26b the water thrust from the periphery of the impeller is at different angles for low flow and high flow the balance weight in the regions 60 61 must be widely dispersed to balance over the flow range the weight of the water 66 in the blocked off cup can be utilized to balance part of the thrust by lessening the balance weight in the regions 60 61 the thrust is opposite to a velocity vector v shown in fig1 u is the peripheral velocity vr is the radial velocity and v is the vector sum of the two components in fig1 the opposite reaction to v would only hit a vane 30 at the extreme end 70 as radial velocity increases the resultant velocity v would become more radial to the center of the impeller and the thrust presses against more of the vane causing greater dynamic unbalance the impeller must be designed to keep the radial velocity low enough that the reaction thrust from vector v never hits a vane or at most hits very little of a vane as shown in fig1 as can be seen in fig1 the water 66 in the blocked off cut is located on opposite sides of the centerline 42 and can be a balance weight for all or part of the suction eye blocking wall 56 a successful dynamically balanced impeller relies on a very scientific means of balancing all of the variables even so a means of actually testing and precisely determining the final balance which is not completely achieved in.