Rotor

“ The fact that the propelling force only comes into existence when the initial spin is sufficient to eject the dead water from the leading side of the rotor blade fully explains the observed fact that a very considerable initial spin is necessary. ”

“ As the friction of the rotor plates on the water heats it in exact proportion to the amount of power absorbed, the small amount of water in the drums would be soon converted into steam unless continually renewed or cooled. ”

“ Then tighten up the nuts and insert the other bolts, the three lowest of which are passed through the feet. Affix the pulley and stirrup, and adjust the spindle longitudinally until the rotor just does not rub the casing. The soldering on of the cap of A completes operations.
To get efficiency, heavy gearing down is needed, and this can be managed easily enough with the help of a clockwork train, decreasing the speed five or more times for driving a dynamo, and much more still for slow work, such as pumping. ”

“ The words are self-defining; a winding is said to be revolving or stationary according as the armature forms the rotor or stator of the machine.
Ques. What is the significance of the terms lap and wave as applied to alternator windings?
Ans. They have the same meaning as they do when applied to dynamo windings.
Fig. 1,487.—Section of General Electric stationary armature ventilating ducts and winding in position.
These are described in detail in Chapter XVIII. Briefly a lap winding is one composed of lap coils; a wave winding is one which roughly resembles in its diagram, a section of waves. ”

“ I find that when I walk backwards as quickly as is convenient, pulling the rope all the time, the scale shows a tension of about 50 lbs. To set the wheel rapidly in motion, I pull about 20' of rope from the axle, so that I have imparted to the wheel somewhere about 50 × 20 = 1,000 units of energy. The rope is fastened to the shaft, so that, after it has been all unwound, the wheel now rapidly rotating winds it in. By measuring the time in which the wheel made a certain number of coils of the rope around the shaft, I find that it makes about 600 revolutions per minute. ”

“ In the rotary design the crankshaft of the engine is stationary, and the cylinders, crank case, and all their adherent parts rotate; the working is thus exactly opposite in principle to that of the radial type of aero engine, and the advantage of the rotary lies in the considerable flywheel effect produced by the revolving cylinders, with consequent evenness of torque. ”

“ After the rope leaves the said sheave, it is coiled away at pleasure. g, g, are two change wheels, for varying the speed of the grooved wheel d, d, to answer the various sizes of ropes; h, is a spiral wheel, driven by the screw k, fixed upon the axle l; m, is a band-wheel, which is driven by a belt from the shaft of the engine, or any other communicating power; n, n, is a friction strap and striking clutch. The axle q, is driven by two change wheels p, p; by changing the sizes of those wheels, the different speeds of the drum R, R, for any sizes of ropes, are at once effected. ”

“ Fig. 205 represents Watt’s sun-and-planet motion for converting reciprocating into rotary motion; b d is the working beam of the engine, whose centre of motion is at d. The gear a is so connected to the connecting rod that it cannot rotate, and is kept in gear with the wheel c on the fly-wheel shaft by means of the link shown. The wheel a being prevented from rotation on its axis causes rotary motion to the wheel c, which makes two revolutions for one orbit of a. ”

“ In whatever form energy is produced and distributed to the train it ultimately appears as mechanical energy applied to turn on e or more axles against the resistance to their rotation imposed by the weight on the wheels and the motion of the train.
The rate at which work is done on a particular axle is measured by the product Tω, where T is the torque or turning moment exerted on the axle by the motor or mechanism applied to it for this purpose, and ω is the angular velocity of the axle in radians per second. ”

“ An even torque, or great uniformity of rotation, is transmitted to the air-screw by these engines, while the design also permits of such good balance of the engine itself that vibration is practically eliminated. The angle between the two rows of cylinders is varied according to the number of cylinders, in order to give working impulses at equal angles of rotation and thus provide even torque ”

“ The most common rotating pieces in machines are wheels of various kinds, and in these the centre of gravity is evidently identical with the centre of rotation; but if from any cause a wheel, which is to turn [Pg 64] rapidly, has an extra weight attached to one part, this weight must be counterpoised by one or more on other portions of the wheel, in order to keep the centre of gravity of the whole in its proper place. Thus it is that the driving wheels of a locomotive are always weighted so as to counteract the effect of the crank and restore the centre of gravity to the axis of rotation. ”

“ Thirty-six strands of rubber, weight about 56 grammes, at 150 turns give a torque of 4 oz. on a 5-in. arm, but an end thrust, or end pull, of about 31⁄2 lb. (Ball bearings, or some such device, can be used to obviate this end thrust when desirable.) A series of experiments undertaken by the writer on the torque produced by twisted rubber strands, varying in number, length, etc., and afterwards carefully plotted out in graph form, have led to some very interesting and instructive results. ”

“ When the fly-wheels of steam-engines and dynamo machines and other quick speed machines are rotating on board ship, you may be quite sure that they offer a greater resistance to the pitching or rolling or turning of the ship, or any other motion which tends to turn their axes in direction, than when they are not rotating. ”

“ But in planning such devices it is well to remember that the moment of a couple increases with its arm, so that in a wide aëroplane the wing tips may best furnish the torque; while in a high short-winged machine, vertical planes, fins, or rudders may give the desired longitudinal moment. Obviously such vertical guiding or controlling surfaces may be so placed as to tilt the machine toward the center of curvature of its path, at the same time opposing the centrifugal force, and exerting a torque about the vertical axis tending to steer the flyer along its path. ”

“ These illustrations will suffice to show how a rapidly rotating body may contain energy in virtue of its rotation, just as a cannon-ball contains energy in virtue of its speed of translation, or as a clock-weight has energy in virtue of the fact that it has some distance to fall before it reaches the earth. The rotating body need not necessarily have the shape of a wheel—it may be globular in form; nor need the axes of rotation be fixed in bearings, like those of the fly-wheel; nor of course is there any limit to the dimensions which the rotating body may assume. ”

“ The arrow S in the vector diagram represents the spin-momentum of the axle and drivers at a given instant, S' represents the spin-momentum at a later instant, ΔS represents the increment of spin-momentum, and T represents the torque which must act upon the axle because of its precession. To exert this torque the outer rail must push up with an excessive force against the outer driver, or, in other words, the outer driver must be forced downwards against the outer rail with more force than that which is due to the locomotive alone as it is rounding a curve. ”

“ Conservation of Rotation.—Let us suppose a hollow circular cylindrical vessel filled with fluid to be set in rotation, about its axis: then if the fluid possessed viscosity it would, in course of time, acquire sensibly the same speed of rotation as the vessel, so that the whole system would revolve en bloc. With an ideal fluid, however, the rotation of the vessel might be continued indefinitely without imparting any motion to its contents. ”

“ We all know that the train’s motion is retarded, and this loss of motion represents the requisite expenditure of force. Now, is there any process in nature resembling, in however remote a degree, the application of a brake to check the earth’s rotation? There is. The tidal wave, which sweeps, twice a day, round the earth, travels in a direction contrary to the earth’s motion of rotation. ”

“ The fly-wheel is a sort of reservoir, into which the engine pours its power at each stroke of the piston. The various machines in the mill merely draw off the power from the store accumulated in the fly-wheel. The earth is like a gigantic flywheel detached from the engine, though still connected with the machines in the mill. In that mighty fly-wheel a stupendous quantity of energy is stored up, and a stupendous quantity of energy would be given out before that fly-wheel would come to rest. The earth's rotation is the reservoir whence the tides draw the energy they require for doing work. ”

“ As a method of controlling and changing the rate of rotation of the wheel, the rivers of water had already proven themselves; and as a method of static balancing to compensate for off-center weights, masses of it could be stopped and held in counterbalance tanks around the rim, thus assuring that the observatory, in its stationary position on the hub, would not suddenly take up an oscillatory pattern of motion as the balance within the wheel was shifted either by moving equipment or personnel. ”

“ The more they studied it, the more complex the problem became. “The thrust depends upon the speed and the angle at which the blade strikes the air; the angle at which the blade strikes the air depends upon the speed at which the propeller is turning, the speed the machine is traveling forward, and the speed at which the air is slipping backward; the slip of the air backward depends upon the thrust exerted by the propeller, and the amount of air acted upon.” ”

“ The difference between the rotative velocity of the earth in surface-motion at London and at Liverpool is about twenty-eight miles per hour; and this amount of lateral movement is to be gained or lost, as respects the locomotion in each journey, according to the direction we are travelling in from the one place to the other; and in proportion to the speed will be the pressure against the side of the rails, which, at a high velocity, will give the engine a tendency to climb the right-hand rail in each direction. ”

“ When we reflect on the fact that the rectilinear motion of the piston in the cylinder of the engine had first to be converted into a rotary one, by beams, connecting-rod, crank, &c., and then this rotary movement transformed into a lifting one by the intervention of wheels, shafts, cams, &c., while all that is required in the hammer is a straight up-and-down movement, the wonder is that such an indirect and cumbersome application of power should have for so many years been contentedly used. ”

“ Steam is admitted through a universal joint, descends through the shaft and escapes through a series of small openings placed at a tangent, so as to give rotation to the [93] wheel after the manner of a Barker’s mill. The casing about the rotating wheel is extremely light as relates to the wheel, so that, when the gyroscope is once spun on a vertical axis, the rest of the apparatus may be tilted in any direction, while the gyroscope and its attachments maintain a vertical axis. ”

“ In a large pitch angle so much energy is wasted, not in dynamic thrust, but in transverse upsetting torque. On no propeller out of dozens and dozens that I [77] have tested have I ever found a tip-pitch of more than 35° give a good dynamic thrust; and for length of flight velocity due to dynamic thrust must be given due weight, as well as the duration of running down of the rubber motor. ”

“ In No. 4 the thirty-foot bamboo pole became part of a real keel, no longer hanging above the navigator’s head, but amplified by vertical and horizontal cross-pieces and a system of tightly stretched cords. It sustained motor, petroleum-reservoir, propeller, and navigator in a spider-web frame without a basket. It was a daring innovation. The navigator himself must sit on a simple bicycle-saddle in the midst of the spider-web, where the absence of the traditional balloon-basket seemed to leave him astride a pole in the midst of a confusion of ropes, tubes, and machinery. ”

“ The greater the speed of rotation, the less the pitch for a given aeroplane speed. Then, in order to secure a large pitch and consequently a good gap, the four-bladed propeller is usually geared to rotate at a lower speed than would be the case if directly attached to the engine crank-shaft. ”

“ The most palpable of the advantages of the rotary engine are the reduction in the size of the engine, claimed to result from the great velocity of the piston; the avoidance of great accidental strains, especially noticed in propelling ships; and a great saving of the power which is asserted to be expended in the reciprocating engine in overcoming the inertia while changing the direction of the motions. These advantages adapt the rotary engine, in an especial manner, to the driving of a locomotive or steam fire-engine. ”

“ Screw-like or Helical Motion.—Since any displacement in a plane can be represented in general by a rotation, it follows that the only combination of translation and rotation, in which a complex movement which is not a mere rotation is produced, occurs when there is a translation perpendicular to the plane and parallel to the axis of rotation. ”

“ The simplest form of wave-motor may be suggested by the force exerted by a ferry boat or dinghy tied up to a pier. The pull exerted by the rope is equal to the inertia of the boat as it falls into the trough of each wave successively, and the amount of strain involved in rough weather may be estimated from the thickness of the rope that is generally found necessary for the security of even very small craft indeed. ”