h a l f b a k e r yMagical moments of mediocrity.
add, search, annotate, link, view, overview, recent, by name, random
news, help, about, links, report a problem
browse anonymously,
or get an account
and write.
register,
|
|
|
Pedal powered aeroplanes just about work. But the power our legs can create is a little low for flight, if you're not an athlete.
How about if you don't aim for full flight, but a pedal-powered winged vehicle that can just get its small wheels a foot off the ground. This would enjoy the benefits
of the Ground Effect; a large boost in lift noticed by hang gliders and pilots just above the ground. Vehicles have been designed to just fly in this "sweet-spot", giving them huge lifting capabilities, and fuel saving (Called Ground Effect Vehicles, or Ekranoplans).
I propose a frame work like a Recumbent bike as these have less drag than an upright bike. Relatively Short but wide wings optimised for this use are attached low down to the frame. The pedals would power one or two propeller mounted on the front. To reduce drag a fairing is fitted. The wheels could be minimised if weight needs to be reduced, as they're only needed for take off now. Basically its Recumbent bike meets Ekranoplan.
Hopefully pedalling like fury on a flat surface gets the thing airborn, giving no ground friction, and a host of surfaces you can 'skim' over. Its strong points could by skimming over rough terrain at good speed (but not too undulating), grass fields, sand, swamps or even water courses. You just need a flat surface to take off/land.
Just don't run out of puff half way across a lake!
Recumbent Bike
http://www.velokraft.com/nocom.html
The frame could be based on this minimal light design [Bal, Oct 04 2011]
Ekranoplan
http://www.darkroas...plans-showcase.html
The russians built huge Ground Effect Vehicles in the 60's. Speed of a plane / weight of a boat. [Bal, Oct 04 2011]
Human powered walker
http://springwalker.com/
Halfbaked, and pedal powered. [rcarty, Oct 09 2011]
If this worked I would want one. Until then these look promising.
http://www.gizmag.com/go/6864/
[2 fries shy of a happy meal, Oct 09 2011]
A great big one
http://englishrussi...0/03/12/ekranoplan/
Exhibit A [Alterother, Oct 09 2011]
Some more
http://www.yachtbou...Ekranoplanintro.htm
Exhibit B (see 'Islander', near bottom of page) [Alterother, Oct 09 2011]
Specs on the Lun-class
http://en.wikipedia...un-class_ekranoplan
What it says on the box. [Alterother, Oct 09 2011]
Specs on the A380
http://en.wikipedia.org/wiki/Airbus_A380
Comparable to Lun-class ekranoplan in both dimensions and load cap. [Alterother, Oct 09 2011]
Bad sketch, but you get what I mean.
http://s68.photobuc...widget_action=album
[2 fries shy of a happy meal, Oct 10 2011]
pedal powered boat record is a pontoon airboat....streamlined .
http://lancet.mit.edu/decavitator/
i doubt adding wings would substantially reduce drag and increase speed. [teslaberry, Sep 19 2014]
Magnus Effect
https://en.wikipedi.../wiki/Magnus_effect
spinning balls [unhelpful_fool, Jul 07 2019]
Flettner Rotor
https://en.wikipedi...wiki/Flettner_rotor
spinning tubes [unhelpful_fool, Jul 07 2019]
Wikipedia: Airborn
https://en.wikipedi...iki/Airborn_(novel)
Not to be confused with "airborne". The novel's name refer to the protagonist having been born while airborne, IIRC. [notexactly, Jul 21 2019]
Heirborn - Airborne (album cover art)
https://i.redd.it/ibyj9hiiych21.png
Another "not to be confused with" [notexactly, Jul 21 2019]
Please log in.
If you're not logged in,
you can see what this page
looks like, but you will
not be able to add anything.
Destination URL.
E.g., https://www.coffee.com/
Description (displayed with the short name and URL.)
|
| |
The main problem is that propellors are less
efficient than wheel-power, which gives me an
idea... |
|
| |
[+] on take off might I suggest pre-winding a spring, in order to give a big push to overcome the drag of the wheels. |
|
| |
...Following on from [Max]'s comment - why not make the propulsion similar to that of a hydrofoil ie an offsett propellor hung into the water for more efficient thrust... |
|
| |
Steering would be difficult. At the heights this is
going to achieve banking isn't going to cut it. You'd
need pure rudder steering, which should be feasible,
but you aren't going to make sharp corners. |
|
| |
The perfect aircraft for people who want to fly really,
really slowly, but find dirigibles too boring. |
|
| |
I suppose one can always get one's manservant to do the pedalling, so a two seater version perhaps? |
|
| |
It would work in theory. The addition of a front aero foil would prevent dipping. Now.... Off you go me lad and construct one. Don't forget to post photos (No blood please). |
|
| |
And here we have the origin of the most ridiculously
awesome sport ever. |
|
| |
//for people who want to fly really,really slowly,...//
Oh.... man, Where can I get me some of that? |
|
| |
[FT] is right, you need an initial boost, at the very least. And I think the jury might still be out on whether you could sustain this under your own power. You must remember this effect is a result of the forward motion of the craft. Like a bow wave. I don't think I have seen an "Ekranokraft" with fewer than eight engines. |
|
| |
They definitely aren't the most efficient way to sort of fly
very low over flat surfaces. Watch out for trees and sheep. |
|
| |
Just for the record, it is [The Alterother]'s opinion that
while ekranoplans may not be the best GEV design ever to
achieve liftoff, they are still pretty cool. William Gibson is
partially to blame for this. |
|
| |
// I don't think I have seen an "Ekranokraft" with fewer
than eight engines. // |
|
| |
There are some little 4-6 seaters that have twin props, and
a few mid-sized models. Good luck trying to find any more
than a picture of them, though. From what I can find on
the web, most of the little ones are either in use as island-
hoppers in the Pacific or in Russian scrapyards alongside
their larger brethren. |
|
| |
I keep seeing this as "pedal powered explosion".
Perhaps some sort of Green terrorist device - a
rupturable air tank connected by high-pressure hose
to a highly-geared bicycle-driven compression. |
|
| |
Because the operater's heart would explode long before
liftoff. I think you've got your power:weight ratio
backwards (I can provide a whole slough of links backing
this
up if you really, really want me to). The
whole point of an Ekranoplan is to make a vehicle heavier
than an airplane but still capable of flight--sort
of. The Russians built them to carry huge anti-ship cruise
missiles too heavy to mount on aircraft. Later, after the
Cold War ended, they persisted in constructing massive
troop-carrier models that they thinly disguised as 'marine
rescue vehicles'. |
|
| |
So, it turns out that we're both right. <linkies> |
|
| |
The ekranoplans that I'm more familiar with, the Russian
military variety (Exhibit A) are great big honking
monstrousities built to carry heavy weapons and a whole
battalion of troops across water very fast, and at
288,800flb thrust : 386 tons (loaded weight) have double
the
power:weight
ratio than would an airplane of
similar dimensions (e.g. an Airbus 380; 280,600flb : 650
tons, also the loaded weight). The Lun-Class
ekranoplan is also a
waterborne vehicle and thus falls under your caveat, but at
double the pwr it far outstrips the take-off requirements of
a theoretical 'Airboat 380'. I feel that either argument is
valid from the comfort of our
armchairs. On the
other hand, much smaller ekranoplans such as the Bentley
Islander (Exhibit B) are rich man's toys made from very
lightweight materials and don't carry much payload, thus
they have a _lower_ pwr than a 4-6 seater airplane. The
ratio is so low, in fact, that I needn't bother with
comparison, so I haven't. |
|
| |
Disclaimer: all of my A380 specs came from Wicky-pedia. If
any
Halfbakers are Airbus designers in real life, complain to
them, not to me. |
|
| |
Interestingly, it appears that Bentley Yachts is offering a
scratch-
built version of the Lun-class. Discerning shoppers
might want to poke around the scrapyards of the Caspian
Sea before paying to have one spec-built. |
|
| |
<after pissing [jutta] off by piling on more links> There,
that's four. Satisfied yet? |
|
| |
Most human powered flights (especially the early ones) have achieved altitudes a small fraction of the wingspan, and were therefore surely experiencing significant WIG effects (although I've found no specific mention of this). So, probably kind of baked. |
|
| |
Okay, just to make sure the horse is really dead, I've
prepared an example of power requirements on land- vs.
water-based aircraft. Those without [The Alterother]'s
near-encyclopedic knowledge of WWII-era military
hardware may fact-check to their hearts' content. |
|
| |
Comparing the Lun-class ekranoplan to an imaginary
water-based
A380 is a bit tricky since the Lun was built decades ago and
the A380 was built, like, last week. To be more
unscientifically accurate, we must find two airplanes of
the same era, the same specs, and
the same general purpose, one a landlubber and the other
a seaplane. This is actually impossible, but I found a way
to make it work, by comparing one B-24 Liberator (land) to
two PBY Catalinas (water). All of my weight specs are
rounded to the nearest thousand because both aircraft
appeared in a dozen or more variants during the course of
their respective production runs. Here goes: |
|
| |
The B-24 weighs around 38,000 lbs empty, with a max
takeoff weight of 65,000 (71,000 with a long runway and a
good life-insurance policy). It is powered by four Pratt &
Whitney R-1830/65 turbocharged radials providing 1,200
hp
each. |
|
| |
The PBY weighs a little over 14,000 lbs empty, with a max
(land) takeoff weight of 35,000. Though max water-takeoff
weight specs are hard to pin down, there are many reports
of PBYs taking off from calm water weighing up to 37,000
lbs (overloaded with fuel and ordnance for long-range anti-
submarine patrols). The PBY has two R-1830/43s, identical
in
almost every respect to those of the B-24 save that the
'65s are built to operate at much higher altitudes. Both
engines produce the same hp at the PBY's max operational
altitude of 15,500 ft, so we're good there. |
|
| |
My imaginary 'Double-PBY', built to match the size,
performance, and most importantly number of engines of
the B-24 would not necessarily weigh twice as much as the
existing airplane, but I'll be generous. This puts the
Double-PBY at 28,000 lbs empty--5 tons lighter than the B-
24--and with roughly the same max takeoff weight if the
two are side-by-side on the runway. The Double-PBY
therefore has a power:weight ratio* at _least_ 22% greater
than the B-24
when empty, and practically the same pwr when taking
flight with a max load--only the PBY can do it from the
water, with no additional power requirements. |
|
| |
Make of that whatever you wish. |
|
| |
*Another disclaimer: all this time, we really should have
been using the term 'power-to-mass ratio', but I decided I'd
stick to what we started with to avoid mass confusion and
panic in the streets. |
|
| |
I suspect that lift-to-drag and structural factors are more important than power-to-weight, and both will somewhat favour a ground effect craft, with its shorter and more efficient wings. Also, as with the human powered flights mentioned above, I've come across descriptions of early aircraft being insufficiently powerful to get out of ground effect; Q.E.D.ish. |
|
| |
We're not aiming for speed here, so comparisons with the Russian ecranoplans may be misleading. |
|
| |
Speed is the only advantage an ekranoplan has over a
hovercraft or fanboat. What exactly are we aiming for? |
|
| |
Pedal-powered flight without heart rupture, I thought. |
|
| |
Ah, yes. I got a little lost back there. |
|
| |
I'm sorry, but I'm just not a big proponent of this idea. I
don't think a human being (or more than one, for that
matter) could produce enough raw power to get the thing
off the ground. Maybe a person could pedal hard enough
and long enough to sustain flight if it were already
airborne and moving at cruising speed. Maybe. And that's
pretty much moot if it never takes off in the first place.
You'd have to shoot it out of a launcher or strap
on some JATO bottles or something. |
|
| |
Look, a lot of GEVs are pretty inefficient. People seem to
have this impression that they're all fuel-savers, while only
a handful of them are. Most of them are military
prototypes that suck fuel
like it's free. It's one reason why their development has
lagged behind other types of aircraft, and why you don't
see more of them. The exceptions to this are either rich-
boy's toys built for novelty or ultralights
with tiny Rotax engines built to prove that an efficient
GEV can be built. |
|
| |
But you might as well try to build a pedal-powered
rhinoceros, for all that I think it will work. |
|
| |
I found something that may explain my efficiency gripe.
From the wiki on Ground Effect Vehicles: |
|
| |
"A ground effect craft may have better fuel efficiency than
an equivalent aircraft due to its lower lift-induced drag." |
|
| |
Note the word 'may'. I think this statement is based on the
postulations of a French inventor and aeronautical
engineer named Le Sueure (sp?). Back in the 1920s and -
30s, he
studied the 'ground effect' phenomenon and wrote quite a
bit of theory on how it could be put to use--but that
was it, just theories. Actual development went off in a
different direction than he'd envisioned, mostly because
the militaries of various countries got hold of the idea and
started hanging weapons on the things, making them
heavier, necessetating more power, which meant bigger
engines... you can see where that goes. So what we've
ended up with are a handful of contraptions that follow in
Le Sueure's footsteps and a whole bunch of gas-guzzling
military prototypes rotting in boneyards because we have
airplanes, helicopters, hovercraft, and, let's face it, blimps
that are more suited to various roles we've tried to pin on
the poor ol' GEV. |
|
| |
I've said it before and I'll say it again, no-one utilizes the max force a human can easily sustain.
NO-one I say! |
|
| |
Held rigidly within in a flexible body harness the human shape can exert far more power straightening to full extension from a foetal position and then pulling back from extended to that same crunch.
Energy could be stored in flywheels. [link] Forgive the spelling. |
|
| |
True, but much more energy could be stored allowing for a smoother acceleration. Also hollow flywheels using compressed air as ballast would allow for energy storage over and above the flywheels themselves when expended, while at the same time lessening the weight of the craft. |
|
| |
Smart idea. Apply it to something else, though. Until I see
a working prototype Pedalkranoplan (even a scaled-down,
unmanned
model powered by an equivalent-to-human-output plant),
I shall remain firmly unconvinced. |
|
| |
hmmmm, what if instead a device was built just to measure the force and sustainability of extension/crunch output compared to any conventional human-powered take-off unit now in use.
The compressed air flywheels could be factored in later. I still think that an average, even non-athletic schmo can produce enough energy to sustain flight, although it might mean storing some of that energy in advance is all. |
|
| |
As a well-known Halfbaker said to me recently: post it,
and they will bun. I know I will. |
|
| |
As for the sketch, I do get what you mean, and as an
added bonus, the flywheels in the center look like boobs at
first glance. Science and sophomoric comedy; ya gotta love
it. |
|
| |
// I still think that an average, even non-athletic schmo
can produce enough energy to sustain flight // |
|
| |
As I and others have alluded to, that's the easy part.
Relative to elapsed time, the
majority of an aircraft's total expended power is used in
takeoff and landing. |
|
| |
I've thought about those points quite a bit. Stored power prior to take-off would overcome the superhuman requirements for initial lift. Energy can then be stored again airborne while gliding or riding thermals to battle crosswinds and such for landings... |
|
| |
On a side note, did'j'ever get the almost overwhelming desire to build a time machine to go back and throttle every one of your past guidence councelors? |
|
| |
No. I think trying to counsel [The Alterother] was probably
punishment enough. |
|
| |
(marked-for-tagline) "I shall remain firmly unconvinced" |
|
| |
That makes me feel better somehow, you must be doing it wrong. |
|
| |
I was sort of hoping somebody would grab the one about
the rhinoceros, but who am I to dictate the whims of
others in regards to prospective taglines? |
|
| |
I'm [The Alterother], that's who. |
|
| |
// I shall remain firmly unconvinced.// normzone, |
|
| |
"There is nothing a German Officer cannot do!"
(Colonel Manfred Von Holstein.) |
|
| |
I love finding these ideas that I have scattered throughout the bakery! |
|
| |
So I was thinking of this, but with a few little additions/modifications. Firstly, I like the idea of electric assist bikes. Nothing huge, just something that spins the wheels to a decent bicycling speed. Secondly, maintaining flight at slow speeds needs bigger wings, but since I want to ride this on nice flat bike paths/trails this can't happen. So instead we increase the lift mechanically! |
|
| |
So let's start with the second part firstly. What do you know about the Magnus Effect? Basically, it means that a spinning sphere will redirect air perpendicular to the flow of the air. (see link). Now we are going to put a spinning cylinder on the front of the wing in order to both redirect airflow downward and to (slightly) accelerate airflow over wing. Mostly downward but excess will flow over. This provides additional lift which means slower air speed can get you off the ground. Now how to get up to speed and determine the airflow? Well if you've seen a Fletner Rotor you will notice that it has discs along the cylinder, this improves efficiency. Now what happens if you put a tire on that disc? Well now you have integrated landing gear and a single pedal point that gets the vehicle up to take off speed! |
|
| |
So now what about the electric assist part? For that we put a small bike motor (<750W) on the propeller that is near the stern of the vehicle with the wash closest to the rudder and elevators. This will also be attached to the spinning rotor to ensure that they fly "in balance". With the prop in front of the control surfaces you have better slow speed maneuvering (like a boat). |
|
| |
How will it all work? Get on a flat smooth surface, start pedaling and your front cylinder will rotate and gather speed and lift. When you approach lift off speed (which you will feel because the front will begin to lose grip and bounce) then you will kick in the electric assist which will boost your propeller speed above the pedal speed and up you go! |
|
| |
Still considered a bicycle, but not one that you will die riding. Well maybe you will still die as you will be literally flying down steep hills with no brakes and a spinning cylinder in front of you that is covered in road gripping rubber. |
|
| |
Lighter, stronger materials, an adaption of air flow dynamics for a lighter less powered dynamic.. hmmm. A strong tail, I mean, head wind. |
|
| |
Anyone seen that video of the cyclist that did that did a superman impression? (although, admittedly, he could have had one of those hidden motors) |
|
| |