Stave bearing

Last updated

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 staves 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.

Contents

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.

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

Materials

Stave bearings in ships must resist the forces in the bearing and offer adequate lubrication from the water alone. They must also survive long-term immersion without rotting, softening or swelling. The historical material used for this was the tropical hardwood timber lignum vitae. In modern practice, Tufnol is often used. [1] 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. [2]

Nitrile rubber and UHMW-polyethylene have also been used. [3] [4] [5] The tradename "Cutless" is a registered trademark owned by Duramax Marine. The name refers to a molded rubber bearing manufactured by Duramax Marine. [6] 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. [7]

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 result is a long wear-life. [8] Shaft vibration can be reduced with Vesconite because it can be machined to tight tolerances to achieve small running clearances. This article in the Yachting Journal explains how a rubber bearing was replaced with Vesconite Hilube for this reason.

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 . [9]

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 cause 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. [1]

Related Research Articles

<span class="mw-page-title-main">Propeller</span> Device that transmits rotational power into linear thrust on a fluid

A propeller is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon a working fluid such as water or air. Propellers are used to pump fluid through a pipe or duct, or to create thrust to propel a boat through water or an aircraft through air. The blades are shaped so that their rotational motion through the fluid causes a pressure difference between the two surfaces of the blade by Bernoulli's principle which exerts force on the fluid. Most marine propellers are screw propellers with helical blades rotating on a propeller shaft with an approximately horizontal axis.

<span class="mw-page-title-main">Lignum vitae</span> A type of wood particularly heavy and hard

Lignum vitae is a wood, also called guayacan or guaiacum, and in parts of Europe known as Pockholz or pokhout, from trees of the genus Guaiacum. The trees are indigenous to the Caribbean and the northern coast of South America and have been an important export crop to Europe since the beginning of the 16th century. The wood was once very important for applications requiring a material with its extraordinary combination of strength, toughness, and density. It is also the national tree of the Bahamas, and the Jamaican national flower.

<span class="mw-page-title-main">Ball bearing</span> Type of rolling-element bearing

A ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the bearing races.

Fluid bearings are bearings in which the load is supported by a thin layer of rapidly moving pressurized liquid or gas between the bearing surfaces. Since there is no contact between the moving parts, there is no sliding friction, allowing fluid bearings to have lower friction, wear and vibration than many other types of bearings. Thus, it is possible for some fluid bearings to have near-zero wear if operated correctly.

<span class="mw-page-title-main">Bearing (mechanical)</span> Mechanism to constrain relative movement to the desired motion and reduce friction

A bearing is a machine element that constrains relative motion to only the desired motion and reduces friction between moving parts. The design of the bearing may, for example, provide for free linear movement of the moving part or for free rotation around a fixed axis; or, it may prevent a motion by controlling the vectors of normal forces that bear on the moving parts. Most bearings facilitate the desired motion by minimizing friction. Bearings are classified broadly according to the type of operation, the motions allowed, or the directions of the loads (forces) applied to the parts.

<span class="mw-page-title-main">Plain bearing</span> Simplest type of bearing, comprising just a bearing surface and no rolling elements

A plain bearing, or more commonly sliding contact bearing and slide bearing, is the simplest type of bearing, comprising just a bearing surface and no rolling elements. Therefore, the journal slides over the bearing surface. The simplest example of a plain bearing is a shaft rotating in a hole. A simple linear bearing can be a pair of flat surfaces designed to allow motion; e.g., a drawer and the slides it rests on or the ways on the bed of a lathe.

<span class="mw-page-title-main">Rolling-element bearing</span> Bearing which carries a load with rolling elements placed between two grooved rings

In mechanical engineering, a rolling-element bearing, also known as a rolling bearing, is a bearing which carries a load by placing rolling elements between two concentric, grooved rings called races. The relative motion of the races causes the rolling elements to roll with very little rolling resistance and with little sliding.

<span class="mw-page-title-main">Thrust bearing</span> Family of rotary bearings designed to support axial loads

A thrust bearing is a particular type of rotary bearing. Like other bearings they permanently rotate between parts, but they are designed to support a predominantly axial load.

<span class="mw-page-title-main">Pillow block bearing</span> Bracket used to provide support to rotating shafts

A pillow block bearing is a pedestal used to support a rotating shaft with the help of compatible bearings and various accessories. The assembly consists of a mounting block which houses a bearing. The block is mounted to a foundation, and a shaft is inserted, allowing the inner part of the bearing/shaft to rotate. The inside of the bearing is typically 0.025 millimetres (0.001 in) larger diameter than the shaft to ensure a tight fit. Set screws, locking collars, or set collars are commonly used to secure the shaft. Housing material for a pillow block is typically made of cast iron or cast steel.

A stuffing box or gland package 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.

<span class="mw-page-title-main">Reduction drive</span> Mechanical device to shift rotational speed

A reduction drive is a mechanical device to shift rotational speed. A planetary reduction drive is a small scale version using ball bearings in an epicyclic arrangement instead of toothed gears.

<span class="mw-page-title-main">Novotext</span>

Novotext is a trade name for cotton textile-phenolic resin, essentially cotton-reinforced Bakelite. It was often used in car engines for gear wheels used to provide a direct drive to the camshaft as it is flexible and quiet-running. One of the first luxury cars to use this material for its camshaft drive gears was the Maybach Zeppelin of 1928. The material is known under various other names such as Turbax, Resitex, Celeron and Textolit. In bar form it is also known as Cartatextiel and Ferrozell and in sheet form as Harex, Tufnol and Micarta.

<span class="mw-page-title-main">Rotary feeder</span>

Rotary feeders, also known as rotary airlocks or rotary valves, are commonly used in industrial and agricultural applications as a component in a bulk or specialty material handling system. Rotary feeders are primarily used for discharge of bulk solid material from hoppers/bins, receivers, and cyclones into a pressure or vacuum-driven pneumatic conveying system. Components of a rotary feeder include a rotor shaft, housing, head plates, and packing seals and bearings. Rotors have large vanes cast or welded on and are typically driven by small internal combustion engines or electric motors.

A thrust block, also known as a thrust box, is a specialised form of thrust bearing used in ships, to resist the thrust of the propeller shaft and transmit it to the hull.

<span class="mw-page-title-main">Albert Kingsbury</span> Engineer and inventor

Albert Kingsbury was an American engineer, inventor and entrepreneur. He was responsible for over fifty patents obtained between the years 1902 to 1930. Kingsbury is most famous for his hydrodynamic thrust bearing which uses a thin film of oil to support weights of up to 220 tons. This bearing extended the service life of many types of machinery during the early 20th century. It was primarily outfitted on Navy ships during World War I and World War II.

<span class="mw-page-title-main">Spiral groove bearing</span> Hydrodynamic bearings using spiral grooves to develop lubricant pressure

Spiral groove bearings are self-acting, or hydrodynamic bearings used to reduce friction and wear without the use of pressurized lubricants. They have this ability due to special patterns of grooves. Spiral groove bearings are self-acting because their own rotation builds up the pressure needed to separate the bearing surfaces. For this reason, they are also contactless bearings.

<span class="mw-page-title-main">Rotary union</span>

A rotary union is a union that allows for rotation of the united parts. It is thus a device that provides a seal between a stationary supply passage and a rotating part to permit the flow of a fluid into and/or out of the rotating part. Fluids typically used with rotary joints and rotating unions include various heat transfer media and fluid power media such as steam, water, thermal oil, hydraulic fluid, and coolants. A rotary union is sometimes referred to as a rotating union, rotary valve, swivel union,rotorseal, rotary couplings, rotary joint, rotating joints, hydraulic coupling, pneumatic rotary union, through bore rotary union, air rotary union, electrical rotary union, or vacuum rotary union

<span class="mw-page-title-main">Rim-driven thruster</span> Electric propulsion unit for ships

The rim-driven thruster, also known as rim-driven propulsor/propeller is a novel type of electric propulsion unit for ships. The concept was proposed by Kort around 1940, but only became commercially practical in the early 21st century due to advances in DC motor controller technology. As of 2017, commercial models of between 500 kW and 3 MW are available from manufacturers such as Rolls-Royce, Schottel, Brunvoll, Voith, Van der Velden, etc.

An underwater thruster is a configuration of marine propellers and hydraulic or electric motor built into or mounted to an underwater robot as a propulsion device. These give the robot movement and maneuverability against sea water resistance. The main difference between underwater thrusters and marine thrusters is the ability to work under heavy water pressure, sometime up to full ocean depth.

A composite bearing is a bearing made from a combination of materials such as a resin reinforced with fibre and this may also include friction reducing lubricants and ingredients.

References

  1. 1 2 "Stave type bearings for marine applications". Tufnol. Archived from the original on July 17, 2011.{{cite web}}: CS1 maint: unfit URL (link)
  2. ↑ "Guest Editorial: Back to the future for prop shaft bearings". Drydock Magazine.
  3. ↑ "Water-Lubricated Bearings and Shaft Sealing Systems". Duramax Marine.
  4. ↑ "Water-Lubricated Bearings and Shaft Sealing Systems".
  5. ↑ US 4149761,Telle, Byron J.,"Water lubricated stave bearing",published 1979-04-17, assigned to Johnson Rubber Co.
  6. ↑ "Duramax Marine Johnson Cutless bearings" . Retrieved 2015-12-01.
  7. ↑ "Propeller Shaft Bearings: MarineEngineDigest.com" . Retrieved 2011-10-25.
  8. ↑ "Vesconite Design Manual" (PDF).
  9. ↑ Tremayne, David (2005). Donald Campbell: The Man Behind the Mask. Bantam Books. ISBN   0-553-81511-3.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.