they must both drop off precipitously after that. If the torque curve is flat then HP will be increasing linearly with RPM, max torque and max HP will be very far apart. It is quite likely that you do have maximum torque at around 3000 RPM, but if for example the torque curve is flat enough that the torque at the 5000 RPM redline is still 60% or more of that at 3000 RPM then that (redline) is exactly where maximum power will be. -- Bruce |
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