1921 - 22 .] Gyroscope and “Vertical” Problem on Aircraft. 293 
used on an aeroplane, means are provided whereby the erector speed 
becomes very great when the aeroplane is turning, the balls will cease 
to function, and there will be no disturbance of the pivoted system. 
Experimental apparatus for bringing about this result has been constructed 
as shown, diagrammatically, in fig. 21. Mounted in the pivoted system 
are two electric motors and , as shown. When the aeroplane is in 
straight flight the erector e is driven by the motor m -^ , and revolves slowly 
in the direction of spin of the gyroscope g ; when the direction of flight 
is changed the drive is changed automatically from the motor m-^ to , 
and the erector then revolves rapidly in the same direction as before. 
The motors drive a spindle s, which in turn, by means of reduction gearing 
contained within the casing c, drives the erector e. With the arrangement 
of gearing employed, if the spindle s were continuous, the effect of switch- 
ing over from to would be to cause the armature of to revolve 
at a very high speed, and to obviate this defect the spindle is fitted with 
a free-wheel arrangement w. When the gearing is operated by 
ceases to rotate and is left behind. 
Mounted on the erector spindle, as shown, are three slip-rings ’ '^3 ’ 
and on these press three brushes h, the brush-holders of which are attached 
to the pivoted system. Mounted below the erector casing are two annular 
copper segments (fig. 22), and on these press two brushes 
(fig. 21). These two latter brushes are parallel to the line of the pivots p^Pi 
