The machine substructure forms the static and dynamic base of mobile and stationary work machines in demolition, tunnel construction and rock excavation, as well as in natural stone extraction. It carries loads, transfers forces into the subsoil and decisively influences structural stability, precision and efficiency—e.g., when using concrete demolition shear or hydraulic rock and concrete splitters. A properly engineered substructure reduces wear, minimizes vibrations and increases process reliability during deconstruction, interior demolition and special demolition.
Definition: What is meant by machine substructure
Machine substructure refers to the entire load-bearing substructure of a machine—from the undercarriage (crawler or wheeled undercarriage) via frame, slew ring bearing and supports to setup and foundation measures. This also includes aids for load distribution such as bearing plates, sleepers or ground protection mats. The machine substructure mechanically connects the machine to the subsoil, absorbs operating and impact loads, limits overturning moments and ensures structural stability and tracking accuracy under changing ground and loading conditions.
Structure and components of the machine substructure
The configuration depends on machine type and operating environment. In concrete demolition and special demolition, carrier machines with crawler undercarriage dominate; for urban interior demolition, compact wheeled undercarriages are often used. In natural stone extraction and tunnel construction, robust crawler undercarriages with high ground clearance and large-area load distribution play to their strengths.
Typical elements
- Undercarriage/running gear: crawler undercarriage (track rollers, carrier rollers, tracks, idlers, drive sprockets) or wheeled undercarriage (axles, tires, hubs, steering)
- Frame and cross members: transfer forces into the ground, increase torsional stiffness
- Slew ring and slew ring bearing: transmit slewing moments, influence precision under lateral loads from concrete demolition shear
- Supports/dozer blade: increase structural stability, reduce overturning moments, serve as additional load distribution
- Setup aids: bearing plates, timber sleepers, steel spreader beams, ground protection mats
Load paths and moments
With high-force tools—such as concrete demolition shear, attachment shear or steel shear—the load paths run from the tool through boom and upper carriage into the slew ring and ultimately into the undercarriage. Lateral cutting and splitting forces generate overturning moments; the substructure must absorb these moments with sufficient structural stability without permitting excessive deformation or slippage.
Load-bearing capacity of the subsoil and load distribution
The best substructure loses effectiveness if the subsoil is insufficiently load-bearing. Load-bearing capacity, settlement behavior, moisture and frost condition determine the necessary measures for load distribution. In sensitive environments—such as on slab surfaces during special demolition—calculated surface load (kN/m²) and stability verification are essential.
Assessment of the subsoil
- Geometry: slope, flatness, steps and edges
- Material: soil class, compaction, load-bearing capacity of slabs and intermediate floors
- Actions: moisture, frost, heat, vibrations
Measures
- Use ground protection mats and bearing plates to reduce surface pressure (bearing pressure)
- Support with wide pads, lower the dozer blade, adjust boom position
- Route planning, load limitation and step-by-step working to minimize settlements
Influence of the machine substructure on concrete demolition and special demolition
When using concrete demolition shear, the quality of separation improves significantly with a steady, tip-stable stance. A stiff substructure reduces pendulum movements, enables controlled cut lines and protects the slew ring bearing and boom bearings. Hydraulic wedge splitters benefit from stable positioning because splitting wedges introduce forces more rectilinearly and crack propagation can be controlled more precisely.
Practical recommendations
- Perform lateral cutting operations close to the ground with the dozer blade lowered
- Select boom geometry so that the center of gravity remains as far as possible within the track/tire gauge
- On slab surfaces: verify allowable surface load (kN/m²), size load distribution mats
- Organize material flow to avoid slewing on the steepest gradient
Machine substructure in rock excavation and tunnel construction
In tunnel construction, impact loads, vibrations and transverse forces arise from extraction tools, attachment shear and rock splitting cylinders. Crawler undercarriages with a large contact area and durable running gear increase traction on debris piles. A low build height of the undercarriage reduces overturning moments on cross slope. Additional bearing points and wedges are useful to compensate for uneven invert surfaces.
Vibrations and structure-borne noise
A massive, backlash-free substructure damps vibrations and protects attachments. The maintenance condition of track rollers and bushings influences the transmission of vibrations to the upper carriage, hydraulic components and operating personnel.
Natural stone extraction: stability and precision
When splitting natural stone, reproducible crack paths are required. The more stable the substructure, the more controllably splitting forces can be introduced. The use of underlay material prevents the tracks from sinking into soft bedding—important for uniform split openings when using hydraulic wedge splitters.
Interior demolition and cutting in indoor areas
On intermediate slabs or in confined spaces, substructure and setup must be planned with particular care. Compact wheeled undercarriages support short maneuvering paths but require adequate load distribution to comply with slab load-bearing capacities. For concrete demolition shear, cutting torch or steel shear, control of tipping edges at the perimeter of openings is critical.
Power units and setup of mobile units
mobile hydraulic power units for hydraulic wedge splitters or attachment shear require a tip-stable, level stance so that vibrations do not transmit into hoses and couplings. Rubberized standing surfaces reduce structure-borne noise and protect substrates. Organized hose routing along load-bearing paths reduces tripping and crushing hazard.
Maintenance and inspection of the machine substructure
Regular inspections ensure function and service life. Play in slew ring bearings, worn track rollers or damaged tires impair precision and increase accident risks. A well-maintained substructure keeps the tools—whether concrete demolition shear, attachment shear or cutting torch—on the intended cut line and reduces energy losses.
Key inspection points
- Running gear components: track rollers, track/tire wear, tracking
- Slew ring: preload, lubrication, axial and radial play
- Supports: hydraulic tightness, support pads, cracks in the frame
- Bolted connections: tightening torques on load-bearing cross members
- Setup accessories: condition of mats, sleepers and bearing plates
Safety and organizational measures
Safety takes precedence. Stability verification, clear travel routes and coordinated lifting and cutting sequences are fundamental. Notes on legal requirements and standards may vary by region; it is advisable to consistently implement generally applicable protective measures such as barriers, load-bearing setup areas, load distribution appropriate to bearing capacity and qualified personnel.
Work organization
- Ensure communication between operator and signaler
- Keep swing areas clear, mark tipping edges
- Monitor weather and subsoil changes, adapt measures
Typical mistakes and how to avoid them
- Underestimated surface pressure (bearing pressure): leads to sinking and tipping tendency—countermeasure: mats and wider supports
- Lateral cutting loads without blade/support: increases slew ring bearing wear—countermeasure: support, adjust boom angle
- Wrong tire/track choice: insufficient traction—countermeasure: match tread and track width to the subsoil
- Insufficient maintenance: play in the substructure—countermeasure: regular inspection, lubrication, replace worn parts
Selection criteria for the right machine substructure
The choice between crawler and wheeled undercarriages, support concept and setup accessories depends on application, tool use and subsoil. Under high transverse loads—e.g., when cutting with concrete demolition shear on massive structural elements—a wide crawler undercarriage with a low center of gravity shows its advantages. For rapid relocations in interior demolition, wheeled undercarriages with suitable load distribution are sensible. In special demolition tasks, the combination of traction, build height, support capability and transport logistics is decisive.