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Posted for Wschertz2@aol.com:
I must be missing something really important here. It doesn't make sense to
me
that the highest pressures should result in zero flow, and vice-versa. There
was no mention of deliberate restrictions (valves) in the lines. Also absent,
was any intimation that power input to the drive motor was varied.
Help me out here .... Jim S.
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Jim,
There is a valve (ball valve) on the exit side of the pump. Therefore, if I close the valve, and turn on the pump, it goes to its "stagnation" pressure, which is the highest pressure that the pump can generate. As you then start to open the valve, the water starts to flow, and the pressure that the pump can make is less, down to the point that the valve is full open and the pump is moving the maximum amount of water. These curves are typical for a centrifugal pump (which is what we have here)
I have some small corrections to make to the data, having made a careful measurement of the bucket and finding that it was 5.8 gallons instead of 5, and I think i can correct for the pressure effects in the tubing connecting the system to the pump.
With regards to the power input. The motor was an electric 1-HP motor from my table saw. It is a synchronous motor, that tries to always run at 3450 rpm. To vary the speed of the pump, I varied the pulley diameter. the motor will run at 3450 rpm at no load, and continue with only small variations up until you exceed its ability. I don't think that I was anywhere close to causing major slippage. The current the motor draws varies with the load.
Bill Schertz
KIS Cruiser #4045
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