Engine all manufacturers furnish the wooden template with shaft and cylinder center lines marked and with all the bolt-holes bored in their correct positions. When the template arrives in several sections, the engineer must unite the parts. Extreme care must be used in this assembling. It is advisable to lay the parts on a level floor, and, after squaring up the center lines, the sections can be fastened together with screws.
In setting the template above the foundation excavation, en gineers use devious methods. Some block up the wooden form at a number of points. This is indicative of shiftlessness and lack of appreciation of the work's importance. The one method that is free from criticism is the use of two heavy timbers, about 12 X12 in., to which are bolted cross stringers of 6 X 6 in. The template is suspended from this framing by bolts, and, if the ends of the 12 X 12's rest on solid footings, the entire framing is rigid. If the engine is of medium size, 8 X 8 in. will serve for the bearing timbers. Such a structure will not move in event a barrow of concrete is thrown against it.
Foundation proportioning of the concrete in gredients varies over a wide range. It depends to a considerable extent upon the character of the sand and' gravel used. It is obvious that, if the gravel is not washed, the proportion of sand would be less than where a clean gravel was obtainable. For heavy foundations, such as the one under discussion; a ratio of one part cement, two parts sand and four parts gravel, or crushed rock, is advisable. This mixture possesses ample binding strength and is free from the danger of cracking which develops when a leaner mixture is adopted. In order to lessen the foun dation expense, many replace the gravel or crushed stone by broken brick. The objection to the brickbat lies in the danger of serious fractures; furthermore, unless they are clean, a good bond with the cement cannot be secured. Upon pouring the conglomerate into the excavation it should be thoroughly rammed, especially at the corners. Enough water should be added to make the mixture "quaky." In most installations the process of pouring the foundation extends over a period of several days. Each night the surface should be given a thorough wetting down to prevent any pre mature setting during the night. If the weather is cold, an old
carpet or other covering can be placed over the foundation to pre vent freezing. It is seldom necessary to place a foundation in freezing weather, but when such conditions do exist the water used should be warm, and a liberal covering of straw and old carpets placed over it each night. After bringing the foundation to the desired level, the surface should be left in an unfinished condition and dampened each night. This keeps the surface concrete green and allows a good finish coating to be applied after the erection is complete.
Often the foundation print shows no reinforcing steel. With any oil engine there is need of tie bars inserted in the concrete. It is not necessary that special bars be purchased. Old steel rails, discard I-beams and the like are just as serviceable. A row of rods or bars laid longitudinally with crossbars at frequent intervals for a reinforcing matting will bind the entire structure. The steel should be laid about halfway from the base.
Foundation Bolts.—The best of authorities recommend a foundation bolt tunnel under the foundation in order that the bolts may be placed in the holes after the frame is set on the foundation. This is undoubtedly an excellent plan with engines above a thousand horsepower capacity. With units under this size the results obtained do not justify the heavy expense of forming the tunnel. The same objection applies to the design wherein recesses are formed in the concrete at the base of the bolt cavities.
For all ordinary installations the best method embodies the employment of bolt tubes: 3-inch black pipe is quite satis factory. When such an arrangement is decided upon, the pipes should be cut to a length equal to the length of the bolt from bottom washer to wooden template. After the pipes are placed upon the bolts and the latter suspended from the wooden template, it is advisable to wrap the pipes with a strong manila paper. This paper prevents the pipes from being gripped by the concrete, allowing the pipes to be withdrawn after the concrete has set. After the engine base has been set, the space between bolt and concrete should be filled with neat concrete.