Ans. More power can be transmitted with a given diameter and width of pulley, on account of the increased grip in the grooves. Rope drive can be employed for long or short distances by reason of its lightness and the action of the grooves.
Gear Drive.—This method is used where a positive drive is desired, as for elevator or railway motors. It admits of any degree of speed reduction without attending difficulties as would be encountered with belt drive.
Thus, with the worm type of gear as used on elevator motors a great reduction in velocity can be made without incurring the expense of countershaft as with a belt.
Fig. 453.—Watson vertical motor designed to operate a vertical shaft, either through belt connection, or by direct drive. Hess-Bright ball bearings are used, taking the downward thrust due to the weight of the armature. For mounting on the floor or ceiling, a tripod base (as shown) is furnished, the standard sliding base being used on a side wall. The armature shaft may be extended for pulley or coupling either above or below the motor.
Friction Drive.—This is a very simple mode of transmitting power and has the advantages of simplicity and compactness. In operation, the driving wheel is pressed against the wheel to be driven, transmitting motion to the latter by the frictional grip. The drive is thrown out of gear by slightly moving the machine on its sliding base. In construction, the friction may be increased by making one wheel of the pair of wood, compressed paper, or leather.
Electrical Connections.—Circuits for dynamos and motors should be carefully planned so as to secure the simplest arrangement, and to avoid unnecessary expense and delay, the wiring should be installed in accordance with the requirements of the National Electrical Code.
Fig. 454.—Sling for handling armatures. In raising an armature it should be supported by the shaft to avoid any strain on the armature body or commutator.
Ques. What may be said with respect to exposed and concealed wiring?