Reg. 310, Reg. 311, Reg.
||The permanent set
in the spring (defined as the difference between free
height and height measured ten minutes after the spring
has been compressed solid three additional times, after
pre-setting at room temperature) shall not exceed 0.5%
of the free height.
||Torsion bars shall
not show a permanent distortion after being twisted to
an angle fifty per cent in excess of the working angle.
|Extension springs shall be made
from round section wire.
Number of Effective Coils
|The number of effective or free
coils in a compression or extension spring shall be determined
from the following formulae:-
(i) For Round or Square Wire: -
(ii) For Rectangular Wire: -
||66 B³ H³
|(B² + H²
N = Number of effective coils.
K = Compression or tension in inches at set pressure.
C = 22 for round, 30 for square steel.
d = diameter or side of square steel in 16th of an inch.
S = Load on spring in lbs. at blow off pressure.
D = Mean diameter of coil in inches.
B = Breadth of wire in 16th of an inch.
H = Depth of wire in 16th of an inch.