A stave bearing is a simple journal bearing where a shaft rotates in a bearing housing. Rather than the usual arrangement where the fixed part of the bearing surrounds most of the circumference of the shaft in one or two pieces, a stave bearing uses a large number of axial stave

Stave

Stave can refer to:*Staff , a set of five horizontal lines and four spaces used in musical notation*Stave church, a Medieval wooden church with post and beam construction prevalent in Norway*The individual wood strips that form the sides of a barrel...

s to support the shaft. A large housing is made with grooves running along the shaft, these grooves being filled with strips of suitable material, originally wood.

Uses

Stave bearings have long been associated with ships and their propeller shafts. The bearing is suitable for slow speeds and high loads. When used on ships, the bearing is designed to run immersed in water, allowing its use outboard of the stern gland or stuffing box

Stuffing box

A stuffing box is an assembly which is used to house a gland seal. It is used to prevent leakage of fluid, such as water or steam, between sliding or turning parts of machine elements.-Boats:...

.

Stave bearings are also well suited to applications such as rudder shafts, where rotation is intermittent and reciprocating, rather than continuous and unidirectional. Other bearing types, such as some ball bearing

Ball bearing

A ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the bearing races.The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads. It achieves this by using at least two races to contain the balls and transmit...

s, don't perform well under this type of use and may fail prematurely.

Materials

The staves must resist the forces in the bearing and offer adequate lubrication from this water alone. They must also survive long-term immersion without rotting, softening or swelling. The historical material for this was the tropical hardwood timber, lignum vitae

Lignum vitae

Lignum vitae is a trade wood, also called guayacan or guaiacum, and in parts of Europe known as pockenholz, from trees of the genus Guaiacum. This wood was once very important for applications requiring a material with its extraordinary combination of strength, toughness and density...

. In modern practice, Tufnol is often used. Recent developments in composites have seen polyester resin and phenolic resin composites such as Maritex and Orkot being used.

Nitrile rubber

Nitrile rubber

Nitrile rubber, also known as Buna-N, Perbunan, or NBR, is a synthetic rubber copolymer of acrylonitrile and butadiene. Trade names include Nipol, Krynac and Europrene....

 and UHMW-polyethylene have also been used. The tradename "Cutless" is used for these rubber bearings and this name has also, along with its mis-spelling 'Cutlass', become a generic term for them.

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. Although small, these rubber bearings are still capable of handling a high power, even a 2,350 hp record-breaker like Bluebird K4

Bluebird K4

Blue Bird K4 was a powerboat commissioned in 1939 by Sir Malcolm Campbell, to rival the Americans' efforts in the fight for the world water speed record....

.

The use of non-metallic bearing materials may also simplify problems with electrolytic corrosion between shaft and housing.

Cooling

Although immersion alone is often sufficient to lubricate the bearing, additional cooling and also flushing away of any gritty particles that could damage may be achieved on large ships by a pumped flow of water to the inboard end of the bearing. This flow passes along grooves in the bearing surface, leading outboard. A low pressure of around 5 psi is adequate.