www.vesconite.com Long life, low friction, no swell

VESCONITERudder andStern tube bearings

Design Manual

What is Vesconite 1

Why use Vesconite 2

Classification Society Approvals 4

Vesconite Product Range 6

Vesconite - Chemical Resistance 8

Vesconite - Typical Properties 9

Interference Press Fits 10

Clearance for Rudder Bearings 10

Clearance for Water Lubricated Stern Tube Bearings 11

Outside Diameter, Inside Diameter 11

Wall Thickness 12

Grooves for Water Lubricated Stern Tube Bearings 12

Grooves for Rudder Bearings 12

Water Grooves 13

Design Loading 13

Length to Diameter Ratio 13

Machining Vesconite 14

Installing and Securing Vesconite 16

Housings 17

Mechanical Securing and Adhesive Bonding 17

Fitting Staves 17

Shaft and Other Mating Surfaces 17

Pressure and Velocity Limits 18

Field Trials 19

Company Profile 20

Warranty and Liability 20

Enquiry Service IBC

Contents

1

Underwater or in humidconditions, Vesconite will notswell and seize which is a majorproblem with nylon bushes.Nor does Vesconite softenand wear in water like nylon. Vesconite's internal lubricantsmake it eminently suited toupper rudder bearing applica-tions where there are long

periods between greasing orno greasing at all, or wherewater lubrication cannot beensured when operating withlight ballasts. Since 1977 Vesconite has been proved and approved asa bearing material for marine applications. (See page 4)

What is Vesconite?VESCONITE is a specialised thermoplastic made frominternally lubricated polymers.It has been proven since thelate 1960s to be an exceptionalplain bearing material, givinglong life in applications whereonly the lowest rates of wearcan be accepted. Even whenconditions are dirty andunlubricated, Vesconite giveslong life together with lowmaintenance and low friction.

Vesconite - with very lowcoefficients of friction whetherdry or underwater, unlubricatedor lubricated - is ideal formany marine applications.It is suited to both dry andimmersed applications. In factwater is an excellent lubricantfor Vesconite.

For rudder and stern tubebearings, Vesconite has manyadvantages compared tonylon, elastomers, phenolic laminates, lignum vitae andphosphor bronze.

Vesconite is dimensionallystable, unlike nylon, someelastomeric materials andphenolic laminates.

2

Why Use Vesconite?Vesconite combines theadvantages of metallic andnon-metallic bearings andbushes.

Vesconite is extremelyversatile. It outperforms inmost plain bearingapplications, whetherunlubricated, grease and oillubricated, or waterlubricated.

Long wear lifeVesconite gives up to 10times the service life ofphosphor bronze in poorlylubricated conditions.

Vesconite keeps size -no water swellVesconite does not swell.Vesconite is one of the mostdimensionally stable syntheticmaterials available as shownin Figure 1. Vesconitebearings may be machined to

the correct clearanceswithout fear of swelling.Clearances do not disappear.Vesconite gives you security!

For most synthetic bearingmaterials, water swell is amajor problem. With waterswell, there is always a riskof seizure. To compensate,suppliers of materials whichswell advise excessiveclearances.

Excessive clearances mustbe avoided for three reasons.

Firstly, they allow increasedvibration.

Secondly, when machiningan excessive clearance, oneis machining away part ofthe wear life of the bearing -before installation!

Thirdly, and most negatively,the rate of wear of a sleevebearing increases inproportion to the clearance.

The greater the clearance, thefaster the bearing wears,which greatly shortensbearing life.

Vesconite remains hardIn a wet environment,Vesconite does not absorbmoisture nor does it soften.Vesconite remains hard, andkeeps its compressionstrength and excellentresistance to creep.

Many synthetic bearingmaterials, like those based onelastomers and nylons, softenand lose their compressionstrength in water. This isshown in Figure 2.

In the long term, humidity inthe general environment leadsto water absorption. Softeningcaused by humidity andimmersed conditions has twomajor disadvantages for thesematerials.

Figure 1: Swell of synthetic bearing materials due to water

3

Firstly, the drop in compressionstrength leads to creep. If thebearing is reasonably loaded, itwill squeeze out, and no longerhold the shaft in its properlocation. Secondly, because thebearing surface is softer, itsrate of wear increasesdramatically, leading to ashorter bearing life.This is why Vesconite is themarine bearing material ofchoice - it remains hard inmoist and immersedconditions, keeps itscompression strength andmaintains its excellent longlife wear characteristics.

Vesconite does notdelaminateVesconite is a homogenousbearing material without anylamination reinforcement. Theresult is that delaminationcannot take place with

Vesconite, whereas it is a majorproblem for many laminatedand composite products, forexample laminated phenolics,laminated polyesters andthermosets.

What is delamination?Delamination is the peeling offof layers of the bearing. It isnot a slow, steady process likewear - instead whole layers ofthe bearing break off, causinguneven and excessiveclearance.

How does delaminationoccur?Laminated bearings aremanufactured in layers, with afibre or cloth reinforcement. Aswear at the bearing surfaceoccurs, water penetrates theexposed micro-channels thatare formed by the cloth. Swelling occurs along thesesurfaces, causing weaknessbetween the layers of the

laminate. The result is that thesurface layers of the bearingmaterial start peeling off.

Avoid delamination problemsby switching to Vesconite.

Vesconite has lowfriction, even in actualworking conditionsCompared to mostelastomers, rubbers, nylonsand laminates, Vesconite hasa low friction. And thisremains the case even in thepractical, tough conditions ofthe real working environment.

Many products are claimed tohave a low friction, but oftenonly in the laboratory whentested under lightly loadedconditions, and before theeffects of softening caused bywater. Vesconite keeps its lowstatic and dynamic frictionwhether dry or wet, or lightlyor heavily loaded.

Figure 2: Vesconite maintains its compression strength whether wet or dry.

Stress and strain comparison after water absorptionVesconite keeps its compression strength in wet environments.Elastomers and nylons absorb moisture, leading to softening and loss ofcompression strength.

Visit vesconite.com to read more about the hundredsof vessels equipped with Vesconite during the last 25 years - ranging from pleasure boats to tankers -testifying to the desirability of long life, lowmaintenance Vesconite in marine applications.

Lloyd’sRegisterLloyd’sRegister

4

Classification Societies

Vesconite has approval from the world’s major shipping classificationsocieties, including:

American Bureau of ShippingBiro Klasifikasi IndonesiaBureau VeritasChina Classification SocietyChina Corporation Register of ShippingDet Norske VeritasGermanischer LloydKorean Register of ShippingLloyd’s RegisterNippon Kaiji KyokaiRINA

Why is this important? Lowfriction for a rudder bearingmeans less bearing wear, aswell as smoother operationand less wear to the wholesteering gear.

The low static friction ofVesconite is especiallybeneficial to the low amplitudeoscillating movements ofrudders. With Vesconite everychange of direction occurssmoothly, with a minimalpower requirement andwithout any jerking.

Test this for yourself withVesconite - its the best way toprove it. You will be delightedwith the performanceimprovement compared toconventional materials.

SOS: Save Our ShaftsVesconite saves your shafts.Because of its low friction,most users report greatlyreduced wear rates on shaftsand liners. In manyapplications, users haveswitched to Vesconitebecause of the reduced wear,increased life and savingsobtained on their shafts, oftena very expensive component.

The case study of thepropeller shaft bearings of theJackson pilot boat on page 19is an example of the low shaftwear rate.

If shaft wear is your problem,or you would like to extendyour shaft life, contact usabout options.

Vesconite does notcorrodeVesconite is not subject toelectrolytic corrosion, a majorproblem with traditionalmetallic bearing materials.While corrosion of the bearingsurfaces is not normally aproblem for bronze andcutless bearings, it becomesa major practical problem

when replacing a cutless orbronze bearing. Usually thereis some corrosion betweenthe outside of the bronzesleeve and the housing, whichoften makes removal of theold bearing exceptionallydifficult.

Easy removal ofVesconite bearingsVesconite bearings are easyto remove. Since noelectrolytic corrosion occurswith Vesconite, they do notseize like metallic bearings.

Vesconite does not containany reinforcement, and oldVesconite bearings are easilyremoved. This is often not thecase for laminated bearings:workers often struggle forhours trying to cut, hammer orburn laminated bearings outof their housings.

Safety and healthVesconite is a safe product. Itdoes not contain asbestos orhazardous fibres. Nor doesVesconite contain any lead orhazardous substances.

Vesconite has passed a seriesof stringent health tests. It isfully approved for applicationsin direct contact with drinkingwater, both in cold and hotwater.

Easy to machineCompared to metallic, cutless, bronze or syntheticbearing materials, Vesconiteis very easy and safe tomachine on standardmetalworking and woodworking machinery.

With Vesconite the size youmachine is the size you get,unlike elastomers whichstress relieve and change sizeduring machining.

There are no dust or healthproblems when machiningVesconite, whereas these can

be problems with laminatesas a result of the fibrereinforcement.

Low friction Vesconite keepslathe tooling sharp hour afterhour. This is another exampleof the long life, low wearproperties of Vesconite. Ifmachining a bearing bluntsyour tooling, think what itdoes to your shafts.

Vesconite versus white metalVesconite has a higher designload limit than white metal(babbitt), a higher fatiguestrength and two to threetimes the wear life.

Chemical resistanceIn addition to its unrivalledperformance in water,Vesconite has a wide rangechemical resistance, includingresistance to many acids,organic chemicals andsolvents, hydrocarbons(including gasoline), oils andfuels. (See page 8)

If you need a bearing for aproblem chemical application,contact us - we can advisewhether Vesconite is suitable,or whether we can offeranother of our specialitybearing materials.

5

www.vesconite.comfor quick and easy to useonline design calculators

VesconiteProduct Range

Vesconite is stocked in a widerange of sizes and shapes.

Vesconite can be obtaineddirectly from dedicateddealerships in many parts ofthe world or airfreighted withindays from the VescoPlastics’factory.

Vesconite is available atshort notice for specialmarine products, whethersemi-finished or finished totoleranced drawings.

Special shapes may also beinjection moulded inVesconite for cost effectiveOEM components.

Bearings (Tubes) Stocked in 1 metre (39”)lengths for shafts from 6 to650 mm diameter ( 1/4” to 26”).

Large diameter bearings (250 mm/10” and greater) arealso stocked in 1.5 and 3 metre (5’ and 10’) lengths.

For greater economy thesecan be supplied to the length

required, thus avoidingwastage.

Details of the full bearingstock range may beobtained from yourVesconite dealer or bycompleting the enquiry formon the inside back cover ofthis manual.

Ready-to-Fit strut and rudderbearings with water groovesare stocked for shafts from25mm (1”) to 50mm (2”)diameters and for housingsfrom 40mm (11/2”) to 70mm (23/4”).

Outside diameters can besupplied to the nearestimperial size.

Staves Vesconite staves for largerudder or stern tube bearingsare cut and milled from plate.

Machined staves areproduced in 1 metre (39”)lengths or as required up to 3metre (10’) lengths.

Ready-to-FitBearings

6

Linings Machining and lining ofsleeves and housings can beundertaken.

Solid rods Diameters from 8 to 160 mm(5/16” to 6”) are stocked in 1 metre (39”) lengths.

Longer lengths may beproduced upon request.

Thrust Washers Manufactured in diameters upto 715 mm (28”).

Plates andWear Strips

produced to requiredlengths. Standard platewidths are 200 mm (7 7/8”).

Some thicknesses are alsoavailable as plates 600 mm(231/2”) wide.

Available in accuratelymachined thicknesses from 3to 50 mm (1/8” to 2”). Platesfrom 3 to 10 mm (0.118” to0.394”) thickness are stockedin lengths up to 1000 mm(39”).

Plates from 12 to 50 mm(1/2” to 2”) thickness can be

VesconiteSuperclad Bearings

Vesconite Supercladtechnology adds greatversatility to the Vesconitestock range.

Many customers requirespecial bearing sizes at shortnotice. To meet this need, aSuperclad Vesconite bearingis produced.

A bearing with a suitableinside diameter is wound witha cloth membraneimpregnated with an epoxycompound until the desiredoutside diameter is obtained.

Left to cure overnight, thebearing is ready for machiningand despatch the next day.

The resulting Vesconitebearing is encased in areinforced Superclad jacket,giving an extremely strongfinal structure.

The high strength ofSuperclad on the outside iscombined with the goodbearing properties ofVesconite on the inside.

Vesconite Supercladtechnology can quickly andeconomically producebearings with practically anydesired wall thickness forshafts up to 675 mm (261/2”)diameter.

7

Vesconite - Chemical Resistance

Vesconite has a wide rangechemical resitance, includingresistance to many acids,organic chemicals andsolvents, hydrocarbons, oils and fuels, includinggasoline.

If you need a bearing for aproblem chemicalapplication, contact us - we can advise whetherVesconite is suitable,

or whether we can offer another of our speciality bearing materials.

5% Acetic acid

10% Acetic acid

Acetone

Aniline

Benzine

Bleaching lye

Brake fluid

Butane

Butyl acetate

10% Calcium chloride

Calcium hypochlorite

Carbon disulphide

Carbon tetrachloride

40% Chromic acid

10% Citric acid

Cottonseed oil

25% Detergents

Dibutyl phthalate

Diesel oil

Dioxane

Ethanol

Ether (diethyl-)

Ethyl acetate

Ethylene dichloride

Freon II

5% Formic acid

Gasoline

Glycerol (Glycerine)

Glycol

Grease

Heptane

Hexane

10% Hydrochloric acid

5% Hydrofluoric acid

30% Hydrogen peroxide

Kerosene

Methanol

Methyl ethyl ketone

Mineral oils

Motor oils

10% Nitric acid

100% Oleic acid

Olive oil

Paraffin

Perchloroethylene

Petrol

30% Phosphoric acid

85% conc Phosphoric acid

10% Potassium chloride

10% Potassium dichromate

1% Potassium hydroxide

10% Potassium permanganate

Silicone fluids

1% Soap solutions

10% Sodium bicarbonate

10% Sodium bisulphite

20% Sodium carbonate

10% Sodium chloride

1% Sodium hydroxide

10% Sodium hypochlorite

30% Sulphuric acid

Toluene

Transformer oil

Turpentine

Vaseline

Vegetable oils

Water

White spirit

Xylene

Vesconite has good resistance to the following solutions at ambient temperatures

8

Density / Specific gravity 1.38 g.ml-1 1.38

Melting point 260°C 500°F

Hardness (Shore D) 84 84

Tensile strength at yield (D638) 65 MPa 9,400 psi

Tensile strength at break 62 MPa 9,000 psi

Elongation at break 26% 26%

Tangent modulus of elasticity (D790) 3400 MPa 493,000 psi

Flexural yield strength 120 MPa 17,400 psi

Deflection temperature at 1.85 MPa/268 psi 93°C 200°F

Modulus of elasticity under compression 2290 MPa 332,000 psi

Compression strength at yield 92 MPa 13,300 psi

Shear strength 49 MPa 7,100 psi

Notched impact strength charpy (D256) 33 J.m-1 0.6 ft-lb/in

Notched impact strength IZOD 16 J.m-1 0.3 ft-lb/in

Thermal conductivity 0.3 W.K-1.m-1 2 Btu-in/ft2/hr/°F

Coefficient of linear thermal expansion 6x10-5mm.mm-1.°C-1 3.3x10-5 in/in/°F

Maximum moisture absorption 0.5% 0.5%in water at 20°C/68°F

Equilibrium moisture absorption in air 0.2% 0.2%(50% relative humidity, 23°C/73°F)

Dynamic unlubricated friction 0.12 - 0.20 0.12 - 0.20coefficient on steel

Dielectric strength 14 kV.mm-1 360 kV/in

Gamma ray resistance 50% loss of properties 100 Mrads 100 Mrads

Physical properties may be altered to some extent by processing conditions.

Vesconite - Typical Properties

9

Example: A rudder pintle has a diameter of 508mm (20”)Find the fitted minimum clearance?From Fig. 4 fitted running clearance is 0.96mm (0.038”)

Example: A rudder neck bearing is required for a housing of533 mm (21”). The bearing will be machined in a workshop withan ambient temperature of 20°C (70°F). The bearing may operate in temperatures as low as -20°C (-4°F).Specify the press fit required.Using -20°C (-4°F) line in Figure 3, press fit = 1.86 mm (0.073”)

0.104

0.096

0.088

0.080

0.072

0.064

0.056

0.048

0.040

0.032

0.024

0.016

0.008

0

2.6

2.4

2.2

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0.0

0 4 8 12 16 20 24 28 32

0 100 200 300 400 500 600 700 800

Housing diameter (inches)

Housing diameter (mm)

-20°C: 0.05mm + 0.0034 (Housing diameter)-4°F: 0.002” + 0.0034 (Housing diameter)

0°C: 0.05mm + 0.002 (Housing diameter)32°F: 0.002” + 0.002 (Housing diameter)

Pre

ss fi

t (m

m)

Pre

ss fi

t (in

ches

)

10

Designing Bearings

InterferencePress FitsInterference press fits are themost common method forsecuring Vesconite bearings.

The press fits recommendedfor most applications may beread off Figure 3. The graphassumes a bearing ambienttemperature of 20°C (70°F)when it is machined.

Choose the press fit requiredfor the minimum operatingtemperature of the bearing.

If a lower operatingtemperature is anticipated,contact your authorisedVesconite distributor.

Clearance forRudder Bearings The recommended runningclearances for rudders afterfitting in well aligned housingsunder normal conditions aregiven in Figure 4.

No extra clearance is neededto allow for water absorptionbefore entering service.Vesconite does not absorbwater to any appreciableextent, unlike many othersynthetic materials whichswell as they absorb water.

0.056

0.048

0.040

0.032

0.024

0.016

0.008

0

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

0 4 8 12 16 20 24 28 32

0 100 200 300 400 500 600 700 800

Rudder shaft diameter (inches)

Rudder shaft diameter (mm)

0.2mm + 0.0015 (Rudder shaft dia. in mm)0.008” + 0.0015 (Rudder shaft dia. in inches)

Fitt

ed c

lear

ance

(mm

)

Fitt

ed c

lear

ance

(inc

hes)

Figure 3: Press fits for rudder and stern tube bearings

Figure 4: Fitted running clearance for rudder bearings

Example: For a water lubricated stern tube bearing used for a356 mm (14”) propeller shaft, find the fitted minimum clearance.From Figure 5, the required running clearance after fittingis 0.91 mm (0.036”).

11

Designing Bearings

Clearance for Water Lubricated Stern TubeBearingsThe recommended fittedrunning clearance for waterlubricated stern tube and strut bearings in well alignedhousings is obtained fromFigure 5.

0.072

0.064

0.056

0.048

0.040

0.032

0.024

0.016

0.008

0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

0 4 8 12 16 20 24 28 32

0 100 200 300 400 500 600 700 800

Propeller shaft diameter (inches)

Propeller shaft diameter (mm)

0.2mm + 0.002 (Propeller shaft dia. in mm)0.008” + 0.002 (Propeller shaft dia. in inches)

Fitt

ed c

lear

ance

(mm

)

Fitt

ed c

lear

ance

(inc

hes)

Figure 5: Fitted running clearance for water lubricated stern tube bearings

Outside DiameterThe bearing outside diameteris obtained by adding thepress fit to the maximumdiameter of the housing.

Inside DiameterThe free standing bearinginside diameter is obtained byadding the maximum shaftdiameter, the press fit multiplied by housing diameter ,

shaft diameterand the running clearance.

When press fitted, the bearinginside diameter is reduced byan amount somewhat greaterthan the press fit. Hence thepress fit is multiplied by housing diameter .

shaft diameter

This is called bore closure.

ID = shaft dia. + running clearance + ( press fit x )housing dia.shaft dia.

OD = housing diameter + press fit

Lead-in chamfer

Bearingoutsidediameter

Interference

Housingdiameter

Runningclearance

Wallthickness

Bearinginsidediameter

Shaftdiameter

Example: A water lubricated stern tube bearing fits into a 254 mm (10”) housing. The stern tube is designed to carry a 203.2 mm (8”) shaft. The bearing will be machined in a workshop with a temperature of 20°C (70°F).From Figure 3, the bearing requires a press fit of 0.56 mm (0.022”). Thus outside diameter = 254 + 0.56 mm [10” + 0.022”]

= 254.56 mm [10.022”]

To find the inside diameter we require the clearance.

From Figure 5 the running clearance is 0.6 mm [0.024”]Thus inside diameter = 203.2 + 0.56 x 254 + 0.6 mm

203.2= 204.5 mm

[ 8” + 0.022” x 10” + 0.024” = 8.052” ] 8”

Wall thickness = 0.5 (254.56 - 204.5) = 25.03 mm

[ 0.5 (10.022” - 8.052”) = 0.985”]

12

Wall ThicknessWhen machining, it is best to specify and control thebearing outside diameter and wall thickness.This is because workshoptemperature changes can

cause expansion andcontraction of up to 0.1%.

For example a 10°C (18°F)temperature change on a 500 mm (20”) diameterbearing will result in adiameter change of 0.3 mm

(12 thousandths) on a freestanding bearing.

If the wall thickness iscontrolled, diameter changeswill not affect the runningclearance once the bearinghas been press fitted.

Calculate the wall thickness as follows: Wall thickness = 0.5 [ OD - ID ]

Grooves for Rudder Bearings Generally Vesconite rudderbearings do not need watercirculation grooves. Vesconiteis also suited to unlubricated

operation when the movementis slow or intermittent which isthe case in most rudderapplications.

Initial and occasional greasingof Vesconite rudder bearings isadvantageous as it increases

bearing life, and grooves maybe provided for this purpose.

If grooves are machined intorudder bearings, groove depthshould not exceed one third ofthe Vesconite wall thickness.

Grooves for Water Lubricated Stern Tube BearingsTable 1 gives details of thewater grooves and flow ratesrecommended for waterlubricated bearings.

Do not grease waterlubricated Vesconite sterntube bearings. Grease may

block the water grooves andinterfere with water flow.

If more than one bearing isused, radial recesses aroundthe inner circumferenceswhere the bearings join mustbe provided to ensure waterflow even if the water groovesare not aligned.

A positive pumped flow ofengine cooling water to the

inboard end of the bearings isrecommended to preventabrasive particles entering thebearings, especially whenoperating in sandy conditionsor on rivers.

If engine cooling water is used,the water temperature shouldnot exceed 55°C (130°F) toavoid possible hydrolyticdegradation of Vesconite overa long period of time.

Designing Bearings

Example: A 500 mm (20”)long bearing with an internaldiameter of 400 mm (16”)can support a load of 50 cm x 40 cm x 300 kg.cm-2

[ 20” x 16” x 4,400psi ]= 600 000 kgs [1,408,000lbs ],that is 600 metric tons.

Shaft diameter No. of *Angle Groove width Groove depth Waterflow rategrooves between

mm inches grooves mm inches mm inches ll min-1 gal/min

60-79 2-3 7 45° 7 0.25 4 0.15 12 3.0

80-119 3-5 7 45° 9 0.30 5 0.20 18 4.5

120-159 5-6 7 45° 10 0.35 6 0.25 24 6.0

160-199 6-8 7 45° 12 0.40 7 0.30 30 8.0

200-249 8-10 7 45° 12 0.40 8 0.30 38 10.0

250-299 10-12 7 45° 14 0.50 8 0.30 45 12.0

300-349 12-14 8 40° 15 0.50 8 0.30 53 14.0

350-399 14-16 8 40° 15 0.50 8 0.30 60 16.0

400-499 16-20 9 36° 15 0.50 9 0.35 75 20.0

500-599 20-24 10 33° 18 0.50 9 0.40 90 24.0

600-699 24-28 11 30° 18 0.50 9 0.40 105 28.0

700-800 28-32 12 27° 18 0.50 9 0.40 120 32.0

13

Table 1: Groove sizes and flow rates for water lubricated stern tube bearings

‘UV’ groove designand recess if morethan one bearing is used

* It is recommended that no groove be located in the 6 o’clock position.

Designing Bearings

Design Loading

Length to DiameterRatio of Stern TubeBearings

Traditionally, water lubricatedstern tube bearings have beendesigned with a bearing lengthequal to four times the shaftdiameter. Because of the high

load capabilities of Vesconite,this bearing surface is morethan adequate. In manyapplications, shorter lengthbearings may be used.

Vesconite is a high compressionstrength, low creep material.The compression strength ofVesconite at yield is over 90MPa (13,000 psi). This allowsfor static design loads of up to30 MPa (300 kg.cm-2) (4,400 psi)provided the bearing issupported within a rigidhousing.

The ‘UV’ groove design witha round groove base and a

chamfered edge isrecommended as it maintainsa better hydrodynamic waterfilm. Groove depth should notexceed half the Vesconite wallthickness. ‘UV’ groove

14

Vesconite XL bearings areeasily machined on standardlathes if proper support isprovided to preventdeformation and cracking.

When machining a largebearing, the machinist hasmany options, depending onthe diameter and length ofthe bearing and the lathe orboring mill available.

By taking the followingimportant precaution, themachinist will find Vesconitebearings a pleasure tomachine:

When chucking the bearing,always use an insidesupport disc machinedsize-for-size to the bearinginside diameter to preventpossible cracking.Machine the support from asteel plate, disc or washer,25 - 35 mm (1 - 11/2") thick.

Do not clamp Vesconite like ametal, but clamp gently andwith care to avoid distortion.

Machining Vesconite

1Align and face one end of the bearing square. (A) This helps with alignmentlater. Use the internal support disc machined to size to prevent distortion and cracking.

2Swop bearing around, align and face the other end. (B)Again use the disc to support the inside diameter.

5Switch bearing around to part to length.A new disc machined size-to-size with the final bearing inside diameter will be required for support.

3Machine the outsidediameter of the bearing,again with the support disc in place.

4Machine the insidediameter, again with thesupport disc in place.

• When taking rough cuts,measure wall thickness asa check on accuracy andovality.

• If more than 15mm (3/4")has to be removed fromeither the outside or insidediameters of the bearing,first semi-finish both theinside and the outsidediameters to approximately5mm (1/4") oversize.

• When machining largebearings ensure that thefree end of the bearing issuitably supported.

For best internet supportand online design calculatorswww.vesconite.com

Larger diametersupport disc,machined size-to-size withfinal bearinginside diameter.

Support disc,machined tosize.

B A

A B

A B

B A

A B

Outside diameter tolerance Wall thickness tolerance% of outside diameter % of wall thickness

+0.2% +0.0%

-0.0% -0.5%

Machining TolerancesThe following are acceptabletolerances for the bearingoutside diameter and wallthickness:

Top rake0° - 5°

Front clearance 5° - 11°

200 mm300 mm400 mm500 mm600 mm700 mm

8”12”16”20”24”28”

Machining Grooves onCentre Lathes

Machining Vesconite

Use a tool up to the width ofthe groove required in aboring bar. Lock the chuckinto position.

Move the tool through thebearing using the hand wheel

or rapid advance taking a cutup to 1.5 mm (1/16”) maximumat a time until the requiredgroove depth is obtained.

Cutting SpeedsUp to 300m (1000’) per minute

Cutting FeedsRough: 0.5 - 0.7mm (0.020 - 0.030”) per revolution

Finish: 0.3 - 0.4mm (0.012 - 0.016”) per revolution

Turning Speed Guidelines: Bearing outside diameter RPM

35030020015010070

Tool Cutting Angles

15

Cutting ToolsUse sharp high speed toolsor tungsten carbide tips with high clearances andpositive rake angles. Rough cuts up to 5 mm (1/4") deep may be taken, with a finishing cut of at least 1 mm (1/32").

Allow the bearing to cool before taking final cuts.

Side rake 5° - 11°

16

Freeze fitting is the easiestway to install Vesconitebearings. Dry ice is an idealagent but liquid nitrogen canbe used if dry ice is notavailable.

Using Dry IceVesconite has a thermalexpansion coefficient of 6 x10-5 mm/mm/°C (3.3 x 10-5

in/in/°F).

Cooling in dry ice for two tothree hours reduces bearingtemperatures by 40 to 60°C(70 to 100°F). This results in ashrinkage of 1,2 mm (0.05”)on a 500 mm (20”) diameterbearing.

Good ventilation must beused in confined spaces toavoid possible lack of air.

Using Liquid NitrogenUse an insulated container asshown below. The containermay be any suitably sizedmetal drum.

To insulate, simply wraparound with glass or rock wool,or several layers of corrugatedcardboard, or bubble wrap.These may be held in place bytape, wire or strapping.

Place the bearing on woodenblocks or bricks to raise it 150 mm (6”) above the bottomof the container. Do not placethe bearing directly onto thefloor of the container.

Place a loose fitting lid on topof the container. If the lid ismade from chipboard orplywood 18 to 25 mm thick(0.75” to 1”), it will act as aninsulator as well.

Slowly pour liquid nitrogen intothe bottom of the container -about 50 mm (2”) deep.

Only sufficient liquid nitrogento cover the bottom of the

container is needed.

It is important to ensure thatthe liquid nitrogen does notcome into direct contactwith the Vesconite bearing.Allow the bearing to cool forapproximately 1 to 11/2 hourswhich should be enough toshrink it sufficiently for asliding fit.

Measure the top outsidediameter with a vernier toensure that sufficient shrinkagehas occurred before removingthe bearing from the container.

Use nitrogen only in wellventilated areas. Take care inhandling and adhere to thegeneral safety rules for liquidnitrogen as it can causesevere burns. Consult yoursupplier of liquid nitrogen fordetailed precautions. Safetyvisors and protective clothingshould be used.

Installing and Securing Vesconite Bearings

Vesconite bearingpacked in a containerwith dry ice.

Vesconite bearingpacked in a container supported bywooden blocks100-150 mm(4-6”) high.

Insulationmaterial

Lid

Liquidnitrogen upto 50mmdeep

Ensure that liquid nitrogen does not come intodirect contact with Vesconite bearing.

17

Housings While Vesconite is a fairly rigidmaterial, it will generallyconform to the size and shapeof the housing. Therefore out-of-round or out-of-line

housings should be avoided,unless the housing is maderound or in-line throughmachining.

MechanicalSecuring

Adhesive Bonding

Fitting Staves

Installing and Securing Vesconite Bearings

As a standard safetyprecaution, bearings shouldalways be secured usingconventional mechanical meanssuch as keeper rings. Grubscrews may be used on smallbearings.

Mechanical securing to preventpossible rotation and endkeeper rings are especiallyimportant for bearings that maybe used in sub-zero conditions.

If desired, anaerobicadhesives such as Loctite 603 or 648 retainingcompound may be used.Adhesive bonding isrecommended when usingsliding fits.

Machine a lead in chamfer of15° to 35° on the leadingedge of the bearing. Prime

initially with Loctite Primer Tand allow to dry.

Loctite 603 or 648 (former forsmaller gaps and the latter forlarger gaps) should be appliedto both the Vesconite bearingand metal housing surfaces.The bearing should bepressed into place andexcess adhesive wiped off.

Shaft and OtherMating Surfaces

Metal mating surfaces mustbe suited to the wearconditions encountered, forexample when operating insandy conditions. Hard shaftsurfaces ensure longer shaftand bearing life.

Hardchrome plated surfaces,seawater corrosion resistantstainless steel and admiraltyand gunmetal bronze linersare generally satisfactory asmating surfaces forVesconite.

Carbon steel and hardenedsteel shafts may be used asmating surfaces provided thatthey do not corrode under theconditions of use. A good finish of the order of0.5 micrometre Ra (20 micro-inches Ra) should be providedon shaft surfaces.Rough surface finishes andcorroded and scored shaftswill cause wear of Vesconitebearings and should beavoided.

Fitting of Vesconite staves isfacilitated by cooling thestaves in dry ice for 3 hoursbefore fitting.

Grub screw

Edge wellchamfered

Keeperplate

18

Pressure x Velocity(PV) Limits

All bearing materials havelimits in their ability to sustaina given loading at a particularspeed. This is known as thepressure x velocity limit or PVlimit.

Apart from pressure andvelocity, the PV limit ofVesconite depends uponoperating conditions. Themost significant factors in

operation are whether frictionis reduced through water or oillubrication, and whether heatremoval occurs either throughcirculating water or oil.

The recommended PV limitsfor Vesconite are given inTable 2. If your applicationhas PV values higher thanthose shown, consult yourdealer or the manufacturer.

PV limit

Operating condition MPa.m.min-1 psi-ft/min

Dry - no lubrication 5 2,500

Greased on assembly 10 5,000

Lubrication at regular intervals 20 10,000

Circulating oil lubrication 40 20,000

Circulating water lubrication 200 100,000

Table 2: Recommended Vesconite PV limits

Photograph: Safmarine

19

Field Trials of Vesconite Stern Tube Bearings

The very long service life ofVesconite stern tube bearingsis demonstrated by 25 years ofexperimental and survey resultsobtained from the RP Jackson,a harbour pilot cutter.

The RP Jackson has two 145 mm (5.7”) propeller shaftsheld by A frames with bearings550 mm (21.6”) long.

The RP Jackson sails in andoff Durban harbour under fairlysevere conditions. Thesewaters invariably containrelatively high concentrationsof abrasive, suspended sandparticles arising mainly frompropeller wash.

Superior wear figures wereobtained. Strut bearing wearof between 1.5 and 3.0 mm(60 and 120 thousandths) wasmeasured after each 5 yearperiod of service, equivalentto 0.4 mm (20 thousandths)wear per year.

The observed wear figureswere remarkably low given the sandy harbour waters theRP Jackson operates in.

An advantage of Vesconitebearings confirmed in the RP Jackson trials was that the wear on the propellershaft lining was reducedsubstantially.

The RP Jackson, operating on Vesconite bearings for over 25 years.

2220

Company Profile

Vesconite is produced in whatis probably the largest factoryof its kind in the world,dedicated to the development,production and application of

internally lubricatedthermoplastic bearingmaterials.

VescoPlastics - the developersand manufacturers ofVesconite - have beeninvolved in the production ofbearing materials, anti-wear

and anti-friction processes, aswell as precision engineeringsince the 1950’s. It is acompany with a long traditionof developing products andtechniques for problem solvingwhere quality and service arethe chief concerns.

Limited Warrantyand Limitation ofLiability

1 This design manual isbased upon many years

of experience ofVescoPlastics (the Company)in manufacturing andinstalling Vesconite.

Experience shows that no twoapplications are the same inevery detail so the Companyencourages that every

application be treated asindividual and unique.

This information is offered ingood faith as part of our clientservice, but favourable resultscannot be guaranteed. Thismanual is intended for use bypersons with technical skill, attheir discretion and risk. Thepurchaser must determine thesuitability of the goods fortheir intended purpose.

2 The Company reservesthe right to change or

amend any recommendationor specification without notice.

3 Goods are supplied onthe express condition

that the Company’s liability islimited to the replacement ofdefective goods or materials.

4 The Company does nothold itself responsible

for any damage, incidental orconsequential loss suffered asa result of the use of goodssupplied.

5 Acceptance of goodswill be held to imply

agreement to the aboveconditions.

IBC

Enquiry ServiceYou will be surprised to learn how competitively priced Vesconite bearings are. For a free quote, fax the following details to Vesco Plastics Sales (+27 11) 616 2222 or

(+27 11) 615 3810.

Bearing Application

Rudder/Pintle bearings Other (specify)........................

Stern tube/Strut/V-bracket ...............................................(water lubricated)

Dimensions mm’s inches

Shaft diameter.................................................

Housing diameter............................................

Bearing length ................................................

Customer Details

Enquiry from .........................................................................................................

Address ................................................................................................................

..............................................................................................................................

Country ............................................... Postal code ............................................

Telephone ........................................... Fax..........................................................

E-mail.................................................. Website...................................................

Visit www.vesconite.comfor information on Vesconite applications in numerous industries including marine, pumps, water treatment, sewage, fish farming, hydro-electric, mineral processing.

Order Design Manuals online or use our Marine Design-a-Bearing calculator program for instant answers to your design questions.

P O Box 40647, Cleveland, 2022 South AfricaTel (+27 11) 616-1111 or 616-4444Fax (+27 11) 616-2222 or 615-3810e-mail: vesconite@vesconite.com

www.vesconite.com

ChileT: +56 2 570 3855

GermanyT: +49 443 1892 3899

BrasilTOLL FREE0800 891 87 16

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United KingdomTOLL FREE0800 731 97 45T: 020 323 990 44F: +44 207 681 34 44

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United ArabEmiratesTOLL FREE800 027 01 03

USATOLL FREE (7 to 5 ET)1 866 635 75 96T: (713) 574 7255F: (212) 937 31 84

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Hong KongTOLL FREE800 930 211

NetherlandsTOLL FREE0 8000 223 805

New ZealandTOLL FREE0800 450 878

SingaporeVesco Plastics SEAT: +65 6 481 87 28F: +65 6 481 69 28

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IrelandTOLL FREE1 800 552 711

Vesconite bushings worldwide.Super large, super quick.

Any size possible.