0865

Item 0865

DESIGN: UniCopter ~ Rotor - Hub - ARR- Bearing - Mast

March 6, 2003 Seriously Consider a Crossed Roller Bearing for the Rotor Head:

See: OTHER: Mechanics - Bearing - Cylindrical Roller ??

Loading:

Due to Blade:

The normal (base) load will be during hover at gross weight. This load on the mast bearing will only be axial during hover since the centrifugal forces of all the blades will self cancel. The axial force on the mast bearing will have a value of only ((GW / 2) * secant(VM)) = 600 pounds, approximately. A vertical climb will not increase the loading much but maneuvers (cyclic activity) and perturbations (gusts) will greatly increase the loading.

Force and Moment from One Blade:

From: DESIGN: UniCopter ~ Rotor - Disk - Blade Generated Forces Currently 4-blade rotor only.

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)

Ultimate moment (thrust), @ hover: 10,837 x (4 [LLF] x 1.5 [SF] = 65,022 lb.-in. (289,232 N).

Ultimate torque, @ 100% RRPM (drag) in one blade = 13,537 / 3 blades = 4,512 lb.-in. (510 N-m.)

WAS from: DESIGN: UniCopter ~ Rotor - Blade - Composite - VR-7mod - Planform, Profile and Lift [OLD] ~ Blade Loading.

at 1G is 10,837 in-lb,
at 3G is 32,511 in-lb, and
at 10G is 108,370 in-lb.

Thrust Force ~ Radial Load on One Blade: Copied from 0859

Operating: 6,735 in-lbs. @ 1G: From page: DESIGN: Rotor - Blade - Composite - VR-7mod - Planform for ARR (2)

Ultimate thrust: 8,221 x (4 [LLF] x 1.5 [SF] = 49,326 lb. (219,413 N)

Due to Gears:

Probably not much compared to the above.

Crude Rough Calculation of Moment:

The distance across the center of the cross roller bearing item 1306 [MMXC 1932] from roller race to roller race is 7.48".

From above ~ Ultimate moment (thrust), @ hover: 10,837 x (4 [LLF] x 1.5 [SF] = 65,022 lb.-in. (289,232 N)

Transfer of 50% of the retreating blades load to the advancing side = 65,022 * 1.5 = 97,533 in-lb.

The loading is 97,533 in-lb / 7.48 in. = 13,039 lbs. 58,000 N

Re LAYOUT Item 0996:

The distance from the centerline of one bearing across the mast's centerline to the centerline of the other bearing is 7.0372".

The moment on one blade is 8,421 in-lbs from the center of the mast. (from 0850)

(4.0 [LLF - limit load factor] x 1.5 [SF - safety factor]) = 6 * 8,421 in-lb = 50,526 in-lb.

Transfer of 50% of the retreating blades load to the advancing side = 50,526 * 1.5 = 75,789 in-lb

The loading is 75,789 in-lb / 7 in. = 10,827 lbs. 48,161 N

With 50% ABC, the outer bearing is under 3 times the load as the inner bearing is. Maneuvers and gusts will increase the loading equally on both bearing, which will bring their comparative loads somewhat closer. This might imply that the outer bearing should be capable of handling a greater load.

Inner bearing: The SKF Thrust Ball Bearing 51218 has a dynamic load rating of 106,000 N, 23,830 lbf, Bearing weights 3.75 lbs. Consider using a 4-point contact ball bearing instead? Such as QJ 217 or QJ 218 N2
Outer Bearing: The SKF Thrust Ball Bearing 51144 has a dynamic load rating of 178,000 N, 40,016 lbf, Bearing weights 10.14 lbs. Consider using 51140 instead?

FORM: Rotor - Hub - Mast Bearings ~ UniCopter ~ Bold is the prefered BUT IT IS VERY LIGHT

Location:	Inner Bearing:		Outer Bearing:		X-roller Brg:
Bearing:	SKF 51218		SKF 51144		SKF MMXC 1932
Basic Dynamic Load Rating: [C]	106,000	N	178,000	N	85,800	N
Basic Static Load Rating: [Co]	305,000	N	800,000	N	143,000	N
Radial Load Factor for the Bearing: [X]	1		1		1
Axial Load Factor for the Bearing: [Y]	1		1		1
Actual Radial Bearing Load: [Fr]	0	N	0	N	0	N
Actual Axial Bearing Load: [Fa]	48160	N	48160	N	58000	N
Equivalent Dynamic Bearing Load: [P]	48160	N	48160	N	58001	N

Bearing Type:	Thrust Ball		Thrust Ball		X-cylindrical Roller

Basic Rating Life (in millions of revolutions): [L10]	11 ??		50 ??		3 ??
Rotor Revolutions per Minute: [nn]	733	RRPM	733	RRPM	480	RRPM
Basic Rating Life (in hours): [L10h]	242	hours	1148	hours	112	hours
Reliability: [rr]	97	%	97	%	97	%
Adjusted Ratting Life: [Ln]	107	hours	505	hours	49	hours

Bearing contact angle: [Theta]		deg.		deg.		deg.
Momentum Load: [M]		in-lb		in-lb		in-lb
Bearing Pitch Diameter: [PD]		in.		in.		in.
Equivalent Radial Load: [Pr]		lb		lb		lb
Weight: (each)	1.7 kg		4.6 kg		3.65 kg
1 Newton = 0.2248 Pound Force

Previously Considered Bearing Selection:

Angular Contact Thrust Bearing:

The NTN Angular Contact Thrust Bearing 562922M has a dynamic load rating of 12,100 lbf. and a static load rating of 43,500 lbf. The diameter across the ball track is about 5. 25". 87,500 / 5.25 = 16,666 lb. Bearing weights 4.3 lbs.

The NTN Angular Contact Thrust Bearing 562924M [Item 0848] has a dynamic load rating of 14,600 lbf. and a static load rating of 54,500 lbf. The diameter across the ball track is about 5.125". 87,500 / 5.125 = 17,073 lb. Bearing weights 6.6 lbs.

The NTN Angular Contact Thrust Bearing 562928M [Item 0869] has a dynamic load rating of 17,100 lbf. and a static load rating of 67,000 lbf. The diameter across the ball track is about 6.62". 87,500 / 6.62 = 13,217 lb. Bearing weights 8.7 lbs.

The NTN Angular Contact Thrust Bearing 562022M has a dynamic load rating of 21,500 lbf. and a static load rating of 71,000 lbf. The diameter across the ball track is about 5.5". 87,500 / 5. 5 = 15,910 lb. Bearing weights 10.8 lbs.

The NTN Angular Contact Thrust Bearing 5629348M [Item 0878] has a dynamic load rating of 24,900 lbf. and a static load rating of 111,000 lbf. The diameter across the ball track is about 7.97". 87,500 / 7.97 = 10,980 lb. Bearing weights 15.2 lbs.

The SKF Spherical Roller Thrust Bearing 29317 has a dynamic load rating of 59,500 lbf. 265,000 N. The diameter across the ball track is about 4.62". 87,500 / 4.62 = 18,940 lb. Bearing weights 6.48 lbs.

Can these bearings be split or supplied as single row w/ 60-degrees?

Consider Crossed Roller Bearing:.OTHER: Mechanics - Bearing - Crossed Cylindrical Roller

Kaydon Reali-slim (catalog 300). KG100XPO FORGET see below:

Notes:

Moment Loads:

When the loads act eccentrically on the bearing paired single row angular contact ball bearings or tapered roller bearings work best when arraigned back-to-back.

Kaydon Bearing Calculations: ~ Forget, since Kaydon cannot handle the speed.

Limiting speed :

N = (F_l*C_f * 1000)/ D ~ Actual speed 670 RRPM

N	RPM	150 RRPM
F_l	Derating factor	0.5 (guess)
C_f	Charted figures	3 (guess)
D	Bearing bore in inches	10

Type X Four-Point Contact:
Pr = (1.2M / PD Sin Θ) + 0.75F_r + 0.9F_t

Pr	Equivalent radial load	Never bothered to work out.
F_r	Radial load	300 lbs. (guess)
F_t	Thrust load	650 lbs. (hover at gross weight)
M	Moment load	38,545 (2 * 6,424 * 3G)
PD	Bearing pitch diameter in inches	11 inches
Θ	Bearing contact angle	30º for standard bearing

Life-Load-Speed Formulas:
L_h = (16,667 / S) * (C / P)³

L_h	L10 life in hours	Never bothered to work out.
S	Speed in RPM
C	Kadon dynamic load rating
P	Applied load

Same Page ~ Different Craft: ~ Electrotor-Simplex ~ Not quite, but probably in the future Dragonfly

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Last Revised: February 26, 2004