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Philaflyer
Member
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Posted: Sun Jun 13th, 2010 08:24 pm |
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In looking at what has been posted so far, I’ve noticed that every discussion of power has been on mechanizing flapping for a constant power source. My interest is as much in control as power transmission. My early thoughts involved having a flywheel and clutches linked to cables to be able to pull them in a controlled but aggressively powerful manner: Something on the lines of the modern hydraulic disc brakes that allow “super bikes” to do “Stoppies” (a sort of reverse wheelie with the back end going up). Has anyone else considered this? I’ve also considered pneumatic power, but for the response needed for control, not only reservoired pressure, but continuous flow may be required. Has anyone done any integrated structural pneumatic design? I found an interesting paper on the subject: http://www.ilcdover.com/products/.../FEMofWarpingInflatableWings.pdf
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michael clark
Member
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Posted: Fri Jun 18th, 2010 12:57 am |
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I have done a bit of pneumatic work, only on models. I used model airplane gear retract cylinders. They worked well, but I didn't know enough about wing design to get anything to fly. This was many years ago, before flying model thopters were common.
As for anything larger, the old problem of efficiency keeps comming up. Do you use maximum pressure through out the piston's stroke, then exaust it all, wasting the pressure, or do you let the air expand during the power stroke, exaust at low pressure, and deal with the fact that force on the piston decreases through out the stroke?
I'm sure this is not a new idea, but what about exausting the high pressure air directly into the intake of the pneumatic compressor? (assuming that the system does not use compressed cylinders). This might recover some of the lost energy.
Michael
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Philaflyer
Member
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Posted: Fri Jun 18th, 2010 04:36 pm |
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The short answer is use short bursts for efficient power and lenghten the burst duration for more total power (Throttle control) at the expense of efficiency. I imagine a spring loading to balance the wings in a neutral position. this would make the whole structure behave like the piston in only needing bursts to make the wings flap.
However, using a traditional piston seems heavy to me. I was originally thinking of a pneumatic structure where inflated tubes offer part/most of the structural rigidity. With this design, varying the pressure in the structural tubes would stiffen and relax them causing a the wing to flap. Consider the writings of Otto Frei: ISBN-13: 978-0262650052 Circa 1968. Not an inexpensive double volume, but worth it.
Bill 
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