Abstract
RESULTS of tests carried out on British-grown poles suitable for transmission lines have been reported (Electrician, Jan. 22). The tests were made to measure the deflexion of the poles, rigidly supported at 5 ft. from the butt, for any given loading ; up to the ultimate load, applied at 2 ft. from the top of the pole; to obtain a value for their ultimate breaking load, and to calculate the average value of fibre stresses. The poles tested were 36 ft. long by 11½ in. diameter at 5 ft. from the butt, with an average diameter of 8½ in. at the top. An analysis of the test results shows the deflexion for any given loading is much greater for Scots pine than for larch poles. On the other hand, the larch has a much greater ultimate strength, requiring an average load of 4,443 lb. compared with an average of 2,800 Ib. for Scots pine. Other things being equal, it is apparent from these tests that, from a strength point of view, larch poles are much better for transmission line supports than Scots pine. The ultimate fibre stress of larch is much greater than that of pine, being of the order of 10,500 lb./sq. in., as against 6,500 lb./sq. in. in the case of pine. The figure for Scots pine is well below the generally accepted figure of 7,800 lb./sq. in. for Baltic fir.
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Larch and Scots Pine Poles. Nature 151, 194 (1943). https://doi.org/10.1038/151194b0
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DOI: https://doi.org/10.1038/151194b0