Since the air that is sucked in during the operation has constantly same pressure, there is no valve for regulating the entrance of the water into the vertical conduit. Upon issuing from the latter, the mixture of air and water strikes the surface of the water in the chamber, b, and the violence of the shock upon the bottom is deadened by the interposition of a stone. While the water is escaping through a lateral aperture in the chamber, b, the air is reaching the tuyeres through a wooden conduit of square section which is fitted to an aperture in the upper part of the chamber. This sorry arrangement, which obliges the mixture of air and water to penetrate the water at the bottom of the upright conduit, a, retards the separation of the two fluids, and results in damp air being forced into the crucibles.
The Trip Hammer.--Fig. 4 shows the general arrangement of the apparatus that go to make up the forging mill. The hammer and cam shaft have their axes parallel, and the latter is placed in the prolongation of the axis of the wheel. The hammer consists of a roughly squared beam, 4 meters in length, and of 0.25 m. section. The head, A, consists of a mass of iron weighing 150 kilos, including the weight of the straps that surround the beam on every side of the piece of iron. The axis of rotation is situated at the other extremity of the beam, B. The cam shaft which serves to maneuver the trip hammer is provided with four cams which lift the beam at a point near the hammer. The length of this shaft (to the extremity of which is adapted the water wheel) is 4.75 m., and its diameter is 0.50 m. The wheel is an overshot one, 3.25 m. in diameter by 1 m. in width. The water, which is led to it by a flume, acts upon it by its weight and impact, and is retained in the buckets and kept from overshooting the mark by a jacket made of planks.
FIG. 4.--THE TRIP HAMMER.
The anvil upon which the hammer strikes is surrounded by a bed of stones (quartzites) derived from the neighboring rocks. It is a mass of iron, 75 kilogrammes in weight. In order to prevent vibrations in the trip hammer when it is lifted, and increase the number of blows, there is established a spring beam, which is formed of unsquared timber, which is firmly fastened at one of its extremities, and which receives at the other end the shock of the hammer head when the latter reaches the end of its upward travel.
Reheating Furnace.--This is a double fire furnace, like those used in our smithies, except that the wind, instead of being forced into it by means of a bellows, is supplied by a tromp which receives water from the same channel as the wheel. The two furnace tuyeres are arranged exactly like those of the cadinhes, upon a wooden conduit which starts from the wind chamber (Fig. 5). This furnace serves to prevent the cooling of such blooms as are awaiting their turn to be shingled, and of such bars of finished iron as are being made into tools.
OPERATION OF THE SYSTEM.
A forge like the one whose plan we give, may be run with 1 workman at the cadinhes, 1 assistant, 1 workman at the hammer; total, 3 men.
Furnace.--The work lasts about twelve hours per day, and three operations of three to four hours are performed in each cadinhe, thus making twelve per day. At each operation, 22.5 kilos. of ore and 45 of charcoal are used. From this there is obtained a bloom of 15 kilos. The operation is performed as follows:
While the assistant has gone to put the bloom of the preceding operation under the hammer, the workman prepares at the bottom of the crucible a bed consisting of a mixture of sand and very fine charcoal, and then fills the crucible up to its edge with charcoal. At the end of a quarter of an hour, the fuel being thoroughly aglow, the workman puts in the first charge of ore in powder (jacutingue), about 2 kilos, and covers it with charcoal.