AV_Motor_Scale

General Requirement:

Four motors required. Two for the front and two for the aft PropRotors.

For a 1/8th scale 1,325 lb UniCopter each of the 4 rotors must deliver 58 watts of power. Page 1471 indicates that in might be only 22 watts.

What size and RPM/V is wanted? See motor page.

The RPM should be ???? for a ??? diameter rotor. See: AeroVantage ~ PropRotor - Scale Model

Selection:

To keep the thrust and the tip speed of the forward and the aft PropRotors close, the forward motors will be the slower AXI 2212/34 and the rear motors will be the AXI 2212/26 or the AXI 221220.

Motor w/ Hollow Shaft: (for 1/8 & 1/10 scales)

AXI Model Motors Site ~ Have hard copy

Hobby-Lobby International Inc.

http://www.mscomposit.com/motors/electric_92/brushless-outrunner/out-runner-for-evp-em-30034-hs---220834.html

ICARE ~ The EVP series of AXI motors are the hollow shaft version to be used with variable pitch props. The variable pitch props (EVP) can be found under the accessories page. Now available for 2208 and 2204

The EVPU blades with pitch change are symmetrical.

AXI 2204/xx Four of these will be too small for the 1/8 scale. 4 * 100 g to 280 g = 400 g to 1,120 g ( 0.88 lb to 2.47 lb)

AXI 2208/xx Four of these should be perfect for the 1/8 scale. 4 * 200 g to 500 g = 800 g to 2,000 g ( 1.76 lb to 4.41 lb)

AXI 2212/34 Four of these will be perfect for the 1/8 scale. 4 * 300 g to 800 g = 1,200 g to 3,200 g ( 2.64 lb to 7.05 lb)

2 only AXI 2208/xx and 2 only AXI 2204/xx = 600 g to 1,560 g ( 1.32 lb to 3.44 lb)

2 only AXI 2212/xx and 2 only AXI 2208/xx = 1,000 g to 2,600 g ( 2.20 lb to 5.73 lb)

This craft will not be as efficient as the airplanes for which the motors are 'recommended model weight'. There for only consider the last 2 options. Perhaps just run the smaller diameter proprotors faster.

Recommended setups for AXI 2212/34 GOLD LINE (from AXI motor page)

Number of Li-pol or Li-ion cells = 3s

Current capacity I_MAX= 10

Recommended speed controller JETI Advance plus = 12A

Propeller

Himax Motor Site ~ Brushless motors with Hollow Shaft and Variable Pitch Prop ~ Have hard copy

Dualsky ~ Have hard copy

Park 370 Outrunner Brushless Motor, 1200Kv w/ Hollow Shaft ~ Have hard copy

XTRA 2829/16 Brushless Motor Hollow Shaft ~ Have hard copy

So far I have not found a manufacturer that produces a unit greater than about 50g weight motor.

Specification Comparison of 1/8 and/or 1/10 Scale:

Perhaps 1/10 scale for 2 motor 1X2 and 1/8 scale for 4 motor 2x4.

Motor Name:	AXI	AXI	Himax	Dualsky	Park 370 HS	XTRA
Model:	2212/26	2212/34	2816	XM2834CA -10	EFL M1210HS	2826/15
RPM/V (kV)	840	740	xx	870	1,200	1,100
Max. Efficiency	79%	77%
Constant
Current - Continuous: (A)	6-10 A	4-8 A		10	10	4 - 8 A
Current - Max burst: (A)	12 A /60 s	10 A /60 s			12	9 A /60 s
No load current / xV	0,45 A; x=8	0,4 A; x=12
Lo: (A)			1.4		0.60
Kv			1220	870
Rm			0.058
Resistance	210 mohm	345 mohm	xx mohm	xx mohm	0.18 ohm	xx mohm
Diameter: (mm)	30	30	28		28
Length: (mm)	27.7	27.7	33		25
Weight (g)	57 g	57 g	79 g	xx g	45 g (1.6oz)	48 g
Shaft Dia (mm)	3,17mm	3,17mm	4mm		4mm (0.16")	3.17mm
Shaft	Hollow	Hollow	Hollow	Not sure	Hollow	Hollow
Brushless					Yes
Cells [Voltage range]	2-3S Li-Po	2-3S Li-Po		2..4	2-3S Li-Po	2-3S Li-Po
Brushless ESC:			25		12-20 amp
Recommended Model Wt:	300 - 700g	300 - 700g		<1,000g ~ aerobatic	170 - 340g
Max. Recommended Prop:	x	x	x	x	x	x

Motor w/ Hollow Shaft: (for 1/4 scale):

BUY: Motor - [Scale] - AXI - Front Motor of Model Double AXI 5330/20

Other and Homemade Outrunners: (perhaps for 1/4 scale):

Buy or make ones own brushless outrunner motor ~ Micro-Dan

Notes:

Synchronization; From RC Group Forum; "when driving two brushless motors from a single ESC they will always be in perfect sync."

This is not applicable to the quad rotor since all four motors will have different speeds at different times. However it might mean that RPM encoders are not required - just forget the feedback.

Torque; From RC Group Forum; "the more noticeable torque problem we associate with an outrunner as compared with an inrunner."

Efficiency; From RC Group Forum; "I remember them calling it "contra rotating" which sounded strange to me. Anyway someone purchased one and found that the prop pitch/diameter should be changed for the rear prop to improve efficiency."

Autorotation: "f you choose a brushless motor, then an autorotation gear is highly recommended. Most brushless motors have extremely high torque so when the motor spools down, the "braking" effect will be very strong. This will very likely break the main gear teeth if you do not have an autorotation gear."

Optional Size ~ 1/2 Scale:

Consider the Plettenberg motors; Plettenberg - Predator 30, the 37 and Plettenberg - HP 370/40 Heli

Castle Creations

Working Papers:

DESIGN:

B527

MAKE:

Items:

DESIGN:

	Name	Item

MAKE:

	Name	Item

BUY (Ref.):

	Name	Item
	1/8 scale and/or 1/10 scale
	BUY: Motor - Scale Model - AXI - Model 2212/26 and 2212/34	1630
	1/4 scale:
	BUY: Motor - Scale Model - AXI - Front Motor of Double AXI 5330/20	1753

Last Revised: September 6, 2009