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At Munro & Associates, we’re always on the lookout for engineering breakthroughs that reshape how we think about vehicle design and performance. One of the most buzzworthy developments in the EV world right now is axial flux motor technology. These compact, high-torque electric motors are being championed as the next leap forward in EV powertrain design. To see what the hype is about, our team tore down an axial flux motor from Omni Powertrains, a Shanghai-based company focused on custom motors for specialized applications like motorsports and industrial equipment.
In this detailed analysis, we explore how axial flux motors compare to traditional radial flux motors, why they’re exciting for niche applications, and what trade-offs engineers need to consider when evaluating this tech.
What Makes Axial Flux Motors Different?
Every electric motor consists of two fundamental components: the stator (stationary) and the rotor (rotating). In radial flux motors—the dominant type used in most EVs today—magnetic flux travels radially, moving from the center of the rotor outward into the stator and back. In contrast, axial flux motors operate differently: the magnetic flux moves along the motor’s axis, flowing axially between flat rotor discs and stator plates.
This design allows the torque-generating surface area to be spread across a wider diameter, potentially delivering higher torque density for a given volume. In theory, this could mean smaller, lighter motors that produce equivalent or greater output than radial flux counterparts.
Munro’s Teardown: Inside an Omni Axial Flux Motor
The motor we analyzed was part of a dual-motor assembly mounted to a transmission. We disassembled one of the two motors to examine its internal design.
Cooling System
The motor uses a water-cooling system with serpentine channels that wrap around the stator housing. A key feature is that coolant never touches the windings directly, which minimizes the risk of electrical failure if a leak occurs. The consistent temperature distribution ensures uniform winding cooling, preventing hot spots that could degrade motor efficiency or lifespan.
Resolver and Electrical Architecture
A resolver tracks the precise position of the rotor’s permanent magnets—critical for timing the motor’s electronic commutation. Electrical connections for the three-phase power supply are housed in a module that could be mistaken for an inverter due to its size, though it’s actually just a robust terminal connection system.
Static Charge Management and Durability Features
The teardown revealed thoughtful touches that enhance motor reliability, especially for high-performance environments. A carbon brush assembly discharges static electricity generated by the spinning plastic rotor, preventing bearing pitting and wear from arcing.
The Munro team also noted the use of threaded fasteners, a detail we often critique due to potential loosening over time or during service. While acceptable for a low-volume, custom unit, there’s room to optimize fastener strategies for mass production.
Key Engineering Differences: Axial vs Radial Flux
To contextualize this teardown, we compared the Omni motor with a radial flux unit from the Chevy Bolt—nearly identical in voltage, power, and torque.
| Feature | Axial Flux Motor | Radial Flux Motor |
|---|---|---|
| Flux Path | Axial (across flat face) | Radial (center outwards) |
| Rotor Shape | Thin disc | Long cylinder |
| Torque Surface Area | Wider (for same volume) | Narrower |
| Cooling Access | Dual-sided | Usually one-sided |
| Structural Loads | Higher axial stress | Balanced radial/axial |
| Complexity | Precision alignment needed | Easier to manufacture |
Although axial flux motors offer a higher torque surface area, the mechanical challenges are significant. Strong axial forces from the magnets require robust bearings and perfectly aligned air gaps. Even small misalignments can lead to excessive wear or rotor instability.
To manage these stresses, the Omni motor uses a carbon fiber retaining ring to secure magnets against centrifugal forces. Without this, magnets could detach during high-speed operation—posing a serious failure risk.
Manufacturing and Cost Considerations
What really sets this motor apart isn’t just the design—it’s the manufacturing approach, which perfectly suits Omni’s low-volume, high-performance market niche.
Traditional stators use stamped laminations formed in large presses, requiring expensive dies and tooling. In contrast, Omni’s stator is fabricated from a strip of notched steel wound like a slinky. The notching process uses a relatively low-cost, $10,000 machine—more like an industrial sewing machine than a traditional press. This approach allows for rapid prototyping and custom designs without massive capital outlays.
The resulting stator has 36 straight slots, ideal for simply dropping in windings. This contrasts with hairpin-wound radial motors that require complex assembly and welding. The winding simplicity keeps costs low and manufacturing flexible—ideal for motorsport builds where only a handful of vehicles may be produced.
Performance Reality vs Potential
Despite the axial flux motor’s design potential, Munro’s performance analysis showed that its actual torque and power density were comparable to existing radial flux motors—rather than exceeding them.
Currently, Lucid’s radial flux motor still leads the industry in both metrics, largely due to aggressive engineering optimization and tight tolerances.
So why choose axial flux? It’s not about mass-market EVs—yet. It’s about tailoring performance and cost efficiency for niche applications, where customizability and compact form factors matter more than marginal efficiency gains.
Where Axial Flux Shines
Axial flux motors excel in:
- Motorsports, where packaging constraints, cooling demands, and high torque matter
- Specialty machinery or robotics with unique mounting or power needs
- Short-run production where flexible, low-cost stator manufacturing is a game changer
Their lower capital cost for tooling, paired with adequate performance and cooling, makes them ideal for custom EV applications.
Conclusion: Engineering Insight Meets Application Fit
Axial flux motors offer clear advantages in form factor, cooling efficiency, and torque surface area. But real-world deployment reveals that mechanical complexity and precise assembly limit their adoption in mass-market EVs—at least for now.
Still, Omni Powertrains’ approach demonstrates how lean design, smart tooling, and targeted engineering can unlock impressive value. For manufacturers aiming to serve motorsports or other low-volume, high-performance applications, axial flux motors may be the perfect fit.
At Munro, we’ll keep watching this space—and tearing down what’s next.
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