ENGINES BY THE HUNDRED

Dominion, Volume 29, Issue 198, 19 May 1936, Page 9

ENGINES BY THE HUNDRED

Power For Empire FlyingBoats The works of the Bristol Aeroplane Company, which were enlarged by half about a year ago and have now doubled their manufacturing space,- are engaged on a piece of production for commercial flying that might have been thought impossible in the midst of military orders, writes the aeronautical correspondent of “The Times.” Imperial Airways need 116 Pegasus engines for the Empire flying-boats now being built at Rochester, and another 40 spare engines for substitution when overhauls are in progress. The Bristol company has undertaken to deliver them punctually, and in the hum of the shops and the roar of the test benches is ample assurance that the production schedule will be maintained. In the midst of the biggest volume of business ever accepted by this firm for the R.A.F., the time of men and machinery is being used to supply the commercial flying-boats with engines which, in efliciency and durability, should serve most of the lifetime of the boats. Just as the boats should be the most advanced things of their day, so the engines, already tested beyond the possibility of doubt, should be fit for hundreds of thousands of miles. They represent the latest and finest of their series of radial engines, so improved step by step that the output of each cylinder is 130 per cent, greater than it was 15 years ago. Epoch in Engine Design. It is not simply that the latest Pegasus yields 920 h.p. for the take-off and can turn most of that into thrust through the variable-pitch air-screw; that by means of deep, closely-set fins, sodlum-cooled valves, and stellited valves and seats, it is proof against the minor evils of “doped” fuel and high exhaust temperatures; or that by careful design of pistons, piston rings, and cylinder barrels, oil and petrol consumption is low and the life of the cylinder is long. The outstanding characteristic of this latest Pegasus is its promise to march with the times. It embodies the advances in engine design which mark an epoch and it can embrace at need the few outlying improvements with which that epoch may close.

This engine is fit to use the leaded fuel which allows the very high output without the risk of detonation. It absorbs without a knock the 51b. to the square inch of "boost” which gives it so fine a performance. If in the course of the new flying-boat’s life it should be desirable to turn over to fuel of a still higher anti-knock rating, tlie Pegasus X will probably be able to stand the harder conditions that will impose. Finally it is equipped with a type of ring cowling which carries the reduction of drag almost to the limit. Tills is based on the comparatively recent discovery that to admit more cooling air than is necessary to tlie cylinders beneath the cowling is to increase drag. Regulating Air Flow. Tlie skirt of this ring cowling is arranged ingeniously so that it may expand or contract, rather like the mouth of a sponge-bag, to regulate the flow of air over the cylinders. Tlie skirt consists of a number of metal plates, the sides of which may move in the grooves of frame members and also on hinges set on the ring from which they depend. They may move outward like flaps and toward each other, and the widening of the circumference is thus obtained without making gaps in it to spoil the smooth flow of the cooling stream. This is an improvement oil the hinged panels hitherto tried with the same object and. if the mechanism survives the hard handling of regular service, it should be a great success.

This engine is a fine culmination of a great series. It is faced some time in the future by the competition of the new sleeve-valve scries. Whatever the result of that may be. the Pegasus will bo remembered as a remarkable example of what its typo might achieve In these works some 8000 men are engaged daily In three shifts. The proportion concerned with engines for the flying-boats is small, but their products will probably fly over all live Conti uents and over most of tlie seven sens. The quality of the work which is being put into them is evidently worthy oiLtheir destiny, _