Page 172 - CITS - Fitter Trade Practical - Volume -2

FITTER - CITS

x + y + z + y + x = 2x + 2y + z
Then add the bent space distances together. For calculating this:- take the radius of the bent up to the neutral
axis and also take the angle of the bend into consideration. (Fig 4).

Radius of the bend up to neutral axis = inner radius + 0.5 x thickness of sheet OR diameter of rod or pipe. Angle
of the bend with respect to Figs 3 & 4 is 90.
Length of the curved space

where ‘R’ is the radius of the curve at the neutral axis.
Calculation of stretching length (Fig 5)

Straight spaces length

200 − (130 + 6 + 6)
x = = 29mm
2
y = 54 − (6 + 6 ) = 42mm

z = 130 − (3 + 3 ) 124mm=
2x + 2y + z = 58 + 84 + 124 = 266mm

There are four bends all having a 90o angle.
R (Radius up to neutral axis)= 3+1.5 = 4.5 mm
90 22
Stretch length of one bend = x2x x4.5
360 7
90 22
For all the four bends = 4x x2x x4.5 = 28.28mm
360 7
Total stretched length = 266 + 28.28
= 294.28 or = 295 mm
In the above calculation the angle of the bend is taken as 90o. For calculating the curved length for any bend-
ing angles the following formula can be used.(Fig 6).

157

CITS : C G & M - Fitter - Exercise 86 - 88