pic: Piston-in-Tube Concept

[cbale2000]

We did something like this back in 2011, but only the cylinder was in the tube, not the piston rod. Rather than using bearings we used linear slide rails on the mechanism it was actuating. Worked pretty good, and definitely saved space.

[PAR_WIG1350]

Isn't a pneumatic cylinder on its own already a piston-in-tube device?
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You could shave some weight off if you used a bracket to secure a tube to the nose of the cylinder so that only the piston rod is enclosed. You might need to rethink mounting, but the weight saved would be non-negligible. In addition, it could be argued that such a design would be more faithful to the name.

[Siri]

We did something similar with Delrin tubes and bars for our 2013 climber (underside, CAD shot). No rollers since the Delrin slides. It ended up being a good way to steamline the package for the pyramid skids. Be ready to demonstrate to the inspectors that you haven't modified the cylinders, however. Some RIs will pay close attention to any pneumatics they can't clearly see. (We showed them a spare.)

[cbale2000]

Originally Posted by PAR_WIG1350

Isn't a pneumatic cylinder on its own already a piston-in-tube device?
.
You could shave some weight off if you used a bracket to secure a tube to the nose of the cylinder so that only the piston rod is enclosed. You might need to rethink mounting, but the weight saved would be non-negligible. In addition, it could be argued that such a design would be more faithful to the name.

Generally, in my experience, these kinds of things are more for saving space than weight. Square tube is also much easier to mount things to.

[PAR_WIG1350]

Originally Posted by cbale2000

Generally, in my experience, these kinds of things are more for saving space than weight. Square tube is also much easier to mount things to.

Any weight that can be shaved off is more weight for future improvements. Furthermore, if you wanted to place the mount near the nose of the cylinder anyway, the method I proposed would not present any impediment.