be used in lieu of the bevel washers 98 the biasing member may alternatively comprise a rubber washer or any other well known member having spring like properties capable of applying a biasing force to the body 25 as shown in fig5 a 5c an alternative design shows the first engaging member on body 25 as a female member 104 and the second engaging member on the clutch disk 99 as a male member 105 referring to fig1 in the event that the flapper valve 76 should become stuck or otherwise unable to be pulled open by the chain 49 the drive shaft 26 could become damaged or the motor 20 could burn out due to the excessive torque the external arm 24 prevents such damage from occurring during normal operation the first engaging member 94 104 of the body 25 remains engaged with the second engaging member 95 105 of the clutch disk 99 as the drive shaft 26 begins to rotate through its 360 degree cycle the chain 49 is pulled by the tab 27 or handle swivel 50 attached to the body 25 of the arm 24 during the first 180 degrees of the rotation of drive shaft 26 the chain 49 lifts the flapper valve 76 allowing the reservoir tank 13 to be drained up on completion of the rotation the flapper valve 76 is closed in the event that the torque from the motor exceeds a fixed torque such as 2 5 inch pounds the first engaging member 94 104 disengages from the second engaging member 95 105 by compressing the biasing member such as in the form of bevel washers 98 as shown in fig4 a or a spring 100 as shown in fig6.