While beta testing the new control system, we have noticed that the connectors for the PWM and other outputs on the roboRIO have a tendency to bend due to the large spacing between rows of pins when cables are tied down. Also, the cables can come off with relatively little force, especially if they are older, well used cables. In an attempt to overcome this, we thought a 3D printed part that can help fill the gaps and hold the cables could help with this.
Introducing… the WildStang Cable Magic!
Design goals
We wanted to be able to:
- Fill the gaps between pins to prevent bending
- Help secure cables as soon as they exit the pins to prevent them coming off unexpectedly
A few notes first about how we normally wire things:
We mount everything to ‘perfstock’ – aluminium sheet, punched with a hole pattern. This allows us to zip-tie directly without having to drill holes where needed (because holes are EVERYWHERE!), and it’s really light.
We keep cables tied down close to the component, without exceeding wire bend radius or placing excessive strain on the cable. In doing so, we also make it impossible for connectors to simply come apart, since there is not enough room for the connector to move.
In making the Cable Magic, we wanted to provide a way to assist with securing the cables close to the connector. However, it would still be necessary to secure the cables to something more permanently.
Take 1
Our first version of this design consisted of bars to fill the gaps between the rows of pins, and downward facing hooks (fingers) to help retains the cables close to the connector.
The Cable Magic sits right along the side of the roboRIO.
This held the PWM cables securely, but didn’t facilitate convenient channeling of cables along the side. With only 2-3 PWM cables, it worked well. However, it was unable to handle the cumulative volume of all of the PWM cables.
Take 2
Our second iteration of this design included sideways facing hooks at the top, allowing cables to cables to group up where they need to, and be redirected more easily. While this worked better than the last, it was more difficult to keep the PWM cables aligned properly.
Take 3
Our third iteration of this design now includes rectangular spaces for the PWM cables to keep them perpendicular, while allowing for the free channeling of cables underneath. Teams must still be sure to secure the PWM cables to some structure or mounting board the roboRIO is resting on, but this model should do a good job of making sure any unwanted cable removal does not occur during motion, and that pins don’t get bent due to overzealous zip-tying. 
Production
The first and second iteration were made from printed ABS. With the long fingers of the first version, bending was a bit of an issue. With too much use, or a bit too much force while routing cables, we could anticipate that the fingers may break off.
The third iteration was printed using PLA. So far this seems a better fit, in conjunction with the new design.
Nice side effects
In addition to helping prevent bent pins, it also helps to keep out larger metal shaving that may enter the larger cavities between pins because the space between pins is totally filled, with a cover around the top. It is not a guarantee of no swarf ever entering the precious roboRIO (especially since any unused pins would leave a nice gap), but it can help.
Future versions
We are still iterating over this design, looking at some improvements such as covering the small connector rows (analog and relay – likely a new part), and securing it to the roboRIO itself in an easy manner. Once we are happy with it, we will release the file for teams to print. Right now, version 3 is an early contender, so stay tuned!
Also, if you can think of a better name than the Cable Magic, please let us know. 