PC1800 Front Shovel (1/12)

[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