Light Weight Axial Flux Motors for Long-Flight UAV Drones

The endurance of a battery-powered drone is governed by a simple energy balance: the energy stored in the battery divided by the power consumed in flight. Reducing the weight of the propulsion system directly lowers the power needed to maintain altitude, extending flight time without increasing battery capacity.

Axial flux permanent magnet motors offer the best power-to-weight and torque-to-weight ratios of any brushless motor topology. Where a comparable radial flux motor's active parts might weigh 400–600 g, the active parts of our pancake-style axial flux motors deliver equivalent torque at 150–250 g — a weight saving that feeds directly into additional minutes of flight or payload capacity for mission equipment. See our article on why we need lighter electric motors for the physics behind this compounding effect.

Weight is the Dominant Variable in Drone Endurance

A multirotor UAV spends the majority of its flight energy simply hovering — counteracting gravity. The power required to hover scales roughly with the square root of the disc loading (thrust per unit rotor area), which means that any weight reduction has a compounding benefit: less thrust needed means smaller motors spinning more slowly, which in turn improves propeller efficiency and further reduces power draw.

In fixed-wing UAVs the relationship is equally direct: a lighter airframe requires a smaller wing area and less engine thrust to sustain level flight, enabling either a longer mission range on the same battery or a heavier sensor payload within the same total take-off weight budget.

The motor system — including the motor, mount, and associated wiring — typically accounts for 15–25% of the total dry weight of a small UAV. Switching from a conventional radial flux motor to an axial flux design at the same power rating routinely cuts this subsystem weight by 40–60%, making it one of the highest-leverage improvements available to UAV designers.

Coreless Design Eliminates Electromagnetic Interference

Conventional brushless motors — both radial and many axial flux designs — use a laminated iron stator core. While this core increases torque density, it also generates alternating magnetic flux and associated electromagnetic noise across a broad frequency spectrum as the motor rotates. This interference can degrade GPS signal lock, corrupt thermal camera imagery, introduce noise into IMU sensors, and disrupt 433 MHz or 5.8 GHz video downlinks.

Our coreless axial flux motors have no iron in the stator. The windings are embedded directly in an epoxy disc between the two rotor magnets. Without a ferromagnetic core there is no cogging torque, no core hysteresis loss, and — critically for surveillance and inspection UAVs — no stray magnetic field emanating from the stator. The rotating permanent magnets produce a contained axial field that attenuates rapidly with distance, so electronics even a few centimetres from the motor are effectively in a magnetically quiet environment.

This matters in practice: thermal infrared cameras use microbolometer detector arrays that are sensitive to electromagnetic disturbances during integration. GPS receivers in the 1575 MHz L1 band and 1227 MHz L2 band operate at received signal strengths of around −130 dBm — well within the noise floor that a conventional motor can generate at close range. With coreless axial flux motors, shielding can be reduced or eliminated entirely, saving additional weight and simplifying the airframe design.

Efficiency Advantage at Partial Load

Most UAV missions involve sustained cruise rather than maximum-thrust bursts. At partial load — the typical operating point during level flight or station-keeping — coreless motors have a decisive efficiency advantage over iron-core designs because they have no core losses. Core losses (hysteresis and eddy current losses) are proportional to motor speed and are present regardless of load, meaning they are disproportionately costly at low throttle settings.

Our motors reach peak efficiency above 93% and sustain over 90% efficiency across a wide torque band. For a UAV consuming 200 W in cruise, the difference between 85% and 93% motor efficiency translates to 16 W less heat and 16 W more thrust — equivalent to carrying an additional 80 g of battery.

Thermal Imaging and Live Video Applications

Long-endurance UAVs equipped with FLIR-type thermal cameras are used for infrastructure inspection, search and rescue, border surveillance, precision agriculture, and wildfire monitoring. In all of these roles, the quality of the thermal image directly determines mission success. Sensor noise caused by propulsion EMI degrades the minimum detectable temperature difference (NETD) of the camera, reducing the range at which targets can be detected.

Live video streaming adds a further RF consideration: the drone's video transmitter, operating at 5.8 GHz, shares a congested radio environment with WiFi networks and other ISM-band devices. Interference generated by the motor drive system can raise the noise floor of the receiver, reducing effective link range and image quality. With coreless axial flux motors, the motor itself contributes negligible RF noise, placing the entire link budget back in the hands of the antenna and transmitter design.

Axial Flux Motor Design for UAV Integration

Our motors are designed from the outset for direct propeller mounting. The flat disc geometry matches the natural form factor of a propeller hub, minimising the frontal area contribution to drag. The motor can be mounted directly on a carbon fibre boom with the propeller on the front face — no separate shaft, coupling, or nose cone required.

The motor's low profile also means the centre of thrust is close to the mounting surface, reducing the bending moment on the arm under load — an advantage in carbon fibre structures where fatigue from cyclic bending is a common failure mode.

Because there is no cogging torque in a coreless motor, the propeller can be started from any angular position without the jerking that causes mechanical stress in conventional motors. This extends propeller and motor bearing life in applications with frequent start–stop cycles, such as delivery drones or inspection platforms that hover at a fixed point between transit legs.

Scalable from Micro to Medium UAV Classes

The axial flux topology scales favourably across the power range relevant to commercial UAVs. Our current motor family spans from compact units producing 50 W continuous power for lightweight surveillance platforms, up to 2 kW motors suitable for medium-class cargo drones carrying 5–10 kg payloads over distances of 50 km or more.

All motors in the family share the same coreless stator architecture, so the weight and EMI advantages described above apply uniformly across the range. Whether the application calls for a lightweight reconnaissance platform or a heavy-lift inspection drone, the same fundamental design principles deliver longer endurance and cleaner sensor data. The Turncircles motor configurator lets you specify your required thrust, operating voltage, and target weight — and returns a simulation-validated motor specification within minutes.