A different kind of v.t.o.l aircraft, is itworth a try?

[leviterande]

Hello everyone I am new here and sorry if I came very wrong but I just wanted to share with technical peoble about a design existed in my head and funny too I found it PATENTED too

what about a VTOL that uses say 40 small 20 inch props instead of one large prop/fan , instead of using 2 or 4 engines as in hariers and god knows how many vtols have been made, what will be a craft with 40 or 30 2-stroke 2kw engines for example be like..

every engine would have its prop , that would make a circular platform with very nicely distrubted thrust. I have RC experience in both airplanes and helicopters but not this kind

here is a patent: http://www.freepatentsonline.com/7159817.html

BTW here are the possible advantages of it:

---very safe: youhve got more then 30 engines , if one or 2 goes, ther is no
problem


---low inertia meaning you dont have that extreme rotor torque of a 12 meter
heli rotor

---pretyy easy to build

the possible disadvantages are

---pretty EXPENSIVE!!! unknown prototyp when you need at least 25 engines to test the concept


very unknown grounds here, it could be easy to handle to make it stable in hover somehow in the air or it could be a disaster to fly

---crazy noise from 30 angry propellers


I really wanted to try this out but wanted to know first if you had anything to point out

regars
Kalle









regards Kalle

[dareposte]

I suspect the most difficult problem you would struggle with is the power to weight ratio. As conventional motors get larger, they can generally output much higher power per pound. That's why it makes sense to have a couple of very powerful engines as opposed to many smaller engines.

If you could figure a way to power it from one or two larger engines with a lightweight power transmission of some sort, then you might be on your way to getting somewhere.

[leviterande]

actually that is nt the biggest problems as I have searched and found rc 2-stroke ones very light and powerful , they deliver about 2kw and wights less then 1 kilo, so i guess the are even more effective then larger ones.

No one ever has tried this at all! it would be pretty intersting to see it in action


kalle

[youngjim]

Controlling such a beast would be a challenge. Not impossible, but you would need to have some means of controlling thrust across all of these engines. Not to mention how would you start them? What about supplying fuel? Perhaps scale it to 4-6 engines, each turning several propellors? The vibrations from that many engines and propellors would be incredible, too.

It sounds like an interesting idea, but not a very practical means of getting from A to B. If you wanted many small propellors then one or two larger gas engines could be used to power generators, and use an electric motor for each engine. Then all you would have to do is synchronize all the motor controllers, and you could get pitch and roll control by adjusting the thrust. -Jim

[leviterande]

Youngjim, I am with you at teh point of the challenge to control aaaaaaaaaallll of these enginesm but that is actually the unqui thing about the concept, Off course i could use 5 engines controlling 30 props but i would loose the "independent control of each one" you might think why the hell do we need to controll them separetely, the reason is you get a very very flexiable platform that requires perhaps pretty slow reactions from a jystick or a little computer controller, if we use 4 engines and 30 props we really control 4 pieces of the craft meaning we would simply give it a four rotor configuration instead



talikng about electric concept, I really dont know what the inventor were thinking, if we use a very high end gas turbing generator and the brushless motors it would perfect, the big big problem is the weight of the alternator

one need say a 100hp alternator ,, it weights at least 300kg...

Kalle

[leviterande]

Controlling such a beast would be a challenge. Not impossible, but you would need to have some means of controlling thrust across all of these engines. Not to mention how would you start them? What about supplying fuel? Perhaps scale it to 4-6 engines, each turning several propellors? The vibrations from that many engines and propellors would be incredible, too.

It sounds like an interesting idea, but not a very practical means of getting from A to B. If you wanted many small propellors then one or two larger gas engines could be used to power generators, and use an electric motor for each engine. Then all you would have to do is synchronize all the motor controllers, and you could get pitch and roll control by adjusting the thrust. -Jim

you are right Jim, I even came to conclusion that using too many engines is hard .. so my plan is to use 4 -8 engines.. but what you said about using electric motors is intersting.. but are you aware of the weight problem of using an engine plus generator..the lightweight gasolinng enigne is not a problem but an alternator will weight 200kg only to suply 55 hp of electricity!! so how does it come everybody is talking about using electric motors with a generator,, in fact a generator system will be very heavy:
a gasoline engine+ alternator+ fuel+ electric motors

the brushless alternators are very heavy as I mentioned at around 200kg for getting 60hp.. so if you add the gas engine, you have 270+ 20 of fuel--- yeah almost 300kg of "power source" of 60hp --

or.. could there be a very light weight alternator?

Kalle

[dareposte]

actually that is nt the biggest problems as I have searched and found rc 2-stroke ones very light and powerful , they deliver about 2kw and wights less then 1 kilo, so i guess the are even more effective then larger ones.

No one ever has tried this at all! it would be pretty intersting to see it in action
kalle

The RC motors you're talking about probably run on "nitro", or nitromethane. They manage to put out good power for their weight mostly because nitro has a lot of oxygen in it so the motor doesn't need to burn as much atmospheric oxygen, and can run faster and leaner. The down side is that for a given power output, that type of motor has to carry about 4x more fuel than a conventional gasoline motor. Also the fuel is more flammable and dangerous than regular gasoline, as it doesn't need much oxygen to burn.

It would be interesting to try as a demonstration or experiment, but for any meaningful flight under load the weight of the fuel required would quickly overcome the weight of the craft. Even with the 4x improved power density of gasoline, it makes up a substantial portion of an modern aircraft's takeoff weight.

[leviterande]

The RC motors you're talking about probably run on "nitro", or nitromethane. They manage to put out good power for their weight mostly because nitro has a lot of oxygen in it so the motor doesn't need to burn as much atmospheric oxygen, and can run faster and leaner. The down side is that for a given power output, that type of motor has to carry about 4x more fuel than a conventional gasoline motor. Also the fuel is more flammable and dangerous than regular gasoline, as it doesn't need much oxygen to burn.

It would be interesting to try as a demonstration or experiment, but for any meaningful flight under load the weight of the fuel required would quickly overcome the weight of the craft. Even with the 4x improved power density of gasoline, it makes up a substantial portion of an modern aircraft's takeoff weight.

thank you for your interest but actually the motors I am talking about run on ordinary gasoline

I can choos from 10hp 163cc or 19 hp 219cc engines

but I first dont know if it is better to stick with one whole big engine like a rotax 582 or 618 or 912 that give 65-100hp

the problemtaics with having a single big engines is that they have power power to weight ratio as opposed to smalle twin engines

example:


rotax 582, 65 hp, 50 kg installed weight with carbs exhaust, mufflers

Sv 210cc twin cylinder engine 19hp, 6 kg installed weight

another big problem is that larger engines need alot more work to install on a craft. strong mountings, shock absorbers.. fluids, etc

sv210cc engine.. the thrust the guy I asked said was 58-60kg!!
http://www.alibaba.com/product-gs/20..._Airplane.html

Kalle

Kalle

[neilw20]

Fuel injected (electronically) diesels.
They are fairly easy to control in this manner with a light weight control system being electronic.
You get a lot of bang for your buck with diesels.
The necessary starter motors are a weight penalty.
As propellers get larger they become more efficient. The inner 1/4 of the disk is fairly useless. If tip speed of prop is much greater than mach 0.8 lots of power is wasted, so we need wide chord ducted fans to use the power with reasonable efficiency. Existing air conditioner fans are well developed and each fan can be fine tuned with the adjustable pitch. All the same settings I think.
Make the whole lot tiltable, maybe a few with gimbals.
It would be nice to travel some distance and not just up.
Now you just need a fair bit of money.
Interesting forced landing un powered procedure is a worry.
I suppose just a parachute or two.
If you land in long grass it will be a b1tch to clean.

Been there, done some development. Before I was as heavy as I am now I built and flew a 75KG (empty) ultralight in 1977. Tail-dragger 9m span, with a plastic kitchen chair minus legs, and golf buggy wheels. There were not many around then. It initially flew on 6HP motor mower engine, but the crankshaft after 1 hour. Finally settled on 18HP Sachs Wankel.
More fun to fly than a real airplane. Still have it stored away.
Online archives didn't exist back then. I must dig out he center page spread in our broadsheet. It is a bit yellow now, and in the drawer behind the CNC.

[leviterande]

you are right there, the tips speed shouldnt actually be over 0,7 mach

and since you have more expreience in testing motors.. is it true that the enigne I specified "210cc" twin could pull 60kg of staic thrust? direct drive?


Kalle

[martinw]

Dear leviterande,

This guy seems to have come up with a solution to the engine starting problem...LOL.



Best wishes,

Martin

[dareposte]

thank you for your interest but actually the motors I am talking about run on ordinary gasoline

I can choos from 10hp 163cc or 19 hp 219cc engines

but I first dont know if it is better to stick with one whole big engine like a rotax 582 or 618 or 912 that give 65-100hp

the problemtaics with having a single big engines is that they have power power to weight ratio as opposed to smalle twin engines

example:


rotax 582, 65 hp, 50 kg installed weight with carbs exhaust, mufflers

Sv 210cc twin cylinder engine 19hp, 6 kg installed weight

another big problem is that larger engines need alot more work to install on a craft. strong mountings, shock absorbers.. fluids, etc

sv210cc engine.. the thrust the guy I asked said was 58-60kg!!
http://www.alibaba.com/product-gs/20..._Airplane.html

Kalle

Kalle

Wow those are some nice powerplants you're looking at. I didn't realize they were so compact! I say you build one and give it a try