A maximum-thrust figure is not enough to select a heavy-lift drone motor. The useful question is how much electrical power the complete motor, ESC and propeller combination needs at your aircraft's working thrust, and whether it can hold that point within its thermal and electrical limits.
For teams developing logistics and transport UAVs, this guide turns a supplier thrust table into a practical comparison worksheet. It separates measured results from estimates, explains the units that are often confused, and shows how to request the missing evidence before choosing a propulsion combination.
1. Define the aircraft operating point before opening the table
Start with all-up mass, not payload. Include the airframe, battery, cargo, avionics, landing gear, wiring and the propulsion components themselves. For a level aircraft with equal rotor loading, the initial hover estimate is:
Required thrust per rotor = all-up mass × gravitational acceleration / rotor count
An illustrative 18 kg, six-rotor aircraft needs approximately 29.4 N per rotor to balance its weight. That is 3.0 kgf, or 3,000 gf, per rotor under the equal-loading assumption. It is not a claim that a motor with a 3 kgf maximum rating is suitable. Climb, control authority, installation losses, uneven loading and the intended operating environment still need separate allowances and validation.
If the aircraft is tilted, the vertical component of thrust is smaller than total thrust. Coaxial rotors also cannot be treated as independent isolated propellers without installation-specific evidence. Use the simple calculation to locate the relevant part of the data, not to approve a flight design. Our heavy-lift thrust calculation guide provides the broader sizing context.
2. Check what was actually tested
A data sheet should describe a combination, not just a motor name. Two tables for the same motor can differ because of the propeller, ESC settings, voltage, cooling or measurement method. A supplier comparison is meaningful only when those conditions are visible.
| Record | What to request | Why it matters |
|---|---|---|
| Motor identity | Model, winding/KV version and sample identification | A different winding is a different comparison. |
| Propeller identity | Exact model, diameter, pitch, blade count and rotation direction | Nominal diameter alone does not define the load. |
| ESC configuration | Model, firmware, timing, switching settings and control signal | Electrical and commutation conditions affect the result. |
| Electrical measurement | Loaded voltage, DC input current and measurement location | A battery label does not establish voltage at the ESC. |
| Environment and installation | Temperature, pressure or altitude, mounting and airflow arrangement | Air conditions and nearby surfaces can change performance. |
| Test duration | Ramp rate, dwell time, warm-up and temperature history | A brief peak does not establish sustained capability. |
| Measurement quality | Sensor ranges, calibration date, zeroing and repeated runs | Small efficiency differences may be smaller than measurement uncertainty. |
Also distinguish measurements from predictions. APC explains that its published propeller performance files are generated using an analytical model based on propeller geometry. The UIUC Propeller Database publishes experimental propeller measurements. Both can be useful, but neither automatically supplies the electrical input or thermal limits of your complete motor and ESC assembly.
3. Keep thrust, electrical power and efficiency separate
Thrust is a force. When a table labels thrust in grams or kilograms, confirm whether it means gram-force or kilogram-force: 1 kgf is approximately 9.81 N. Do not combine a force in newtons with a mass in kilograms without the conversion.
For measurements made on the ESC's DC supply side, electrical input power is:
DC electrical input power (W) = loaded voltage (V) × DC current (A)
State the measurement boundary. A current sensor at the battery includes downstream wiring losses; a sensor beside one ESC represents a different boundary. Neither reading is the same as motor phase current. Tyto Robotics' explanation of motor power and efficiency discusses the distinction between electrical input and mechanical output, including the role of torque and rotational speed.
A table may call the following value "efficiency":
Thrust-to-electrical-power ratio (gf/W) = thrust (gf) / DC input power (W)
This is a useful hover comparison metric, not a dimensionless motor efficiency percentage. A value of 3 gf/W does not mean 300% efficiency. Mechanical motor efficiency requires shaft power as well as electrical input. Conventional forward-flight propulsive efficiency also involves airspeed; applying that definition at zero forward speed does not describe hover quality in the same way.
4. Compare combinations at equal thrust, not equal throttle
Suppose your initial target is 3,000 gf per rotor. The following numbers are invented solely to demonstrate the calculation. They are not TORGATEK product measurements, a supplier quotation or an approved operating limit.
| Illustrative combination | Thrust | Loaded voltage | DC current | Input power | Thrust/input power |
|---|---|---|---|---|---|
| A: lower measured point | 2,800 gf | 44.0 V | 18.0 A | 792 W | 3.54 gf/W |
| A: upper measured point | 3,200 gf | 44.0 V | 22.0 A | 968 W | 3.31 gf/W |
| A: local estimate at target | 3,000 gf | 44.0 V | 20.0 A | 880 W | 3.41 gf/W |
| B: direct measurement at target | 3,000 gf | 44.0 V | 21.0 A | 924 W | 3.25 gf/W |
For combination A, the target lies halfway between the two thrust points. Linear interpolation gives an estimated 20 A and 880 W. This is a local planning estimate between nearby points, not proof of a linear motor curve. Request a direct measurement at 3,000 gf before selecting the combination.
At that target, A appears to use 44 W less per rotor than B. Across six isolated units, the estimated difference is 264 W. However, A's result is interpolated and B's is measured. Repeatability, calibration, temperature and installation losses could narrow or reverse a small advantage. Compare the full evidence rather than declaring a winner from rounded numbers.
Equal throttle percentage is not an equivalent operating condition: different combinations can produce different thrust at the same command. Likewise, the best gf/W number at a very low thrust point may be irrelevant to an aircraft that must hover at a much higher load.
5. Convert the working point into an aircraft power estimate
Using the illustrative A result, six units require approximately 6 × 880 = 5,280 W at their defined measurement boundary. If avionics and other loads add 120 W, a first-pass total is 5,400 W. Add wiring and conversion losses only where they are not already included in the measurements; counting the same loss twice makes the estimate misleading.
This is still not a flight-time prediction. The installed aircraft may require more thrust because of its layout, airflow or attitude. A delivery mission also includes takeoff, transit, waiting, approach and landing. The companion guide to battery sag, energy reserve and cargo drone endurance shows how to build a mission-level budget rather than divide battery capacity by one bench current value.
6. Ask for the conditions where a promising result can fail
Lower operating voltage
A fresh-pack test does not show whether the unit can hold working thrust near the end of the usable discharge window. Ask for a thrust sweep at the lowest intended loaded voltage, within the battery, motor and ESC limits. Voltage alone cannot tell you the new operating point: current, speed, thrust and temperature must be recorded together.
Sustained operation
A current label without a duration and cooling condition is incomplete. Request a temperature-versus-time record at the intended working point and a separately defined short-duration high-load test. The allowable temperatures must come from the component specifications and the validation plan, not a universal value copied from another motor.
Installation effects
Record propeller clearance, support geometry and nearby structures. Check the installed assembly as well as the isolated unit. Treat coaxial overlap, restricted cooling and different mounting hardware as configuration changes that need evidence, not as small details already covered by a single-motor table.
7. Send a test request that a supplier can answer
When comparing multirotor motors or reviewing a heavy-lift motor product page, send the supplier one short operating-point sheet:
Aircraft all-up mass, rotor count, rotor layout and maximum propeller envelope.
Battery architecture and the expected loaded-voltage range, not only the cell count.
Working thrust per rotor, expected duration and separately specified transient requirements.
Ambient temperature range, operating altitude and installation/cooling arrangement.
Required report fields: thrust, RPM, loaded voltage, DC current, temperatures, dwell time and repeatability.
Ask which combinations have existing measured data and which require a new test. A product listing is a starting point for this discussion; it is not confirmation that the illustrative aircraft in this article matches that product.
Frequently asked questions
Can I use maximum thrust to calculate payload?
Not directly. Payload is only part of all-up mass, and a peak thrust result may have a limited duration. Establish working thrust, installation effects and the aircraft's required control and climb capability before assessing payload.
Is the motor with the highest gf/W always the best choice?
No. Compare gf/W at the required thrust, then consider mass, temperature, voltage range, physical fit and transient capability. A more efficient isolated combination can still be unsuitable for the complete aircraft.
Can static bench data predict cruise performance?
Static data help define a baseline. They do not establish the complete aircraft's forward-flight power, drag or rotor interaction. Use suitable aerodynamic data and installed-aircraft measurements for the mission you intend to fly.
Discuss your propulsion data with TORGATEK
Send your all-up mass, rotor layout, propeller limits, voltage range and target mission through the TORGATEK contact page. Request the available test conditions and operating-point data before treating any headline thrust value as a design decision.
Engineering note: All worked numbers above are illustrative. They are not measured performance, a flight authorization or a replacement for component limits and aircraft-level validation.
