ProTechTrader RS-550S 18V Brushed DC Motor with 3.175mm D-Shaft for Drill Replacement and Robotics
ProTechTrader RS-550S 18V Brushed DC Motor with 3.175mm D-Shaft for Drill Replacement and Robotics
The ProTechTrader RS-550S is a brushed DC motor designed for replacement and upgrade in power tools, robotics, and DIY projects. It features a 3.175mm diameter D-shaft, a body length of 57mm, and an 18V nominal voltage, delivering up to 20,000 RPM at no load and around 17,000 RPM at peak efficiency. Weighing approximately 218 grams, it fits many 3/8-inch cordless drills and other equipment, but verify dimensions before ordering.
Technical Specifications
| Model | RS-550S |
| Motor Type | Brushed DC, carbon brushes |
| Body Dimensions | 57mm length x 37.5mm diameter |
| Shaft | D-shaft, 3.175mm diameter x ~9mm length |
| Weight | ~218g (7.7oz) |
| Operating Voltage | 6V – 24V DC (optimal 12V – 18V) |
| No Load RPM | ~20,000 |
| RPM at Peak Efficiency | ~17,000 |
| Stall Current | ~85A |
| Stall Torque | ~70.55 oz-in (498.2 mN·m) |
| Efficiency | ~70% |
| Mounting Holes | M3, spaced 25mm apart |
Performance and Power Delivery
At its optimal voltage near 18 volts, this motor produces a balance of speed and torque. The no-load speed reaches about 20,000 RPM, while under peak efficiency it drops to around 17,000 RPM. With a stall torque over 70 oz-in, it can handle moderate loads common in drills and small robots. The stall current peaks at 85A, so ensure your power source can supply that briefly.
What Should You Verify Before Replacing an Existing Motor?
Before purchasing, check that the motor matches your application's requirements. Measure the shaft diameter (3.175mm D-shaft), shaft length (about 9mm), body diameter (37.5mm), and body length (57mm). The mounting holes use M3 screws spaced 25mm apart. Also confirm the voltage range (6–24V) is compatible with your device. This motor is designed as a drop-in replacement for many 3/8-inch drills, but not all models—always compare spec for spec.
Frequently Asked Questions
What is the shaft style and diameter?
It uses a D-shaft with a diameter of 3.175mm (1/8 inch). The flat on the shaft provides a secure fit with compatible couplers or gears.
What voltage should I run it at?
The motor works from 6V to 24V, but optimal performance—best balance of speed, torque, and efficiency—occurs at 12V to 18V. The nominal rating is 18V.
Can this motor replace the motor in my cordless drill?
It is built to fit many 3/8-inch cordless drills, but it's not universal. Compare body dimensions, shaft length and diameter, and mounting hole spacing with your original motor before ordering.
What is the no-load current draw?
At no load, the motor draws about 1.2A. Under load, current increases; stall current can reach 85A.
Common Applications
Beyond drill replacements, this motor is a popular choice for DIY electronics and robotics projects, PowerWheels modifications, gate openers, and other outdoor tool conversions. Its compact size and high torque output make it versatile for custom builds. Always test the motor with a suitable power supply and controller to match your specific use case.