Page:Motors and motor-driving (1902).djvu/326

294 accumulator is seriously injured of course assuming that the accumulator has been properly designed for the work that it has to do.

For use in a car, accumulators are usually—or at any rate preferably—mounted, about half a dozen together, in what are termed nesting-boxes that is, wooden cases a little shallower than the cells themselves. Such a bunch of accumulators forms a unit which can be separately handled for removal or insertion in the vehicle. The connections between the cells composing it should be flexible and should be easily removable when required. Some constructors mount the whole of the cells in one nesting-box or tray, so that they can be inserted by mechanical means into a vehicle when charged, and instead of the vehicle being kept waiting for the process of charging, the discharged battery box can be withdrawn and a fresh one inserted.

Let us consider the running gear of a car such as is shown in fig. 12. The two motors are mounted on the rear axle and adapted to drive by means of spur gearing, consisting of a pinion and a rack both enclosed, each of the rear wheels of the vehicle independently. We will suppose that we have a battery of accumulators mounted on the framework above described, consisting, say, of forty cells, arranged in two groups of twenty cells each, one at the front part of the frame, and one at the rear. We have to consider the problem of connecting the batteries with the motors. This would be a simple business if the car were designed to run on the flat at an always uniform speed, and if the surface on which it would be its fate to run could always be satisfactory, such as an asphalted street, for example. It would then suffice to connect the two terminals of one of the batteries to the two brushes of one of the motors and the two terminals of the other battery to the two brushes of the other motor, by means of cables covered with insulating material, switches for making and interrupting the connection being arranged in between. Such a car, however, would only have one speed, and it would take an