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)
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
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
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.