1921-22.] Gyroscope and “Vertical” Problem on Aircraft. 309 
runs in a bearing B. Three slip-rings are carried by s, and these 
with three brushes 63 serve to take in electric current to the motor of 
the gyroscope g. 
One end of the gyroscope spindle is extended, and is connected, by 
means of reduction gearing contained in the casing c, to a vertical spindle 
s, and on this is mounted a boss d from which radiate a number of arms 
e, e, terminating in plane vanes v, v. The gearing is so arranged that 
when the gyroscope flywheel is spinning, the spindle s rotates rapidly in the 
opposite direction, and the vanes v are thus carried round in the direction 
opposed to that in which the gyroscope is spinning, and owing to the 
resistance which the air offers to their motion a torque in the opposite 
direction is applied to the pivoted system. Under the action of this 
torque the entire system turns on the bearing B in the direction of spin 
of the gyroscope g. 
The apparatus is mounted so that the centre of gravity of the pivoted 
system lies very slightly to one side of the pivot axes. When the device 
is in action the equilibrium position is one in which the axis of the 
gyroscope is vertical. When the device is inclined to the vertical its 
motion of rotation becomes space-periodic in character, and there is 
applied to the pivoted system an integral erecting couple, in accordance 
with the principles already explained. 
Attached to the spindle s is a rod r terminating in a bead h. The entire 
system is enclosed in a case c, and on this is carried a pair of cross-wires 
w (one only is shown in the figure) bent so that they lie on a surface 
of a sphere. When the device is carried on an aeroplane the relative 
movements of the wires and head serve to indicate inclinations of the 
aeroplane with respect to the horizontal. 
Adjustment of Stabilisers. 
Returning now to the ordinary form of stabiliser, that in which the 
pivoted system does not rotate as a whole, it will be easily seen that the 
instrument must be carefully adjusted before being set up on an aeroplane. 
When the pivoted system is upright, with the balls in contact with their 
pushers, or what corresponds to the pushers, the centre of gravity of the 
entire pivoted system should lie either at the intersection of the pivot 
axes or very slightly below the intersection. The pivoted system is 
made up of parts which do not rotate, and a system of balls which 
move in a circular track. The centroid of the ball system, when the 
balls are in contact with their pushers, lies at the centre of the track ; 
but the assumption should not be made that the centre of the track lies 
