Machine Design Miscellaneous
 A force of 400 N is applied to the brake drum of 0.5 m diameter in a band brake system as shown in figure, where the wrapping angle is 180°. If the coefficient of friction between the drum and the band is 0.25, the braking torque applied, in Nm is

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As the drum is rotating in anti clock wise direction, T_{1} will be right side & T_{2} will be clock side.T_{1} = e^{μθ} = e^{0.25 × π} = 2.19 T_{2}
⇒ T_{2} = = 182.375 N
Braking torque = (T_{1} – T_{2} )r
= 54.4 N – mCorrect Option: B
As the drum is rotating in anti clock wise direction, T_{1} will be right side & T_{2} will be clock side.T_{1} = e^{μθ} = e^{0.25 × π} = 2.19 T_{2}
⇒ T_{2} = = 182.375 N
Braking torque = (T_{1} – T_{2} )r
= 54.4 N – m
 A band brake having bandwidth of 80 mm, drum diameter of 250 mm, coefficient of friction of 0.25 and angle of wrap of 270 degrees is required to exert a friction torque of 1000 N m. The maximum tension (in kN) developed in the band is

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Given: b = 80 mm = 0.08 m D = 250 mm = 0.25
R = D = 0.25 2
μ = 0.25θ = 270° = 270 × π = 4.712 radians 180
F_{t} = 100 NmAs p_{1} = e^{μθ} p_{2}
⇒ p_{1} = e^{μθ} ⋅ p_{2} = e^{0.25 × 4.712} ⋅ p_{2} = 3.25p_{2}
Now, F_{t} = (p_{1} − p_{2})R∴ 1000 = p_{1} − p_{1} 0.125 3.25
Solving, we get maximum tension in the belt,
p_{1} = 11.56 kNCorrect Option: D
Given: b = 80 mm = 0.08 m D = 250 mm = 0.25
R = D = 0.25 2
μ = 0.25θ = 270° = 270 × π = 4.712 radians 180
F_{t} = 100 NmAs p_{1} = e^{μθ} p_{2}
⇒ p_{1} = e^{μθ} ⋅ p_{2} = e^{0.25 × 4.712} ⋅ p_{2} = 3.25p_{2}
Now, F_{t} = (p_{1} − p_{2})R∴ 1000 = p_{1} − p_{1} 0.125 3.25
Solving, we get maximum tension in the belt,
p_{1} = 11.56 kN
 In spur gears, the circle on which the involute is generated is called the

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NA
Correct Option: C
NA
 Interference in a pair of gears is avoided, if the addendum circles of both the gears intersect common tangent to the base circles with in the points of tangency.

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NA
Correct Option: A
NA
 For a pinion of 15 teeth, under cutting ______ (increases/decreases) with _______(increase/ decrease) of pressure angle.

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Interference decreases with increase in pressure
Correct Option: A
Interference decreases with increase in pressure