MIL-DTL-17060G(SH)
4.6.15 High-impact shock test. Tests for lightweight motors shall be nine blows delivered while the motor is
operating under no-load at nominal speed. An additional nine blows shall be delivered with the motor stationary;
separate motors may be submitted for each series of nine blows if desired by the contractor. Tests specified in
MIL-S-901 under group I and group III in the horizontal and inclined orientation for medium weight motors shall be
conducted with the motor running under no-load at nominal speed. Tests under group II shall be with the motor
stationary. For inclined orientation, medium weight motors shall be mounted with the motor shaft axis inclined and
shaft extension up. Separate motors may be submitted for each series of three blows if desired by the contractor.
Tests shall be as specified in MIL-S-901 and with other features of the test as follows:
Required type of shock test. Type A, B, or C as specified (see 6.2).
a.
b. Weight designation of the shock test (as required by the motor). Motors weighing 250 pounds or less shall
be tested on the lightweight shock testing machine. Motors weighing in excess of 250 pounds and up to 6,000
pounds shall be tested on a medium weight shock testing machine. Motors weighing over 6,000 pounds shall be
tested on a floating shock test platform. When a motor shaft supports a part of a driven auxiliary, such as a pump
impeller or a clutch-type coupling, the motor shall be shock tested with the shaft loaded with the part or with an
equivalent weight for that part.
Required class of equipment. Unless otherwise specified (see 6.2), Class I.
c.
Required grade of equipment. Grade A for Service A motors or Grade B for Service C motors (see 6.2).
d.
e. Method of mounting on shock-testing machine. Mounting adapters shall be as shown on the applicable
figures of MIL-S-901.
4.6.15.1 Post-shock analysis. Following completion of the shock test, the following examinations shall be
performed on the motor in the order given below:
a. Visual inspection (external). Service A and C motors shall be visually inspected without disassembly for
breakage, distortion, deformation, and dislocation of any parts.
b. Heat run. Service A motors shall be operated at full load (at rated speed) with rated input voltage and
frequency applied for not less than 4 hours. Bearing and oil temperature rises shall be determined as specified in
4.6.16. During this test, any unusual motor noises (e.g., squeals, grinding, or pounding) shall be noted.
c. Dielectric strength. For Service A and C motors, a dielectric strength test as specified in 4.6.17 shall be
performed immediately following the heat run. However, the applied voltage shall be 65 percent of the values in
table XV.
d. Internal inspection. Service A motors shall be disassembled and inspected thoroughly for damage (such as
breakage, distortion, deformation, or dislocation of parts). The extent of disassembly shall be sufficient to observe
the condition of all parts including, be not limited to, the structure, bearings, and winding. The causes of any
increase in motor airborne noise shall be determined.
4.6.15.2 Failure to perform principal functions. Any of the following shall be cause for rejection of the motor:
a.
Service A motors:
(1) Breakage of any parts, including mounting bolts.
(2) Appreciable distortion or dislocation of any parts such as mounting feet, poles, coils, and bearings.
(3) Values of speed differing by more than 1 percent of the preshock test values, and no-load input watts
increasing by more than 5 percent. If no-load watts decrease by more than 10 percent, this does not constitute a
failure, but rationale shall be provided explaining this reduction.
(4) A mechanical imbalance of more than two times the applicable value specified in table V.
(5) Either a bearing or oil temperature rise or both in excess of that permitted in table XIV.
(6) Any unusual motor noises (e.g., squeals, grinding or pounding) when operating. The cause of such
noise shall be determined.
(7) Insulation failures during the dielectric strength test of 4.6.15.1(c).
b. Service C motors:
47
For Parts Inquires call Parts Hangar, Inc (727) 493-0744
© Copyright 2015 Integrated Publishing, Inc.
A Service Disabled Veteran Owned Small Business