Differential gear

“ The differential gear makes it possible to apply the same amount of power to each of the road wheels, and also allows one wheel to rotate faster than the other when turning around a corner. If both road wheels were rigidly fastened to a single rotating axle it would be practically impossible to turn a corner for it would be necessary for the engine to slip one or the other of the wheels because of their difference in speed, as the outer wheels turn faster than the inner. ”

“ So far as driving is concerned the automobilist has only to remember with regard to the fixed hind axle that the axle should be kept well oiled, and that careful examination should frequently be given to all nuts and pins.
The Differential Gear.—The live hind axle used in so many of the more recent forms of light car is a very different thing, and needs more attention, as part of its structure is the differential gear. ”

“ Or the driving wheels may be mounted on a live rear axle, the motor driving on to the compensating gear, either by a chain, by spur gearing, or by means of worm gearing, which gives a nice silent drive, and is used in the Oppermann cars. In any case the use of a single motor involves, in addition to the motor, a differential gear. What is to be avoided is a live rear axle with the motor so mounted that any large proportion of its weight comes on this live axle. ”

“ It is called an adder. The scheme of it is shown in Fig. 17: an input shaft [Pg 78] with amount of turning a, another input shaft with amount of turning b, and an output shaft with amount of turning a + b. The adder essentially is another kind of gearbox, called a differential gear assembly. This name is confusing: the word “differential” here has nothing to do with the word “differential” in “differential analyzer.” This mechanism is very closely related to the “differential” in the rear axle of a motor car, which distributes a driving thrust from the motor to the two rear wheels of the car. ”

“ This is what causes the power to drive both wheels at all times, whether going straight or on a turn.
Fig. 34a. Differential Gears.
If, however, one wheel gets on slippery ground, then A, Fig. 29, will move forward, without pulling on the lower end. As the lever A has the same action as the pinion in a differential, shown in Fig. 34a, it will be seen that if the pinion center is moved in the direction of the arrow, and if the wheel W1 slips, the pinion will simply roll on the bevel gear G2 without driving it on the wheel W2. ”

“ The pinions mesh with two wheels that are mounted on a countershaft, on which is also fixed a chain-sprocket, from which the drive is transmitted, through a long chain, to a chain-wheel surrounding the differential gear mounted on the back axle. Traction-engine type of steering gear, with revolving fore-carriage, is most generally adopted, and is rendered sufficiently rapid in its movement by suitable gear, operated by a diagonal shaft and wheel, from the driver’s footplate. ”

“ On many cars the bevel wheels of differential gear were too small in diameter, and hence there was insufficient room to get in pins of sufficient size to carry the pinions h, and rapid wear and breakage took place. In any case it is necessary to have ample diameter for these parts, and to see that they are kept well oiled, not only at the pins and gear teeth but at the centre of the axle, where the two parts are joined by means which allow them to rotate differentially on a centre pin and in the bearings in the differential gear-box which surrounds the wheel j. ”

“ Moore’s patent differential epicycloidal gear. The pinion and wheel are loose on the shaft and eccentric. One wheel has one tooth more than the other.
1546. Multiplying bevil gear. A is a fixed wheel, the cross C is keyed to shaft, B loose on ditto, D and E loose on C; then B is driven at a speed greater than the shaft in proportion to the diameters of the gear. See Patent No. 12,696, 1884.
1547. Double worm gear, right and left hand threads. Neutralises the end thrust on shaft. A and B may be geared together.
1548. Pointed gear; used for light work and for minimum of friction. ”

“ The differential gear is heavy and effective. A patent steering attachment, with spiral roll, holds chains taut and gives positive motion. Friction clutch is mounted on engine shaft and connects with the hub of the pinion on this shaft. Rigid pinion is also provided. Cross-head pump and injector are used, and Pickering governor with improved spring speeder, permitting quick and easy change of speed; also Sawyer’s lever for testing safety. Steam passes direct from dome to cylinder, without loss from cooling or condensing. The steel water tank can be filled by a jet pump operated by steam. ”

“ Instead of India-rubber, elastic steel is used. Since the driving-pulley has the velocity of the tight side, and the driven of the loose side of the belt, the difference in the number of their turns, if they are of equal size, will measure the work. This difference I measure by differential gearing which actuates a hand on a dial. I may turn the handle as fast as I please; the index does not move, for no work is being done. I may hold the wheel and produce a great driving-strain ”

“ As a large gear reduction is thus rendered possible on the back axle, it will readily be understood that the change-speed gear-box may be made considerably smaller than would be necessary for a bevel-driven live axle, where a large gear reduction is not permissible, both on account of its size and because such a gear would be very noisy in its working. ”

“ By means of these it is possible to change the gear of the machine so as to have a high gear under favourable conditions and a low gear when mud, wind, or an ascent make travelling difficult. Although chain gearing is used in nearly every machine made, connecting rods, wheels, or bands are fitted instead to some machines. ”

“ If gears of exactly the proper size cannot be obtained readily, the position of the intermediate gear may be adjusted to produce a proper meshing of the gears.
Mount the small gear on the end of the armature shaft away from the commutator, so that there will be about 1⁄16-in. clearance between the outside surface and the shoulder at the end of the shaft. Fit it on tightly so that no other means of fastening will be necessary. Mount the large gear on the inside surface of one of the truck wheels, as shown in Figs. ”

“ For the benefit of those of our readers, who have no previous acquaintance with mechanism, we shall merely premise that a gear is a wheel with a toothed circumference, like watch-wheels, or what in ruder mechanism are known as cogged-wheels; and those gears, known as level gears, are such as have the toothing on the circumference not perpendicular to the plane of the diameter, but at an acute angle to it, so that when two gears of a peculiar degree of bevil are set in contact, a horizontal rotatory movement may be communicated to one by a corresponding perpendicular rotation of the other. ”

“ Many use the 1/16” square rubber string, others the 1⁄8” while many use ribbon rubber, say 1/32” to 1/16” thick by 3/16”. 1⁄4” and 5/16” wide. For small models, rubber bands can be looped together.
Gears. Small, light weight gears can be made or bought. They are attached to propeller shafts and are geared back different pitches. Some one to two, others one to three, while some gears are one to one. It might seem that one to one is added friction and no gain in winding, but a hook is attached to each gear wheel which allows two rubber motors instead of one, and allows longer unwinding. ”

“ The question of gearing is complicated by the fact that the frame of the car oscillates vertically with respect to the axles. Spur-wheels, worm-gear, friction gear, belts, multiple-band gear, and chain-gear are or have been used. ”

“ The link motion may be moved from full gear forward to full gear backward or to any intermediate position, whether the engine is running or at rest, but is, when the engine is running, harder to move from full gear forward toward back gear, and easier to move from full gear backward toward mid and forward gears, which occurs because of the friction of the eccentrics in the straps, and it follows that this will be the case to a greater extent in proportion as the revolutions of the eccentrics are increased. ”

“ A pinion C on a shaft D is so journaled that during one half of the rotation of the wheel A, it engages with the rim teeth, and during the other half with the hub teeth. As the hub B and gear C are the same diameter, one half turn of the pinion C will give a half turn to the wheel A.
As the rim teeth of the wheel A are three times the diameter of the pinion C, the latter must turn once and a half around to make a half revolution of the wheel A.
Scroll Gearing.—This is a type of gearing [190] whereby at the close of each revolution the speed may be greater or less than at the beginning. ”

“ Half of the power of the engine was to be transmitted to an adjoining building driving a vertical shaft through a pair of miter gears. It was required that these should run noiselessly, which at 350 revolutions per minute seemed a difficult thing to accomplish. I had the gears cut in the best gear cutter I knew of, and fitted them to run in a lathe, the spindle of the driven gear running in a frame made for the purpose, and being provided with a friction wheel and brake. ”

“ The gearing is attached to the axle and countershaft which extend across the engine. The compensating gear is strong and well covered from dirt. The gearing is the gear type, axle turning with the drivers. There is an independent pump; also injector, and all attachments. The band wheel being on the steering wheel or right side of the engine, makes it easy to line up to a threshing machine. ”

“ The imported gear cases are clumsy and heavy, and, being made mostly of metal, are apt to be noisy. The 1898 gear cases of American make are made of a combination of rubber, leather and metal, and are light, noiseless and graceful, and most of the leading makes of the chain cycles for the coming season are built with sufficient clearance to take a gear case. ”

“ As regards the gearing breaking or stripping, that is comparatively inexcusable in an electromobile, as the kind of effort which an electric motor exercises is a steady and continuous one, and the gearing is subjected to none of the jerks and jars which occur when an explosion engine is the motive power, and when change-speed gear is varied by an inexperienced hand. ”

“ Some machinists, when cutting a double thread, simply remove the work from the lathe and turn it one-half a revolution by placing the tail of the driving dog in the opposite slot of the faceplate. This is a very simple method, but if the slots are not directly opposite or 180 degrees apart, the last thread will not be central with the first. Another and better method is to disengage the idler gear from the gear on the stud, turn the spindle and work one-half, or one-third, of a revolution, as the case might be, and then connect the gears. ”

“ The driving power being transmitted from front sprocket or gear by shaft tube to rear gear or sprocket, all being suitably secured as above stated to frame upon rear fork rotatably supported by ball bearings connected to the frame and forks.
“This does precisely what has always been accounted to be out of the question and confutes both theoretical and practical mechanics. It is a gear that turns the corner by means of square cut teeth that mesh directly instead of by means of bevel teeth, and we call it a face gear. ”

“ The power is transmitted from one of the pulleys by a rubber belt to an intermediate shaft, which carries a toothed wheel that transmits the power to the axle by means of an endless chain. On this axle are three conical gear wheels, two of which are furnished with hooked teeth, and the third with wooden projections and fixed permanently in place. ”

“ If two gears running together, or in mesh, have the same number of teeth, they will make the same number of revolutions, but if one has twice as many teeth as the other, the smaller will revolve twice while the larger revolves once. As the cam shaft must revolve but once while the crank shaft revolves twice, its gear must have twice the number of teeth as the gear on the crank shaft. ”

“ Low and reverse are always opposite each other on the same core. High and intermediate are located on another core, and are controlled by another individual [201] shifting fork. The gear box arrangement (Fig. A) shows the cast gear box which contains the gears, shafts, and bearings, and a roomy compartment below the gears in which grease is carried, as the gears in this type of transmission always operate in an oil bath which prevents excessive wear and causes them to operate noiselessly. ”

“ The above cut represents a very cheap and simple gear-cutter. Its principal novelty consists in the use of the large gear-wheel instead of the common graduated table. It is extremely simple, and at the same time possesses all the advantages of the old machine. It will be observed that the crank is connected to the large wheel by a set of intermediate gears, every revolution of which is made to correspond with the number of teeth in the wheel to be cut. ”

“ The use of gears is obvious; they eliminate torque on the spars, or the tendency which a single skein would have to twist the spar. Pieces of tube are passed over the shafts to bear between the gears and the gear bearing. In order to counteract the tendency of the rubber hooks to pull out straight when the rubber is in tension, the hook ends are secured as shown at A. When it becomes necessary to detach the skeins, it is only necessary to slide the tubes along the shaft to open the hook. ”