Piston

“ The piston is made to admit steam or air into the cylinder, and to cut off the supply, and to open the exhaust, as required, by means of tappet valves, or other suitable devices; and provision is made to allow, within certain limits, a variation in the length of the stroke. During a portion of the stroke, means are brought into action to cause the piston to rotate to some extent, for the purposes that have been already explained. To keep the cutting edge of the tool up to its work, the whole machine is moved forward as the rock is cut away. ”

“ This simple form of piston is used in the steam-engine indicator, and also in pumps.
Fig. 46 shows the piston of the circulation pump of a marine engine. A is the cast-iron casing or barrel of the pump; B is a brass liner fitting tightly into the former at its ends, and secured by eight screwed Muntz metal pins C, four at each end; D is the piston, which is made of brass, and is attached to a Muntz metal piston rod E. The liner is bored out smooth and true from end to end, and the piston is turned so as to be a sliding fit to the liner. ”

“ The upper end of the piston is continued above the top division head of the chamber A, and the extension is provided with the slot F. Near the center of the piston, the walls of the piston are run out into a flat circular plate or trunk piston E, which is the actual piston head that receives the force of the explosion. The piston E reciprocates in the large cylinder H, which is reduced at its upper end to the diameter of the main piston barrel, for which it affords a sliding support, or guide, and also serves to aid the exhaust port closure. ”

“ As the cut-off can be made at any point of the stroke, and the expanding gases allowed to do the work of the remainder, the piston is subjected to a pressure entirely similar to and as readily controlled as that exerted by steam in the steam-engine. The piston is lubricated by its lower edge dipping into a shallow pan, F, at the bottom of the cylinder, containing oil, and the other parts in the ordinary manner. The motor is easily and quickly stopped and started, and when running requires but little attention. ”

“ The working piston is easily taken from the cylinder by removing the cylinder head and the four nuts that fasten it to the differential piston casting. The displacement of the differential piston is approximately 1.9 times the displacement of the working piston which is more than enough for thoroughly scavenging the cylinder and supplying air for combustion. The air suction is controlled by a piston valve which eliminates much of the loss encountered in the marine type of two stroke cycle. ”

“ Now put your finger on the opening of the nozzle firmly, so as to stop any water from passing out, and then try to push the piston down. You will find that you cannot make it stir without great force; and, if the piston moves appreciably, it will be because some of the water has escaped by the sides of the piston. In fact, if the piston presented a square inch of surface, and fitted accurately, and the column of water in the cylinder were one inch long, it must be pressed down by a weight of 30,000 pounds (about thirteen tons) to make it move one-tenth of an inch. ”

“ Lubrication is a subject that should be studied by every gas-engine user. So far as the piston is concerned it is a matter of the utmost importance. The piston does its work under very peculiar conditions. It is driven at great linear velocities; and it is, moreover, subjected to high temperatures which have nothing in common with good lubrication if care be not exercised.
The piston is the essential, vital element of an engine. Upon its freedom from leakage depends the maintenance of a proper compression, and, consequently, the production of power and economical consumption. ”

“ The cover, when bolted on, forms a part of the cylinder; the piston rod is cast solid with the piston, and is made sufficiently large at its outer end to receive the tool. These two parts constitute an engine, and with less than one fixed and one moving part it is obviously impossible to develop power in a machine by the action of an elastic fluid. ”

“ The indicator piston actuates a pencil, which rises and falls with it and traces the diagram on a sheet of paper fixed to a drum that is caused to rotate back and forth through a certain arc, in unison with the motion of the engine piston. ”

“ A piston makes a tremendous pound when a badly connected rod allows it to touch a cylinder-head, and a very ominous pound is produced when the spider gets loose on the piston-rod, and a piston-rod loose in the cross-head will make itself heard all over the engine. ”

“ Let a piston be substituted for the cannon ball, as was suggested by Huygens in 1680 and by Papin in 1690, and the charge of powder so reduced that when it is exploded the piston will not be thrown entirely out of the cylinder, another small explosive charge introduced on the other side of the piston to force it back, or let the cylinder be vertical and the piston be driven back by gravity, means provided to permit the escape of the gas after it has done its work, and means to keep the cylinder cool, and we have the prototype of the modern heat engines. ”

“ The piston in gas, oil and air engines has a similar function, but in a pump, instead of imparting motion, it has motion imparted to it by some prime-mover. In every case the piston must fit the cylinder so accurately that as little as possible of the working fluid, whether it be steam, gas or Water, can escape past it, packing of various forms being commonly placed round its periphery in order to secure this fit. ”

“ The follower of a piston is a plate or cover that is employed to hold the piston rings in place, and the piston rings should be so fitted that the follower should be bolted firmly up, or otherwise the bolts may come loose and work out, and getting between the piston and the cylinder cover, may cause the piston to knock the cylinder cover out. ”

“ When the piston reaches the top of the cylinder, the sliding bridge or valve has its direction changed, so that the pipe r, and consequently the bottom of the cylinder, is connected with the condenser, while a passage is opened from the pipe m n to the steam box. Thus a communication is alternately made between the top and bottom of the piston. ”

“ A snap piston ring is one that is larger in diameter than the cylinder bore, and is closed in to get it into the cylinder, while it depends on its own spring outwards for its fit to the cylinder bore, having no supplementary rings or springs to force it out. ”

“ When the main piston has completed one stroke, it moves backward on its return; the arm strikes against the other cam on the valve stem and communicates a reverse motion to the valve which closes and opens the alternate ports to admit and exhaust steam to and from the pistons. It also cushions the piston at the end of each stroke which prevents the piston from striking the heads. ”

“ The packing of the piston now gives us little or no trouble, it goes from a fortnight to a month, opening the top now and then to screw it down, as it gets slack, which should be attended to. We use no grease or oil in packing the piston or working the engine, having found blacklead mixed with water, and poured 'a little now and then' through a hole on the top into the steam-cylinder, suits the packing of the piston much better, and is cheaper than anything else. About 1s. worth of blacklead will last our engine a week. ”

“ The piston is held on an expanding pin chuck which is so constructed that all of the pins are forced outward with equal pressure and automatically conform to any irregularities on the inside of the piston. ”

“ Each piston as it ascends draws into the annular space under it a supply of gas and air in proportion regulated by the cocks or valves, and as it descends it forces this charge into the interior of the revolving valve and its casing, and into the reservoir which communicates therewith. When either piston is at the top of its stroke, the revolving valve admits to the upper part of the cylinder a supply of the gaseous mixture from the reservoir and valve casing, and this passes through the generator. ”

“ The right-hand main steam piston must wait until the left-hand piston has completed its stroke before it can reverse, and consequently the movement of the main pistons will always be in opposite directions, and neither can reverse until both have completed their stroke. ”

“ I saw at a distance of fifty feet a 22-inch piston being finished for an engine we were building for the Tremont and Suffolk Mill. The workman had finished turning the piston and was then cutting the grooves for the rings. The reflection from the surface showed me the same two cones meeting in the middle. I went up to the lathe, the back side of which was toward me, and told the workman to stop his lathe and bring me a straight-edge. This rocked on the edge in the middle of the piston, opening nearly one eighth of an inch on each face alternately. ”

“ The upward stroke of the piston, with its attached hammer-block C, is arrested at the proper height not only by allowing the steam that raised it to escape, but as soon as the piston passes the escape holes X X, the confined air above the piston at O rebounds, and so aids most effectively in increasing the energy of the fall of the hammer-block C on the pile head. ”

“ The piston placed on some branch of the main tube must be so constructed that on being depressed it closes the natural windways through the main bore and opens others into the additional piston length. ”

“ This spring is to be made of such strength as that when the whole weight of the atmosphere is upon the piston the air will only move it about one inch down. E is the tube leading from the axle, which is hollow from the top to the level of the wheel, so as to admit the external air by this tube to the piston D, which piston is a circular vessel, made air-tight, and exactly fits the cylinder. There is a joint in the tube E at F, which is made air-tight by leathers, so that when the piston descends the tube may give way to it. ”

“ It is important for the proper functioning of the piston in a gas engine that it should fit the explosion chamber closely so as to conserve power, prevent the passage of lubricating oil around the piston into the chamber, and insure the smooth and noiseless movement of the piston within the cylinder. ”

“ The piston-rod A is acted upon by the gas pressure at its forward end, and is driven to the rear against a strong spiral spring o, which moves the piston end forward after the gas pressure has ceased to act. ”