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Fig. 27.—Sectional View of Four-Cylinder Motor Having the Cylinders Cast in Block and Using a Two
Bearing Four-Throw Crankshaft.
Q. Name the other systems of valve construction.
A. The other forms of valves that have been evolved to replace the poppet type usually consist of some rotating or sliding member that uncovers ports, through which the gases pass.
Q. What is the Knight engine?
Fig. 29.-Conventional Methods of Operating Internal Combustion
Motor Valves. A—Valve Actuated by Rocker Lever and Tappet
Rod. B-Valve Operated by Simple Plunger Resting on the Cam. operates on the four-cycle principle and has two sliding sleeves which are placed inside the cylinder and interposed between the cylinder wall and the piston. These are given an up and down movement by small connecting rods attached to the sleeve at one
end and a small auxiliary crankshaft at the other These sleeves uncover ports which are formed in the cylinder walls.
Q. · What are rotary valves?
A. Rotary valves are forms in which the ports in the combustion chamber are opened by a revolving cyl nder or disc at a certain portion of its revolution.
Q. Describe action of typical rotary valve.
A. The Mead rotary valve motor utilizes a cylinder of metal placed at the side of the combustion chamber and driven at one-quarter the crankshaft speed by means of silent chain gearing. One of these cylinders is carried at Fig. 30.-Outlining Design of Typical Bevel each side of the cylinder
Seat Motor Valve. blocks, one serving to admit the gases into the combustion chamber, the other to provide means for their discharge. The operation of this orm of valve is very simple. A series of slots are mach ned in the revolving valve member and at the proper points in the cycle of operation these register with suitably formed ports in the combustion chamber and manifold respectively. (Figs. 33, 35.)
Q. What are piston and ring valves?
A. Inome engines a sliding member or piston is used to uncover ports in the cylinder walls as shown at Fig. 36 A or a reciprocating ring may perform the same function as in the Sphinx motor depicted at Fig. 37.
Q. What is a simple rule for size of inlet valve ?
A. The effective area of a valve port when the valve is fully opened should be a little greater than the size of the passage of pipe through which the gases enter the cylinder. The size of the intake passage as determined in usual engine practice may be found as fol ows:
Fig. 31.- End Section of Knight Engine Showing Sliding Sleeves
Which Replace Poppet Valves for Controlling Gas Passages.
1. The diameter of the passage is equal to that of the piston multiplied by .30 on slow speed engines and by .40 on high speed motors. 2. The area of the inlet passage is equal to one-eighth the area of jhe piston. 3. Intake passage area should equal area of piston muliplied by the speed of the piston in feet per minute and then divided sy 5000.