1561

Item 1561

DESIGN: Electrotor-MicroLite - Power Train - Bearing - Rotor & Gear

Choices for Rotor Bearing:

Gyrobee:

Reference: The Gyrobee's only Main Rotor Bearing is: #5206. Torrington Catalog, Fafner Ball Bearings, page 43. It is a double row angular contact ball bearing and the angle is 30º. Its weight is 0.65 lbs. The static load rating is 5,200 lbs and the dynamic load rating is 8,650 lbs. A supplier and specs; http://www.skatebearings.com/5206-2RS-5206-ZZ.htm.

The craft has a maximum weight of 500 lbs, a single rotor with a teetering head.

For calculations on gyrocopter rotor bearings see OTHER: Mechanics - Bearing ~ Gyrocopter.

___________________

MicroLite:

For Kaydon and RCB thin bearings see OTHER: Mechanics - Bearing.

"Full Power Flight: Assume the craft to be flying at maximum speed with full torque applied to rotor, and a maneuver made with full control displacement.

Limit load factor for rotor thrust loads =4.0.

Safety factor of 1.5 should be used with the above loads" [Source ~ MDD p.11]. This give a multiplier of 6:1.

Also apply the above to the bolts on the appropriate web page. DESIGN: Electrotor-MicroLite ~ Power Train - Miscellaneous

Calculations:

Rotor radius = 60"
70% of rotor radius = 42"
For 2-blade rotors; The average thrust per blade is 300 lbs GW / 4 = 75 lbs.
For 3-blade rotors; The average thrust per blade is 300 lbs GW / 6 = 50 lbs.
Increase by 3 fold for maneuvering = 225 lbs and 150 lbs.
Moment on bearings = 225 lbs x 42" =9,450 in-lb. and 150 lbs x 42" =6,300 in-lb.
Safety factor of 2:1. Including this gives a multiplier of 6:1.
Moment on bearings w/ safety factor = 450 lbs x 42" =18,900 in-lb. and = 300 lbs x 42" =12,600 in-lb.
Moment on bearings w/o maneuvering and safety factor = 75 lbs x 42" =3,150 in-lb. and = 50 lbs x 42" =2,100 in-lb.
I assume that with 3-blade rotors the moment will be less but not as low as 2/3s.
Do not get bearing with internal preload since it will probably consume extra power.
The contact angle of the Kaydontype X bearings is 30º, which is the same as the Gyrobee's main bearing

	Bearing:	Item:	Metric/Imperial:	Bore:	OD:	Width:	Weight:	Dynamic Moment or Thrust:
⁽³⁾	Kaydon KF040XPO		Imperial	4.00"	5.50"	0.75"	0.86kg, 1.9lbs	6,490lb-ins
⁽³⁾	Kaydon BB10020	1781	Metric	100mm, 3.94"	150mm, 5.90"	20mm, 0.787"	1.21kg, 2.67lbs	9,753lb-ins
⁽³⁾	Kaydon KG040XPO		Imperial	4.00"	6.00"	1.00"	1.63kg, 3.6lbs	11,260lb-ins
⁽³⁾	Kaydon KF050XPO	1843?	Imperial	5.00"	6.50"	0.75"	1.05kg, 2.3lbs	8,920lb-ins ⁽¹⁾
⁽³⁾	Kaydon KG050XPO	1843?	Imperial	5.00"	7.00"	1.00"	1.95kg, 4.3lbs	15,250lb-ins ⁽¹⁾
⁽³⁾	Kaydon BB11020		Metric	110mm, 4.33"	160mm, 6.30"	20mm, 0.787"	1.36kg, 3.0lbs	11,506lb-ins
	Kaydon KD045ARO		Imperial	4.50"	5.50"	0.50"	0.88 lbs x 2	4,570lb thrust ⁽²⁾
	Kaydon KD047ARO		Imperial	4.75"	5.75"	0.50"	0.93 lbs x 2	4,720lb thrust ⁽²⁾
	Kaydon KD050ARO		Imperial	5.00"	6.00"	0.50"	0.98 lbs x 2	4,870lb thrust ⁽²⁾
	Kaydon KD055ARO		Imperial	5.50"	6.50"	0.50"	1.06 lbs x 2	5,160lb thrust ⁽²⁾
	Kaydon KF055ARO		Imperial	5.50"	7.00"	0.75"	2.59 lbs x 2	10,060lb thrust
	Kaydon KG060ARO		Imperial	7.00"	8.00"	1.00"	5.07 lbs x 2	17,060lb thrust

It appears that Item 1843 will not be strong enough.

These have more than half the dynamic thrust rating of the Gyrobee bearing, and this craft has 300/505 the GW plus 2 rotors, but it will have greater moments.

These are all 'X' bearings and their limiting speed rating is too low for the MicroLite rotors. However, on page Kaydon page 64 it says "If a shorter life is acceptable, higher speeds may be tolerated, ...."

Miscellaneous:

Kaydon Type A - Angular Contact ~ Duplex Bearings: See Kaydon Manual page 48.

Bearings to be ordered as matched sets.
Bearings to be installed Back-to-back.
See Kaydon Manual page 48.

Kaydon - Limiting Speeds: See Kaydon Manual page 64.

The following assumes; 3-blade rotors, no 3-fold increase for maneuvering due to infrequency, and no safety factor preceding that of the bearing.
Note that the bearings are calculated by Kaydon for a full service life of 1,000,000 revolutions.


Power Train Assembly:	1841 & 1842	1858	1879	1841 & 1842
Bearing:	Item 1843??	Item 1843 ??		Item 1843 ??
Bearing:	KF050XPO	KF050XPO		KG050XPO
Series: See page 6.	F	F		G
Bore: (D)	5"	5"		5"
Slimness Symbol: (S_S)	I	I		I
Loading on Bearing:	6,300	6,300		6,300
Dynamic Moment Rating:	8.920	8,920		15,250
Derating Factor: (F_I)	.7	.7		1.0
Class and Lubrication:	1 & Oil	1 & Oil		1 & Oil
Charted Figure: (C_f)	4	4		4
Limiting Speed: (N) RPM ⁽¹⁾ ⁽⁴⁾	560	560		680
Limiting Speed: (N) RPM ⁽²⁾ ⁽⁴⁾	720	720		800
Actual Speeds: RPM ⁽³⁾ ⁽⁴⁾	1,500 & 1,000	1,500 & 1,000		1,500 & 1,000

(1) N = (F_I) (C_f) (1000) / D

(2) If the Loading on Bearing is 3,150 [based on infrequent maneuvering] then the Derating factor is 0.9 and the Limiting Speed is higher.

(3) The RRPM of the rotors will be 6,000 x 4:1 = 1500 for IVO blades and 6,000 x 6:1 =1,000 for custom blades.

(4) Type 'A' and 'C' bearings accept approximately 4 times the rpm speed as do the type 'X' 9ref Fig. 47)

Type 'A' bearings appear to be best in a Back-to- back arrangement but need, or are better, with a spacer between them. (see; Fig. 30 and page 84).

With back-to-back bearings "The bearings are adjustable through the inner races by using shims under the inner race clamping ring." (see; Fig. 20).

Type 'A' bearings must be purchased as a matched set.

See note on page 57 re 'X' type re retainer an pocket opening down or extension on shaft or housing..

The KG050XPO, for which I have not yet done the calculations, may not be satisfactory in respect to RPM and in respect to capacity when looking at the Gyrobee's bearing above OTHER: Mechanics - Bearing ~ Gyrocopter.

If a pair of 12" square 'A' bearings are to be used then the billet should be moved up 1/4" and a 1/2" retainer used at the bottom.

Last Revised: December 2, 2009