VESCONITE Marine Bearings and Bushings
Rudder and Stern Tube Bearings / Bushings

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What is Vesconite?
VESCONITE is a specialised thermoplastic made from internally lubricated polymers.  Proven since the 1960s, Vesconite is an exceptional plain bearing material.  It gives long life in applications where only the lowest wear rates can be allowed, even when the application is poorly lubricated and dirty.

Vesconite is ideal for many marine applications.  It is suited to both dry and immersed applications - in fact water is an excellent lubricant.

Vesconite is extensively used for rudder and stern tube bearings.  Vesconite's internal lubricants make it eminently suited to upper rudder bearing applications where there are long periods between greasing or no greasing at all, or where water lubrication cannot be ensured when operating with light ballasts.

The hundreds of vessels equipped with Vesconite during the last 15 years - ranging from pleasure boats to tankers - testify to the desirability of long life, low maintenance Vesconite in marine applications.

Why use Vesconite?
Vesconite combines the advantages of metallic and non-metallic bearings and bushes.

Vesconite is extremely versatile. It outperforms in most plain bearing applications, whether unlubricated, grease and oil lubricated, or water lubricated.

Long wear life
Vesconite gives up to 10 times the service life of phosphor bronze in poorly lubricated conditions.

Vesconite keeps size - no water swell

Vesconite does not swell. Vesconite is one of the most dimensionally stable synthetic materials available. Vesconite bearings may be machined to the correct clearances without fear of swelling. Clearances do not disappear. Vesconite gives you security! For most synthetic bearing materials, water swell is a major problem. With water swell, there is always a risk of seizure. To compensate, suppliers of materials which swell advise excessive clearances.	Click on figure to view detail
	Figure 1: Swell of synthetic bearing materials due to water.

Excessive clearances must be avoided for three reasons.

Firstly, they allow increased vibration.

Secondly, when machining an excessive clearance, one is machining away part of the wear life of the bearing - before installation!

Thirdly, and most negatively, the rate of wear of a sleeve bearing increases in proportion to the clearance.

The greater the clearance, the faster the bearing wears, which greatly shortens bearing life.

Vesconite remains hard

In the long term, humidity in the general environment leads to water absorption. Softening caused by humidity and immersed conditions has two major disadvantages for these materials.

Firstly, the drop in compression strength leads to creep. If the bearing is reasonably loaded, it will squeeze out, and no longer hold the shaft in its proper location.

Secondly, because the bearing surface is softer, its rate of wear increases dramatically, leading to a shorter bearing life.

This is why Vesconite is the marine bearing material of choice - it remains hard in moist and immersed conditions, keeps its compression strength and maintains its excellent long life wear characteristics.

Vesconite does not delaminate
Vesconite is a homogenous bearing material without any lamination reinforcement. The result is that delamination cannot take place with Vesconite, whereas it is a major problem for many laminated and composite products, for example laminated phenolics, laminated polyesters and thermosets.

What is delamination?
Delamination is the peeling off of layers of the bearing. It is not a slow, steady process like wear - instead whole layers of the bearing break off, causing uneven and excessive clearance.

How does delamination occur?
Laminated bearings are manufactured in layers, with a fibre or cloth reinforcement. As wear at the bearing surface occurs, water penetrates the exposed micro-channels that are formed by the cloth. Swelling occurs along these surfaces, causing weakness between the layers of the laminate. The result is that the surface layers of the bearing material start peeling off.

Avoid delamination problems by switching to Vesconite.

Vesconite has low friction, even in actual working conditions
Compared to most elastomers, rubbers, nylons and laminates, Vesconite has a low friction. And this remains the case even in the practical, tough conditions of the real working environment.

Many products are claimed to have a low friction, but often only in the laboratory when tested under lightly loaded conditions, and before the effects of softening caused by water. Vesconite keeps its low static and dynamic friction whether dry or wet, or lightly or heavily loaded.

Why is this important? Low friction for a rudder bearing means less bearing wear, as well as smoother operation and less wear to the whole steering gear.

The low static friction of Vesconite is especially beneficial to the low amplitude oscillating movements of rudders. With Vesconite every change of direction occurs smoothly, with a minimal power requirement and without any jerking.

Test this for yourself with Vesconite - its the best way to prove it. You will be delighted with the performance improvement compared to conventional materials.

SOS: Save Our Shafts
Vesconite saves your shafts. Because of its low friction, most users report greatly reduced wear rates on shafts and liners. In many applications, users have switched to Vesconite because of the reduced wear, increased life and savings obtained on their shafts, often a very expensive component.

The case study of the propeller shaft bearings of the Jackson pilot boat is an example of the low shaft wear rate.

If shaft wear is your problem, or you would like to extend your shaft life, contact us about options.

Vesconite does not corrode
Vesconite is not subject to electrolytic corrosion, a major problem with traditional metallic bearing materials. While corrosion of the bearing surfaces is not normally a problem for bronze and cutless bearings, it becomes a major practical problem when replacing a cutless or bronze bearing. Usually there is some corrosion between the outside of the bronze sleeve and the housing, which often makes removal of the old bearing exceptionally difficult.

Easy removal of Vesconite bearings
Vesconite bearings are easy to remove. Since no electrolytic corrosion occurs with Vesconite, they do not seize like metallic bearings.

Vesconite does not contain any reinforcement, and old Vesconite bearings are easily removed. This is often not the case for laminated bearings: workers often struggle for hours trying to cut, hammer or burn laminated bearings out of their housings.

Safety and health
Vesconite is a safe product. It does not contain asbestos or hazardous fibres. Nor does Vesconite contain any lead or hazardous substances.

Vesconite has passed a series of stringent health tests. It is fully approved for applications in direct contact with drinking water, both in cold and hot water.

Easy to machine
Compared to metallic, cutless, bronze or synthetic bearing materials, Vesconite is very easy and safe to machine on standard metalworking and wood working machinery.

With Vesconite the size you machine is the size you get, unlike elastomers which stress relieve and change size during machining.

There are no dust or health problems when machining Vesconite, whereas these can be problems with laminates as a result of the fibre reinforcement.

Low friction Vesconite keeps lathe tooling sharp hour after hour. This is another example of the long life, low wear properties of Vesconite. If machining a bearing blunts your tooling, think what it does to your shafts.

Vesconite versus white metal
Vesconite has a higher design load limit than white metal (babbitt), a higher fatigue strength and two to three times the wear life.

Chemical resistance
In addition to its unrivalled performance in water, Vesconite has a wide range chemical resistance, including resistance to many acids, organic chemicals and solvents, hydrocarbons (including gasoline), oils and fuels.

If you need a bearing for a problem chemical application, contact us - we can advise whether Vesconite is suitable, or whether we can offer another of our speciality bearing materials.

Classification Society Approvals.
Vesconite has been given approval by most of the ship classification societies, including:

American Bureau of Shipping
Biro Klasifikasi Indonesia
Bureau Veritas
China Classification Society
China Corporation Register of Shipping
Det Norske Veritas
Germanischer Lloyd
Korean Register of Shipping
Lloyd's Register
Nippon Kaiji Kyokai
Rina 

Field Trials of Vesconite Stern Tube Bushes
The long service life of Vesconite stern tube bushes is demonstrated by 15 years of experimental and survey results obtained from the RP Jackson, a harbour pilot cutter.

The RP Jackson sails in and off Durban harbour in waters with high concentrations of abrasive, suspended sand particles arising from propeller wash.

Superior wear figures of 1.5 to 3.0 mm (0.06 - 0.118") were obtained after each 5 year period of service.  These wear figures were remarkably low given the sandy harbour waters the Jackson operates in.

Vesconite Production Range

See also the Vesconite Production List

Vesconite is stocked in a wide range of sizes and shapes, and is machined at short notice to toleranced drawings.
Specialised parts may also be injection moulded.

Straight Bushings (Tubes) are stocked for shafts from 20 to 660 mm (0.8" to 26") diameter (housing diameters up to 750 mm (29.5")).  To save costs, bushings with diameters greater than 250 mm (10") can be supplied to the exact length required.

Ready-to-Fit stern tube and rudder bushes with water grooves are stocked for shafts from 25 to 60 mm (1" to 2.4") diameters for housings from 40 to 80 mm (1.5" to 3.2").  Outside diameters can be supplied to the nearest imperial size.

Staves are produced in lengths up to 3 metres (10').  Linings and machining of housings can be undertaken.

Flanged Bushes and Thrust Washers can be produced up to 715 mm (28") outside diameter.  Solid Rods from 20 to 160 mm (0.8" to 6.3") are stocked in 1 metre lengths.  Plates and Wear Strips are available in accurately machined thicknesses from 2 to 50 mm (0.08" to 2").

A wide range of new bushing sizes up to 750 mm (29.5") has been put into stock. 

Availability
Vesconite can be obtained directly from dedicated dealerships in many parts of the world.  Substantial stocks are maintained at VescoPlastics Sales and their Factory as well as in Singapore and China, Hong Kong,  Buenos Aires, Netherlands, Australia, New Zealand, United Kingdom and the United States of America ready to be air freighted anywhere in the world at short notice. 

Stave Bearings