Machine Design
In a band and block brake, the ratio of tensions on the tight and slack sides of band is given by (where μ = Coefficient of friction between the blocks and the drum, θ = Semi-angle of each block subtending at the centre of drum, and n = Number of blocks)

T₁/T₂ = [(1 - μ tanθ)/ (1 + μ tanθ)]n
T₁/T₂ = [(1 + μ tanθ)/ (1 - μ tanθ)]n
T₁/T₂ = (μθ)n
T₁/T₂ = μθ × n

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Machine Design
In the calculation of induced shear stress in helical springs, the Wahl's stress factor is used to take care of

Combined effect of bending stress and curvature of the wire
Combined effect of transverse shear stress and bending stress in the wire
Combined effect of torsional shear stress and transverse shear stress in the wire
Combined effect of transverse shear stress and curvature of wire

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Machine Design
When the belt speed increases

Power transmitted increases to a maximum value and then decreases
Power transmitted decreases
Power transmitted remains the same
Power transmitted increases

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