Analysis of forces in the Bobcat arm and cylinders

To determine the force in the second hydraulic cylinder (the one that controls the dumping action of the bucket) a couple of measurements are needed. First, the total applied load of 1000lb is applied at a point 20 inches from point D. This point is also 22 inches from point F. The distance from point D to point F is 8 inches. The angle that the cylinder makes with the line DF is 146° . By doing the sum of the moments about point D, the force applied by the cylinder is found to be 4470lbs. The reaction forces at D are found by applying the sum of the forces for the cylinder, pin D, applied load system. Using this method, Dx is found to be 1376lb, and Ry is found to be 761lb. The total force applied by pin D is 1573lb.

Looking at the whole arm, and finding the forces in the first cylinder, we need a couple more measurements. The distance between point A and point C is 44.5". The cylinder acts on the arm at an angle of 21° . The distance from the load to point A is 116". However, for this calculation, the load is divided by two because there are two arms. The angle that the load makes with the line A to load is 76° . Applying the sum of the moments about point A, we find that the force that must be applied by the cylinder in order to keep the load from pushing the arm down is 3529lb. This leaves the reaction forces at point A. Using the sum of the forces in the y-direction results in only Ay and Fload. This means that Ay equals –Fload or 500lb. Using the sum of the forces in the x-direction yields Ax equal to –Fcyl or Ax equals –3529lb. This results in a total reaction force at A of 3564lb.