The hydraulic press is controlled by hand valves. The pressure is usually obtained from an individual power-operated pump. A pressure gauge is installed on the line in sight of the operator of the press. This press consists of a circular iron table pivoted in the center to permit a circular movement and designed to be driven upward by means of a ram operated by hydraulic pressure. This ram makes its contact with the table top at a point directly below the line of pressure which is to be exerted upon the frame while charging. Two frames are in operation continually, which may hold from six to eight cases each, ranged in a double row. In operating, only one set of frames comes under the influence of the pressure at a time. During this interval the other set is being charged by the operator. The circular movement of the table top permits the operator to subject the successive batteries of cases to alternative pressure and loading. As is shown by figure 22, the several spindles are bolted firmly to a metal plate, which in turn is attached to the table top.
Figure 23 shows the dimensions of these spindles and the manner in which they are set upon the plunger base. There are four separate sets of plungers used for loading, the number of plungers in each set being the same as the number of rocket cases held by the frames, which may be six or eight in number.
Fig. 22. - Hydraulic press showing cases in place.
Fig. 23. - Dimensional drawing of spindles.
A fifth set of plungers, differing slightly from the others, is used to pack the clay heading at the top.
Fig. 24. - Dimensional drawing of plungers.
The operation of charging the rocket is as follows: The empty cases to be charged are pressed upon the spindles, shouldering tightly around the base. Before the introduction of the plungers, the top of the case is often bell-mouthed. This spreading is done by pounding a tapered wood plug a short distance into the case. The bell-mouthing is to insure the easy entrance and withdrawal of the plungers. The loading of the clay heading has already been described and is the first operation prior to the introduction of the powder charge. Plungers of the set No. 1 are used for ramming this clay heading into place. A pressure is exerted on the ram which when proportioned for each of the separate rammers will be equivalent to approximately 2 1/4 tons each. After the clay heading has been forcibly pressed into shape the plungers are removed. In order to free the plungers two short brass bars are used as hand levers. No. 1 set of plungers is used to ram home the first to sixth charges of composition, inclusive. The No. 2 set of plungers is used to drive home the seventh to tenth charges, inclusive, and the final charges are rammed home with the No. 3 and No. 4 plungers, respectively. Variation in the climatic condition and humidity will cause a certain slight variation in the number of the charges, as to which practice alone will dictate the proper manipulation. Care must be taken that there is ample powder supplied for each successive ramming to prevent the plunger from striking the spindle. The inside diameter of each set of plungers varies in size, in order that this diameter may be larger than the diameter of the spindle at the point where the charge is rammed home. The 1 1/4 massif or heading is rammed home in three successive charges, using No. 4 plungers which have no central orifice. As the plungers are withdrawn after each operation there is occasioned a slight dust of fine highly inflammable powder. Care must be exercised in the handling of the plungers and spindle to see that no spark is struck and that metals are used Which will minimize the danger of sparking by contact. As a safety precaution, the plungers are equipped with brass bushings and the heads of the last set are often constructed with a center lead inlay.
Fig. 25. - Dimensional drawing of plunger for clay heading.
The top clay heading consists of a charge of high-grade molding clay weighing approximately 3/4 of an ounce. The clay measure described previously is filled with clay and introduced into the case on top of the powder charge and rammed home by means of the plunger described in figure 13.
The orifice of the top clay heading is now reamed out in order to clear the walls of this orifice from any accumulation of dirt, and the reamer is forced a slight distance into the massif or heading.
A five-ply quick match is used for this purpose. The match is cut about four inches long, looped into three equal lengths and then forced through the orifice in the clay-heading bottom into the cavity which has been formed in the top of the massif or heading. When the match has been set in place the expelling charge is added.
This expelling charge consists of approximately 27 grains of 5 F. grain meal powder which is poured on top of the clay heading and is contained in the space between the clay heading and end of rocket case. Some of this powder works its way through the orifice in the clay heading, completely filling it. In this manner the quick match is imbedded in the rapid-burning grain meal powder. The function of the expelling charge is to forcibly eject the contents of the rocket head, consisting of the parachute and light.
The muslin drumhead serves the purpose of holding the grain meal powder, which constitutes the expelling charge, in place in the case. This drumhead is unbleached muslin cut into a 3 1/2 inch square and is pasted over the top of the rocket case, covering up the match and the expelling charge. The edges of this square piece of muslin are formed over the sides of the case and pasted firmly to it.
The prime consists of a coating, which is applied to the top surface of the muslin drumhead, completely covering it.
This prime is a slurry consisting of grain meal powder and water in which is dissolved some dextrin. Its composition is as follows:
Sixteen parts 5 F. grain meal powder, one part of yellow dextrin and sufficient water to form a thick paste.
The function of this prime is to ignite the fuse connected with the signal light attached to the rocket.
Fig. 26. - Rocket body showing drumhead and prime.
Before attaching the rocket head, which contains the garniture, the body of the rocket is completed by attaching a device for holding the stick and also by attaching an article which produces the smoke trail.