A technical guide to designing axial flux motors. Learn about D3 torque scaling, YASA topology, and 10 kW/kg power density for custom EV and UAV builds.
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A technical guide to designing axial flux motors. Learn about D3 torque scaling, YASA topology, and 10 kW/kg power density for custom EV and UAV builds.
For a Tier-1 lead engineer or a technical founder, the "buy vs. build" dilemma is constant. The prospect of designing a custom axial flux motor in-house promises total control over the powertrain’s form factor and the ability to tune a torque curve specifically for a unique propeller pitch or transmission ratio.
However, moving from a 2D radial design to a 3D axial architecture introduces significant electromagnetic and mechanical complexities. At Beyond Motors, we champion engineering transparency. Whether you are prototyping a proof-of-concept or looking to integrate a professional-grade solution, this guide outlines the critical design pillars required to achieve 10 kW/kg power density and optimized electric propulsion.
The first step in designing for maximum efficiency is understanding that axial flux torque is not just about magnetic volume—it is about radius. In a radial motor, torque is proportional to the square of the diameter (D2). In our high-performance e-motors, torque is proportional to the cube of the diameter (D3).
To maximize torque density, you must minimize the mechanical air gap while maintaining structural integrity.
A "custom torque curve" is achieved by manipulating the Back-EMF (Electromotive Force) profile. If your mission profile requires high peak torque for takeoff (eVTOL) but high efficiency at cruise, the winding configuration is your primary lever.
At Beyond Motors, we utilize a Yokeless and Segmented Armature (YASA) topology to remove the "iron tax" of the stator yoke. This is the only proven method to reach the 30-40% higher torque density benchmarks required by 2026 industry standards.
The most common failure in "DIY" axial designs is the thermal trap. Because the stator is sandwiched between two rotors, heat has nowhere to go. An air-cooled axial motor will almost always hit a thermal ceiling before it reaches its electromagnetic potential.
The Engineering Requirement:
To maintain an efficiency island of >96%, you must implement active cooling. We have solved this via a patent-pending water cooling system that places the cooling interface in direct contact with the stator segments. Without this, your "custom torque curve" will suffer from severe thermal derating within 30 seconds of peak load.
If you are building your own, the greatest challenge is not the magnets—it is the axial attraction force. The magnetic pull between the rotor and stator can reach several kilonews.
Designing a motor from scratch takes years of R&D and millions in simulation software. The most efficient route for modern engineering teams is to use a modular, parametric platform.
Instead of reinventing the stator segment, you can customize specs, sizing, and project requirements using our existing, flight-proven architecture. This allows you to focus on the vehicle-level integration while we handle the 10 kW/kg electromagnetic backbone.
A DIY approach is excellent for learning, but for high-stakes electric propulsion, precision is non-negotiable. If you have specific torque and RPM targets, we invite you to bypass the R&D "valley of death."
Use the Beyond Motors Configurator to input your desired torque curve and receive a personalized data sheet for your powertrain.
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