Krakbogruvan

After a walk through the Tilas adit, one emerges into Krakbogruvan.

The mine was worked from the mid-1750s, intermittently, until 1905.
It was the second-to-last mine in operation on the Högberg field.
At the time of closure, the mine had a depth of approximately 103 metres.

Construction and Pump Line

The drawing in image 1 shows an impressive timber construction above the mine:

The construction supports the pump line where it changes direction and continues down into the mine.
The change of direction takes place over a rocker arm, known locally as a ”doppare”.
The section of the pump line that descends to the bottom of the mine is called the storstång (main rod).
The pump power came from Braskefallet at Flintkärret, approximately 1,200 metres from the mine.

Definition from Jernkontoret’s Mining Lexicon

Storstång (Schachtgestänge) in water pump systems is the rod hanging from the rocker arm that extends all the way down into the pump shaft, where the smaller suction rods are connected. See also: Bij Tab. III Fig. 1, H and Tab. IV Fig. 1, H.

The Mine’s Depth and Subdivision

”In 1754 the depth of the mine was 13 fathoms (approx. 23 m).”

”Krakbogruvan: At surface level the ore must have been quite substantial, as the passage to a depth of 3 fathoms and a width of four fathoms has been worked over a length of 47 fathoms. From the aforementioned depth, the mine is divided into 4 sinkings with intermediate pillars of 2 to 3 fathoms.”

Transcript: The Origin and Development of Swedish Mines, J. O. Carlberg, Professor of Mining Science.