IN THE usual auttmobile poppet valve the poppet or mushroom valves are lifted from their seats by cams and reseated by springs. In a four·cycle motor, the valves in each cylinder are Oiened and closed once in ,two revolutions of the crank shaft. This intermittent movement of the valve must be produced by a cam and a spring mechanism. The valve is not closed until it is in actual contact with its seat. Hence the valve mU8't be free to seat itself under the action of the spring. Noise is produced when the cam strikes the valve to lift it, and also when the spring strikes the seat and start8 to close the valve. This noise in itself indicates a tendency to wear. In the usual construction there is no way to provide for wear. Furthermore, neither cam nor spring is suitable for high speed work. While the poppet valves work well at low speeds, they are unreliable at high engine speeds, and the “timing,” or opening and closing of the valves, is uncertain. This is the gravest objection to th' poppet valve. By a radical change in design, Charles Y. Knight of Chicago has produced a design of valve for the fourcycle internal combustion motor, a design in which all the inherent disadvantages of the poppet valve are eliminated. For .ome time !rior to 1908, Mr. Knight manufactured anrl marketed in small quantities an automobile called the “Silent Knight.” The claim for silence lay in the motor. Although successful enough, the car, owing perhaps to lack c detailed refinement and the use of the new motor, did not appeal to the aUtomobile trade. Knight, whose chief interest was in the motor itself, thereupon took his invention to England, and succeeded in interesting the English Daimle:' Company in it. After many tests and further development and refinement the English firm adopted it. Almost . immediately the engine became the subject of much discussion and investigation by British automobile and technical soeieties, culminating in an exhaustive test by the Royal Automobile Cluh. As a part of this test a 38 horse-power motor (4 % inc]l bore and 5% inch stroke) was run continuously for 132 hom's under a load of 54 horse-power. The motor waH then placed if a chassis and driven for 2,001 miles on the famous Bro'l:-lands track. Next it was returned to the testing rack and run for five hours more and developed 57 horsepower. Under the conditions of this test the load on the testing rack was never to be less than 1.3 times the calculated horsepower of the motor. The roa1 test was to be made at a speed of not less tha I 40 miles per hour and the final return of the engine to its bench test was to determine its final eondition. These extraordinary eondi Lions of the test were insisted upon by the Daimler Company, and the final bench test was especially desired by them. The reason is apparent when it is noted that the hors8power developed was in excess of the power developed at the start of the test, both tests being at the same engine speed-l,200 revolutions per minute. Evidently the Daimler Company reasoned that while it might be possible for a poppet valve engine to meet the first and second stages of the test it was obviously impossible for such a motor to meet the fnal stage, i. e., to develop more power, to be in better condition after continued running. After the motor had snccessfully withstood the test, the Daimler Company was awarded the Dewar trophy and the .motor received the unqualified official indorsement of the Royal Automobile Club's technical committe!, Extensive tests and experiments have been made on the motor in this country, with the result that three American firms have secured licenses. In a few years the new motor will be as well known here as it is abroad. The motor is not really valveless, nor is it in any way akin to the two-cycle motor. Knight's invention is a mechanical or structural improvement in the design of the valve mechanism. The valve mechanisr consists of two concentric sleeves sliding up and down between the piston and cylinder walls. Certain slots in theBe valves register with one another at proper intervals, producing large and direct openings into the 'Combustion chamber from the exhaust and inlet ports in the cylinder. The sleeves are operated by smlll connecting-rods from a small crank shaft or eccentric shaft running at one-half the speed of the mam shaft. }ig. 1 shows the general arrangement of the parts and their nomenclature. The detail operations of the valves can best be seen by a glanee at the seven diagrams comprising Fig. 2. In the diagrams the relative positions of the inner and outer sleeves at various pOints in the cycle of the motor are indicated. The method of reciprocating the ¦sleeves by connecting rods from the eccentric shaft is shown. The eccentric shaft is positively driven, by a silent chain, from the main crank shaft and rotates at one-half the speed of the motor. The eccentric operating the inner sleeve is given a certain advance or “lead” over that of the outer sleeve. This lead, together with the rotation of the eccentric shaft at half the crank shaft speed, produces the cyCle of operations. In the first diagram the piston is just past its tOlp center, and is starting down on its inlet stroke. The inner sleeve is at the bottom of its travel and moving slowly Tpward, the outer sleeve is about midway in its travel and is mol'-ing downward rapidly. The opening from the carburetor through the inlet port into the cylinder is a rapidly increasing space between the upper edge of the slot in the inner sleeve and the lower edge of the slot in the outer sleeve. By the time the piston is a little more than half way down on the suctio! stroke the inlet passage is wide Open as shown in the second diagram of Fig. 2. The outer sleeve is now at the bottom of its stroke and moving very slowly, the inner sleeve is gaining in speed moving upward; and the inlet is closed by the lower edge of the inner sleeve slot in passing the upper edge of the outer sleeve slot, as shown in the third dia gram of Fig. 2. The inner sleeve continues to move up with the piston on its compression stroke, the rings in the head and piston tightly sealing the eompression space, until the explosion occurs. The sleeves and piston are then in position shown in the fourth diagram. About two-thirds of the way down on the explosion (Continued on page 176.)
This article was originally published with the title "The Knight Valveless Engine"