Arizona republican., 1918-08-18
ENC|NES AND ENGINE: TERMS NIT ALWAYS UNDERSTOOD By
 PEOPLE RRE|N EXPLAINED

There are many engineering terms connected with the modern motor car which have gained currency among the general motoring public but which are scarcely if at all understood by the very people who employ them. Such term is high speed" with reference to .he engine and not 10 the vehicles rate of progress. And yet the modern high speed engine is so intimately con- nected with the future development of the motor vehicle that any one really interested in this field cannot afford 10 he without some understanding of what the term actually means and how the condition benefits the operation of the car.
 To begin with the term high speed is relative. There is no hard and fast line on one side of which the engine is low speed and on the other high speed. For instance a power plant having a maximum speed of 1 900 revolutions per minute. is certainly in the low speed class On the other hand when We find an engine with q maximum speed in the neighborhood of 5000 revolutions per minute we know that it is certain ly high speed power plant. The actual comparison of the two types comes when we find that al given car speed say twenty miles per hour. one engine is turning over 1000 revolutions per minute and the other more than twice as many.
 Not More Efficient
 Al first blush the neophyte might be puzzled to know where an engine that revolves twice as many times as it's rival to accomplish a given amount of work, could possibly be considered the more efficient. The explanation lies in this fact. that the high speed power plant with it's reduplicated revolutions IS accomplishing it's work through series of light taps so briefly spaced mat they come almost in continuous stream. On the other hand the low speed engine is delivering it's power in ScrleS of thumps. with greater inter Nals between. The high speed delivery or power makes inevitably for smoother and easier operation. without notico- able pause between the power-delivorv efforts. This characteristic is ohvious " intended for travel along a rather in oltferent surface where iolts and iars are certain to be encountered at best
 The present. day automobile power plant is an evolution from tho station Sry engine of yesterday In this en- I'nc. pellNerN CT power was pra ct iCa lIv inc only essential. It might come in a dtsjointed series of terrific wallops. what did the designers care. The en- sine was located on a permanent base. 't could he made very heavy to with- stand heavy internal blows. But when inls engine came 10 be transferred to -he chassis of a vehicle intended for road travel, the case was very different There was definite limit to the weight mat could bc carried and the delivery ot power had to be made in something like steady stream instead of in a series of terrific hiccoughs. So with The advent of tho automobile tho en- glneers at once began to study the problem of producing a smooth running power plant. The modern high speed engine. is the latest product of the pro- cess of engineering evolution.
 One of Essentials
 Ono of the essentials in the produc- ion of high speed engine is the uso of light rcciprocatinc parts. Tn tho operation of all rotating parts there is condition known as inertia. This