OCR Text |
Show E11JT1 OF M AUTOMOBILE Four Definite Types Hold Center of Stage; Various Reasons Advanced for Present Efficiency. In tho svime what more than f if toon years since the American mentor car passed from the experimental t?tape, no part of the mechanism has gone through a more Interesting process of evolution tharV the engine or motor, as it Is commonly com-monly railed. Many typos of power plants have come :md gone, and today construction has practically standardized four types the conventional poppet valve design, the air-cooled engine, the sliding sleve or Knight motor ami the steam power plant. In the years that have gone "before we have seen many other types make bids for popularity and for some reason or other fall. The list includes tho rotary-valve rotary-valve engine, the revolving cylinder, oscillating os-cillating sleeve designs, piston valve engines, en-gines, two-cycle plants, and others. Today To-day there is the Diesel, a definite type, which ha not yet been tried for passenger pas-senger car work, but Which looms up as a possible development of the future. We shall concern ourselves first with the four types that hold the cer.tcr of the passenger car stage today, as they alone are of practical interest to motor car owners. The poppet valve engine is the prevailing type. Nor are the reasons rea-sons for the supremacy of this type of power plant far to seek. It is cheap to manufacture, is simple in operation, is reliable and generally efficient. It is difficult to beat this array of qualifications. qualifica-tions. Pf5t Valves. ..One poppet valve engine ha-s the in-J in-J e and exhaust alves pla-ced at some " nion in the cyliifTler head. In the jppet valve engine, the valves or devices de-vices for controlling the flow of gases snd from the cylinder, are in the form ' o: Mechanically operated discs. Take a silver dollar, bevel the edge and fasten a stem pencil shaped to the center, and you have a poppet valve In appearance. The stem is moved by mechanical connection, con-nection, by means of a cam, so that as the cam turns around it strikes the intermediary, in-termediary, which in turn pushes the valve upward. The valve is closed by spring pressure. This type of engine is used on practically all modern automobiles. auto-mobiles. "While it has been demonstrated that other types of engines may give better service under certain conditions, it Is almost axiomatic that the poppet valve type gives greater returns on an equal exepndlture, and this is why it finds a place on most of our passenger j motor cars. I The air-cooled engine is used today by two makers, Franklin and Holmes. Both these engines are of the poppet valve type, but their radical difference in cooling method certainly entitles them to distinct classification. Among the obvious ob-vious advantages of the air-cooled power plant, one of the chief is the saving in weight through the elimination of the radiator, water Jackets, pump, etc. The freedom from freezing in winter is a point that the past few months have served to emphasize. Air Cooled Types. The air-cooled engine shows certain' definite economies over its water-cooled rival, principally through the weight saved. However, the water-cooled engine of the same-size as ah air-cooled one will give a greater power output. In ordinary service the question of power production is not a paramount one. After enough power is assured, more is simply excess, so that the air-cooled engine's limitations in this direction are more theoretical than real. The Knight sliding sleeve valve engine, en-gine, instead of the ordinary poppet . valve, utilizes sliding sleeves inside the cylinders. In these sleeves porte are cut and as the sleeves slides up and down the ports register with the manifolds and the cylinder. These sliding sleeves are irf operated by rods from an eccentric shaft, '- corresponding to the camshaft which op-""Sa-ates the poppet valves. The really ovtanding advantage of this construc-tioiVis construc-tioiVis its quietness in operation. The sleeves sliding up and down make, comparatively com-paratively speaking, no noise at all. Another An-other advantage is the freedom from carbonization car-bonization troubles; the formation of carbon car-bon has no bad effect on this design. In the early designs great trouble with lubrication lubri-cation was encountered, but that has all been overcome. One drawback of the type is Its inaccessibility In case anything goes wrong, necessitating dismantling to get at the Interior. The Steamer. Steam, which enjoyed a period of positive posi-tive pre-eminence, has fallen from that high estate, but still retains two adherents ad-herents in the Stanley and Doble stearn-. stearn-. ers. This propulsive medium is un-equaled un-equaled for flexibility, quietness of operation oper-ation and gives adequate power and speed. In its present exponents the factor fac-tor of economy (It uses kerosene), is a notable talking point and the old trouble trou-ble of frequent water replenishment has been obviated. In fact, there seems to be a well defined opinion that steam is about to undergo a rejuvenation. Having disposed of the living, we shall now hold a brief post mortem on types that have passed. Most important Is the rotary' valve engine, which uses by way of valves long bars of steel or iron, revolving re-volving in the cylinder head. These bars have ports cut in them and proper registration regis-tration with manifolds and combustion 'chamber, to insure entrance and emission of the fuel. Many engineers believe that the rotary valve is destined to a return in the not distant future. In the revolving cylinder enclne the cylinders revolve as a unit. In this type the crankshaft Is stationary and the oi-indera oi-indera revolve about it as a center. The Gnome airplane engine is perhaps the most noteworthy revolving cylinder engine, en-gine, but its greatest inherent fault is due to the fact that it Is a prodigious oil and gasoline consumer, and is noisy. Revolving Cylinder. Though revolving cylinder engines have KT tried for automobiles, notably in a marketed some years ago, as the v Artams-Farewell, the disadvantages as to ' f Siz' ue' efficiency, cost, etc., make it v. entirely unworthy of the name automo-bile automo-bile cntrine. f,7-- ao Iinal typo which we shall consider is the piston valve engine, which has never actually been used in passenger car construction, though many designs have been placed on the market. In this type small pistons are used to control the intake and exhaust ports. These pistons move up and down in their individual in-dividual cylinders just as the ordinary pistons do. While its adherents have claimed that the piston valve tended toward to-ward simplicity, their claims are scarcely scarce-ly borne out In practice. Knglnes of this type are bulky, the internal resistance is increased, lubrication is complicated and the valvo gearing is a!so complicated, compli-cated, with the additional disadvantage that it Is hard to get at and difficult tu repair. . To sum up, there is no present probability proba-bility of the poppet valve, water cooled engine being displaced tis the leader in the field. It is nnt the ideal power plant, but for a given expenditure it offers the most. L,ike everything in the engineer- . in" field; U is simply a compromise, and tvill continue to prevail until some! other compromise that embodies more of I the desired factors comes along to re- j .place it. |