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Introduction

Yet another turn of the screw. A new iteration. The latest member of the T-Motor family: the F40-III. This is the third version of the brand's lead motor, worshipped by its efficiency and performance, smoothness, and power on demand. It seems like T-Motor have taken a step in the right direction. The developement of this product is focused mainly on three key points: efficiency, durability and cooling, all thanks to to a complete revamp. But words aren't just enough, it has to be proven; and this is the objective of this in-depth analysis.

We've gotten our hands on some pre-release units to test them and share the results with you. We chose the 2400Kv (there's also a 2600Kv and a 2750Kv variants) as it's the one that suits our "racing needs" the most.

 

Specifications

These are the most important specs of the motor:

  • KV: 2400
  • Stator size: 2306
  • Shaft diameter: 4 mm
  • Wire gauge: 18 AWG
  • Cable length: 100 mm
  • Weight without cables: 30.8 g
  • Weight with cables: 34.5 g
  • LiPo: 3-4S
  • Configuration: 12N14P
  • Internal resistance: 42 mOhm

If you want further, more detailed information about the specs, you can always find them in T-Motor's official website:

http://store-en.tmotor.com/goods.php?id=464

 

Analysis

At first glance you can already tell the exceptional quality, just like in all T-Motor's outrunner line-up; A very refined yet bare and robust look. In this version we won't find anything that stands out, aesthetically-wise.

Unlike it's predecessors, the silver top face of the bell is smooth and matte, with a laser-engraving of the model, serial number...The black in the ring and the silver base of the stator give the motor a very attractive look overall. As a curiosity, the matte-like finish is achieved by giving the pieces a sand-eroding treatment.

It's quite important to highlight the complete redesign of the bell to achieve greater rigidity and a constant air flow, which helps bring the temperature of the motor down slightly. T-Motor claims the overall working tempreature reduction is around 10ºC, comparing to other previous designs. Also, the hollow-shaft's walls have been reinforced to give the motor even greater rigidity.

Actually, there is something that stands out quite a bit: the orange in the motor's wires. These silicone wires are on the thick side (18 AWG), ideal to be soldered without the sleeving burning out and shrinking. The provided cable length allows for those 4 in 1 ESC builds, as they require longer motor cable length to be able to reach the centralized board.

As per usual, each motor comes with its accessories: screws (suitable even for those thicker 4mm carbon arms), some adjusting washers, e-clips and M5 aluminum prop locknut/nylock nut (really lightweight).

 

Thrust tests

We haven't missed the opportunity to put the T-Motor F40-III 2400Kv in our thrust stand to find out wheather it's all just words or if it actually performs as promised. To do so, we've chosen some of the most representative props of nowadays, as well as some "really old-school" ones.

Thrust / Amp draw / Efficiency

This is a very balanced motor in all its range, without excessive amp draws nor enormous thrust, with very linear tendencies all around.

If we take a look between the different props we've chosen, the ones that seem to make the most thust are the Cyclone 5050x3, at slightly above 1300g. We can also see that the amp draw peak at full throttle on these is above the 37A.

In terms of efficiency, we see a clear winner: the HQ Prop 5040x3 nylon fiber, with 1129g of thrust at only 23A. Surprisingly, the "old-school" DALProp 5040x3, despite being so thick and heavy, they manage to make 1235g of thrust at a mere 24A, acheiving an even better efficiency rating than the HQ Prop nylon propeller.

We also need to highlight the DALProp Cyclone 5050x2, that are quite surprising at nearly 1100g (and 27A peak amp draw), which isn't too bad for a bi-blade.

RPM / Torque

Just as expected, the higher the pitch and total blades per prop, makes the required torque increase. The highest is, of course, in the most powerful props (the Cyclone 5050x3). Inversely proportional, the RPM decrease as we go higher in pitch and blades per prop.

With these charts we can roughly determine what equipment (ESC, battery, PDB...) will suit this motor better depending on the prop we intend to use. This is a very balanced motor, without excessive amp draws, so a 30A ESC should be enough for pretty much anything.

 

F40-III vs F40-II

The data shown above doesn't make much sense on it's own. That's why we've decided to compare it to its predecessor's: the F40-II

Thrust, amp draw and efficiency

The evolution is quite present. The F40 III achieves a higher thrust on all props. It even gets better efficiency all across the board comparing it to it's older brother the V2, just as T-Motor claims.

To mention a negative aspect, we can say that over-propping affects the newer V3 slightly more than the V2.

RPM and Required Torque

 

Conclusions

As stated in the very beginning, T-Motor's developement in the F40-III is focused primarily in the efficiency, the durability and the cooling of the motor.

The first point refers to the performance and efficiency enhancement, which it really achieves. Based on the previous theorical comparison charts and analysis, the V3 has better specs than the V2. If you happen to have flown the V2, switching to the V3 will make you feel a better exiting of turns, as well as a bit more top speed in straights and a very linear power delivery.

The second point refers to the cooling of the motor. We've done an empirical but not too scientific test with two very similarly skilled pilots (@Pijuli and @MIJABA), and a nearly identical quad setup. The test consisted of draining an entire pack and monitoring the motor temperature by touching them. After the test, the V3 came down noticeably cooler than the V2.

Finally,the last of the goals of the F40-III was the durability. This is a very important point, as many V2 users have managed to snap shafts. Given the short time that these motors have been released for, we don't have experience enough as per to confirm if this point has been adressed correctly or not, but so far we can say that they've held up to some "rough landing" abuse...

 

Picture gallery:

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