Scotch yoke actuator equation
Scotch yoke actuator equation
(OP)
thread404-300325: Scotch Yoke Actuator Torque Output
It was noted in this previous thread that a scotch-yoke actuator has a strange relationship between angle of rotation and output torque. The torque vs. angle curve is a parabola shape. None of the many answers actually gave a useful solution to the question. I recently figured this out and found this thread and thought I would post a more helpful solution. See attached force balance.
The reason this is counter-intuitive is because the output force normal to the lever arm of the actuator is actually greater than linear output in the cylinder (Pressure * Area). It works this way because of the direction of each reaction force as shown.
It was noted in this previous thread that a scotch-yoke actuator has a strange relationship between angle of rotation and output torque. The torque vs. angle curve is a parabola shape. None of the many answers actually gave a useful solution to the question. I recently figured this out and found this thread and thought I would post a more helpful solution. See attached force balance.
The reason this is counter-intuitive is because the output force normal to the lever arm of the actuator is actually greater than linear output in the cylinder (Pressure * Area). It works this way because of the direction of each reaction force as shown.





RE: Scotch yoke actuator equation
"Engineers like to solve problems. If there are no problems handily available, they will create their own problems." -Scott Adams
RE: Scotch yoke actuator equation
vector times the amplitude of that force, FXR.=FRsin(theta) and Rsin
(theta) is constant.
So, given that the force vector is constant, it must follow that the torque remains constant for this problem, period.
So exactly where is the mystery?
The higher force on the slot is accompanied by the lower normal distance so that, the torque is the same.
RE: Scotch yoke actuator equation
RE: Scotch yoke actuator equation
RE: Scotch yoke actuator equation
which makes me question the load balance on the link ... if this is a two force member, then the two forces need to have the same link of action, which would imply they acting along the slot (not across it as assumed). which would imply that the only time the original assumption "static equilibrium" is achieved is when the valve is fully open or fully closed, when both pins are bearing against the ends of the slot.