pic: Piston-in-Tube Concept

[EricH]

Rather than using bearings, what's keeping you from using a short section of tube of the next size up, and possibly applying a thin sheet of delrin or HDPE as a bearing surface?

Some clever material selection here could eliminate the bearings entirely, while still providing the same effect.


I'd be a little leery of only using two bearing sets if straightness was critical (it often is), and would suggest 3-4 sets (2 on one side, 1-2 on the other) in such applications. Or, as noted, some clever material selection.