Model Details

Threads

There are three threaded sections on this part. One is for the matching connector, the second is for the Jam Nut, and the third is on the back for an optional backshell or other connector. These regions can just be modeled as smooth cylinders using the major diameter of the thread.

Contacts

The connector series is actually made up of two parts. The first is the shell, which has one of nine different sizes. The second part is the contact insert. There are several different possibilities for contact size, service rating, pin vs. socket contacts, and contact arrangements. In modeling these parts, the contact inserts are ignored. They are simply specified in a note. This reduces the complexity of the part, and the number of part entries necessary to produce the entire family. During discussion about this portion of the connector, it was decided that the best way to handle the insert area and the interior dimensions of the part, which wasn't specified, was to assume a wall thickness at the ends of the connectors, based on the available part. The insert area would be left hollow. Also, this allows a separate family of inserts to be created, and combined in assemblies as necessary.

Keying

Each connector in this family has six different polarization types. These involve slots cut into the interior of the connector shell. These options are also left to descriptions in notes to reduce the complexity of the model and size of the family.

Countersink

An optional countersink may be included on the back of the connector around the threads. This is necessary for connection of certain types of connectors. In order to allow this countersink to be included, one possibility was to include a countersink angle as one of the parameters in the model. An angle of zero would result in no countersink. Upon discussion of this during the C5SC presentation for this part, it was decided that a better approach to this problem would be to specify the necessary mating depth. This is closer to the way that the countersink would actually be specified. The final decision on this portion of the model was to assume a fixed angle for the countersink of 45 degrees, and compute the appropriate dimensions based on this angle and mating depth.

Keying Flat

The connectors have a keying flat on the jam nut thread region, and they use a D-shaped mounting hole. Since the proper mounting hole has to be included in the panel, the flat has to be included on the part, or the connector would not fit in the hole.

Edge Flats

The mounting flange is in the shape of the intersection of a disk and a square plate. Since the model can be used for interference checking, accuracy of outer dimensions is important. Therefore, the flange has to be created as specified.

O-Ring

The flange contains a circular groove to hold an O-Ring (MS9068). [MS9068] There are several possibilities for modeling this O-Ring. The first is to ignore the O-Ring and its channel. The second is to ignore the O-Ring and include the channel. Third is to model both the O-Ring and the channel. The final is to add the material that appears above the flange, and ignore the rest. This decision took little discussion. The first method, just treating the flange as flat, is the best choice in this case. When assembled, the O-Ring is flattened out, and fills the channel, ending up flush with or below the surface of the flange. The only time an O-Ring would actually be seen in an assembly is in an exploded view, and the channel is not necessary for this.

Hex Nut

The hex nut is covered by MIL SPEC MIL-C-38999/28. [38999/28] This specification lists a hex nut with three or six equally spaced holes on the edge. These provide attachment points for lockwires. These holes are not necessary in the model, so the hex nut can simply be modeled as a flat plate, possibly with chamfers on the corners. Since this particular nut can be used on multiple connectors, and since the connector can be used without the nut, it was decided that the nut be modeled separately, and that the appropriate nut part number be included in the table with each connector entry, and that the connector numbers be included in the table for the nut. This also allows the nut and connector to be shown separately in exploded views.

Part Numbers

The full military part numbers include the DOD No. Prefix, Spec Sheet No, class, shell size code, the insert arrangement, the contact style (pins or sockets), and the polarization designator. The master part numbers would be d38999.24, which is the DOD No. prefix and spec sheet number. The class was dropped because there was no differences in the model among the different class connectors, and including the class codes would increase the family size by an order of magnitude. The member names were chosen to be the shell size codes. (A-J). Therefore, the final part names are fpts.d38999.24-family.? where ? is a shell size code. Originally, the parts were named d38999-24. Changing the hyphen to a period helps to keep the family of parts library directory organized as the period between d38999 and 24 indicates that 24 is a subdirectory of d38999. If any other parts from the 38999 series were to be created, they would also go under the d38999 directory. This greatly reduces the number of subdirectories in the main library directory.

Last Modified: Wed Aug 28 14:41:29 EDT 1996