Adapt the speed and click the flag.. If you check the movement of the rod (brown), it's not regular like a wheel. In machines - mills, steam engines, car, even a bicycle - the same movement does not give the same result depending whether the crank (orange) is in one place or another.
The calculations are well explained on wikipedia, if you want them in full. The movement is right, but the calculation needs explaining. The movement of the slider (black) is the most important. It can only go left or right. As the crank turns, the rod pushes or pulls the slider. The distance of the slider to the end of the crank has to remain the same.
