There are two common types of these foundations. The first one, for small or medium sizes of drop presses or hammers, are built with timbers set on end and firmly bolted together in sufficient numbers to form a foundation of the required size, as shown in Fig. 37, the bolts going entirely through the mass. Timbers 10 × 10 inches or 12 × 12 inches are a convenient size, and hard pine is found by experience to be best adapted to the work.

The excavation is first made to solid ground, then a foot or so of hard gravel is tightly rammed down in the bottom, to form the bed. The timbers are cut of a proper length to reach the surface, but should not be less than 5 feet long. They are bolted together, lowered into place, and leveled up, and good hard gravel is tightly rammed in around the timbers, filling the space between them and the sides of the excavation.

This form of foundation is adapted for drop presses and small hammers in which the anvil is a part of the machine itself. In case a hammer is of such size as to have the anvil detached from the main frame, the latter is supported upon a stone foundation, or on one partly of stone and partly of brick (built in two piers for a double hammer), as shown in cross-section in Fig. 38 and in side elevation in Fig. 39. The foundation for the anvil is built of timbers laid horizontally, the base being spread over as large an area as practicable, in order to resist the force of the blows of the hammer.

In a double hammer the anvil foundation must be restricted in width, but may be extended in length at the base so as to present the form shown in the engraving.

Fig. 37. Drop Hammer Foundation.

Cross Section of Steam Hammer Foundation.

Fig. 38. Cross Section of Steam Hammer Foundation.

The size of the foundation is necessarily proportioned to the size of the hammer, but approximately as follows: Supposing the width between the upright parts of the main frame to be 6 feet, the width of the timber work will be about 4 feet, the length on top 8 feet and at the base 12 feet - assuming the necessary depth to be 4. feet. If solid ground is not found at this depth, the excavation may be filled up with hard gravel, stone or concrete; or a layer of concrete may be placed at the bottom, then a course or two of stone laid in cement mortar, and finally hard gravel well rammed in. The timbers should be bolted together at the comers or securely spiked, but owing to constant shocks, bolts are to be preferred. The top corners of the timbers should be bolted together horizontally. The masonry piers and timber foundations must not in any way be connected, as the constant concussions would soon disintegrate the masonry. All spaces around the masonry and timber work should be tightly rammed with hard gravel. The size of the timbers may be from 6×6 inches and larger, according to the size of the structure; but they are usually 10 × 10 inches or 12 × 12 inches. Timbers used in places where decay is feared should be coated with hot gas tar as a preservative.

Fig. 39. Longitudinal Section of Steam Hammer Foundation.

On one occasion, in soft and very yielding ground, a machine of forty tons weight was supported by a foundation built by excavating nearly 30 feet deep, piles being driven at 2 feet centers over an area about three times the width and length of the base. Upon these was built a timber structure in the manner described, up to within six feet of the surface of the ground, and gradually drawn in to four feet larger all round than the base of the machine, which was quite high in proportion to its width of base. On this timber work stone laid in cement mortar was built up to the level of the ground and the machine erected upon it. The foundation proved successful.