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554 HANDBOOK OF PROJECTION FOR
must have all this information. If you do not supply the full information you must expect delay and probable failure to get much satisfaction from the manufacturer until you do. The most common causes of troubles are (1) Commutator trouble. (2) Brushes. (3) Bearing trouble. (4) Low or variable supply voltage. (5) Wires too small or poor connections or grounds. (6) Noisy operation due to machine out of line or not set level or poor foundation. Motor air gap not equal all the way around motor rotor. Bearings loose in housing or shaft. Shaft sprung or armature out of balance.
COMMUTATOR. — The brush position is correctly set at the factory and must not be changed, except upon advice from
the factory. Possible commutator troubles are many. They are fully dealt with under general instruction No. 7, page 502. Cutting or roughing of the commutator may be caused by (a) Hard brushes having too much tension, (b) Brushes which have dirty faces, possibly with a too-heavy tension. An armature shaft which has no end motion at all. (d) Brushes which stick in their holder, (e) Brushes moved from their original position as determined at the factory, (f) Excessive brush tension, (g) Brushes not properly seated, (h) Excessive sparking at brushes, (i) Overloaded generator, (j) Eccentric commutator, (k) Brushes worn down too much. See General Instruction No. 7, page 502 and study all its various paragraphs.
NOISY, WORN OR HOT BEARINGS,— Sleeve Type Bearings : Lack of oil. Poor oil. Dirty oil. Oil used too long without cleaning bearings out and renewing oil. Oil rings not turning. Bearings out of alignment, which with 4-bearing sets is caused by motor and generator being out of line with each other, usually because the foundation top is not perfectly level. Misalignment of 2-bearing sets is usually due to feet being bolted to a base having uneven top.
Heating of waste-packed bearings indicates (a) Lack of sufficient oil. (b) Oil of poor quality, (c) Waste improperly packed around journal, (d) New waste packing required.
Ball bearings will run smoothly and noiselessly unless (a) There is lack of sufficient grease, (b) Grease used is too heavy, (c) Dirty grease, (d) Grease contains acid (usually sulphuric) which has roughened the surface of the balls or their races, or both. Use recommended grease only, (e) Flat spot on one or more balls, (f) Ball race loose in bracket housing, or on shaft, (g) Bearings improperly installed. Same