{"id":20202,"date":"2026-01-30T14:18:32","date_gmt":"2026-01-30T13:18:32","guid":{"rendered":"https:\/\/www.darda.de\/?page_id=20202"},"modified":"2026-01-30T14:18:32","modified_gmt":"2026-01-30T13:18:32","slug":"rack","status":"publish","type":"page","link":"https:\/\/www.darda.de\/en\/knowledge\/rack","title":{"rendered":"Rack"},"content":{"rendered":"
\n

The rack is a central machine element that converts rotational motion into linear motion. In the practice of demolition and cutting technology \u2013 from concrete demolition and special deconstruction<\/a> to natural stone extraction \u2013 it appears as a compact linear actuator, as an adjustment or positioning mechanism, and as a robust guide. Even in tools and fixtures that work with hydraulics, the combination of pinion and rack can take over functions such as fine adjustment, synchronization, or mechanical locking. This functionally expands the application range of equipment like concrete demolition shears as well as stone and concrete splitting devices in tough day-to-day construction site use \u2013 without making the design unnecessarily complex or maintenance-intensive.<\/p>\n

Definition: What is meant by a rack<\/h2>\n

A rack is a bar or strip profile with teeth distributed along its length that mesh positively with a gear (pinion). This rack-and-pinion<\/em> converts the pinion\u2019s torque into a force along the rack. Important parameters include module (m), tooth form (usually involute), tooth width, quality\/tolerance, contact ratio, backlash, and surface hardness. Depending on the design, a rack is suitable both for precise positioning and for robust power transmission with high feed forces \u2013 for example, for opening and closing tool jaws, setting up stops, or traversing smaller assemblies.<\/p>\n

Function and design of the rack<\/h2>\n

The basic principle is pairing a linear toothing (rack) with a round counterpart (pinion). When the pinion rotates, the rack travels proportionally to the pinion\u2019s pitch diameter circumference: per revolution, the stroke equals the circumference of the pinion\u2019s pitch circle in the idealized case. The transmittable force along the rack is determined by the pinion\u2019s tangential force and the flank engagement, with friction, lubrication, tooth form, and surface finish being decisive.<\/p>\n

For rugged applications in dusty, abrasive environments \u2013 typical in concrete demolition, rock removal, or building gutting \u2013 spur-toothed racks with inductively hardened flanks are often used. They combine easy installation, high resilience, and well-manageable adjustment of backlash and alignment.<\/p>\n

Use in demolition and cutting technology<\/h2>\n

In equipment and fixtures used in demolition practice, racks enable compact, reliable linear movements \u2013 alone or in combination with hydraulic power packs and cylinders.<\/p>\n

Concrete demolition shears: setting, synchronizing, securing<\/h3>\n

While the main closing of concrete demolition shears is usually hydraulic, a rack can take on supplementary tasks: for instance, backlash-free positioning of stops, synchronization of additional guides, or setting up preload and end stops. A mechanical rack with a mild transmission ratio enables sensitive adjustments that remain in place even when the hydraulics are depressurized. This is particularly helpful when positioning before a separation cut or when taking a controlled initial bite on reinforced concrete edges.<\/p>\n

Stone and concrete splitters: feed and positioning<\/h3>\n

In splitting work in concrete or natural stone, wedges are driven hydraulically. Around the actual splitting point, however, auxiliary movements are often required: aligning clamping frames, precise follow-up of guide shoes, or reproducible setting of split heights. Rack drives can move these auxiliary axes with positive, slip-free engagement, even when dust, moisture, and chips act on the mechanism.<\/p>\n

Rock demolition, tunnel construction, building gutting, and cutting<\/h3>\n

In mobile fixtures or carrier systems used in deconstruction and tunnel advance, racks serve as robust travel units \u2013 for example, for lifting and setting down smaller attachments, for adjusting cutting or gripping widths, or for locking mechanisms that, independently of hydraulics, enable mechanical self-locking or a defined end position. This allows processing steps with concrete demolition shears or multi cutters to be prepared safely and reproducibly.<\/p>\n

Advantages and limits of the rack drive<\/h2>\n