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I'm trying to find a thread that has good fatigue resistance and strength for a telescoping lift to be used in a robotics competition. The lift will lift a weight of around 2-3 kg. I do not intend to spool it as I read that thread with good fatigue resistance are usually not good for spooling, although if there is a kind of thread that is also good with spooling then please let me know. I also want the thread to be relatively lightweight, although that is not a big priority.

If it helps, the actuator will most likely be a chain lifting system.

I intend to string the telescoping lift both ways (one way for lifting, the opposite way for lowering).

I have been looking at steel thread wires but I was wondering if there are any alternatives. Thanks!

(The robot will experience collisions quite frequently, but the telescoping lift should be shielded.)

I would also like to know how to secure the wire rope to the different layers (e.g. by tying it with a specific kind of knot, by using a specific type of clamp, etc.)

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For a 3 kg load which is used on a short term event like the robotics competition that is mentioned, I wouldn't worry too much about fatigue.

In any case, you could use a fishing line which are usually made from nylon or Kevlar and they are very lightweight also. It is also very easy to procure some.

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  • $\begingroup$ Thanks! I was worrying about bending fatigue resistance in particular, because the robot will go through many rounds of practice and many rounds of competition. So the rope will be bent around the pulley many times. But yeah, my online research seems to agree with you that nylon would be a reasonable choice. $\endgroup$
    – Mushroom1
    Dec 25, 2021 at 7:06
  • $\begingroup$ Fishing lines give me the impression of not very good bending fatigue resistance though, since it doesn't really bend over a pulley like in my case. But I really don't know. $\endgroup$
    – Mushroom1
    Dec 25, 2021 at 7:15
  • $\begingroup$ Unless the reel diameter is really small the bending stiffness would not be an issue. Also for fatigue you probably need to do than one thousand cycles before you start seeing any noticeable effects $\endgroup$
    – NMech
    Dec 25, 2021 at 7:16
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    $\begingroup$ Thanks @SolarMike I missed the (n't) at the wouldn't. I corrected it now (I wrote the answer on a mobile phone and the autocorrection kicked in). $\endgroup$
    – NMech
    Dec 25, 2021 at 7:46
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    $\begingroup$ @MadelineLeung for a 3 kg weight even a monofilament would perform adequately. THe monofilament will probably perform better than the strands in terms of bending fatigue. However, IMHO you are overthinking it -- the fishing like is inexpensive, easily procurable and robust. Are there any other requirements/specifications that need to be met which worry you about fatigue resistance. $\endgroup$
    – NMech
    Dec 25, 2021 at 7:48

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