Speedometer

“ The automatic speed control system, which functions in signalized territory, is connected to the locomotive cab signal, it is independent of and not connected to the locomotive's speedometer and event recorder. If the locomotive engineer fails to reduce speed to the authorized level in cab signal territory, the speed control automatically triggers a brake application to slow and stop the train Signal 226 2 at Ruggles Street was not coded to provide the 30-mph speed restriction at MP 227. ”

“ All the half-dozen makes are good ones. A speedometer is a very interesting accessory, for it tells you exactly the pace at which you are travelling, and in some instances has been known to influence the decision of a magistrate when deciding a charge of exceeding the speed-limit. ”

“ Better stop the auto at every crossing if the noise of the motor prevents hearing whistle or bell signals from the train.
But there is a worse dereliction than failing to make sure that a train is not at hand, and that is the devil-may-care spirit which prompts driver to spurt up the engine and dash for the crossing to get over ahead of the train that is in plain sight. There are few persons who can estimate the speed of a railway train with any degree of accuracy, even the railway employes having to check the time between known points to estimate the speed, unless there is a speedometer. ”

“ And his the Viking sky boat that first dared the fierce gale of the wind path!
The gale he was riding gathered power. His speedometer mounted erratically, jerking up records of additional fives and tens of miles. Ten—twenty, thirty—four hundred and forty miles per hour.
A curious vibration of his engine startled him. But he drove away all thoughts of danger. The mileage was a magnet that held his eyes. Speed, speed! Riding high and fast! The sky was his height limit. He was reeling off a record. He must hold to it, must speed on.
Riding higher and faster than any human since creation! ”

“ The radio boys laughed and sang, cracked jokes, and waved to passing cars, while the mileage record on the speedometer mounted steadily up. The sun was still quite a way above the western horizon when they reached the place where the forest road branched off from the main highway. The driver tackled this road cautiously, and they soon found that his description of it had not been overdrawn. It was a narrow trail, in most places not wide enough for two cars to pass, and they wondered what would happen should they meet another car going in the opposite direction. ”

“ Ground the wire on engine. Turn ignition and light switch on. Lamp should light. If it does not light, check wire for condition and/or replace lamp after removing panel cover (par. 119) . If lamp and wiring are satisfactory, replace oil pressure switch.
121. SPEEDOMETER HEAD. a. Remove. Remove instrument panel cover (par. 119) . Loosen the two tank front mounting bolts and remove rear mounting bolt to free speedometer cable clamp. Disconnect speedometer cable at drive unit. Free cable from clip located below tool box. Remove two screws which mount head to frame. ”

“ The transmission of power by a strap is familiar to every one in a treadle sewing-machine or an ordinary lathe. The driving force depends on the difference in the tightness of the two sides of the belt, and the power transmitted is equal to this difference multiplied by the speed; a power-meter must, therefore, solve this problem—it must subtract the tightness of one side from the tightness of the other side, multiply the difference by the speed at every instant, and add all the products together, continuously representing the growing amount on a dial. ”

“ The carriage may be driven at any assigned speed by adjusting the governor of the driving engine already alluded to, but the record of the speed by means of the time and distance diagrams is more definite. When the resistances of the model have been obtained at several speeds, varying in some cases from 50 to 1,000 feet per minute, the speeds are set off in suitable units along a base line, and for every speed at which resistance is measured, the resistance is set off to scale as an ordinate value at those speeds. ”

“ As we rush on past countless signals, punctual to the minute, yet always having ample time to slacken speed before we come to the places where the different colored lights cluster thickest, we are reminded once more how much is required of an express engine-man besides a thorough acquaintance with the machinery he has to control. Traveling at night at a great speed, he must know every inch of the road by heart—where an incline begins and where it ends, and the exact spot at which every signal along the line may be first sighted. ”

“ Thus, if the calculated speed of the second gear is, say, eighteen miles per hour, the driver should wait until the work of surmounting the gradient has caused the engine to slow the pace down to that, and not try to make the change when the car is still doing twenty. Some little practice and intelligent observation is necessary before this can be nicely done, but that sort of thing is where much of the charm of driving a good car comes in. ”

“ You are now on third (or top) gear and will find that unless the country is very hilly you will usually be able to keep the car running on this gear for a long time, varying the speeds from 10 to 28 miles an hour by deftly manipulating the ignition, air and throttle.
Changing speed on the car illustrated is an easy task, and that is why I have taken the De Dion car as an object-lesson. With the majority of cars there is a deal of “arm work” necessary, and in many cases not a little strain, this strain very often counteracting the benefits otherwise derived from the driving. ”

“ Hooded dials, brightly lighted push-buttons, a telephone headpiece and receiver combined, and switches all lay in easy reach. Here was the tachometer, that would give to a fraction the revolutions of each screw per minute; here the altimeter, to indicate height; here the air-speed indicator, the compass with reflector, the inclinometer, the motometers—to show the heat in each engine—and there, the switch to throw on the gigantic searchlight, with the little electric wheel to control its direction, as accurately as you would point a wand. ”

“ After the driver becomes a little experienced he may shift from third to second without sound at practically any car speed that the engine is able to deliver on second gear. This may even be found of value when climbing steep hills and in anticipating necessary shifts. To make this shift at high speed, release the clutch, shift gear lever to neutral notch, engage clutch, and accelerate engine speed to a point which experience tells you is the correct engine speed for second gear at that car speed, disengage clutch and shift into second. ”

“ The law that the driving force required increases as the square of the speed imparted applies only to the original source of power, as, to the force of the steam exerted in the cylinder of an engine, the motion of the piston remaining the same, and to the transmitting belts or gears whose speed also remains the same. At all these points the force exerted must increase as the square of the speed imparted; but this does not apply to the pressure exerted in the governor joint. Its speed does not remain the same, but increases with that of the balls. ”

“ And that man should have constructed an engine so nicely adjusted in all its parts as to utilize this power is little less than a miracle of mechanics.
A word should be said about another interesting mechanism that pertains not indeed to the speed of the automobile, but to an accurate record of that speed. That is an electrical timing-device with which absolute accuracy of timing is assured. A moment's reflection will show that it would be quite impossible to time the automobile moving at record speed by the172 old stop-watch method. ”

“ All machines have signaling horns of some character, operated, usually, by some mechanical arrangement connected with the gearing or by compressed air, and others are connected up with the engine exhaust. Chime whistles are so operated.
Speed Signals.—Other inventions are designed to indicate, by automatic mechanism, the speed of the car, in which color displays the relative speed. Thus, a car going at the normal speed, say 10 (163) miles per hour, would show a white light ”

“ Now in two-fifths of a second, as we have seen, the record motor car covers a distance of over 77 feet. Obviously such latitude in measurement could not be permitted. Hence an electric device has been elaborated which tests the speed with absolute accuracy, recording it automatically on a strip of tape. Therefore the fractional seconds are now stated in hundredths instead of in mere quarters or fifths, and we may be confident—as we could not always be regarding the old-time records—that the different fractions of a second represent an actual difference of speed. ”

“ Thus, if an electric tramcar starting from rest attains its full speed of 24 miles per hour in the time of 20 seconds, its average acceleration is 1.2 miles per hour in each succeeding second, or "1.2 miles per hour per second." If instead of giving the speed in miles per hour we give it in metres per second, the acceleration of this car would be 0.535 metres per second per second. Taking the metre as the unit of length, the second as the unit of time, and the kilogram as the unit of force, we have thereby also settled what the unit of mass must be. ”

“ A very good formula to follow in regard to changing speeds is to continue on the speed on which you are running until the engine cuts out or shows signs of extra vibration or noise, which will at once indicate to you that it is running faster than it ought, and that it is desirable to change on to the next speed. This will ensure there being a good run on the car, and that the next higher speed will take up the run and increase the pace. ”

“ To accomplish this, first get the vehicle running as fast as possible on the first speed, then press down the left pedal quickly, push the speed lever firmly into the second forward notch, and lift up the left pedal gently as when starting. You are now on the second speed, which you will no doubt observe is considerably faster than the lower speed, and the novice should familiarise himself with this in the same way as on the first speed, i.e. letting the car run short distances and thus becoming accustomed to the speed. ”

“ There are no balance weights, and the screw regulates the movement. There is also a very ingenious speed indicator, which consists of a small brass case filled with water, in which is a small fan driven by a cord from the driving wheel; a copper pipe leads from the fan case to a glass gauge tube; the faster the fan runs the higher the water will stand in the tube, thus indicating the speed. ”

“ The change-speed mechanism, to which the clutch transmits the power of the engine, is to the engine what a block and tackle is to a man who lifts a heavy weight, and is necessary because of the varying resistance to the movement of the car in traversing steep, rough hills and smooth avenues. A change-speed mechanism may be defined as an arrangement by which the relative number of revolutions of the crank shaft and driving wheels may be altered to suit conditions. ”

“ Even the best and most unbiassed judgment ought not to be trusted when mechanical evidence can be produced. The first rule I propose is, that—
Every engine should have mechanical self-registering means of recording its own velocity at every instant during the whole course of its Journey.
In my own experiments this was the first point I attended to. I took a powerful spring clock, with a chronometer movement, which every half second lifted a peculiar pen, and left a small dot of ink upon the paper, which was moving over a table with the velocity given to it by the wheels of the carriage. ”

“ The air-speed meter, whether of the Pitot type or pressure-plate type, will prove invaluable in flying through clouds or mist when the ground is obscured. Also the inclinometer is able to give the angle of flight when the earth is not visible, although the speed indicator usually is sufficient to give the angle of flight, for an increase of speed means downward motion and decrease of speed means upward motion. ”

“ A. The different speeds required to meet road conditions are obtained by opening or closing the throttle. Practically all the running speeds needed for ordinary travel are obtained on high gear, and it is seldom necessary to use the low gear except to give the car momentum in starting. The speed of the car may be temporarily slackened in driving through crowded traffic, turning corners, etc., by “slipping the clutch,” i. e., pressing the clutch pedal forward into neutral. ”

“ But the moment the plane is either augmented or retarded by favorable or unfavorable winds, the air-speed indicator becomes a very unreliable instrument for showing distances traveled: it practically only records the speed of the air pushed past the plane. It is like running at ten miles an hour with a pin-wheel in the hand on a perfectly calm day, and getting a certain velocity of revolutions of the wheel per minute. On another day one might stand still with the pin-wheel and permit the rush of a high velocity of wind to twirl it round with the same speed. ”

“ Now there are very obvious limitations to the procedure just given. If the street car is going too fast, we can not board it directly, but must use devices, such as getting on from a moving automobile; and, more important still, there are limitations to the velocity that can be given to street cars or to meter sticks by any practical means in our control, so that the moving bodies which can be measured in this way are restricted to a low range of velocity. ”

“ If an automobile could run at an unvarying rate of speed, if there were no hills which require the translation of speed into power, or if the engine131 controls alone could give sufficient speed regulation to cover the emergencies constantly arising, the transmission might be simplified into a mere coupling and reverse. But simplify as you will, there must be provision for varying speeds and these must be attained while the car is in motion, and this means the meshing together of finely built gears revolving so fast the teeth cannot be seen. ”