Monday, December 29, 2008

Change in Load Question

The system consists of a fixed RPM electric motor, fixed displacement pump, system relief, cylinder, directional valve, and reservoir. If the cylinder is extending at a constant speed and the load opposing cylinder travel increases what happens to the speed of the cylinder?

Saturday, December 27, 2008

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Friday, December 26, 2008

Regenerative Circuit Question

Are the pressures on the Cap side and Rod side of a cylinder in a regenerative circuit equal?

Monday, December 22, 2008

Pressure Compensation

The flow across any hole is determined by the pressure drop or differential pressure across the hole and the temperature of the fluid. Pressure compensation keeps the pressure drop across the hole relatively constant regardless of the inlet or outlet pressure at the hole.

Saturday, December 20, 2008

Understanding the Spring

The spring is an essential part of any hydraulic system. One must understand the deflection vs force on the spring; this is called the spring constant. The greater the spring is deflected from its free state the more force it takes to deflect it further. This is a linear relationship. Cracking pressure is a result of the preload on the spring. Pressure drop vs flow is a result of the spring constant and the square root relationship of pressure drop vs flow during turbulent flow.

Saturday, December 13, 2008

Pump Pressure

Question of the day: What 2 things determine pressure at the pump outlet?

Sunday, December 7, 2008

Balance of Forces/Cylinder

A cylinder will travel at a constant velocity from 0-100% as long as the forces on both sides of the piston, the load force, and any other forces such as friction are in balance. When the forces are not in balance the piston and rod will accelerate (positively or negatively) until the forces are once again in balance.

Saturday, December 6, 2008

Hydraulic Application - Hydrostatic Pump circuit for Double Acting Cylinder

Pressure Drop

When using a sharp edged orifice the pressure drop across any hole size can be determined using the following formula.


This assumes that FLOW1 and DELTA PSI1 are known and the hole size remains the same.