Tractor beam

“ Now, suppose we consider the threaded rod as being fixed at the far end, and pulling at the projector end with sufficient power to stretch the rod. The frequency happens to be definitely fixed by the primary standard in the control rack. The distance between remains the same by the constants set up in the tripod and puller beams. The wave length-factor, striving to satisfy the demands of the tractor beam, and maintain the correct number of wave lengths as the beam pulls, will cause the wave length to lengthen. But that tends to change the frequency-velocity factors. ”

“ Couple a force beam with a tractor focus-zone generator. The tractor, you know, operates on the field-of-focus principle. A rough sphere at the end of the beam—anything in that field is drawn. The snatcher merely applies the field-of-focus idea to the side-thrust of a force beam. You raise the power several times and anchor it with a superdrive tube coupled so that the thrust is balanced against a spatial thrust instead of the ship. That tears the guts out of anything. ”

“ A two-membered fuselage can be adapted from this design by omitting the bottom member and skid. Such a fuselage would be suitable for a light machine.
It is an essential point with tractor models to fit a chassis; the purpose thus being twofold. First, it protects the propeller, and secondly, it obviates the characteristic tendency of tractor machines to ascend “nose first,” by keeping the weight low (in technical language, providing a low centre of gravity) . Hand-launched tractor machines that are unprovided with a landing gear are seldom successful and notoriously troublesome. ”

“ The 5-ton artillery tractor, Model 1917, is a self-propelled road vehicle of the “Track laying” type; that is, the power is transmitted to the ground through a flexible endless chain which acts as a track and is composed of steel links and shoes cast integral and connected by hardened steelpins. The advantage of this type of tractor as compared with the usual type of wheel tractor or truck, is its ability, due to very low unit ground pressure, to negotiate very soft and uneven surfaces, impassable to the usual type of self-propelled vehicle except under the most extreme difficulties. ”

“ The working part of a tractor is the engine; it is this that furnishes the power that makes the machine go.
The engine gets its power from the burning of a mixture of fuel vapor and air. When this mixture burns, it becomes heated, and, as is usual with hot things, it tries to expand, or to occupy more room.
The mixture is placed in a cylinder, between the closed end and the piston; it is then heated by being burned, and, in struggling to expand, it forces the piston to slide down the cylinder. This movement of the piston makes the crank shaft revolve, which in turn drives the tractor. ”

“ The big traction engine is a very British product, and it is interesting, if not quite satisfactory, to note that the huge siege guns of the German army are stated to be hauled by engines of British origin. For lighter guns, the steam tractor, or small traction engine, can be employed, but very many efforts have been made to dispense with its service in favour of an internal combustion [Pg 96] tractor, less dependent on constant renewal of fuel and water supplies. ”

“ The engine is one of the two-cylinder type, consuming paraffin fuel, and driving the live back axle through a substantial gear-box and a final drive of the externally-toothed type. Such a machine is well below the weight limit for heavy motor-cars. Fig. 37 shows a more powerful oil tractor by Thornycroft. This machine is the same type which was so successful in the tractor trials promoted by the British War Department in March 1909. It is capable of hauling a gross load of seven tons practically anywhere, and even of lifting that load vertically by means of its winding cable. ”

“ When the ratchet is released, the rear axle drives the fluted wheels on it, and they in turn drive the tractor bands, as shown in the side elevation, Fig. 6. The wire-wrapped flywheel conserves the initial power of the rubber-band motor, and makes its action more nearly uniform.
The tank will run upward of 10 ft. on the rubber-motor power, depending on the size and number of the bands used. The gun is fired by a spring hammer, actuated by a rubber band. The trigger device is shown in Fig. 1. The pulley A is belted, with cord, to the front axle. ”

“ A tractor is arranged to pull its load in two different ways, first by the draw bar, as when pulling plows, and secondly by a belt from the engine pulley as in driving a threshing machine or circular saw. In the first case it is necessary to drive the road wheels through the gear train, and in the second case it is necessary to disconnect the road wheels while driving 333the thresher or saw. As the engine cannot be started while under load it is also necessary to disconnect the road wheels to free the engine while turning it over to get the first explosion. ”

“ When the tractor moves straight ahead the differential turns as if it were one solid piece. When there is less resistance to one driving wheel than to the other, the small bevel gears, in addition to [Pg 162] revolving with the frame that carries them, turn on their shafts. This transmits the power of the engine to one wheel more than the other, according to the resistance of the wheels.
Fig. 64.—“I. H. C.” Chain Drive, Showing the Differential
Figure 64 shows one of the large bevel gears of a differential, with the three small gears, the other large bevel gear being removed. ”

“ The power developed by the engine is transmitted by the differential to both rear wheels; when the wheels meet with equal resistance, they turn equally, but when one wheel meets with greater resistance than the other, it slows down, while the other speeds up to correspond.
A tractor with two driving wheels must use a differential in order to make turns easily. Without a differential, the wheels would run always at equal speed, and in making a turn one would be obliged to slip. ”

“ The foundation of an engine is the base, which supports the bearings in which the crank shaft revolves, and to which the cylinders are attached. The cylinders of tractor engines are made of cast-iron, and the cylinder heads, which close the upper ends of the cylinders, are usually in a separate piece, bolted on. ”

“ Perhaps the most interesting feature of the mechanism was that the Ring appeared to have automatic stability, for the angle of the direction in which the tractor was pointed was controlled not only by a pair of gyroscopes which kept the Ring on an even keel, but also by a manometric valve causing it to fly at a fixed height above the earth's surface. Should it start to rise, the diminished pressure of the atmosphere operating on the valve swung the tractor more to one side, and the horizontal acceleration was thus increased at the expense of the vertical. ”

“ The necessary mechanism was, however, too complex to render anything of the sort suitable for extensive military use, and the same trouble probably applies to the Caterpillar type of tractor, in which the wheels are surrounded by a track in the form of a sort of endless chain, which lays itself as the machine moves upon the ground, and distributes the weight over a large area. ”

“ By changing the connections between the engine and the driving wheels, [Pg 152] the engine can be made to run twice as many revolutions to one turn of the driving wheels, which will give double the number of power strokes; the wheels will thus be turned with twice the force. As no change is made in the speed of the engine, the wheels will now turn at half their former speed, and the tractor will run at 11⁄2 miles per hour. It will, however, have twice the ability to overcome obstacles. ”

“ Fifty feet above the ground, supported upon a cylindrical trestle of steel girders, rested the body of the car, constructed of aluminum plates in the form of an anchor ring some seventy-five feet in diameter, while over the circular structure of the Ring itself rose a skeleton tower like a tripod, carrying at its summit a huge metal device shaped like a thimble, the open mouth of which pointed downward through the open centre of the machine. Obviously this must be the tractor or radiant engine. ”

“ Ratchet wheels, M, are fitted between the ends of the center section and the adjoining pieces, the ratchet wheels being nailed to the center section and soldered to the wire axle. Pawls, U, are fitted to the inside of the two end sections, as indicated in Fig. 1 and in Fig. 5. When the rubber motor is wound up on the drum, the tractor bands are gripped until it is desired to start the tank on its trip. Then the power is communicated from the drum, or center section of the axle, to the drive wheels by means of the ratchet wheels, acting on the pawls. ”

“ So powerful is it that it will crash through underbrush with ease and even small trees yield before it. It will run over soft mud, deep sand, and even snow with equal facility. The tread belts on either side of the tractor are separately driven and by making one belt run faster than the other it is possible to steer the machine. In fact it can be made to turn around in its own length by stopping the belt on one side and driving the belt on the other. ”

“ Midway between the well and the engine a post is planted, on which is balanced a working beam about sixteen feet in length: one end of this beam is attached to the crank of the engine, and the other to the implements in the well. The power is applied to raising the bit—the blow is produced by the fall of the same when relieved by the downward motion of the working beam. ”

“ The most improved form of Watt's engine was reached by successive additions to the old atmospheric engine of Newcomen and Cawley. Hence, the working-beam, derived from the pump brake of that engine, always formed a part; and the parallel motion, or some equivalent contrivance was absolutely necessary. In many American engines, and (p. 100) particularly in those used in steam boats, the working beam is no longer used for the purpose of transmitting motion to the machinery. This is effected by applying a bar, called the cross-head, at right angles to the upper ends of the piston-rod. ”

“ Then he ejaculated a sharp order to the mechanics. They flung the blades of the tractor into revolution. The machine, emitting a series of riflelike reports, commenced to run across the field. The tractor became a blur.
The woodland appeared to rush towards him and then suddenly dropped away in a diagonal underneath. His eyes on the dial of the barograph, the [Pg 76] aviator warped the machine round and set the planes to an acute angle of elevation. Confident in the power of his engine he mounted steeply in a spiral. The record on the dial rose with every second—100 feet—200—400. ”

“ In these cases there are two cylinders and pistons, each fixed to a crank formed in one axle united to the two wheels, and these cranks are so arranged that the greatest power is exerted on one when the least is exerted on the other, and for this purpose they are placed so that when one crank is upright the other is horizontal. The stroke of the piston-rod is not always made to act directly on the crank, but has a “beam” interposed working on bearings in its centre, hence the term beam-engine (see cut) . ”

“ Thus a small engine, working at a high speed, is able by means such as this to pull very heavy loads at a slow speed.
It is evident, however, that the reduction necessary in this case cannot be attained even by a worm-gear, for there are other wheels visible which show that ordinary tooth gearing is also employed to reduce the speed even further before it is applied to driving the tractor along. Practically all the other gear which we see in the picture, above the platform, consists of the controlling apparatus. ”

“ If an attempt is made to shift the gears while they are in motion, the result will be that one will grind against the other, and there will be rapid wear and probable breakage. It is because gears cannot be shifted while they are moving that manufacturers instruct users not to attempt to shift on a hill without first blocking the wheels. The reason for this is that the brakes may not hold the tractor, and if the gears are pulled out of mesh, the machine may start to run down hill ”

“ These trials, if not satisfactory in attaining their main object, at least helped to demonstrate that practically nothing is impossible to a soundly constructed motor vehicle, if properly equipped for rough work. Intermittently, experiments have been made at Aldershot with various machines of more or less peculiar construction. Among these may be remembered [Pg 50] the Pedrail tractor, the wheels of which carry a number of articulated feet which, as the machine progresses, plant themselves one after another squarely upon the ground. ”

“ It consists of a steel frame or platform upon which is mounted a four-cylinder petrol engine with a reservoir above to carry the supply of fuel and with a radiator in front to cool the water which keeps the engine from becoming too hot. Towards the back of the vehicle is what is called by engineers a worm-gear, the function of which is to reduce the one thousand revolutions per minute of the engine to somewhere near the slow speed required of the wheels of the tractor. ”

“ The speed of a tractor engine is practically always controlled by a throttle, which is a valve set in the passage of the carburetor. It operates exactly the same as a damper in a stovepipe; when it is closed, it shuts the passage and prevents the flow of mixture to the engine. As it is opened, it permits a greater quantity of mixture to flow, and it follows, of course, that as the charges of mixture become larger, the engine runs with more power. A tractor carburetor usually has two throttles, one being operated by hand and the other by the governor. ”