Can Normal DC Motors Replace Brushless Motors in RC Planes?

When it comes to equipping RC planes with motors, one of the primary choices faced by hobbyists is whether to use a normal brushed DC motor or a brushless motor. At first glance, normal DC motors might seem like a cost-effective and accessible alternative. However, there are several factors to consider, particularly when aiming to achieve performance parity with a 500KV brushless motor.

Understanding Brushless Motor Specifications

KV Rating: The KV (kilovolt) rating is a critical specification for brushless motors. A 500KV brushless motor, for example, indicates that the motor will rotate 500 times per minute (RPM) for each volt applied. This rating is crucial in understanding the motor's performance, especially in terms of the speed it can achieve under different voltage inputs.

Voltage: Brushless motors are typically designed to operate at higher voltage levels. For instance, a 3S LiPo battery, which provides approximately 11.1V, is a standard voltage for brushless motors. The relationship between voltage and RPM for a 500KV brushless motor can be calculated using the simple formula:

RPM KV × Voltage

For example, if a 3S LiPo battery is used, the calculation would be as follows:

RPM 500 × 11.1V 5550 RPM

Matching with a Brushed Motor

Matching the performance of a brushed DC motor to that of a 500KV brushless motor requires careful consideration of both voltage and RPM.

Voltage Consideration

Ensure that the voltage used with a brushed DC motor is similar to what would be used for the brushless motor. In the case of a 3S LiPo battery, a voltage of 11.1V is a good starting point.

RPM Consideration

To achieve a similar RPM, look for a brushed motor that can spin at around 5550 RPM at the chosen 11.1V. This might require selecting a brushed motor with a higher RPM rating, as brushed motors generally have lower efficiency and might not perform as well under load.

Additional Considerations

Several factors beyond voltage and RPM must be taken into account when replacing brushless motors with brushed ones:

Torque and Power Output

Ensure that the brushed motor can handle the power requirements of your RC plane. Brushless motors typically offer higher torque and power output, which might be a limiting factor when using brushed alternatives.

Weight and Size

Brushed motors are often heavier and larger compared to brushless motors. This could affect the overall weight and design of your RC plane, potentially impacting its flight characteristics.

Heat and Maintenance

Brushed motors generate more heat and may require more maintenance, such as brush replacement, compared to brushless motors.

Conclusion

While it is possible to use brushed DC motors in RC planes, achieving performance comparable to a 500KV brushless motor requires careful selection of voltage and RPM specifications, alongside consideration of the motor's overall performance characteristics. Careful planning and testing will be necessary to ensure that the chosen brushed motor performs optimally in your RC plane.