Fig. 12. Front Axle Wheels.
[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 C 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 H is the lever C 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 last 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.
Fig. 13. Constructions Showing Power Applied to Front 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.
Several 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 EE 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.
Fig. 14. Krieger Coupé.