Piston length-diameter ratio

[XYZman]

Could you help in finding an analytical answer or formulas for a proper length-diameter ratio of a piston to prevent it from binding as a function of force or pressure, and piston diameter, and the clearance between the piston and cylinder bore? The piston can either be connected to a rod or to nothing. Thanks very much in advance.

 

[dicer]

As in a nonguided reciprocating engine piston? Or something similar to a hydraulic cylinder piston? Two very different loadings.

 

[XYZman]

It is something similar to a hydraulic cylinder piston. Sorry for not making my question clear. Please help.