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Show LATEST MYSTEBY FOR AUTO READER Revolutions Per Minute New Factor in Putting Power in Motors. 'h !J. M." What do the m M.m w, i initial-. n.;w o common in the de-cr--tion ol' ai.y modern. Mgh ped ;utoint-bile. ;utoint-bile. Minify? With the advent of 1016 M-iison. ' 1 Yt. V. M . " h em:c into as common utgc a h. . t horC uwer . , the let! ors -u h i - Uv years nma ijl mi j nun h to the prospective Inner of a car. . ' R. P. M . " dues not stand for a brand of oipars. but in motor a-lauci means "Revolution:- Per Mi nine-"' iu shaft. When ab-mt four years ao a foreign-built racing car was brought to this count rv, and. although having a piston displace ment of cni v .lo cubic; inches;, .began showing more speed than the fastest cars then built, American engineers began to take notice. The solution they found was in-li.e high-speed motor a motor turning over -;U0 or more times each minute and since then the trend of Ame ican manufacture manu-facture has been in that direction. In view of the fact, " T P. M.'' iiotv plays such an important ra.t in the automobile au-tomobile industry, it is here explained how the change was brought about. First By reducing the weight of the moving parte;. Kvcry ounce taken -tY pistons and connecting rods reduced the force of the impact at the end of each stroke and saved eo much bvt power. Second -y reducing bore of cvli n -ders. 'This gave an explosion chnm.lier that allowed quicker combustion of compressed gas. Xor doe?- the stma force, of explosion drop as quickly as in largo bore, short stroke. Third Ry lengthening ihe pis-to"'"' stroke. More levprage N obtained ' n the cran k shaft. A small-bore. lon;:-stroke lon;:-stroke cylinder give the full power of the expanding gas. like the barrel of a rifle. There is also be! ter ' ' sea v en :"!'-ing,'' :"!'-ing,'' better charging nf cylinders and better compression. Fourth By enlarging the valve openings. open-ings. Large valve openings give quick passage to the burned gas leaving and the fresh, gas entering the combustion chambers. They also reduce back pressure pres-sure on the exhaust stroke. |