Am I doing something wrong? The tension head on my m140 does not "hold" and it just keeps slipping till it drops beyond 180 degrees and touches the table. Weirdly enough, it has happened twice (on separate occasions) and with Victor strings.
Does the string slip through or is the string stretching? I find that with some slippery strings, my klippermate does that too, although the video makes some weird creaking sound of which I'm not sure is string stretching or not....
if it is slipping, clean the tension jaws (I use a toothbrush and a little bit of nail polish remover, courtesy of my wife, that stuff cleans everything), and if that doesn't help, a bit of hockey tape in the jaws helps grip the string better.
Or like hoyas says, a double loop will hold, it just gets a bit tight near the end as you may not have enough string to do it.