184.108.40.206 Dynamic balance .-
220.127.116.11.1 By instrument.- The dynamic balance of the completely assembled motor (and any
special attachments such as brakes, overspeed switches), shall be measured. Motor shall be tested at
their no-load speed except that in motors having a varying speed, but no definite no-load speed shall be
tested at not less than 100 percent above the rated full-load speed of the driven auxiliary or at the maxi-
m urn normal operating speed of the driven auxiliary whichever is higher. The method of test shall be as
(a) Place the motor on an elastic mounting, so proportioned that the up-and-down natural
frequency shall be at least as low as one-quarter of the operating speed of the motor.
To accomplish this, it is required that the elastic mounting be deflected downwards
at least by the following amounts due to the weight of the motor. The deformation
of the mounting should in no case be more than 1/2 the original height of the elastic
Revolutions per minute
(b) A reliable vibration indicator shall be employed.
(c) The amplitude of vibration shall be measured on the bearing housing in the direction
giving the maximum amplitude, with the motor running, the axis of the shaft in
normal position and at normal voltage. The motor shall be balanced with 1/2 a
standard key in the keyway; that is, a key of full length, flush with the top of the
18.104.22.168.2 By hand, - The blance shall be checked by "touch" without the necessity of mounting on
an elastic base. If motor feels to vibrate excessively it shall be retested in accordance with 22.214.171.124.1
to determine whether or not the dynamic balance is within the acceptable limit.
126.96.36.199 End play. -
4.2, 4. 7.1 Horizontal sleeve-bearing motors shall be tested for "end play" while running by alter-
nately pressing and releasing the rotor shaft at each end. To insure floating of the shaft, there shall be
at least 1/64 inch end play in either direction. The armature shall not oscillate and bump the bearing end.
The longitudinal mechanical and electrical centers shall coincide.
188.8.131.52.2 All ball or roller bearing motors shall be tested for end play. The requirements of
3.6. 1.9.2 and Specification MIL-P-17840 apply.
184.108.40.206 Speed regulation (except series motors). -
(a) With the motor operating at rated load, and with fated voltage (for submarine
service, the test shall be conducted at nominal and the extremities of the
voltage range (see 220.127.116.11 (q) (12) and 3.7.1. 1) applied, the speed in
revolutions per minute shall be observed and recorded. The motor shall
be immediately disconnected from the load as by the throwing off of the
driving belt or unloading a dynamometer, and another set of readings
taken. The difference between the full:load speed and the no-load speed
shall be expressed as a percentage of the full-load speed.
(b) In the case of adjustable-speed motors the test for speed regulation shall be
made at the highest speed rating.