Quote:
Originally Posted by sparkycuda
The hydraulic stuff can get confusing very quickly. Yes, a fixed displacement pump will deliver same volume for same pump speed, but if divided between circuits, each circuit gets only a part of that volume, so each function will be slower than each individually. Also, for a given valve opening, oil volume is directly related to pressure on that circuit. If using two circuits at once and both valves are opened the same amount, the circuit with the least resistance (and lower required pressure to move it) will move first. Only when that circuit bottoms out or it's valve is closed, will the other (higher required pressure) function move. Throttling or feathering the two valves during operation is the only way to compensate so both functions can move simultaneously while operating at different circuit pressures. Pressure-compensated (and usually with variable displacement pumps) take care of this for operators, but are much more complicated systems. Yes, the open center system does reduce heat and horsepower needed when in neutral. But having some "standby" pressure, as Mario stated, does give quicker response when activating. Also, open center may allow a function to drop a bit when first pressurizing a circuit - I don't think our model circuits have load-check valves to prevent this.
Ken
|
Yup....it does get confusing very quickly for me!!! Lol
Here is what I understand....if a pump at a given RPM moves 2 gal/min is attached to a cylinder that has a total volume of 2 gallons it should take one minute to fill the cylinder....if you have two of these 2 gallons cylinders it will take longer to fill them both, in this case twice as long. The larger the total volume of the cylinders being used the longer it takes to fill them all and the cylinder movement speed will be reduced accordingly. What I don't understands is why this isn't happening like it should....this pump supplies much more volume than what is really needed....there should be a surplus of volume left over when using multiple cylinders....but where is this surplus going??? I think that in this valve body there is always some flow allowed to bypass the spools and flow to the return port even when the spools are totally open to the cylinders!!?? One would think that all the flow would be channeled through the spools that are being used and only allowed back to the return through the return hoses on the cylinders. Yes/No ???