Hydraulic Ram

The Department's description

Exterior description and setting

600mm wide concrete channel served by a 60mm diameter pipe crossing the River Roe at a high level near Largy Bridge at the Dogleap, Limavady. The channel moves 6-7 metres inland before turning to run parallel with the river. To the land side the ground level falls away leaving a concrete structure six metres high when the structure re-emerges at the river, 20 metres downstream. At this point there are cast iron railings and more recent timber fencing preventing closer inspection.

Historical information

Built by Miss Dorothy Robertson of Dogleap House (HB02/13/007) in 1924 utilising water carried across to her farm historically to mill building (HB02/15/008) via a timber aqueduct from the mills at Largy Green on the opposite bank. This aqueduct was described and drawn in the Ordnance Survey Memoirs of 1833-5 as ‘wooden aqueduct built by Robert Thomson millwright’. The concrete channel served a small hydro electric turbine generating 20-25 brake horse power on a head of 24 feet and a 12 kilowatts, 220 volts direct current generator both housed in the drop at the end of the run. In 1933 the electricity company on the opposite bank needing more water power, agreed to supply Mrs Robertson with free electricity and removed the aqueduct diverting the water into a new generator. The present pipe was installed on the route of the aqueduct to provide sufficient head of water to operate her hydraulic rams. A hydraulic ram is ‘a simple type of pump which uses kinetic energy of a moving column of water to pump a part of that water column to a greater height than that of the water supply’. (J Stevenson).

References:

Electricity Survey Memoirs of Ireland Vol. 9 p.52.
J Stevenson - Electricity from the Red River (NIE) p34.
IHR (Dogleap) 1680

Criteria for listing: architectural interest

Not listed

Criteria for listing: historic interest

Not listed

Evaluation

A reinforced concrete structure interesting for its association with the generation of hydro electric electricity on the River Roeand at also for the dramatic association of the man made structure with the natural rocks of the Dogleap. Seen from the south bank of the river opposite, the irregular rocks are suddenly squared off by an ivy covered concrete projection which with weathering looks part of the outcrop. On the north side nature is secondary to the ruthless straight concrete line rising slowly from the forest floor stopping abruptly without any apparent warning. Interest includes suspended pipe over river , millrace and drop to river.