CHAPTER XV.

EXAMPLES IN ENGINE WORK.

IN the figures from 308 to 328 inclusive are given three examples in engine work, all these drawings being from The American Machinist. Figures 308 to 314 represent drawings of an automatic high speed engine designed and made by Professor John E. and William A. Sweet, of Syracuse, New York. Figure 308 is a side and 309 an end view of the engine. Upon a bed-plate is bolted two straight frames, between which, at their upper ends, the cylinder is secured by bolts. The guides for the cross-head are bolted to the frame, which enables them to be readily removed to be replaned when necessary. The hand wheel and rod to the right are to operate the stopcock for turning on and off the steam to the steamchest.

The objects of the design are as follows: Figure 310 is a vertical section of the cylinder through the valve face, also showing the valve in section, and it will be seen that the lower steam passage enters the cylinder its full depth below the inside bottom, and that the whole inside bottom surface of the cylinder slopes or inclines towards the entrance of this passage. The object of this is to overcome the difficulty experienced from the accumulation of water in the cylinder,

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which, in the vertical engine, is usually a source of considerable annoyance and frequently the cause of accident.

Any water that may be present in the bottom finds its way by gravity to the port steam entrance, and is forced out by and with the exhaust steam at or before the commencement of the return stroke.

To assist in the escape of water from the top of the cylinder, the piston is made quite crowning at that end, the effect of which is to collect the water in a narrow band, instead of spreading it over a large surface. This materially assists in its escape, and at the same time presents a large surface for the distribution of any water that may not find its way out in advance of the piston.

The piston is a single casting unusually long and light, and is packed with four spring rings of inch. square brass wire.

The valve is a simple rectangular plate, working between the valve face and a cover plate, the cover plate being held in its proper position, relative to the back of the valve, by steam pressure against its outer surface, and by resting against loose distance pieces between its inner surface and the valve seat. This construction admits of the valve leaving the seat, if necessary, to relieve the cylinder from water, as in the instance of priming, and also, by the reduction of these pieces, admits of ready adjustment to contact, should it become necessary.

The cover plate is provided with recesses on its inner surface which exactly correspond with the ports in the valve face, and the corresponding ports and re

cesses are kept in communication with each other by means of relief passages in the valve. From this it will be seen that the valve is subjected to equal and balanced pressure on each of its sides, and hence, is in equilibrium.

The valve is operated through the valve motion, shown in Figure 311, the eccentric rod of which hooks on a slightly tapered block that turns on the pin of the rock arm, like an ordinary journal box.

The expansion, or cut-off, is automatically regulated by the operation of the governor in swinging the slotted eccentric in a manner substantially equivalent to moving it across the shaft, but is however favorably modified by the arrangement of the rock arm, which, in combination with the other motions, neutralizes the · unfavorable operation of the usual shifting eccentric, and which, in connection with the large double port opening, provides for a good use of steam from o to 34 stroke.

The governor shown in Figure 312 is of the disc and single ball type, the centrifugal force of the ball being counteracted by a powerful spring. Friction is reduced to a minimum in the governor connection, by introducing steel rollers and hardened steel plates in such a manner as to provide rolling instead of sliding motion.

In order that a governor shall correctly perform its functions, it is unquestionably necessary that it have power largely in excess of the work required of it, and also that the friction shall represent a very low percentage of that power. In respect to this, especial means have been employed to reduce the friction; the