what is different between hydraulic motor and hydrostatic motor

Same differnce.

Correct!

Hydraustatmotor just means that the hydraulic motor is used in a closed loop. meaning that there is always filling pressure in the A and B port. 99% of the motors used in a hydraustat are bi-directional. 90% plunjer motor.

The pump is the major difference, it has a filling pump to fill and flush the system.

The flushing valve can be fit in the pump or motor (motor option)

You could say that a motor with flushing valve is a hydraustat motor but it can also be used in an open loop, return pressure is used the flush and cool the motor housing.

Lets not forget that there are hydraulic motors wich can't withstand back or filling pressure in the returnline and cant be used in a closed loop!

Best regards!

Hello DaveB:

That was well explained! GA on it's way.

A hydrostatic motor has the same variable type of system that a hydrostatic pump has. In other words the swash plate is variable by an external control, thus you can vary the speed and direction of the motor. Most of the time these motors are supplied by constant flow pumps. The most common application is a hydrostatic pump with fixed motors. The motor speeds and directions can only be varied by the pump. Most applications are one pump to one motor. So a skid steer for example, has two pumps (technically four pumps) Left side pump/motor, Right side pump/motor, a charge pump, and a pump for the auxilaries.

In my point of vieuw hydraustatic motor does'nt need te be adjustable . There are many hydraustatical systems with fixed motors.

If you like to call a variable motor a hydraustatical motor then this is up to you.

Hydraustats are often used as for driving perpose. The pump regulates the flow forward or backwards, correct! The motor can be fixed, variable in to stage or variable depending on pressure. (Motor is set at small volume per rev and volume per rev is increasing as pressure rises) The last one is often used for heavy epquipment above 10.000Kg

I have designed hydraustatical system from 1 up to 3 motors in series. Even seen machine with 16 motors in series.

All motors wich could have been used in open loop systems aswel.

Hydraustatical drive can be seen as a general therm for forces applied by pressure. open or closed loop.

Hydraudynamical drive is the well know as fluidclutch or torque converter wich is comonly used in every automated gearboxes (force applied by internal flow)

I hope somebody understand what I mean with these last lines.

Best regards,

A good application of a Hydrostatic motor is this: A diesel engine powering a 50gpm hydraulic pump at 1800psi on a log chipper. This system has minimal electronics and the cylinders are designed to run at a constant pressure. The feed rollers use a hydrostatic motor to control the feed speed and reversing of the rollers by the operator in the control cab. The control on the speed/reverse in this particular motor is a manual operation by the use of a cable. However, this same motor can be ordered with electronics. In some applications, this system is easier than trying to use electric motors with vfd's. Check the Saur-Danfoss or the Parker Hydraulics Websites for Variable Displacement Motors.

Harmen had the best common sense answer... because IMO hydrostatic hydraulics means a transmission of power by pushing on a confined fluid. Therefore regardless of what hydraulic component you may have...hydrostatics is present. But I did not vote GA because the whole post did not really hold true... The first comment was quite OK but some manufacturers terms based on component design (piston pumps... off topic) are called hydrostatics.

off topic///

Take for example a standard inline piston pumps (eg rexroth A10VSO) has pistons sliding on a cylinder block are parallel to each other. Rexroth call A4VS(sturdy design) pumps as hydrostatic , just because they can be applied(most in mobile closed loop due to engine speed variations) with much better performance(lesser possibility of slipper pad to stay out of contact from the swashplate) due to a slightly angled pistons(centrifugal action).

Hydraulic motors are either fix or variable (rexroth design=control of the secondary unit).

I hope this helps...

If the hydraulic mOtor that u say is the mOtor that uses hydraulic pResSure and flow to transmit mechanicAl power then they are the same.all mOtors either useD in close or open hydraulic circuit cAn be cAlLeD hydrostatic mOtor becAuse it uses hydrostatics theory or pRinciple in transmiting power.