SOME WAR SECRETS

Dominion, Volume 13, Issue 238, 2 July 1920, Page 7

SOME WAR SECRETS

PERFECTING THE DEPTH CHAEGB.

Although the depth charge was the most powerful of>the weapons that cheeked the operations of tho U-boat, thus leading indirectly to the collapse o£ the Central Powers, I imagine that no moro than ten people in every.thousand would be able to explain'-ju'st wlimt a dentli charge is, writes C. B. Dewhurst, M.Sc., in the "Daily Mail." Jack Tar himself,, who knows most things, could not tcllj you how and where it came to be constructed.

Manchester University did, in fact, make the first depth chargo, It would, be inaccurato to 6ay it was invented by. usi like the tank, tho depth charge is • (nobody's child. But wo can honestly claim'that it was our Engineering. De-' partment which experimentally developed tho depth chargo to tho commercial strtgo.

It was one of the.many odd problems sdt us by the Admiralty. Thev asked us for a lSin. bomb-thrower whicli would project a weight.of lewt. a distance of 500 .yards by compressed. air. We supplied it. They asked us for a shackle which would stand a pull of one ton and melt after being immersed in the water for a certain length of .time. It was a novel request, and probably tho thought' they had set. ui a Dosor. Tho, object was to discover a contrivance which would shacklo a mine and its sinker together on the bed of tho sea until a mine-laying submarine, had dropped all its "eggs," when, with the' melting of the shackle, each mine would rise to the determined height. We solved that particular problem with' a sugar Bhackle—by pouring melted taf* fee into a cavity dovetailed in a motal Bhackle! It was so devised that it could stand a pull of one ton and a third during the forty-five minutes that the sugar' took to melt. , After the first year of war soveral men from, our laboratory took up responsible ; positions in H.3\f.S. Vernon, the Navy's research department at Portsmouth, and' it was through the Vernon that tho investigations into the question of how to conquer the U-boait first camo back to the Engineering Department at tho university. Two alternative designs of mechanism causine a heavy charge to explode at a fixed depth under water were sent <!o us; for criticism, modification, and experiment, and, after some months of patient experimenting, we were able to hand; over n to tho university instrument-maker the final design from which, under our supervision the first fifty depth charees. were mode..

Our aim was to produce n 6imp!«' mcchanism* thoroughly fool-proof which would ro off at the pressure at which it was sot, The depith chargo consisted of a case containing 3001b. of T.N.T. ftri-' Jiitro-tolnpl) with ftn attached niccL'nnism provided with a flexible diaphrasm and a piston which depressed a spring in such a way that the spring was compressed in proportion to the depth below tho fiurfneo of tho sea. By 11 simple arrangement worked bv a lever on the outside of tho depth charge the amount of compression required to fire the cliarsa could bo adjusted to suit any deptli—m DractlM one spring was released at forty, a second at eighty foot, The firing sear was so arranged that a trigger was released when tho spring was compressed by the amount corresponding to the desired depth. ( 'The triggor fired a detonator! tho detonator exploded the T.N.T.I and—that was tho end of tiis U-boat.