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

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Machine Design
The ends of the leaves of a semi-elliptical leaf spring are made triangular in order to

Have variable bending moment (M) in each leaf
Permit each leaf to act as an overhanging beam
Make M/I constant throughout the length of the leaf
Obtain variable moment of inertia (I) in each leaf

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