The Steampunk Forum at Brass Goggles
October 22, 2017, 02:52:19 pm *
Welcome, Guest. Please login or register.
Did you miss your activation email?

Login with username, password and session length
News: Support BrassGoggles! Donate once or $3/mo.
 See details here.
 
   Home   Blog Help Rules Login Register  
Pages: 1 2 3 4 [5] 6   Go Down
  Print  
Author Topic: Airship Class  (Read 6485 times)
MWBailey
Rogue Ætherlord
*
United States United States


"This is the sort of thing no-one ever believes"

rtafStElmo
« Reply #100 on: August 12, 2015, 05:46:51 pm »

Those of us who understand such things (I realize I'm a hopeless noob, but I do understand a few things) may be able to read opinions and facts about inefficiency and efficiency, but the lay person on the street (or the student) who doesn't really think about such things all the time is usually, by this point, going W T EFFING F?! and deciding that his/her little R/C aircraft project can't fly, or that the science in his or her novel is just impossibly and ridiculously fantastical, and thus unpublishable (or inadmissable in class). It's winging over their heads (pun intended), is what I'm saying. So, I thought it might be good to interject just this one little point.
  
To everybody else:
People can caterwaul all day about how wonderfully "efficient" a prop or an airfoil is, but the simple fact of the matter is that there is still, even with those designs, a degree of inefficiency; if there weren't, it wouldn't be necessary to use knife-edge wings or jet or rocket engines (it's proven to be so) for surpersonic flight (just as an example); ifthat were not the case, you could just use Gooney Bird (1930s-40s C-47; a slow cargo 'plane) wing designs and turboprop configurations for it. It's just that the inefficiency inherent in knifedged wings and jet engines is outweighed by the greater efficiency inherent in those designs; by the same token, for supersonic fight, props and 30s-40s wings , like those of the gooney bird aircraft, have proven to be overwhelmingly inefficient.

Getting back to the paddlewheel and bellows fan bit, Despite the impression you might get from the short-form explanations you see on here (believe me, the long form is EXHAUSTIVELY long; as a person trained originally as a tech writer, I'm more or less used to poring over such things for grammar etc. if nothing else, but it's an acquired skill and taste), It's not actually "Is a giant blacksmith's bellows fan and necessary gearing and powerplant ridiculously inefficient," but rather "can a giant blacksmith's bellows fan and necessary gearing and powerplant (1.) be lifted by a properly- lofted airship envelope, and 2. can said fan, once lifted, be used to propel the airship through the air?"

The answering of that question/those questions is actually the point where "inefficiency" and "efficiency" come in; lay folks are not seeing that process much here, because we'd all be typing for seven hours straight every time we posted if we went through the theoretical and calculatory, and associated explanation, rigmarole every time we posted.

I realize that such thoughts are already running hardwired through our resident engineer's heads, it's just that people who are not engineers or do not have some association (past or present) with same, yet like to dabble so to speak, might become confused and disheartened by misunderstanding such a point. Experimentation, even if it's been done hundreds (millions?) of times before, is half the fun, after all, and actually serves a valid academic purpose.
« Last Edit: August 13, 2015, 05:12:21 am by MWBailey » Logged

Walk softly and carry a big banjo...

""quid statis aspicientes in infernum"
J. Wilhelm
╬ Admiral und Luftschiffengel ╬
Board Moderator
Immortal
**
United States United States


Sentisne fortunatum punkus? Veni. Diem meum comple


WWW
« Reply #101 on: August 12, 2015, 07:35:37 pm »

So, what you're saying that I went too deep into the subject, and thus took the fun out of the subject.  Cheesy

It happens to me all the time. But I don't want to underestimate the ability of lay people to research a subject on the Internet.  The flow of information is very different today, compared to just 25 or 30 years ago.  Sure that may lead to the irritating side effect of the homeless guy talking to himself about Quantum Mechanics, bit aside from that I see no damage in pushing the boundary just above peoples heads, and letting them swim to the surface to take a breath of fresh air.

This is the reason I'm hesitant to open an Aeronautical Club in the Meta section.  If people become overwhelmed, them it's going to be a lonely club...
Logged

Narsil
Immortal
**
United Kingdom United Kingdom



WWW
« Reply #102 on: August 12, 2015, 07:35:51 pm »

To address this it's important to define exactly what engineers mean by 'efficiency'. It's one of those words which is used a lot in common speech with a fairly vague meaning but has a very specific meaning in a technical context.

In general efficiency is the  amount of effort/energy that you put into a process compared to the amount of useful work that you get out, usually expressed as a ratio or percentage. In practice there are lots of different ways of measuring efficiency but they all come down to this ratio of energy out / energy in

As a simple example you might talk about how many tons of coal a steam engine consumes per hour to generate a certain horsepower, or in more modern terms miles per gallon for a car. Both of these are a bit crude and in technical analysis you would use more specific units of energy eg Joules, Watts etc but you get the picture.

Note also that efficiency is NOT the same thing as effectiveness. Effectiveness might consider any number of measure of performance of which efficiency may only be one and different aspects of performance will be given different priorities. So in some circumstances the most efficient solution may not be the most effective, depending on your priorities.

Having said that for any vehicle which has to carry fuel on board fuel efficiency will effect performance as fuel has mass so you need to expend power to carry it around, similarly all vehicles must consider the power to weight ratio of their engines.

For example the jet engines in civil airliners and military fighter aircraft work on pretty much the same principals but in general a civil aircraft engine will be more efficient in term of the thrust it produces per kg of fuel used whereas a military aircraft engine will have a much greater maximum thrust relative to its weight.

Similarly with car engines a 1.2 liter 4 cylinder engine will use less fuel per horsepower than a 5L V8 but the V8 will have much greater torque and maximum power and a better power to weight ratio (assuming similar levels of technological sophistication). Similarly a modern Formula 1 engine is only 1.6 L but will produce over 800 HP and better thermal efficiency than many road cars at the expense of having a life of only a few thousand miles and huge capital cost and spectacular  maintenance requirements.  At the other end of the scale is something like a Lister single cylinder stationary engine which will run as long as you keep feeding it something resembling fuel.

It also matters a great deal which parts of a given system you look at when calculating efficiency, an engine which is efficient in a small hatchback just won't work at all in a 16 wheel truck.

Something else to consider is that with a car there are relatively few losses associated with actually using the power developed by the engine (certainly at moderate speeds) rubber tyres on tarmac roads are pretty efficient at turning motive power into momentum, most of of the waste occurs in turning fuel into mechanical power and frequent accelerating and braking of the mass of the vehicle.

In aircraft the situation is somewhat different as you're pretty much stuck with having to generate thrust by accelerating the medium you are traveling through (ie air) and this is inherently inefficient as compressible gases are very good as soaking up energy.

Logged







A man of eighty has outlived probably three new schools of painting, two of architecture and poetry and a hundred in dress.
Lord Byron
J. Wilhelm
╬ Admiral und Luftschiffengel ╬
Board Moderator
Immortal
**
United States United States


Sentisne fortunatum punkus? Veni. Diem meum comple


WWW
« Reply #103 on: August 12, 2015, 08:28:27 pm »

Indeed.  I could go into a comparison between Rocket engines, turbojet engines, turbofan engines, propjet, turboprop, unducted fan,  propfan, and piston propeller engines (written in increasing order of efficiency, incidentally).  But I'll leave that discussion for an aeronautical club, as Mr. GCCC is encouraging me to open one, even if it's a bit of a monologue...
Logged
MWBailey
Rogue Ætherlord
*
United States United States


"This is the sort of thing no-one ever believes"

rtafStElmo
« Reply #104 on: August 13, 2015, 04:59:45 am »

So, what you're saying that I went too deep into the subject, and thus took the fun out of the subject.  Cheesy




Not for me, I love this stuff. But the average layperson, well, yeah I guess Grin
Logged
MWBailey
Rogue Ætherlord
*
United States United States


"This is the sort of thing no-one ever believes"

rtafStElmo
« Reply #105 on: August 13, 2015, 05:18:55 am »

Pardon the double post; I just now realized the horrendous error I failed to corredt earier.

It's "R/C aircraft project," not "A/C Aircraft project."

I know it's not really all that bad, it's just that I'm supposed to be proficient at editing, whether I'm a tech write ror a teacher.

*sigh*
Logged
Banfili
Zeppelin Captain
*****
Australia Australia



« Reply #106 on: August 13, 2015, 02:16:30 pm »

A use for the 'paddlewheels' on some of these airships may well be nothing to do with propulsion, but a lot do do with lift (in the mechanical sense) - the paddlewheel (or hamster wheel) type of construction was use for the manual lifting of heavy objects via ropes and pulleys, as seen in the building of castles and cathedrals. The wheels themselves may well be objects of punishment for irresponsible or insubordinate subordinates - "8 hours on the paddlewheel for you, Private. That will teach you to mind your manners to your betters!"
Logged
MWBailey
Rogue Ætherlord
*
United States United States


"This is the sort of thing no-one ever believes"

rtafStElmo
« Reply #107 on: August 13, 2015, 05:00:45 pm »

Or, perhaps human-powered engines to drive the props... Excellent suggestion, I hadn't thought of that!
Logged
Maets
Immortal
**
United States United States

Gravatar

Airship Builder


WWW
« Reply #108 on: August 13, 2015, 09:51:06 pm »

Checkout this website devoted to airships.  Not much there yet.  I posted a bunch.  Some older stuff up.  They are trying to promote it now, so here is my effort.

http://dirigible-modelers.lefora.com/
Logged

chironex
Snr. Officer
****
Australia Australia


The typing jellyfish monster


« Reply #109 on: August 15, 2015, 04:20:39 am »

Love the smell of helium in the morning...
http://www.urbanghostsmedia.com/2015/08/blimp-towed-water-skiing-extinct-sports/
It only failed to take off because Apocalypse Now made it cooler to do with rotorcraft.
Logged

Orkses is never beaten in battle. If we wins we wins and if we dies we dies fightin' so it don't count as beat. Even if we runs away it means we can always come back for anuvver go, see!

QUEENSLAND RAIL NOT FOR SALE!!!!!!
GCCC
Zeppelin Admiral
******
United States United States


« Reply #110 on: August 19, 2015, 04:28:54 am »

This seems apropos to some of the more recent discussion:


http://www.harkavagrant.com/index.php?id=231
Logged
GCCC
Zeppelin Admiral
******
United States United States


« Reply #111 on: August 19, 2015, 04:34:04 am »

Getting back to the subject of Airship classifications...


(Stolen Borrowed from polyphemus' post to the thread at: http://brassgoggles.co.uk/forum/index.php/topic,45979.0.html )

Intriguing design; what's this ship used for?
Logged
Burgess Shale
Officer
***
United States United States



« Reply #112 on: August 19, 2015, 04:42:56 pm »

A scudabout - a small, quick airship for quick jaunts from an untethered airship to the ground or another airship. Like a runabout boat, but named after the rapidly moving cloud.

I like that. Mind if we use it?

Please do. Smiley
« Last Edit: August 19, 2015, 04:59:19 pm by Burgess Shale » Logged

Dean of the Department of Palaeontology at the American Institute of Natural History and Decorative Arts
GCCC
Zeppelin Admiral
******
United States United States


« Reply #113 on: August 19, 2015, 05:15:52 pm »

A scudabout - a small, quick airship for quick jaunts from an untethered airship to the ground or another airship. Like a runabout boat, but named after the rapidly moving cloud.

I like that. Mind if we use it?

Please do. Smiley


Thanks!
Logged
Caledonian
Zeppelin Admiral
******
Netherlands Netherlands


the dragon's called Salmacis


« Reply #114 on: August 19, 2015, 06:27:08 pm »

I've been playing with the idea of training vessels. Small hot air balloons that hold two or three people and only have a simple engine to work with. This to help beginning pilots practice with being above the ground and operating in mid air.
Logged

"Crazy pseudo-scot living in a fantasy world"
Burgess Shale
Officer
***
United States United States



« Reply #115 on: August 19, 2015, 06:47:24 pm »

Another one could be the Luftstadt class for gigantic city-sized airships. This would require a buoyancy system other than gas bags or propellers, maybe spheres of nothingness to keep the whole thing up.
Logged
MWBailey
Rogue Ætherlord
*
United States United States


"This is the sort of thing no-one ever believes"

rtafStElmo
« Reply #116 on: August 19, 2015, 08:43:41 pm »

This seems apropos to some of the more recent discussion:


http://www.harkavagrant.com/index.php?id=231




ROFL
Logged
von Corax
Squire of the Lambda Calculus
Board Moderator
Immortal
**
Canada Canada

Prof. Darwin Prætorius von Corax


« Reply #117 on: August 20, 2015, 05:23:27 pm »

Here's a little grist for the fantasy mill, from yesterday's Hack A Day:

The EM Drive Might Not Work, but We Get Helicarriers If It Does
Logged

By the power of caffeine do I set my mind in motion
By the Beans of Life do my thoughts acquire speed
My hands acquire a shaking
The shaking becomes a warning
By the power of caffeine do I set my mind in motion
The Leverkusen Institute of Paleocybernetics is 5838 km from Reading
Maets
Immortal
**
United States United States

Gravatar

Airship Builder


WWW
« Reply #118 on: August 20, 2015, 05:50:15 pm »

The airship I am working on now has two nozzles I was calling rockets.  Maybe they are EM drives? Shocked
Logged
J. Wilhelm
╬ Admiral und Luftschiffengel ╬
Board Moderator
Immortal
**
United States United States


Sentisne fortunatum punkus? Veni. Diem meum comple


WWW
« Reply #119 on: August 20, 2015, 07:25:52 pm »

Here's a little grist for the fantasy mill, from yesterday's Hack A Day:

The EM Drive Might Not Work, but We Get Helicarriers If It Does


Since my training in engineering is all based in classical physics, including Electro Magnetic wave theory, which was well developed by the end of the 19th C, then every fibre of my being says this drive cannot work.  Explaining how the large end of the can has a larger force than the small end also sounds bogus at first glance, since I tend to think about force as pressure multiplied by area, acting perpendicular to the surface.

In this case the pressure is for the momentum of photons hitting the walls inside the can (electromagnetic waves <=> photons, duality of matter and energy)

In other words, the angled walls of the can also produce a force, albeit smaller, due to the angle That is why turbine and jet engines -while being basically a just a tube with combusting gases- can produce any thrust at all. The non-straight shape of the tube (and rotor blades) actually provides a "cross sectional area that can be "pushed" by the pressure to move the cylinder forward, yes?  Actually this is a PhD candidate's question for oral exams...  

There must be some axial component of the force acting in the direction of thrust.  How do these dudes make out to have a pressure differential? Not so, according to Isaac Newton and Einstein.

The explanation most likely lies in quantum mechanics, and the effect is basically a "microscopic universe" type of physics...  

So is this something best explained by wave functions? Which basically are probability distributions for finding a photon?  A probability drive?  An Improbability drive must be around the corner  Grin


If they can explain how it works it'd be awesome...  But 30kN per kilowatt?  Who said that?
« Last Edit: August 20, 2015, 07:38:32 pm by J. Wilhelm » Logged
GCCC
Zeppelin Admiral
******
United States United States


« Reply #120 on: August 20, 2015, 08:49:00 pm »

Regardless if it works or not, at least they had the decency to make it look vaguely Steampunk...



I'm guessing that's copper? Needs gauges and tubing, 'though, and one of those flywheel things...
Logged
Peter Brassbeard
Zeppelin Captain
*****
United States United States



« Reply #121 on: August 21, 2015, 04:34:35 pm »

Since my training in engineering is all based in classical physics, including Electro Magnetic wave theory, which was well developed by the end of the 19th C, then every fibre of my being says this drive cannot work.  Explaining how the large end of the can has a larger force than the small end also sounds bogus at first glance, since I tend to think about force as pressure multiplied by area, acting perpendicular to the surface.

I think we can say with confidence that if EM drive does work it topples at least one of conservation of energy or relativity theory.  And serious damage to our understanding of electromagnetism.
Logged
Banfili
Zeppelin Captain
*****
Australia Australia



« Reply #122 on: August 22, 2015, 03:45:09 am »

Do you know I'm starting to be even gladder than I was at the time (2010) when I did physics at uni - I am understanding this thread!  Grin
Logged
GCCC
Zeppelin Admiral
******
United States United States


« Reply #123 on: August 22, 2015, 05:26:18 am »


https://pbs.twimg.com/profile_images/2511431080/olzckk6xrgq9rauqn0qa.jpeg

Well, obviously this is the logo for their site, but if it were a functional aeroship...

Would the winds running across the strings make music? Or would there be a mechanical control, either like a player piano or an actual musician manipulating some sort of controller that translates their playing to the exterior strings?

What would you think this vessel is used for...?
Logged
Caledonian
Zeppelin Admiral
******
Netherlands Netherlands


the dragon's called Salmacis


« Reply #124 on: August 22, 2015, 08:06:12 am »


https://pbs.twimg.com/profile_images/2511431080/olzckk6xrgq9rauqn0qa.jpeg

Well, obviously this is the logo for their site, but if it were a functional aeroship...

Would the winds running across the strings make music? Or would there be a mechanical control, either like a player piano or an actual musician manipulating some sort of controller that translates their playing to the exterior strings?

What would you think this vessel is used for...?

Perhaps the same way as armies marching bands!
Logged
Pages: 1 2 3 4 [5] 6   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.20 | SMF © 2013, Simple Machines Valid XHTML 1.0! Valid CSS!
Page created in 0.336 seconds with 16 queries.