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To give readers an idea of how small this pump is, here's a few pics of just the pump, without the electric motor.

Here's a pic of what I'm using. The plastic bottle says it's ISO-68 Hydraulic oil, which Google searches tell me is a middle weight oil meant for heavy equipment use.

No, I have not yet tried a heavier weight oil,...but I do need to :) Edit: I'm currently using ISO-68 Hydraulic Oil.

Thanks for the kind words. I'm super happy with the operational range & performance of my little pump. One of two main reasons I built this pump was because the pressure washer pump I was using could not be regulated at low flow rates,...the DC motor would stall and stop at low flow rates. My...

I successfully pressure tested the boiler using my new home-built, 9 piston pump. This test demonstrated the new pump was capable of pressurizing the boiler to several different pressure points, up to 600 psi. The below pic shows the output plumbing of the boiler; the valve is used to slowly...

Goals achieved !! At the beginning of this thread I stated that I wanted to develop a feed water pump that could deliver 3 LPM at 600 psi. Today's tests came close enough to both of those goals that I'm claiming victory :cool: The pic below shows the pump attached to a 1kW 36vdc motor rated...

Since I will be replacing the 300 Watt motor I used for these tests, with a 1 kW motor, which I hope will be the final version, I did not take voltage, current, nor PWM duty cycle measurements. The general rule-of-thumb for monotube boilers, (as I understand) is the feed pump needs to be able...

I ran a few measurement tests using the small 300 watt motor driving the pump. At open flow, the motor will spin at 2060 rpm and output 5 LPM. Below I've listed the 4 test points which I measured: Pressure (psi) RPM Flow (Liters Per Minute) 100 760 1.35 100 1490 3.33 200 1060 2.19...

I really, really, really hate having to use this 5.3 Kg monster,....but with it's 1 kW power output, I'm 99% certain it has more than enough power. This is the same size motor I used on the 3 piston pressure washer, which develops higher pressure and flow rate. I also know it will run...

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% ?

I need an even bigger motor :confused: 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...

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...

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...

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...

The sandwich method is what I used to drill holes and mill slots through 0.010" (0.26mm) thick stainless sheet to make the reed valves in the photo below. All discs are 3.3" diameter and were clamped onto the mill table through the center hole. I used 3mm thick polycarbonate sheet top and...

If the area isn't too large, sandwich the metal foil between two sheets of polycarbonate. Drill though the top sheet into the foil and then slightly into the bottom sheet. Clear polycarbonate allows you see what your progress.

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...

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...

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...

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...