Avionics Bending: Making Cables for the Simulator

Finished Deutsch Connector with Strain Relieve

Since a lot of time the last few weeks has gone into making cables for the instruments and panels of the L-1011 trainer at the museum I thought it would be fun to show you how I make these cables. By the way, there are pretty strict standards on how to makes cables used on actual aircraft and the cables that I make somewhat loosely follow them, however, you should not consider this a guid on how to make cables used on actual aircraft.

Many of the connectors that we use on the simulator came out of actual airplanes. Every now and then you can get a friendly scrapper to cut off the cable ends for you right before the aircraft is scrapped. This is how we ended up with many connectors looking like this:

Tools 

Here are the tools that I use for making cables.

To get the old cables and pins out of the connectors you will need an extraction tool. Extraction tools come in all forms and shapes and are somewhat specific to the connector manufacturer. On circular avionics connectors the most common pin size is RED. The extraction tool below is metal and little more durable, but there are also plastic tools that only cost a few cents and do the job well .... if you are not planning on doing hundreds or pins. By the way, Clay Young from Precession Electronics here in Atlanta showed me a cool trick; when you dip the extraction tool into alcohol prior to using it it will grip to the pin better.

Insertion/Extraction Tool 

Jim just recently found a lot of tools for the museum and they have been a huge help. To put pins back onto the ends of your cables you will need some sort of a crimp tool that can be used with the pins used on circular connectors. Again, there are different crimp tools for different manufacturers. The most common crimp tool is show below and is made by Daniels Corporation and is called the M22520/1-01. The tool that we have at the museum has a turret head on it that can crimp three different sizes (green, red and blue)

Daniels Crimp Tool M22520/1-01 with Turret Head

The pin is inserted on the other side of the turret and then crimped by applying lots and lots of ponds via an easy to operate ratcheting grip.

SETP 1: Pull out the unused pins with the extraction tool.

Keep the pins! They will come in handy when you are making cables. By the way, when these connectors are being built for use on actual aircraft, all pin positions are filled with pins ... regardless of having a cable attached to it or not. These "unused" pins can be re-used in the simulator which then cuts down on the cost. 

STEP 2: Make the cable

Using the Crimp tool, I am now crimping one of the spare pins onto the AWG 22 cable and insert it into the correct location in the connector

STEP 3: Strain and Vibration Relieve of the Cable

If you don't strain relieve the cables on the backside of the connector you risk that, over time, the cable inside of the connector might break off from the pin. This can happen quite easily if you have a lot of strain on the cable, or, if the weight of a cable bundle pulls on a single cable in the connector. Therefore, always build a strain relieve for the cable. 

I use the back-shell clamps that fit the Deutsch and Amphenol connectors to do so. In order for the back-shell not to clamp down on the actual wires, or, as is the case with most connectors, the cable bundle is too small for the clamp to secure the cables I use 3M Temflex Rubber Splicing tape. 

Temflex tape is a thick rubber tape that is not adhesive. It is perfect to wrap around the cables and build a plug with allow the back-shell clamp can clamp down on.

Once in place, the Temflex tape absorbs all strain and vibration that the cables might exert on the pins. 

And this is how I make cables :)

Avionics Bending: Deutsch Connector Recycling

Deutsch DL66R Connector Recycling

Bayonet connectors are pretty darn expensive, especially when they are commercial/military grade. Unfortunately, cockpit projects like the L-1011 project used dozens of them in all different pin configurations and sizes. In order to avoid this cost I was able to buy a box of connectors out of scrap/surplus that had been cut out of an actual L-1011 cockpit. In order to re-use these connectors I need to pull all the sockets and pins out of them. To do so I use a toll made by Astro Tools called the ATR 2080. This tool works for rear release size 20 sockets. Here is how the tool works: 

1. The tool slides down the cable into the rear of the connector.

2. When fully inserted the tool releases the rear retainer clip

 3. Once released the socket together with the crimped on cable simply pulls out of the connector.

There are also hundreds of sockets that had not been used and had been inserted into the connector and then plugged with a small red plug on the backside of the connector. These unused sockets come in handy because they can be re-used, and, at a price of almost $1 per socket .... they come in very handy.

Avionics Bending: NAS 1599 / MIL-C-26482 Connectors

NAS 1599 Connectors used on the L-1011
from. Engineering Description Series, Lockheed, April 1976

Lockheed selected a modified NAS 1599 connector for the L-1011. All of the connectors used on the aircraft are bayonet type connectors. The connectors use standards pins and sockets that can be inserted with a metal or plastic tool and removed with either a metal or plastic tool. The connectors and pin sizes are still in use with aircraft today. The connectors themselves are very very durable, made out of metal and can cover a pretty insane temperature range (-20C to 200C).  The image above is a drawing taken from a Lockheed publication. Below you can see how each of the connector pieces interfaces with the other.

NAS 1599 Connectors used on the L-1011

from. Engineering Description Series, Lockheed, April 1976

Each pin or socket is held in place by a retention collet. The removal tool basically pushes the retention collet open and allows for the pin or socket to be pulled out of the back of the connector.  See image below. This feature makes these very expensive MIL standard connectors reusable.

NAS 1599 Connectors used on the L-1011

from. Engineering Description Series, Lockheed, April 1976

Avionics Bending: Deutsch Connectors (Analysis)

The L0ckheed L-1011 used mostly connectors made by Deutsch. They are round bayonet style connectors that are pretty standard in the aviation industry. They are, however, very expensive when you have to buy them. The best way, is to see if you find them on eBay or somewhere else. Here are a few notes on Deutsch connectors:

1) Each connector has a unique identifier that tells you the size of the connect, the number pins and the key used. For example:

DL66R-14-15SN-1A

It encodes the connector size as 14 the number of pins as 15 and the connector key as "SN". The "S" denotes a socket and a "P" a pin. The connector below has sockets and the instrument picture below that as pins:




1) Each connector has a number of keys that prevent the connector from being inserted into a wrong instrument. There are a large number of different keys, but I will show you the most common key positions here.

"SN" Key ... this one is by far the most common on the L-1011.


"S6" Key Style


"S8" Key Style


The blue arrow show the main key. This one is always on top of the connector at the 12 o'clock position.