Help Design a Human-Powered Helicopter

[M Grandin]

If "Gossamer" manpowered planes work, at least I cannot see anything preventing two such planes connected together circulating around a common center = "helicopter". That may be boiled down to a man powered helicopter where the rotor is not driven by center shaft, but from from smaller propellers at rotor wing ends. Wing units (perhaps several parallel layers as in WWI combat planes) behind towing propellers, placed rather far out from center
shaft. Propellers could be driven by wires as in garden trimmers.

I agree it may appear less efficient letting rotor be towed by propeller - but I can see
gossamer planes (towed by propeller) lift while manpowered helicopters (driven by center shafts)
don't lift. In aerodynamics not always common sense applies.

Sorry, according to http://flight.engr.ucdavis.edu/~smlarwood/documents/LarwoodSaiki1990.pdf
that kind of solutions have earlier been developed. But evidently not a success. At least not
hitherto.

 

[Cyrus]

I've read every paper on this subject and will be happy to answer any questions. I will say this, it's certainly possible, but you walk a very fine line. I see a lot of misinformation being stated in this thread.

Fred, PM me your email address. I can't send you pms because you have it turned off.

 

[Mech_Engineer]

It seems to me that for a helicopter to achieve free flight (outside of the ground effect) it needs to push enough air down to have sufficient mass flow to maintain altitude. Based on the power requirements of other helicopters which are engine powered, it would have to have more than 10 horsepower available, far more than any bicyclist can achieve.

Edit- any 130-lb bicyclist anyway. Weight is the #1 killer on these things.

 

[Cyrus]

It seems to me that for a helicopter to achieve free flight (outside of the ground effect) it needs to push enough air down to have sufficient mass flow to maintain altitude. Based on the power requirements of other helicopters which are engine powered, it would have to have more than 10 horsepower available, far more than any bicyclist can achieve.

Edit- any 130-lb bicyclist anyway. Weight is the #1 killer on these things.

No, this is wrong and not based on any sort of calculation. Run the numbers and you will find you are off by an order of magnitude.

You are about right on the weight of the cyclist though.

 

[BenchTop]

Do the rules prohibit offsetting the load with, say, lighter than air wings?

 

[Cyrus]

Do the rules prohibit offsetting the load with, say, lighter than air wings?

Lighter than air construction, and energy storage devices are explicitly prohibited. Check out the www.vtol.org website for the official rules, which goes over everything in detail.

 

[Cyrus]

After looking at the rules, I believe the contest is doable. It only says you need to momentarily exceed 3 meters and total hover time is only 1 min. A cyclist can put out a lot more power for 1 min than s/he can for three hours.

Just keep in mind, this is nowhere close to the achievment of the Gossamer Albatross, which actually had sustained, controllable flight for close to 3 hours. This "helicpoter" prize seems pretty pointless to me.

Then you need to study helicopters so you won't make such a naive statement! This is, in fact, harder, than a human powered airplane. McCready said so himself - if you don't know who he is Google him.

 

[Phrak]

I had a thought (beware)...

A lot of stuctural weight is required to support the pilot in the middle.

http://www.humanpoweredhelicopters.org/yuri1/YURI_1.jpg

Now, it's well established by the Gossamer Albatross that a single Bryan Allen can power a plane over a comparatively long time span in straight and level flight. Flying in circles would require a bit more work, but over a shorter span of time.

Four of these things,

http://www.bfi.org/images/content/frontpage_events/gossamer.jpg

tethered to fly in a circle, mutually constrained by relatively light weight struts and cables, and powered by four Bryan Allens would be capable of achieving the desired result.

The craft should have an overall diameter of about 400 feet. That would take a big gymnasium.

 

[Phrak]

Useless facts. The largest hanger in the world wouldn't be enough.

http://www.distant.ca/UselessFacts/fact.asp?ID=165

"CargoLifter hangar, located in Brand, Germany (60 kilometres south of Berlin) on a former Soviet military airport, is the largest self-supporting hangar in the world. With 360-meters in length, 210-meters in width and 107-meters in height the hanger was designed to accommodate the planned CargoLifter CL 160, a 260-meter long airship."

Self propelled helicoptering should be an outdoor sport.

 

[Cyrus]

Useless facts. The largest hanger in the world wouldn't be enough.

http://www.distant.ca/UselessFacts/fact.asp?ID=165

"CargoLifter hangar, located in Brand, Germany (60 kilometres south of Berlin) on a former Soviet military airport, is the largest self-supporting hangar in the world. With 360-meters in length, 210-meters in width and 107-meters in height the hanger was designed to accommodate the planned CargoLifter CL 160, a 260-meter long airship."

Self propelled helicoptering should be an outdoor sport.

Provided you have very calm winds, yes. Large indoor areas pose problems because the circulation of the air inside the (Gymnasium!) as a result of the induced velocity will cause the rotorcraft to inevitable drift outside the limits of the (10?) meter box.

 

[Phrak]

Provided you have very calm winds, yes. Large indoor areas pose problems because the circulation of the air inside the (Gymnasium!) as a result of the induced velocity will cause the rotorcraft to inevitable drift outside the limits of the (10?) meter box.

It may be moot, since the widest indoor flat area I could find was about 260 meters, but I'm not following. The helicopter will induce some toroidal flow of air--up on the outside, and down in the middle. Will off-center cause positive feedback to draw it further off-center?

 

[Mech_Engineer]

No, this is wrong and not based on any sort of calculation. Run the numbers and you will find you are off by an order of magnitude.

You are about right on the weight of the cyclist though.

What formulas should I be using to calculate the required power for a helicopter?

I looked at it from a thrust standpoint, and used the weight of the DaVinci III as a guide for human-powered helicopter dimensions. With a weight of 227 pounds, and an induced wind velocity of 35 mi/hr (I just guessed at this, the DaVinci III report had no specs), you have to push 142 lb/s of air for a total of 111,600 cfm, and that works out to 10.5 horsepower required to gain stable flight outside of the ground effect.

 

[Cyrus]

What formulas should I be using to calculate the required power for a helicopter?

I looked at it from a thrust standpoint, and used the weight of the DaVinci III as a guide for human-powered helicopter dimensions. With a weight of 227 pounds, and an induced wind velocity of 35 mi/hr (I just guessed at this, the DaVinci III report had no specs), you have to push 142 lb/s of air for a total of 111,600 cfm, and that works out to 10.5 horsepower required to gain stable flight outside of the ground effect.

You should write and run a BEMT code. I have no idea where your ad-hoc numbers come from. As a first order analysis, you could just use momentum theory itself (which does not require any code).

$$P = T^{3/2}/\sqrt{2\rho A}$$

Using R = 50' and T = 227lb, the power is 559.59 (whatever units it is fl-lb/s, or something...) or about 1.01 HP. This is obviously a first order analysis and one would have to use BEMT for better estimates at HOGE. An order of magnitude less than your estimate! (And we have not even gotten into any of the actual hard technical challenges!)

 

[russ_watters]

Then you need to study helicopters so you won't make such a naive statement! This is, in fact, harder, than a human powered airplane.

You misunderstood my point. I know it is harder than a human powered airplane - and that's why they have to make the prize for such a small achievement.

In other words, you can't fly this thing across the English Channel.

 

[Cyrus]

You misunderstood my point. I know it is harder than a human powered airplane - and that's why they have to make the prize for such a small achievement.

In other words, you can't fly this thing across the English Channel.

My bad. You would have a hell of a time flying this thing even in a straight line! The power requirements are horrible, and the rotation of the blades mean the stresses quickly kill you, because things have to be build bulkier. It's a hell of a problem compared to the human powered airplane (HPA).

 

[Phrak]

http://en.wikipedia.org/wiki/Momentum_theory"

http://en.wikipedia.org/wiki/Blade_element_theory"

 

[Phrak]

My hopes are dashed (see my post #43) by the following outlandish rule...

http://www.vtol.org/awards/hphregs.html#4 .

4.1.2 The machine shall be a rotary wing configuration capable of vertical takeoff and landing in still air, and at least one member of the crew shall be non-rotating.

Or...I will require a freshly made, newborn volunteer, as light in weight as possible, to function as the fifth crew member, suspended in a non rotating, centrally located bassinette.

 

[Phrak]

After more internet searching than I expected in order to circumvent infant labor laws, I discovered that the "world's smallest midget" is 28 inches tall. With some proportional comparison, this yields a nominal body weight of 18 pounds. Erroring on the conservative side, I expect to obtain the services of a 25 pound dwarf to provide the requisite fifth, non-rotating crew member.

After providing for a crash cage and mechanism to provide non-rotation of the central crew member plus the supporting cables, the central mass should weigh an effective 50 pounds. With four cables tensioned at 200 pounds apiece running to each Condor pilot's center of lift, the fifth pilot should be suspended at an altitude of 1/16th the flight radius below each Condor's lifting surface.

After some back of the envelope considerations, the flight radius of each Condor should be about 400 feet. This implied that the fifth pilot will be suspended 25 feet below the lifting blades.

To meet the requirement:

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.

the blades will be required to obtain 35 feet of altitude + 3 feet of suspended fifth pilot = 38 feet. This is within some small ground effect for each Condor (wingspan of 100 ft.).

The overall diameter of the Helicopter will be about 900 ft.

 

[Phrak]

Will each Condor provide the centrifugal force necessary to tension the cables to the 5th crew member?

Each Condor will obtain about 25 feet per second, based upon the information from Wikipedia.

Using

$$v^2 = ar$$

were v =25 feet per second
and r = 400 feet

The centripital acceleration of each Condor will be 1.6 foot pounds per sec². The mass of each Condor will be about 32 Kg plus pilot (wikipedia reference, again).

After some calculations, each Condor is capable of providing only 10 pounds of radial force to hold up the fifth crew member. This is unacceptable.

Ideas anyone?

 

[mheslep]

I'll absolutely dismiss it. The power that can be provided by a good cyclist is somewhere in the area of 300 W. Not only will you be hard pressed to find a very light person that can put out that kind of continuous power, ...

It's not very continuous, but olympic calibre athletes can do work at 600W for 6 minutes. Such an athlete might helo across a hefty lake then, never the channel.

 

[Cyrus]

It's not very continuous, but olympic calibre athletes can do work at 600W for 6 minutes. Such an athlete might helo across a hefty lake then, never the channel.

Damn, if they can do 600W for 6 mins that's extremely impressive.

 

[mheslep]

Damn, if they can do 600W for 6 mins that's extremely impressive.

To my mind, olympic rowers in these time frames (6 minutes), out perform any other athlete type.
The athletes are frequently tested on ergometers (flywheel machines). The world record a few years ago was http://en.wikipedia.org/wiki/List_of_world_records_in_rowing#Indoor_Records" of 590W, i.e. work done on the machine. Over 500M (1m 16s) these guys can exceed 1HP. I've tested at the 2k distance a hundred times in competition and came in, ehem, somewhat lower. The typical top 10 school college rower (male) will rate at about 430W.

BTW, the do-it-yourself helo would have to hold that record holder's 97kg, 2m to get that power:

 

[FredGarvin]

It's not very continuous, but olympic calibre athletes can do work at 600W for 6 minutes. Such an athlete might helo across a hefty lake then, never the channel.

Yeah. I wouldn't use that as a data point. Those are definitely outliers from the norm.

 

[mheslep]

Those are definitely outliers from the norm.

So is this idea of a human powered helo.

 

[Mech_Engineer]

The point is that a helicopter like is being proposed needs at least 1hp (745W) to fly (I'm still convinced it would be more, but flying within the ground effect does help). The problem is, every pound kills you, and "successful" designs like the Davinci III only had an available payload of 59kg (130lb) for the pilot. Even powerful professional athletes which are significatly heavier cannot sustain that kind of output for very long.

 

[Cyrus]

The point is that a helicopter like is being proposed needs at least 1hp (745W) to fly (I'm still convinced it would be more, but flying within the ground effect does help).

I just showed you a calculation concerning the power.

The problem is, every pound kills you, and "successful" designs like the Davinci III only had an available payload of 59kg (130lb) for the pilot. Even powerful professional athletes which are significatly heavier cannot sustain that kind of output for very long.

That's right exactly right, and the power goes with the weight^(3/2).

 

[Phrak]

Does anyone know how high Allen flew crossing the English channel?

My second question would be, what is ground effect as a function of wingspan?

Edit: I've been searching for Bryan Allen's estimated power output and weight while crossing the channel and haven't found them.

 

[FredGarvin]

Ground effect is essentially any height below one rotor diameter.

The aircraft was powered using pedals to drive a large two-bladed propeller. Piloted by amateur cyclist Bryan Allen, it completed the 35.8 km (22.2 mi) crossing in 2 hours and 49 minutes, achieving a top speed of 29 km/h (18 mph) and an average altitude of 1.5 metres (5 feet).

The empty mass of the structure was only 32 kg (71 lb), although the gross mass for the Channel flight was almost 100 kg (220 lb). To maintain the craft in the air it was designed with very long tapering wings (high aspect ratio), like those of a glider, allowing the flight to be undertaken with a minimum of power. In still air the required power was of the order of 0.4 horsepower (300 W), though even mild turbulence made this figure rise rapidly.

 

[Phrak]

That's nearly full ground effect. The root of the wing was maybe 10 feet and the tips another 10 feet or so. This compares to a span of 100 feet.

I would expect that ground effect is exponential decaying with height.

I think I should discover the difference in total ground effect to none. That is "What is the maximum percent gain in lift due to ground effect?"

 

[Phrak]

Didn't you like my last post Fred? This thread is about a contest with no practical application, isn't it?

 

[Phrak]

Fred, on a more serious note, the contents of prize state nothing limiting supporting equipment. Ground effect could be sustained throughout the required excursion to 10 feet by ducting the blades with a circular fence.

How are you at hovercraft ducted fans?

 

[Mech_Engineer]

Fred, on a more serious note, the contents of prize state nothing limiting supporting equipment. Ground effect could be sustained throughout the required excursion to 10 feet by ducting the blades with a circular fence.

How are you at hovercraft ducted fans?

You couldn't have a giant duct, because the rules state the lowest part of the "helicopter" has to attain the maximum height. The bottom portion of the "ducts" would therefore have to reach the height.

I doubt you could justify such a system weight-wise anyway.

 

[dr dodge]

"4.1.4 No devices for storing energy either for takeoff or for use in flight shall be permitted. Rotating aerodynamic components, such as rotor blades, used for lift and/or control are exempt from consideration as energy storing devices"

couldn't you use multiple staged rotors with a gearing so it took maybe an hour to get everything rotating in a "no lift mode" then after critical rotation is reached, pull on the stick to get the pitch needed. during "run up" with a rotor not fighting for lift, I would think rotational velocity could be brought up high enough that inertia would then help keep it rotating with less immediate power needed?

just a little sprinkle to add to the current brainstorm

dr

 

[Cyrus]

"4.1.4 No devices for storing energy either for takeoff or for use in flight shall be permitted. Rotating aerodynamic components, such as rotor blades, used for lift and/or control are exempt from consideration as energy storing devices"

couldn't you use multiple staged rotors with a gearing so it took maybe an hour to get everything rotating in a "no lift mode" then after critical rotation is reached, pull on the stick to get the pitch needed. during "run up" with a rotor not fighting for lift, I would think rotational velocity could be brought up high enough that inertia would then help keep it rotating with less immediate power needed?

just a little sprinkle to add to the current brainstorm

dr

Why on Earth would you do such a thing? Think of it this way, what do you think will happen to the stresses at the hub when you suddenly dump the collective? The change in AoA will give a large impulsive pitching moment - bye bye blades.

 

[Phrak]

You couldn't have a giant duct, because the rules state the lowest part of the "helicopter" has to attain the maximum height. The bottom portion of the "ducts" would therefore have to reach the height.

I doubt you could justify such a system weight-wise anyway.

The fence or duct is attached to the ground, not the helicopter.