At deep-hole drilling sites hundreds of meters underground, the raise borer is truly a pioneering beast.
When faced with high-hardness rock formations, not only must the drill rig itself have a strong and robust structure, but its power core—the hydraulic motor—must also be capable of delivering powerful and steady output during high-load, low-speed operation.
However, in actual construction, a problematic situation often arises unexpectedly: when the drill rig is boring through hard rock at low speeds and under heavy loads, the power head exhibits intermittent jerking movements—the so-called “crawling” phenomenon. At the same time, the hydraulic pump station’s piping experiences violent vibrations, and a piercing high-frequency noise fills the machine room.
In hydraulic engineering, this phenomenon is known as system fluid oscillation and water hammer effects caused by “flow interruption in the distribution valve.” It is not merely a sign of inefficiency; it is also a “silent killer” that can cause significant losses, such as shattering high-value drill pipes, dislodging alloy teeth from the cutterhead, and even triggering borehole collapses and drill bit jamming.
When faced with extreme and demanding operating conditions, how can we ensure that a raise boring rig delivers smooth, unimpeded power? Today,we’ll start with the fundamentals of hydraulic science to reveal the benchmark for power in heavy-duty mining excavation—the MS Series internal-curve radial piston hydraulic motor—and see how its top-notch quality perfectly empowers our AT-3000L raise boring rig.
As is well known, the workflow for a raise boring rig involves first drilling a guide hole several hundred millimeters in diameter from top to bottom (or bottom to top) to penetrate the upper and lower sections; then, a reaming cutterhead—often two or three meters in diameter—is installed to “gnaw” the guide hole in the opposite direction until it becomes a large shaft of the designed diameter.
The problem lies in the reaming step—the larger the cutter head, the slower the rotational speed must be , yet the torque required to break through rock is several or even dozens of times higher than that of a conventional drill rig. This places extremely demanding requirements on the drive system：
And at the heart of it all is often an unassuming yet crucial component: the hydraulic motor.
Compared to electric motors, hydraulic motors offer higher power density and a more compact design, enabling them to deliver extremely high torque in limited spaces. At the same time, they feature strong overload capacity and support stepless speed control, making them particularly well-suited for applications involving frequent forward and reverse operation and heavy-load impacts. This is why hydraulic motors are virtually indispensable in the core drive systems of everything from tunnel boring machines to raise boring rigs.
Among the many types of hydraulic motors, the Multi-stroke radial piston motor is the “specialist” for low-speed, high-torque applications—it is inherently designed for “slow speed and high torque”.
The core function of the rotor is to “convert pressure into force.” It takes the pressure energy of the high-pressure hydraulic oil delivered by the hydraulic pump, transmits it through the force applied to the piston, and ultimately converts it into mechanical energy (torque and rotational speed) that drives the rotation of the power head on the raise boring rig.
The piston and roller are typically installed as a single assembly within the rotor bore.The piston body is a cylindrical chamber that contains hydraulic fluid; its function is to convert the pressure of high-pressure hydraulic fluid into a massive linear thrust that pushes outward. The roller is mounted in a V-shaped or spherical roller seat at the head of the piston body. It converts the piston’s outward linear thrust into a lateral tangential force that drives the rotor’s rotation by rolling along the wave-shaped inclined surface of the stator. At the same time, it transforms sliding friction into rolling friction, preventing the motor from seizing up under immense force.
The stator is the motor’s outer casing. Its inner wall consists of multiple peaks and troughs that form a precision wave-shaped cam track. During operation, it remains stationary and provides a reaction force. When the piston pushes the roller outward and reaches the downward slope, the stator uses the incline to convert the piston’s linear thrust into a tangential rotational force, serving as the core mechanical fulcrum for achieving high torque at low speeds.
The oil distribution system is a precision component that diverts and distributes oil to the individual piston chambers. Its precision is evident in its control of the inflow and retraction of both high- and low-pressure oil; the distribution body must fit tightly against the rotating cylinder body to prevent high-pressure oil leaks that could cause the power head to lose force or malfunction. Furthermore, to withstand liquid pressures as high as several hundred kilograms and prevent the end face from being forced open, the back of the distribution body features a hydraulic automatic compensation chamber that ingeniously utilizes the force of the high-pressure oil itself to achieve dynamic clamping and oil sealing.
Bearings are mounted at both ends of the rotor; not only do they stabilize the rotor and ensure it rotates without eccentricity, but they also withstand the enormous thrust and lateral impacts transmitted by the drill rig. The seals serve a dual purpose of “sealing internally and protecting externally”: internally, they prevent hydraulic oil leakage through gaps in the contact surfaces; externally, they block mine dust to prevent internal contamination. Together, they ensure the motor’s long-term, stable operation under high pressure and heavy loads.
Even though they’re both called “internal curve radial piston motors,” their performance can vary dramatically, depending primarily on:
Volumetric efficiency measures a hydraulic motor’s ability to convert input flow into effective output speed. It essentially reflects the overall sealing performance within the motor, with the core focus on evaluating leakage losses of the working fluid during pressure transmission. A value between 90% and 98% is considered good; the higher the volumetric efficiency, the more precisely the distribution body fits against the cylinder block, and the lower the leakage rate.
Mechanical efficiency measures a hydraulic motor’s ability to convert input pressure energy into effective output torque. It essentially reflects the degree of energy loss due to friction pairs within the motor during operation. The key lies in assessing the proportion of driving force lost to various mechanical resistances during transmission; these frictional resistances directly consume a portion of the torque, hindering its conversion into effective output. To operate efficiently, this value must be maintained at 90%.
In general, when hydraulic motors operate at speeds below 10–50 RPM, their output torque experiences severe fluctuations due to sudden changes in internal friction. Industry-leading models can achieve a minimum stable speed as low as 0.5 RPM or even 0.1 RPM, and high-quality radial piston motors with an internal curved bore can effectively prevent crawling and stick-slip phenomena.
In addition to the mandatory specifications, the hydraulic motors of raise boring rigs can be designed and optimized in terms of displacement options, overload protection, pressure-relief buffering, and hydrostatic lubrication.
All right, so the next time you need to choose a hydraulic motor, you won’t feel lost.
The MS Series is a direct-drive, versatile hydraulic motor with a maximum output power of 140 kW, designed specifically for wheeled machinery and tool drive systems. The motor has a displacement range of 3,500 to 6,011 cc/rev, a maximum operating pressure of 450 bar, and a peak torque of up to 43,000 N·m. With its multi-speed design, it can reach a maximum speed of 225 rpm, effectively meeting the dual requirements of low-speed heavy-load operation and high-speed travel.
| Parameter | Value | |
 | Maximum Displacement | 6011cc/rev |
| Maximum Power | 140KW/188HP | |
| Maximum Torque | 43000Nm/31715lb-ft | |
| Maximum Operating Pressure | 450.00Bar/6527.00PSI | |
| Maximum Speed | 225RPM | |
| Motor Type | Wheel Motor / Shaft Motor | |
| Brake System | Service Brake + Parking Brake |
Multi-speed Design: The MS Series incorporates a multi-speed concept, allowing the displacement to be switched according to operating conditions.This flexibility allows a single motor to adapt to a wide range of operating conditions, from low speed and high torque to high speed and low torque.
Modular Design：
The modular design allows the MS Series hydraulic motor to be disassembled with ease, with each module performing a specific function and connecting seamlessly. This modular design adapts to a wide range of operating conditions, facilitates maintenance, and can be flexibly configured to meet different application requirements.
Twin-Lock™ Technology：
Twin-Lock™ is a smart hydraulic anti-slip system balancing powerful traction with flexible steering. When a wheel slips, it instantly limits flow and redirects power to wheels with grip for recovery. It ensures solid straight-line traction and releases during turns, maximizing efficiency without vehicle deviation.
The AT-3000L (CY-R120V) is a fully hydraulic, intelligent crawler type raise boring machine equipped with two MS Series.2.A16.A50 heavy-duty hydraulic motors capable of delivering high torque at low speeds. During the initial design phase of this drilling rig, we faced technical challenges involving high rotational torque, high rotational speed, and limited installation space. The traditional “high-speed motor + gearbox” solution failed to meet the requirements for reliability and size, and the gearbox required regular inspections and oil changes. Ultimately, we adopted the MS series of low-speed, high-torque hydraulic motors and successfully implemented them in mass production on the AT3000-L.
In deep-hole drilling operations in underground mines, raise boring rigs must perform large-diameter, high-precision, long-distance drilling within confined spaces. The AT-3000L (domestic model CY-R120V), as China’s first self-propelled intelligent large-diameter raise boring rig, has a nominal reaming diameter of 3,000 mm, a maximum drilling depth of 400 m (up to 500 m when f ≤ 14), and a required well deviation rate controlled within 0.5%. To manufacture the AT-3000L in strict accordance with these highly demanding specifications, we carefully selected a hydraulic motor that offers high compatibility and delivers robust power. We found that the MS Series heavy-duty piston motor perfectly meets the AT-3000L’s required specifications and operational standards, providing the rig with superior drilling efficiency and an excellent construction experience.
The limited space in underground mine chambers imposes strict requirements on equipment dimensions. The MS Series features a modular design; each motor weighs approximately 400 kilograms and has a displacement of up to 6,011 cc, offering a significant size advantage over large, heavy hydraulic motors. Additionally, the two MS Series motors are arranged in an axially symmetrical configuration, enabling direct drive of the power head spindle and greatly enhancing construction stability.
The MS Series hydraulic motor features a dual-displacement function, allowing it to flexibly switch between displacement modes to meet the requirements of different operational phases of a raise boring rig. During the pilot hole stage, the motor operates in low-displacement mode, using high speed and low torque output to drive the drill bit downward rapidly and efficiently form the pilot hole; upon entering the reaming stage, the motor seamlessly switches to high-displacement mode, shifting to low speed and high torque output to provide the drill bit with continuous, smooth, and jam-free pull-up force and cutting torque. This dual-displacement design enables a single motor to simultaneously meet the requirements of two distinctly different operating conditions—pilot hole drilling and reaming—without the need to replace the motor or reconfigure the gearbox.
During reaming operations, the AT-3000L must deliver a rated torque of 168 kN·m and a peak torque of 192 kN·m to break through hard rock formations. The Poclain MS Series motors have a maximum displacement of 6,011 cc/rev and can deliver a maximum torque of 43,000 N·m at an operating pressure of 450 bar, with a maximum power output of 140 kW. Working in tandem, the two MS Series motors provide the drill rig with ample torque reserve and power redundancy, ensuring continuous and stable power output during drilling in hard rock sections. At the same time, the combined power of the two motors is matched to the drill rig’s 160 kW main motor, enabling efficient utilization of the power source.
The AT-3000L (CY-R120V) raise boring rig and the MS Series hydraulic motor together form a proven, high-performance solution for the most demanding underground drilling conditions. The MS Series’s dual-displacement capability, low-speed stability, and high torque output perfectly match the AT-3000L’s requirements for pilot hole drilling and reaming, delivering smooth, jam-free operation and exceptional borehole accuracy.
We are proud to offer both the MS Series hydraulic motor and the AT-3000L raise boring rig—either as individual components or as a fully integrated system. Whether you need to upgrade an existing rig or build a new fleet, our team can provide the right configuration, technical support, and after-sales service to keep your projects on track.
For more information on how the MS Series and AT-3000L can improve your drilling efficiency, reduce downtime, and lower total cost of ownership, please contact us today. Let us help you power through hard rock with confidence.
