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  1. #81
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    Quote Originally Posted by diarmaid View Post
    Thanks for the info Geof. A four fan adaptation of the aerotrek crossed my mind to allow 2 or 4 person capacity. It looks like an interesting and kinda unique design, although maybe a bit slow. But hey!...if it works...more power to 'em.

    Here's the site if anyone's interested:
    http://www.skyflyertec.de/en/the-idea/

    Referance post 72, I don't give up that easy....I still have an idea in the works that unfortunately has to stay very 'hush hush'!
    Maybe you will be interested to find out how I came across skyflyer. The business pages of The Vancouver Sun has a reporter who specializes in uncovering stock market frauds and scams; Skyflyer Technology GmbH is featured in one of his articles.



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    Quote Originally Posted by Geof View Post
    Maybe you will be interested to find out how I came across skyflyer. The business pages of The Vancouver Sun has a reporter who specializes in uncovering stock market frauds and scams; Skyflyer Technology GmbH is featured in one of his articles.
    LOL. You got me! Maybe next you can find a similar article about Steorn!! : Does look like a nice design if someone who ain't a corrupt fraudster decided to design and build it.



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    Hi all.

    In case anyone is interested I was in contact with Joe at Zinger Propeller and he is able to provide both tractor and pusher props in 3 and 4 bladed.
    But Im not working on this anymore.

    L8rs.

    Last edited by diarmaid; 10-01-2006 at 05:49 PM.


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    Also although Im not working on this anymore I coincidentally came across an engine quite inexpensive and putting out enough hp for a scale proof of concept prototype (I think).



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    Posted this blank post by accident.

    Last edited by diarmaid; 10-02-2006 at 10:38 AM.


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    hey diarmaid thanks for the info. i e-mailed pwerfon props to get some more info about thier carbon fiber thrust fans. Check em out at http://www.powerfinprops.com/
    -will



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    Thats great will. You seem to be a lot further along than I was. If you dont mind me asking, did you build a scale prototype of your design before moving onto looking at full size?

    That powerfin site is great but I went looking at engines after seeing it and found the site below. If your looking for a 5 bladed prop from 36" upwards these Kievprops seem to be even better.

    Pity there's no prices for the engines on the site. There's a mathematical calculation I have somewhere for calculating required horsepower for a given prop diameter, weight, air drag coefficient, and speed required, which can be used to calculate necessary engine power. But I can't find it in my mountain of paper so I asked an aircraft technician I know and he's going to get it for me this week. If your interested I'll post it up.

    http://www.oregonaircraftdesign.com/props.html

    The above mentioned (Post 84) inexpensive scale engine. GMS 120. 3.3hp at just under max rpm.
    http://www.mecoa.com/gms/index.htm

    Last edited by diarmaid; 10-02-2006 at 11:01 AM.


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    Im after finding a nice compact 2 stroke model aircraft engine that puts out 32Hp and only weighs 7.3kg. That would be 64Hp for two if I was still working on this. Now just have to get those calculations to figure out how much weight 64Hp with a given prop would lift.



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    The relevant calculation requires you to know the thrust co-efficient for the particular prop which can be got from the manufacturer, or by testing yourself.

    For anyone who wants to know its:

    Ct = T / r x s x d

    Where:
    Ct = Thrust Co-efficient
    T = thrust in Newtons
    r = rho = density of air
    s = prop revs per second
    d = diameter of prop

    There are a few other formulas also.



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    Default VTOL Dream

    Hi Guys, forgive my novice ( I have "0" aeronautical knowledge) involvement to propose an idea I have had ever since I saw a Motorcycle with hub-less wheels. I used to follow the Moler projects.

    Counter Rotating fan rotors driven by 1 (or 2 for safety) engines in the middle of the fans. Fans mounted in hub-less wheel brackets. Air ducts that are adjustable to control direction and speed forward or backwards. A Parachute in the nose cone for emergency.

    Seems to me to be a pretty stable design but not very fast. I am sure you could adjust air flow and tilt to help if the overall design is feasible.

    Just looking for feedback on the possibilities of this design.

    Again, thanks for indulging my idle mind.

    Chuck

    ps: don't beat me up too bad for the wrong direction blades, just think reverse.

    Attached Thumbnails Attached Thumbnails Personal Air Vehicle?-vtol-dream-jpg   Personal Air Vehicle?-vtol-dream-top-jpg  


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    Cool design.

    The only possible problem I see is that the internal and external blades have a vastly different surface area from what I can see, so the internal ones will have to rotate faster, the external ones slower, or else enlarge the inner ones outwards until their diameter allows a total surface area equal to the outer blades. Also I didnt count all the blades, but are there an equal number internally and externally?

    Im not sure how much of a difference it would make, because the physics of this are soooo complicated and beyond me, but there is a much larger air gap between the blades of the outer fan, than the blades of the inner fan. This may affect the overall lift properties.

    Another consideration is that the inner and outer fans will be sucking air inwards using opposite vortices above them (Because they are contra-rotating) and I think that this also may have an effect because of the layout (Different to that of two equal diameter contra rotating props directly above/below each other), its a blind stab in the dark here, but I think this will increase the airflow into the inner fan, and suck air away from the outer.

    It looks basically like a current helicopter, except using ducted fans instead of blades, thus removing the need for a tail prop, like a heli with contra rotating blades. Im not up enough on the physics of ducted fan - vs - blades efficency ratios, so maybe the fan would be efficient enough to significantly reduce the diameter, but if not, then your outer fan diameter looks a bit small to generate enough lift for such a bulky body, especially considering that the entire 'disc' surface is not available to be used, only the parts outside your nose cone.

    The nose cone looks very large, Im not sure it'd need to be so large to fit a parachute, although Im not sure how big small aircraft emergency chutes are.

    Also, from my unrelated interest in wind turbines, wind turbine studies have shown that the nose cone actually decreases the efficiency of the turbine blades. This may be different as the air speed increases substantially as with an aircraft, but its worth considering when thinking about how small you can get the cone.

    Just some thoughts. Please keep us informed on how your going.

    Edit: Also, from what I see in the pics, are your engines side mounted? If so then your looking at quite a complicated drive system to transfer the drive through a minimum of two axis changes.

    However.....it does look really cosy in there!



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    Thanks for the reply...
    I just drew this up in the hour before posting after I found this cool thread.
    I know there are a ton of things that would have to be configured differently than I have drawn. There is absolutely "0" engineering on this drawing.
    As I was drawing this I saw too that the outer and inner blades would have to be balanced somehow, whether through air flow or mass or some other higher level of thinking than I am aware of. I am not sure if they have to be balanced in numbers of blades though....all the blades would give some lift, and some more than others. I think the main thing would be to balance for rotational stability. Good point about the in-coming air turbulence.....I'll leave that to the higher powers.
    As far as a fan goes, if you look at leaf blowers and such, there is tremendous force coming from small diameter blades and when you have many more blades than typical low numbers on helicopters I am thinking it is feasible...again no engineering to back me up...just a gut feeling.
    The nose cone is an easy fix also if not needed and I guess the intent of this vehicle is not to take off fast like a rocket and therefore the shape could be anything that the chute would pack and deploy from efficiently.
    Actually, my engines are vertically mounted...never thought that it may not work that way. I have seen snide remarks to the rotary engine (Wankels) but that is what I would consider for this application. The drive shaft coming basically straight out the front of the engine (maybe through a gear box).
    Unfortunately, I am only a concept kind of guy in this realm and will never proceed any further than wishful thinking. I have wanted to share the idea with someone else who actually may be able to make it work or at least give it a credible thought. That is where this thread came in to my view. All of you who have posted here seem to be in to this sort of thing and seem very knowledgeable. I really believe someday we will be flying around in personal aircraft and would love for it to be in my lifetime.
    I am on CNC-Zone for a CNC Router I am building....not aeronautics.
    That is why I apologized for stepping in here initially. I know this is a bit off topic for the group and thread beginning. I sure don't want to offend anyone in here or waste their time with my drivel.

    ps: great nickname......

    Later,
    Chuck



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    Thanks re the nickname!

    There's no interfering in any threads, its an open site for all to participate. I do like the idea though and might look into it a bit more. The major problem with this idea from a DIT experimental point of view is the use of ducted fans. Although they're great they would have to be custom made using equipment generally outside the posession of you average home experimenter. failing that they would have to be custom built at huge expense, without knowing if they'd even work. Its not easy to just buy ducted fans like it is props.

    The wankle rotary seems to be the standard engine looked at for PAV systems at the moment. Light and powerful. But its operational hours are relatively small compared to a standard vertical piston engine. The drive axis will have to be altered regardless of the engine type with the layout above I think. Far from impossible, but still quite complicated to build the necessary parts yourself.

    L8rs.



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    Can these types of projects just be drawn up in some software to determine all of the potential problems like to incoming air vortexes and the rotational balance? I must be too assuming and believing with today's technology there is an Autocad plugin that could tell you based on your computer model the suitability and conflicts on a project like this.

    I also feel like it would not be too complicated to make a model version of this design for testing as a DIY'er. I used to be a machinist though and still have many people I could pull help from on making the required parts. One guy made a lawn vacuum with a ducted fan that sucks up 1.5" diam sticks and chews them up in the same process. Almost too much vacuum! And it was all homemade.

    Dang....you got me all tied up on this stuff again....I have other projects to get done......thanks alot!

    later



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    Quote Originally Posted by RakmUp View Post
    Can these types of projects just be drawn up in some software to determine all of the potential problems like to incoming air vortexes and the rotational balance?

    I know many programs that have FEA (finite element analysis) plugins. They can test stress in structures based on loads. Solidworks' plugin for this is called cosmoworks.

    Not sure about your specific application, as there are so many variables. Perhaps something created for the RC airplane hobby industry ?

    Carlo



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    interesting idea, a couple of thoughts;

    There is no plugin for autocad etc to do aero vehicle dynamics as a whole. You can get fea for mechanical, some programs for thermo and some fluid dynamics. Each program is more than several autocad full licences. The end result still wouldn't give the answer you're looking for. They do not generally contribute to one answer or even agree. Thats why wind tunnels are still required.

    Hubless wheel bearings carry the load in a different plane to the concentric ducted fan design.

    The hubless bearing generally is engineered for a relatively slow speed. Each fan would have to rotate much faster than a road wheel and you are componding the bearing speed since the two fans rotate in the opposite directions, doubling the effective working speed requirement for the bearing.

    Are the two fans supposed to pass the same volume of air per unit time? A rough rule of thumb says the same amount of work (power) will move the same given volume of air what ever the speed and size of stream. If the concentric idea is to balance the torque produced by the fan disks then the inner disk will have to turn at a function of the ratio of the areas. If the inner is a 1/4 area its got to turn four times the speed. This will produce serous turbulent flow as the centre stream will be required to flow far faster than the outer stream. You've got boundary effects on the outsides of both fans.

    Powering the rotors seperately would be interesting.

    As thkoutsidthebox says, fairings or spinners do not help below certain airspeeds and at very low airspeeds are actually a hinderance.

    How about concentric fans or prop blades like a helicopter, mounted on one common shaft system.

    Any thoughts on controlling it?

    Again, interesting, fun idea....

    Andrew

    Last edited by fyffe555; 12-02-2006 at 04:40 PM. Reason: can't spell....


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    ....ok....
    1. you engineering guys develop:
    ____a. air volume/speed requirements to lift ~500lbs.(allow for some safety measure)
    ____b. divide that by 2 rings (inner smaller diam. and outer larger diam.) giving equal flow at same rpm.
    ____c. determine rpm of blades (based on available engine technology)
    ____d. size, shape and qty. of blades based on "a." & "c."
    ____e. determine adequate bearing configuration for fan rims.
    ____f. size of parachute to bring 500 lbs down safely in the probable emergency,(folded package size)
    ____g. what to drink when we achieve goal

    2. No computer help so we need to build a scale model.
    ____a. What scale?
    ____b. Material?
    ____c. what to drink when it flies?

    Seriously....
    Thanks guys for entertaining my idea.
    Good point Carlo, there may be something already out there in the model industry that could help get things rolling.
    Andrew, my point on the hubless wheels was just that you don't need to think center-minded anymore. The outer fan could be supported by some OD/ID bearings of some sort or another....not necessarily like a motorcycle wheel.
    Each fan would be in their own bearing structure, I don't see where the compounding comes in.
    I would suspect each fan would blow much different volumes of air at the same RPM. It could be the same but you are correct, the goal to me would be to balance torque. I do not know how else to stop the rotation unless you use a tail and rotor to keep you straight. And the outer fan could be much narrower if that results in a better match for the balance. Then I would just extend the motors out from the body to the centers between each fan.
    The reason I was thinking each engine would both drive was for safety that possibly 1 engine could bring you down safely....nothing more. So if it makes sense to drive each fan a various different RPM's then I would hope that either remaining fan could also bring you down slower than a rock and still avoid using the chute.
    Control in my plan comes from the ducts that lead from the top of the body(under fan) to the 4 corners at the base of the body....normally open air flows and gives some lift...close any 1 partially and you would begin to rotate..close all in back and go in reverse, close all in front and you go forward. Like I suggested earlier, it would not be a fast ride unless you could build in some kind of tilt to get the fans pulling you in a direction as well. The purpose for this would not in my mind be for cross country flight but possibly commuting 20-30 miles relatively quickly as the crow flies.
    I was just trying to stay away from props as they have been done probably to death and they still don't fly much in this type application....they are not common. Concentric Fans?
    Please remember I have no real idea of what I suggest....just thinking outside the box. ;-)

    Thanks again...Later....

    Chuck



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    Generally the scale of model to build is 'the larger the better'! Smaller models give completely different aerodynamic characteristics to their full size brethren. I'd be thinking definately no less than 1/3 size, depending upon the size of the full scale vehicle. remember that some large rc models are what we can consider huge for models, so for something like this it may be worth thinking about your 'model' being a full size version, just with rc controls.

    Of course building full size and full weight increases the costs exponentially since you can no longer buy r/c aircraft parts for testing and you have to go to regular aircraft manufacturers and engine manufacturers. Its basically a trade off between as big as you can afford while trying not to be too small. If you have a multi million developmental budget then of course the sky's the limit....so to speak!

    Im working on a design of my own at the moment, I have been since last May. I have a two year design program drawn up. Sorry I can't post pics for a bit, but will at a later date. I've gone through a number of design changes and sourced most of the parts. Im tooling up at the moment and starting to build the initial proof of concept prototype at the beginning of February all going well. I've sourced most parts for both a scale prototype and a full scale version, but the full scale version was running at over 6 times the cost to build a prototype, and that's not including staying in line with any regulatory considerations. The scale I decided upon in the end is 1/2 scale, which allows me to remain within a reasonable budget for the initial prototype by using model aircraft parts (Approx €1000).

    As intimated to above, you can't get a program to just calculate everything, at least not without getting it specifically made for you. If you can I'd be extreamly surprised, please let me know! The factors involved are phenomenal, your talking about the movement of multi-billions of air molecules, with huge variables ranging from the altitude and humidity to the exact shape, size and distances from your fans that your vehicle is. Supercomputer multi million dollar government physics lab kind of stuff. Unfortunately.

    There are hobby type programs out there, some are free online or VERY cheap and used for analysing aerofoil data. However, the accuracy of the data is questionable, but can be useful for getting a general idea, in fact, Im using one myself! But I havent seen anything for calculating the thrust from ducted fans like you need to. In fact, I havent even found one for props, and have to do all the calculations myself the old fashioned way...great fun! ...

    Two engines for safety is great, but if you have a working parachute system then its not really necessary. However, two engines can be advantageous because you may be able to get the same power out of a smaller weight using two smaller engines which are lighter than one bigger one.

    How about moving your ducts to the base of your vehicle, two front and two rear. And have their output adjustable like you said, or possible having fully adjustable pitch outlets also. Anyway, when you direct some thrust solely out of the rear vents, because the vents are at the base and rear, the rear base will lift and the front base will drop, the aircraft will tilt forwards, allowing the main fans to then provide forward motion also. But remember when the main fans provide some forward motion also, that said force is being taken from the thrust providing lift and the thrust will have to increase. Theres more to this again, such as the operation of the ducts, the thrust out of the ducts, the operation of the front & rear ducts in concert etc but its an idea.

    The reason that props "have been done" is because they are very efficient for moving large volumes of air at slow speeds. Unlike for example, jet engines, which move small volumes at high speed. Dont dismiss props as being old. I know ducted fans have that cool factor, but take a step back to think that maybe props would be a possible alternative. They might look less new and improved, but they may also be a better choice. I considered both in detail and decided upon props, but again, lots of money could change this to fans if you have it!

    Im not that up on the intimate details of ducted fans, but I believe that your rims in the pic above would be unsuitable as the shrouds on ducted fans have to go slightly above and below to trap the air, so the shrouds need a flat (Or matching the blade edge) verticle surface inside. Ducted fans also have very tight tolerances between the edge of the fan blades and the shroud which have to be engineered very closely. They are not common because of the expense in making them, and they have their own considerations. Although with modern techniques and materials their time is probably coming. Again, I can't be sure because I dont know the characteristic comparisons between fans vs props. That would be interesting to see, any idea anyone?

    Also Im thinking '6 bladed prop' instead of 'ducted fan'. A 6 bladed prop is 6 times more efficient than a single blade (Very rare but they do exist), twice as efficient as a 3 blade etc. By efficient I mean that it literally provides 6 times the thrust of a single blade.

    Finally ....I firmly believe that the reason personal air transport has not developed faster is because the aviation industry worldwide has become SO INCREDIBLY OVER-REGULATED. Seriously, its crazy. Its well regulated for current technology in use, but regarding the development of a completely new aircraft, the amount of red tape and paperwork basically makes it impossible for an individual to fly something they designed and built themselves. Look at how difficult and expensive it is to just buy a small aircraft kit and get it registered to fly. With something like this you basically will end up with some aviation authority bozo who knows cessnas and 747's coming out at every stage of the construction process to see if your new aircraft, which he knows nothing about, is going to be safe to fly. Also, to actually sell and use something like a personal air vehicle, your talking huge legislative changes, because obviously every person who buys one of these can't go through the current Private Pilot training and testing and certification. This is not so bad in the good ole US of A, because you have different airspace classes, and if Im not mistaken, this could be flown by anyone, to and from work or whatever, in ClassD airspace. But in Europe we dont have seperate airspace classes like that, and its a headache to even think about.

    So, the point is that you should build a prototype as a model whatever size (I joined the local Model Aeronautical Society! ), then build the full size as a model and see if you can find investors or whatever. If I eventually get to a full size version Im going to just build it and fly it away from crowded area to see how it goes without telling anyone. If they get a radar blip at ATC I dont care because Ireland doesn't have any F16's to scramble to investigate.

    L8rs.



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    Ok.....I guess you have convinced me to go back to work on my little router. When you start talking governmental bureaucracy I'm outta here. Last thing I need is more stress in my life.
    I really do appreciate the information you have so graciously shared. I hope it didn't keep you up too late. That was a huge post! Somebody will benefit from it, I am sure.
    I wish you well in your project and good luck with your test flight. I'll watch this post from time to time to see if anyone is keeping it going but I don't think it will be me.

    Best wishes,

    Chuck

    maybe after I get my router going........cnc propeller/fan blades........hmmmm...



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