Re: Hyd Pump - What did I just buy?
Thought I'd post a little update on this. Have some good news and bad news on the Idex Micropump.
First the good news...no problem stopping the leaks in the shaft seal or housing. (Steve - I'll fill you in on that w/ PM later...ended up getting square o-rings for housing and quad rings for the shaft off McMaster so had to buy 50 pcs...will send you a handful to play with...they work good).
Now the bad news. I tried my Leimbach 12v motor to run this pump and it pulls a ton of current and doesn't have enough power to spin the pump to proper speed when it's running against the pressure relief - unless you feed it about 8 or 9 amps and even then it labors and never really spins up to a sustainable speed. I knew about this problem in previous posts but was hoping it was because I had the shaft too tight due to compressing the o-ring to seal the leak. So I did a serious of [poorly documented and unphotographed] experiments to see why the same motor that spins a Leimbach pump doesn't have the power to spin this pump. I will spare you the details and say that it ultimately led me back to review the specs for these pumps. Per L.G. Joe in the DIY Pump thread the Leimbach pump is a 350ml/min pump - not sure if that is max at full 10 bar (or is it 15?) but probably so. I didn't verify the 350 ml/min but sounds about right and Joe's numbers have always checked out before. So the Idex model 120 pump is spec'd for about 2000ml/min at 5.5 bar (80 p.s.i.) and the pumps they spec are shown to run 4000 RPM and pull 90 watts which would be 7.5 amps at 12v. That's a lot of current for a little motor.
Anyway...where am I going with all this babble...well I haven't completely drawn a conclusion yet...and I still think we can make this pump work...but my theroy right now is the Idex model 120 is trying to move about 6 times as much fluid as the Leimbach and these regular Johnson motors just weren't designed to generate that kind of power. Good news is these pumps have the extra capacity in a small package for the guys with big machines and big cylinders. Bad news is they are current hungry.
Next step is to run it geared down 3:1 or even more and see if the motor runs a comfortable speed and if it operates my test cylinders at the right rate. The pump seems to run 80 p.s.i. at pretty low RPMs so I am optimistic that lower RPM won't mean lower pressure...just lower volume and therefore ability to be driven by a 12v battery powered motor. Then I will insert the heavier spring I bought to modify the pressure relief to see if it runs closer to 10 bar, etc. etc.
Joe
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