Theory of Machine
Flexible coupling is used because

It transmits shocks gradually
It is easy to disassemble
It prevents shock transmission and eliminates stress reversals
It is easy to engage and disengage

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

T₁/T₂ = (μ θ)n
T₁/T₂ = [(1 - μ tanθ)/(1 + μ tanθ)]n
T₁/T₂ = [(1 + μ tanθ)/(1 - μ tanθ)]n
T₁/T₂ = μ. θ. n

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