POWERFUL NEW ENGINE.

Colonist, Volume LX, Issue 14653, 6 March 1918, Page 2

POWERFUL NEW ENGINE.

AIR TROUBLES FOR GERMANY

What is in store in tie air for Germany in 1918 may be surmised from the announcement that His Majesty the King, at his visit to the Napier works, was greatly interested in a powerful new twelve-cylinder engine, yctid to weigh between 6001b and 7001b and to develop something like 500 horse-power. As the lowest weight to power ratio hitherto accomplished ha.3 been about |2|lb weight per unit.-of horse-power, this new model must be very remark^:, able, and possibly marks a departure in; the use of aluminium alloys which, if successful,will revolt tionise aerotongine construction, says the '-Field." 4'At the sa-nie time, it has to /bo pointed out j that, proportionately to its power, the largo engins can be-built-lighter'than the smaller. ..Nothing approaching tliir> particular model in weight, however, has been seen in work. The manner of

its production can .bo surmised when we are told that each of its cylinders is machined from a casting which, in the rough, weighs almost 801b, and when finished and ground, ready to receive the piston, weighs no more than sseveri.

Operations of that character' are not merely tedious,, but 'very expensive, and, while the' efficiency secured probably justifies the-time and cost, we doubt very much whether either our enemies or our. allies follow such methods. To securo a 'maximum of power in an engine of this character it is a prime necessity that the expansion of the cylinder and the piston shall be uniform at every point. This can only be obtained by using a perfectly ■homogeneous", metal, practically with j'equal co-efficients of expansion, and constructing..cylinder; and piston so accurately that the thickness of metal is perfectly equal at .every, point of 'the cylinder, aid piston walls..] That end can only be attained by turning or grinding; each to a gauge. If it be- any air-cooled cylinder, the external cooling fins have to be machined or ground to equality throughout. Even then variations in the density of the steel will cause unequal expansion, which, in tho case of a light cylinder^ may quickly tesult in grave loss of efiVcioncy. aad-a "dud-"'engine.