+ Reply to Thread
Page 2 of 10 FirstFirst 12345678 ... LastLast
Results 16 to 30 of 142

Thread: How many pounds of thrust can I expect to generate?

  1. #16
    Registered User HumanPoweredDesigner's Avatar
    Join Date
    Sep 2009
    Location
    Arizona
    Posts
    1,030

    Re: How many pounds of thrust can I expect to generate?

    Quote Originally Posted by BBerson View Post
    About a week ago Sikorsky announced that the human powered helicopter cash prize has been increased from $25,000 up to $250,000.

    Lift yourself to a 10 foot hover for minute, I think.

    Not that easy.
    I like those kind of offers. Only thing I don't like is huge teams of professors with access to advanced materials and machine shops building something highly non-portable and which is weak at other stuff and just good enough to win the prize money.

    Anyway, the HPV that went across the english channel was powered by at least 0.4 hp from an amature. My estimate is I can put out at least 0.33 hp. So those are my numbers. It took him almost 3 hours, too.

    I got to get this thing light, and get the drag down. I think lower aspect ratio gets it lighter, and wingtip fences helps with tip drag. I know I can do better than the one that amature rode. Just a matter of if it is good enough to be worth building.

    Needs to climb at least 1 foot per second, lifting a total mass of at least 200 pounds. How many watts is that? 1/3 M, 100kg, 10m/s2 = 300 watts?

    Plus I need 1/3 hp just to fly it, so another 250. So 550 watts to fly and climb. I wonder how long an amature like me can keep that up for. 1 minute = 60 feet climbed. 2 hours to get to 6000 feet. Maybe Lance Armstrong could do 550 watts for 2 hours. That is a long time to get up high. And circling would cause lost lift. 2 hours at 10 mph = 20 miles travelled.

    Yep. I think HPVs can be done, but you'd need like 600 watts maintained for 2 hours. What do you guys think? Just make that amature cyclist's plane more efficient? Or am I describing a death sentence?

  2. #17
    Registered User bmcj's Avatar
    Join Date
    Apr 2007
    Location
    Fresno, California
    Posts
    7,566

    Re: How many pounds of thrust can I expect to generate?

    Quote Originally Posted by BBerson View Post
    About a week ago Sikorsky announced that the human powered helicopter cash prize has been increased from $25,000 up to $250,000.

    Lift yourself to a 10 foot hover for minute, I think.

    Not that easy.
    The synopsis I read wasn't clear on whether it had to maintain 10' for 60 seconds or just reach 10' sometime during the 60 seconds. Do you know which is required?

  3. #18
    Registered User BBerson's Avatar
    Join Date
    Dec 2007
    Location
    Port Townsend WA
    Posts
    4,750

    Re: How many pounds of thrust can I expect to generate?

    Quote Originally Posted by bmcj View Post
    The synopsis I read wasn't clear on whether it had to maintain 10' for 60 seconds or just reach 10' sometime during the 60 seconds. Do you know which is required?
    You are right Bruce,
    4. Flight Requirements

    4.4.1 The flight requirements shall consist of hovering for one minute while maintaining flight within a 10-meter square. During this time the lowest part of the machine shall exceed momentarily 3 meters above the ground.

    4.4.2 The machine shall be in continuous flight from takeoff to landing, and at no time during the flight shall any part of the machine touch the ground.

    4.4.3 A reference point on the non-rotating part of the machine will be established an a means whereby the observers can judge that the machine stayed within the confines of the 10-meter square.

    4.4.4 The one minute hovering time and the momentary achievement of 3 meters altitude is required to win the AHS prize. (However, the FAI 1980 regulations specify that only the duration of the flight and a momentary achievement of 3 meters altitude will be recorded for the FAX world record attempt, making it possible to achieve a world record without satisfying the AHS prize requirements.)

    rules:http://www.vtol.org/awards/hphregs.html#hph_toc
    Last edited by BBerson; September 6th, 2009 at 06:59 PM. Reason: add website

  4. #19
    Registered User HumanPoweredDesigner's Avatar
    Join Date
    Sep 2009
    Location
    Arizona
    Posts
    1,030

    Re: How many pounds of thrust can I expect to generate?

    I'll make a human powered vehicle just to win some prize money. Then use a mini motorcycle engine (5 hp) for when I fly for fun. Same airplane. Multiple set ups.

    The money is good. But I'm not really interested in helicopters. I guess for $250,000 I can become interested.

  5. #20
    Registered User HumanPoweredDesigner's Avatar
    Join Date
    Sep 2009
    Location
    Arizona
    Posts
    1,030

    Re: How many pounds of thrust can I expect to generate?

    OK. I got a design for the helicopter. I can go get that prize money. Only I got to be strong enough to squat my own weight for 1 minute. I know how to keep it from spinning. The hard part is keeping it from tipping over. One way is to angle the blades up a bit, but then I'd lose lift. I could anlge them just a tad though.

    If I use a patented feature, do I have to pay them some of the prize money? Or do patented designs only apply to sales production?

  6. #21
    Registered User HumanPoweredDesigner's Avatar
    Join Date
    Sep 2009
    Location
    Arizona
    Posts
    1,030

    Re: How many pounds of thrust can I expect to generate?

    On problem with helicopter blades is they must be strong if they are big.

    Strictly from a strength perspective, how thick would the blades have to be to carry 180 pounds? If they are 10 feet in diameter?

  7. #22
    Moderator addaon's Avatar
    Join Date
    Feb 2008
    Location
    San Jose, CA
    Posts
    1,657

    Re: How many pounds of thrust can I expect to generate?

    If you can pull it off for less than $250k, I think you'll get a lot of industry interested as well.

  8. #23
    Moderator autoreply's Avatar
    Join Date
    Jul 2009
    Location
    Leiden, Netherlands
    Posts
    8,410

    Re: How many pounds of thrust can I expect to generate?

    Well, you need to have at least 30' of radius, probably much more, think about 50' That's rather hard while building a light construction (under 150 lbs) and also imaging the countertorque-device..


    125 kg's, 250 watts

    So induced velocity is 0.2 m/s, which yields a huge rotor

    In turn that's about 70 meters (210') of radius, or 140 meters (420') of diameter... good luck.
    Last edited by autoreply; September 7th, 2009 at 06:46 AM.

  9. #24
    Registered User BBerson's Avatar
    Join Date
    Dec 2007
    Location
    Port Townsend WA
    Posts
    4,750

    Re: How many pounds of thrust can I expect to generate?

    The late Paul McCready said a human powered helicopter would need 150 feet rotor diameter.
    BB

  10. #25
    Registered User Mac790's Avatar
    Join Date
    Jun 2008
    Location
    Poznan, Poland
    Posts
    1,569

    Re: How many pounds of thrust can I expect to generate?

    Quote Originally Posted by BBerson View Post
    The late Paul McCready said a human powered helicopter would need 150 feet rotor diameter.
    BB
    Or a few smaller rotors.
    YouTube - 人力ヘリ&#2 27;‚³ãƒ—ã‚¿ YURI-I 日本記éŒ&#17 8; 樹立

    here is a nice movie too
    http://www.youtube.com/watch?v=caHCbuh_Yyc

    Seb
    Last edited by Mac790; September 7th, 2009 at 10:33 AM.
    Amor Patriae Nostra Lex

    "Time, training, training, training and more training is the key to any success."
    Francis "Gabby" Gabreski

  11. #26
    Registered User Dan Thomas's Avatar
    Join Date
    Sep 2008
    Posts
    3,086

    Re: How many pounds of thrust can I expect to generate?

    Quote Originally Posted by autoreply View Post
    First of all, get used to SI-units. No stupid correction factors or whatever and at least the rest of the world understands it as well

    Regarding the numbers, those numbers are less or more ballpark figures.
    See this and tell me where I'm wrong:
    SI Metric System Conversion Table Units hand horsepower joules to cm watts or other units

    Dan

  12. #27
    Moderator autoreply's Avatar
    Join Date
    Jul 2009
    Location
    Leiden, Netherlands
    Posts
    8,410

    Re: How many pounds of thrust can I expect to generate?

    Quote Originally Posted by BBerson View Post
    The late Paul McCready said a human powered helicopter would need 150 feet rotor diameter.
    BB
    If you assume around 1500 watts that's the ballpark figure, not accounting losses, control and so on. Still rather large and from a structural point of view unlikely to be achieved.
    Most current attempts rely on ground effect. Allthough nice and helping enormously with just lifting of it isn't going to help you much getting to 10'. Control is horrible, how about the gyroscoping reactions of a 150' disc

    Quote Originally Posted by Dan Thomas View Post
    Just a general rant against Americans doing it "different", nothing wrong with what you wrote. SI really is easier, no stupid correction factors and so on. (550 foot-pound, multiply by 3.6, 1.852 or 1.6, metric versus short tons, lbs vs tons versus gallons, crashing Mars landers and so on)
    But then again, I'm from a insignificant country you can fly across in 4 minutes..

  13. #28
    Registered User Dan Thomas's Avatar
    Join Date
    Sep 2008
    Posts
    3,086

    Re: How many pounds of thrust can I expect to generate?

    Quote Originally Posted by HumanPoweredDesigner View Post
    On problem with helicopter blades is they must be strong if they are big.

    Strictly from a strength perspective, how thick would the blades have to be to carry 180 pounds? If they are 10 feet in diameter?
    Helicopter rotors don't depend on stiffness to carry the weight of the machine. They rely on the centrifugal forces generated by the weighted rotor tips. The rotor tach has a rather narrow green band where the pilot must maintain the rotor speed lest the blades cone excessively and drag eventually kills the whole thing, or centrifugal forces get too high and something fails.

    So a huge, low-speed rotor isn't going to work unless it has a lot of internal strength, which means too much weight, or external wires, which add plenty of drag. Smaller but faster rotors lose hp to drag.

    Dan

  14. #29
    Moderator autoreply's Avatar
    Join Date
    Jul 2009
    Location
    Leiden, Netherlands
    Posts
    8,410

    Re: How many pounds of thrust can I expect to generate?

    Quote Originally Posted by Dan Thomas View Post
    So a huge, low-speed rotor isn't going to work unless it has a lot of internal strength, which means too much weight, or external wires, which add plenty of drag. Smaller but faster rotors lose hp to drag.

    Dan
    That's not true. If you imagine the 150' diameter rotor, that's probably going to turn at about 120 rpm. That's still (V^2/R) about a 100 g's, so plenty to keep the rotor flat. Turning much slower isn't possible because your foils will simply be too ineffective (low reynolds) Higher speed isn't always bad for performance

  15. #30
    Registered User Dan Thomas's Avatar
    Join Date
    Sep 2008
    Posts
    3,086

    Re: How many pounds of thrust can I expect to generate?

    Quote Originally Posted by autoreply View Post
    That's not true. If you imagine the 150' diameter rotor, that's probably going to turn at about 120 rpm. That's still (V^2/R) about a 100 g's, so plenty to keep the rotor flat. Turning much slower isn't possible because your foils will simply be too ineffective (low reynolds) Higher speed isn't always bad for performance
    At 120 RPM the tip speed of a 150' rotor will be 643 MPH. Far too high and swallowing an awesome amount of power, certainly not human-powered. The max tip speed of the Bell 206's 33.3' rotor is 468 MPH. The tip speed of the MIL 26's 104' rotor is 490 MPH, the Hughes/MD 500E's is 464 MPH. Anything above such speeds limits the forward speed of the helicopter as the advancing blade starts to generate far too much noise and drag.

    And 100 Gs of what? A really light rotor? We need weight at the tips to make this work, adding to the weight of the machine. Helicopters have to be one of the most inefficient modes of transport ever devised by man, one step up from the stoneboat. We only use them because they can land and take off and place loads in tiny places. A human-powered machine will be made of unobtainium and powered by a steroid-saturated beast.

    Dan

+ Reply to Thread
Page 2 of 10 FirstFirst 12345678 ... LastLast

Similar Threads

  1. Thrust vs. Weight
    By Lucidguy in forum General Experimental Aviation Questions
    Replies: 10
    Last Post: September 5th, 2009, 11:51 PM
  2. Panther 2 Thrust angle problem
    By Richard Olmsted in forum General Experimental Aviation Questions
    Replies: 1
    Last Post: April 29th, 2009, 11:22 AM
  3. How to calculate static thrust?
    By leviterande in forum General Experimental Aviation Questions
    Replies: 9
    Last Post: October 22nd, 2008, 06:44 AM
  4. Expect the Unexpected! (Flight testing)
    By Tinbuzzard in forum Rules and Regulations / Flight Safety / Better Pilots
    Replies: 3
    Last Post: May 2nd, 2005, 02:44 PM
  5. Using a peltier to generate electricity
    By dustind in forum General Experimental Aviation Questions
    Replies: 7
    Last Post: August 30th, 2004, 02:37 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts