Excellent of hydraulic
(1)It is small dimensional and strong.
(2)It is liberty and changes the speed.
(3)Easy adjust with the force and speed.
(4)It’s free for the momentum transfer.
(5)Install anywhere.
(6)Because the transfer of medium is liquid, so they are shock absorbing 
    and steady and reliability.



Defective of hydraulic
(1)Sometimes leakage.
(2)Must to be careful cause fire accident.
(3)Temperature influence.
(4)It is difficult for installed.
(5)Maybe mixed with air.
(6)Because the state for hydraulic system is close, when order, to repair
    some trouble.  
(7)Stop state, but the motor is running, so, they cannot to save energy.