Wind mills

Discussion in 'Hangar Flying' started by Joe Fisher, Oct 27, 2018.

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  1. Nov 30, 2018 #181

    bmcj

    bmcj

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    Why remove the blades? Just place ‘snag’ hooks on the ends of the blades, then raise up a riser cable from the ‘base’jumper so that the blade hook catches it and lifts the jumper off the ground and slings him trebuchet-style up and over into an upward ballistic path. You can have contests to see who gains the most altitude before deploying. :roll:
     
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  2. Nov 30, 2018 #182

    Pops

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    You go first so I can watch how its done.
     
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  3. Nov 30, 2018 #183

    bmcj

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    Absolutely not... no way!

    it shouldn’t be done, but I know that just by putting out there, someone is going to read it and think that it’s a great idea, and you and I can smile as we sit on the sideline and watch it from a safe location. ;)
     
  4. Nov 30, 2018 #184

    Pops

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    Just checking, might be interesting to watch. Remind me not to do that :)
     
  5. Dec 1, 2018 #185

    Aesquire

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    I have some experience with trebuchetes. The exact angle of the release pin is critical, and dependent on arm speed. One speed, one weight of projectile, one angle. Vary any parameter and the angle has to change to optimize distance.

    Or you could brake the arm speed to compensate for projectile weight and a fixed angle.

    That leaves the initial position and vector of the projectile to tune. A Trebuchete traditionally starts the projectile close to, below and ahead of the pivot point for the arm. However, this is partially an artifact of the frame design that minimizes height ( and thus materials ) for a given arm length.

    To reduce climbing the tower, a rescue "snatch" system of cables based on the Fulton system could be used to pick the projectile up at ground level. https://en.m.wikipedia.org/wiki/Fulton_surface-to-air_recovery_system

    However, a failure in the system might result in the unlucky jumper being slung into the ground on the down stroke at maximum velocity. Assuming we can keep the G loading under human tolerance to prevent disassembly.

    Sandbag tests are prudent before human trials.

    Red Bull sponsorship?
     
  6. Dec 1, 2018 #186

    Pops

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    I know there was a reason I didn't want to be first :)
     
  7. Dec 1, 2018 #187

    Swampyankee

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    Coal companies are not responsible for payments to sufferers of black lung disease, which is only contracted by coal miners. Coal emissions are also very damaging to health and the environment, costs which are borne by local governments, health insurers, and individuals.
     
  8. Dec 1, 2018 #188

    Jerry Lytle

    Jerry Lytle

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    In an effort to bring this into the realm of Home Built Aircraft (or flying at least.) How many plane builders or wanabes have black lung desease?
    Just asking.
     
  9. Dec 1, 2018 #189

    BBerson

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    That's why individuals should demand a switch from coal to modern nuclear. (cleanest solution to global warming)
    Even the Union of Concerned Scientists recently switched to supporting of nuclear instead of opposing.
    Windmills just can't provide the base load people need. Society decides what we allow. My guess is a windmill operator won't be liable if a pilot hits it.
     
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  10. Dec 1, 2018 #190

    Aesquire

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    The earliest wind mills date from prehistoric middle eastern (modern Syria/Iraq/Iran ) ruins, often with extensive curved stone walls to duct the wind into the mechanism.

    Modern wind generation designs come from a WW2 german scientist/airplane designer, whose name I forget, so I put it up as a Contest for HBA members to look up.

    Contest!

    I've spent over 30 years studying the science and history behind the political/religious movement responsible for the OP's concern. However, site rules discourage religious arguments, which I agree to by participating.

    I'd much rather discuss catapulting people with 'chutes in a silly manner. For one thing, we'd need to add to the BASE jumper's acronym. ( building, antenna, span, escarpment (earth, cliff )) Then determine the maximum G loading we can accept on the human. I propose keeping them conscious to deploy their own chute be the standard.

    After all, if you need a remote or computerised chute deployment, we might as well strap the thrill seeker in a cage or ball and really create a money making thrill ride. The mind boggles with possibilities. Japanese game shows already have hillside mazes and pachinko machines for humans in balls.

    Introduce logic gates and create a https://en.m.wikipedia.org/wiki/Digi-Comp_II type manual computer with human carrying balls! Perhaps to determine order of launch from our converted wind mill/trebucete.

    https://shop.evilmadscientist.com/productsmenu/tinykitlist/375-dcii

    I had both the Digi Comp 1 & 2 as a child, and think they are still in storage somewhere.

    Or simply design a multi shot sling launch system to toss 3 jumpers per revolution, like a ski lift gone horribly right?
     
  11. Dec 1, 2018 #191

    BJC

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  12. Dec 2, 2018 #192

    lr27

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    I wonder how many waivers he had to sign and if there were more waivers than critical points of failure.

    ---------

    Aesquire:
    You should tell us what features make a wind turbine "modern". The old 1930's Jacobs wind turbine looks fairly modern to me.
    ML-on-tower.jpg
    Jacobs turbines were common in rural parts of the US, as were the simpler Wincharger turbines.

    The Smith-Putnam turbine had problems, but it was put up in 1941 and actually connected to the local electrical grid. Over a megawatt, although the blade design seems rather crude for a project with so much money behind it:
    SmithPutnam40sWndTrbn010307A.JPG
    http://www.wind-works.org/cms/index.php?id=223

    Anyway, I read someplace about some work in the 1940's by Ulrich Hutter in Germany. Is he the guy you were talking about?

    -----------

    As far as release for the jumper, these days you could have some inertial sensors and a little computer to release the tether as soon as the jumper stopped accelerating upwards. Then all we have to worry about is keeping him from hitting the blades or some other obstacle. Like maybe the next turbine over.

    Say we have a 100 meter diameter turbine and a 20 mph wind. As I recall, a tip speed to wind ratio of 10:1 is supposed to be pretty efficient. That's ONLY about 16.5 g's. Would probably make the jumper pass out at least, and that's not counting the initial acceleration when the tether hooks up. If the tether from the blade tip to the jumper was very long, the number might be higher.

    I wonder how far you could sling a pumpkin with an optimal turbine/trebuchet device?
     
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  13. Dec 2, 2018 #193

    lr27

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    P.S. Homebuilt turbines seem like they'd be appealing for airplane homebuilders, as long as there was a place where they wouldn't get in the way of aircraft. I might try one if I had a good place for one, but I think the neighbors would find an adequate tower quite ugly. The tower would probably have to be 80-100 feet to get well above the treetops. There's also a hill that rises about 300 feet higher than our house and blocks the prevailing wind.
     
  14. Dec 2, 2018 #194

    Aesquire

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    Ding Ding Ding! A winner!

    Thanks, Ulrich Hutter.

    https://en.wikipedia.org/wiki/Hütter_Hü_28
    https://www.soaringmuseum.org/glider_more.php?id=29

    for his aero props ;)

    https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19740008648.pdf
    http://www.telosnet.com/wind/20th.html

    Quote from above. In Germany, Professor Ulrich Hutter developed a series of advanced, horizontal-axis designs of intermediate size that utilized modern, airfoil-type fiberglass and plastic blades with variable pitch to provide light weight and high efficiencies. This design approach sought to reduce bearing and structural failures by "shedding" aerodynamic loads, rather than "withstanding" them as did the Danish approach. One of the most innovative load-shedding design features was the use of a bearing at the rotor hub that allowed the rotor to "teeter" in response to wind gusts and vertical wind shear. Hutter's advanced designs achieved over 4000 hours of operation before the experiments were ended in 1968.
     
  15. Dec 2, 2018 #195

    Aesquire

    Aesquire

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    I'm going to define "modern" here as some combination of "blades designed for windmills instead of propeller or sails/composite construction/variable pitch/load shedding/helicopter type hub" ...... Kinda like a patent application. I don't have emotional investment in the terminology, feel free to discuss.
     
  16. Dec 2, 2018 #196

    Aesquire

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    The actual release point can certainly be triggered by computer, and varied for speed, etc. to aim the jumper in the intended direction.

    It's not when acceleration ceases, not in a Trebuchete version. It's hard to tell from videos, but the acceleration of the Arm slows & stops as soon as the weight passes directly below, and gravity acts to slow it. But.... there's a sling involved, and the lag means that maximum velocity on the object in the sling is such that a maximum speed release would toss the projectile into the ground. ( assuming level ground ) Angle at release? A bunch of factors but a WAG based on playing with these things is 30-60 degrees down vector from horizontal on release. For altitude or distance, you release much earlier than that. Before the arm reaches vertical. Too soon and the rock comes straight back down. AMHIK. Sling physics apply.

    I am also assuming a modified Fulton system to load the riders, but it's a bit scary with the sling length.

    Skipping that complication, you have the issue of G loading. Blade tip speed is far slower than sling speed. To keep it under a nominal 9 g's ( fighter pilots fight to stay conscious ) the blade rotation would have to be reduced to "stately".

    If you didn't need to care about the payload's comfort, say, a weather drone/probe launcher application, just having the blade hook a sling on the way by in high winds would be fun to watch.

    I'm going to have to write the next Mad Max movie, since the notion of converting old windmills to catapults tossing fire balls at someone.... dang. You have to imagine car tire armor and land sail barges, lots of spikes and other post apocalyptic imagery.

    If you decide to go for "cup & arm" type I have no idea how you plan to load the jumpers.

    Edit: I just "googled" sling physics with it set on images, and it's all so obvious in pictures.
     
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  17. Dec 2, 2018 #197

    lr27

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    I wrote acceleration in the upwards direction, assuming we're trying for the most altitude and flight time. That seemed to be the objective in the video with the two cranes.

    I dunno. When I think of "post apocalyptic imagery", I envision cockroaches and bacterial mats. ;-p
     
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  18. Dec 2, 2018 #198

    Pops

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    And I thought I was strange :) :)
     
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  19. Dec 2, 2018 #199

    lr27

    lr27

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    Not strange. Realistic, at least if we set off all the nukes.
     
  20. Dec 2, 2018 #200

    mcrae0104

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    What is this, 1964?

    Sheesh.

    Airplanes, anyone?
     

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