May 28, 2019 | Case Studies

Engineered Plastics Provide Quieter, Smoother Operation for Boat Dock & Lift Customer

The Customer

The customer is an upper Midwest manufacturer of maintenance-free boat, pontoon, and personal watercraft docks and lifts.

The Challenge

With numerous boat lift manufacturers in the area, it’s no wonder that different providers have differing opinions on which materials work best for different applications. For example, when it comes to pulleys, there are several styles in use today, including aluminum with bronze bushings, Acetal (Delrin), and injection molded plastics. There are certain environments that these types are best suited for—no solution works best across every application.

The Solution

The customer came to Cope Plastics seeking an alternative solution because neither aluminum pulleys nor injection molded pulleys were giving them ideal results. Both the aluminum and injection-molded pulleys (which require bronze or alternative metal bushings) were causing squealing noises and “stick-and-slip” motion during normal operation. This result is common with metal materials since metallic bushings have a less desirable coefficient of friction (COF) for this application, which causes premature wear and stress on the entire lift.

They had also explored a polymer alternative with injection molded sheaves, which offered a lighter pulley and better mating surface for the cable. However, the injection molded components proved less tolerable of the stress of operation, causing them to fail. They discovered that the injection molded polymer still required a bronze or other metallic bushings to make it viable for use at all.

The Cope Plastics team developed sheaves prototypes that were machined from solid Nylon rods that needed no metallic bushing. They also deployed rigorous testing to prove the solution was able to stand up to the customer’s configuration. Through comparison with the injection-molded and aluminum alternatives, The Cope team was able to demonstrate that the machined Nylon sheaves were a far superior solution that provided a viable alternative to injection-molded and machined metal components.


Our team at Cope Plastics is passionate about solving problems for our customers. We don’t easily give up when we are presented with a challenge, and this case was no exception. We will always continue to prototype and test until we find a solution that works for each customer’s unique needs.

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