Barrel/Valve Plate Wear of Axial Piston Pump

[drober]

I am seeing wear at the Barrel/Valve Plate interface of the axial piston pump I am designing. We were using nitrided 15-5 on nitrided 15-5 but we are now looking at a bronze barrel with "Kingsbury Pads" on it running against a thru-hardened valve plate. The pump must see a range of pressure between 0 and 3000 psi and speeds between 0 and 10,000 RPM for an aerospace app.
Any recommendation on Kingsbury pad design or what barrel bronze materials to use? Galling studies?
I don't think dirty fluid is the problem because I attached a Vicker bent-axis pump to to the system and that unit shows no signs of wear.
Also, how does one achieve the amazing flatness and surface finish of a Vickers, or similar, valve plate and barrel?

 

[MikeHalloran]

Wow; 10,000 rpm on a hydraulic pump? That's an amazing requirement. Did Vickers decline to bid on it? Now you know why.

Amazing flatness and surface finish come from lapping; you get most of the finish for free when you go for flatness. You need the flatness to control the leak rate. You need to read up on hydrostatic bearings to understand how to compute it, and why you need to.

Vickers clearly knows what they are doing. It's probably time to disassemble their pump and reverse- engineer it. I don't mean just copy a feature or two; I mean analyze in excruciating detail why each and every miniscule feature is there, or not there, and why it's the exact size it is.

Your goal should not be to find materials that don't gall when rubbed together. Your goal should be to arrive at a geometry that prevents any parts from rubbing on each other.



Mike Halloran
Pembroke Pines, FL, USA

 

[BigInch]

How long's the barrel? I'd love to calculate the miles per minute that turns out to be.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[drober]

The padded barrel has an OD of 1.565 inches.