Roadable Aircraft DESIGN

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by WonderousMountain, Jan 23, 2012.

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  1. Jan 23, 2012 #1

    WonderousMountain

    WonderousMountain

    WonderousMountain

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    I'm no moderator,

    Just responding to a request for a thread devoted to improvement of the Air-car.

    Will post my own work when the three views are ready.

    1) as always play nice, if you don't care about the road-plane, don't post.

    2) Save your critisizm for planes-not people or countries.

    3) good people do not need rules-I'm not one.

    Blessings,

    Mountain
     
  2. Jan 23, 2012 #2

    Aircar

    Aircar

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    Good on you Wonderous --we have the ball rolling !
    I'll cook up a suitable "introduction" ASAP with my usual spare writing style..
     
  3. Jan 24, 2012 #3

    Aircar

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    ****! -got timed out again but think I might have saved it --need to get my IT guy to see how I can retrieve from files .

    In the meantime how about a few contributions --suggest things like most and least important preferences or general characteristics as aircraft as car or any unnacceptable features of either -that sort of thing.
     
  4. Jan 24, 2012 #4

    WonderousMountain

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    Low roll center in car form, unless it's a jeep style bushwacker. Favorable handling characteristics as a plane, decent roll rate and responsive to all control input. Good rate of climb, ingress for both modes. Subtle look of wings in road mode.
     
  5. Jan 24, 2012 #5

    Aircar

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    All good inputs WM -Still trying to get my "lost post" back and hoping to get the "introduction' piece up some time soon...
     
  6. Jan 24, 2012 #6

    topspeed100

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    May I add here;

    4. Rasism not tolerated !

    ?
     
  7. Jan 24, 2012 #7

    delta

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    Does anyone know if there's legislation that would prohibit prop propulsion on the road. It might be possible to incorporate retractable screens and thrust deflectors to protect your prop and tailgaters from debris. The transition from wheel drive to prop sounds more complicated to me.

    Rick

    ps.. Topspeed100... I think you just added #4 because you know there's no good Finnish jokes out there to come back and bite you...
     
  8. Jan 24, 2012 #8

    WonderousMountain

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    Actually, one of my friends is Finnish, and there's no shortage of jokes to go around.

    However, while I sympathize with you---I cannot protest if someone wants to talk about Races. There a long history both air and car races, and it's only a matter of time before someone suggests the use of a racing inspired technology or competition of some sort. If you don't like it, you can always fly or drive as slow as allowably/possible.

    Cheers,

    Mountain
     
  9. Jan 24, 2012 #9

    Daveed'

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    what would rutan do? i'd like a deconstruction of the bipod, especially of the untalked about (by rutan) power system. many thanks in advance. youse guys are my collective hero.
     
  10. Jan 24, 2012 #10

    bmcj

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    That's always been my thought/plan on my yet to be divulged design.

    (Actually, I used to openly promote the design idea, but no one seemed to buy into it, so I changed my direction to keep it quiet until I finally have a chance to try it out myself. I only speak out here because you spilled the beans on one of my secret plans :gig:.)

    To be honest, I'm not sure what the DOT reg would be on this, but there are many things on existing car that might be considered equally as dangerous.

    Bruce :)
     
  11. Jan 24, 2012 #11

    SVSUSteve

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    -Crash survivability
    This is one area where the weight issue is going to be a major factor because of the standards in place for cars. I'm not a fan of the flying car concept at all, but if I can help with this side of the projects, feel free to ask. It's a good academic exercise if nothing else and the technology that would come from such work would likely derive real benefit for the aircraft market.

    I'll ask my Norwegian ex-girlfriend. I'm pretty sure there are some out there. ;)

    The issue with retractable screens/thrust deflectors is that they are just one more system that would add complexity and maintenance issues to the design. Remember how poorly maintained a lot of cars are and work from the standpoint that if a flying car were to ever be put into wide scale use, it would probably be maintained to a similar level of disrepair. One of the major hurdles to the flying car concept would be if a mandate for aircraft style maintenance procedures were to be put into place as the maintenance costs alone would be prohibitive to the average person.

    Also, read: http://en.wikipedia.org/wiki/Lauda_Air_Flight_004 ....and consider what would happen if a poorly maintained thrust deflector were to deploy in flight. Given that most flying cars would likely be operated by relatively inexperienced pilots at low altitude.....you do the math on what would result.

    It depends on to whom, how severe the results would be and how likely the occurrence is. One kid getting into a prop because someone didn't maintain the shielding and you can kiss the market for that design goodbye once the news gets wind of the story.

    The more practical concern (besides the safety and complexity issues) is how would that vehicle handle on the ground in conditions with strong winds, icing, etc. Having rear thrust could likely make the vehicle more prone to fishtailing on wet and/or icy roads. Also, you'd likely have an issue with ice building up on the propeller in icing conditions which would reduce propulsive efficiency.

    Then there is also the issue of noise associated with an engine operating a propeller in the disrupted wake of the aircraft.

    The final argument I would have against that would be that such a system would likely lack the ability to finely control the speed of the vehicle as surface conditions and winds change.
     
  12. Jan 24, 2012 #12

    BBerson

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    Yes, I want prop drive as well.
    I think there was a roadable design (in Sport Aviation around the 60's) using prop drive on the highway. The guys name was Bryan, I think.

    I was thinking a prop drive would be neat and simple, even for a non flying car:ponder:. Just 5-10 lbs for a prop and no need for a transmission.
     
  13. Jan 24, 2012 #13

    Hot Wings

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    Does anyone know if there's legislation that would prohibit prop propulsion on the road.

    There are already laws in some municipalities specifically prohibiting just that, and you can bet the rest will have them within a few weeks of the first prop driven auto showing up (unless you can prove it won't kick up debris). Your car mode also should be bullet proof. Some folks get pretty ticked off when they have to buy a new windshield :shock:

    J. Hall mounted a couple of snowmobile engines on the back of his Chaparral's once to suck the air out from under the vehicle. They cornered like they were on rails but only lasted a race or so before they were ruled out of existence.

    Bipod's hybrid drive is an obvious solution to the dual mode propulsion.
     
  14. Jan 24, 2012 #14

    delta

    delta

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    "-I'm not a fan of the flying car concept at all, but if I can help with this side of the projects, feel free to ask."

    Your negative nay saying is of no help at all. Come to think of it, It might be helpful to this particular thread if you'd avoid keeping up with it since it is of no particular interest to you. See rule #1.

    Rick
     
  15. Jan 24, 2012 #15

    WonderousMountain

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    Fishtailing is often the result of applying power to the wheels, not the carframe. The wheels begin spinning and lose traction, it's hard to reduce power fast enough to keep to a strong turn. If we leave legislation out of it, props are limited in the thrust they can produce, where cars can accelerate about as good as their engine has power. Prop driven cars would need to be able to accelerate up a hill and from a stop. We could define a maximum slope the car could accelerate from a standstill. Offroading would pretty much mandate a drive. Prop driven roadables would need a good static thrust/weight ratio, and there's only the max width of the car for props-if that. Of course the prop would need a cage when we're not out in the bush.

    While picking up pebbles is conceivable, the possibility of picking up full size rocks and shooting them at windshields seems highly unlikely on a well paved road. Perhaps the front wheels should have a guard so as not to pick it up and then shoot it out. A bad sort of synergy.

    One point here is it seems possible to have prop drive on one end of the engine and a gearbox on the other. Disengaging a clutch is no big deal from an engineering standpoint. Of course this places the engine higher than I would like for prop clearance, but it stands as an option.
     
    Last edited: Jan 24, 2012
  16. Jan 24, 2012 #16

    SVSUSteve

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    I have useful information to add (see the rest of my posts on this thread) even if I think the concept is fatally flawed because of the operational consideration. I view the actual technology development as being an interesting exercise that may yield potential advances for other aspects of aviation even if the limitations I mentioned are somehow overcome. To put it another way, I don't care about the "road-plane" but I do care about the subsystems that could be developed especially with regards to the fuel system and safety aspects.

    To simply have a thread where nothing negative (or rather contrary to popular opinion) is allowed is not as likely to advance. Everyone needs a gut check now and then....marching in creative lockstep is simply the best way to wind up chasing one's own tail and not getting any closer to a set goal.

    If you truly believe I have nothing to offer, then why not show where my points on this thread have no validity rather than simply attacking me for not having developed a liking for the taste of a particular brand of Flavor Aid? Either we're designers and can take (and hopefully welcome) a little criticism or we are a bunch of zealots who only want to hear what want to hear. I didn't realize that pointing out some issues to be considered and overcome would be regarded so harshly.
     
  17. Jan 24, 2012 #17

    SVSUSteve

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    It's also an issue if you have unbalanced power between the wheels. This is one reason why rear-wheel drive vehicles handle very differently of slick surfaces than do front-wheel drive vehicles or four-wheel drive vehicles.

    So would operation in anything approaching mountainous terrain. The other issue I could foresee would the be need for a very small screen size to keep gravel and other FOD from road surfaces from damaging the prop. This would likely greatly impair the efficiency of the propeller. Without a screen of sufficiently small size (say a quarter inch or so for the sake of argument), operating the vehicle on anything but a paved road would carry a potentially high risk of damage to the propeller.

    I'd stick with nothing less than 12-14" of clearance between the lowest point of the blade arc (with a flat tire and the shocks at full stroke) to minimize the chance of damage to either the prop and/or its shroud. This seems to be a common recommended practice among aircraft operating off of grass strips.

    The other issue is that a significant number of people with the land necessary to takeoff and land on (such as my family; assuming the design has STOL capability) live on less than well paved roads. Given America's crumbling infrastructure, I don't see the state of our roads improving across the board any time soon.

    The issue with thrust to weight is going to be the mandate for safety equipment inherent with a road vehicle. This is where I think I can be most helpful to this thread since I am working currently on lightweight seats, restraints and fuel tanks for my own designs that would likely be helpful in keeping the weight down on your own project(s) while offering better performance than anything seen in aircraft and exceeding the current standards for motor vehicles.
     
  18. Jan 24, 2012 #18

    Rick McWilliams

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    I fly an amphibian. It can climb a very steep ramp, or sandy beach. Thrust is about 400 lbs, gross weight 1430. The problem is that high power is needed. Even 100Hp turning a 68 inch propeller can make quite a hurricane. Propulsive efficiency at zero speed is zero, at low speed it is very low. At highway speeds propulsive efficiency might get to 40%.
     
  19. Jan 24, 2012 #19

    Daveed'

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    rutan built the bipod, using electric only motor power on the road w speeds over 70 and electric motor for airspeed of he says 200 mph. these motors powered by 550 (?) cc motorcycle engines. two of em. comments please. how did he do the propulsive part of the system. what would rutan do?
     
  20. Jan 24, 2012 #20

    WonderousMountain

    WonderousMountain

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    Generator. Engine turns a generator, produces electricity, then uses electricity in four little electric motors. It's not perfectly efficient, but you are pretty much always using only what you need, which helps out along with a sleek design. Electric motors can be surprisingly light, and easy to fit, giving design flexibility.

    Thanks for the contribution Rick. You're thrust/weight is .32, or just under a third. Can you do a stoplight acceleration trial?
    We could calculate it, but it wouldn't be as fun...

    Wonderous Mountain
     
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