Rothe Erde wire-race bearing. - · PDF fileRothe Erde wire-race bearing allows rapid and...

Rothe Erde wire-race bearing.

Rothe ErdeA ThyssenKruppTechnilogies

company

TK

www.bergab.ru Берг АБ [email protected] Тел. (495)-228-06-21, факс (495) 223-3071


Rothe Erde wire-race bearings.

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Index.

4 Global success with quality bearings and rings

5 Rothe Erde wire-race bearings

6 Rothe Erde aluminium alloy wire-race bearings

8 Bearing stresses

9 Design features

10 Variety of combinations for purpose designed bearings

12 Bearing types

14 Quality Management

16 Rothe Erde wire-race bearings in space systems

18 Sketches and notes

3



Global success with quality bearings and rings.

Our production programmeincludes ball and roller bearingslewing rings, wire-racebearings, turntables, andseamless-rolled steel and non-ferrous metal rings.

With its large-diameter anti-friction bearing programme,Rothe Erde has gained a strongglobal market position.Rothe Erde bearings are

produced in Germany as wellas by our subsidiaries in GreatBritain, Italy, Spain, the UnitedStates, Japan, Brazil andChina. Furthermore, we haveestablished sales organisationsand agencies in all majorindustrial countries.The Rothe Erde ring programmealso occupies a top-rankingposition in the internationalmarketplace.

Our domestic and internationalproduction facilities are unitedin their serious commitment toquality. In all our activities fromapplications consulting anddesign engineering to produc-tion and extensive customerservice, we are working toDIN EN ISO 9001.

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Rothe Erde wire-race bearingsare the product of dedicatedresearch and development.The typical feature of our wire-race bearings are the high-strength races for the rollingelements. A wire-race bearingsystem allows structural andmaterial combinations as wellas cross sections which are outof reach of any conventionalantifriction bearing.

Dimensions, cross sectionsand the ring material of the

bearings can be optimallymatched to all applicationrequirements. Depending ontheir purpose, Rothe Erde wire-race bearings can be ballbearings, roller bearings or acombination design.

Rothe Erde wire-race bearingsextend the range of applicati-ons for open-centre large-diameter bearings. They offerdecisive advantages overconventional surface-hardenedbearing designs like high

running accuracy, low anduniform torque resistance evenin a distorted condition,resistance to corrosion andlow-weight aluminium alloybearing rings.

Our bearing programmeranges from diameters assmall as 200 mm, e.g. formedical therapy equipment,to diameters of up to 14 m.



The principle of the wire-racebearing is that it allows materialcombinations which are notpossible in any other anti-friction bearing. As thesurrounding bearing rings arenot directly exposed to rollingfriction, they do not have to bemade from steel but canconsist of non-ferrous metals,cast iron or synthetic materials.Rothe Erde wire-race bearingswith alu-minium rings havegained particular importance.The same load carryingcapacity as that of comparablesteel bearings is achieved byan aluminium alloy of highmechanical strength. Thesurrounding rings preferablyconsist of the aluminium alloyAlZnMgCu 0.5 (Fig. 1).Compared to steel bearings ofidentical cross sections,aluminium wire-race bearingsweigh approx. 60% less.

Tests at renowned institutes oftechnology as well as our ownR&D work have demonstratedthat the high mechanicalstrength of this wrought alu-minium alloy also allows todirectly cut the gear into one ofthe bearing rings.

By using appropriate materialsfor the rolling elements andraces, a aluminium alloy wire-race bearing can be madecorrosion-proof and main-tenance-free. The corrosionbehaviour of aluminium bearingrings can be further improvedto resist the effects of saltwater by anodising or hard-coating.

Fig. 1:Aluminium wire-race bearing

Rothe Erde aluminium alloy wire-race bearings.

This aluminium wire-race

bearing weighs

249 kg

61.2 % we

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Weight comparison between analuminium bear-ing and a steel bearingof identical size with an outer diameterof 2.200 mm

This steel bearing of indentical

cross section weighs

641 kg

eight saved

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Aluminium alloy

Property Unit Al Zn Mg Cu 0.5DIN 1725 Bl. 1

Weigth ρ g/cm3 2.80

Material condition temper hardened

Tensile strength Rm N/mm2 490 min.

Yield point Rp 0,2 N/mm2 440 min.

Brinell hardness HB 10 approx. 150

Young’s modulus E N/mm2 approx. 71000

Expansion coefficient α 10-6/grd 21.6 – 23.6

Apart from the weight savingsalready mentioned, aluminiumalloy wire-race bearings areparticularly advantageous inapplications where the bearingis required to withstand shockloads and travelling vibrations.Due to the elastic deformationof the aluminium, which isabout three times that of steel,

and the additional elastic defor-mation between races and racebeds, shock loads are ab-sorbed much more smoothly,so that brinelling and striationof the raceway can be largelyprevented.

The high elasticity of thewrought aluminium alloy

characterised by a low Young’smodulus causes the elongationdifferential to be fully absorbedby the wire-race bearing.



Fr

Fr

Fa

M

M

Fa

Fa

b

a

M

Fr

FaFa

M

M

Bearing stresses.

Fig. 2:Double-row inclined axiswire-race roller bearing

Fig. 3:Axial forces and tiltingmoments acting as a cylin-drical surface and radialforces acting in the bearingplane

Fig. 4:Axial forces, radial forces and tiltingmoments acting on awire-race bearing

Structures involving large-diameter antifriction bearingsare preferably fitted withbearing types capable of with-standing all of the occurringloads. These antifrictionbearings must transmit all threeload components satisfactorily.

Due to the diagonal arrange-ment of their 3 or 4 races,4-point ball wire-race bearings,cross-roller wire-race bearings,and double-row oblique wire-race roller bearings (Fig. 2) arecapable of withstanding allaxial and radial forces even ifthese occur eccentrically or asshock loads. The axial forces

(Fa) and tilting moments (M)are acting as a cylindricalsur-face, while the radial forces(Fr) are acting on the rows ofrolling elements in the bearingplane (Fig. 3). Hereby, thetilting moments (M) which canbe generated either byeccentrical axial forces or byradial forces outside thebearing plane, are transformedinto reciprocally acting axialforces (Fig. 4).

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Design features.

Fig. 5:Double-row inclined axis wire-raceroller bearing. Internal gearing onthe split outer ring. Section throughthe fastening holes.

Fig. 6:Cross section of a double-row inclined axis wire-race roller bearing.Section through the retaining bolts.

Fig. 7:Races with cylindrical roller

Fig. 8:Plastic segmental cage for 5cylin-drical rollers

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7 8

The Rothe Erde wire-racebearing is a compositestructure consisting of bearingrings and races, rollingelements and spacers (Fig. 2).Contrary to conventional anti-friction bearing designs, therolling process does not occurdirectly between rollingelements and hardened bear-ing rings, but between rollingelements and the racesimbedded in the surroundingbearing rings.

The small cross section of theraces compared to the bearingrings allows the use of high-alloyed special steels with uni-

form hardness over the entirecross section. The possiblechoices include alloys with highcorrosion resistance – a usefulproperty for many applications,and materials with low magne-tic signitures.

Apart from steel, the bearingrings themselves can be pro-duced from materials meetingspecific requirements, such asbronze, cast iron, plastic oraluminium. Aluminium alloyswould, for instance, be chosenif high corrosion resistance,low weight and low-mainte-nance are required.

The composite structure of theRothe Erde wire-race bearingallows rapid and low-costrepair as only the races needto be replaced.

The service life of a bearingdepends on the life of its race-way. The easy replaceability ofthe races makes it possible torestore a bearing to as-good-as-new condition at low cost.

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Variety of combinations forpurpose designed bearings.

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Bearing rings● Engineering or heat treated

steels for standard bearingdesigns.

● Acid-proof special steels forcorrosion-resistant steelbearings.

● Heat-resistant special steelsfor bearings subjected tohigh temperatures.

● Steels with high impactstrength at low temperaturesfor bearings subjected tovery low temperatures.

● Non-ferrous metals, inparticular from aluminiumalloy AlZnMgCu 0.5, forlight-weight bearings.

Geared bearing rings● Hardened and tempered

steels, normalised, for bea-rings having to withstandnormal stresses.

● Hardened and temperedsteels or hardened, tem-pered and gas-nitridedsteels for bearings having towithstand high stresses.

● Aluminium alloys and othernon-ferrous metals.

Races● Hard-drawn spring steels.● Hardened special-grade

steels.● Corrosion-resistant materials.



Fig. 9:Seals

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Rolling elements● Antifriction bearing steel,

e.g. 100 Cr 6● Corrosion-resistant anti-

friction bearing steel, e.g.X 45 Cr 13

Rolling element cages● Synthetics● Bronze● Steel

Shims● Thin, corrosion-resistant

steel plates of variousthicknesses for bearing clearance adjustment

Retaining bolts● Grade 8.8 or 10.9 steel

depending on bearingstresses

● Special steels depending onspecific application require-ments Heli-Coil inserts

Heli-Coil inserts● Chromium-nickel steel, e.g.

for aluminium alloy bearingrings

SealsThe raceway systems in RotheErde wire-race bearings areprotected from environmentalinfluences by lip seals or laby-rinths.

The direct insertion of the ra-dially or axially arranged sealsinto the bear-ing rings assuresespecially advantageousstructural dimensions of theentire sealing system (Fig. 9).If particularly stringent sealingrequirements must be met,Rothe Erde wire-race bearingscan be completely sealed offeither by spring lip seals, byjoint seals and, if necessary, by additional O-ring seals.

Preloading is possible bymeans of the tension springbehind the sealing lip, so thatsealing effect and torqueresistance can be optimallyadjusted.

These seals protect the interiorof the bearing against theingress of dust, gases andliquids from the outside andare rated for a pressure ofseveral meters water columnand up to 5 mbar air over-pressure of the ABC positiveventilation inside the vehicle.



Design types and propertiesRothe Erde wire-race bearingscombine the advantages ofconventional ball and rollerbearings with the advantagesoffered by the wire-race bea-ring system itself:● Transmission of all load com-

ponents by a single self-retaining bearing unit. Highrunning accuracy, high staticand dynamic load carryingcapacity.

● The overall centre of gravityof the loads may be locatedfar outside the bearing dia-meter.

● Low and uniform torque resi-stance over the entire loadarea, even under distortion.

● The open centre permits thearrangement and passage ofother structural elements,e.g. drives, access openings,and others.

● The gear can be cut directlyinto one of the bearing rings.

● Aluminium bearings offerapprox. 60 % weight savingover comparable steel bea-rings at identical load carry-ing capacity.

● Demands for maintenance-free, corrosion-resistant andantimagnetic bearings canbe met as well.

Rothe Erde wire-race bearingscan be supplied in combinationdesigns which are technicallyand economically tailored toany requirements.

Balls or rollers can be used asrolling elements, depending onthe loads the bearing is sub-jected to. The direction ofapplied forces determines thebasic design as an axial orradial wire-race bearing or acombination thereof.

Basic bearing typesFig.10The single-row radial 4-pointwire-race ball bearing issuitable for the unrestrictedtransmission of all loadcomponents.

Fig. 11The single-row axial 4-pointwire-race ball bearing transmitsprimarily axial forces. Its radialload capacity depends, amongstother factors, on the amount ofaxial load occurring.

Fig. 12The single-row axial wire-raceroller bearing transmits exclu-sively axial forces. Radialsupport must be assured bymeans of an additional bea-ring.

Fig. 13The single-row radial wire-raceroller bearing is used for purelyradial forces, or if additionalaxial forces are transmitted byan other bearing.

Fig.14The inclined axis wire-race rol-ler bearing is only used incombination forms, if axial aswell as radial loads occur.

Bearing types.

Fig. 10

Fig. 11

Fig. 13

Abb. 14

12

Fig. 12



Combination bearing designsFig. 15:Double-row wire-race rollerbearing, suitable for the trans-mission of all load compo-nents. Three races form theraceways for the two inclinedaxis arranged rows of rollingelements. Shown with internalgear cut into the split outerring.

Fig. 16:Double-row inclined axis wire-race roller bearing, suitable forall load components. Shownwith external gear cut into theouter ring.

Fig. 17:Three-row wire-race rollerbearing for high and very highloads. Three bearing ringssurround two axial rows andone radial row of rollers. Thearrangement of the racewaysassures clear separation of theaxial and radial componentswithin the bearing. Shown withinternal gear cut into thesupporting ring.

Fig. 18:Wire-race cross roller bearing,suitable for withstanding allload components. This type ofbearing has two inclined axiswire-race roller bearings in oneplane, with alternately arrangedrolling elements. Shown withgear on the inner ring.

Fig. 19:Double-row wire-race ball bea-ring designed as a bilaterallyacting axial bearing for highaxial forces. The radial andmoment loads are independentfrom the amount of axial loadsustained. Shown without gear.

Special designsRothe Erde has alsodeveloped and producedspecial wire-race bearingdesigns like segmental bea-rings for very specific require-ments and operating con-ditions.

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Fig. 15

Fig. 17

Fig. 18

Fig. 19

Fig. 16



Rothe Erde wire-race bearingsreflect our company’s qualityphilosophy. The quality mana-gement system to DIN EN ISO9001, AQAP 110 and AQAP120 in place at Rothe Erdeguarantees conformance withspecifications as well as thecontinuous development ofproduct and performancestandards.

The consequent implementationof our quality strategy assuresthat all organisational, commer-cial and technical activitiesaffecting production quality areplanned, controlled and moni-tored.

The manufacturing processitself has integrated standardholding points for inspectionpurposes from base material tofinal inspection throughout allproduction stages. This includesall standard destructive andnon-destructive tests for con-trolling and determining quality-relevant features.

Quality management.

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Our commitment to quality iscomplemented by the responsi-bility we feel towards our cus-tomers. At Rothe Erde, quality isthe product of all activities, fromthe first consultation to cus-tomer service. Quality manage-ment is the connecting elementin all our activities.

We place particular importanceon the on-going training of ourentire staff. Together, weassure that only products of thehighest quality, recognised byrenowned classification andacceptance agencies, leave ourcompany.

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Management handbook Rothe ErdeProduct range large-diameter antifriction bearing.„Quality, environmental control, industrial safety“

A ThyssenKruppTechnologies

companyRothe Erde

TK

Ausgabe: September 2002



Rothe Erde wire-race bearings in space systems.

Fitness for space was demon-strated by a Rothe Erde wire-race bearing installed in arotary platform on the NASASpace Shuttle for satellitedeployment and retrieval.

It was a 4-point wire-race ballbear-ing with aluminium alloybearing rings with 1830 mmdiameter and weighing 54 kgs.

For positional accuracy and toeliminate vibrations during thelaunching sequence, the bea-ring was slightly preloaded. Itis capable of withstanding any

combination of axial and radialloads as well as tilting moments.

The raceway wires are not end-less but are provided with thebutt joint customary for wire-race bearings. While the bea-ring is exposed to the extremetemperatures in space,fluctuating between -87°C and+121°C, the different expan-sion and contraction propertiesof the aluminium alloy ringsand of the steel races arecompensated by respectiveadaptations in the butt joint.

The 1830 mm diameter of thebearing permits easy access tosatellites for repair and mainte-nance work. The gear is cutdirectly into the outer ring andserves for initiating the rotarymotion.

Fig. 20:Cross section of the Rothe Erdelight-alloy 4-point wire-race ballbearing installed in the Space Shuttle

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This bearing was designed toremain maintenance-free duringits planned 10-year service life.This included treatment with aspecial grease with high age-resistance even under extremetemperatures.

Fig. 21:Space Shuttle with opened cargo hatches. Astronaut F. Story Musgraveis coupled to the end of the remotemanipulator system carrier and preparesto be transported to the top of the uprightHubble Space Telescope to attachprotective covers to magnetometers.Astronaut Jeffrey A. Hoffman (below)helps with the final service tasks.

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Sketches and notes.

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Rothe Erde

F-92566 Rueil Malmaison CEDEXPhone: +33 (1) 41 39 00 90Fax: +33 (1) 41 39 00 99E-mail: [email protected]

Viale Kennedy, 56I-25010 Visano (Brescia)Phone: +39 (0 30) 95 20-1Fax: +39 (0 30) 95 20- 3 00E-mail: [email protected]: www.rotheerde.it

USA-Aurora, Ohio 44202Phone: +1 (3 30) 5 62 40 00Fax: +1 (3 30) 5 62 46 20E-mail: [email protected]: www.rotek-inc.com

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Rothe Erde GmbHTremoniastrasse 5-11D-44137 DortmundPhone: +49 (2 31) 186 -0Fax: +49 (2 31) 186 -25 00E-mail: [email protected]: www.rotheerde.com



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