JR3 Balance for Ground Vehicle Testing
Western Michigan University's Applied Aerodynamics Laboratory is equipped with a JR3 balance (UFS-45A50-ITI) capable of measuring two components of force (drag and lift) with a standard maximum range of ± 50 lb with a digital resolution of 0.013 lb in each direction. The nominal accuracy of the balance is of ± 0.25 % of the measuring range, which translates on a nominal accuracy of ± 0.125 lb.
The model currently tested is connected to the balance is by having the ground plate bolted to the balance and then the semi-truck model attached to the ground plate through a set of four stilts, as represented in Fig. 1. Thus for the testing of another model it is recommended to build the model along with the ground plate. The ground plate will need to have six through holes that match the balance threaded holes shown in the top view of the balance in Fig. 2. The through holes that attach the ground plate to the balance must have a diameter of 7 mm and must be placed on a 59 mm diameter circle as shown in the previous figure. The holes are equally spaced (60o apart). Finally, the balance has a diameter of 101 mm.