Richardson's handbook of projection (1927)

Page scan 00055 from Richardson's handbook of projection

Record Details:

Title:
Richardson's handbook of projection
Date:
1927
Publisher:
New York : Chalmers Publishing Company
Volume:
Richardson's handbook of projection
Leaf #:
00055
Language:
English
Subjects:
Motion Pictures, Motion Picture Technology
Collection:
Books
Format:
Books
Contributor:
Media History Digital Library
Sponsor:
Media History Digital Library
Coordinator:
Media History Digital Library
Description:
Date Added:
August 01, 2024
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MANAGERS AND PROJECTIONISTS 505 exactly the same when measured both ways around the commutator; in other words, distance A should equal distance B, as per upper drawing, Fig. 149. If it be a four-pole machine, with two positive and two negative brushes (four altogether), the correct distance is one-fourth of the circumference of the commutator between the points of adjacent brushes; that is to say, distances marked X should all be equal, as per lower drawing, Fig. 149. If it be a machine with more than two positive and two negative brushes (more than four brushes all told), divide the number of commutator segments by the number of poles or field coils of the machine. The result will equal Figure 149 Figure 150. the distance, in commutator bars, the brushes should be apart. (c) Dirty brushes or dirty commutator may cause sparking, or may even prevent the generator from picking up its load at starting, and will sometimes cause a badly fluctuating arc. Some of the causes of dirty brushes and dirty commutators may be found in one of the following: Carbon brushes contain a small amount of paraffine. When the carbon gets warm, if it be excessive in quantity, it is likely to ooze out and coat the commutator thus forming a partially insulating coating in spots, or the paraffine may mix with dust and coat the end of the brush with a semi-insulat