Rock drill

A rock drill including

• an impact piston;
• a fluid system for driving the impact piston;
• a stroke length adjustment mechanism including at least one element moveable to vary a stroke length of the impact piston;
• structure defining a chamber such that a back pressure from a rock face is applied to fluid in the chamber;
• and
• wherein the chamber is fluidly connected to the stroke length adjustment mechanism such that the moveable element(s) is driven by the fluid, to which the back pressure is applied, to vary the stroke length in response to the back pressure.

A rock drill including

• an impact piston;
• a fluid system, including fluid paths, for driving the impact piston;
• a stroke length adjustment mechanism including at least one element moveable to reconfigure the fluid paths to vary a stroke length of the impact piston;
• structure defining a damping chamber such that a back pressure from a rock face is applied to fluid in the chamber;
• and
• wherein the chamber is fluidly connected to the stroke length adjustment mechanism such that the moveable element(s) is driven by the fluid, to which the back pressure is applied, to vary the stroke length in response to the back pressure.