I'm designing a custom part that needs an active shock absorber and space is restricted. I most likely won't be able to use a stock absorber and was thinking, can two squarish tubes be made tight enough?

  • $\begingroup$ Anything can be made accurately enough with enough money. It's much easier to make round precision parts, though, particularly bores. Instead of asking us, ask your machine shop. $\endgroup$
    – TimWescott
    Aug 19, 2019 at 1:31
  • $\begingroup$ Would a square ram be more likely to jam through a rotating load? $\endgroup$
    – Solar Mike
    Aug 19, 2019 at 5:15
  • $\begingroup$ @TimWescott I don't have a machine shop. $\endgroup$
    – akauppi
    Aug 20, 2019 at 16:21

1 Answer 1


Assuming reasonable pressures, it should be workable.

However, keep in mind that the pressures will be higher at the corners and you'll run a higher risk of leakage / bursting. Cylindrical tubes distribute the pressure evenly across the bearing surface and don't have that issue.

You'll also potentially have difficulty with fabricating a gasket to seal the space between the square tubes.

Given the minimal difference in surface area between a cylindrical and square tube, and the ready prevalence of cylindrical tubes, it does beg the question as to why you feel a square tube is the more appropriate design choice.

  • $\begingroup$ The thinking of square tube came from space constraints (I may end up making a custom integrated part instead of stock tubes) and from the wish it would prevent axial rotation. However, thinking about this more I think the mere shape is not enough to remove rotation, since the two sides of the cylinder won't actually meet due to tightenings). I'll look at stock cylinders and/or make mine round. $\endgroup$
    – akauppi
    Aug 19, 2019 at 6:34
  • $\begingroup$ @ GlenH7: I’m very curious why you are mentioning that the pressure will be higher in the corners. I thought that in a hydraulic chamber the pressure is in every point the same. I rather think you mean the tension in the material of the piston could be higher. Perhaps you can clarify. Thanks. $\endgroup$
    – tueftla
    Aug 20, 2019 at 8:58

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