Wardwell's High-Pressure, Valveless Engine.

The cut on page 241 represents Wardwell's Valveless Engine. As will be observed, it is a horizontal engine, with one end of a girder frame bolted to and supporting the cylinder, and the other supporting the pillow-block. The pillow-block brasses are provided with side adjustment wedges, operated from the top face of the cap by bolts and nuts. The cross-head has V-shaped bearings, top and bottom, with a wrist-pin providing journal-bearings for the fork end of the connecting-rod. The straps at these ends of the rod are provided with the ordinary gibs and keys. At the crank-pin end, however, the strap is secured to the rod by a bolt passing through the strap, the key merely serving to adjust the brasses. The piston passes a working fit through the cross-head, being secured at each end by jamb-nuts, by which arrangement any lateral play of the piston-rod in the cross-head is prevented; but at the same time the rod rotates in the latter. To the extreme end of the piston-rod, after it has passed through the crosshead, there is keyed fast a section of a bevel-wheel containing 5 teeth, which gears into another containing 4 teeth; this latter section being bolted fast to the inside of one of the fork-arms of the connecting-rod; the outside arm being selected as affording the best advantages for adjustment. When the connecting-rod is attached to the crank- and cross-head, and steam admitted to the cylinder, a semirotary movement takes place in regular order, and as the stroke proceeds, the steam passages are so arranged that steam can be admitted, cut off, and exhausted at any desired point of the stroke. It is obvious, however, that to accomplish this the piston-head in the cylinder must be extra long in proportion to the stroke.

The piston is solid, similar to a plunger, and is a neat working fit in the bore of the cylinder. The wear is provided for by the insertion at each end of the piston-head of ordinary spring packing-rings; and to take up wear and prevent leakage from one port to the other, a straight, longitudinal, spring packing-piece is placed

between the steam passages in the piston-head, thus preventing the escape from one port to the other. The steam-port is in the centre of the cylinder, and on top. The steam passages in the piston-head commence near one end, and run along the circumferential surface, in a longitudinal but curved line, so that the passage will remain full open to the cylinder steam-port, notwithstanding the rotary motion of the piston. At such part of the stroke, however, at the point at which the steam is to be cut off, the steam passage turns at an angle, and runs round nearly onehalf the perimeter of the piston-head, so that the rotary motion of the piston during the remainder of the stroke is insufficient to permit any communication between the cylinder-port and piston passages. So soon as the piston-head steam passage turns the angle above noted, the longitudinal movement of the piston-head past the cylinder steam-port cuts off the supply of steam, and the remainder of the piston-stroke is performed by expansion. The circumferential direction of the passage above referred to serves another purpose than acting as a cut-off, in that it enables the same passage to be used to convey the steam to the cylinder exhaust-port. After the steam passage has taken the circumferential direction referred to, it continues longitudinally to the end of the piston-head; the steam passage, while isolated from the cylinder steam-port, comes into open communication with the cylinder exhaust-port, and that stroke of the engine is completed. For the return-stroke, a similarly arranged passage is provided in the piston-head, and hence the piston requires but two passages, each of which operates alternately, as induction and eduction passages.

There were three of this description of engines on exhibition at the Centennial Exposition, which attracted considerable attention, in consequence of the arrangement for admitting and exhausting steam being entirely different from anything heretofore employed. Such engines possess no practical value, their chief interest consists in the novelty of the arrangement.

Lubricants.

To understand the quantity of oil required for steam-cylinders, slide-valves, and the reciprocating or revolving parts of steamengines, we should first know what its objects are. The object of oil is to diminish friction, by interposing a thin film between the sliding or revolving surfaces. To insure perfect lubrication, the surfaces must be kept coated at all times, under all pressures and velocities. In steam-engines there is a sliding and rotating friction, and it is very doubtful if any one kind of oil is perfectly suited to both. Oil has no tendency to improve the character of a bearing; its functions being simply to keep them apart, prevent heat, and diminish friction.

Temperature exerts a very important influence over any lubricant. A thin oil has a tendency to run off too fast, while a thick one is not sure to flow. Tallow, and all other thick and greasy compounds, are exposed to the same objection, as the bearing generally gets hot before the lubricant begins to flow. Besides, what may be called a good lubricant, one that adheres to the rubbing surfaces under ordinary circumstances, may not be equally well adapted to all conditions, as the area of the bearing surfaces varies with the size of the journals, and the form of the boxes, which causes a difference in the velocity of rotation. From this, it follows, that a lubricant that would be retained between the frictional surfaces under a light load, would be entirely pressed out under a heavy one.

The quantity of lubrication that the cylinders and slide-valves of any engine require, depends on the condition of the engine, the amount of work it is performing, and on the pressure and temperature of the steam. If the load is light, the pressure low, and the engine in good order, very little lubrication is necessary; but if the pressure and speed are high, and the engine is working up to its full capacity, the cylinder and valves will require to be frequently lubricated. But in no case should an unnecessary quantity be used, as it is likely to produce a greater evil than the

one it was intended to remedy. A person having charge of steam machinery should understand the work each part has to perform, the speed at which it runs, and the weight it has to sustain. Crank-pins and main-bearings require to be frequently oiled; but the condition of the bearing will determine the quantity of lubrication needed. What is needed in any case is a few drops of good oil applied often. It may be safely said that five times the quantity of lubrication is used on the revolving and rubbing surfaces, and in the valves and cylinder of steam-engines, which is actually

necessary.

According to the general impression, grease or animal oil is a preserver of metal; but experience has shown that it is more frequently a destroyer, especially of the cylinders, pistons, and valves of steam-engines. The reason of this is, that vegetable and animal fats and oils contain stearic, megaric, and oleic acids, which, when subjected to the heat of high pressure steam, that frees them from their base, attack the metal and destroy it. This applies as well to oils of vegetable as to oils of animal origin, as fish or sperm oil. On removing the heads of steam-cylinders and the bonnets of steam-chests, the cylinders, pistons, and steam-chests frequently show evidence of corrosion, which differs entirely from that of ordinary wear, and which persons unacquainted with the nature and effect of the oil and grease they have been using, are puzzled to account for. Oils derived from petroleum contain no oxygen, cannot form acid, and therefore do not attack metal. The proof of this may be found in the fact, that such oils are used in surgical operations, and for cuts, bruises, and abrasions, with good effect. Oils from petroleum are produced for nearly every mechanical process, as well as for the cylinders of steam-engines, for which latter purpose animal oils were considered indispensable. At a recent meeting of the Railway Master Mechanics' Association, at St. Louis, a report was presented by the committee on lubricants, which embodied the result of a series of experiments made for the purpose of testing the lubricating qualities of different kinds of oil. In making the test, 56 drops of each variety