Hello, I’ve been looking for something like in the KOP where we got twisted green and yellow cable. I’ve found individual wires, but I have yet to find cable that is already twisted, the right size, and the right color all in one.
I know that we could twist it ourselves or use the wrong colors, but I’m curious to see if anyone’s found a simple way to order this already “assembled”.
Cat 3 pairs are the right gauge and have the right number of twists. Someone donated the school spools of the stuff a while back, and we grabbed a few feet. It’s cheap, as it’s going out of style. If you use the Talon SRXs, you may not need to use any wires other than the ones embedded in the motor controllers; just put the Talons electrically between the devices with the clips.
Would it stay like that if there wasn’t something holding it twisted? IIRC wire comes untwisted pretty easily. And if the only thing holding it twisted is the electronics then I imagine the twisting would pull the wires out easier than otherwise (especially with the CAN Weidmeuler connectors that come out so easily).
Also that sounds like it could be very unsafe if not done with the utmost care.
We’ve done this in the past, and it works very well. Sure, when you release the tension it loosens up a bit, but once you get past that it stays twisted without anything else holding it. It’s just like bending a piece of sheet metal - you bend it, it relaxes a little bit, then holds that new shape forever. Trust me - we have wires sitting in boxes that are still twisted together and probably haven’t been attached to anything for years. The kids seem to think that any wire with a 5 cent connector on it should be saved, because we “might need it later”.
If you twist your own wires (or make your own rope), you’ll want to keep the angle of attack of the strands with the place that is being twisted essentially constant as you twist. You should also proceed at a steady speed, with steady tension. This helps ensure that the wire is twisted evenly along its length. The tighter you want the twist, the wider the angle would be. The angle shown below is too steep for CAN wires, but it shows the idea.
Stranded cat3 would be fine; be careful about using solid cat3 wire, as the wire can develop stress fractures due to vibration. Wiring in airplanes and automobiles is almost exclusively stranded wire for this reason.
When twisting your own wire, a simple technique works very well. One student holding the drill, two students holding the opposite end of the wire and one student following the twist with their fingers. The students at the far end of the wires, should allow the wire ends to spin naturally in their hand. The student walking the twist should lightly clamp the twist in their fingers. This will set the wire as you twist. #22 wire works very well for this. You are trying for about 1-2 twists per inch. As a final step, chuck one end of the pair in a bench vise, and then stretch the wire out and give it a good pull. That will stretch the wire a little and set the twist. Taking this last step will prevent the wire from self twisting and kinking up as well preventing it from untwisting. We generally will twist about 30’ at a time.