I’ve heard a lot of mixed information about how number of blades can affect performance and duration of the flight of your racing drone, so I’ve decided to put my thrust test stand to a good use and test various micro motors I had on hand and different propeller configurations.
Motors
- 1102 10000kv
- 1102 7800kv
- 1104 6500kv
Propellers
- 2535-2 blades
- 2535-4 blades
- 2535-2 blades cut down to 1.88″
- 2535-4 blades cut down to 1.88″
Methodology
I’ve run each micro racing motor for 3 times with each of commonly used propellers on ~50% throttle and ~100% throttle. For each run I’ve used different battery. Then I’ve picked average result.
Disclaimer
I doubt that data I’ve collected are 100% accurate, so they should be considered with the grain of salt.
1102 10000kv motor
1.88″ propeller with 2 blades (2S battery)
1.88″ propeller with 4 blades (2S battery)
Summary for 1102 10000kv with 1.88″ propellers
| Motor | Propeller | Throttle | Amps | Watts | Thrust | g/W |
|---|---|---|---|---|---|---|
| 1102 10000kv | 1935-2 | 50% | 2.13A | 17.1W | 21g | 1.23 |
| 1102 10000kv | 1935-2 | 100% | 4.27A | 33.1W | 35g | 1.06 |
| 1102 10000kv | 1935-4 | 50% | 2.7A | 22.5W | 22g | 0.98 |
| 1102 10000kv | 1935-4 | 100% | 4.99A | 39.5W | 34g | 0.86 |
I’ve noticed that when motor was spinning on full throttle with 1935-4 blades propeller there was a bit of burning smell and motor was hot after it. So 1935-2 blades was a clear winner in this case.
2.5″ propeller with 2 blades (2S battery)
2.5″ propeller with 4 blades (2S battery)
Summary for 1102 10000kv with 2.5″ propellers
| Motor | Propeller | Throttle | Amps | Watts | Thrust | g/W |
|---|---|---|---|---|---|---|
| 1102 10000kv | 2535-2 | 50% | 2.7A | 22.1W | 27g | 1.22 |
| 1102 10000kv | 2535-2 | 100% | 5.09A | 39.6W | 35g | 1.01 |
| 1102 10000kv | 2535-4 | 50% | 2.68A | 22W | 22g | 1.09 |
| 1102 10000kv | 2535-4 | 100% | 5.72A | 45.3W | 34g | 0.8 |
At around 50% throttle 2.5″ 2 blades propeller seems to have advantage over 1.88″ but later on difference in thrust almost disappears which suggests that 2.5″ 2 blades propeller might be the maximum 1102 10000kv motor can handle.
2 blades has clear advantage over 4 blades in this case as well.
1102 7800kv motor (2S battery)
1.88″ propeller with 2 blades
1.88″ propeller with 4 blades
Summary for 1102 7800kv with 1.88″ propellers
| Motor | Propeller | Throttle | Amps | Watts | Thrust | g/W |
|---|---|---|---|---|---|---|
| 1102 7800kv | 1935-2 | 50% | 1.56A | 12.9W | 20g | 1.55 |
| 1102 7800kv | 1935-2 | 100% | 2.89A | 23.2W | 32g | 1.38 |
| 1102 7800kv | 1935-4 | 50% | 1.94A | 15.9W | 19g | 1.19 |
| 1102 7800kv | 1935-4 | 100% | 3.36A | 27.3W | 29g | 1.06 |
In the case of 1102 7800kv 2 blades seem to have an advantage as well. Efficiency has increased in comparison to 10000kv.
2.5″ propeller with 2 blades (2S battery)
2.5″ propeller with 4 blades (2S battery)
Summary for 1102 7800kv with 2.5″ propellers
| Motor | Propeller | Throttle | Amps | Watts | Thrust | g/W |
|---|---|---|---|---|---|---|
| 1102 7800kv | 2535-2 | 50% | 1.86A | 15.3W | 28g | 1.83 |
| 1102 7800kv | 2535-2 | 100% | 3.7A | 29.3W | 43g | 1.47 |
| 1102 7800kv | 2535-4 | 50% | 2.12A | 17W | 29g | 1.7 |
| 1102 7800kv | 2535-4 | 100% | 4.23A | 33.5W | 40g | 1.19 |
In case of 1102 7800kv 2535-2 seems to perform better than other configurations.4 blades were still making motor very hot.
1104/5 6500kv motor
1.88″ propeller with 2 blades (2S battery)
1.88″ propeller with 2 blades (3S battery)
1.88″ propeller with 4 blades
1.88″ propeller with 4 blades (3S battery)
Summary for 1104/5 6500kv with 1.88″ propellers
| Motor | Propeller | Throttle | Amps | Watts | Thrust | g/W |
|---|---|---|---|---|---|---|
| 1104/5 6500kv | 1935-2 | 50% | 1.7A | 13.7W | 26g | 1.9 |
| 1104/5 6500kv | 1935-2 | 100% | 3.51A | 27.7W | 49g | 1.76 |
| 1104/5 6500kv | 1935-4 | 50% | 2.71A | 21.4W | 36g | 1.68 |
| 1104/5 6500kv | 1935-4 | 100% | 4.61A | 35.8W | 54g | 1.51 |
| 1104/5 6500kv 3S | 1935-2 | 50% | 2.74A | 32.4W | 50g | 1.54 |
| 1104/5 6500kv 3S | 1935-2 | 100% | 5.28A | 58.6W | 79g | 1.35 |
| 1104/5 6500kv 3S | 1935-4 | 50% | 4.44A | 51.3W | 63g | 1.22 |
| 1104/5 6500kv 3S | 1935-4 | 100% | 6.62A | 73.1W | 82g | 1.12 |
1104/5 6500kv motor
2.5″ propeller with 2 blades (2S battery)
2.5″ propeller with 2 blades (3S battery)
2.5″ propeller with 4 blades
2.5″ propeller with 4 blades (3S battery)
Summary for 1104/5 6500kv with 2.5″ propellers
| Motor | Propeller | Throttle | Amps | Watts | Thrust | g/W |
|---|---|---|---|---|---|---|
| 1104/5 6500kv | 2535-2 | 50% | 2.94A | 23.7W | 47g | 1.98 |
| 1104/5 6500kv | 2535-2 | 100% | 5.18A | 39.5W | 72g | 1.82 |
| 1104/5 6500kv | 2535-4 | 50% | 3.75A | 29.1W | 53g | 1.82 |
| 1104/5 6500kv | 2535-4 | 100% | 6.16A | 46W | 79g | 1.72 |
| 1104/5 6500kv 3S | 2535-2 | 50% | 4.52A | 52.8W | 81g | 1.53 |
| 1104/5 6500kv 3S | 2535-2 | 100% | 7.33A | 79.2W | 110g | 1.38 |
| 1104/5 6500kv 3S | 2535-4 | 50% | 5.98A | 65.4W | 89g | 1.36 |
| 1104/5 6500kv 3S | 2535-4 | 100% | 8.36A | 86.7W | 103g | 1.19 |
Same as with other motors 1104/5 6500kv motor was hot after spinning 4 blades props and efficiency was slightly lower.
Conclusion
Although I doubt that collected thrust data are 100% accurate and real numbers can be higher or lower, we can still see how efficiency changes depending on with which propeller different motors are used.
Smaller motors are getting hotter with bigger propellers or more blades and don’t offer better performance.
It seemed that four blades were always under-performing with selected motors, but probably it can be different with lower kv 1104/5 motor or bigger motor.
It worth to note that four blades always generated less noise. I’ve also heard that 4 blades can offer better agility. But everything comes with the price and it is a question of the proper balance.
So to conclude 2 blades setup seems to be able to offer longer flight time and more thrust with high kv micro motors for the price of more noise.
