DESIGN PROCEDURE

Calculations for Belt Width:

Width of belt is depends upon the lump size which depends upon the following factors,

1. Volume of material to be conveyed

2. Angle of repose of material to be conveyed

3. Density of material to be conveyed

4. Troughing angle of belt

5. Maximum allowable belt speed

Let,

Mass of material conveyed per unit length of belt

=

Volume to be conveyed per meter length of belt,

V =

V =

Area of cross section of lump on troughed belt of width w is shown in figure. Hence

area of cross section of lump can be calculated as,

A = (0.6w + 0.6w + 2 0.2w cos) 0.2w sin + (0.6w + 0.4w cos)

(0.6w + 0.4w cos) cot

Volume/ meter length of belt (V) = A 1

This must be equal to volume to be conveyed per meter length of belt,

= (0.6w + 0.6w + 2 0.2w cos) 0.2w sin + (0.6w + 0.4w cos)

(0.6w + 0.4w cos) cot

Knowing , , , belt width w can be calculated and selected from standard range available.

Calculations for Motor Power:

Work is required to raise the material against gravity and to overcome the rolling resistance

between the idler rollers and belt.

Resistance to move the material horizontally,

= g (m + )

Where,

= coefficient of rolling resistance (for this application it lies between 0.15 to 0.3)

g = gravitational acceleration

m = total load over whole length

= length of conveyor

= mass of belt

= mass of belt per unit length length of belt

Resistance to raise the material against gravity,

= g m L sin

Where,

g = Gravitational acceleration

m = Total load over whole length

L = Total length of conveyer

= Angle of elevation

Maximum resistance,

= ( + )

For lagged pulley is 1.3. from table

Motor power:

Power required (P) = total force speed of belt

P = v

Motor Power,

=

Where,

= transmission efficiency

Calculations for Minimum Pulley Diameter:

The minimum drive pulley diameter can be calculated as,

=

Where,

= 25. from table

= Angle of contact

The next standard diameter of pulley available in the market should be used.

The length of driving pulley rollers should be slightly more than that of width of belt. The

standard clearances on both sides of belt for different belt widths have been given in the table.

Rotational speed of roller:

Rotational speed of the roller is the function of diameter of roller and belt speed. Rotational

speed of pulley (N) can be given as,

N =

Calculations for Belt Selection:

Drive side tensions and are related by,

= Total force

=

where,

= Tight side Tension

= Slack side Tension

Also,

=

Where,

= Coefficient of friction between belt and pulley

= Angle of Wrap

Now,

Belt Stress =

=

Belt safety factor =

The recommended maximum belt tension (RMBT) is provided by the belt manufacturer

for the belts of different widths. The belt safety factor should be more than one, if not, select next

belt of higher ply rating.

Calculations for Design of Drive Shaft:

Motor Torque,

=

Where,

= Motor Power

= Motor Speed

Gear Box Reduction Ratio,

G =

G =

Torque at drive shaft,

= Motor torque gear box reduction

= G

According to maximum shear stress theory for shaft design,

=

d =

where,

d = diameter of drive shaft

= maximum shear stress

= torque at drive shaft

= bending moment

The next standard diameter of shaft should be used.

Selection of Bearings:

The general equation for equivalent dynamic load is given by,

= X + Y

where,

= equivalent dynamic load

= axial or thrust load (N)

In our case the load is pure radial and there no axial load or thrust hence,

= = ( )

The dynamic load capacity is given by,

=

where,

= dynamic load capacity (N)

= rated bearing life (in million revolution)

p = 3(for all ball bearings)

p = 10/3 (for roller bearings)

Bearing life can also be given in working hours.

The relationship between life in million revolutions and life in the working hours is given by,

=

where,

= rated bearing life (hours)

n = speed of rotation (rpm)

According to the value of dynamic load capacity c, select the suitable bearing from the

manufacturers catalog for the given shaft diameter.