The FS3115 900KV brushless motors from LN-Motor are intended for 9 and 10 inch cine-lifter FPV drones. These motors can be used in X4 and X8 configurations, depending on how much payload you expect to install on your drone. Each motor can generate a max thrust of 4kg when equipped with a Genfan 10″ propeller or 3.3kg with an HQProp 9″ blade.
In my previous FPV motor review, I explained how to measure and identify motors based on their model number. Now, we will discuss your build’s optimal thrust/weight ratio.
Start with your drone’s total weight to determine your motor and propeller combination’s required power (thrust). The take-off weight has three main components:
- The drone itself – the frame, flight stack, FPV system, motors, and propellers
- Flight battery (1-12S LIPO and LI-ION battery up to 8000mAh) – Always choose the battery with the best weight/flight time ratio that does not affect flight performance.
- Additional detachable equipment – CineLifters are equipped with a professional camera that often weights more than the drone (1-2kg)
The unwritten guide of FPV drone builds says that the maximum thrust produced by all motors should be at least double (2:1 ratio) the aircraft’s total weight (including battery and additional equipment). For example, if you have a fully equipped cine-lifter drone weighing 4 kg, the total thrust generated by all motors should be at least 8kg -that’s 2kg thrust produced by each motor for an X4 configuration or 1 kg of an X8 design. In an X4 setup, the LN Motor FS3115 will produce 13-16Kg power -having extra thrust available is always a bonus. Hovering between 40-50% of the throttle would be optimal. For racing drones, things are changing; you will need at least a 10:1 thrust-to-weight ratio in order to win the race.
LN-Motor FS3115 review
Disclosure: I received these Cinelifter motors in a product review collaboration with LN-Motor. Although the motors were offered for free, all opinions in this article remain mine, and the sponsor did not influence me.
LN-MOTOR (Shenzhen Mingshi Innovation Technology) is an innovative technology enterprise focusing on producing brushless DC motors. “LN” comes from the Chinese names of the two founders, Lin and Na. Since I published my FS2812 motor review, the company changed its logo and slogan (see photo below).
The motors come in a bulky foam with included mounting screws and M5 nylon insert lock nut. The motors weigh about 106 grams, including the 25cm 18 AWG leads, and a set of four is close to half of a kilo, including 10-inch propellers. It has a 28mm stator width, 12mm stator height, and 19x19mm M3 mounting pattern. Looking down at the motor, you can see that it has a hollow shaft that saves some extra grams. A slight grip is milled into the top of the bell to prevent slipping the propeller. The entire motor is black except for some pink stripes on top of the bell.
The FS2812 900KV motors adopt a 12N14P configuration. The number before N refers to the number of copper coils in the stator, and the number before P refers to the number of magnets in the bell.
As mentioned, the LN-motor FS2812 suits 9 and 10″ long-range and CineLifter FPV drones. You can choose from 900KV and 1050KV versions -both support 3-6s power systems.
FS3115 motors: Technical parameters
| KV | 900KV and 1050KV |
| N/P | 12N14P |
| Shaft diameter | 5mm |
| Stator diameter | 31mm |
| Stator height | 15mm |
| Mounting pattern | ⌀19 M3 |
| Weight | 108 grams |
| Wires | 3x250mm 18AWG |
| Resistance | 46Ω |
| Voltage | 3-6S |
| Max Power | 1566W |
| Max Current | 65A |
| Efficiency | 2.37-4.97 g/W |
| Max thrust | 4135 grams |
What kind of ESC should you choose for the FS3115 900KV motors?
Typically, choosing ESCs with a rating of 10-20% greater than the peak current your motor draws at full throttle is recommended. So, if you look at the test performance table below, the LN-Motor FS3115 equipped with 9″ props reaches 59A at the maximum throttle and 10″ 65A at 100% throttle; to stay on the safe side, choosing an ESC rated at either 70A or 80A would be appropriate. Using a lower Amper ESC will not just result in an underpowered drone, but, most likely, the ESC will fail when you give max throttle. You can opt for individual ESC modules or a 4in1 board. I plan to use a BLITZ E80 Pro 4-IN-1 ESC that should power these motors bravely.
LN-Motor FS3115 900KV: Test performance
| Propeller | Throttle | Voltage (V) | Current (A) | Thrust (g) | RPM | Power (W) | Efficiency (g/w) |
| HQ 9″ | 50% | 25.2 | 11 | 1320 | 10430 | 277.20 | 4.76 |
| 60% | 25 | 17.2 | 1830 | 12121 | 430.00 | 4.26 | |
| 70% | 24.8 | 26.1 | 2321 | 13836 | 647.28 | 3.59 | |
| 80% | 24.7 | 36.7 | 2865 | 15313 | 906.49 | 3.16 | |
| 90% | 24.5 | 49.2 | 3371 | 16598 | 1205.40 | 2.80 | |
| 100% | 24.3 | 58.6 | 3369 | 17376 | 1423.98 | 2.37 | |
| GF 10″ | 50% | 25.2 | 11.9 | 1490 | 10591 | 299.88 | 4.97 |
| 60% | 24.8 | 18.9 | 1987 | 12171 | 468.72 | 4.24 | |
| 70% | 24.5 | 28.9 | 2653 | 13667 | 708.05 | 3.75 | |
| 80% | 24.3 | 39.7 | 3231 | 14978 | 964.71 | 3.35 | |
| 90% | 24.1 | 54.7 | 3856 | 15803 | 1318.27 | 2.93 | |
| 100% | 24.1 | 65 | 4135 | 16235 | 1566.50 | 2.64 |
9 and 10-inch frames for 3115 brushless motors
If you want to build an FPV drone using these FS3115 motors, choosing the right frame is crucial for performance and durability. Many no-name cheap frames are made from low-quality carbon fiber and designed in a garage without quality testing. Even if they can be twice as expensive, I recommend using frames from reputable brands such as iFlight, FlyFish-RC, GepRC, RekonFPV, Diatone, or AxisFlying. The Chimera 9, XL10, Amax F9L+DC9, GEP-Pulsar LR9, MANTA10, and Rekon10 PRO are excellent choices for these motors. For the X4 configuration, you must decide whether you prefer a true-X frame structure or deadcat-style without props in FPV view.
If you prefer X8 builds, the Honeybadger X8, Taurus X8 Pro, FilmMaster X8, and SHENDrones AKIRA 9 are the favorite frames of many CineLifter builders.