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

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Machine Design
Jam nut is a locking device in which

A hard fibre or nylon cotter is recessed in the nut and becomes threaded as the nut is screwed on the bolt causing a tight grip
Through slots are made at top and a cotter pin is passed through these and a hole in the bolt, and cotter spitted and bent in reverse direction at other end
A slot is cut partly in middle of nut and then slot reduced by tightening a screw
One smaller nut is tightened over main nut and main nut tightened against smaller one by loosening, creating friction jamming

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Machine Design
When the belt is transmitting maximum power,

The tension in tight side is twice the centrifugal tension
The tension in tight side is thrice the centrifugal tension
None of these
The tension in slack side is equal to the centrifugal tension

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