| 40KG·CM STALL | 0.088S/60° NO-LOAD | 8.4V RATED |
| 73G WEIGHT | StainlessGEARTRAIN | 360°TRAVELCustomizable |
Overview
The S8035D is the quickest servo in this 8.4 V coreless series: 40 kg·cm at 0.088 s/60°, which is 682 °/s at the output spline, in the standard 20 × 40 × 38.4 mm case at 73 g. It takes a normal 800–2200 µs pulse train, so it drops into any receiver, gyro or flight controller that already drives a digital servo.
The torque comes from a coreless rotor behind a stainless geartrain. At this class the first gear stage usually gives up before the motor does, and that is the part the stainless train buys you — at a cost of 73 g on the scale, which is the honest trade at 40 kg·cm.
Performance at each supply voltage
| Supply | No-load speed | Peak stall torque | Idle current | Stall current |
|---|---|---|---|---|
| 6.0 V | 0.131 s/60° (458 °/s) | 28 kg·cm (2.75 N·m / 389 oz·in) | 320 mA | 3.7 A |
| 7.4 V | 0.104 s/60° (577 °/s) | 34 kg·cm (3.34 N·m / 472 oz·in) | 370 mA | 4.5 A |
| 8.4 V | 0.088 s/60° (682 °/s) | 40 kg·cm (3.92 N·m / 555 oz·in) | 440 mA | 5.2 A |
Control specification
| Item | Specification |
|---|---|
| Command signal | PWM (50–333 Hz) |
| Amplifier | Digital controller |
| Pulse width range | 800–2200 µs |
| Neutral position | 1500 µs |
| Dead band | 1 µs |
| Rotating direction | CCW (1000–2000 µs) |
| Travel | 360°, customizable |
Mechanical specification
| Item | Specification | Item | Specification |
|---|---|---|---|
| Dimensions | 20 × 40 × 38.4 mm | Case material | CNC aluminium |
| Weight | 73 g | Geartrain | Stainless steel |
| Bearings | 2 × ball bearing | Motor | Coreless |
| Output spline | 25T / 5.94 mm | Horn in box | POM plastic |
| Lead | 300 mm | Travel limit | 360°, customizable |
| Operating temperature | −15 °C to 65 °C | Storage temperature | −20 °C to 70 °C |
| Ingress protection | Splash resistant (customizable) |
What’s in the box
- 1 × XQ-S8035D servo
- 1 × POM horn set
- 1 × mounting screw pack
Optional: metal horn, sold separately.
How to size it
Torque budget = load at the horn × horn length from spline centre × 1.5 safety factor.
Worked example: a 6 kg surface with its centre of pressure 35 mm from the spline centre needs 6 × 9.81 × 0.035 × 1.5 ≈ 3.09 N·m. The S8035D delivers 3.92 N·m at 8.4 V, about 27% headroom. That margin is not padding — a servo held near stall through a long hold dissipates heat continuously, and heat is what ends a correctly sized servo’s life.
FAQ
Can I run it directly from a 2S LiPo?
Yes. A 2S pack is 8.4 V at full charge, which is the top rail in the inspection sheet and the rail the 40 kg·cm figure is measured at. There is no headroom above 8.4 V. Bear in mind a receiver rated for 6 V will not pass 8.4 V through — power the servo from a BEC or a direct lead, not through an old receiver bus.
What pulse range does it accept?
700 µs below and 2300 µs above are outside spec: the window is 800–2200 µs with 1500 µs neutral. A 1 µs dead band means it will hunt if your controller has a noisy output, so keep the signal lead short or use a buffered output.
The photo says 40KG but the datasheet header says 35kg-cm — which is right?
40 kg·cm at 8.4 V is the measured peak stall in the inspection table, and the product photo carries the same number. The header string predates the top-rail measurement. This page publishes the measured figure.
Why are there three different torque figures?
Because torque, speed and current all scale with supply voltage: 28 kg·cm at 6.0 V, 34 at 7.4 V, 40 at 8.4 V. Compare servos at the same rail or the comparison means nothing.
Does it rotate continuously?
Travel is 360° when commanded over 1000–2000 µs, as a factory customization. Standard units work across the 800–2200 µs window. Continuous rotation is set at build time, not by a switch afterwards.
Is there a serial version?
Yes — the XQ-S8035TTL is the same servo with a TTL serial command layer. Same motor, geartrain, case and 40 kg·cm; the difference is the wiring and the protocol.
How much is 40 kg·cm in oz·in?
About 555 oz·in, or 3.92 N·m. Same torque in three units — US hobby buyers quote oz·in, robotics and European buyers quote N·m.
Downloads
- XQ-S8035D inspection specification (PDF, 787 KB)
Torque, speed and current at 6.0 / 7.4 / 8.4 V, mechanical data, control specification, mounting dimensions. - 2D dimension drawing (image)
Quick view of mounting hole positions and case depth; the same drawing is inside the datasheet.
