A chain drive is to be used to transmit 5 kW power from an electric motor running at 1000 r.p.m to a machine running at 500 r.p.m The service conditions involve light shock.

i) Select a standard roller chain. ii) Determine the pitch circle diameters of driving and driven sprockets. iii) Determine the length of the chain. iv) Specify the correct centre distance between the axes of sprockets.

Mumbai University > Mechanical Engineering > Sem 7 > Machine Design 2

Marks: 10M

Year: Dec 2016

[R] =

$K_s = K_1.K_2 K_3 K_4 K_5\\ K_1 = 1.25\\ K_2 = 1\\ K_3 = 1\\ K_4 = 1\\ K_5 = 1.25$

$K_s = 1.5625$

$[P] = 7.8125 is P \times K_s$

By Resheter equation

$P \geq 1.8 \sqrt[3]{\frac{[M_t]}{\sigma_{brg}m.z_1}}$

$z_1 = 27$ for i = 2 (PSG 7.74)

$z_2 = iz_1 = 54 \approx 55$

connected i = 2.037 $[M_t] = 68.587 N-m$

$\sigma_{brg} = 2.24 kgf/mm^2 = 22.4N/mm^2$

for 2 strand chain

Selecting DR 1278 $d_r = 8.51 mm\\ \text{Brg area} = 1 cm^2\\ w = 1.32 kgf\\ a = 3180 kgf$

Diameter of sprocket $d_1 = \frac{P}{sin \frac{180}{z_1}} = 109.3951$

Diameter of driven sprocket $d_2 = \frac{P}{sin \frac{180}{z_2}} = 22.4604$

No. of links

$l_p = 2a_p + \frac{Z_1 + Z_2}{2} + \frac{\Big( \frac{Z_2 - Z_1}{2 \pi}\Big)^2}{a_p}$

$a_p = 40 \hspace{1cm} PSG 7.75$ $\hspace{0.5cm} = 119.7$ $l_p \approx 120 links$

Length of chain

$L = l_p \times P\\ L = 1524 mm$

Centre distance corrected

$a = l + \frac{\sqrt{e^2 - 8m}}{4} P\\ e = l_p - \frac{Z_1 + Z_2}{2} e = 79\\ M = 19.86 (PSG 7.76)\\ a = 498.436$