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eylinders relining, and new pistons, valves, etc., should be fitted. The cost of renewals at this stage will amount to perhaps 15 per cent of the cost of a new engine, and the entire cost of reconditioning, includ- ing fitting, testing, etc., if made a matter of regular and well organized routine, may amount to from £50 to £60 per engine. Allowing, therefore, for three top overhauls to one major overhaul, the cost of routine repairs and maintenance should average from £100 to £120 per engine in four years, or say, £25 to £30 per annum. To this must be added perhaps an additional 30 per cent to cover the hazards of accidental breakdown; making a total of about £2500 to £3000 per annum for all engine re- pairs and maintenance in a ship of about 10,000 tons, in which the total installed horsepower is 7500, the actual shaft horsepower at full speed 5000, and whose seagoing average is 4000 hours, or say, 60,- 000 miles per annum, Not a very high figure, I think, more especially when consideration is given to the fact that throughout its whole life, the ship will never be out of com- mission for one minute for engine repairs, and that the routine over- hauls will maintain all the engines in new condition and at maximum efficiency until obsolescence, not age or wear and tear, brings their lives to a close, Undertaking the Maintenance In this connection I would mention that some of the manufacturers of high-speed diesel engines for road vehicles are already undertaking the entire maintenanee of their engines, including replacement with new en- gines when necessary, and including also the maintenance of all the en- gine auxiliaries, of the entire elec- trical equipment and batteries, at little more than the rate I have men- tioned. As to the maintenance cost of the electrical gear, I am not, I am afraid, in a position to offer any fig- ures, but since no batteries are in- volved, it is reasonable to suppose that it will be relatively very small. Within the engine itself, the lub- rication system will be exactly as in a road vehicle engine, that is to say all bearings will be fed by pressure in the usual manner, with the usual large-diameter drilled passages in place of oil piping wherever possible. Each engine of 100 horsepower will require approximately 8 gallons per minute for the dual purpose of cool- ing and lubricating the bearings, so that the capacity of the oil circulat- ing system should be about 200 gal- lons per minute, The fuel system should be similar to that of the lubricating oil, except of course, that no cooler is required. In order to ensure against gassing or air locks in the fuel pumps, it is always preferable to maintain a con- tinuous flow through them, but. of course quite a low velocity will suffice. As in the case of the lub- ricating oil, the circulation of fuei to each individual engine will be in- terconnected with the starting of the engine. In like manner, both the air intake and exhaust from each engine should be connected to ring mains, the latter of course water-cooled. With such a system, it may well be worth while to apply a super- charge and so raise the whole power of the plant by about 20 per cent, since this could be accomplished so easily by a single large centrifugal blower, The whole of the engine commis- sariat system will, of course, be oper- ated electrically, and all vital or vul- nerable parts should be in duplicate. The total power consumption of the engine auxiliary services, if in dupli- cate, will amount to somewhere about 50 horsepower or about 1 per cent of the shaft horsepower, exclud- ing supercharging, Although JI have reckoned on a normal maximum shaft horsepower of 5000 with ten engines engaged upon auxiliary services, and eight in reserve, it is probable that in most services four or five engines will suffice for the auxiliary work when at sea, so that as many as seventy engines could at times be pressed into the work of propulsion, giving a normal shaft horsepower of 6000. If supercharged to increase the out- put by 20 per cent, and setting aside the use of two engines to drive the blowers, a maximum of just over 7000 shaft horsepower could be attained in emergency with all generating units in operation and supercharged. Noise.—To the marine engineer’s ear, the continuous high-pitched roar of the high-speed engine is perhaps quite as distressing and almost ag unnerving as is the gasp and shud- der of the slow-speed type to earg accustomed to the former, There is, however, this essential difference, that whereas by proper insulation, the roar of the high-speed engine can be smothered, more especially so when the air intake is muzzled, that of the slow-speed, emanating as it does from the hurtling about of un: balanced tons of metal, cannot be isolated in this way but reacts throughout the ship. In Soundproof Wooden Box In order to cope with the noise difficulty, and at the same time to discourage any meddling with the engines by those on board, I would propose that each generating set or pair of generating sets should be en- closed entirely in a double-walled wooden soundproof box, well ventil- ated by connection to deck ventil- tors, or even a false funnel. This box will rest on the ship’s structure en- tirely out of contact with the engine or its mounting. A glass window should be provided in each box through which an occasional visitor MARINE REVIEwW—March, 1934 to the engine room can sée the com- mutator of the generator, a_ ther- mometer on the exhaust pipe, possib- ly, though not necessarily, an am- meter, and the crankcase air vent; the amount of smoke from the lat- ter will reveal the general condition of the piston rings and indicate when the time is drawing near for @ top overhaul. Thus enclosed, the generating sets will sound like bees on a summer’s aftérnoon, and the solitary engine room clerk will be able to smoke his pipe of peace. Since the fuel injec- tion pumps will have been calibrated ashore and set to give a maximum delivery sufficient for 100 horse- power only, at 1600 revolutions per minute, there can be no possibility of overloading, and I would insist that any adjustment to the fuel pumps or governors be sealed, lest some engineer cracksman succeeds in breaking and entering the engine’s cell, All engines should, I suggest, be started and stopped by means of a remote control, either from the main switchboard or the _ bridge. Lights on the switchboard and in each engine cell will indicate which engines are in operation at any mom- ent, The engine room clerk will be expected to keep records of the num- ber of hours run by each generating set, of the total fuel and oil consump- tion, and it will be his business also to take an occasional stroll around and to chalk-mark for the benefit of the engineer ashore, any set which is persistently showing an exhaust temperature much above the average or which is showing excessive fum- ing from the crankcase breather. Mounted in Trunnions I would propose that each com- bined engine and generator should be mounted in trunnions fore and aft on a vyery light pressed steel or. tubular subframe, in such a manner that it is free to rotate about its own crankshaft and thus balance its own torque reaction. The angular rota- tion would, of course, be limited by a spring-loaded torque arm and any oscillation damped by means of a damping disk of large radius, as in a Lanchester torsion damper. In this manner, each engine unit would absorb entirely its own dis- turbing forces and would transmit as little vibration as a really well- balanced electric motor, The sub- frame would form an integral part of each generating set by which the whole unit would be slung when lift- ing, and by which it would be slid into and clamped into position in the engine room, The ship’s structure would then be called upon merely to withstand the dead weight of each generating set, a matter of about 1% tons only; for no unbalanced forces or vibration will be imparted to it, nor will it be called upon to play any part in the alignment of the engine or genera- 13