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Ignore my last post, akkamaan. I think you mean when cylinder deadheads, a RV opens. For some reason, I was taking it to mean when the flow to the cylinder is throttled down.

This is the key thing. This is what I was curious about. The work port RV set at a lower pressure restricts the pressure the cylinders can get to. So to let the cylinders get to higher pressure, eliminate that and just have the system RV. But then you're dumping over that the whole time...

I mean why is

How so? For discussion:

So if I have a 10 GPM gear pump, and I want 7 GPM to the cylinder, what will the pressure be on the pump side of the DCV? Assume no plumbing pressure drops. Say max allowable system pressure set by relief valve is 3000 psi. Case 1: load pressure = 2500 psi. Case 2: load pressure = 500 psi...

I want to add that other pump manufacturers actually publish motor power required in the pressure-compensated state. Using that power figure and speed, you can calculate torque and compare to the full load torque to see where you are speed-wise. From one of the pump mfr graphs that I saw, the...

We tested an HPU a few months ago. We measured current with the swash plate neutral, pump in pressure-compensated state. For reference, full load amps was 57 per motor datasheet. Measured amps was 25. I had found a US Dept of Energy document that had some generic curves for Efficiency and...

This is an awesome document. I'm about halfway through.

You would think their published performance data would be conservative, for CYA purposes.

I agree with you. Apologies there. I was assuming that the "A" and "B" values on that graph on pg 12 applied to all compensator settings, but after looking more closely, I believe they apply to only the 315 bar (4568 psi) compensator setting. Trying to answer questions here and do the work at...

Good to know. I'll keep this in mind on future applications. Now that I think about it, the times the company has tested units and they seem to be drawing too much amperage, it's always been on the smaller units (1.5 HP, 2 HP, 3 HP). On the few bigger units I've observed in testing, amperage...

Ok, I've got a lot of reading to do now. Thanks for taking a shot at some of the parameters I was asking about.

The grinder was belt driven from the engine. I'll read the rest tomorrow. Thanks for responding.

As I said in a previous post, calcs were performed, checked, and checked again. Manufacturer data was used, and the calculated required HP was under 2. The motor selected was 2 HP rated. The proper pump was selected.

Makes good sense, and good to know. Good information. One of my original q's: If BDT = 275% FLT, is breakdown current = 275% full-load current? If not, what do you think current would be? I'll ask this again in a different way. Say a 2 HP motor during testing is drawing more than service...

I just looked through a Prince catalog, and it only gives the usual pressure drop vs flow curves, where the pressure drop increases as the flow increases. Same thing all the directional valve mfrs publish. No data (that I saw) on pressure drop as you meter full pump flow down to a lower value...

Thank you. Some follow up questions: 1. Do all manual valves send the unused flow to tank at less than relief pressure, or does this depend on the specific valve? 2. Is this accomplished by special componentry within the valve, or just by virtue of how the internal flow paths are connected...

No I meant what I said, and I'm keeping it. Please feel free to post your circuit diagram, if it answers my question.

This weekend I had at the house a Vermeer Stump Grinder SC362. I was looking at the exposed hydraulics while the operator was taking a break. There was a 2-section gear pump. There were 4 functions: 1 steering cyl, 2 pivoting cyls, 1 up-down cyl, and I think 1 hydraulic motor for driving...

I have never seen this data at more than service factor load. I know. I was hoping somebody with special / strong knowledge of this could estimate based on the numbers I gave, or give a rule of thumb like "efficiency is ~50% of full load efficiency at 2 x FLA". The new Fluid Power...