TechnicalEnglishUnit6

professionalEnglishDimensions ofcircles

Prof.HalaJ.El‐KhozondarSpring2017

Contents

A. Key dimensions of circlesB. Types of views used on drawings

A. Keydimensionsofcircles

Anengineerisgivingatrainingcoursetoagroupoftechnicalsalesstaffwhoworkforatyremanufacturer.Duringthetalk,shementionsanumberofdimensionsrelatingtocircles.Obviously,theoutsideedgeofatyreformsacircle,asyoucanseeinthissimplediagram.

A. Keydimensionsofcircles

Theoutercircleinthediagramistheoutsideofthetyre,andtheinnercircle‐ thecirclewiththesmallerdiameter‐ representsboththeinsideofthetyre andtheoutsideofthewheel.And,clearly,theinnercircleisrightinthemiddleoftheoutercircle‐it'sexactlyinthecentre.Sobecauseit'scentral,thatmeanstheinsideandoutsideofthetyre formconcentriccircles.Andasthetyre iscircular,simplegeometrytellsusthatmeasurementsoftheradius,takenfromthecentre ofthecircletodifferentpointsonitsedge‐pointsonthecircumference‐ areequal.Alltheradiiarethesame.Inotherwords,thetyre hasaconstantradius.'

A. Keydimensionsofcircles

Butwhenatyre isfittedtoavehicle,it'scompressedagainsttheroadsurface.Thatmeansitsgeometrychanges.Sowhilethewheel‐ theinnercircle‐ obviouslyremainsround,thecircumferenceofthetyre ‐ theoutercircle‐ changesshape.Itdeforms.

A. Keydimensionsofcircles

Before deformation, this part of the tyre forms an arc ofthe circle, between points A and B. So, as you can see inthis diagram, it's not a straight line ‐ it's a curved line. Butafter deformation, it's no longer a curve. The tyrebecomes deformed between points A and B. It becomes achord of the same circle, forming a straight line betweenA and B.

However, the length of a chord and the length of an arc,between the same two points on a circle, are different. Sothe design of the tyre has to allow for this change inshape‐ from a rounded edge to a straight edge.

Technicians are discussing different views shown on drawings (looking at components from above, from the side, etc.), as they search for the information they require.

In non-technical, everyday English, engineering drawings are often called plans.

Section is the short form of cross-section, and is commonly used in technical contexts.

Two-dimensional and three-dimensional are often shortned to 2D and 3D.

B.Typesofviewsusedondrawings

• Specifictermsareusedtodescribethecirculardimensionsofpipes.Thewidthoftheinsideofapipeiscalledtheinsidediameter(ID).Itcanalsobecalledthe bore.Theoutsidewidthiscalledtheoutsidediameter(OD).Whenpipesarelaidhorizontally,thetopoftheoutsideofthepipeiscalledthecrown,andthebottomoftheinsideofthepipeiscalledtheinvert.

B.Pipedimensions

6.1Completethenotes,madebyasalespersonattendingthe engineer'stalk,usingthewordsinthebox.

Beforetyres arefittedtovehicle:

Arc,chord,circular,circumference,constant,curved,deformed,diameter,radius

6.2 Findwordsandexpressionswiththefollowingmeanings.Onequestionhastwopossibleanswers.1. thehighestpointofahorizontalpipe

2. thelowestpointoftheinsideofahorizontalpipe

3. themaximumoverallexternalwidthofapipe

4. themaximuminternalwidthbetweenthepipewalls

6.3Changeonewordineachofthesentencesbelowtocorrectthem

1. Thedistancetravelledbythevehicleeachtimeitswheelsturncompletelyisequaltotheradiusofoneofitstyres.

2. Thediameterofthetyre ismeasuredfromthecentre ofthewheeltotheoutsideedgeofthetyre.

3. Theradiusofthecurveinthemotorwayisconstant,sotheedgesoftheroadfollowchordsofacircle.

4. Thecurveinthemotorwayhasaconstantradius,sotheinsideandoutsideedgesoftheroadarearcsoftwodeformedcirclesthathavethesamecentre.

5. Theinvertisonthecircumferenceoftheexternalfaceofthepipe,andthereforecannotbeincontactwiththeliquidflowinginsidethepipe.

6. Thethicknessofthewallatthebottomofthepipe,plusthedistancebetweentheinvertandthecrownofthepipe,isequaltotheinsidediameterofthepipe.

6.3Changeonewordineachofthesentencesbelowtocorrectthem

Solution6.31. Thedistancetravelledbythevehicleeachtimeitswheelsturncompletelyisequalto

thecircumference ofoneofitstyres.

2. Theradiusofthetyre ismeasuredfromthecentre ofthewheeltotheoutsideedgeofthetyre.

3. Theradiusofthecurveinthemotorwayisconstant,sotheedgesoftheroadfollowarcs ofacircle.

4. Thecurveinthemotorwayhasaconstantradius,sotheinsideandoutsideedgesoftheroadarearcsoftwoconcentric circlesthathavethesamecentre.

5. Thecrown isonthecircumferenceoftheexternalfaceofthepipe,andthereforecannotbeincontactwiththeliquidflowinginsidethepipe.

6. Thethicknessofthewallatthebottomofthepipe,plusthedistancebetweentheinvertandthecrownofthepipe,isequaltotheoutside diameterofthepipe.

Iseeyougotright