Post on 07-May-2015
description
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