| 85KG·CM STALL | 0.110S/60° NO-LOAD | 8.4V RATED |
| 92G WEIGHT | StainlessGEARTRAIN | 360°TRAVELCustomizable |
Overview
The BLS8185D is the 85 kg·cm low-voltage build: 20 × 40 × 44 mm, 92 g, and the same 25T-φ7.96 mm output as the 8175D one step down. It reaches its full 85 kg·cm at 8.4 V, which is what makes it a 2S part rather than a 4S one.
Stainless steel geartrain on two ball bearings, CNC aluminium case, and a 7075 aluminium CNC horn in the box — at this torque a POM horn is not the right default. The output has no mechanical stop, so travel is set entirely by the controller, and the 360° running degree is a real option rather than a customization that needs a different part.
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) | 42 kg·cm (4.12 N·m / 583 oz·in) | 320 mA | 4.0 A |
| 7.4 V | 0.140 s/60° (429 °/s) | 75 kg·cm (7.36 N·m / 1042 oz·in) | 370 mA | 5.0 A |
| 8.4 V | 0.110 s/60° (545 °/s) | 85 kg·cm (8.34 N·m / 1180 oz·in) | 440 mA | 6.0 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 × 44 mm | Case material | Aluminium, CNC |
| Weight | 92 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 | No limit |
| 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-RS8185D servo
- 1 × 7075 aluminium horn
- 1 × mounting screw pack
How to size it
Torque is 42 kg·cm at 6.0 V, 75 at 7.4 V and 85 at 8.4 V, at 0.17, 0.14 and 0.11 s/60°. The step from 6.0 V to 7.4 V is unusually large on this winding — on a 2S pack that sits near 7.4 V under load, the honest working figure is 75, not 85.
Stall current runs 4.0 A at 6.0 V, 5.0 A at 7.4 V and 6.0 A at 8.4 V. Two of these on one rail is 12 A at stall. If the receiver resets during a hard manoeuvre, add a servo rail before changing the servo.
FAQ
BLS8185D or BLS8185HV?
Same case, same geartrain, same 92 g — different winding. The low-voltage build gives 85 kg·cm at 8.4 V and is meant for 2S. The HV build gives the same 85 kg·cm at 16.8 V and only 42 kg·cm at 8.4 V. Pick by the pack you already run, not by the headline torque.
Will my 25T horns fit?
Check the centre diameter — this is a φ7.96 mm spline, the same as the 8175D, not the φ5.94 mm used on the 8135D and 8145D. A φ5.94 horn will not seat, even though both are called 25T.
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-RS8185D inspection specification (PDF, 807 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.
