Page:Popular Science Monthly Volume 90.djvu/540

 Shifting Gears Automatically

It is done by electricity, a mere pres- sure of a button effecting the change

��Interior mechanism of the car. The current to operate the shifter is taken from the bat- tery of the starting and lighting system

���There are four buttons, one for each speed- change gear. As these are pushed the gears are moved into mesh by magnetic attraction

��ONE of the electric gear-shifters now on the market, the use of which enables the gears to be changed by the mere pressure on a button, is oper- ated on the principle of electro- magnetism in which solenoids are used. The solenoid is similar in many respects to the common horseshoe mag- net except that whereas the energy of the horseshoe mag- net is permanent and does not vary, the solenoid exerts its power only when electric cur- rent is passing through its coil. As shown in the accom- panying sketch, the simple solenoid consists of a spool around which is wound a coil of wire, the ends of which are attached to some current source. A metal rod inserted within the hole of the spool will move to a position where both ends project equal dis-

��tances from

is passed th

This

���__ the left, moymc fear to the left If ( throufh solenoid No. 2, rod and (ear will ir

��A simple solenoid with rod, one of which is provided for each of the change-speed gears

��the ends of the spool if current

rough the coil of wire.

the principle of the electro- magnetic gear shift, one sole- noid being provided for each of the change-speed gears in the transmission. A rod with an arm carrying the gear is inserted in the solenoid. Cur- rent passed through the sole- noid causes the rod and the gear to move back or forth, in or out of mesh with other gears which transmit the pow- er to the driving wheels. In the ordinary gear set with three speeds forward and one reverse, four speeds in all, four solenoids are used. Thesei are arranged in two sets two each as shown at th bottom of the accompanying sketches. Steel shafts carry- ing gears on arms are placed inside of the solenoids, and asj

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