If 1 centimetre long line on a map represents a real length of 4 metres. Calculate th
R.E and draw a plain scale long enough to measure up to 50 metres. Show a distance of 44 m on it
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1ENGINEERING DRAWING For I.B.TECH (ALL BRANCHES)
2DIMENSIONS OF LARGE OBJECTS MUST BE REDUCED TO ACCOMMODATE ON STANDARD SIZE DRAWING SHEET-THIS REDUCTION CREATES A SCALE OF THAT REDUCTION RATIO, WHICH IS GENERALLY A FRACTION... SUCH A SCALE •S CALLED A REDUCING SCALE AND THAT RATIO IS CALLED A REPRESENTATIVE FACTOR. SIMILARLY, IN THE CASE OF TINY OBJECTS DIMENSIONS MUST BE INCREASED FOR THE ABOVE PURPOSE. HENCE THIS SCALE IS CALLED ENLARGING SCALE. HERE THE RATIO CALLED REPRESENTATIVE FACTOR IS MORE THAN UNITY. USE THE FOLLOWING FORMULAS FOR THE CALCULATIONS IN THIS TOPIC. FOR FULL-SIZE SCALE R.F.=I OR ) MEANS DRAWING & OBJECT ARE OF SAME SIZE. Other RFs are described as 1:100, 1:1000, A B DIMENSION OF DRAWING REPRESENTATIVE FACTOR (R.F.) = DIMENSION OF OBJECT LENGTH OF DRAWING ACTUAL LENGTH AREA OF DRAWING ACTUAL AREA VOLUME AS PER DRWG. ACTUAL VOLUME LENGTH OF SCALE = R.F. X MAX. LENGTH TO BE MEASURED.
3BE FRIENDLY WITH THESE UNITS. 1 HECTOMETRE = 10 DECAMETRES TYPES OF SCALES 1 KILOMETRE 1 DECAMETRE 1 METRE 1 DECIMETRE 1 CENTIMETRE = 10 HECTOMETRES = 10 METRES = 10 DECIMETRES = 10 CENTIMETRES = 10 MILIMETRES 1. 2. 3. 4. 5. PLAIN SCALES DIAGONAL SCALES VERNIER SCALES ( FOR DIMENSIONS UP TO SINGLE DECIMAL) ( FOR DIMENSIONS UP TO TWO DECIMALS) ( FOR DIMENSIONS UP TO Two DECIMALS) COMPARATIVE SCALES ( FOR COMPARING TWO DIFFERENT UNITS) SCALE OF CORDS ( FOR MEASURING/CONSTRUCTING ANGLES)
4PLAIN SCALE:-This type of scale represents two units or a unit and its sub-division. PROBLEM NO. 1:- Draw a scale 1 cm = 1m to read decimeters, to measure a maximum distance of 6 m. Show on it a distance of 4 m and 6 dm. CONSTRUCTION:- DIMENSION OF DRAWING a) Calculate R.F.= DIMENSION OF OBJECT R.F.= lcm/ 1m = 1/100 Length of scale = R.F. X max. distance = 1/100 X 600 cm = 6 cms PLAIN SCALE b) Draw a line 6 cm long and divide it in 6 equal parts. Each part will represent a larger division unit. c) Subdivide the first part which will represent second unit or fraction of the first unit. d) Place ( 0 ) at the end of the first unit. Number the units on the right side of Zero and subdivisions on the left-hand side of Zero. Take a height of scale 5 to 10 mm for getting a look at the scale. e) After construction of scale mention its RF and name of scale as shown. f) Show the distance 4 m 6 dm on it as shown. 10 DECIMETERS 1 2 R.F. = 1/100 3 4 5 METERS PLANE SCALE SHOWING METERS AND DECIMETERS.
5PROBLEM NO.2:- In a map, a 36 km distance is shown by a line 45 cm long. Calculate the R.F. and construct a plain scale to read kilometers and hectometers, for max. 12 km. Show a distance of 8.3 km on it. CONSTRUCTION:- a) Calculate R.F. R.F.= 45 cm/ 36 km = 45/ 36 . 1000 . 100 = 1/ 80,000 Length of scale = R.E X max. distance = 1/ 80000 X 12 km = 15 cm PLAIN SCALE b) Draw a line 15 cm long and divide it in 12 equal parts. Each part will represent a larger division unit. c) Subdivide the first part which will represent the second unit or fraction of the first unit. d) Place ( 0 ) at the end of the first unit. Number the units on the right side of Zero and subdivisions on the left-hand side of Zero. Take a height of scale 5 to 10 mm for getting a look at a scale. e) After construction of scale mention it's RF and name of scale as shown. f) Show the distance 8.3 km on it as shown. 8KM 3HM 10 5 0 HECTOMETERS 1 2 3 4 5 6 7 8 9 10 11 KILOMETERS R.F. = 1/80,000 PLANE SCALE SHOWING KILOMETERS AND HECTOMETERS
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