h a l f b a k e r yThe word "How?" springs to mind at this point.
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CVT Aircraft
A 3 bladed helicopter which uses only one engine | |
Apparently I reinvented the CVT last night. I
was envisioning a flying machine which has a
cabin surrounded by 3 blades, but is powered
off only one engine. The blades are
positioned triangularly around and above the
cabin. The engine has variable diameter
pulleys that drive the blades allowing
the
pilot to the rate of rotation for each blade
independently while not changing the central
motor's rate.
Draganflayer
http://www.andybrai...ras/draganflyer.htm
[2 fries shy of a happy meal, Sep 09 2007]
[link]
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I assume you mean three rotors, not three blades. Which would be at least six blades. And how do you surround something three dimensional with only three planar surfaces? I think you will need at least four rotors. |
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Oh, and why do you want to do this? What is this accomplishing? |
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I guess I wasn't clear. I did mean 3
rotors, each consisting of 3 blades. |
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The rotors are positioned in a single
horizontal plane above the cabin where
the drive shaft of the engine protrudes
(the same plane that a traditional
helicopter rotor resides in). |
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Why, shirley this is no place for that
question. Honestly, because the mental
picture I had flicked on that little light
that make you want to do something
just because. It may not work, its not
very well thought out, and its most
likely no better than any existing
system. But it would look cool and
different and it was an interesting
thought. At least to me. |
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Ah! So they are all coplanar above the cabin. One going clockwise and the other two counterclockwise (anticlockwise). Or vice versa. In that case you are going to need to do something to keep the cabin from spinning in the direction of the odd rotor. An internal gyroscope or external tail rotor would do it. |
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This will be a bitch and a half to fly, but so what, that is what fly by wire and test pilots are for, right? |
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Like this [bleh]?
[link]
but with three rotors and one motor? |
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Yes, sort of like that 2 fries, but with 3
rotors. |
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If the frame the rotors are attached to is
mounted directly to the cabin, would it
still need something to keep the cabin
from spinning? |
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also, why is there an odd rotor? it
seems to me they will all be spinning
the same direction, but I may be
visualizing it wrong. |
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Two rotors are typically set up to counter rotate, one clockwise, one anticlockwise (counterclockwise). That way the torque cancels out. Three rotors(or any odd number) would not be able to do this, so there will always be some torque that needs to be dealt with or the cabin will spin. |
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//Two rotors are typically set up to
counter rotate, one clockwise, one
anticlockwise (counterclockwise). That
way the torque cancels out.// |
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Would you still need to do this if the
rotors are not on the same axle? Having
one rotate the opposite direction would
complicate things. |
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It's probably clear by now but I am no
engineer [yet (another 2 years)]. |
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Yes, this is just a matter of Newtonian physics. If a motor tries to spin a shaft one way, the motor is going to try to spin the other. If you use a drive train to split the spinning mass into equal parts going opposite directions (or use two power plants) they counter act each other. |
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With 3 rotors the cabin will rotate unless one of the rotors is rotating in the opposite direction to the other 2 at twice the speed (or has twice the area). |
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I can see no advantage to this arrangement. |
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I think what you are aiming for could be achieved fairly easily with a layout of 4 rotors and I'm pretty sure I've seen that somewhere. |
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Using 3 rotors you could have a main rotor slightly behind the centre of gravity and 2 smaller maneuvering rotors in front and out to the sides. As with most helicopters, the rotational speed of the 3 rotors can be linked, with only the pitch being altered independently. This would be a lot more complicated to fly that the 4 rotor arrangement and would only allow a more fixed-wing aeroplane style of flying, eliminating some of the maneuvers possible in a helicopter. |
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Well, I still don't understand fully, but I
havent diagramed it or put any research
into it at this point. |
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The only real reason I went w/3 rotors
as opposed to 4 is because I thought 3
would look cooler. 4 Is fine by me. |
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Alternatively, can the 3 rotor version all
rotate the same way with each rotor
having a slight pitch to counteract the
rotation of the cabin? |
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If anything other than exactly half of the rotors are rotating each direction, you are going to have torque to deal with. (assuming rotors are the same size, same speed, yada yada). There are ways to deal with this. The very traditional tail rotor for one. Or the motor could be spinning freely on bearings inside the cabin. Or you could have six rotors in three counter-rotating concentric pairs (three shafts with two rotors on each, one above the other spinning in opposite directions). The last option might give you the look you are seeking. |
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//Or the motor could be spinning freely on
bearings inside the cabin.// So, motor at
3000rpm clockwise, and blades at 100rpm
anticlockwise? Hmmm. |
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Well, maybe not freely. Put a brake and some automatic controls and I bet it could control yaw pretty effectively. |
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