Assembly Video: https://youtu.be/GqohsdSTQrc

Using"2mm Male Female Banana Plug Connector for RC Model ESC Motor Speaker" to convert Foster Connectors to electrical connectors -concentric BNC like.

The printed parts hold these 2mm contacts in place within the connector.

Female pin goes in tube.

Male goes in other cup like holder. You can also superglue into place, as required but mine worked just on friction which i preferred for maintenance.

When fitted this forms a perfect electrical connection, the connectors are good to rotate in the sockets due to the connector type.

Instructions:

prep

Unscrew the cable connector, remove the rubber black disc and the spring and inner plunger. All these can be discarded. Just need rear of connector and front of connector.

The ground wire will be connected to the body of the connector. Strip 1-2cm of bare wire and fold it back over the outside of the corrugated tubing. Screw the end of the tubing into the back of the connector, with the bare wire on the outside so it makes contact with the inside thread at the back of the cable connector. This forms your ground connector with the connector body. For the 2nd connection the 2mm contacts will be used in the middle of the connector.

bulkhead connector

• Print the FosterConnectorTubeContactHolder.stl recommend using a raft.

-Use a sharp knife to cut off the last mm to remove any elephant foot that may have occurred.

• Solder a small wire to the back of the socket 4mm pin collector - as shown in one of the photographs, ensure as little wire is exposed as possible, and solder does not fall outside the diameter of the contact.
• Put the wire through the top of the tube feeding it though until the back of the contact is against the mouth of the plastic tube
• use a light hammer and light taps on the top of the tube to tap it into the plastic sleeve, it can help to rest the sleeve on top of the jaws of a vice open just enough for the wire to fall between the jaws as you tap.
• now place the foster connector bullk head type in the jaws of a vice or similar to steady it, from the front of the connector put the wire though the connector and then tap the plastic sleeve with contact in it, into the connector from the front, until it is flush with the front face of the connector

cable connector

• print FosterConnectorContactHolder.stl
• solder the pin contact to small wire, ensuring no solder falls outside the diameter of the contact
• feed the wire though the flat face of the contact holder.
• use a vice with jaws open a few mm to let the wire go though, place the contact holder on the vice jaws and holding the contact tap it into the contact holder from the top, with a light hammer
• stop tapping when the contact is flush with the back of the contact holder on the inside
• solder the short wire to the in comming wire from the cable, trim both these back to be as short as possible, using silicone wire is good for this as it is very flexiable
• the contact holder is going to go into the back half of the connector, the front screwing over the top of it.
• fold the wire into the back of the connector, as you push the contact holder into the back of the connector. The contact holder should be more or less flush with the end of the screw thread on the connector back.
• screw the front of the connector onto the back of the connector that is holding the contact

Back nut for bulkhead connector https://www.thingiverse.com/thing:4897811