Build a frame for your practice barrel. Weld the channel iron into a 4-foot-by-6-foot rectangular frame. Weld two cross braces into the middle, leaving just the width of the car hub between the braces.
Weld the car hub to the frame, centering the hub in the middle of the frame between the cross braces. While the lug bolts on the hub can be placed up or down, it is easiest to place the hub with the bolts down.
Attach the three car springs to the hub in a triangular pattern using three of the U bolts. Be sure to place two springs toward the back of the frame and one toward the front. When the bucking barrel is finished, this will simulate the kicking action of a bull with his hind feet as well as the dropping action of the front end.
Again using the U bolts, bolt the springs to a piece of channel iron that has been cut just big enough to cover the springs.
Weld the barrel to the channel iron, centering its weight over the three springs.
Place the bull rope around the center of the barrel and begin practice. The barrel will begin to move with the rider, allowing the rider to practice without assistance. While the springs will simulate the kicking and dropping action of the bull, the hub will turn with the rider's movements, simulating a final element of bull motion: spin.