The loam molder requires the greatest all-around skill in the whole range of foundry work. He must know all the tricks of the core room and dry-sand shop, and most of those in green sand. Added to all this he must have a practical working knowledge of the principles of drawing and must possess to a large degree the foresight of the designer.
In order to save time and lumber in the pattern shop, only a set of sweeps is provided if the mold is simple, and these, with blue prints of the piece wanted, are all the molder has to work from. In intricate work, such as a modern Corliss cylinder, a skeleton pattern carrying the steam chests, etc., in accurate position is made, and in some very crooked work a pattern is furnished complete. As a rule, however, the loam molder must rely upon his own skill and ingenuity for the best method of constructing each detail of the work.
The equipment for the loam floor varies in different shops. In Fig. 119 are shown the essential features of an equipment for sweeping-up circular forms.
The spindle a should be large enough not to spring when being used, and long enough to conveniently clear the highest mold. A piece of 2-inch shafting is a handy size, for with it the sweeps may be made uniformly 1 inch less than the required diameter and placed snug to the spindle when set up, and the correct size of mold is ensured. This spindle should revolve smoothly in a step b. The step shown may be set at any convenient place on the floor. It has a long taper bearing, as shown in section A, capable of holding a 5-foot spindle without need of any top bearing. The three arms serve to make the step set firmly, and upon them any plate may be readily leveled up. Where a tall spindle is used, the spindle socket is more shallow; the step may be cast without arms and be bedded in the floor. The top of the spindle is steadied by the bracket c. This must carry a bearing box so designed that the spindle may be readily set in position or removed. And the bracket must swing back out of the way when any parts of the mold are to be handled by the crane. Sweeps. The sweeps are attached by means of the sweep arm d. The detail B shows one method of clamping the sweep arm to the spindle by using a key. The arm is offset so that one face hangs in line with the center of the spindle. Bolting the face side of the sweep to this brings the working edge in a true radial plane. Sweeps are usually made from pine about 1 1/8 inches thick. The working edge is cut to the exact contour of the form to be swept, and then is beveled so that the edge actually sweeping the surface is only about 1 inch. For very accurate work or when sweeps are to be much used, the edge is faced with thin strap iron to prevent wear.
Fig. 119. Rig far Loam Work.
We have seen that the walls of green- and dry-sand molds are supported by sand packed into flasks and that these flasks may be lifted, turned up sideways, or rolled completely over to suit the convenience of the workman. The facing which forms the wall of a loam mold is supported by brickwork built upon flat plates of cast iron, and laid in a weak mortar of mud. From the nature of their construction, therefore, these molds must always be kept perpendicular when being handled. The parts may be raised, lowered, or moved in any direction horizontally, but they must not be tipped or rolled over.
The plates are cast in open sand molds, as illustrated in Fig. 56. Two methods are employed to provide for handling them by the crane; either lugs are cast on the edges of the plates, as in C, D, and E, Fig. 119, or wrought staples are cast in the plates, as shown in B, Fig. 120, or in the crown plate of the main cylinder core. Fig. 123. Three typical plates for a loam job are shown in Fig. 119. C is the building plate; it should be at least 18 or 20 inches larger than the largest diameter of the casting to be made, and thick enough to support the weight of the entire mold without springing. D shows a cope ring; its inside diameter should clear the casting 2 inches on all sides. The face should be 8 to 12 inches wide, depending upon the height of the mold. E shows a cover plate; its diameter equals the outside diameter of the brickwork on that part of the mold which it covers. Here the loam facing is placed directly on the iron, and must be supported when the plate stands vertically or is turned completely over as in C, Fig. 122. To hold the loam in this way, fingers or stickers are cast on these plates. This is accomplished by simply printing the end of a tapered stick into the bed of the open mold which shapes the plates. These sticker plates are often used for a purpose similar to the core E, Fig. 116, and shape the outer face of a picked-out flange. This is illustrated in D, Fig. 122.
Fig. 120. Laying-Up Loam Work.
Fig. 121. Steps in Sweeping Up Typo Mold.