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

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Machine Design
A hollow saddle key is

A taper key which fits in a key way of the hub and is flat on the shaft
Provided in pairs at right angles and each key is to withstand torsion in one direction only
A taper key which fits half in the key way of hub and half in the key way of shaft
A taper key which fits in a key way of the hub and the bottom of the key is shaped to fit the curved surface of the shaft

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Machine Design
According to I.B.R., when the thickness of boiler shell (t) is greater than 8 mm, then the diameter of rivet hole (d) is obtained by

Equating tearing resistance of the plate to the shearing resistance of the rivets
Equating shearing resistance to the crushing resistance of the rivets
Equating tearing resistance of the plate to the crushing resistance of the rivets
None of these

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