How to calculate the required length of an axial pump piston

[ENGBIO]

Based on other parameters how do you calculate the required length of a piston inside the cylinder block of an axial piston pump?

What are the relevant equations? I've found many for the required diameter but not the length.

 

[anorlunda]

How about the required difference in volume, piston up and piston down?

 

[jrmichler]

The piston length is determined by the maximum angle between the connecting rod and the bore centerline, the peak force on the piston, the location of the wrist pin, and the allowable bearing stress on the side of the piston. There is no single equation that I am aware of. You need to use engineering judgement to determine the rod length ratio and allowable bearing stress, then calculate from there. The calculations are straight from Statics 101.

 

[CWatters]

Do you mean length or stroke?

 

[ENGBIO]

Do you mean length or stroke?

No i meant length

 

[CWatters]

Then I agree with post #3.

 

[jrmichler]

This is not a typical academic problem with a single exact solution. It is an optimization problem with many solutions, none of which are "the best". You can optimize for least overall size, lowest friction, least number of parts, lowest cost, highest reliability, etc, etc. You choose how you weight the various factors using engineering judgement, then do the calculations. It's an iterative process.

 

[Baluncore]

how do you calculate the required length of a piston inside the cylinder block

How many piston rings are there?
What is the diameter of the wrist pin?
What keeps the piston axially aligned with the cylinder?
What are you pumping? The heat of compressed air will expand the piston unless the skirt/sides can cool by radiating heat into the block.
Skirt of piston must be clear of crankshaft so connecting rod and bore must be longer for longer skirted pistons.