Specification Differences Between Brands: How to Read Spec Sheets Critically

You're building a compact robot arm, a precision camera gimbal, or an intricate animatronic puppet. Your component of choice? The humble, yet critical, micro servo motor. You hit the web, and a dizzying array of options floods your screen: brands promising "high torque," "lightning speed," and "metal gears" at every price point. The natural instinct is to compare the specification tables—to let the numbers decide. But here lies the trap: not all spec sheets are created equal, and not all specifications are measured the same way.

In the world of micro servos, where a difference of a few grams-centimeters or milliseconds can make or break a project, learning to read spec sheets critically is your most vital engineering skill. This guide will equip you to look beyond the marketing fluff, understand the unspoken truths behind the numbers, and make informed choices between brands like Savox, KST, Spektrum, HiTec, and the myriad of OEM options from Asia.

The Anatomy of a Spec Sheet: More Than Just a Table

At first glance, every spec sheet lists similar parameters. Your job is to interrogate each one.

The Core Trinity: Torque, Speed, and Voltage

These are the headline figures, and they are deeply interdependent.

Torque: The King of Misrepresentation

Torque, typically listed in kg-cm or oz-in, is the servo's rotational force. This is the most commonly manipulated spec.

• The Stall Torque Illusion: Many budget brands prominently list stall torque—the torque the servo outputs when forced to a standstill. It's an impressive, peak number. Reputable brands (e.g., MKS, Savox) often list operating torque—the sustainable torque within normal operational limits, which is significantly lower but far more realistic.
• The Voltage Factor: Torque is not a fixed value. A servo rated at "6.0 kg-cm" will have that figure measured at a specific voltage, usually 4.8V or 6.0V for analog servos, and 7.4V or 8.4V for high-voltage digital ones. Always check the test voltage. A brand may boast high torque by testing at an elevated voltage that your application's BEC (Battery Eliminator Circuit) may not support.
• The Gear Train's Role: The final torque is a function of the motor's power and the gear reduction. A number alone doesn't tell you if that torque is smooth or jerky, or if it can be maintained without gear tooth failure.

Speed: The Context-Free Promise

Speed, measured in seconds for a 60-degree rotation, seems straightforward. But critical details are often omitted.

• No-Load vs. Loaded Speed: The flashy "0.08 sec" speed is almost always a no-load speed measurement. The moment you attach a control horn and apply resistance, speed plummets. Ask: at what torque was the speed measured? A quality sheet might provide a performance graph showing the speed-torque curve.
• The Digital Advantage: Digital servos (like those from Spektrum's "A" series or Futaba) use higher frequency drive signals to achieve higher holding power and often faster initial response times than their analog counterparts, even if the "60-degree travel" spec is similar. The spec sheet should clearly state "Digital" or "Analog."

Operating Voltage Range: The Power Corridor

A servo listing "4.8-6.0V" is giving you its safe operating range. Pushing it to 6.0V will increase both speed and torque. A "high-voltage" servo rated for "7.4-8.4V" is designed for modern LiPo-powered systems. Critical Question: Are the torque and speed specs given at the lower, middle, or top of this range? A honest brand will specify (e.g., "6.0 kg-cm @ 4.8V, 7.5 kg-cm @ 6.0V").

The Hidden Determinants of Performance and Lifespan

The core trinity sells the servo. These next specs determine if it will survive.

Gear Material: The Hierarchy of Strength

This is a prime differentiator. The listing "Metal Gears" is insufficient. 1. Plastic / Nylon Gears: Lightweight, quiet, and cheap. They absorb shock well but strip under load or stall. Common in ultra-micro or budget servos. 2. Karbonite / Composite Gears (HiTec's trademark): A fiber-reinforced composite. More durable than plastic, quieter and lighter than full metal, with good shock absorption. 3. Metal Gears: The standard for performance. But not all metals are equal: * Brass / Aluminum: Softer, used in non-critical stages or budget metal-gear servos. Can wear or deform. * Steel: The standard for core torque gears. Look for "Steel Gears" or "Titanium-Coated Steel" (like in KST servos). These handle high loads and shocks. * Titanium: The premium option (e.g., high-end Savox). Lighter and stronger than steel, offering the best strength-to-weight ratio for the gear train.

Bearing Type: The Support System

"Double Ball Bearing" support is a key phrase. It refers to bearings at the top and bottom of the output shaft, replacing simple bushings. * Bushings: Sleeves of brass or bronze. They wear faster, allow more slop (play) over time, and handle radial loads poorly. * Ball Bearings: Provide smoother rotation, significantly reduce slop, handle both radial and axial loads better, and extend servo life. The number and placement of bearings are a mark of quality.

Motor Type: The Heart of the Servo

Often buried in the details, this is crucial. * Coreless Motors: The rotor is a hollow, wire-wound basket. They offer faster acceleration, higher efficiency, and smoother operation than 3-pole or 5-pole motors. Common in mid-to-high-range servos. * Brushless Motors: The pinnacle. The stationary coils are on the stator, and magnets are on the rotor. They run cooler, are vastly more efficient, have incredible lifespan, and deliver exceptional power. Brands like MKS and Xpert heavily feature brushless designs. Their presence usually denotes a top-tier servo.

Decoding Brand-Specific Terminology & Testing Methods

Brands use language to position themselves. Here’s a translation:

• Savox / MKS: Often emphasize "Holding Torque" and provide detailed graphs. Their specs tend to be conservative and reliable. They highlight waterproofing (IP ratings) and programmability features.
• HiTec: Pioneered user-friendly features like programmable soft-start, deadband, and endpoint adjustment. Their "D" series digital specs are robust. They are transparent about gear composition (Karbonite).
• Spektrum / Horizon Hobby: Specs are tailored for the R/C market. They emphasize integration (DSMR telemetry, Smart technology) and durability. Look for "Stall Torque" in their tables—understand it as a peak, not continuous, rating.
• KST / OEM Brands: Often offer impressive numbers at low cost. Scrutiny is essential. Is that torque at 8.4V? Are the "steel gears" only on the final output? Check community forums for real-world durability tests.

The Critical Checklist for Your Next Purchase

Before you click "buy," run down this list of questions derived from the spec sheet:

1. Torque Context: Is this stall or operating torque? At what voltage is it measured?
2. Speed Reality: Is this no-load speed? Is there a performance graph?
3. Voltage Specificity: Are the key specs given at a stated voltage within the operating range?
4. Gear Transparency: Does it specify the material for all gears, or just say "metal"?
5. Bearing Clarity: Does it specify "ball bearing" or just "bearing"? Is it single or double?
6. Motor Disclosure: Does it mention "coreless" or "brushless"? If not, assume a standard 3-pole or 5-pole ferrite motor.
7. Dimensions & Weight: Are they exact? Does the weight include wires and connector? A 0.5g difference matters in a drone.
8. Pulse Width Range: Is it a standard (1500µs center) servo, or does it have a wider range (e.g., 500-2500µs) for greater resolution?
9. Idle Current & Stall Current: Digital servos consume more power at rest (idle current). High stall current can crash your vehicle's BEC. Are these listed?
10. Real-World Data: This is the final step. The spec sheet is a starting point, not the finish line. Find independent tear-downs, thermal imaging tests under load, and long-term durability reviews from trusted users in your application field (e.g., competitive RC crawling, FPV drone cinematography, robotics).

The difference between a project that works flawlessly and one that fails under stress often comes down to the deep, critical understanding of the tiny components that drive it. By learning to read between the lines of a micro servo spec sheet, you stop being a passive consumer and become an informed engineer, selecting not just the part with the biggest numbers, but the right tool for the job.