How to choose a turning machine: 8 criteria for an EPC supplier

The rotary tool is not selected based on a single parameter. The torque determines how the machine can handle the soil profile, but the engagement on a specific construction site is determined by the same factors as the compressive force, the length of the blade, the width of the machine, and the method of installing the screw. The following overview summarizes the eight criteria in the order in which we consider them when selecting a machine with our suppliers, and shows where the Glentor A70, B80, C65, and D50 models differ from each other.

1. Torque and rotational speed — always two numbers, not one

The high torque at low speeds is used to overcome a hard layer — a compacted substrate, gravel, weathered rock. The low torque at high speeds, on the other hand, accelerates the rotation in a homogeneous soil where resistance is no longer a problem and it’s all about time to the point.

Torque is the most frequently cited parameter and the one that is most often misinterpreted. What matters is not the maximum value itself, but the torque/rpm ratio, because the machine operates in two different modes.

Model	Working mode	Quick mode
A70	7 000 Nm / 13 rpm	3,000 Nm / 45 rpm
B80	8,000 Nm / 20 rpm	2,000 Nm / 85 rpm
C65	6,500 Nm / 20 rpm	2,000 Nm / 85 rpm
D50	5,000 Nm / 37 rpm	—

The A70 also has a third mode at 6,000 Nm/20 rpm. The B80 combines the highest torque in the range with high speeds in the fast mode — which is why it is the most frequently chosen model for projects where different soil profiles are alternated.

What to ask: not „how many Nm the machine has“, but „what torque it has at the speeds at which I will actually be working on my site“.

2. Pressure force — a parameter that determines the rotation

The moment the screw rotates, the compressive force pushes it into the ground. In cohesive clayey soils and when installing over a compacted layer, it is the pressure that determines whether the screw will even take hold.

The difference within the range is crucial: the A70 has 5,000 N, the B80 and C65 have the same value 12,000 N, That is more than twice as much. The D50 as an accessory has a lifting capacity of 6,350 N.

If the project involves laying over asphalt, paving, or compacted subgrade, the compressive force is more important than the last thousand newtonmeters of torque.

3. Maximum length of screw and pilot

The length of the loop is a strict limitation — shorter loops are better than longer ones, but the opposite is not true.

Model	Max. screw length	Max. length of the pilot
A70	2.4 m	—
B80	2.5 m	—
C65	3.5m	4.3 m
D50	2.5 metres	—

For most FVEs, wood structures and furniture, 2.4–2.5 m is sufficient. However, once the project requires longer beams — soft and damp profiles, where load-bearing capacity is sought deeper, soundproof walls, control columns or pilot lights — the C65 is the only choice in the range.

4. Weight, transport and loadability of terrain

Weight affects two things at once: how the machine gets to the construction site and what it does with the surface on which it stands.

A70 — 1 700 kg: The simplest transport, the lowest pressure on the surface. The choice for less accessible places, soft or modified surfaces.
B80 — 2 480 kg: universal compromise, sufficient stability for higher pressure.
C65 — 3 050 kg (drilling) / 3 250 kg (with hammer): highest stability, but requires careful handling and rugged terrain.
D50 — 480 kg: It is not a separate machine; it is an auxiliary device without its own motor, powered by the hydraulics of the main machine (200 bar / 70 l/min).

The D50 changes the economics of selection: if a company already operates a carrier with adequate hydraulics, it does not purchase the entire machine, but equipment for a fraction of the weight and acquisition cost.

5. Dimensions and accessibility of the construction site

The width of the machine is an inconspicuous parameter, but it will exclude the machine from the entire segment of projects.

The A70 has a transport width 902 mm, B80 980 mm. Both will go through the standard alley between the parking rows, the regular gate and the intermediate section in the set. In projects in the development area, in pedestrian zones, in vineyards or between existing structures, width is just as important as moment.

The relevant parameter is the tilt of the sled: A70 and B80 ±18° / 8°, C65 and D50 ±15°. This determines how steep a slope the machine can handle without the rocker turning sideways.

6. Front-versus-side installation

This is the most overlooked criterion and yet it determines entire segments.

Front-loading (A70, B80, D50) means that the rod is placed in front of the machine. The machine must be positioned facing the point — it needs free space in front of it.

Lateral foundation (C65) allows the screw to be rotated on the side of the machine. In practice, this means that the machine can move along a line and rotate just next to an obstacle, a curb, a kerb or a wall — without turning and without the need for free space in front.

In linear structures, in a narrow sidewalk profile or along an existing structure, side-mounted foundations are the reason why C65 is chosen, even though it has a lower nominal moment than B80.

7. Drilling, DTH pre-drilling and boring

Three different technologies that solve three different situations:

Drilling — basic mode of all models.
DTH drilling — available on A70, B80, C65 and D50. Necessary where there is a hard cover over the load-bearing layer: asphalt, concrete, weathered rock.
Drilling with a hydraulic hammer — only C65, The MTB36 hammer with a striking energy of 900 J and a frequency of up to 900 strokes per minute. The C65 can also be supplied as a single-purpose punching machine.

If the project portfolio includes threaded profiles or pilot screws in addition to conventional bolts, the C65 is the only model that can handle both with one machine.

8. Control, documentation and service

Three operational criteria that will be manifested only after purchase:

Remote control. The operator is not on the machine — he/she is working outside the danger zone and with a view to the rotating point. Working near vehicles, traffic or existing structures is not a comfort factor, but a prerequisite for safe execution.

Telematics unit and recording. It records the moment and depth of each screw. The output is a document for the structural engineer, the investor, and the building manager — and in public contracts it is often a directly required component of the handover.

Service and availability of parts. Glentor machines are manufactured in the Czech Republic and serviced in-house; the hydraulics are based on Danfoss/Eaton and Linde components, and the motors are Hatz and Kohler. The company holds ISO 9001:2015 certification and is an authorized system partner of Eaton for the Czech Republic and Slovakia.

Decision table by project type

Project type	Recommended model	The decisive parameter
Solar park	B80	moment 8,000 Nm, fast mode 85 rpm
Agrivoltaics in perennial crops	B80, A70 into narrow intermediate position	width 902 mm, inclination ±18°
Solar carports	B80, C65 on concrete	pressure 12,000 N, DTH pre-drilling
Timber buildings and modular houses	A70 or B80	weight, availability of space
Linear structures	C65	side mounting, pilot 4.3 m
Municipal furniture	C65, A70 to the pedestrian zone	side mounting, width
Agricultural structures	C65, D50 for fencing	screw length 3.5 m
Warehouse buildings	B80, C65 on a hard surface	pressure, point of loadability
Battery storage	B80	point load on the container

Comparison of Glentor models

Parameter	A70	B80	C65	D50
Torque	7,000 Nm	8 000 Nm	6,500 Nm	5,000 Nm
Downward force	5,000 N	12,000 N	12,000 N	6 350 N
Max. screw / pilot	2.4 m	2.5 metres	3.5 / 4.3 m	2.5 metres
Mass	1.7 tonnes	2,480 kg	3,050–3,250 kg	480 kg
Width	902 mm	980 mm	side-mounting	1 040 mm
Motor	Kohler ECH980, 28 kW	Hatz 3H50TICD, 43.7 kW	Hatz 3H50TICD, 43.7 kW	without motor
Hydraulics	320 bar / 47 l/min	280 bar / 65 l/min	220 bar / 65 l/min	200 bar / 70 l/min
Founding	front	front	side	front
Hydraulic breaker	no	no	MTB36, 900 J	no
Carriage elevation	±18° / 8°	±18° / 8°	±15° / 8°	±15°

The three most common mistakes when choosing

Selection based on one number. A machine with the highest torque is not automatically the most powerful on the given job. The C65 has a lower torque than the B80, but thanks to its side loading and longer reach, it can handle projects where the B80 won’t reach the point.

Omission of the supporting force. The difference between 5,000 N versus 12,000 N is decisive in cohesive soils and when establishing over compacted layers — often more than the difference in moment.

Selection without knowledge of the soil profile. Without a geotechnical base, the choice of machine is an estimate. Before making a decision, we recommend having at least an orientation probe — and, in projects where load-bearing capacity is proven, following the procedure described in the project documentation. Eurocode 7.

What is cheaper? Comparison of cost items

What torque do I need for a solar park?
For common soil profiles of solar parks in the Czech Republic, the torque of 8,000 Nm is recommended, namely the B80 model. However, the decisive factor is the combination of torque and rotational speed – the B80 offers 8,000 Nm at 20 rpm for harder layers and 2,000 Nm at 85 rpm for rapid rotation in homogeneous soil. We recommend making a final choice based on a geotechnical survey of the site.
What is the difference between front and side screw mounting?
In face-on laying (A70, B80, D50), the screw is laid in front of the machine, so the machine needs free space in front of it and must stand with its front facing the point. Side laying (C65) allows the screw to be turned on the side of the machine — the machine can then move along the line and work close to the ditch, curb or wall. For linear constructions and work in a narrow profile, side laying is a decisive advantage.
When do I need a hydraulic hammer and when is it enough to just unscrew?
The rotary hammer is suitable for ground drilling in most soil profiles. You need a hydraulic hammer where driven profiles or pilot holes are installed — typically in linear structures, noise barriers, or in profiles where rotary drilling is inefficient. The MTB36 hammer with a striking energy of 900 J is only available in the C65 model, which can also be supplied as a single-purpose drilling machine.
Is the D50 a full-fledged alternative to a standalone machine?
No, the D50 is an auxiliary drilling rig without its own motor — it is powered by the hydraulics of the carrier machine and requires 200 bar at 70 l/min. For a company that already operates an appropriate carrier, this is the most economical way to drill the screws into holes up to 2.5 m in diameter. For standalone operation, one of the self-propelled models A70, B80 or C65 is required.
How do I know that the machine is suitable for a hard or rocky surface?
Three things determine the success: sufficient torque in the low-speed mode, the availability of the DTH drill bit and the compressive force. For hard profiles we recommend B80 or C65 — both offer a compressive force of 12,000 N and the DTH drill bit, C65 additionally includes a hydraulic hammer for cases where drilling is not continuous. In weathered rock, a pre-drill test is always carried out in advance.
Does the operator of a drilling machine need special authorization?
A self-propelled drilling rig is not a road vehicle, so the operation itself does not require a driver's license. A driver's license corresponding to the category is required for transporting the machine on a trailer or semi-trailer. The operator must be trained on the specific model — Training and service support provided by Glentor.

Where to continue

Technical and normative background of rope-based construction: Eurocode 7 and ground screws
Comparison of foundation technologies: Ground screws vs concrete foundations
Solutions based on the type of project: Use of Glentor ground screws
Service, spare parts and operator training: Service and Support