MANUFACTURE OF MUNITIONS

Dominion, Volume 9, Issue 2683, 1 February 1916, Page 7

MANUFACTURE OF MUNITIONS

HIGH EXPLOSIVE SHELL CASES

SUCCESSFUL EXPERIMENT

For! some months past the Hon. [Arthur Myers; Minister for Munitions, •has been in close comimuiication with the Commonwealth! Minister for Defence and tho Secretary.of tho Federal Munitions ' Committee,. Melbourne, and. through their kindness has been kept Tip-tomato with tho formulae, specifications, plans, ctc., ' necessary for tho manufacture of tho IS-pounder high explosive shell which is playing such an important part in modern warfare and of which such enormous quantities are required. In its interim report tihe Munitions Committee, whicli v/as.set up at a conference of engineers held last September m Wellington at the request of the Minister for Munitions, indicated, inter alia, that the bodies of these shells could be manufactured in New Zealand, provided the proper steel and copper bands could be obtained; aJid, in order to make a practical demonstration, a small quantity of steel was procured from the Broken Hill Proprietary Company of Australia. This steel is supplied in rolled 31-inch bars, and is the material used by the Commonwealth authorities for a similar purpose. Professor R. J. Scott, of Christcliurch, chairman of the committee, offered to undertake to turn out an experimental batch of tho shells, and for this purpose Mr. E. H. Hiley, General Manager of Railways, placed at his disposal the services of Mr. Jackson, chief mechanical engineer, and the staff and machinery of the Addington Railway Workshops. It is interesting now to learn that 18-pound high explosive shell bodies true to War Office^specifications ravo been turned out, the finished article, it is stated, presenting a decidedly,, workmanlike appearance, and reflecting' great oredit on those concerned with its manufacture.

The whole of tho formation of the shell is' effected by machining, no "forging or pressing or heat treatment being , now required. Some idea of the work involved may -be gathered from the following short description of tho process of manufacture from the arrival of the steel at the works to the finished article.

Test specimens are cut from tho steel bars, and on these passing somewhat exacting physical tests, the bars are straightened and cut up into lengths, each of which will make a single ishell. These blanks are drilled form the cavity for the explosive, the cavity being subsequently carefully bored and then exposed to a sand blast, .vhich gives' tho exceedingly smooth finish necessary for safe handling,, where high ' explosive charges are used. As ' a further protection, the interior of the shell is varnished and the surface baked. The mouth of the cavity is screwed to take the standard fuse, all measurements of this part being mado to the thousandth part of an inch and tho extremo perniissiblo variation in size being .006. It is therefore quite evident that such work can be accomplished only with the assistance of gauges and the most accurate'of tools, and to enable tho abovo-mentionea batch of shells to be made some, sixty gauges had first to be manufactured by the Railway Department, each in all portions accurate to tho thousandth part ci an inch. ' '

The body of the shell is turned and the nose ground, the perniissiblo vari-. ation in the diameter being one hundredth part of an inch, but accuracy comparable with that at the fuse screw is required iu the copper driving band, which serves tho double purpose of a gas check and means of'rotating the projectile by being forced into the rifling of the gun. The formation of the groove for taking this band is a very "nice" operation. It has to be undercut to an amount comparable with the siy.o of a pin's head, and also have formed in it a pair of waved ribs, tho function of which is to ensure the rotation of the projectile. The band itself is made from copper tubing of a size which will just slip on to the finished projectile. Tho supply of copper tubing was procured from tho .Victorian State Munitions Committee, who had imported a large quantity supplied, to War Office specification by tho' Brougliton Copper Company. The band is compressed into its groovo by means-of six radial hydraulic presses, which simultaneously force steel noses against it, and is afterwards turned to correct profile. The base of t-fie shell Is then recessed and a base plafo of steel, the grain of which is transverse to tha* of the body of the shell, is soreivud and cemented into it. This is a precaution against the chance ignition of the bursting charge by a flash through an undetected flaw iii the lwso of tho shell.

"Of courso ifc must be remembered," said Mr. Myers to a reporter, "that if we are to proceed vigorously with the manufacture of large quantities of these shells—and' to be of any real service this would . have to be' done — tho Railway Department would necessarily have to set aside a • large' portion of its important work of making carriages and maintaining the present rolling stock, while if the work were undertaken by outside firms tho assembling of their plant in central localities would have the effect of interfering to a large extent with the making of freezing works machinery and dairying machinery which are so necessary for the carrying on of our important industries. It will be seen, therefore, that the problem is a very weighty one, and will require most careful consideration."

The information in tho hands of the 'Minister of Munitions, together with tile result of tho experimental manufacture, will enable liim to place tho matter before Cabinet, who will now consider tho whole question.