Fig. 27. End View of Mesta Engine.
The chrome-vanadium piston rod carries the pistons floating free from the cylinder walls reducing the wear on the bore, while the piston rings maintain a gas tight contact with the cylinder walls. Each piston rod is made in two halves, the joint between the sections being made between the cylinders at which point the rods are supported by an intermediate cross-head and guide. Both parts of the rod are interchangeable. The pistons are made in one casting. As will be seen from the accompanying cuts the front end of the piston rod is carried by a cross-head which relieves the pressure on the piston and packing glands.
Speed regulation is performed by the governor by controlling both the quantity and the quality of the mixture. Independent valves in the gas and air passages are actuated by the governor according to changes in the load. This method of control combines all of the good features of quantity and quality regulation.
Make and break ignition is used, with the igniter trip gear so designed as to allow all of the igniters to be timed from one lever, or adjusted independently as the case may require. Each combustion chamber is supplied with two igniters, one at the top and one at the bottom, which insures regular and rapid combustion and therefore gives a maximum of efficiency and reliability.
Compressed air is introduced into the cylinders for starting at a period corresponding to the power stroke in normal operation. This is accomplished by cam operated poppet valves located in the air main and check valves in the cylinders. By this system the engine can be started and put on full load in less than one minute.
(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.