## Enlarging and reducing plane figures and equivalent areas

Beginning at R. draw the sides of the larger figure parallel to the sides of the original smaller figure. This construction works equally well for reducing the size of a plane figure. Fig. 7 2 shows an irregular hexagon reduced to 4 9 its original size. These constructions are practical only if the figure which has to be enlarged or reduced has straight sides. If the outline is irregular, a different approach is needed. Fig. 7 3 shows the face of a down in two sizes, one twice that of the...

## Orthographic projection

Orthographic projection is the solution to the biggest problem that a draughtsman has to solve how to d aw. with sufficient clarity, a three-dimensional object on a two-dimensional piece of paper The drawing must show quite clearly the detailed outlines of all the faces and these outlines must be fully dimensioned If the object is very simple, this may be achieved with a freehand sketch. A less simple object could be drawn in either isometric or oblique projections, although both these systems...

## The blending of lines and curves

It is usually only the very simple type of engineering detail that has an outline composed entirely of straight lines The inclusion of curves within the outline of a component may be for several reasons to eliminate sharp edges, thereby making it safer to handle to eliminate a stress centre, thereby making it stronger to avoid extra machining, thereby making it cheaper and last, but by no means least, to improve its appoarance This last reason applies particularly to those industnes which...

## How To Draw Loci For Crank Mechanism

A locus plural foci is tha path traced out by a point which moves under given definite conditions You may not have been aware ot it but you have met loo meny times before. One of the most common loci is that of a point which moves so that its distance from another fixed point remains constant, this produces a circle Another locus that you know is that ot a point which moves so that its distance from a line remains constant this produces parallel lines. Problems on loci can take several...

## Construction Of Triangles Perimeter Altitude Vertical Angle Given

Preface to the second odition iii 1 Scale 3 The representative fraction plain scales diagonal scales proportional scales 2 The construction of geometric figures Construction of the following tnanglea Equilateral. given one of the sides Isosceles, given the perimeter and altitude Scalene, given base angles and altitude Scalene, given base, altitude end vertical angle Scalene, given penmeter and ratio of sides Scalene, given perimeter, altitude and vertical angle Similar triangles with different...

## Diagonal Scale Drawing

Three examples of diagonal scales follow. This scale would be used where the drawing is twice the m of the natural object and the draughtsman has to be able to measure on a scale accurate to 01 mm The longest natural dimension is 60 mm. This length is first divided into six 10 mm intervals. The first 10 mm is then divided into 10 pans, each 1 mm wide scaled Each of these 1 mm intervals is divided with a diagonal into 10 more equal parts To construct a diagonal seal , 30 mm 1 mm, 4 m long to...

## Some more problems solved by drawing

This chapter introduces the student to some more drawing techniques It should be emphasized that the topics are only introduced all of them can be studied in much greater depth and any solutions offered in this chepter will apply to simple probleme only. AREAS OF IRREGULAR SHAPES It is possible to find, by drawing, the area of an irregular shape. The technique does not give an exact answer but. carefully used can provide a reasonable answer. Look at Fig. 17 1. The shape is trapezoidal with...

## Further problems in loci

After 1 6 rev. the position of P the intersection of the line Pt Pi and the radius. marked off from 0 . This is repeated for the twelve divisions Fig. 16 1 also shows the beginning of a second cycloid and it can be seen that the change from one cycloid to another is sudden. If any locus is plotted and has an instantaneous change of shape H indicates that there is e cessation of movement Anything that has mass cannot chsnge direction suddenly without first ceasing to move. The point of the...

## Conic sectionsthe ellipse the parabola the hyperbola

Fig. 11 1 shows the five sections that can be obtained from a cone The tnangle and the circle have been discussed in earlier chapters this chapter looks at the remain -ing three sections, the ellipse, the parabola and the hyperbola These are three very important curves. The ellipse can vary m shape from almost a circle to almost a straight line and is often used in designs because of its pleasing shape The parabola can be seen m the shape of electnc fire reflectors, rader dishes and the main...

## Eight-course 125mm Stepped-off Diagonal Method

To construct a regular octagon given the diagonal, i. o. within given circle Fig. 2 29 1. Draw the circle and insert a diameter AE. 2. Construct another diagonal CO, perpendicular to the first diagonal. 3. Bisect the four quadrants thus produced to cut the circle in B. D. F, andH. To construct a regular octagon given the diameter, i.e. within a given square Fig. 2 30 1. Construct a square PORS. length of side equal to the diameter. 2. Draw the diagonals SQ and PR to intersect m T. 3. With...

## Urheberrechtlich geschDUIes Material

Fig. 2 hows the front elevation and plan of an ink bottle stand. Make e full size isometric drawing of the stand with corner A nearest to you. Hidden details should not be shown. West Midlends Examinations Board 3. Fig. 3 shows the development of a hexagonal box. Draw, in isometric projection, the assembled box standing on its base. Ignore the thickness of the material and omit hidden detail. North Western Secondary School Examinations Board See Ch. 14 for information not in Ch. 3 . 4. Three...