RING-PITS.
The next manner of tempering clay is by the ring-pits, which usually furnish clay for six gangs, and are run either by horse or steam power.
These pits are about twenty feet in diameter, two feet in depth, and commonly hold clay sufficient to make fourteen thousand brick ; they are cased around with hard-burned brick, and the bottom is usually covered with oak planks, cut wedge shape. Hard pine is cheaper than oak, and is also used.
There is a pedestal firmly set in the centre of the pit, upon which the machinery that works the tempering wheel is placed.
For a ring-pit worked by horses, there is a long shaft of iron passing through the centre of a wheel, about six feet in di ameter, called the tempering-wheel, and terminating beyond the ring far enough for two horses to be hooked to it, and have room sufficient to travel around the ring with it.
There is a gearing of wheels so arranged as gradually to push the tempering-wheel from the centre to the outer edge of the pit, while the wheel is revolving around the circle, and when it reaches the outer edge to again gradually draw it towards the centre.
In the pits using horses to work them, there is sometimes a small wheel, about one foot and six inches in diameter, and which travels in a level track around the edge of the ring, sup porting the long iron shaft which passes through it.
Recent changes have been made,jn the wheel by placing the spokes at an angle, producing a dish in the wheel, so as to suit the circle of the pit, saving the labor of the horses ; it also grinds and leaves the surface of the clay level in the pit during and after grinding. An illustration of the Raymond tempering wheel, made by C. W. Raymond & Co., Dayton, Ohio, is shown in Fig. io. The capacity of tempering-wheels of course de pends upon the nature of the clay and also the power furnished ; but the wheel shown in Fig. 10 will temper clay for 30,000 to 40,000 brick per day under favorable conditions. The open tooth and the box racks are now in use ; the latter have the cogs placed on the inside around the rack, a rib on the top side placed lengthwise, and when coming in contact with a pin placed in the bottom side of the cross-bar on the saddle, causes the rack to shift. The racks can be made of different lengths, to suit smaller sized pits, when necessary. Directions can be obtained for setting the wheels on application to the manu facturers.
When steam is the motive power, the principle of construc tion is about the same ; but the shaft which passes through the tempering wheel does not extend much beyond the edge of the ring, and the whole machinery is attached to a vertical shaft, and on the top is a heavy bevelled gearing.
Serious difficulties have been encountered in constructing and operating machines of this class, from the fact that the power which has propelled them has been communicated through some horizontal shaft above the receptacle for the material to be tempered, which arrangement has necessitated the use of a long vertical shaft to communicate the motion of such horizontal shaft to the shaft and gear-wheels which propel the tempering-wheel. This arrangement of the parts has ren dered necessary expensive, and in many cases inconvenient, frame-work to support the shafting, which often interferes with the efficient working of the machine, and is always a large ad dition to its cost. Another, and a very serious objection, has arisen from the fact that the pinion which meshes into the circular rack upon the upper surface of the clay receptacle has been constructed in accordance with well-known rules as to its diameter and the pitch-line of its teeth, which form of construc tion, it is claimed, is found defective in this particular case.
When steam power is employed for driving these machines, two of the pits are placed on the same line, the distance be tween the nearest points of the circles being about six feet.
There are no separate temperers for the ring-pits of either class ; the driver of the horses in one case, and the engineer in the other, let the water into the clay, and see that it is properly tempered. It requires two of these pits, of either class, to temper clay for six gangs, as it is worked out of one pit, while the other pit of clay is being tempered. The sheds, which must be maintained over the ring-pits of both classes, are much more expensive for the ones that are run by steam power than for the other class, as the timbers have to be very heavy, and well framed and braced. Sometimes clay enough to make twenty-eight thousand brick, which is sufficient for twelve gangs, is worked out of two ring-pits daily ; when this is so, the pits are filled after the gangs stop work, and the clay is then tem pered during the night time.