Help Design a Human-Powered Helicopter

Phrak

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

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

[tex]v^2 = ar[/tex]

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

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

Damn, if they can do 600W for 6 mins thats extremely impressive.

mheslep

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 5 min 36 s. over 2000 meters. That's a continuous power output 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

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

mheslep

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

I just showed you a calculation concerning the power.


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.

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

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