Arizona republican., 1918-03-24

greater returns on an equal eXpendl- ture and this is why it finds a place on most of our passenger motor cars.
 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 entities them to distinct classification. Among the obvious advantages of the air cooled power plant, one of the chief IS the saving in weight through the elim- ination 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. The air cooled engine shows certain defln- ite economies over its water cooled rival, principally through the weight saved However the water cooled en- zine of the same size as an air cooled one, will give a greater output. In or dinary service the question of power production is not paramount one. After enough power is assured, more is simply excess, so that the air cooled engines limitations in this direction are more theoretical than real.
 The Knight sliding sleeve valve en- zine, instead of the ordinary poppet valve, utilizes sliding sleeves inside the cylinders In these sleeves ports are cut and as the sleeves slides up and down, the ports register with the manifolds and the cylinder. These sliding sleeves are operated by rods iron an eccentric shaft, corresponding to the camshaft which operates the poppet valves. The really outstanding advantage of this construction is its quietness in opera tion. The sleeves sliding up and down make, comparatively speaking, no noise at all. Another advantage is the free dom from carboniZation troubles; the formation of carbon has no bad effect on this design. In the early designs great trouble with fabrication was en- countered, but that has all been over- come. One drawback of the type is it's inaccessibility in case anything goes wrong, necessitating dismantling to get at the interior.
 Steam, winch enjoyed a period of po- sitive preeminence, has fallen from that high estate, but still retains two adherents in the Stanley and Doble steamers This propulsive medium is unequaled for flexibility, quietness of operation and gives adequate power and speed In its present opponents the factor of economy Git uses kero- sene) is a notable talking point and the old trouble of frequent water re- plenishment has been obviated. In fact there seems to be we'll defined | opinion that steam is about to undergo a rejuvenation.
 Having disposed of the living, we shall now hold brief post mortem on types that have passed. Most import ant is the rotary valve engine, which uses by way of valves long bars of steel or iron, revolving in the cylinder head. These bars have ports cut in them and proper registration with manifolds and combustion chamber, tC 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 engine | the cylinders revolve as a unit. IT this type the crankshaft is stationary and the cylinders revolve about it as g center. The Gnome airplane engine is perhaps the most. noteworthy revolv- ing cylinder engine, but its greates'
 inherent fault is due to the fact tha- it is a prodigious oil and gasoline con- sumer and is noisy Though revolving
 cylinder engines have been tried fol automobiles, notably in a car marketed
 some years ago as the Adams Farewell
 the disadvantages as to size, fuel ef. ! ficiency, cost, etc. make it entirely un-