THE TRANSMISSION GALLERY
Here we bring you Construction Bulletin no. 5, dated September 1951 and published by British Insulated Callender's Construction Company Ltd., the contractors responsible for the building of the Holme Moss mast.
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High on the moors, 1,750 feat above sea level, nine miles south-west of Huddersfield lies Holme Moss, the bleak site of the B.B.C.'s Northern Television Transmitter Station.
At the head of the 750 feet mast designed and erected on this site by British Insulated Callender's Construction Co. Ltd. to B.B.C. specification. is the television aerial - 2,500 feet above the sea. Holme Moss is the most powerful television station in the world. and brings television within the reach of eleven million people in northern England.
The mast at Holme Moss is similar to the structure built for the B.B.C. at Sutton Coldfield and the general features have been already been described in one of our previous publications We shall. therefore pay special attention to those features of the mast which are of interest owing to the exceptional nature of the site.
Holme Moss is subject to extremely severe winter weather conditions and to meet these the mast was designed to withstand maximum wind velocities ranging from 85 m.p.h. at ground level to 125 m.p.h. at the top, and in addition ½" thick covering of ice was allowed for on every member of the structure. The moor is covered with moss-peat to depths of up to 12 feet and masses of this unstable material had to be cut away to expose firm ground in which to bed the foundation and stay-anchorages. To guard against the deleterious affects of peat-water acids, concrete mixing was carefully controlled and aggregates finely graded.
The mast rests on a reinforced concrete foundation block designed to carry a maximum of 350 tons. It is supported at points 200, 400, 600 and 710 feet above the ground by three lock-coil steel wire stay ropes, displaced in plan by 120° at each supporting point. The stays are anchored at ground-level to blocks at distances of 175, 350 and 500 feet from the foot of the mast.
At Holme Moss a new type of rigging was used to provide means of adjustment in stay lengths and tension. This consists of two long screwed rods, pinned to steelwork in anchor blocks. and holding between them an adjustable cross head to which stays are attached. Initial tensions in the stays are of the order of 8 tons and great care had to be exercised in obtaining a correct balance of tensions under particularly difficult conditions
Painter Bros. Ltd. Hereford. supplied the fabricated steel and Wright's Ropes Ltd., the steel stay ropes. John Laing & Son. Ltd., were sub-contractors for the foundations.
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