Why adjust the stroke?
The guide explains that a stroke-adjustment device changes piston travel to produce different combinations of impact energy and frequency for different rock conditions. Designs differ between machines, so the adjustment of one example should not be assumed to apply to another.
The three-position COP1238 example
The guide describes an external, three-position stroke adjustment on the COP1238. In its example a shorter stroke corresponds to lower impact energy and higher frequency, while a longer stroke corresponds to higher impact energy and lower frequency. This summarizes the example's operating principle; it is not an adjustment instruction or a performance guarantee for an individual machine.
Selection and parts matching
When comparing equipment, provide the drilling requirements, rock conditions and complete rock drill model and version. For a piston, valve or cylinder, use the old part number and physical component and verify against the manufacturer's documentation. COP1238 is a structural example, not evidence that another model uses the same parts.
Source: GLOBMACH Hydraulic Rock Drill Parts Selection Guide, printed pages 67–68.