The transient behaviour of hydraulic motors has been widely investigated by many researchers. Most analysis of dynamic phenomena in hydraulic motors has considered the motor as a system with linear damping. Therefore, the results of these studies on hydraulic motors can not apply to the non-linearly damped air motors.
In this report, the air motor behaviour in the starting and stopping phase has been analyzed by numerical method. The analysis results have been confirmed by several experiments with a radial piston air motor.
Some of the results of studies are as follows.
(1) Close agreement between experimental and theoretical results of rotational speed of motor was obtained.
(2) Motor start/stop period increased nearly in proportion to the inertial load.
(3) The motor stopping time required by an outlet valve was approximately one-half of that by an inlet valve.

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Special care is taken to avoid hoses in hydraulic circuit and air bubbles in hydraulic oil as these cause undesirable hydraulic cylinder motions like vibration and jumping during its starting and stopping. Analytical and experimental study was conducted on the transient characteristics in the elastic circuit of the new-type non-jumping flow control valve presented in the previous paper by the present authors.
Analysis on the effect of the elasticity of the circuit on the motion of the cylinder showed that the newtype valve was much more effective than the conventional one to eliminate such jumping even in the elastic circuit. Experimental results also showed better characteristics of the new-type valve with elastic hoses.

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