So, what is a brushless motor? At its core, it is a highly efficient, digitally controlled electric motor that eliminates mechanical friction to deliver higher efficiency, longer lifespan, and more reliable performance.
When browsing RC forums, power tool reviews, or electric vehicle (EV) discussions, users consistently ask: Why is it faster, more expensive, and does it actually last longer? The answer to all these questions lies in this fundamental engineering shift.
This definitive guide is built to answer those questions. Are you an absolute beginner upgrading an RC crawler? A contractor investing in reliable cordless tools? Or an engineering student mastering complex electronic commutation? We have you covered.
In this comprehensive breakdown, we will explore the exact internal mechanics, compare them directly against traditional brushed motors, and provide a strict engineering-grade ROI purchasing model. This guide focuses on real engineering principles rather than marketing claims.
Key Takeaways
- The End of Mechanical Friction: A brushless DC (BLDC) motor entirely replaces physical carbon brushes and mechanical commutators with an Electronic Speed Controller (ESC) to achieve precise electronic commutation.
- Unmatched Efficiency & Lifespan: By eliminating brush-contact friction, BLDC motors typically achieve 85%–93% efficiency (up to 90%+ in optimized systems). Their lifespan easily exceeds 10,000 hours, limited almost exclusively by the physical wear of their mechanical bearings.
- The ESC is Mandatory: A brushless motor cannot run by simply connecting it to a battery. The ESC acts as the motor’s brain, converting DC power into a timed three-phase signal to drive the stator coils.
- Higher Upfront Cost, Lower TCO: While sophisticated control electronics increase the initial purchase price, the massive leap in performance, heat management, and battery runtime yields a lower long-term cost (Total Cost of Ownership, TCO) for high-demand applications like EVs, heavy-lift drones, and professional power tools.
What Is a Brushless DC Motor?
A brushless DC (BLDC) motor is an electronically commutated motor that replaces carbon brushes with an Electronic Speed Controller (ESC). This eliminates mechanical friction and electrical arcing. While powered by direct current (DC), the ESC acts as the motor’s brain, generating a precisely timed three-phase AC-like waveform to drive the stator’s electromagnets. This is why brushless motors use three wires instead of two. Because electronic commutation eliminates brush wear, mechanical bearings become the only physical upkeep required.
To see why this matters, here is how motor technology evolved:
The Historical Evolution of Electric Motors
Era |
Dominant Motor Type |
Biggest Problem |
Industry Shift |
1900s |
Brushed DC Motors |
Brush wear, mechanical friction, and sparking |
Cheap and simple to manufacture, but required heavy maintenance. |
1980s |
Early Brushless DC |
Prohibitively expensive solid-state electronics |
Limited adoption in highly specialized engineering fields. |
2000s+ |
Modern Brushless DC |
ESC controller costs drastically reduced |
Eliminating friction became the standard. Now dominates EVs, drones, and power tools. |
How Does a Brushless Motor Work?
A brushless motor works by using an Electronic Speed Controller (ESC) to perform precise electronic commutation, rapidly switching the electromagnets in the stationary stator to create a rotating magnetic field that forces the permanent magnets on the central rotor to spin continuously without mechanical friction. Often described as an “inside-out” architecture, this process operates exactly like a dog race where the rotor’s magnets constantly chase a shifting magnetic field they can never catch.
To prevent the rotor from locking into place and to maintain continuous rotational motion, the Electronic Speed Controller (ESC) must know the exact physical position of the rotor’s magnets. It achieves this position tracking by using either built-in Hall-effect sensors (which detect magnetic fields) or by analyzing the natural “back-EMF” (voltage) generated by the spinning coils. In sensorless systems, the ESC interprets these voltage signals as a rotor-position map, allowing it to know exactly when to fire the next coil without needing extra hardware.
Once the position is tracked, the motor executes a rapid, continuous sequence. This 6-step process is the standard way to drive three-phase brushless motors. To truly understand how do brushless motors work, we must look at this exact electronic commutation process.
The 6-Step Rotation Sequence (3-Phase Motor)
Step | Activated Coils | Magnetic Interaction & Rotor Reaction |
1 | Coil A (+) Coil B (-) | The stator creates a magnetic field; the rotor aligns itself to this initial field. |
2 | Coil A (+) Coil C (-) | The controller quickly switches power; the magnetic field shifts forward, pulling the rotor. |
3 | Coil B (+) Coil C (-) | The rotor continues its spin, chasing the newly energized electromagnets. |
4 | Coil B (+) Coil A (-) | Polarity reverses for Coil A; the “mechanical rabbit” moves further ahead. |
5 | Coil C (+) Coil A (-) | Magnetic attraction and repulsion keep the rotor spinning continuously. |
6 | Coil C (+) Coil B (-) | The final step completes the electrical cycle before instantly repeating Step 1. |
By repeating this precise sequence thousands of times per minute, the ESC maintains a constantly rotating magnetic field, forcing the permanent magnets on the rotor to spin with incredible efficiency and zero physical friction. While this electronic commutation is extremely efficient, the discrete pulsing can create a slight vibration at very low speeds, known as cogging torque.
What Are the Main Components of a Brushless Motor?
The main components of a brushless DC motor are the stator, the rotor, Hall-effect sensors, and mechanical bearings, all orchestrated by an Electronic Speed Controller (ESC). To understand exactly how this internal architecture eliminates physical friction to generate massive power, let’s examine the specific role of each part:.
- The Stator: This is the stationary component that houses the electromagnets, typically consisting of copper coils arranged in a three-phase setup. When the ESC passes current through these coils, they generate a precisely timed, rotating magnetic field.
- The Rotor (Inrunner vs. Outrunner): The rotor is the moving component equipped with powerful permanent magnets (such as neodymium). When evaluating the stator vs rotor brushless dynamic, their physical arrangement dictates performance. In an Inrunner motor, the rotor spins inside the stator, producing extremely high rotational speeds (RPM) ideal for RC racing cars. Conversely, in an Outrunner motor, the rotor spins outside the stator like an overhanging bell, generating massive low-end torque favored by heavy drones and electric bikes.
- Hall-effect Sensors: While the ESC acts as the brain, it relies entirely on these crucial feedback sensors. Typically mounted on the stator, Hall-effect sensors physically detect the exact position and magnetic polarity of the rotor’s permanent magnets as they spin past. They instantly feed this real-time location data back to the ESC, allowing it to trigger the next electromagnetic pulse flawlessly. (Note: “Sensorless” motors calculate this position indirectly by measuring electrical back-EMF).
- Mechanical Bearings: These high-precision components support the rotor, allowing it to spin smoothly and quietly within or around the stator with minimal physical friction.
Together, these four physical components form the mechanical foundation, but they rely entirely on the external brain – the ESC – to orchestrate the precise electrical timing and current needed to bring the entire system to life.
What Is an ESC in a Brushless Motor?
An Electronic Speed Controller (ESC) is the essential “brain” of a brushless motor system that converts direct current (DC) into a precisely timed three-phase drive current to act as an electronic commutator. Because BLDC motors lack physical brushes, they absolutely cannot run without an ESC. Without this crucial controller, the motor cannot spin and is essentially just a dead weight of magnets and copper wire.
The ESC functions by taking steady direct current (DC) from your battery and, rather than outputting traditional AC, it uses Pulse Width Modulation (PWM) or Space Vector PWM (SVPWM) to generate a precisely timed three-phase drive current (either 6-step or sinusoidal) to power the electromagnets.
To time the magnetic attraction perfectly, the ESC must track the exact physical position of the rotor. It achieves this through physical Hall-effect sensors, high-precision encoders/resolvers (in high-end systems), or by measuring electrical back-EMF feedback (Sensorless). It is worth noting that sensorless systems often struggle with stuttering during low-speed startups because back-EMF requires physical motion to generate a readable signal. Additionally, while many consumer-grade or RC ESCs feature a built-in Battery Eliminator Circuit (BEC) to safely power receivers and servos, high-power or industrial ESCs typically do not include them.
To truly understand what is ESC technology, we must look at how it electronically drives the motor using two primary algorithms:
Brushless ESC Commutation Algorithms Compared
Drive Algorithm | Commutation Method | Pros & Typical Applications | Drawbacks |
Trapezoidal (120-Degree) | Block commutation (abrupt phase switching via PWM). | Simple and highly affordable. Widely used in basic RC bashers, entry-level drones, and simple power tools. | Creates “torque ripple” (slight vibrations) and acoustic noise, especially at low speeds. |
FOC / Sine Wave (180-Degree) | Continuous sinusoidal current shifting (often via SVPWM). | Incredibly smooth, high efficiency, and no torque ripple. Standard for EVs, advanced robotics, e-bikes, and camera gimbals. | Historically required expensive processors, but modern, affordable MCUs (like STM32) have drastically lowered the cost barrier today. |
Whether you rely on an affordable trapezoidal setup or a sophisticated FOC processor, this electronic brain is what replaces physical friction with smart software, unlocking the motor’s true potential.
What Is the Difference Between Brushed and Brushless Motors?
The fundamental difference between brushed and brushless motors is that brushed motors use physical carbon brushes for mechanical commutation, whereas brushless motors eliminate physical friction entirely by relying on an Electronic Speed Controller (ESC) for precise electronic commutation. To truly resolve the brushed vs brushless motor debate beyond simple claims that one is “better,” we must compare their engineering parameters directly across 12 critical dimensions:
The Ultimate Brushed vs. Brushless DC Motor Comparison
Feature | Brushed Motor | Brushless Motor (BLDC) |
Commutation Method | Mechanical (Carbon brushes & commutator) | Electronic (ESC and position sensors) |
Wiring Complexity | Simple (2 wires: Positive & Negative) | Complex (3 phase wires + optional sensor cables) |
Energy Efficiency | 75% – 80% (Energy lost to mechanical friction) | 85% – 93% (Up to 95% in high-end theoretical models) |
Expected Lifespan | 1,000 – 8,000 hours (Limited by brush wear) | Tens of thousands of hours (Limited only by bearings) |
Maintenance Needs | High (Requires periodic brush replacements) | Minimal (Essentially maintenance-free) |
Waterproofing | Can run submerged briefly (though it accelerates wear) | Motor is waterproof, but the ESC and sensors are highly vulnerable to water |
Electrical Noise (EMI) | High (Continuous sparking at contacts) | Low (No physical sliding contacts or arcing) |
Low-Speed Control | Excellent (Naturally smooth for RC rock crawling) | Prone to “cogging” without sensors; Sensored/FOC setups resolve this |
Heat Generation | High (Due to internal friction and arcing) | Low (Coils on the stator allow easy cooling) |
Top Speed (RPM) | Limited (Brushes bounce/arc at high speeds) | Extremely high (No physical friction limits) |
Cost & TCO | Very affordable upfront | 40-60% higher initial cost, but lower long-term TCO (pays off in 12-18 months) |
Best Applications | Cheap toys, display units, single-use applications | EVs, drones, advanced robotics, high-end power tools |
While brushless technology represents the modern standard for high-performance applications, brushed motors are not entirely obsolete. As avid RC enthusiasts frequently highlight, traditional brushed motors still provide naturally superior low-speed torque out of the box, making them popular for specialized hobbies like rock crawling.
However, for electric vehicles, drones, and professional robotics that demand sustained high RPMs, the choice is clear. The 40% to 60% higher upfront cost of a brushless system is rapidly offset by its superior 85% to 93% efficiency and massive lifespan, yielding a much lower total cost of ownership (TCO) over its operational life.
Are Brushless Motors AC or DC?
A brushless DC (BLDC) motor is powered by direct current (DC) externally, but it operates using alternating current (AC) internally because the Electronic Speed Controller (ESC) inverts the DC input into a precisely timed, three-phase AC-like waveform. To truly settle the debate over this dual nature, we must explicitly separate the external power source from the internal mechanics.
So, is BLDC actually AC internally? Yes. Its internal physical operation is highly similar to a permanent magnet AC synchronous motor. In engineering, naming depends on the waveform: standard BLDCs rely on an AC-like trapezoidal waveform, whereas Permanent Magnet Synchronous Motors (PMSM) utilize a pure sinusoidal waveform.
Feature |
Brushless DC (BLDC) |
Traditional AC Motor |
Input Power Source |
DC (Battery or DC power supply) |
AC (Wall outlet or electrical grid) |
Commutation Method |
Electronic (ESC via PWM) |
Grid frequency / Line frequency |
Waveform Type |
Trapezoidal (PMSM uses Sinusoidal) |
Pure Sinusoidal |
Internal Operation |
Synchronous AC-like magnetic field |
Synchronous or Asynchronous |
What Are the Advantages and Disadvantages of Brushless Motors?
The primary advantages of brushless motors are their 85% to 93% electrical efficiency and 10,000+ hour lifespan, while their main disadvantages include high initial costs and dependency on complex Electronic Speed Controllers (ESCs). To provide an objective analysis beyond basic marketing claims, we must examine both sides of these real-world engineering constraints:
The Advantages (Why Are Brushless Motors Better?)
Unmatched Efficiency & Power-to-Weight Ratio: Brushless motors typically achieve 85% to 93% electrical efficiency, compared to just 75-80% for brushed alternatives. By eliminating mechanical friction, they deliver an exceptional power-to-weight ratio, allowing lightweight devices like drones and EVs to generate massive thrust and torque, significantly extending battery range and run time, especially when paired with the high energy density of lithium ion battery packs.
- 10,000+ Hours of Lifespan: Without physical carbon brushes rubbing and wearing down, the motor’s lifespan is theoretically limited only by the mechanical bearings, easily surpassing 10,000 hours of continuous operation.
- Zero Sparking (Hazard-Safe): The elimination of mechanical commutators means there is absolutely no electrical arcing. This makes brushless motors inherently safer for industrial operations in highly flammable or explosive environments, though full system-level ATEX/IECEx certification is still required for true explosion-proof compliance.
The Disadvantages (Brushless Motor Cons)
- Low-Speed Stuttering & Control Complexity: Sensorless brushless motors rely on electrical back-EMF to track the rotor, which requires existing rotational motion to generate a readable signal. As a result, they often struggle with harsh startup stuttering (often conflated with magnetic ‘cogging’). While more expensive sensored setups (Hall-effect) or advanced FOC (Field Oriented Control) combined with observer algorithms can resolve most of these issues, they significantly increase engineering complexity.
- High ESC Dependency and Cost: A brushless motor is completely non-functional without a complex Electronic Speed Controller (ESC). Adding this sophisticated circuitry, alongside rare-earth magnets, significantly increases the initial upfront cost.
- Complex Troubleshooting: When a brushed motor dies, you often simply replace the brushes. When a brushless system fails, pinpointing the exact issue – whether it is a blown MOSFET in the ESC, a faulty position sensor, a burnt stator winding, or even software-related firmware glitches – requires advanced diagnostic tools and engineering knowledge.
What Is the KV Rating of a Brushless Motor?
The KV rating of a brushless motor represents its velocity constant, indicating the exact theoretical RPM (revolutions per minute) the motor will spin per one volt of electricity under no-load conditions.
Because KV is strictly inversely proportional to the motor’s torque constant (Kt), a higher KV does not equal more power; instead, it dictates a strict engineering trade-off between maximum top-end speed and low-end pulling torque. To master the high KV vs. low KV debate, we must evaluate this trade-off across real-world setups:
Specification |
High KV Motor (e.g., 3500+ KV) |
Low KV Motor (e.g., 500 – 2500 KV) |
Performance Profile |
Maximum top-end speed, lower natural low-end torque. |
Slower top speed, massive low-end pulling torque. |
Current & Heat |
Can draw more amps; prone to generating more heat if improperly geared. |
Often easier to maintain high efficiency and run cooler under heavy loads. |
Ideal Setup |
Smaller pinions or propellers. Due to a lower Kt, reducing the physical load is mandatory to prevent overcurrent. |
Larger gear ratios or heavy-duty drone propellers. |
Best Applications |
RC racing cars, sport EDF jets, speed-run drones. |
RC rock crawlers, heavy-lift drones, robotics. |
Swapping to a higher KV motor without reducing battery voltage or gear ratios will overwork the stator coils. Ultimately, KV ≠ Power Rating. A tiny motor and a massive motor can share the exact same KV, but their maximum power capacities differ vastly. Always evaluate KV alongside the physical stator size (e.g., 2205 vs. 3650).
Where Are Brushless Motors Used?
Brushless motors are predominantly used in electric vehicles (EVs), industrial robotics, drones, and cordless power tools due to their extreme power-to-weight ratio and thermal efficiency. To understand exactly why these specific industries demand this technology, we must examine the ultimate brushless application matrix:
Industry |
Primary Reason |
Specific Example |
EVs & E-Motorcycles |
Torque density & thermal efficiency. |
Electric motorcycles, EV traction. |
Industrial Robotics |
Millimeter-level precision control. |
CNC machines, assembly arms. |
Drones & RC Vehicles |
Extreme power-to-weight ratio. |
Heavy-lift UAVs, RC racing. |
Cordless Power Tools |
Eliminates brush friction, maximum battery life. |
Professional drills, impact saws. |
- EVs & E-Motorcycles: Modern electric mobility relies on brushless technology to maximize commuting range, establishing the BLDC as the gold standard for an electric motorcycle motor when paired with high-density NMC or LiFePO4 batteries. While basic BLDCs power e-bikes, high-end EVs often use PMSM (Permanent Magnet Synchronous Motors) for smoother sine-wave control. (Note: Regenerative braking is not inherent to all BLDC systems; it requires a specialized bidirectional ESC, which is a crucial system concept to grasp when exploring how does electric motorbike work).
- Industrial Automation & Robotics: In manufacturing, brushless servomotors paired with high-resolution encoders deliver millimeter-level positional accuracy and reliable holding torque at zero RPM.
- Drones & Power Tools: Eliminating mechanical brushes maximizes the thrust-to-weight ratio for aggressive drone maneuvers, while drastically extending battery runtimes for cordless power tools.
How to Choose the Right Brushless Motor?
Choosing the right brushless motor requires a strict engineering evaluation of four critical parameters: the target load, system voltage, KV rating, and ESC amperage capacity. To guarantee optimal performance and prevent catastrophic electronic failure, bypass generic size-matching advice and follow this sequential 4-step selection funnel:
Choosing the right brushless motor requires a strict engineering evaluation of four critical parameters: the target load, system voltage, KV rating, and ESC amperage capacity. To guarantee optimal performance and prevent catastrophic electronic failure, bypass generic size-matching advice and follow this sequential 4-step selection funnel:
The 4-Step Engineering Selection Funnel
- Step 1: Define Target Load: Assess the physical weight and application. Are you pushing a heavy 1/8 scale RC basher or lifting a lightweight FPV racing drone?
- Step 2: Determine System Voltage: Select your power source (e.g., 3S, 4S, or 6S LiPo batteries). Higher voltage setups generally run more efficiently by pulling fewer amps to generate the same wattage.
- Step 3: Select the KV Rating: Match the KV to your chosen voltage and load. Use low KV for massive torque (heavy propellers/large pinions) and high KV for top-end speed.
- Step 4: Match ESC Amperage: Always select an Electronic Speed Controller (ESC) rated for 20–30% more continuous current (amps) than your motor’s peak draw to prevent catastrophic thermal failure.
ROI Purchasing Model: Is the Upgrade Worth It?
Before investing, evaluate your total cost of ownership (TCO) and specific use case:
Buying Decision |
When It Makes Financial Sense |
Buy Cheaper Brushed |
You are on a strict budget, an absolute beginner, need a power tool for rare weekend repairs, or specifically require naturally smooth low-speed RC rock crawling. |
Upgrade to Brushless |
You are a daily professional contractor, an RC enthusiast chasing 50mph+ top speeds, or building heavy-lift drones where maximizing battery runtime is mandatory. |
By adhering to this engineering logic, you eliminate guesswork, ensuring maximum performance, safety, and a guaranteed return on your investment.
How Long Do Brushless Motors Last and How to Maintain Them?
High-quality brushless motors typically last for 10,000 to 30,000 continuous hours because their physical lifespan is limited almost exclusively by mechanical bearing wear (L10 life) rather than brush friction. However, to achieve this massive longevity and protect the Electronic Speed Controller (ESC) from thermal stress, you must follow this 3-step engineering-grade preventative maintenance checklist:
Maintenance Step |
Action Required |
Why It Prevents Failure |
1. Environmental Cleaning |
Use compressed air for dust. For metal shavings stuck to powerful neodymium magnets, use masking tape/putty or partially disassemble the motor. |
Debris scratches magnets and traps heat, which destroys electrical efficiency. |
2. Bearing Inspection |
Spin the shaft manually. If it feels gritty, replace the bearings immediately. Avoid adding external lubricants to sealed bearings, as this attracts dirt. |
Seized bearings instantly spike electrical current, frying the stator windings. |
3. ESC & Thermal Check |
Inspect ESC cooling vents and phase wires for melted connectors or solder joint cracks caused by repeated thermal cycling. |
A damaged ESC or loose wire causes dangerous desynchronization (stuttering), burning the motor. |
The Future of Brushless Motors
Brushless motors are definitively replacing brushed motors across all industrial sectors, with the future of BLDC technology driving entirely new frontiers in AI robotics, eVTOL aviation, and solid-state GaN controllers. To understand why this electronically commutated architecture has become the absolute industrial default, we must look beyond simple power tools to see how next-generation systems are actively pushing the limits of modern engineering.
Today, ultra-compact, high-torque systems serve as the foundational humanoid actuators driving advanced AI robotics. Similarly, the rapid rise of eVTOL aviation relies entirely on the extreme thrust-to-weight ratios that only advanced brushless propulsion can safely deliver.
These frontier applications are continuously accelerated by breakthroughs in control electronics, specifically the transition to solid-state motor controllers utilizing wide-bandgap (SiC and GaN) semiconductors. Although GaN ESCs offer superior efficiency, their widespread adoption still depends on continued cost reduction and manufacturing scalability. Furthermore, as FOC control becomes universal, the line between BLDC and PMSM continues to blur, with most next-generation systems effectively operating as high-precision PMSM drives.
However, the ultimate engineering hurdle remains material dependency. To sustain this incredible growth, the industry must overcome supply chain challenges associated with rare-earth magnets (like Neodymium), driving massive investments into rare-earth recycling breakthroughs and sustainable magnetic alternatives.
Conclusion: The Final Verdict on Brushless Technology
Ultimately, the answer to the core questions we asked at the very beginning – why is it faster, why is it noticeably more expensive, and do they actually last longer? – comes down to one fundamental engineering triumph: replacing physical mechanical friction with intelligent electronic commutation.
Whether you are a contractor relying on cordless tools for daily heavy-duty tasks, an RC enthusiast pushing the limits of speed, or an engineering student analyzing the shift toward solid-state ESCs, the verdict is clear. The higher upfront cost is not just a markup driven by generic marketing jargon; it is a direct investment in 85%+ electrical efficiency, zero electrical arcing, and a massive 10,000-hour lifespan limited only by mechanical bearings.
By understanding the true internal mechanics rather than relying on guesswork, you are now equipped with the exact engineering-grade logic needed to evaluate your next powertrain. The brushless revolution is no longer just an upgrade – it is the definitive standard.
FAQ
Why do brushless motors have 3 wires?
Unlike brushed motors with two wires (positive and negative), brushless motors use three wires because they operate on a three-phase electrical system. The Electronic Speed Controller (ESC) sends precisely timed, alternating (AC-like) current pulses through these three wires to rotate the internal magnetic field.
Do brushless motors spark?
No, they do not. Brushless motors completely eliminate physical carbon brushes and mechanical commutators, which are the primary causes of electrical arcing and sparking in traditional motors. This makes brushless technology significantly safer for use in highly flammable or explosive environments.
Are brushless motors waterproof?
The motor itself is highly water-resistant because it has no exposed electrical contacts. However, the ESC and sensor wires require dedicated waterproofing. Additionally, submerging the motor will quickly strip lubrication and rust its mechanical bearings – its only physical wear point – drastically reducing its lifespan.
Can a brushless motor run without an ESC?
Absolutely not. A brushless motor cannot run by simply connecting it directly to a DC battery. It strictly requires an Electronic Speed Controller (ESC) to act as its brain, converting the DC power into the sequenced three-phase pulses required to spin the rotor.
Why do brushless motors stutter at low speeds?
Sensorless motors rely on back-EMF to track the rotor. At zero RPM, the lack of back-EMF causes the ESC to guess timing, resulting in rough startup stuttering. A common misconception is calling this “cogging.” True cogging is actually the natural magnetic resistance felt when spinning an unpowered motor by hand.
Are brushless motors AC or DC?
They are DC by input, but AC by internal operation. You supply direct current (DC) to the ESC, which then inverts it into a precisely timed, three-phase alternating (AC-like) waveform to drive the motor’s stator coils.
Do brushless motors need maintenance?
While they eliminate brush replacements, they are not entirely maintenance-free. The mechanical bearings are the primary wear point. Routine maintenance involves keeping the stator free of metallic debris and inspecting the bearings for grit to prevent catastrophic electrical failure.
