Insufficient foundations installed for some years parts that are exposed to oil drippings become rotten. These portions should be cut away and renewed with neat con crete. Frequently the foundation proves to be too small to adequately support the engine. It then becomes necessary to devise ways and means of increasing the foundation footings.
Some engineers merely trench around the old footing and add a few feet of concrete. Unfortunately the new and old concrete always fail to unite with any measure of bonding. The only satisfactory correction of this foundation trouble is "rafting." A trench should be dug completely around the engine foundation; the bottom of the trench should be at least 4 feet below the foundation base. Three or more tunnels about 4 feet high and 6 feet wide should be driven transversely under the foundation. These tunnels connect with the trench and are filled with concrete as is also the trench. If the vibrations have been excessive, it is advisable to fill the tunnels with concrete and remove the earth from between the tunnels, filling these voids with concrete. This increases the entire foundation depth by the height of the tunnels. The footings can be extended to any desired width. Many instances of warm bearings on engines using outboard bearings are directly traceable to a shifting or settling of the foundation.
Vibration.—One of the objections voiced against the installation of a Diesel engine in an office building is the vibration so often present in the internal combustion engine. There is no adequate defense against this charge, for, as customarily installed, an oil engine sets up vibrations that can be felt even in large buildings.
In preparing the foundation for these installations a layer of felt at least 10 inches thick should be placed over the entire bottom of the foundation excavation. A concrete retaining wall 6 inches thick should be built about the foundation. This wall serves to keep the earth from touching the foundation. A wooden form for the foundation is then placed within this retaining wall. The form can be made of 2 X 4 in. studding and 1 X 12 in. rough boards. The 2 X4's should not touch the retaining Walls but should be supported by wedges. After the concrete is
in the wedges can be removed; this will allow the wooden forms to be dismantled. The distance between foundation and retaining wall ought not to be less than 8 inches. With this construction the foundation is not bound in any way to the building and the layer of felt will absorb all the shocks incident to the engine's operation.
With any concrete foundation, after the engine is erected, a heavy coating of waterproofing cement mixture makes an ideal finish. This coating will serve to keep any oil from seeping into the concrete.
Installation of Engine Frame or Bed.—The frame is generally mounted on skids when shipped from the factory. To unload this heavy section entails considerable mental and physical effort. The easiest method involves the building of a crib against the end of the flat car with a runway of heavy timbers, such as 12 X12 in., laid from the level of the car to the edge of the engine foundation. After the frame has been jacked up and rollers inserted under the skids, it can be easily pinched to the incline. A rope hitch should be run to the end of the car and about the car axle for the purpose of restraining the motion down the incline. Since the "runway" has been carried up over the foundation, clearing the foundation bolts, the frame is moved without difficulty into approximate position on the concrete. In many instances a winch is available, which reduces the labor of moving the heavy bed. It usually is necessary to employ a "dead man," or post, and a tackle block. The next step is the placement of the frame directly on to the concrete. This involves the use of at least four heavy jacks, one at each corner. These jacks can be located in recesses to be filled after the engine is set. The frame is raised a slight amount and the skids are removed, Fig. 24, after a number of iron wedges with a butt thickness of about inch have been prepared and placed on the foundation along the line of the frame. The frame is now lowered and rests on these wedges, whereupon the jacks are removed. The wedges are used to line up the frame.