As the frame rests on wedges, the center lines of the engine should be established. Since the stakes used in locating the center line of the template are still in place, the piano wire is run between the two stakes and through the bearing housings. The bed can be shifted until the wire is exactly center. The wedges are then gradually knocked out, bringing the frame down on to the foundation. If care is used in moving the wedges, no shifting will occur.
Leveling up the Frame.—If the engine, is a horizontal one, it is usually possible to level it up by a spirit level placed on the main bearing housings. The top surfaces of the housings are machined parallel with the plane of the crank and cylinder center lines. By placing the level parallel with the shaft line the frame can be trued up transversely, while placing it across the top of the two throws and parallel with the cylinder allows the discrepancy that exists longitudinally to be corrected. It is necessary to check the results by leveling both housings and rechecking the process. A few engines have a true surface machined on the top of the cylinder jacket to facilitate the work of leveling.
After the frame has been leveled, the foundation bolt-nuts should be drawn down tight and a thin grouting of neat cement poured into the cavities around the bolts and well troweled under the frame. If this coating is brought up above the bottom of the engine frame an inch or so and sloped toward the edge of the foundation, the appearance of the installation is much im proved. The iron wedges should be left in place. In event the engine settles out of line, these wedges facilitate correcting the trouble.
With a vertical box-frame engine a sub-base is usually provided. This is first set on the foundation and aligned by the same proced ure. However, while the bolts should be drawn up snug, the grouting in is best deferred until the main frame is set. Where the sub-base is used, the bottom of the frame is usually planed, and the frame should set level if the sub-base has been properly aligned.
Erecting the Cylinders.—All horizontal engines are shipped with the cylinder liner in place; it follows that correct alignment of the cylinder is secured when the frame is properly set. With the vertical box-frame engine the placing of the cylinders is a ticklish proceeding and calls for much ingenuity in plants where facilities are meager.
Every plant should with an I-beam trolley and differential hoist. This hoist should be of at least 5-ton ca pacity. The I-beams can rest on brick pediments that are incor
porated in the building walls. In case such equipment is not available, it becomes necessary to construct a wooden frame similar to Fig. 24A. The top beam should clear the frame by at least 10 feet to give ample room for the blocks. If timbers of sufficient length are not obtainable, the frame can be made of built-up timbers constructed of six planks, 2 X12 in. in size, lag-screwed together. Stout planking should be placed along the side of the engine to prevent the cylinder damaging the frame as it is hoisted to the top; 6 X 6 in. cross timbers can be laid across the top of the frame to act as a landing for the cylinder. These timbers guard the studs against damage. The tackle blocks, or chain hoists, are fastened to the cylinder top, and it is raised until it can be lowered on to the 6 X 6 in. platform. It is always advisable to use two blocks. This is a safety meas ure in case one breaks. After the cylinder is placed on the plat form, it should be pinched into place over the studs. All the timbers save two outside the bolt circle can be removed. By lifting the cylinder with the blocks, which have been centered above the cylinder, the two timbers are withdrawn and the cylin der lowered on to the frame.
After the cylinder is in place, a plumb bob is dropped through it. To do this a metal or wood strip, similar to Fig. 25, is fastened to one of the cylinder-head studs. A washer is attached to the bob line after the line has been passed through the slot in the strap. The strap is placed over the approximate cylinder center. The slot allows the bob line to be moved until it is exactly center. To center the plumb line at the top of the cylin der, a pair of inside calipers are used. This centering calls for the greatest patience on the part of the erector. After centering the line at the top, measurements must be taken at the bottom of the cylinder to ascertain if the bob line is central at this place. Since both the cylinder flange and frame top are machined true, it is seldom that the cylinder does prove out of plumb, providing the frame has been properly set. If this should occur, the frame must be wedged up until the cylinder center line is plumb. If the engine is multi-cylindered, a plumb is dropped through each cylinder and kept in place until the engine shaft is lined up, Fig. 26. The bob lines must square with shaft, center line. Practically the same method can be followed with the A-frame engine.