Couplings FAQs

Are custom couplings more expensive than standard couplings?

No, the engineering process required to create your custom flexure is completely free and is part of our committed service to you. Pricing is a function of the complexity of the design and the material specified.

Do specialty or non-standard couplings take longer to manufacture?

No, just because they are referred to as “non-standard” does not mean that we may not already have these products in our inventory.

What is meant by “single start” and “multiple starts”?

A single start spring is a single continuous coil element that starts at one end and terminates at the other end. This configuration is common to most springs. A “double start” spring has two intertwined continuous coil elements phased 180 degrees apart. In effect, this puts two independent helixes in the same cylindrical plane. Multiple start flexures such as triple start etc. are similar extensions of the concept.

What are some of the benefits of multiple start flexures?

Multiple start flexures are beneficial because they not only provide redundant elastic elements should a failure occur, but a failed element (coil) will be physically trapped by the remaining ones.

A multiple start compression or extension spring is balanced when a load is applied, which prevents tipping. Traditional wire springs and single-start machined springs have an unresolved moment when a load is applied. A coupling with a multiple start flexure will have a stiffer torsional rate and can transmit more torque compared to a single start flexure.

What does “relief” mean for a coupling?

A coupling with relief allows both shafts to enter the flexible region. The diameter through the flexible part of the coupling is larger than the diameter of the two shafts. The ends of the two shafts can operate very close together when a relieved coupling is used. For a non-relieved coupling, each shaft must not go into the flexible region. In some cases, there will be a step to prevent the shaft from entering the flexible region.