[diarmaid]

Hi will. The idea I ended up with was also an adaptation of the Springtail (Solotrek) which I believed would be not only cheaper and more simple to produce, but also have various other advantages. I could'nt find any site to buy a ducted fan over a few inches in diameter unfortunately but if I do I'll let you know. I deleted the text from a large number of my previous posts so you were probably unaware of the route I decided to go down which may have been similar to your own. Im sure you've seen this but here's the current Solotrek (Now called Springtail) site. http://www.trekaero.com/

[Geof]

diarmaid maybe you should be talking to these people:

Skyflyer Technology GmbH ("Skyflyer"). Skyflyer is a company based in Wegberg, Germany engaged in the development and commercialization of a one-person recreational flying device.

[diarmaid]

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'!

[Geof]

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.

[diarmaid]

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!! :stickpoke: Does look like a nice design if someone who ain't a corrupt fraudster decided to design and build it.

[diarmaid]

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.

[diarmaid]

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).

[diarmaid]

Posted this blank post by accident.

[willw00ds]

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

[diarmaid]

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

[diarmaid]

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.

[spider]

http://www.newlaunches.com/archives/...helicopter.php

[thkoutsidthebox]

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.

[RakmUp]

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.

[thkoutsidthebox]

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!

[RakmUp]

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

[thkoutsidthebox]

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.

[RakmUp]

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

[cbass]

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

[fyffe555]

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