| 75KG·CM STALL | 0.110S/60° NO-LOAD | 8.4V RATED |
| 88G WEIGHT | StainlessGEARTRAIN | 360°TRAVELCustomizable |
Overview
The BLS8175D is the 75 kg·cm end of the standard-size brushless range: same 20 × 40 mm footprint as the 8135 and 8145, but 40 mm deep and 88 g, because the geartrain and the motor behind it are bigger. At 8.4 V it delivers 75 kg·cm at 0.11 s/60°.
Two details separate it from the smaller models. The output is a 25T-φ7.96 mm spline — larger than the φ5.94 used on the 48 kg·cm build, so horns do not cross over — and the box includes a 7075 aluminium CNC horn rather than a POM one, which is the right call at this torque.
This page covers the RS-485 build: the same mechanics, commanded over a differential serial bus instead of a PWM channel. It is the version to pick when several servos sit on one pair of wires or when the cable run is long enough that a single-ended signal would pick up noise.
Performance at each supply voltage
| Supply | No-load speed | Peak stall torque | Idle current | Stall current |
|---|---|---|---|---|
| 6.0 V | 0.170 s/60° (353 °/s) | 53 kg·cm (5.20 N·m / 736 oz·in) | 320 mA | 6.0 A |
| 7.4 V | 0.140 s/60° (429 °/s) | 65 kg·cm (6.38 N·m / 903 oz·in) | 370 mA | 7.5 A |
| 8.4 V | 0.110 s/60° (545 °/s) | 75 kg·cm (7.36 N·m / 1042 oz·in) | 440 mA | 9.0 A |
Control specification
| Item | Specification |
|---|---|
| Command signal | RS-485 |
| Amplifier | Digital controller |
| Dead band | 2 µs |
| Rotating direction | CCW (1000–2000 µs) |
| Travel | 360°, customizable |
Mechanical specification
| Item | Specification | Item | Specification |
|---|---|---|---|
| Dimensions | 20 × 40 × 40 mm | Case material | Aluminium, CNC |
| Weight | 88 g | Geartrain | Stainless steel |
| Bearings | 2 × ball bearing | Motor | Brushless |
| Output spline | 25T-φ7.96 mm | Horn | 7075 aluminium, CNC |
| Lead / connector | 300 mm, 3-wire | Mechanical limit | 210° |
| Operating temperature | −15 °C to 65 °C | Storage temperature | −20 °C to 70 °C |
| Ingress protection | Splash resistant (customizable) | Travel | 360°, customizable |
What’s in the box
- 1 × XQ-RS8175D servo
- 1 × 7075 aluminium horn
- 1 × mounting screw pack
How to size it
Torque is 53 kg·cm at 6.0 V, 65 at 7.4 V and 75 at 8.4 V, at 0.17, 0.14 and 0.11 s/60°. The 8.4 V figure is the one on the box; on a loaded 2S pack plan on 65 kg·cm.
Stall current runs 6.0 A at 6.0 V, 7.5 A at 7.4 V and 9.0 A at 8.4 V. Two of these on one BEC is 18 A at stall — if the receiver resets under load, the supply is the problem, not the servo. Use a rail rated for the stall current, not the idle current.
FAQ
BLS8145D or BLS8175D?
48 kg·cm versus 75, 73 g versus 88 g, 38.4 mm versus 40 mm deep. The 8175D also changes the spline to φ7.96 mm and ships with a 7075 aluminium horn. If your linkage and horn set are built around a φ5.94 spline, staying on the 8145D avoids redesigning the arm.
Will my existing 25T horns fit?
Check the centre diameter. 25T splines are not all the same size — this one is φ7.96 mm, where the 8135D and 8145D are φ5.94 mm. A φ5.94 horn will not seat on it.
Does the RS-485 build speak Modbus?
The inspection sheet lists RS-485 as the command signal and nothing more. Ask for the register map and the supported function codes before you write the controller code — do not assume a Modbus dialect.
How many servos can share the bus?
The limit is the address space and the current budget of the shared supply. Terminate the pair at both ends and keep the power pair separate from the signal pair.
Other interfaces
Downloads
- XQ-RS8175D inspection specification (PDF, 820 KB)
Torque, speed and current at each supply voltage, mechanical data, control specification, mounting dimensions. - 2D dimension drawing (image)
Mounting hole positions, case depth and overall height; the same drawing is inside the datasheet.
