Scales

Plain Scale Diagonal Scale Comparative Scale
Dimensions of large objects must be reduced to accomodate on standard size drawing sheet. This reduction creates a SCALE of that reduction scale, which is generally a fraction. Such a scale is called REDUCING SCALE.
AND that ratio is called REPRESENTATIVE FACTOR. 

USE FOLLOWING FORMULAS FOR THE CALCULATIONS IN THIS TOPIC.

>> REPRESENTATIVE FACTOR (R.F.) = DIMENSION OF DRAWING / DIMENSION OF OBJECT   
                                                          =  LENGTH OF DRAWING / ACTUAL LENGTH 

>> LENGTH OF SCALE = R.F. * MAX. LENGTH TO BE MEASURED

TYPES OF SCALES

>>PLAIN SCALES                                        ( FOR DIMENSIONS UP TO SINGLE DECIMAL)

>>DIAGONAL SCALES                                ( FOR DIMENSIONS UP TO TWO DECIMALS)

>> COMPARATIVE SCALES                        ( FOR COMPARING TWO DIFFERENT UNITS)

>>SCALE OF CORDS                                  ( FOR MEASURING/CONSTRUCTING ANGLES)

Plain Scale


PROBLEM 1 : Draw a scale 1 cm = 1m to read decimeters, to measure maximum distance of 5 m. Show on it a distance of 3 m and 4 dm.
Calculation

R.F. 1cm/ 1m = 1/100

Length of scale = R.F. X max. distance = 1/100 X 500 cm

= 5 cms

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Diagonal Scale


PROBLEM 2 : The distance between Delhi and Agra is 200 km. In a railway map it is represented by a line 5 cm long. Find it’s R.F. Draw a diagonal scale to show single km. And maximum 600 km. Indicate on it following distances.
1) 222 km 2) 336 km 3) 459 km 4) 569 km
Calculation

RF = 5 cm / 200 km = 1 / 40, 00, 000

Length of scale = 1 / 40, 00, 000 X 600 X 105

= 15 cm

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Comparative Scale


PROBLEM 3 : A motor car is running at a speed of 60 kph. On a scale of RF = 1 / 4,00,000 show the distance traveled by car in 47 minutes.
Calculation

Scale of km.

length of scale = RF X 60 km = 1 / 4,00,000 X 60 X 105

= 15 cm.

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