Design procedure for Cast iron pulley, Flat belt drive, V belt drive, Chain drive and Wire ropes

Title: UNIT-I; Design Procedure of Cast iron pulley, Flat belt drive, V belt drive, Chain drive & Wire ropes.
Subject Name: ME8651 - Design of Transmission Systems (DTS) B.E. Mechanical Engineering
Third Year, VI Semester
[Anna University R-2017]

1. Prepared By: S.Thirumalvalavan & S.Selvarasu, AP/Mech, 5104-AEC. 1

UNIT - I
DESIGN PROCEDURE FOR CAST IRON PULLEYS
1. Dimensions of pulley :
i) Diameter of pulley(D) :
σc=ρv
2

where ℓ=density of rim material,
= 7200 kg/m
3
for cast iron, and
V= velocity of rim =
?????? ?????? ??????
60
, D being diameter of pulley and N the speed of the pulley.
Now select the diameter of pulley(D), by referring PSG Data Book Pg. no.7.54
ii) Width of pulley (a) : if the width of the belt is known, then select the width of pulley
refering to the following values.
Belt width pulley dia
Upto 125 mm 13mm
125 to 250mm 25mm
250 to 375mm 38mm
375 to 500mm 50mm
for other values refer width of pulley values from PSG Data Book Pg. no.7.55
iii) Thickness of pulley rim (t) :
For C.I. Pulleys,
t =
??????
200
+ 3 mm, for single belt
=
??????
200
+ 6 mm, for double belt PSG Data Book Pg. no.7.57
D = Diameter of the pulley in mm.
2. Dimensions of arms :
(i) Number of arms (n) :
No. of. arms = 4 for diameters upto 450 mm
= 6 for dia over 450 mm Refer PSG Data Book Pg.no 7.56

2. Prepared By: S.Thirumalvalavan & S.Selvarasu, AP/Mech, 5104-AEC. 2


ii) Cross section of arms (b and b/2) :
The cross section of arm is elliptical, with major axis (b) is equal to twice the minor
axis (b/2).
Major axis of elliptical section , b = 2.94 √
?????? ??????
4 ??????
3
for single belt , and
= 2.94 √
?????? ??????
2 ??????
3
for double belt
Minor axis of elliptical section = b/2
Refer PSG Data Book Pg. no.7.56.
iii) Arms taper : the arms are tapered from hub to rim.
Taper = 4 mm per 100 mm Refer PSG Data Book Pg. no.7.56
iv) Radius of cross section of arms :
r =
3
4
b
3. Dimensions of hub :
i) Diameter of hub (d1) :
Diameter of hub (d1) = (1.7 to 2.0) x diameter of shaft (d2)
d1 = (1.7 to 2.0) d2
ii) Length of the hub (l) :
minimum length of hub , l =
2
3
a
where, a = width of pulley. Refer PSG Data Book Pg. no.7.56
4. Crowning of pulley rim :
Selection of crown height (h): knowing diameter (D) and width (a) of the pulley, select
crown height (h) Refer PSG Data Book Pg. no.7.55

3. Prepared By: S.Thirumalvalavan & S.Selvarasu, AP/Mech, 5104-AEC. 1

UNIT - I
DESGN OF FLAT BELT DRIVE

1. Selection of pulley diameters:

Select the pulley diameters and angle of contact (i.e.; wrap angle). By using the given belt
speed and assuming numbers of piles, minimum pulley diameter is chosen.
For diameter of smaller pulley- PSG Data book pg. no. 7.52

2. Calculation of design power in kW:

Calculate the design power in kW by using the relationship given below

Design kW =
�??????��� �� × ��??????� �������??????�� �??????���� (��)
??????�� �� ����??????�� �??????���� (�??????) ��??????�� �����?????? �??????���� (��)


(i) Load Correction factor (Ks) : This factor is used to account for the nature of
application and type of load. The value of Ks can be selected
From – PSG Data book pg. no. 7.53

(ii) Arc of contact factor (K??????) : The load rating is given for 180° of contact. So it has to
be corrected for actual arc of contact.
Arc of contact = 180° – (
�−�
�
) × 60°
For the calculated value of arc of contact, correction factor (K??????) is selected
From – PSG Data book Pg. no. 7.54

(iii) Small pulley factor (Kd) : This factor is used to account for the amount of bending or
flexing of the belt and how this affects the life of belt.
Use the below table for small pulley factor.
Smaller pulley dia factor







3. Selection of a belting :

Select a type of belting from – PSG Data Book Pg. no. 7.54
Smaller
Pulley Diameter
Kd
Upto 100 mm
100 - 200 mm
200 - 300 mm
300 - 400 mm
400 - 750 mm
Over 750 mm
0.5
0.6
0.7
0.8
0.9
1.0

4. Prepared By: S.Thirumalvalavan & S.Selvarasu, AP/Mech, 5104-AEC. 2



4. Load rating correction :

Correct the load rating to actual speed of the belt by using the relation given below.
Load rating at V m/s = Load rating at 10 m/s ×
�
10

From – PSG Data book Pg. no. 7.54

5. Determination of Belt Width :

Determine the belt width by using the following relation:

Width of belt =
??????��??????�� ��??????��
??????�??????� �??????�??????�� × ??????�.�� �????????????��


With the smaller pulley diameter and velocity of the belt are known, the no. of plies can be
found From - PSG Data Book Pg. no. 7.52

6. Determination of pulley width :

With the belt width is known, the pulley width can be calculated
From – PSG Data book Pg. no. 7.54

7. Calculation of Belt length (L) :

The length of the Belt is found by the equation
From – PSG Data book Pg. no. 7.53
For open belt drive : 2C + (
??????
2
) (??????+�) +
(�−�)
2
4�


For closed belt drive : 2C + (
??????
2
) (??????+�) +
(�+�)
2
4�

5. Prepared By: S.Thirumalvalavan & S.Selvarasu, AP/Mech, 5104-AEC. 1

UNIT - I
DESIGN OF V – BELT DRIVE

1. Selection of Belt section :

From – PSG Data book Pg. no. 7.58,
Select the Cross section of the belt (i.e., type of belt) depending on the power to be transmitted.

2. Selection of Pulley diameters ( d and D ) :

Select smaller pulley dia (d) from table in – PSG Data book Pg. no. 7.58
Using speed ratio calculate larger pulley diameter (D) these pulley should be round off to a
standard diameter by using table from – PSG Data book pg. no. 7.52

3. Selection of center distance (C) :

Select the center distance, if not given from – PSG Data book pg. no. 7.61
Cmin = 0.55 (D+d) + T Cmax = 2 (D+d)

4. Determination of nominal pitch length :

Determine the length of the belt L by using the formula
L = 2C + (
??????
2
) (??????+??????) +
(�−??????)
2
4�
From – PSG Data Book Pg. no. 7.61
For the calculated nominal inside length and belt section, calculate the standard pitch length
From – PSG Data book Pg. no. 7.60

5. Selection of various modification factors :

(i) Length correction factor (Fc) :
For a give sheave speed, longer belt has more life than a short one., because the shorter
belt is subjected to the action of the load greater number of times. For this reason, Belt
correction factor (Fc) is used

For the selected belt cross section, and the standard length found, corresponding length
correction factor (Fc) is chosen From – PSG Data book Pg. no. 7.60.


(ii) Correction Factor for arc of contact (Fd) :
Arc of contact = 180° – (
�−??????
�
) × 60°
For the calculated value of arc of contact, correction factor (K??????) is selected .
from PSG Data book Pg. no. 7.68.

6. Prepared By: S.Thirumalvalavan & S.Selvarasu, AP/Mech, 5104-AEC. 2



(iii) Service factor (Fa) :
The service factor takes into account the severity of the load transmitted which depends
upon the characteristics of driving and driven units
Service factor (Fa) is found from table in – PSG Data book pg. no. 7.69.


6. Calculation of maximum power capacity :

Calculate the maximum power capacity ( in kW) of a V- Belt using the formula given in table
in – PSG Data book Pg. no 7.62

7. Determination of number of belts (nb) :

Determine the number of belts (nb) from the relation,

nb =
??????× ??????
??????
???????????? ×??????
� ×??????
�
From PSG Data book Pg. no. 7.70

8. Calculation of actual center distance :

Calculate the actual centre distance from the relation

Cactual = A + √�
2
−�
Where
A =
??????
4
– ?????? [
�+??????
8
]

B =
(�−??????)
2
8

From PSG Data book Pg. no. 7.61

7. Prepared By: S.Thirumalvalavan & S.Selvarasu, AP/Mech, 5104 – AEC 1

UNIT - I
DESIGN PROCEDURE FOR CHAIN DRIVES

1) Selection of transmission ratio: (i)
Refer PSG Data Book Pg. 7.74

2) Selection of no.of.teeth on driver sprocket: (z1) :
Refer PSG Data Book Pg. 7.74

3) Determination of no.of.teeth on driven sprocket: (z2) :
z2 = i x z1.
Recommended value of z2 : z2 max = 100 to 120 refer PSG Data Book Pg.7.74
Check whether z2 is less than recommended z2 max.

4) Selection of standard pitch (p):
Assume initial center distance (a),then find pitch using relation,
a = (30-50) p.
From the obtained value refer table in PSG Data Book Pg.7.74 for p value.

5) Selection of chain:
Select chain type from PSG Data Book Pg.7.71
Select chain number from PSG Data Book Pg.7.72
Select standard pitch from PSG Data Book Pg.7.73

6) Calculation of total load on driving side of chain (PT):
PT = Pt+ Pc+Ps
Where, PT = total load on driving side,
Pt = tangential force
Pc = centrifugal tension
Ps = tension due to chain sagging.

i) To find centrifugal force (Pt) :

Pt = .
Where, N = transmitted power in kw,
v= chain velocity in m/s,. .
ii) To find tangential force (Pc):
PC = mv
2
.
Where, m= mass of chain.
iii) To find tension due to sagging (Ps):
Ps = k.w.a
Refer k value from, PSG Data Book pg. 7.78,
w= m.g
a = center distance in metre.

8. Prepared By: S.Thirumalvalavan & S.Selvarasu, AP/Mech, 5104 – AEC 2


7) Calculation of service factor: (ks) :

Service factor, ks = k1.k2.k3.k4.k5.k6.
For k1 ,refer PSG Data Book pg.7.76
For k2, refer PSG Data Book pg.7.76
For k3, refer PSG Data Book pg.7.76
For k4, refer PSG Data Book pg.7.77
For k5, refer PSG Data Book pg.7.77
For k6., refer PSG Data Book pg.7.77

8) Calculation of design load:

Design load = PT x Ks.

9) Calculation of working factor of safety (FSw):
Factor safety =
10) Check for safety :
Compare working factor of safety with recommende minimum value of factor of safety
From PSG Data Book pg.7.77

11) Check for bearing stress in roller:
(PT x Ks.) / A
Compare induced stress with allowable bearing stress from PSG Data Book pg.7.77

12) Calculation of actual length (L):
Refer PSG Data Book pg.7.75

13) Calculation of exact center distance :
Refer PSG Data Book pg.7.75,
Exact center distance = a-0.01 a =0.99a

14) Calculation of pitch circle diameter of sprockets
For small one, d1,=
For larger one, d2 =
Outer dia for small sprocket, d01 = d1 + 0.8 dr.
Outer dia for large sprocket, d02= d2 + 0.8 dr.
dr value can be taken from PSG Data Book pg.7.73

9. Prepared By: S.Thirumalvalavan & S.Selvarasu, AP/Mech, 5104 - AEC 1

UNIT - I
DESIGN OF WIRE ROPES

1. Selection of suitable wire rope:
First select the suitable type of rope for the given application
From PSG data book pg.No.9.1
2. Calculation of design load:
Calculate the design load by assuming a larger factor of safety, say 15 (or find the design load
by assuming g a factor of safety 2 to 2.5 times the factor of safety)
From PSG data book pg.No.9.1
Design load= load to be lifted × Assume factor of safety
3. Selection of wire rope diameter (d)
Selection of wire rope diameter (d) from by taking the design load as the breaking strength.
From PSG data book pg.No.9.5 and 9.6
4. Calculation of sheave diameter (D):
Obtain the diameter oil sheave (or drum). Always larger sheave diameter id preferred.
*Ratio for 50 m/min of rope speeds to be increased by 8% for each additional speed of 50m/min.
From Table PSG Data book pg No. 9.3
5. Selection of the area of useful cross-sectional of the rope (A):
Select the area of useful cross-sectional of the rope, From PSG Data book pg No. 9.1
6. Calculation of wire diameter (dw):
Calculation of wire diameter of wire using the relation From, PSG Data book pg No. 9.4
�
�=
�
1.5√??????

Where i= number of wires in rope.
i= number of strands ×number of wires in each strands.
7. Selection of weight of rope (Wr):
Obtain the rope weight (Wr) from Data book pg No. 9.4 and 9.5
8. Calculation of various loads:
Calculate the various loads using the relations given below.
(i) Direct load, Wd =W+ Wr
(ii) Bending load, ??????
�=??????
�×??????=�
�
�
??????
�
×??????

10. Prepared By: S.Thirumalvalavan & S.Selvarasu, AP/Mech, 5104 - AEC 2

(iii) Acceleration load due to change in the speed of hoisting,
??????� = [
??????+??????�
�
]�
Where a =
�
2−�
1
�
(when the speed of the rope changes from v1 to v2 in t seconds)

(iv) Starting or stopping of the road:
(a) When there is no slack in the rope :
Starting load,
Wst = 2.Wd =2(W+Wr)
(b) hen there is a slack in the rope :
Starting load,
??????
�� = ??????
�� ×A =(W+W
r
) [1+√
2.a
s .h.E
r
σ
d.l.g
]
9. Calculation of effective loads:
(i) Effective load of the rope during normal working, ??????
��=??????
�+??????
�
(ii) Effective load of the rope during acceleration of the load, ??????
��=??????
�+??????
�+??????
(iii) Effective load of the rope during starting, ??????
��??????=??????
�+??????
��
10. Calculation of working (or actual) factor of safety ( FSW) :
Working factor of safety, ��
�=
??????���??????�� ���� ���� ���� ??????��� ��.�� 9.1 ��� �ℎ� �������� ����
������??????�� ���� ���??????�� ���������??????�� (??????
????????????)

11. Check for safe design:
Compare the calculated working factor of safety (FSw) with the recommended factor of safety
(n
1
) given in the PSG Data Book pg.no. 9.1. If the working of factor of safety is g-reater than
the recommended factor of safety, then the design is safe and satisfactory.
If FSw<n
1
, then the design is not satisfactory. Now choose some other rope with greater
breaking strength or increase the number of ropes.
12. Calculation of number of ropes:
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