How many rpm was the video? Is the line closer to the camera the input?
Axial Swash Plate Feed Pump
- Thread starter Toymaker
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How many rpm was the video? Is the line closer to the camera the input?
Yes, the line closer to the camera is the input. RPM was approx. 300 when the bubbles were visible.
Were the bubbles from just starting the pump or was the pump generating them from gas pulled out of the water?
Might have a problem with the pistons pulling vacuum on partially filled chambers and pulling air out of solution and sorta chewing on it till it gets expelled.
That might suggest the problem is water not getting into the pump easily enough?
Sounds good though!
Might have a problem with the pistons pulling vacuum on partially filled chambers and pulling air out of solution and sorta chewing on it till it gets expelled.
That might suggest the problem is water not getting into the pump easily enough?
Sounds good though!
I intentionally pulled the input line out of the water to allow a little air to be sucked into the pump as a means to view the output flow. I see no air bubbles in the line during normal open flow or pressure flow conditions.
I opened the swash plate section of the pump after the motor overheating as I wanted to inspect the plate and slippers for signs of excessive wear or water intrusion into the oiled section of the pump. The swash plate and slippers looked new, and there were only a tiny few droplets of water to be found in the oiled section.
I opened the swash plate section of the pump after the motor overheating as I wanted to inspect the plate and slippers for signs of excessive wear or water intrusion into the oiled section of the pump. The swash plate and slippers looked new, and there were only a tiny few droplets of water to be found in the oiled section.
Rev 2 Initial test results are very encouraging.
Installed a much larger motor with gear reduction, smaller, weaker springs pushing on the check-valve balls, and ceramic balls for the valves replaced the steel balls.
Below shows the new motor connected to the pump, along with the older motor.
The motor is rated for 24 VDC at 950 rpm at the gear reduction output shaft. At 25 VDC output shaft goes up to 1000 rpm. Open flow = 2 LPM at 1000 rpm. I believe I'm still getting some leakage around my check valves, but they're all functioning much, much better as shown by the much smoother output at 120 to 140 psi.
I was able to go up to 300 psi but when I did, I could hear the shaft coupler slipping,...I need to put keyways on both shafts
Installed a much larger motor with gear reduction, smaller, weaker springs pushing on the check-valve balls, and ceramic balls for the valves replaced the steel balls.
Below shows the new motor connected to the pump, along with the older motor.
The motor is rated for 24 VDC at 950 rpm at the gear reduction output shaft. At 25 VDC output shaft goes up to 1000 rpm. Open flow = 2 LPM at 1000 rpm. I believe I'm still getting some leakage around my check valves, but they're all functioning much, much better as shown by the much smoother output at 120 to 140 psi.
I was able to go up to 300 psi but when I did, I could hear the shaft coupler slipping,...I need to put keyways on both shafts
Nice! That needle is way more under control now!Rev 2 Initial test results are very encouraging.
Installed a much larger motor with gear reduction, smaller, weaker springs pushing on the check-valve balls, and ceramic balls for the valves replaced the steel balls.
Below shows the new motor connected to the pump, along with the older motor.
View attachment 158366
The motor is rated for 24 VDC at 950 rpm at the gear reduction output shaft. At 25 VDC output shaft goes up to 1000 rpm. Open flow = 2 LPM at 1000 rpm. I believe I'm still getting some leakage around my check valves, but they're all functioning much, much better as shown by the much smoother output at 120 to 140 psi.
I was able to go up to 300 psi but when I did, I could hear the shaft coupler slipping,...I need to put keyways on both shafts
View attachment 158367
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I'm theorizing that the valves need a break-in period, and will seal better after some unknown minutes or hours of operation. The valve block is machined from 6061 aluminum and the 6mm spheres are Silicone Nitride (Si3N4) ceramic. Each time the unyielding ceramic spheres smash into the much softer 6061 aluminum seat, that seat should be slightly deformed into the curved shape of the sphere. Any small non-uniformities in the valve seats will be hammered into the rounded surface of the spheres.
To test this theory, I'm running the pump at 100 psi and watching the pressure guage for any changes.
To test this theory, I'm running the pump at 100 psi and watching the pressure guage for any changes.
The pulses have inertia, so you might be seeing water hammer as needle vibration, which is to say that the flow might possibly be smoother then it appears.
So long as the volume is right I'd be tempted to hook everything up and see how the turbine responds
So long as the volume is right I'd be tempted to hook everything up and see how the turbine responds
The pulses have inertia, so you might be seeing water hammer as needle vibration, which is to say that the flow might possibly be smoother then it appears.
So long as the volume is right I'd be tempted to hook everything up and see how the turbine responds
I too am tempted to hook the pump to the boiler and give a go,....BUT,....I really do need to wait until I'm getting at least 500 psi at 1.5 LPM. The pump cannot produce those results yet.
Also, now that I'm running the pump at 100 to 200 psi for stretches of about 20 minutes, I'm seeing more water entering the oiled area and I'm loosing a lot of oil into the pumped water; the current O-rings either need to be tighter against the cylinder walls, or doubled, or both.
Maybe a heavier weight oil? Like a 40 weight?
Problem found and fixed. What I thought was a valve problem turned out to be a design flaw (or oversite) which I made when changing from using valve & port plates, to using 6mm balls in drilled holes as valves. A spring (see red arrow in below drawing) was used to push the valve plate and port plates together; however, when those plates were removed and replaced with 6mm ball valves, the spring no longer served a useful purpose, and was preventing the rocker plate from working properly. That spring has now been replaced with a solid bushing (green lines).
The pump now reaches 500 psi, though the dial guage is still quite bouncy at that pressure. I've little doubt the pump will develop the 800 psi I want, but I need a larger motor as the current 100 watt motor, even with the geared speed reduction, is not capable of turning the pump at that high pressure; it's becoming excessively HOT. I've ordered a 300 watt motor which should arrive in a few days.
The pump now reaches 500 psi, though the dial guage is still quite bouncy at that pressure. I've little doubt the pump will develop the 800 psi I want, but I need a larger motor as the current 100 watt motor, even with the geared speed reduction, is not capable of turning the pump at that high pressure; it's becoming excessively HOT. I've ordered a 300 watt motor which should arrive in a few days.
Nice! Well sorted.
Does the water stay out of the oil now?
500psi is a nice mile stone.
I remade all 9 pistons from stainless steel and cut the O-ring channels 0.01 less deep, causing the O-rings to fit much tighter in the cylinders. I found a report stating that pistons should be made of hardened steel as it slides better against brass,...well, stainless is as close as I can easily get to hardened steel. Likely due to the tighter O-rings,...I have no more water in the oil
The same report stated slippers should be made from high tensile brass while the swash plate should be made from hardened steel. Again, hardening steel is not something I want to do, so I epoxied a high gloss stainless steel plate onto a 6061 aluminum swash plate. So far it's working quite well. I took the below photo to show the mirror finish on the stainless plate. The reduced friction between slippers and stainless swash plate is noticeably less compared to the brass swash plate.
That's awesome!I remade all 9 pistons from stainless steel and cut the O-ring channels 0.01 less deep, causing the O-rings to fit much tighter in the cylinders. I found a report stating that pistons should be made of hardened steel as it slides better against brass,...well, stainless is as close as I can easily get to hardened steel. Likely due to the tighter O-rings,...I have no more water in the oil
View attachment 158622
The same report stated slippers should be made from high tensile brass while the swash plate should be made from hardened steel. Again, hardening steel is not something I want to do, so I epoxied a high gloss stainless steel plate onto a 6061 aluminum swash plate. So far it's working quite well. I took the below photo to show the mirror finish on the stainless plate. The reduced friction between slippers and stainless swash plate is noticeably less compared to the brass swash plate.
View attachment 158623
The brass pistons look like they were starting to gall a bit.
Thanks
I'm super happy with the results thus far.Wear on the aluminum rocker plate, which pulls the pistons up, has reduced the piston's stroke from 0.24" to 0.21", resulting in a reduced displacement from 0.00276 down to 0.00241 liters.
Calculated open flow is now 2.41 LPM at 1000 RPM. Measured open flow is 2.38 LPM.
The new 300 watt motor is rated for 2000 rpm,...should be interesting to see if I can get 3LPM at 500 psi.
Below is a closer view of the brass pistons,...yes, there does appear to be a bit of galling. Interesting that the pistons appear to be rotating as they're being pushed and pulled; I did not expect that.
I need an even bigger motor After connecting the larger, 300W, 2000 rpm motor, I can report mixed results. The pump itself has shown better than expected results. With the larger motor I'm able to maintain 1000 RPM at a pressure of 300 psi, with minimal pulsing showing on the dial guage (+/- 40 psi), and although I did not measured the flow rate at 300 PSI, it appears to be 2 or 3 LPM. These are the results I was hoping for.
Now for the bad news; the conditions described above are the max continuous capabilities for this motor. When I increase the pressure to 400 psi, RPMs drop below 700 which noticeably decreases flow rate; when I increase power from the motor speed controller in an attempt to increase RPM, the motor literally begins to smoke.
The hydraulic power formula tells me that 250W should provide 435 PSI at 5 LPM, but that's not what I'm seeing. Well, there's theory, and there's real-world results. My real-world results are telling me to look for at least a 500W motor.
After connecting the larger, 300W, 2000 rpm motor, I can report mixed results. The pump itself has shown better than expected results. With the larger motor I'm able to maintain 1000 RPM at a pressure of 300 psi, with minimal pulsing showing on the dial guage (+/- 40 psi), and although I did not measured the flow rate at 300 PSI, it appears to be 2 or 3 LPM. These are the results I was hoping for.Now for the bad news; the conditions described above are the max continuous capabilities for this motor. When I increase the pressure to 400 psi, RPMs drop below 700 which noticeably decreases flow rate; when I increase power from the motor speed controller in an attempt to increase RPM, the motor literally begins to smoke.
The hydraulic power formula tells me that 250W should provide 435 PSI at 5 LPM, but that's not what I'm seeing. Well, there's theory, and there's real-world results. My real-world results are telling me to look for at least a 500W motor.
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Real world is a bustard.
I'd go oversized on the motor, so it has the ability to self cool while staying away from it's SF rating.
Good news that the pump is working well. At least, it sounds like, you could run the pump in at the lower pressure and lower rpm and either end up with it already for real duty or at least identify any future failure modes.
I'd go oversized on the motor, so it has the ability to self cool while staying away from it's SF rating.
Good news that the pump is working well. At least, it sounds like, you could run the pump in at the lower pressure and lower rpm and either end up with it already for real duty or at least identify any future failure modes.
Toymaker,
Have you taken mechanical drag into consideration? There is quite a bit with these types of pumps.
Cheers
Andrew
I know there's friction between the moving parts inside the pump, but calculating the amount in terms of additional watts needed to overcome said friction is well beyond my expertise.
Are you aware of any "ballpark" numbers used to approximate frictional losses? 10% ? 30% ?
Let me get back to you.
I have some ideas.
I have some ideas.
