Gear (mechanics)

“ 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. ”

“ Self-reversing gear, with one belt, two fast and one loose pulleys. The large spur wheel is driven from the bevil gear, and carries the weighted lever past the vertical position by a stop on the face-plate or disc, when it falls over and reverses the belt fork. ”

“ By gripping the endless rope between grip wheels (see 1208) the small wheel can be thrown into gear to grip the rope by a lever, cam or screw.
c. Differential gear may be driven from a shaft by belts or gearing. See Sections 84 and 3.
d. Screw gear. Ditto.
e. Rack gear. Ditto.
f. Worm and wheel gear. Ditto.
g. Friction gear is usually driven as No. 1211.
1211. Where the barrel shaft has a slight horizontal movement, so that, by the lever, it can be forced into gear with the friction pinion to raise the load, or into the brake block to sustain the load or lower it. ”

“ 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. ”

“ Chain and sprocket act on each other much as the teeth of gears act, and in effect they are a peculiar form of gears, for if you can imagine one of a pair of gear wheels flexible and flattened out like a chain, and thus running, it is evident that this action is really that of gearing. ”

“ 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. ”

“ By multiplying both numerator and denominator by 4, we obtain two available gears having 24 and 40 teeth, respectively. The 24-tooth gear goes on the spindle stud and, the 40-tooth gear on the lead-screw. The number of teeth in the intermediate or “idler” gear b, which connects the stud and lead-screw gears, is not considered as it does not affect the ratios between gears a and c, but is used simply to transmit motion from one gear to the other. ”

“ When the teeth of bevel gears form an angle of 45° they are called miter wheels.
Miter wheels to gear must be of equal sizes.
A crown wheel is a disc that has teeth which are on its side face; that is, teeth on a flat circular surface all parallel to the axis of the wheel.
A rack has teeth on a flat surface or plane all parallel to one another.
A gear cut by machine is called a cut gear. It has teeth with less clearance than cast wheels, which are not so true or perfect, and therefore require more clearance. ”

“ 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. ”

“ When a screw or worm revolves in the teeth of a wheel, the latter is termed a worm wheel or worm gear; see fig. 270. When a pinion acts with a rack having teeth, we speak of rack and pinion. When the teeth are on the inside of the rim, and not on the periphery, the wheel is termed an internal gear; see fig. 272.
Two wheels acting upon one another in the same plane are called spur gear; the teeth are parallel with the axis. When wheels act at an angle, they are called bevel gear. ”

“ A gear is primarily a toothed wheel; gearing is a train of toothed wheels for transmitting motions; there are two chief sorts of toothed gearing, viz., spur gearing and bevel gearing.
A spur wheel has teeth around the edge pointing to the center; commencing at the center, a spur wheel may be said to consist of a hole, square, octagonal or round, for its axle or shaft; a hub; the web, body or arms; a rim, and the teeth; see fig. 263.
A spur wheel has teeth on its circumference which run parallel to its shaft; wheels as shown in fig. ”

“ But by far the most interesting part of the machine is that which is underneath the frame. At one end we see a pair of ordinary-looking wheels and between them the gear for swinging them to right or left for steering purposes, but even they are somewhat unusual, since they will be seen to have flanges or rims round the edge for the purpose of biting into [Pg 279] the earth, so that they may be able to guide the machine the better in soft ground. ”

“ The gear on the armature shaft should be as small, and that on the axle as large, as practicable. The intermediate gear should be of such a size that it will close the space between the small gear on the armature shaft and the large one on the axle. ”

“ Machines are made of a variable number of carriers to suit goods of different character that are required. Provision is made to carry the rubber beam in hanging brackets underneath the machine, which are of sufficient strength and firmness to carry the maximum weight necessary for governing the rubber tension. Above the machine there is a gear-driven take-up shaft, on which are tension rolls to govern the feed of the goods when braiding. ”

“ By a belt on the fly-wheel of the prime mover the power is transmitted to the line shaft, and pulleys suitably placed along the line shaft by means of other belts transmit power, first, to small counter shafts carrying fast and loose pulleys and striking gear for starting or stopping each engine at will, and then to the driving pulleys of the several machines. ”

“ Gears about 5 in. in diameter and beveled will be required. Adjust the first pair of the beveled gears as at F and G. If the wheel shaft is metal, the gear may be set-screwed to the shaft, or keyed to it. If the shaft is hardwood, it will be necessary to arrange for a special connection. The shaft may be wrapped with sheet metal and this metal fastened on with screws. Then the gear may be attached by passing a pin through the set-screw hole and through the shaft. The upright shaft like the wheel shaft is best when of metal. ”

“ On account of the first-named advantage, they are largely employed upon small gears, having their teeth cut true in a gear-cutting machine; while on account of the second advantage, interchangeable wheels, which are merely required to transmit motion, may be put in gear without a fine adjustment of the pitch circle, in which case the wear of the teeth will not prove destructive to the curves of the teeth. ”

“ 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. ”

“ At each side of the spur gear are placed bevel gears, meshing into the bevel pinions, one of which is keyed fast to the shaft or axle, while the other is firmly bolted to small pinion that drives the traction wheel, or to hub of the traction wheel, which also runs loosely on its axle. ”

“ 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. ”

“ At first sight, it might appear that sand and mud might create a disturbance by edging themselves into these small gears, but the makers maintain that a gear case is unnecessary, because the gears practically clean themselves, in consequence of each gear wheel running in direction opposite to that of its neighbor. ”

“ Furthermore, belt connections are lighter and cheaper than gear-wheel or other rigid and positive connections, and hence the wide application of leather belts for the transmission of power, notwithstanding the slight variations of pulley velocity ratio due to the unequal elasticity of the various parts of the leather composing the belt. ”

“ The intermediate gears are securely locked to each end of the tubular gear shaft by a simple locking device, which makes it possible to remove and replace the gears conveniently and without the necessity of any special tools and appliances. The tubular gear shaft rotates on ball bearings specially constructed and designed to receive the thrust of the driving gear, and transmits the power to the rear hub. ”

“ The teeth of the back gear should be accurately cut so that there is no lost motion between the teeth of one wheel, and the spaces of the other, because on account of the work being of large diameter or of hard metal (so as to require the slow speed) , the strain of the cut is nearly always heavy when the back gear is in use, and the strain on the teeth is correspondingly great, causing a certain amount of spring or deflection in the live spindle and back gear spindle. ”

“ 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. ”

“ The sparking gears are driven by means of a gear formed on a sleeve which telescopes over the hub of the starboard drum, and has a bearing thereon, the end of the sleeve terminating in a ring which is fastened to the crank shaft. ”

“ With a three-speed gear the low and high gears should be chosen respectively below and above the single gear which suits the rider, the middle gear being about the same as the rider’s usual single gear.
All the variable speed gears at present made consist of toothed wheel mechanism either at the hub or crank-bracket, and nearly all are based on the same epicyclic train of toothed wheels. At one speed there is no relative motion of the toothed wheels, the whole mechanism revolving as one solid piece ”

“ Proper proportions, low wheels, chain-gearing, treadles, pedals and cranks, cushion and pneumatic tires, drop frames, steel spokes like a spider’s web, ball-bearings for the crank and axle parts, a spring-supported cushioned seat which could be raised or lowered, adjustable handles, and the clearest-brained scientific mechanics to construct all parts from the best materials and with mathematical exactness—all this has been done. ”

“ Revolving worm for operating a belt shifting bar, locking it at the same time.
2506. Worm gear may be thrown out or in by moving the wheel sideways on its shaft.
2507. Bolt and slot device for gearing two wheels together on one shaft, used on lathe headstocks.
2508. Half nut for throwing out of gear, with screw, and fitted with spring to take up the wear of the nut.
2509. Sliding shaft for winch or other gear, to shift the pinion out of gear or change to another speed (as in No. 2293) . ”

“ Great care should be taken to see that both gear and bearings are kept properly lubricated, or worn surfaces will result, with much extra friction to be overcome, and if not quickly attended to other things may happen of a serious character. ”

“ To accurately divide off the pitch circle of a gear-wheel by hand, requires both patience and skilful manipulation, but it is time and trouble that well repays its cost, for in the accuracy of spaces lies the first requisite of a good gear-wheel. ”

“ The driving pulley b, Fig. 3189, for operating the feed mechanism, receives motion by belt connection from the countershaft, and drives the shaft on which are the bevel gears b and d, and from these gears the feed motion and quick return are derived, while from gear e and pulley r the cutter head may be raised and lowered by belt power as occasion may require. Beginning with the feed motion, the gear d drives gears e and f, which are a working fit on the shaft s. ”

“ 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. ”

“ We now have uniformity in height and contour to insure perfect contact between all classes of equipment, and a positively locked knuckle. The design and attachments to car body are prescribed of a strength in excess of the power of locomotives, and in modern friction draft gear the strength reaches 250,000 pounds. ”

“ 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. ”