Automotive How can we improve helicopter technology with a new flying car design?

[berkeman]

People always deny new ideas especially if they work in the industry and its not in their favour for something new and better to replace what they are doing. I can imagine that would be quite upsetting.

Please do not try to use this argument here at the PF. We do not allow suggestions of conspiracy theories or other apologia for misinformation.

 

[russ_watters]

You keep wanting to have some mechanism to generate additional lift without additional momentum flux, and it just doesn't work that way. No matter how you make lift, each Newton of lift will require that the vehicle adds 1 kg*m/s of momentum to the surrounding air each second. You seem to believe that the low pressure above the wing is somehow generating lift without adding to the momentum flux, and it isn't. 100% of the lift from a wing can be accounted for simply by measuring the downwash in the wake of the wing.

Indeed, for a helicopter or ducted fan, it should be easier to visualize that, since they create a fairly coherent column of moving air, who's velocity and/or momentum is easily calculated.

 

[amorphos_b]

multiple or aircraft sized winfThat a force has an equal and opposite is a bit like saying; did you know 2+2 = 4. But let me try another approach if i may...Imagine if instead of many little wings i had many little rotor blades or propellers, the thrust vectors would be respectively smaller and the dissipation of air into the general field of air would occur sooner. Ergo there would be less air blowing if you were stood say 10 ft away from it than an equivalent single rotor/propeller with a large thrust vector.The next thing to consider is efficiency whilst cruising at say 100 mph, wings have an element of gliding ability, whereas propellers have very little. Rotors, i agree have some wing like capacity in this sense, but not as much as aircraft wings [or multi-wings of same surface area]. Admittedly with my system only a proportion of the wings are meeting the oncoming air at anyone time, but the whole thing is still moving through air, and even that smaller amount is still far more than props or rotors.

 

[Mech_Engineer]

Imagine if instead of many little wings i had many little rotor blades or propellers, the thrust vectors would be respectively smaller and the dissipation of air into the general field of air would occur sooner. Ergo there would be less air blowing if you were stood say 10 ft away from it than an equivalent single rotor/propeller with a large thrust vector.

Please provide a citation for your assertion, any published result showing proof-of-concept for this claim will do. I think you'll find you are incorrect, but I'm open to being proven wrong.

The next thing to consider is efficiency whilst cruising at say 100 mph, wings have an element of gliding ability, whereas propellers have very little. Rotors, i agree have some wing like capacity in this sense, but not as much as aircraft wings [or multi-wings of same surface area]. Admittedly with my system only a proportion of the wings are meeting the oncoming air at anyone time, but the whole thing is still moving through air, and even that smaller amount is still far more than props or rotors.

I'll quote Akin's Laws of Spacecraft Design: 1. Engineering is done with numbers. Analysis without numbers is only an opinion.

Please provide an analysis or paper which shows this is the case, I think we'll all be better off if you start backing up your claims with reasonable proof via publications or calculations.

Edit- by the way, you need not distinguish between your design and rotors. They are the same thing, you just have a many-bladed design which you're claiming is more efficient through motivated reasoning but without providing any solid facts which prove it.

 

[amorphos_b]

Now you are just attempting to divert the issue, when if you are an expert then you already know the answers...

Noone has built such a device [multiple small propellers] as far as i know [i expect the motors wouldn’t be powerful enough]. I am speaking in theory and simply stating that smaller propellers produce smaller thrust vectors, are you saying this isn’t true? Or do you mean that the collection would be the same as a single blade doing the same job, because that at least would make sense. For it to be exactly the same the mass of blades would have to occupy the same area though, and you could spread them out or layer them such that a proportion of the thrust vectors have dissipated by the time it reaches the next layer of blades. I know we are only talking small differences but that’s all i am stating anyhow.Please answer the question; do wings glide more than rotor blades? A helicopter uses a lot of energy to stay in the air, and only the angle of the blades are driving it forwards. An airplane uses most of its energy to propel itself forwards and the act of pushing itself through the air keeps it up.
Please give me a little leeway, I am only asking simple questions which i know you know the answers to e.g. Small propellers have smaller thrust vectors. I am not trying to insult you or say that anything you have said is fundamentally wrong, i already stated that it would take the same amount of work to do the same job, and now you are asking me to provide existing cases for something that has not been built ~ and you already know that.

 

[berkeman]

Please answer the question; do wings glide more than rotor blades? A helicopter uses a lot of energy to stay in the air, and only the angle of the blades are driving it forwards. An airplane uses most of its energy to propel itself forwards and the act of pushing itself through the air keeps it up.

That's why a ducted fan tilt-rotor design fits well for a flying car design. You get VTOL and more efficient horizontal cruise.

Trying to do something different than a ducted fan for VTOL in this application doesn't seem practical. Your ideas about small fans and wings are not going to bear much fruit, I'm afraid.

 

[Nidum]

https://en.wikipedia.org/wiki/Avro_Canada_VZ-9_Avrocar

 

[amorphos_b]

^^ dear lord! you think I haven't seen old stuff like that unbalanced contraption!

you didn't answer any of my points specifically, so I may as well give up on trying to debate with you. all I am asking for is a sensible debate and help with the idea. this is not a game, it doesn't matter to me if you win. I just wish I could get help rather than people saying things I have already agreed with or otherwise stated. I said that the cover was a gauss and someone accused me of a fatal flaw where I was expecting enclosed wings to work, and I really expected better on physics forums.

cant you chaps just help instead?

 

[berkeman]

https://en.wikipedia.org/wiki/Avro_Canada_VZ-9_Avrocar

Interesting. Did they ever get it to fly above the ground effect?

 

[berkeman]

you didn't answer any of my points specifically, so I may as well give up on trying to debate with you. all I am asking for is a sensible debate and help with the idea. this is not a game, it doesn't matter to me if you win. I just wish I could get help rather than people saying things I have already agreed with or otherwise stated. I said that the cover was a gauss and someone accused me of a fatal flaw where I was expecting enclosed wings to work, and I really expected better on physics forums.

cant you chaps just help instead?

We are trying to help. What you are suggesting will not work well at all. The reasons have been explained fairly well, IMO.

 

[Nidum]

Interesting. Did they ever get it to fly above the ground effect?

The little version never got far off the ground and was very unstable .

As far as I know the larger advanced technology one never flew at all except in a few ground tethered tests .

 

[Ketch22]

^^ dear lord! you think I haven't seen old stuff like that unbalanced contraption!

you didn't answer any of my points specifically, so I may as well give up on trying to debate with you. all I am asking for is a sensible debate and help with the idea. this is not a game, it doesn't matter to me if you win. I just wish I could get help rather than people saying things I have already agreed with or otherwise stated. I said that the cover was a gauss and someone accused me of a fatal flaw where I was expecting enclosed wings to work, and I really expected better on physics forums.

cant you chaps just help instead?

There are a couple of issues with your concept that I have not seen addressed as of yet. I appreciate quite a bit that you are in search of a better solution. When I was in engineering college a very memorable professor created a lesson that we all failed at, the real take home was "never let your education get in the way of what you know." I have tried to work from this point of view for the rest of my career.

On to your design. An Airplane wing does not so much generate lift by pushing air down as it is drawn ( or sucked ) up. The increase in velocity of the air above the wing causes a low pressure region and the opposing high pressure region below creates an imbalance an the wing (an impermeable surface )which is trapped in the middle and is forced to move towards balance. The "down thrust" of a wing is only a part of the total lift.

If one were to place a series of wings oriented vertically the upper one would have highest "negative pressure" and the bottom of that wing would have a higher pressure area. However, the next wing is trying to suck air from a restricted source and thus sees less low pressure and due to the imparted angular momentum ( from the first wing) has less high pressure. This same pattern will be repeated with each stage until there is very little left to gain.

In a turbine such as a jet engine compressor or turbine this effect is compensated for by reducing the blade size with each stage. Look at a video on any gas turbine construction and you will notice that with each stage the root moves outwards creating a taper and thus a compensation for loss of efficiency.

So point number one to your new design. The root must taper and each stage loses efficiency. I would be interested to see, as I have not seen listed yet, how you are controlling for this significant loss of "thrust"

Also in your design I am seeing the planning (which I highly applaud) for your safety features. If one is to generate enough pure thrust to lift a vehicle with human occupants the inlet side will have a tremendous possibility to harm. Your plan is to have a very fine net with which to filter out or prevent inclusion of foreign objects. This is an interesting problem. The netting, no matter what the allowance, creates a restriction to air flow. The airflow is prime in developing thrust or lift as your plan is moving towards. This in turn increases forces on the netting and so the netting needs to be increased in size to have sufficient strength to not collapse. Please look at any of the military or civilian gas turbines that are designed for use around sand or other damaging materials. The screens that are used around the uptakes are large, robust, and heavy much like yours would need to be. To reduce this one needs to look at the amount of open area as a relationship to the blockage. If the protected area is for example 1000 in² and you have it covered with 300 in² of wire your uptake will only operate at 70%. Please refer to the first point of diminishing returns. As you are now running a diminishing return at 70% of theoretical.

I am looking at your design and I see something that is very heavy with low efficiency that only works if done with fictional materials. Please allow that I am very much in support of finding a better way. I am even more in support of thinking outside the box ( UC Jacobs was da bomb). However if you are not actually willing to work with the members here that provide valuable input, why are you posting?

 

[amorphos_b]

On the gadget show there was a guy with a hover-board made of multiple small rotor blades, the lady stood near it wasn’t getting her hair blown all over the place as she would with a helicopter. This is the difference small thrust vectors make!http://www.independent.co.uk/life-style/gadgets-and-tech/news/guy-comes-up-with-annoyingly-obvious-hoverboard-solution-breaks-world-record-10278561.html
Ketch22Hi, thanks for the good reply! I am concerned about how much loss would occur form one wing taking from the pressure vortex of the one above, as well as dirty air not helping. The size of the wings relative to distance would denote this loss ~ as you say, and this is why the wing mesh is fairly huge ~ my attempt to reduce this without it becoming to ugly. There would be some loss during VTOL but not total loss, because the majority of pressure regions are fairly local and the wings are small. The gap between them i think should be enough to let most of the normal wing function occur.I don’t know if this is helped once the vehicle is moving at speed? Would the airflow over the wings tighten the air vortexes?The honeycomb safety gauss would be made of ultra thin carbons, tubular hexagons ~ for strength. This would present something of a block to the air i agree, and naturally the thickness of the material would have to not be so thin [sharp] that it would grate ones fingers upon touch. Imho something like this should be used regardless of rotor type, if we are ever going to be able to use them in urban areas. Same applies to the detection requirements; i would be happier if there were a cloud 3D open world model, and each vehicle uploaded its location and schematics, such that the oncoming vehicles computers and pilots could see everything in their locality.I am happy to work with members here, and need help with this. As for fictional materials, well carbon fibre can be shaped then the resin is heated to solidify it once the shape is formed. I saw a documentary on lexus cars, where skilled artisans used irons to hand make the curves the machine which built the sheets of carbon couldn’t make. Artificial diamond is coming along strong, as you may know scratchless covers of mobile phones are made of diamond. At the moment only flat sheets of it can be made though.My thoughts on manufacturing are as like the additive steel welding technology, which uses steel continually welded to form a shape. Instead of a steel rod being fed into the arc welder, one could use a carbon particle gun spraying industrial diamond dust. Then to form curved shapes, air under high pressure could be feed through two opposing delivery systems; imagine something like two shower heads [analogy] with air forming a cushion between them, then that these can be moved between concave and convex positions, thus forming/shaping the molten carbon into shape. This would be for macro shapes relative to the resolution of the burn area.I wouldn’t attempt to build this prior to the existence of technology to make carbons, as the whole thing i feel is entirely reliant upon being very light. Equally remember that i am an artist, so the design reflected how i wanted it to look, whereas in fact a manufacturer would probably make the whole thing in more skeletal fashion.

the gauss will allow 30% of air passage only if it has that amount of material blocking the path.
_

 

[berkeman]

On the gadget show there was a guy with a hover-board made of multiple small rotor blades, the lady stood near it wasn’t getting her hair blown all over the place as she would with a helicopter. This is the difference small thrust vectors make!

This thread has gone far enough. Please take some aerodynamics and physics classes at your local community college. This thread is a waste of time.