THE DESIGN OF DIRECT-CURRENT 
DYNAMOS AND MOTORS 
INTRODUCTION. 
1. Branches of Science Involved in Dynamo De- 
sign.—The following discussion of the design of dyna- 
mos and motors will be confined to the consideration of 
direct-current machines. 
The design of a dynamo and motor relates to three essen- 
tial parts: first, the armature carrying the conductors in 
which the electric energy is generated or absorbed; second, . 
the field magnet that produces the magnetic field or flux 
in which the armature revolves; and third, the various 
mechanical parts and arrangements necessary to carry 
out the electrical and magnetic actions. Thus, three 
great branches of science—electricity, magnetism, and 
mechanics—are involved. 
2. General Method to be Followed.—In taking up the 
design of a dynamo or motor, the mind should not be 
allowed to jump at conclusions or immediately settle upon 
some particular solution of the problem. The question 
should be considered from all points of view before any 
one point isdecided. Oneshouldalso endeavor to be free 
from prejudices and not blindly follow custom. On the 
other hand, it is a mistake to attempt radical or’ sensa- 
tional departures from well-established practice. By al- 
ways striving for simplicity and directness, the latter 
danger is generally avoided. 
Certain quantities entering the calculations are not pre- 
scribed and must be assumed by the designer.: If he 
is experienced, usually the first or second assumption of 
the variable quantities will lead to a satisfactory result. 
