Item 1107
DESIGN:
UniCopter ~ Rotor - Disk - Variable RRPMPage structured somewhat in US patent format for the heck of it.
Abstract:
A means of allowing the speed of the rotors (RRMP) and the engine RPM to be reduced thereby resulting in a quieter helicopter, and an increased endurance during hover. The reduced RRPM will also be advantageous when used with ABC during fast forward flight. The higher RRPM will be an advantage during high rates of climb.
Thought:
A constant speed slow rotor speed will reduced the profile drag in forward flight. This slow speed might not be detrimental in hover because in hover all eight blades will be sharing the load
. I must do some more comparative calculations to see how good this statement is.|
The Sikorsky ABCs implement variable speed rotors. The Stepniewski (concept) ~ Low Tip Speed Design Philosophy appears to have a constant slow speed.
Looking into the pros and cons of a fixed slow speed rotor (with a wider chord rotor). DESIGN: UniCopter ~ Rotor - Disk - Large Chord & Low Tip Speed - Fixed |
References:
US Patent Documents:
US patent ~ Optimum speed rotor ~ 6,007,298~ I'm not sure what is so patentable. At least one other helicopter reduces the RRPM slightly for longer quieter hover. This one just talks about an expanded range. ~ Have hard copy. In addition, the coaxial Sikorsky XH-59A ABC had two speed rotors.
Drawings:
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Description:
Field of the Concept:
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Background of the Concept:
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Description of the Drawings:
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Summary of the Concept:
The low RRPM during hover is accomplished by increasing the angle of attack on all blades, so that the lift/drag ratio is inproved.
Because of the extremely high rigidity, it may be possible to vary the RRPM by simply varying the engines RPM. This would be similar to a plane, where maximum power is only used occasionally and for a very short period of time.
The RPM's can be overridden by the collective grip. The desired RRPM is set by an adjustment device on one of the sticks, preferably the cyclic, which controls the rotor governor. There might also be a default button that quickly returns the RRPM to the its default value.
The
Really Rigid Rotors will allow for the RRPM to operate closer to natural blade frequencies.
Detailed Description of the Concept:
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Related Concept at this Web Site:
A serious concept being considered for the UniCopter;
DESIGN: UniCopter ~ Pusher Prop - General - Variable Speed Rotors and Prop
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Initially displayed: August 8, 2002 ~ Last Revised: July 10, 2008