MARK V FUSE ASSEMBLY.
This picture shows two complete units for this assembly work. The operation begins in the foreground with cap assembly and progresses toward background, the fulminate detonator being inserted midway down table. The protecting bulkhead for cap supply is shown in the foreground.
The so-called 50-50 amatol, composed of 50 parts ammonium nitrate and 50 parts T. N. T., is loaded into shell by a casting method similar to that used in loading T. N. T. alone.
The so-called 80-20 amatol, composed of 80 parts ammonium nitrate and 20 parts T. N. T., was originally loaded cold, by hand, and then followed up with mechanical pressing. As a substitute for this method, which is accompanied by a certain element of danger, the use of hot 80-20 amatol, was resorted to in England. This was tamped by hand to the proper density, it being more compressible than cold amatol.
As this is an exceedingly tedious method of operation it was entirely done away with in England, except for large shell, by the use of what is known as the horizontal extruding machine. With this machine the British were able to load 80-20 amatol with great success into the 75-millimeter shell and higher calibers up to 8 inches.
This machine took a mixture of T. N. T. and ammonium nitrate in a jacketed hopper, so that the temperature might be maintained, and the hopper fed it down through a funnel upon a screw that was placed against the shell by counterweights to give the proper density. One of these machines was imported here from England, but, as it was unsatisfactory from a construction standpoint, new and satisfactory machines were built on the same principles of construction in our own amatol loading plants.
Experimental work with these machines was carried on at the Government testing station Picatinny Arsenal, Dover, N. J., and the du Pont Experimental Station, Gibbstown, N. J., as well as experimental plant operations at the Morgan plant of the T. A. Gillespie Co., Parlin, N. J., and the Penniman plant of the du Pont Co., Penniman, Va. All difficulties of the operations were overcome so satisfactorily that the greater portion of the loaded shell was produced by this method.
The metal parts as received at the shell-filling plant are inspected and cleaned to remove all traces of foreign matter such as grit or grease before being sent to the loading room. After being loaded the shell are again inspected. At intervals a split shell is loaded and then taken apart and examined, so that any loading defects may be found quickly and conditions remedied, before any large quantities of shell are produced.
The cavity left in the amatol by the tube of the extruding machine is filled with molten T. N. T., and a cavity is produced in this T. N. T. into which the booster fits. This is necessary in order to provide for complete detonation. The booster cavity is produced either by the use of a former, which upon removal leaves a cavity of the proper size, or by plunging the booster into the shell filling before this is cooled, or by drilling out a cavity for the booster after the filling has been thoroughly cooled.