What does this mean. I am pretty sure my little line pump only pumps one or the other. Just curious, as I see it talked about quite a bit.

The rod side or piston side refers to where the supply of oil from your hydraulic pump is directed; which side of the hydraulic piston is being "pushed".

The distinction is made typically to 'say' whether they are using the high volume or the high pressure side of the piston. As there is a larger total face area to 'push' against on the head side, but also a larger volume of oil is necessary, the head side is high pressure and lower pumping volume. The "rod side" is the most common for boom pumps. When the oil is directed to the rod side there is less room (area) on the piston head due to the fact that some of the area is being taken up by the cylinder rod its self. That also has the affect of requiring less oil to move the cylinder the same distance because the cylinder rod is now taking up some of the volume on that side of the piston head. This means faster pumping volume.

The opposite cylinder is moved, in both cases by loop oil.

Rod side = high volume and low pressure

Head side = high pressure and a lower volume

Red,

Just picture two of these sitting next to one another ;~)

Rod side and Piston side are shown well

http://science.howstuffworks.com/hydraulic2.htm