Repeat Robotics Mini Brushless Drive Gearmotor MK4.1 – 3mm Shaft
Repeat Robotics Mini Brushless Drive Gearmotor MK4.1 – 3mm Shaft
The Repeat Mini 3mm brushless gearmotor MK4.1 from Repeat Robotics is a small form-factor planetary drive motor designed for antweight combat robots. Its custom-wound 1106 brushless motor and 28.5:1 all-metal planetary gearbox deliver fast, powerful drive performance, with 20% more torque than the MK4. Whether you’re building a new robot or upgrading from traditional brushed gearmotors, MK4.1 brings modern brushless performance to a combat-focused drivetrain.
$35.00
24 in stock (can be backordered)
Repeat Robotics Mini Brushless Drive Gearmotor MK4.1 – 3mm Shaft
Brushless drive power for antweights
The Repeat Mini 3mm brushless gearmotor MK4.1 is designed for builders who want the speed, power, and efficiency advantages of brushless drive in a gearmotor made for combat robotics. It pairs a custom-wound 1106 3500KV brushless motor with a two-stage, 28.5:1 all-metal planetary gearbox. This page is for the 3mm version, sold individually.
Why choose brushless drive?
Brushed gearmotors remain a simple, proven choice for many combat robots. Brushless drive systems trade a little more setup complexity for more power and speed in a similarly sized package. The Mini MK4.1 is rated for 2S-4S operation and is designed specifically around the demands of antweight combat robot drivetrains.
What’s new in MK4.1?
Repeat Robotics updated the MK4 design with a new 1106 motor that provides 20% more torque, while making the drive motor shorter and lighter. MK4.1 also strengthens wire retention with stronger stator winding wires and mechanical clamping at the stator base. Those changes address the motor-lead area while preserving the familiar 16mm planetary gearbox format.
Designed around combat robot drivetrains
The 28.5:1 drive ratio, extra-long D-shaft, and M2 face-mount pattern give builders a straightforward starting point for an antweight drivetrain. The output shaft can be cut to length if needed.
When mounting the gearbox, keep face-screw engagement to approximately 0.08in (2.0mm) or less; screws that extend too deeply can damage the gearbox.
ESC and electronics
These are brushless motors and require a compatible brushless ESC configured for bidirectional drive operation. Repeat Robotics offers both single and dual AM32 drive ESCs for this purpose. You can also browse ItGresa’s ESC selection for additional options. Select the proper ESC for your battery voltage, motor configuration, and drivetrain requirements.
More drivetrain options
See the FAQ tab for common questions about ESC selection, shaft choice, wiring clearance, and mounting. You can also explore combat robotics motors at ItGresa for other drivetrain choices.
- Find the 4mm shaft Mini Mk4.1 here: https://itgresa.com/product/repeat-robotics-mini-brushless-gearmotor-mk4_1-4mm/
- Find the 3mm shaft Mini Pro 1106: https://itgresa.com/product/repeat-robotics-mini-pro-1106-brushless-gearmotor/
Features
- MK4.1 revision delivers 20% more torque than MK4
- 3500KV custom 1106 motor for fast brushless drive
- 28.5:1 all-metal planetary gearbox for drivetrain reduction
- 2S-4S voltage range supports common antweight batteries
- Stronger wire retention with mechanical clamping at the stator
- 3mm D-shaft output can be trimmed to length
- Shorter and lighter MK4.1 design than the prior MK4
Basic Specifications
| Specification | Details |
|---|---|
| Revision | MK4.1 |
| Motor | Custom-wound 1106 brushless motor |
| KV | 3500KV |
| Rated Voltage | 2S-4S |
| Gearbox | Two-stage, all-metal planetary |
| Gear Ratio | 28.5:1 |
| Gearbox Diameter | 0.63in (16.0mm) |
| Body Length | ~1.10in (~28.0mm) |
| Output Shaft | 0.12in (3mm) D-shaft; extra-long and may be cut to length |
| Weight | 0.79oz (22.4g) |
| Face Mount Pattern | 0.41in (10.5mm), M2 |
| Maximum Face-Screw Engagement | ~0.08in (~2.0mm); longer screws can damage the gearbox |
Frequently Asked Questions
What makes a brushless gearmotor different from a traditional brushed gearmotor?
Brushless motors typically offer higher power density, improved efficiency, and faster throttle response than similarly sized brushed motors. They also require a compatible brushless ESC rather than a brushed speed controller. An easy way to tell the difference is the wiring: brushless motors have three wires connecting to the ESC, while brushed motors have only two wires or two terminals.
What ESC should I use with the MK4.1?
ItGresa offers the broadest selection of ESCs of all types, including Repeat Robotics’ AM32 brushless ESCs. Repeat recommends pairing the Mini Brushless Drive Gearmotor MK4.1 with the Repeat Robotics AM32 ESC. For a two-wheel-drive robot you need two single ESCs, or one Repeat Robotics Dual AM32 ESC to control both drive motors. Repeat Robotics founder Peter Garnache personally prefers the dual. Both come pre-programmed for bidirectional drive operation. You can also browse all ESCs at ItGresa. Always verify that your ESC supports your battery voltage and motor configuration.
TIP:
Not all brushless ESCs are configured the same way. Drive ESCs are typically programmed for bidirectional operation, allowing your robot to drive forward and reverse. Weapon ESCs are usually configured for forward-only operation because you generally do not want a weapon to spin backwards. If you install a forward-only ESC in your drivetrain, your robot will only drive forward. Many brushless ESCs can be reprogrammed with a compatible programmer such as our USB ESC Linker or the Grey Skies ESC Programmer.
Should I choose the 3mm or 4mm shaft version?
Both versions use the same motor and gearbox. The 4mm shaft is more robust and harder to bend, so if your design has the weight allowance, we would generally choose it for durability. The 3mm shaft is more common in antweights. Make sure your hub bore matches the shaft: a 4mm shaft needs a 4mm hub, and a 3mm shaft needs a 3mm hub.
Is this motor suitable for antweight combat robots?
Yes. Repeat Robotics designed the MK4.1 specifically for antweight combat robotics and rates it for 2S-4S operation.
What should I know before switching from brushed to brushless drive?
First, use a compatible brushless ESC with bidirectional operation for drive motors. Second, remember that the outer can of the 1106 motor spins. Keep wires and other parts well clear of the rotating motor. Many builders 3D print small protective cups that fit over the end of the gearmotor to help keep wiring away from the spinning can. They are not required, but they can be a useful protective addition.
How deep can the face-mount screws go?
Repeat Robotics specifies only about 0.08in (2.0mm) of face-screw engagement. Using screws that extend farther into the gearbox can damage it, so check screw length carefully when designing your mount.
Does this motor include an ESC?
No. The gearmotor is sold individually and does not include an ESC. See “What ESC should I use with the MK4.1?” above for drive ESC options.