Practical Hand Book of Gas, Oil and Steam Engines / Stationary, Marine, Traction; Gas Burners, Oil Burners, Etc.; Farm, Traction, Automobile, Locomotive; A simple, practical and comprehensive book on the construction, operation and repair of all kinds of engines. Dealing with the various parts in detail and the various types of engines and also the use of different kinds of fuel.

by John B. Rathbun

(49) Knight Sliding Sleeve Motor.

The Knight motor was the first four stroke cycle automobile motor to employ an annular slide valve in place of the usual poppet valve. Its success has led to the development of several other motors of a similar type which follow the construction of the original engine more or less closely. Being free from the slap bang of eight to twelve cam actuated poppet valves which hammer on their seats at the rate of a thousand blows per minute, the Knight motor is free from noise and vibration. Instead of the jumping of a number of small parts, there is only the slow sliding of the sleeves over well lubricated surfaces. They make no noise because they strike nothing and can cause no vibration because they are a perfect sliding fit in their respective cylinders.

Besides insuring noiseless operation, the valves increase the output, efficiency and flexibility of the motor for they are positively driven and are not affected in timing by fluctuations in the speed. The wear of the reciprocating increases the efficiency of the sleeve instead of destroying it. With poppet valves at high speeds, the valves do not seat properly in relation to the crank position owing to the inertia of the valves and to the gradual weakening of the valve springs which delays the closing of the valves. Carbon also gets on the seats of the poppet valves and prevents proper closure. These faults cannot exist with sliding sleeves when they are once set right as they are positively driven through a crank and connecting rod.

Fig. 28. Section Through Knight Motor Showing the Sleeves, Eccentrics, and Automatic Adjustment for Lubrication. Inlet is at the Right, Exhaust at the Left.

At high engine speeds the velocity of the exhaust and inlet gases is very high in the poppet valve type due to the many restrictions and turns in the passages which causes back pressure and a considerable loss of power. With the sliding sleeve type an ideal form of combustion chamber is possible and the passages to and from the chamber are short and direct. Very large port areas with a low gas velocity are also possible. The sleeves are more effectively cooled than the poppet type, being in direct contact with the water cooled walls for their entire length. Because of the large port areas, the cylinders receive a full charge of mixture, and as a result the engine accelerates and gets under way with remarkable ease.

Figs. 28–29–30. Showing Sleeve Positions on the Inlet Stroke. (Knight Motor.)

The arrangement of the slide valves, or sleeves, is shown by Fig. 28, which also gives an idea of the cylinder form, and the location of the piston. Fitting the engine cylinder closely, one within the other, are the two sliding valve sleeves, and within the inner sleeve slides the power piston.

Figs. 31–32–33. Showing Sleeve Positions on the Exhaust Stroke.

Each sleeve has two slots cut in it, one on each side, which form an outlet and inlet for the exhaust and inlet gases respectively. When the slots on the intake side of both the outer and the inner sleeves register, or come opposite to one another, and also opposite to the intake pipe, a charge of gas is drawn into the cylinder. After the explosion has taken place, the sliding motion of the sleeves brings the other two openings, on the exhaust side, opposite to one another, and opposite the exhaust pipe, which allows the burnt gas to escape to the atmosphere through the exhaust manifold.

The sleeves are driven from cranks on the half-time shaft shown at the side of each cut, through the small connecting rods, which gives them a reciprocating motion. Like the cam shaft on a poppet valve motor, the lay shaft runs at half the crank shaft speed, since the engine is of the four-stroke cycle type. The lower ends of the sleeves, to which the connecting rods are fastened, are made thicker than the portion within the cylinder, and are heavily ribbed for strength in the overhang.

The sleeves are of the same composition of cast iron as the cylinder and are provided with oil grooves cut in their outer surfaces for gas packing, and the distribution of oil. Leakage between the inner sleeve, and the cylinder head is prevented by a packing ring, or “junk” ring that is fastened to the bottom of the inwardly projecting cylinder head. The junk ring not only prevents the leakage of gas during the explosion, but it also serves another purpose.

The exhaust ports or slots in the inner sleeve are above the junk ring during the explosion, in which position they are protected from contact with the burning gas. The life of valves is greatly increased by this protection. It will be noted that the entire surface of the sleeves is in contact with water jacketed surfaces, making perfect lubrication and smooth working possible. The two spark plugs for the dual ignition system are shown in the depressed cylinder head.

Complete water jacketing encircles the cylinders, cylinder heads, the circulation area enclosing the plugs and the gas passages so that a uniform heat is maintained the entire length of the piston travel.

The half-time shaft, the magneto, and the water pump are driven by a silent chain from the crank case; this drive being found superior to the gears commonly used for this class of work. The cranks on the half-time shaft are made in one integral piece with the shaft.

Although the piston on the Stoddard-Dayton Knight motor has a stroke of 5½ inches, it is scarcely as much as this considered as friction producing travel, because the inner sleeve in which it rests moves down in the same direction 1⅛ inches.

This distribution of the working stroke to two surfaces reduces the wear on the side of the sleeve caused by the angularity or thrust of the main connecting rod. On the compression stroke, both outer and inner sleeves go up in the same direction as the piston, the inner sleeve moving the faster. On the exhaust stroke and suction stroke the sleeves move in a direction opposite to the direction of the piston, but on these strokes there is very little work performed by the piston and consequently little thrust is produced on the sleeves and walls of the cylinder.

It is a valuable feature to have the sleeves descend with the piston on the working stroke because this is the stroke in which the piston has the greatest amount of side thrust.

The up and down movement of the sleeves is very little compared with that of the piston. A stroke of 5½ inches gives a piston speed of 916 feet per minute at a speed of 1,000 revolutions per minute. The stroke of the sleeves is 1⅛ inches and its speed is but 93.7 feet per minute, or a little more than one-tenth that of the piston. This fact makes the problem of lubrication a feasible one, the slow-movement of the sleeves distributing the oil thoroughly between them as well as between the outer sleeves and the cylinder walls.

The action of the valves, and their position at different points in the cycle, is shown in diagrammatic form by Figs. 28–29–30–31–32–33, the particular event to which each diagram refers being marked at the foot of the cuts. The direction of the sleeve movement is indicated by the arrows at the bottom of the sleeves. Particular attention should be paid to the position of the slots in the sleeves.

The first three diagrams show the position of the inlet slots that govern the admission of the combustible gas from the carburetor. Fig. 28 shows the slots coming together to form an opening in the inlet port as the lower edge of the outer sleeve separates from the upper edge of the inner sleeve. The outer sleeve is now moving rapidly downward while the inner sleeve is slowly rising, and as their motion is opposite the opening is quickly formed. Fig. 29 shows the full opening with the slots in register.

When closing (Fig. 30) the outer sleeve is nearly stationary while the inner sleeve is rising rapidly. When the inner sleeve port is covered by the lower edge of the junk ring, the valve opening is closed, the slot in the outer sleeve remaining opposite the inlet opening.

The exhaust port opens (Fig. 31) when the lower edge of the slot in the inner sleeve leaves the junk ring in the cylinder head, the sleeve moving rapidly downward at the moment of opening. To obtain a rapid opening of the exhaust, the ports are arranged so that the inner sleeve is just about to reach its maximum speed at the time of opening.

The outer sleeve closes the port (Fig. 33), closure starting when the upper edge of the outer sleeve coincides with the lower edge of the cylinder wall port. At this time the outer sleeve is traveling downward at maximum speed, so that the closing of the exhaust is as rapid as the opening.

The lubrication of the Knight motor is accomplished by what is known as the movable dam system, which overcomes the tendency of the motor to over-lubricate. A movable trough is placed under each connecting rod, in the crank case, that is connected to the carburetor throttle lever in such a way that the opening and closing of the throttle raises and lowers the troughs.

When the throttle is opened, raising the troughs, the points on the ends of the connecting rods dip deeper into the oil which creates a splashing of oil on the lower ends of the sliding sleeves. In this way the oil is fed to the engine in direct proportion to the load and the heat produced in the cylinder. When the motor is throttled down, the points barely dip into the oil.

An excess of oil is fed to the troughs by an oil pump, which keeps them constantly overflowing. The overflow is caught in the pumps located in the crank case, and returned to the circulation so that it is used over and over again.

Claims of great efficiency are made for this system, there having been many tests made showing 750 miles per gallon of oil, while even as high as 1,200 miles per gallon has been made under favorable conditions.

The oil pump is contained in the crank case, and is of the gear type, insuring positive action. The pump also acts as a distributer, a slot being cut in one of the gears which register successively with each of the six oil leads. In this way it is possible to obtain the full pump pressure in each lead should they become obstructed in any way.

In the upper half of the crank case are cored passageways through which the air passes before reaching the carburetor. These passages not only eliminate the rushing sound of the intake air, but also form an efficient method of warming the air supplied to the carburetor and cooling the crank-case. It is possible to furnish warm air after the engine has been idle for several hours, as the oil in the crank case remains warm longer than any other part of the engine.