I The standard K4s Pacific type of locomotive was offered as the subject for consultation on streamlining to improve its speed and appearance. The Pennsylvania Railroad Company operate some 2,500 of these loco motives, so it was natural that the specifications for the I new designs should stipulate that in streamlining, - everything in the existing locomust be clearedWhen comparing the new design with, say, the Silver Jubilee, this point should be kept in mind. The first stage in the solution of the problem at which results began to appear was the testing of clay models, seven feet long, in the wind tunnel of New York University's Aerodynamic Laboratory. This was a process which was carried on over a period of months; clay was the substance chosen for modelling because it was easy to make alterations where the tests proved that these were needed. igoo i9o; 1910 J9I4 1918 1925 i928 1951 1934 The development of streamlining again presented in the form of a pictorial chart. Railroad Company, a concern which builds as well as t runs its locomotives. Observations of the air flow were made by the use of silk threads and smoke bombs, as well as by photo graphs and sketches taken while the tests were in progress. Twenty-four models were built and dis carded in favour of four, from which the final design was selected. Comparative tests were made for wind resistance with the model of one locomotive, with tender and one coach. Under these conditions, at wind tunnel speeds of 100 m.p.h., air resistance was reduced from 890 h.p. in the standard model to 600 h.p. with the streamlined design. This represents, at maximum speeds, of 90 to 100 miles per hour, by reduction of air pressure, a saving in speed of nearly 300 h.p. It is interesting to compare the two locomotives side by side and notice the different factors which have contributed to this success. Since the specifications stated that the existing loco motive must be covered as it stood by the new model, the obvious method of achieving a streamline by cut ting back the smoke box was scratched. Instead, therefore, the streamlining was achieved by doming out the front, removing the lamp and setting it in the centre of the dome. This part of the work was carried out in sheet steel. Special methods of providing for smoke lift were also worked out which will be dealt with later. Meanwhile, wherever desirable, other features of the standard form were retained. Changes were not made for the sake of making them. The separation between the front end of the boiler and the skirting in front of the pilot and round the cylinders was retained. This 178 was proved to give uniformity of pressure in the air

Industrial Arts en | 1936 | | page 20