1921-22.] Gyroscope and “ Vertical” Problem on Aircraft. 315 
the slope of the track the other is descending. The ball which is ascend- 
ing is rubbing against its pusher, and if the power available to rotate the 
erector is not too great the erector will slow down appreciably and the ball 
which is descending the slope will move up against its check. In fig. 37 
is shown an arrangement in which 
two balls are employed as a brake. 
The balls lie, as shown, between a 
pusher p and a check c ; they rotate 
on the track t. If the track t is 
inclined to the horizontal, so that the 
balls are moving uphill, the ball h 
rubs against the pusher p and also 
against the ball h'. If the slope of 
the track is considerable, the ball h 
slides on the track, and the effect is, of course, to slow down the erector. 
When these devices are used, the resting position of the pivoted system is 
definite within half a minute of angle. 
In fig. 38 is illustrated a convenient method of cutting off the action of 
the erector when the vehicle on which the apparatus is mounted is moving 
Fig. 37. 
-a 
Ti 
Fig. 38. 
in a curved path. The ball h rotates on the track t, its motion limited by 
the pusher p and the check c. When the ball is against its pusher it lies 
directly under the core g of the electro-magnet e (fig. 38 (a)). When the 
vehicle moves in a curved path, current passes through the coils of the 
electro-magnet, and the ball leaves the track and adheres to g, as shown 
in fig. 38 (6). An alternative method of bringing about the desired result 
consists in causing the check c to move close up to the ball when the 
vehicle is rounding a curve. 
