Which hydraulic motor for a drilling rig should you choose? We check the key parameters

Choosing the right hydraulic motor for a drilling rig is not a technical detail that will 'somehow get sorted out along the way'. It is a decision on which the drilling performance, the stability of the excavator and the service life of the entire attachment depend. If the parameters don't play together right from the start, even the best drill rig will just spin in place instead of realistically working the ground. In this guide, you'll find specific tips for choosing the right solution for your machine, field conditions and daily operations - without costly mistakes or unnecessary compromises.

Torque, pressure and flow - the three numbers that will determine whether your drill rig 'goes to ground' or just spins in place

It's worth making one thing clear right from the start - selecting a hydraulic motor for a drilling rig doesn't start with a catalogue, it starts with the parameters of your excavator's hydraulics. It is the torque, operating pressure and oil flow that form the interconnected system that either allows you to drill stably and predictably, or you end up with frustration, overheating oil and zero performance. Torque determines whether the auger actually 'bites' into the ground or merely glides over its structure. For light mini-excavators, we are talking about values in the range of 2000-3500 Nm, for medium machines 6000-8000 Nm and for heavy applications even 20000 Nm. If the torque is too low in relation to the ground conditions, the drill rig starts to work at its limits, leading to overloading of the gearbox, excessive wear on the engine and a decrease in operator comfort.

The second pillar is the operating pressure, i.e. the real force that the hydraulic system is able to generate. In practice, it is the pressure that determines whether the hydraulic motor will give out its full torque or whether it will only remain on paper. The 160-240 bar range is no luxury today - it is often the bare minimum when working in clay, gravel or cohesive soils. The third piece of the puzzle is oil flow, which is responsible for speed. Too low a flow rate means slow, jerky operation, too high a flow rate means excessive heating of the oil and a decrease in the life of the hydraulics. The key, therefore, is to match the absorption capacity of the drill motor to the real capabilities of the excavator pump, not the other way around. It is also worth remembering that the hydraulic drill rigs available from Techna Poland do not require a separate engine - they have a built-in hydraulic motor which does not operate independently, but is fed directly from the hydraulic system of your excavator. This solution simplifies operation, reduces the risk of errors and allows you to exploit the potential of the machine you already have.

Engine unequal - why an orbital can cope in clay and a geared one ends its life quicker than a drill bit

If there is one mistake that is regularly repeated when buying a drill rig, it is to underestimate the type of hydraulic motor. At first glance, 'a motor is a motor', but in practice, design differences determine whether equipment will last thousands of hours or end its life after one season. Orbital (gerotor) motors are the standard in professional hydraulic drill rigs today. Their compact design, high torque at low speeds and resistance to overloading make them ideal for clay, silt or gravel, where resistance changes with each layer of soil. This is why models based on BMR, OMR, OMS, BMS or OMT solutions are the most common in work equipment designed for tough conditions.

In contrast, it is worth making it clear: gear motors are not the solution for hydraulic drill rigs. Although tempting in price and simple in design, they do not tolerate prolonged axial loads, cannot cope with sudden jumps in resistance and wear out rapidly in continuous operation. The result? Torque loss, leaks, noise and costly servicing. Piston motors, on the other hand, offer high precision, but their price and sensitivity to contamination make them a rare practical choice for typical excavator-mounted drills. Therefore, if you want durability and predictability, an orbital motor with a planetary gearbox is a choice that simply makes sense. Importantly, Techna Poland's hydraulic drill rigs are complete - they have an integrated hydraulic motor, adapted to work with the excavator system, without the need for additional modifications or external drive.

Excavator weight versus real working conditions - how do you select a hydraulic motor so you don't tilt the machine and jam the hydraulics?

Selecting a hydraulic motor in isolation from the weight of the excavator is a straightforward route to problems that only come out in the field. A rig that is too powerful on a lightweight machine results in tipping, loss of stability and unnecessary stress on the arm and swivel. Conversely, too weak a configuration on a heavy excavator means wasted equipment potential and increased working time. In practice, the weight of the excavator determines not only the maximum torque, but also the safe range of drilling diameters. For 1-3 tonne machines, drill rigs with a torque of 2000-3500 Nm are a sensible choice, for 4-6 tonne excavators 6000 Nm, and with 8-12 tonne machines the real work only begins with torques of 8000 Nm and above. These are not 'stock' values - they are real numbers that affect the stability and life of the whole rig.

The hydraulics of the excavator are equally important, as even the best engine will not work properly if the oil flow and pressure are not within its optimum operating range. Too much engine absorption relative to pump capacity results in slow drilling and overheating of the oil, which in turn leads to accelerated seal wear and reduced system efficiency. It is therefore crucial that the drill rig is matched to the excavator you already own, rather than for hypothetical 'future' applications. It is worth noting at this point that the hydraulic drill rigs in Techna Poland's range are designed as attachments mounted directly to the excavator, with an integrated hydraulic motor that uses the machine's existing oil system. This means fewer complications, greater compatibility and real control over operating parameters in everyday conditions.

Sand, clay, gravel or rock? See how soil type changes the requirements for the hydraulic motor and the entire drill rig

Soil type is a factor that dramatically changes the requirements for the hydraulic motor, even with the same excavator and the same drilling diameter. Sand is relatively easy to handle - smooth operation and stable rotation are important here, and lower torques are completely sufficient. The situation is completely different in clay and loam, which can 'catch' the auger and generate enormous resistance. In these conditions, torque below 8,000 Nm quickly proves inadequate, and the lack of adequate pressure leads to jerky operation and overloading. Gravel, on the other hand, requires a compromise - here both torque and the engine's ability to withstand varying loads, which appear suddenly and without warning, are important.

The highest demands, however, are placed on rock and concrete, where, without the right rock-cut blades and high torque, drilling turns into a battle with physics. In such conditions, there is no room for half-measures - a planetary gearbox, robust seals and stable hydraulic performance are an absolute must. It is also worth remembering that the choice of motor is only part of the system, as the auger, the length of the drill bit and the type of teeth, which must be matched to the ground, are equally important. Poorly matched teeth can destroy even the best motor in record time.

That's why, if you want to make sure your equipment can cope with real-world conditions, it's worth reaching for complete hydraulic excavator drills, such as those available from Techna Poland - with a pre-selected, built-in hydraulic motor, adapted to the excavator's system and ready to operate without additional compromises.

FAQ

Is it possible to select a hydraulic motor "to spare" in order to make the drill rig more powerful?
In practice, oversizing the motor often leads to stability problems in the excavator and overloading the hydraulics. It is better to match the torque to the real weight of the machine and the working conditions, not to theoretical applications.
How do you know whether the excavator hydraulics can cope with a particular drill rig?
Two parameters are key: the maximum operating pressure and the available oil flow from the pump. If these are not within the operating range of the drill rig, even a good motor will not reach its capacity.
Is speed of rotation important when drilling?
Yes, but only in combination with sufficient torque. Too fast a speed with low torque will cause the auger to 'slip' instead of really digging into the ground.
Why are orbital motors better for drill rigs than gear motors?
Orbital motors withstand variable loads and prolonged low-speed operation better. This makes them more durable and predictable in difficult soils such as clay or gravel.
Will one hydraulic motor work for all types of soil?
Not really - different soils require different torques and working attachments. This is why it is important that the motor and the entire drill rig are selected for the specific working conditions.
Is a drill rig with an integrated hydraulic motor a better solution?
An integrated motor eliminates the risk of errors in drive selection and simplifies operation. The whole set-up is factory-fitted to work with the excavator's hydraulics, which increases durability and comfort.