Motor bicycling taken to a higher level

[HeadSmess]

yep, the big tilt rotor type. its not the only one.

still suffer the same problems as every other VTOL...a lot of power required for it! vtol, is, as any pilot will tell you, extremely dangerous, especially if youre in a confined space. air starts doing a big vortex around the blades, and uh oh...no lift. kick up the collective, air flows faster, until the blades stall... then weeeee! down you go! uncontrollably. smack, bang, splat. those blades do a lot of damage when they hit things! argggh! black hawk DOWN black hawk DOWN!!!!!

and just like a helicopter...they use a lot less fuel when taking off from a runway in the usual speed up then pull back on the stick...



now a catapult, like on a carrier....oh yeah baby! launched! hope the afterburners are working and you got full power as you go over the edge!

it was off an aircraft carrier that they first discovered, by accident, that the ejection seat worked under water. LT. Macfarlane, 1954, in a wyvern. throttles died on him as he got flicked off...

a lot luckier than one of the earlier test pilots, P J Page, who was fired out at 400MPH from a meteor in '47... well, he survived... with a broken neck, legs smashed up, etc etc etc... he had to go down with the seat, as he couldnt run the risk of freeing himself, and having his personal chute tangle up.



and lastly, id rather be in a helicopter when it loses engine power than any other type of VTOL. autorotation. you can still land quite smoothly with no engine in one!

the v-22...what happens if all power is lost while the rotors are vertical? you cant even glide then... how do you tilt the wings back?


(same way actually, they have collective pitch control, so ok...if the blades are halfway between the two positions and you lose power...)

 

[Fabian]

ever hear of the V-22?

The V-22 is an awesome piece of engineering. Shame about it's unreliability issues, and the fact that it can't autorotate, and the fact that if the the drive shafts suffer mechanical failure, you are pretty much dead, and the fact that it costs over $100 million per aircraft and the fact that it killed a heck of a lot of people in testing and the fact that it is a horrendously expensive aircraft to maintain.

Those small things aside, the V-22 is an awesome piece of engineering with great capability.

but

It's been done before at a fraction of the cost; quite possibly with greater reliability and service intervals and increased payload if scaling up the design.

 

[HeadSmess]

i thought of this when i was eight years old....

http://jlnlabs.online.fr/gfsuav/index.htm

unfortunately it was patented a long time before i was even born, so... cant even claim simultaneous creation


but the freaking thing works! and note exactly where the propwash goes. it is NOT lifting directly from "thrust".

 

[Fabian]

Crikey, that is a terrific post HeadSmess. I love Formula 1 for the aero side of things as well as the many other innovative systems on the cars; Coanda exhausts being one sneaky trick to get around reduction regulations.

Even though the Coanda effect is put to good use, it's interesting to note that he uses vortex generators to assist flow attachment over the control surfaces.


This video is a great representation of non axial airflow creating lift through the Coanda effect:


:

 

[HeadSmess]

well im 31 and it took me that long to get round to making this...




i was drunk it became a keyring.

but yeah...i always pictured high speed compressor type turbine, storing in a torus. let the air escape through the thinnest slot possible over the large disc, but with two contra-rotating turbines... converging airstreams creating thrust in one direction... all nicely shaped for maximum aerodynamics and so forth. use the fact that the air will be spinning.



iunno. all i ever really did was make some nozzle for the aircompressor that will lift a kilo or so...but thats bernouli...

might do it one day ha ha.

 

[Fabian]

HeadSmess, maybe you should have a quiet chat to Adrian Newey. I am sure he would be all ears!!!

 

[HeadSmess]

i came to the conclusion, about 10 years ago, that coanda effect isnt that great.

why?

my nozzle for the compressor...it can lift simply because the "jet" is in the centre of a 6 inch disc.

high speed air, low pressure. you create a very thin layer of high speed air, that then "sucks" whatever is being lifted to the flat surface, despite having air escaping from that nozzle at 100psi. (whatever airspeed that is on a 1.2mm nozzle, someone else can do the maths and figure out). its a proximity thing. more than an inch or so clearance and the airjet simply pushes anything away.


same deal as trying to lift paper off a desk by blowing under it... just keeps sucking itself down.

hang on...just like a carby throat and jet!

anyway. coanda effect...high speed fluids will stick to a surface. i learnt that lesson all too often while brazing...get the torch the wrong way on a piece of steel and the flame would cling to it and come back, hit you in the face or hand or something... as akin to plain simple blowback, the coanda effect was a curiousity. took a long time before i found out what it was called. yep, science teachers sure know a lot... ha ha. half have never seen it before, half dont care... strange, tis what happens with a decanting rod...

but... theory says its moving fast, so it should be low pressure?

exactly correct, and exactly WHY it clings to the surface.

the atmosphere pushes DOWN on that low pressure layer of air. if it was upside down it would push up. etc etc.

the atmosphere plays the same role as the disc with my aircompressor nozzle.

the atmosphere, unlike my disc, is not solid and inflexible, but simply keeps moving in relationship to whatever surface this high speed layer of air clings too.

therefore the atmosphere will push down on the "coanda film" for want of a better name. therefore...no lift. once again, any old shape section of wing will FLY, with the correct angle of attack, the ideal shape is just, well...ideal... but it has to move through the air. as do heli blades, gyro blades, etc...

coanda does have some effect, reduces the amount of thrust required... but wont ever achieve complete unassisted (downthrust of propwash) lift. as i always liked to think, just lower the air pressure more than normally so across an airfoil? and the thing will produce more lift?

nope. doesnt work air pushes down on the layer with as much force as it pushes up on the underside.

thats the conclusion i came to.

laminar flow and turbulence and thickness of layer, surface tension, etc...im sure theres a lot of factors come into play, but...

that video i found is awesome makes me dream again despite knowing its pointless.

 

[Fabian]

i came to the conclusion, about 10 years ago, that coanda effect isnt that great.

You need to have a quiet chat to Adrian Newey. His opinion may be somewhat different.