Page images
PDF
EPUB

is commonly called a double reduction gear for single motor equipment. The outline 4 represents the motor, B being the shaft. Upon this shaft is mounted a small pinion which meshes into a larger wheel on the intermediate shaft C. This shaft carries a pinion which meshes into the wheel D mounted upon the arle of the vehicle.

Fig. 3 illustrates a single reduction double motor equipment, the motors being located at AA. In this arrangement the pinion on the end of the motor shaft meshes directly into a large gear secured to the carriage wheel, thus dispensing with the intermediate shaft (' of the previous figure. The single reduction gear is the more simple in construction, but the motors run at a lower velocity, and on that account must be larger for the same capacity. With the double motor construction each wheel is driven independently and the axle C, in Fig. 3, remains stationary, as in any ordinary vehicle; but in a single motor equipment, arranged as in Fig. 2, the wheels are fastened to the axle and the latter rotates. When a carriage runs round a short curve the outer wheels will revolve faster than the inner ones, if free to move independently, as in Fig. 3. If they are rigidly attached to the axle, as in Fig. 2, one or the other will have to slide over the ground, and this is decidedly objectionable with rubber tires. To prevent this slipping of the wheels in rounding curves, the axles, in designs following the construction of Fig. 2, are made in two parts, and the gear D is arranged so as to drive the two halves, imparting to each one the proper velocity. Gear wheels of this kind are called compensating gears; they are made in many designs, but the most common form is that illustrated in Fig. 4. In this drawing A is the gear D of Fig. 2, and BB are bevel gears which are mounted upon studs C, which are virtually the spokes of wheel AA. Large bevel gears E and F are placed on either side of a E, being secured to (i, which is one-half of the axle, and F and H, which is the other half. If the carriage is running in a xtraight line, the two parts of the axle G and I will revolve at the same velocity and the gears BB will not revolve around the studs C, but in rounding a curve one of the halves of the axle will revolve faster than the other and then the gears B will rotate round the studs 0. The compensating gear is not a feature peculiar to electric vehicles; it is used on all kinds of automobiles when the construction is such as to require it.

[ocr errors]

FIGURE 4.-Compensating gears. FIGURE 5.-Single motor equipments. If a compensating gear is placed upon the axle the latter, instead of supporting its end of the vehicle, will itself have to be supported, for as it is cut in two at the center, it has no supporting strength. By placing the compensating gear on another shaft this difficulty can be overcome. Fig. 5 shows the construction used by the Columbia Company in its single motor equipment. In this arrangement the motor casing is made of sufficient length to reach from one side of the vehicle to the other. The armature and field magnets of the motor, which are the parts that develop the power, are located at A and the compensating gear is placed at B. The motor armature is mounted upon a hollow shaft, which is connected with the compensating gear. The shafts D and C, upon which are mounted the pinions E and F, are turned by the side wheels of the compensating gear, and therefore will run at such velocities as the motion of the carriage wheels may require.

While this construction renders the carriage as easy to steer as those in which the motors are connected with the rear axle, it sacrifices the advantage derived from applying the power to the front wheels, namely, the ability to turn round in a small space.

Another design for driving the front wheels which allows them to swing round independent pivots, is shown in Fig. 14, which is a coupé made by Krieger in France. The power is supplied by two motors, one being mounted on each swivel point. The construction can be understood by considering that in the lower part of Fig. 13 the motor would be secured to a suitable support at the end of the frame L, being held in such a position that the shaft would replace pivot D and a pinion mounted thereon would gear into wheel E. What the advantage of this construction may be, the writer is not able to point out; it certainly shows, however, that there are many ways in which the object sought may be accomplished.

American manufacturers of electric vehicles, at least the great majority of them, resort to spur-gearing to transmit the motion of the motor to the driving wheels, but with the French designers the chain and sprocket appears to be in great favor. Fig. 15 shows a Jenatzy vehicle (French), in which the chain is used. This construction would not be received with favor by Americans, who as a rule desire to have the mechanical part of the apparatus hidden from view as much as possible. In the Jenatzy vehicle two chain gears are used, one on each side of the body, and from the engineering point of view this is the most desirable arrangement, as with it the driving wheels are independently operated and a compensating gear need not be placed upon the axle. The American designer, however, would in most cases be controlled more by the artistic appearance and would use a single chain which would be placed under the body of the carriage, and thus as much out of sight as possible.

[graphic][ocr errors][merged small]
[graphic]

FIGURE 15.—Jenatzy Dog-Phaeton. Fig. 16 shows an English design of electric dog cart. The mechanism consists of a single motor which is connected with the axle by means of spur gearing, this being so arranged that several different speeds can be obtained for the vehicle with the same velocity for the motor. To obtain variable speeds by means of gearing it is necessary to introduce a considerable amount of complication, and in this country the opinion of most designers appears to be that the gain effected thereby is not sufficient to compensate for the increased complication, and differential speed gearing is not often used.

[graphic][subsumed]

FIGURE 16.—The Electric Motive Power Co.'s Dog Cart.

evident from this fact that if the front axle of an automobile were the same as that of a horse vehicle, the driver would have an unpleasant task, to say the least, in holding the steering lever in position, and should one of the wheels drop into a rut, the handle would be jerked violently out of his hand and the vehicle would sheer off to one side, possibly with serious results. To avoid this difficulty the front wheels of horseless carriages are arranged so as to swing round on a center close to the hub, if not actually within it. The most common construction is illustrated in Fig. 10, the first being a view of the axle and wheels as seen from the front, and the second a view from above. On the left-hand side of Fig. 10, is the axle proper, and BB are the portions upon which the wheels are placed. The central part A is held rigidly to the body of the vehicle or to the truck which carries it, and the ends BB are swung round the studs PP in a manner moru clearly indicated on the right-hand side. Here the levers CC are shown, and these extend from the side of BB. The right-angle lever E is connected with the steering lever G by means of rod F, hence, when G is moved, rod D moves, and thus levers CC are rotated round the studs PP, and in that way the supporting studs BB which carry the wheels are turned. As the studs PP are not exactly in line with the plane passing through the center of the rim of the wheel, there is a slight tendency to jerk the steering handle round when a wheel drops into a hole in the pavement, but the leverage of B being very short, this tendency is so small as to be hardly noticeable.

Fig. 10 illustrates the general principle upon which the front axle is designed, but the construction of the swivel joints P is far more elaborate, as can be seen from Fig. 11, which illustrates the actual design employed in the vehicles just described. Looking at Fig. 9, it will be noticed that the front axle consists of two bars, one of which runs in a straight line from side to side, while the other is curved with the convex side upward. In Fig. 11 B is the end of the upper curved rod and (' is the lower straight one. These two rods are secured into the Casting A, which holds the part D upon which the wheel is carried, D being the part B at the left side of Fig. 10. The end E which is broken off in the drawing extends through the hub of the wheel and is provided with ball bearings so as to run without friction. The upper end F, of D, is arranged so as to be held by a ball bearing, as shown, against the end of J. By means of an adjusting screw I at the lower end the parts are brought into proper position with reference to each other. The shaded portion II is the lever (at the right side of Fig. 10.

The left-hand end of Fig. 12 shows a design for front axle wheels which is one of the many modifications of the general arrangement just described. In this construction the wheel swings round the stud C, which is placed within the hub, and in a line, or nearly so, with the center of the rim. The rod A is the axle and F is the lever extending from the inner part of the wheel hub by means of which the steering is effected. The left-hand side of Fig. 12 is a view as seen from the front and the right-hand side shows the device as seen from above. In this jast drawing it will be observed that as the lever F is attached to the inner portion of the wheel hub, if it is moved to one side or the other of axle A, by pulling or pushing on rod G, the wheel will be swung round. The advantage of designs of this type is that there is no strain whatever brought to bear upon the steering handle, and the objection is that the wheel hub is made much larger and the whole construction is somewhat more complicated.

.1

FIGURE 10.-Arrangement of axles and wheels.

[ocr errors][merged small]

FIGURE 11.-Front axle.

FIGURE 12.-Front axle wheels. The arrangement of the front axle, so as to swing the wheels round a center close to the hub or within it, as described in the foregoing paragraphs, is used on all types of automobiles and is not a distinguishing feature of the electric carriage. In some of the lighter vehicles the front wheels are held in forks of a design substantially the same as that of the front wheel of the ordinary bicycle, the tops of the forks being connected with each other by means of a rod, as in the lower part of Fig. 10, so as to obtain simultaneous movement of the two wheels by the movement of a single steering handle.

In the majority of electric vehicles the power is applied to the rear axle, but some are made with the motors geared to the front axle. In a few of these designs the wheels and axle are made the same as in an ordinary carriage, so as to swing round a pivot or king bolt located at the center of the axle and reinforced by a fifth wheel. When this construction is used the steering gear is made so as to hold the axle in position more firmly than in the other designs; but even with this assistance the driver has a harder task than with the independently swinging wheels. The advantage derived from swinging the whole axle is that the carriage can be turned round in a very small space, and on that account the construction is well adapted to cabs.

Sereral arrangements have been devised by means of which the power can be applied to the front wheels, while these may at the same time swing round independent centers. One of these constructions is illustrated in Fig. 13, the first drawing presenting the appearance when seen from above, the second being a view from the front. In the first diagram the motor is shown at A, and by means of pinion B and gear C, motion is transmitted to the axle, which is shown more clearly in the right-hand figure. On the ends of the axle are bevel gears FF, and these mesh into other bevel gears which revolve round the vertical studs D. Through this train of gearing the bevel wheels E are driven, and these are attached to the hubs of the carriage wheels. From the first diagram of Fig. 13 it can be seen at once that the gears E E can swing round D in either direction without in any way interfering with the transmission of motion from gears FF. The levers HH are secured to the sleeves GG which swing round the studs DD, hence, by connecting these with the rod J and moving the latter to one side or the other by means of the steering handle, the wheels are turned in any direction desired.

N

FIGURE 13.—Constructions showing power applied to front wheels.

« PreviousContinue »