# How to calculate the required length of an axial pump piston

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? Ive found many for the required diameter but not the length.

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

jrmichler
Mentor
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
Homework Helper
Gold Member
Do you mean length or stroke?

Do you mean length or stroke?
No i meant length

CWatters
Homework Helper
Gold Member
Then I agree with post #3.

jrmichler
jrmichler
Mentor
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