Vertical hinge blades of the helicopter
In order to release the helicopter from the effects of variable strength in the plane of rotation of the rotor blade spar and relieve fatigue from stress in mounting the blade to the hub has, in addition to axial and horizontal hinges, one hinge - vertical (VSH).
About this hinge blade can be deflected in the plane of rotation and move upstream.
The equilibrium position of the blade in the plane of rotation is determined from the condition that the sum of all moments acting in the plane of rotation, relative to the vertical pivot high school.
0 resistance force creates a moment with respect to VSH equal that seeks to reject the blade back against rotation. Once the blade has deviated from the radial position at an angle which is called the angle of lag, arises shoulder centrifugal force relative to HS, and the time of the centrifugal force tending to return the blade to its original (radial) position
The rotary force generated on the blade in its scale and lowering, creates a relatively VSH time deflecting the blade during or upstream depending on flaps and lowered the blade. Shown advancing blade. Consequently, this blade flaps and rotating force is directed along the rotation. The moment will be equal.
In this case, the time of the turning force tends to return the blade to the radial position.
The equilibrium condition of the blade relative to the vertical joint can be written as follows:
The strength of the resistance of the air prevents the rotation of the blades. To blades rotate at a constant speed, it is necessary to attach to it a torque from the engine, which would be equal to the moment of resistance forces.
However, as we have seen, the power of resistance and turning the power during one revolution vary in size and strength, in addition, changes and direction. Because of this lag angle of the blade £ it changes all the time. The blade is around high school. Changes and the load on the engine, causing the shaking of the helicopter and fatigue stresses in the blade (somewhat less than in the absence of vertical hinge).
To reduce the vibrations of the blade in flight, so stop at the promotion and rotor on the ground, and, consequently, to reduce the shaking of the engine on a vertical hinge mounted damper. At the time of spin and stop the rotor natural frequency oscillations of the blades in the plane of rotation can fall into resonance revolutions that lead to strong rocking helicopter landing gear, especially when the chassis dampers operate satisfactorily.
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