323 
1911-12.] On a Continuous-current Motor-Gyrostat. 
balanced rotor of large moment of inertia ; and magnalium being very light 
material, practically all the mass of the rotating system is concentrated 
in the ring. On one of the magnalium discs is mounted the commutator, 
consisting of phosphor-bronze studs J, each of which is held in position by 
a nut K. The commutator is mounted on a ring of insulating fibre I, 
arranged concentrically with the shaft. A phosphor-bronze body connecting 
each of the studs with its nut is enclosed in an insulating sleeve. 
The space within the armature ring and its supporting discs is occupied 
by the field magnet system P, and brush gear L. Placing the field magnets 
in this way within the armature ring enables the mass of the stationary part 
to be reduced to a minimum ; and, further, the non-rotating mass is situated 
near the axis, the most convenient position. The field magnet is composed 
of malleable cast iron or mild steel, and carries two windings, one on each 
side of the shaft. The field magnet casting is provided with two projections 
0, one on either side of the magnet coils. Each such projection is adapted 
to receive the brush gear L and brushes ; the latter are mounted parallel 
with the shaft. The brushes make contact with the phosphor-bronze studs, 
which project inwards from the magnalium disc supporting the armature 
ring as already described. By means of two screws G the field magnet 
is clamped to the shaft, which is fixed in this type of motor. The shaft 
extends out to an equal distance on both sides of the field magnet casting ; 
one end of it is bored out to allow of the connections from the field magnets 
and brushes being brought to the outside of an internal casting H made 
