BELT DRIVE

Term & symbol

Nisbah halaju (velocity ratio) – nSudut lekapan (angle of contact) – θJarak antara pemacu & penurut (distance between driver & driven) – xTegangan tali sawat (belt tension) – F (sometimes T)Kesan empar terhadap tegangan talisawat (centrifugal effect on belt tension) – FcKuasa terhantar (power transmitted) – P

Speed ratio

Velocity ratio; n

Assuming no slip

but

and d=2r

Therefore;

+ +driver

driven

d1d2

N1N2

tension, F1

slack, F2

Angle of contact

For open drive:

Note: always measure angle of contact from smaller pulley

, in radian

For cross drive:

, in radian

Belt tension

x

α

α

α

α

O1O2

M

θ N1, r1N2, r2

driverdrivenα

α

α

α

α

O1O2

M

θN1, r1N2, r2driverdriven

α

E

F1 - belt tension at tension side (N)F2 - belt tenson at slack side (N)Fmax – max belt tension before fail

For flat belt [flat belt, inelastic, friction theory]

F1 - belt tension at tension side (N)F2 - belt tenson at slack side (N)Fc – tension due to centrifugal effect (N)μ – coefficient of friction between belt & pulleyθ – angle of contact (rad)

cross-section view side view

For V belt [flat belt, inelastic, friction theory]

or

F1 - belt tension at tension side (N)F2 - belt tenson at slack side (N)Fc – tension due to centrifugal effect (N)μ – coefficient of friction between belt & pulleyθ – angle of contact (rad)

Fc

F2

F1

+

belt

pulleyfriction

belt

pulley

friction

angle = 2β

Where:

and

m – weight per unit length (kg/m)v – velocity (m/s)ρ – belt material density (kg/m)

belt initial tension

Power transmission

and

Belt creep (only for elastic belt)

When creep occur:

Thus, power:

(use v2 for calculation)

A – cross-sectional area of belt (m2)E – belt material modulus of elasticity (N/m2)

+ +driver

driven

d1d2

N1N2

tension, F1

slack, F2Velocity, v1Velocity, v2