Rubber bearing propeller shaft10/28/2022 ![]() ![]() Where used on small boats, the bearing is often moulded in one cylindrical piece of rubber, although the inner surface is grooved so that it still functions as a stave bearing. This article in the Yachting Journal explains how a rubber bearing was replaced with Vesconite Hilube for this reason. ![]() Shaft vibration can be reduced with Vesconite because it can be machined to tight tolerances to achieve small running clearances. Vesconite Hilube is widely used for propeller shafts because the self-lubricating, homogeneous material has a low coefficient of friction (typically 0.10 to 0.12). The tradename "Cutless" is used for these rubber bearings and this name has also, along with its misspelling 'Cutlass', become a generic term for them. ![]() The name refers to a molded rubber bearing manufactured by Duramax Marine. The tradename "Cutless" is a registered trademark owned by Duramax Marine. Nitrile rubber and UHMW-polyethylene have also been used. Recent developments in composites have seen polyester resin and phenolic resin composites such as Feroform, ACM, Maritex and Orkot being used as well as elastomeric polymer materials from Thordon Bearings. In modern practice, Tufnol is often used. The historical material used for this was the tropical hardwood timber lignum vitae. They must also survive long-term immersion without rotting, softening or swelling. Stave bearings in ships must resist the forces in the bearing and offer adequate lubrication from the water alone. Other bearing types, such as some ball bearings, don't perform well under this type of use and may fail prematurely. Stave bearings are also well suited to applications such as rudder shafts, where rotation is intermittent and reciprocating, rather than continuous and unidirectional. When used on ships, the bearing is designed to run immersed in water, allowing its use outboard of the stern gland or stuffing box. The bearing is suitable for slow speeds and high loads. Stave bearings have long been associated with ships and their propeller shafts. ![]()
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