Welcome to the Ask the Expert Blog, where our engineering experts answer questions about retaining ring and wave spring design and performance. This week, our engineers answer questions about Hoopster retaining rings and single turn wave springs.

Can you use a Hoopster retaining ring without a groove?  Will friction be enough to keep it in?

Hoopster retaining rings, just like any retaining ring, is a removal shoulder you can incorporate into your design.  Most retaining rings need to be installed into a groove to be properly positioned and resist any thrust load it is subjected to.  A Hoopster without a groove will likely not have enough friction generated from cling to hold its position if a thrust load is applied.

Is it possible to stack wave springs as you might stack disc springs? Or do they require solid contact points on each end?

Yes, Single-Turn Gap-Type wave springs can be stacked to achieve similar characteristics to disc springs. Similar to a Nested Wave Spring design, wave springs can be stacked to increase the spring rate. To decrease the spring rate and increase deflection, Single-Turn wave springs need to be stacked with a shim separating each spring, which simulates a Crest-to-Crest wave spring. Stacking increases the number of moving parts required to perform a function. 
Many of our customers prefer to use one spring to get the spring characteristics they require and not have to orient multiple parts in a specific pattern like what is required by disc springs because this could lead to mistakes during assembly. If you have a situation where stacking is required, you may want to consider using a custom design to meet your specific needs.