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

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

Originally Posted by BBerson
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. ## Re: How many pounds of thrust can I expect to generate?

Originally Posted by BBerson
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. ## Re: How many pounds of thrust can I expect to generate?

Originally Posted by bmcj
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

4. ## 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. ## 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. ## 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. ## 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. ## 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.

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

Originally Posted by BBerson
The late Paul McCready said a human powered helicopter would need 150 feet rotor diameter.
BB
Or a few smaller rotors.
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here is a nice movie too
http://www.youtube.com/watch?v=caHCbuh_Yyc

Seb

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

Originally Posted by autoreply
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. ## Re: How many pounds of thrust can I expect to generate?

Originally Posted by BBerson
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

Originally Posted by Dan Thomas
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. ## Re: How many pounds of thrust can I expect to generate?

Originally Posted by HumanPoweredDesigner
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. ## Re: How many pounds of thrust can I expect to generate?

Originally Posted by Dan Thomas
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. ## Re: How many pounds of thrust can I expect to generate?

Originally Posted by autoreply
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

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