I'm planning to drive a small linear guide (4cm long) with a servo in a setup like this:

enter image description here

I wonder if the ball bearings inside would sustain too much stress due to the vertical forces exerted by the links whilst driving it linearly. AFAIK ball bearings can support reasonable radial load, but I'm aware that these guides are usually driven by lead screws instead. Is it a good idea to drive the guide the way presented above?

  • $\begingroup$ How fast and heavily are you loading it? Do the trig from there, compare it against the rail's specs. Would probably be more efficient to turn your drive 90 degrees and just actuate a lead screw to achieve linear motion. $\endgroup$
    – jko
    Commented Apr 3, 2020 at 12:16
  • $\begingroup$ @jko Quite slow. Around 1cm/s and the load is around 1kg. The spec reads C_dyn = 2550N but there's no indication of what the radial load is though. The angle of the servo is limited to 180 degrees. $\endgroup$
    – John M.
    Commented Apr 3, 2020 at 14:21
  • $\begingroup$ Get a new servo lol. My gut feeling is that slow and that low of a load for a rating over 1 kN should be no problem for a gothic arch raceway. $\endgroup$
    – jko
    Commented Apr 3, 2020 at 14:34

1 Answer 1


If you limit the retracted angle of the arm to $\ a<60^{\circ} $ it should be ok.

That would limit the maximum vertical load at two times the horizontal push.

$ F_y = \ \leq 2F_x$


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