Item 0854

DESIGN: UniCopter ~ Rotor - Disk - Blade to Blade Clearance - 3-blade Rotors

Two intermeshing rotor disks with 3 blades each.

See DESIGN: UniCopter ~ Rotor - Blade - NACA 00xx - Planform & Thrust for latest planform and clearance of airfoils.

See DESIGN: UniCopter ~ Rotor - Disk - Pre-cone ~ Thoughts re Angle: for a means to improve the clearances.

Drawing:

This drawing has the latest disk radius. However, the stagger of 27" may be incorrect. It is currently 21"

In addition, on this drawing the obliquity is 9-deg. Not yet 3-deg plus precone & decone.

 

This drawing will have to be updated.

From the lower drawing ~ The vertical clearance, including 3º pre-cone, at the widest location of the chord is 5.369" and with the 16"chord the interaction is 0.16". If the mast-to-mast angle was increased from 18º to 20º then there will be a clearance of 0.54". Perhaps the mast-to-mast angle can be increased to only 19º.

Other thoughts;

    • Change the direction of rotation back to breast stroke?
    • Bring hubs closer together ???
    • Move the widest chord further out the span ??
    • Have seperate root control and set to zero pitch on retreating blade root?
    • Any other ????

For plan view of rotor disks see: DESIGN: UniCopter ~ Rotor - Disk - Downwash Intersection Azimuths

Notes:

I think that the 3-blade rotor will require the DESIGN: UniCopter ~ Rotor - Disk - Lateral Dissymmetry of Lift and Drag? - (3-blades) and (Swishring and Higher Harmonic Control) to eliminate lateral vibration at higher forward speeds.

 

FORM: Rotor - Disk - Interaction:

Input: The number of blades per rotor = 3, the stagger = 2'-6", the V-angle = 18º, the disk radius = 9'-6", and the azimuth of the port blade.

Output: It calculates the radius of the crossover on each blade and the Vertical ctr-ctr distance at intersection of the blades at this location.

At present, the calculations do not incorporate coning or blade flexure.

Calculations re Above Drawing:

 

Azimuth Upper blade. *

Azimuth Lower blade. *

Intersection radius Upper blade

Vertical ctr-ctr distance at intersection (1)

3º precone Upper blade (3)

Chord at on lower blade at intersection

3º precone Lower blade (4)

 Vertical ctr-ctr distance between blades. (5)

 

90º

270º

30.0"

4.69"

 

 

 

 

 

95º

155º

28.9"

4.33"

 

 

 

 

 

100º

160º

28.6"

4.13"

 

 

 

 

 

105º

165º

29.0"

4.06"

 

 

 

 

 

110º

170º

30.0"

4.13"

 

 

 

 

 

115º

175º

31.8"

4.32"

 

 

 

 

 

120º

180º

34.6"

4.69

2.11"

12.27"

-1.5"

5.28"

 

125º

185º

39.0"

5.3"

2.56"

14.94"

-2.0"

5.86"

 

130º

190º

46.0"

6.32"

 

 

 

 

 

135º

195º

58.0"

8.13"

 

 

 

 

 

140º

200º

82.4"

11.88"

 

 

 

 

 

143.0º (2)

203.0º

114.1"

16.79"

 

 

 

 
  1. The vertical distance between the feathering axes of the two blades where the axes intersect, not considering the pre-cone angle.
  2. Any greater and the 9'-6"R. blades do not overlap.
  3. The spanwise dimension for the cone is measured from the mast to the point on the trailing edge, which intersects the other blade's feathering axis.
  4. The spanwise dimension for the cone is measured from the mast to the intersection of its feathering axis and the trailing root of the other blade.
  5. Vertical clearance, which includes conning angles of both blades.

________________________

From the above FORM.

 *** The azimuth angles below are based on inside-forward (breaststroke) rotation. Add 180º to the values below to get the true azimuth (outside-forward) of the blade.

Additional Notes:

The vertical dimensions related to the cross-section of the blade in the above drawing will increase proportionately to any increase in the blade's chord.

Note: The height of the rotor hubs will be greater than the height of the blade, as shown in its cross-section.

Same Page ~ Same Craft, but 4-blade Rotors: ~ DESIGN: UniCopter ~ Rotor - Disk - Blade to Blade Clearance - 4-blade Rotors

Same Page ~ Different Craft: ~ SynchroLite ~ Dragonfly

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Last Revised: May 1, 2005