My buddy Stan wanted an economical "yolk-walk" apparatus. We made one out of static pipe fixtures and threaded pipe. With this apparatus, Stan can do the yolk walk, presses, quarter squats, half/full squats (with a step-up box), 45-degree horizontal pull-ups, incline presses, and more. He has had 440 pounds of plates on this muscle builder, and it seems that it would hold solid to at least 500 pounds.
Our yolk-walk machine quite resembles my Harvey Maxime apparatus. However, the yolk-walk device uses threaded pipe and fittings to secure connections, while the Harvey Maxime bar uses Kee Klamps to get the job done.