HOBBYWING XRotor 3110 900KV

The HOBBYWING XRotor 3110 900KV is an FPV outrunner with 12 slots and 14 poles (12N14P) for long-range quadcopters and cinelifters with 8 to 9-inch propellers. Hobbywing is a Chinese maker of drives and speed controllers. The case measures 37.2 mm in diameter and 27 mm in height, and the mass is 89 g. As controller the maker names the XRotor FPV G2 65A 4-in-1.

At 900 KV the motor is tuned low: on 6S (22.2 V nominal) that is roughly 20,000 rpm unloaded, on 4S (14.8 V) roughly 13,300. Permitted cell counts are 4 to 6S, and the recommended propellers are HQ8x4.5x3, HQ9x4x3 and HQ9x5x3, that is three-blade propellers of 8 to 9 inches diameter. As peak values Hobbywing quotes 1,500 W and 63 A for 10 s, and the maximum thrust is 3,626 g.

10 s is a short time basis: it describes what the motor tolerates while accelerating, not what it delivers continuously in cruise. The peak current of 63 A sits only just below the 65 A of the recommended controller; in flight the load stays far below that, but anyone flying at the limit needs headroom in the controller. The thrust of 3,626 g holds for a particular propeller at a particular voltage and can only be compared with values taken under the same conditions. Cinelifters carry a heavy camera; operator registration falls due with a camera regardless of weight, and the class depends on the take-off mass of the whole drone.

A long-range drive runs for long periods under even load. The bearings and the insulating varnish of the winding age as a result, and heat builds up when the propeller is too large or the wind is strong. After a flight the motor should feel warm but not too hot to touch. Rough bearings, play in the bell and shaft wobble are the first checks; they also disturb the motion sensors of the flight controller.