Item 1069

DESIGN: UniCopter ~ Rotor - Hub - ARR - Blade Generated Forces - Intermediate

Must be completely reviewed and changed.

Currently for 4-blades only at present

For use in calculating loading on blade, pitch bearings, hub, mast bearing & transmission frame.

To pictorially view the moment arms and blade areas at blade elements see: DESIGN: UniCopter ~ Rotor - Blade - VR-7modified - Planform, Profiles and Lift. To see if the length of the moment arms can be reduced.

Will some of the information on this page eventually come from a UniCopter page similar to; DESIGN: SynchroLite ~ Rotor - Blade - Composite - VR-7b - Centers, Radii & Moments later?

Characteristics:

OTHER: Helicopter Specification - UniCopter ~ 4-blade rotor

Characteristics from above:

Mode is Hover. GW is 1150 lbs. Rotor speed = 480 RPM. Blade weight = 15.4 lbs. Tip weight = 0 lbs. Rotor radius = 9'-3". Blade length = ?'-?". Twist = active. Taper + 1.222"/ft. The blade is divided into 10 elements.

Note that the blade weight is currently a guess.

Note that the rotor radius will probably be 9'-3", plus 3" curved tip with anhedral.

OTHER: Helicopter Specification - UniCopter ~ 3-blade rotor

Characteristics from above:

Mode is Hover. GW is 1150 lbs. Rotor speed = 480 RPM. Blade weight = 21 lbs. Tip weight = 0 lbs. Rotor radius = 9'-6". Blade length = ?'-?". Twist = active. Taper + 1.368"/ft. The blade is divided into 10 elements.

Note that the blade weight is currently a guess.

Note that the rotor radius will probably be 9'-6", plus 3" curved tip with anhedral.

ALL THE FOLLOWING IS BASED ON THE 4-BLADE ROTOR

Axial Force (Centripetal Force) on One Blade, at 100% RRPM:

The centripetal force F [in pounds] acting on a body of mass M [in slugs] is given by the equation F = (Mv2)/r, where v [in feet per second] is its velocity and r [in feet] is the radius of its path. See: Mechanical - Definitions & Algorithms ~ Centripetal Force

Blade Element

Radius (inch) & [feet] to mid point of elements

Weight (lbs.) & [slugs] (1)

Velocity (ft./sec.)

Force (lbs.)

1

11.1" / 2 = 5.55" [0.46]

1.54 [0.048]

23

55

2

11.1" + 5.55 = 16.65" [1.39]

1.54 [0.048]

70

169

3

11.1" + 16.65 = 27.65" [2.30]

1.54 [0.048]

116

281

4

11.1" + 27.65 = 38.85" [3.24]

1.54 [0.048]

163

394

5

11.1" + 38.85 = 49.95" [4.16]

1.54 [0.048]

209

504

6

11.1" + 49.95 = 61.05" [5.09]

1.54 [0.048]

256

618

7

11.1" + 61.05 = 72.15" [6.01]

1.54 [0.048]

302

728

8

11.1" + 72.15 = 83.25" [6.94]

1.54 [0.048]

349

842

9

11.1" + 83.25 = 94.35" [7.86]

1.54 [0.048]

395

953

10

11.1" + 94.35 = 105.45" [8.79]

1.54 [0.048]

442

1067

Tip weight

111" [9.25]

0.0 [0.0]

465

0

Total: Based on 100% RRPM. (2)

15.4 []

 

5,611

 

(1) The weight is currently equal for every element. (Root end will have more structure and tip end may have more tip/leading edge weight).

(2) In autorotation it is possible that the rotational speed may increase to 3G or 173% RRPM .

Ultimate centrifugal force @ 100% RRPM = 5,611 x (4.0 [LLF - limit load factor] x 1.5 [SF - safety factor]) = 33,666 lb. (149,754 N)

_________________________________

Note: If the pitch bearings could be located out 1'-6" further from the mast, just inside the other mast, then the axial load will be about 8% less.

Radial Force (Aerodynamic Force) on One Blade, at hover:

Thrust Force ~ Out of Plane Radial Load on One Blade:

The following is based on thrust = GW / 8 blades = 144 pounds. Less 15.5 pounds for the blade.

 

For Pitch Bearings:

For Mast Bearing & Frame:

Blade Element:

Radius at outside of element (ft.)

Coefficient of Thrust w/ Tip Loss

Lift (pounds) (1)

Lift (pounds) (2)

Length of Arm to 75% of element (in.) (3)

Moment (lb.-in.) (4)

Length of Arm to 75% of element (in.)

Moment (lb.-in.)

0

0

0

0

0

0

0

 

0

1

0.93

0

0

-1.54

1.3"

-2

 

0

2

1.85

0

0

-1.54

12.4"

-19

 

0

3

2.78

0

0

-1.54

23.5"

-36

 

x

4

3.7

0.0025

6.2

4.66

34.6"

161

 

x

5

4.63

0.0032

7.9

6.36

45.7"

290

 

x

6

5.55

0.0049

12.1

10.56

56.8"

600

 

x

7

6.48

0.0072

17.8

16.26

67.9"

1104

 

x

8

7.4

0.0100

24.8

23.26

79.0"

1838

 

x

9

8.33

0.0136

33.7

32.16

90.1"

2898

 

x

10

9.25

0.0166

41.1

39.56

101.2"

4003

 

x

 

Total =

0.0580

143.75

128.35

 

10,837

 

x

 

(1) These values come from FORM: Elements after running FORM: Rotor - Blade. They are 1/8 of the disk values at each element

(2) These values are the previous column with weight of the blade (15.5 lbs) removed equally from all elements with lift.

(3) Element is 11.1" long. Moment arm is at the 75% point of element (8.33") and blades pivot is located at 7" radius from rotor's centerline. The 7" dimension should probably be increased by a couple of inches.

(4) At; hover, gross weight & out of ground effect. From Access Database calculations.

Ultimate moment @ hover: 10,837 x (4 [LLF] x 1.5 [SF] = 65,022 lbf.-in. (7,346 N-m).

_________________________________

Note: If the pitch bearings were to be located out 1'-6" further from the mast, just inside the other mast, then the radial moment will be about 22% less.

Torque Moment ~ In Plane Radial Load on One Blade, @ 100% RRPM:

Operating torque in of rotor = ((63,000) x 65 HP) / (480 RRPM x 2 rotors) = 4,266 lb.-in.

Operating torque in one blade = 4,266 lb.-in. / 4 blades = 1,066 lb.-in.

Ultimate torque (drag) in one blade = 1,066 x 2.0 [LLF] x 2.25 [SF or 150% RRPM] = 2,135 lbf.-in. (241 N-m.)

Combined Radial Moment:

Ultimate Radial moment = square root (2,1352 + 65,0222) = 65,057 lbf-in. (7,350 N-m)

Torsional Force:

This may be handled by the skin.

Same Page ~ Different Craft: ~ Dragonfly ~ SynchroLite (none)

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Last Revised: October 3, 2004