1、8 DECEMBER 1958 SUPERSEDING MIL“172B 15 DECEMBER 1953 MILITARY SPECIFICATION CASES; BASES, MOUNTING; AND MOUNTS, VIBRATION (FOR USE WITH ELECTRONIC EQUIPMENT IN AIRCRAFT) This specification has bem approved the Department of Defenss and ia ?nun- datw for use by th Departments of thc Army, the Navy,
2、and th Air Fome. 1. SCOPE 1.1 Scope. This specification covers cases, mounting bases, and vibration mounts used to enclose and isolate electronic equipment in aircraft from external vibrations. This spe- cification establishes the general require- ments and dimensions thereof, defines the space limi
3、tations in aircraft therefor, and sets forth the performance and dimensional re- qnirements thereof, in order to insure inter- changeability. 1.2 CIassification. Items covered by this specification are standard cases identified by MS part numbers, nonstandard cases, and mounting bases and vibration
4、mounts of the following chsses, as specified (see 3.1 and 6.2) : Class A. Mounting bases - Mounting bases am- forming to the performance, dimen- sional, and two-bone load-carrying requirements of this specification, and identified by MS part numbers. Vlkation mounts-Vibration mounts conforming to th
5、e performance, dimen- sional, and ho-bone load-carrying re- quirements of this specification, and identified by MS part numbers, Chss B. Mounting bases - Mounting bases con- forming to the performance and dimen- sional requirements of this specification. Load-carrying capability can be two- to-one,
6、or =t 15 percent with non- geometric center of gravity. Unless otherwise specified (see 6.2), the mounting bases are identified by in- dividual - nomencIature in accordance with the Joint Communication- Electronic Nomenclature System (AN) (see 6.8). Vibration mounts - Vibration mounts conforming to
7、the performance, dimen- sional, and f 15 percent load-carrying requirements of this specification, and identified by MS part numbem. ms c. Mounting. bases - Mounting bases con- forming to the performance require- ments of this specification. They can have individual electrical connedors and, unless
8、otherwise specified (see 6.2), are identified by individual AN nomemiahre (see 6.8). 1.2.1 Identifleuth Fsc 5975, 5340 Licensed by Information Handling ServicesProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-C-172C 57 7777706 0007440 2 -172C 1.2.
9、1.1 Cases. The MS part number for standard cases shall be as specified (see 3.1). Nonstandard cases shall be identifled as ape- cified (see 6.2). 1.2.1.2 Mounting bmes. The MS part num- ber for class A mounting bases shall be as specified (see 3.1). Unless otherwise specified (see 6.2), the nomencla
10、ture for classees B and C mounting bases will be established in accord- ance with the AN system (see 6.8). 1.2.1.3 Vibration mounts. The MS part num- ber for vibration mounts shall be as specified (see 3.1). 2. APPLICABLE DOCUMENTS 2.1 The following specifications, standards, and publications, of th
11、e issue in effect on date of invitation for bids, form a part of this spe- cification : SPECIFICA!lIONS FEDERAL PPP-B-566 - Boxes, Folding, Paper- PPP-B-575 - Box, Paper - Overlaid PPP-B485 -Boxes ; Wood, Wire- PPP-U91 -Boxes, Fiberboard, PPP-3401 - Boxes, Wood, Cleated- board. Veneer (Straparound T
12、ype), bound. Wood-Cleated. Plywood. and Lock-Corner. PPP-B-621 -BOX=, Wood, Nailed PPP-M36 -Boxes, Fiber. WP-3476 -Boxes, Set-up, Paper- board. “ARY “116 - Fremvation, Methods “229 -Boxes; Paperboard, of. MetalStayed. 2 “4456 - Shock, Variable Dura- MIGW541 .-Chemical Films fox tion, Method and Appa
13、ratus for. Aluminum and Aluminum Alloys. MILW-6860 - Welding ; Aluminum and Magnesium Alloys, Spot and Seam. “A43625 -Anodic Coatings, for Aluminum and Aluminum Alloys. “3-10377 -Box, Wood, Cleated, Veneer, Paper Overlaid. “L10547 -Liners, Case, Water- proof. STANDARDS MILITARY MIL-STD-105 -Sampling
14、 Procedures and Tables for Inspection by Attributes. “STD-129 - Marking for Shipment and Storage. MIL-STD-130 - Identification MSkiTg of U. S. Military Property. MILSTD-202 -Test Methods for Electronic and Electrical Component Parts. (For MS military standards for cases, mounting bases, and vibratio
15、n mounts covered by this speci- fication, see Supplement-1 to this specificatio:.) PUBLICATIONS Am FORCE-NAW AERONAUTICAL Bulletin No. 143 - Specification and Standards ; Use of. (Copies of specifications, standards, and publica- tions required by contractors ir: connection with specific procurement
16、 functions should be obtained from the procuring activity or as directed by the contracting o5cer.) 2.2 Other publications. The following docu- ments form a part of this specification. Unless otherwise indicated, the issue in effect on date of invitation for bids shall apply. CONSOLIDATED CLASSIFICA
17、TION COMMITTEE Consolidated Freight Classification Rules. (Application for copies should be addressed to the Consolidated Claspification Committee, 202 Chicago Union Station, Chicago 6, Ill.) Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-C-L72C
18、 57 - 9799706 0007443 4 W “G172C 3. REQUIREMENTS 3.1 Military standards for individual cases, mounting bases, and vibration mounts. All requirements specified herein appIy to dl cases, mounting bases, and vibration mounts covered by applicable MS military standards. Details or exceptions applicable
19、to individual classes, sizes, and types are specified on the MS military standards listed in Supplement-1 to this specification. In the event of any con- flict between this specification and the in- dividual BIS military standards, the latter ehall govern (see 6.2). 3.2 Qnali5cation (applicable only
20、 to class A mounting bases and classes A and B vibra- tion mounts). Class A mounting bases and classes A and B vibration mounts furnished under this specification shall be a product which has passed the qualification inspection epecified in 4.4 (see 6.3 and 6.3.1). 3.3 Definitions. For the purpose o
21、f this specification, the following definitions shall apply : 3.3.1 Cme. A case is an enclosure for a re- movable electronic unit (chassis). 3.3.2 Equipment. An equipment is a case with a removable electronic unit (chassis) installed therein. 3.3.3 Mo2cntix.g base. A mounting base is the base upon w
22、hich the equipment is placed for vibration isolation. It consists of a SUP porting system which provides a mounting structure complete with integral vibration- isolating elements, or with detachable vibra- tion mounts. 3.3.4 Vibration mount. A vibration mount is an individual unitcmounting device us
23、ed in multiples to isolate equipment from vibra- tions. 3.5.4.1 Cup-type. A cuptype v%ration mount is a mount which exerts its support at a single point. 3.3.4.2 Beam-type. A bearn-pe vibration mount is a mount which exerts its support along a line. It is usually equivalent to two cup-type mounts. 3
24、.3.5 Mozcnted unit. A mounted unit con- sists of an equipment (or mockup) mounted on a standard mounting base. 3.3.6 Mockup. A mockup is a dummy or simulated equipment which has the same weight, center of gravity, and geometry as an actual or possible equipment. 3.4 Material. Unless otherwise specif
25、ied herein, material will be specified in the ap- plicable equipment spidication. Specifications and standards for all materials and parts, and Government certification and approval of processes and equipment which are not spe- cifically designated herein and which are necessary for the execution of
26、 this specifica- tion, shall be selected in accordance with Pub- lication 143. Acceptance or approval of any constituent material or part shall not be con- strued as a guaranty of the acceptance of the finished product. In the event of any conflict between this specification and the equipment specif
27、ication, the latter shall govern. 3.4.1 Protective treatment. Material used in the construction of cases, mounting bases, and vibration mounts shall be resistant to, or pro- tectsd against, environmental and climatic conditions, corrosion resulting from salt air, high humidity, and moisture, in a ma
28、nner that will 8seure compliance with the performance requirements of this specification. The use of any protective coating that will crack, chip, or scale with age or extremes of almospheric conditions is prohibited. The protective coab hg applied to the interior of the case Shan be compatible with
29、 the cooling techniques utilized. i- . o Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-3.4.1.1 Protective Coating for duminum. Aluminum structural parta which do not need to be grounded or bonded shall be anodized in accordance with Specification M
30、IGA-8625 or shall receive an approved chemical film in accordance with Specification MIL-G-5541. A 2- to 5-minute immersion in a solution con- taining 5 to 10 percent chromic acid in water, and maintained at 49“ to 60 C, my be used in lieu o anodizing; or a chemical film in accordance with Specifica
31、tion MIGC-5541 may be used on parts fabricated from alum- inum 1100, aluminum alloys 3003, 5052, 6053, 6061, 6063, 7072, or equally corrosion-resist- ant alloys. For aluminum structural parts which need to be electrically bonded or ground- ed, aluminum 1100, alloys 3003, 6052, 6053, 6061, 6063, 70?2
32、, or equally corrosion-resisl ant alloys, shall be used and shall not be an i.e., zinc means zinc castings as well as zinc electroplate, zinc hot-dip, or zinc metal- spray. Different metals in contact, even though similar, shall be employed in assemblies in such a manner that the muller part is cath
33、- odic (or protected) and the larger part is anodic (or cor.ded) if any corrosion takes place. Care shall be exercised in using differ- ent aluminum alloys against eseh other or aNCH MAX7 r(SEE FIG, I) / ” -1 i l l - I l l l l l i l l e l l l MOUNTING BASE SPACE- FOR V I BRAT I ON MOUNTS OR V I BRAT
34、 I ON- ISOLATING ELEMENTS VIEW ACROSS THE NARROW AX IS i MOUNTING ,/BASE I SPACE FOR VIBRATION MOUNTS OR V IBRAT ION-ISOLAT ING ELEMENTS VIEW ACROSS THE LONG AX1 S J FIGURE 2. Swag space for muunting bases. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS
35、-,-,- the tMIllsmissibility in each direction shall be not more than that shown on figure 3. 3.6.6.5 At high frequmcim. When the mounted unit is tested as specified in 4.6.4.2.6, the transmissibility in each direction shall be not more than that shown on figure 3. 3.6.7 Shock (see 4.6.5). 3.6.7.1 St
36、ep 1. When the mounted unit is tested as specified in 4.6.6.1, there Ml be no mechanical failure of the mounting base, vibration mounts, or any of the holding de- vices. 3.6.7.2 Step 2. When the mounted unit is tested as specified in 4.6.5.2, the isolation efficiency at room temperature shall be as
37、spe- cified in 3.6.6.4. 3.6.7.3 Step -S. When the mounted unit is tested as specified in 4.6.5.3, there shall be no separation of the unit from the supporting structure due to failure of the resilient medi- um, or due to weakness in design or con- struction of the mounting base or vibration mounts,
38、nor shall the we come free of the mounting base. Bending or distortion of the mounting base or vibration mount is per- mitted. 3.7 Identification marking. Cases, mount- ing bases, and vibration mounts shall be mark- ed in accordance with Standard MIL-STD- 130 and as specified in 3.7.1 to 3.7.3, incl
39、usive, as applicable. The marking shall be formed in the metal of the item or formed on an attached metal nameplate. 3.7.1 Cases. The MS part number shall be marked on the top of standard cases, centered approximately 1 inch from the front. For nonstandard cases, the marking shall be m specified (se
40、e 6.2). 3.7.2 Mounting bases. The MS part number and load range for class A mounting basa shall be marked as specified (see 3.1). For MIL.C-172C classes B and C mounting bases, the assigned AN nomenclature (see 6.8) shall be marked as specified (see 6.2). 3.7.3 Vbmtion mounts. The MS part num- ber,
41、and load range or specific load as applic- able, shall be marked as specified (see 3.1). 3.8 Workmanship. Cases, mounting bases, and vibration mounts shall be manufactured and processed in a careful and workmanlike manner, in accordance with good design and sound practice. Where welding is required.
42、 it shall be done in accordance with Specification MIL-W-6860. 4. QUALITY ASSURANCE PROVISIONS 4.1 Classification of inspection. The exami- nation and testing of cases, mounting bases, and vibration mounts shall be classified as follows : (a) For cases: 1. Acceptance inspection (see 4.5.1). (b) For
43、mounting bases and vibration mounts : 1. Qualification inspection. (see 4.4). 2. Acceptance inspection. (see 4.5.2). 4.2 Inspection conditions. Unless otherwise specified herein, all inspection shall be made at room ambient temperature, pressure, and humidity. In case of dispute, the referee con- di
44、tion shall be 23“ and salt spray (corrosion) (see 4.6.3.3) and construction for which inspection may be made as part of the applicable portion of the equipment specification. The inspection shall be considered minimum and does not preclude additional inspection when such in- spection is inclnded in
45、the applicable equip- ment specification of which this specification forms a part. 4.5.2 Mounting bases and vibration mounts. Acceptance inspection for mounting bases and vibration mounts shall consist of groups A and B. 4.5.2.1 Inspection lot. An inspection lot shsll be as specified in Standard MIL
46、STD- 105. 4.5.2%2 Resubmitted lots. If an inspection lot is rejected, the manufacturer may rework the lot or screen out defectives and resubmit it for acceptance inspection. Resubmitted lots shall be kept separate from new lots. The re- submitted lot shall be inspected, using tighten- ed inspection.
47、 11 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-” MIL-C-LiZC 59 9999906 0007450 5 MIGG172C 4.5.2.3 Group A inspection. Group A in- spection shall consist of visual and dimen- sional examination (see 4.6.2). Statistical sampling and inspection sha
48、ll be in accordance with Standard MIL-STD-105, The acceptable quality levels (AQL) shall be 1.0 and 4.0 (percent defective) for major and minor de- fects, respectively. Major and minor defects shall be as defined in Standard MIGSTD-105. 4.5.2.4 Grmp B inspection. Group B in- spection shall be the lo
49、aded-height test (see 4.6.3.1). 4.5.2.4.1 Sampling procedure. The sampling procedure shall be in accordance with the ap- pendix to Standard MIGSTD-105. Unless otherwise specified herein, normal inspection shall be used at the start of the contract. The reduced inspection procedure shall .be R-1. The AQL shall be 6.5 (percent defective) and the inspection level shall be L7 for normal in- spection and L5 for reduced inspection. 4.5.2.4.2 Disposition of sample units. Sam- .
