Case Study #3

Customer needed a drop-in replacement for another manufacturer’s universal joint; they needed our unit to be perfectly compatible with the rest of their assembly, and there were numerous constraints that made it impossible for them to use one of our standard products.

We were able to offer them a heavily customized UJ, in a non-standard size (7/8 inch outer diameter, between our size 12D and our size 16D); in a special alloy of steel, with a special plating; with cross-drilled holes to their drawing, to pin the joint to the shafts.

Two large additional hurdles remained: The customer needed the joint to be particularly flexible at one point, so that the hubs could be brought to an angle of 90 degrees at that one point; and they wanted the boot to be fixed to the yokes with cups, rather than with cable ties.

Our standard UJ configuration has a unique shape to the yokes; unlike most universal joints, we’ve left as much material on the yoke as possible, so that the joint can rotate through 45 degrees throughout a rotation, but at any one particular point in that rotation, it’s not capable of flexing much more than 45 degrees. The yoke’s shape is complex, and includes swept and curved surfaces that can only be produced with a CNC machine tool with a large number axes. We’ve done this to maximize strength of the UJ.

In order to accommodate the customer’s flexibility requirement, we had to change our internal geometry and mill away additional material. We were still able to use fillets and otherwise optimized geometry to maintain the strength required to withstand the customer’s maximum torque requirements, with a large safety factor.

Prior to this project, we had always secured our boots with cable ties; this is an inexpensive method that allows the boots to be removed so that the joint can be re-lubed. However, this customer required that we use formed metal cups for attachment of the boot. We designed and tested cups that would work with our existing boots. We were so pleased with the performance of these cups that we now offer cups as an option for all sizes of standard UJ.