My understanding of swash plates led me to believe that the pistons in a swash plate pump rotate around with the driving shaft along with the chambers in which they aspirate (e.g. M&S Hydraulic Youtube video on swash plate plumps). As the axial position of the pistons change, the piston chambers draw and expel fluid.

However, I just watched a training video from "Our Virtual Academy" (which costs money to view unfortunately) where the pistons do not rotate with the shaft; instead, the swash plate rotates causing the pistons to move axially. The angle of the swash plate is varied by forcing pressurized fluid into the control chamber (here is an example).

I can't imagine why one would use this latter form of swash plate pump. What are the reasons for the different approaches? (What is the correct terminology to distinguish the two so I can carry on my own research)

  • $\begingroup$ Instead of youtube, why not check out the manufacturers of those pumps - they usually have good information $\endgroup$ – Solar Mike Jun 10 at 6:04
  • $\begingroup$ There are some differences between pumping and motoring, such as the need to self-start a hydraulic motor, which means you need a bunch of pistons radially arranged. A pump can be built with just one cylinder. Sealing a pressurized and noxious gas is harder than sealing hydraulic oil that just bleeds into a sump and is piped back to a tank. The energy wasted in compression makes this a bad idea in gasses. So go with a fixed cylinder that can be sealed and rotate the swashplate. plate. $\endgroup$ – Phil Sweet Jun 11 at 9:32

There exist three types of axial plunger pumps.

1- Rotating swash plate axiale plunger piston pumps:

Usually for low-power systems, as the temperature rises above 120° C, it can degrade the fluid properties and cause some damages to the sensitive components.

the advantage of the first type is it simplicity and efficiency, driving a light swash plate requires less power than the heavy block of barrel and pistons

2- Fixed swash plate axiale plunger piston pumps:

In this type, the cylinder barrel rotates with the shaft, of course, designing this type needs more consideration and have more complexities than the previous type, but the clearance between the cylinder barrel and the housing block, allows leakage of the fresh fluid so it serves a lubricant of the rotating body and cooling of the system.

3- Bent axis axial plunger piston pump:

The cylinder barrel makes an angle with the rotating shaft, by changing the angle, you can acquire a variable displacement pump.

  • $\begingroup$ Can you tell me which pump is which from my original question? $\endgroup$ – Jordan McBain Jun 10 at 14:00
  • $\begingroup$ And the second of mine? $\endgroup$ – Jordan McBain Jun 10 at 14:02
  • $\begingroup$ @JordanMcBain The first mechanism, you described is number 2 and 3 in my answer, and the second mechanisme according to you is number 1 in my answer. $\endgroup$ – Sam Farjamirad Jun 10 at 14:07
  • $\begingroup$ If your first description has the problems it has, why wouldn't one always use the third system you described? $\endgroup$ – Jordan McBain Jun 10 at 14:08
  • $\begingroup$ Actually, I've never seen any practical pumps of the first type, is it possible to build it, and study it academically. The third and the second mechanisms are more popular anyway. $\endgroup$ – Sam Farjamirad Jun 10 at 14:10

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