Design of a Transmission System with Parametric CAD Implementation

Design of a Transmission System with Parametric CAD Implementation
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Contents
Section A: Complete System Design Calculations..........................................................................3
A. Identification of Parts:.............................................................................................................3
B. Calculation of power:..............................................................................................................6
C. Selection of a Grooved pulley to replace existing Flat pulley:.............................................11
D. Selection of V belt system to replace the Existing Flat belt pulley AB:...............................16
E. Design of Shaft:.....................................................................................................................22
F. Fatigue Analysis of shaft.......................................................................................................32
G. Design of shaft deflection:....................................................................................................38
h. Keys and Keyways selection:................................................................................................41
I. Selection of bearing:...........................................................................................................43
Section B: CAD implementation:..................................................................................................46
1. 3D CAD models:....................................................................................................................46
1.1 Complete Assembly:........................................................................................................46
Parts............................................................................................................................................47
2. 2D Drawings..........................................................................................................................51
Section C:.......................................................................................................................................57
Discussion and Recommendations:...............................................................................................57
Conclusion:....................................................................................................................................57
References......................................................................................................................................58
Appendix A:...................................................................................................................................59
Appendix B:...................................................................................................................................61

Section A: Complete System Design Calculations
A. Identification of Parts:
In this topic the various parts associated with the system which was examined will be explained
briefly with their operations. The schematic layout of the given system is given at the figure1.
The various parts of the system will be initially identified and then explained briefly.
Figure1. Image illustrates the schematic of the given system.
The various parts present in the system are:
1. A Shaft of 850mm Length.
2. Pulley AB of 250 mm diameter.
3. Pulley CD of 300 mm Diameter.
4. Assembly of two Bearings with housing at the both ends.
5. Keyways
6. Screws.
Part1: Shaft:
The Major part of the system is the shaft. A shaft is a rotating machine element which is used to
transmit motion, torque and power. The shafts are of circular cross section in general. The shaft
plays a key role in power transmission such as gearbox, propeller shaft, wheel axle shafts, etc.
The shafts should be designed for reliability, strength and life. It should have good load bearing
capacity and also the vibrational characteristics must be considered. The shaft designed should

be targeted for low mass and high strength. Material for the shafts are generally low carbon steel,
hot rolled steel, cold drawn steel, etc. (Whitman, M.P. 2015)
Part2: Pulleys
The system consists of two pulleys one of diameter 250 mm and another pulley of 300mm
diameter which are used to receive and transmit power from the source to the final system. One
of the pulley among them is driving pulley another one is driven. A pulley is a mechanical
structure which consists of a wheel attached to a shaft, it is rotated by a belt assembly which is
mounted at the top of the pulley wheel. There are many types of pulleys such as Flat belt pulley,
V-groove pulley, double V-groove pulley, etc. The pulleys are to be selected on the basis of the
power transmission requirements, torque loads acting, type of applications and the reliability
requirements of the system. (Antchak, J.R., et.al 2018)
Part3: Bearings with housing:
A bearing is a machine part which act as a support to the parts in motion and also helps to
confine the motion of the part. The bearing is utilized in almost all machine parts such as
automobiles, pumps, generators, turbines, etc. The bearings are selected on the basis of the
design of the shaft and the service factor requirements. The bearings are of different types. They
can be classified as follows:
1. Radial bearings
2. Thrust bearings
1. Radial bearings:
Figure2. Image illustrates the various parts of a radial bearing assembly.

The radial bearings are also called as sliding contact bearings, they can be used in the application
where the loads are acting along the circumferential direction along the bearings. The figure2
illustrates a typical radial bearing.
They are further classified into four types as:
a) Zero film bearing.
b) Thin film.
c) Thick film.
d) Externally pressurized.
2. Thrust bearings:
Thrust bearings are used in places where axial thrust force acts on the bearing such as office
chairs and other machine components.
Figure3. Illustrates the thrust bearing exploded view.
Bearings are mounted on a supporting house which is used to confine the bearing and the shaft
attached to the bearing. The whole assembly is bolted or attached to a foundation.

Figure4. Image illustrates a typical bearing confined on a housing.
B. Calculation of power:
Power to be transmitted:
The layout diagram of the existing system si provided the data available from the given system
are the geometric properties of the shaft, pulleys, the distance between two pulleys, etc. The
power transmitted is not provided, so the power transmitted by the exsiting system will be
calculated. Then the power flow required by the system to be redesigned will be calculated by
finding the value of the power that is 15 times greater than that of the calculated power of the
existing system. As the power requirement is given as 15 times the proposed system. (Gonen, T.,
2015)
Power transmitted by the existing system:
The power is given by the equation:
P = 2 πNT/ 60 in Watts
Where,
N is the speed in RPM

T is the Toque
Now,
The toque of the existing system can be calculated as:
Torque, T = π
16 ƫ d3
Where,
ƫ is the shear stress in N/m2
d is the diameter of the shaft in m.
T is the toque in N.m
The power of the existing system can be calculated by finding the power transmitted by the
pulley on the existing system as the pulley is mounted on the shaft only.
The power transmitted by the Pulley CD can be calculated as:
P = (T𝛚)
Where,
P is the power transmitted.
T is the Torque transmitted.
𝛚 is the Angular acceleration.
The torque T can be calculated using the relation between the forces acting
on the tight and slack side of the pulley. The forces are acting on the side F1
and F2 for the existing system is given as:
T = (F1-F2) r
Where,
F1 is the Force acting on the tight side.
F2 is the force acting on the slack side.
r is the radius of the pulley.

From the diagram provided in the Appendix A the force transmitted F1 and F2 are taken as:
Force on tight side, F1: 270 N
Force on slack side, F2: 50 N
Radius: r: 0.15 m
Now,
T = (270-50)(0.15)
T = 33 N.m = 24.339 Ft-Ib
The total amount of power transmitted by the pulley CD is:
From the technical specifications the angular velocity of the Shaft: 1500 Rpm: 157 Rad/sec
P = 33(157) = 5181 W = 5.181 KW
P = 7.0441996 PS
The power transmitted by the pulley CD is found as 7.0441996 PS.
The forces acting on the P1 and P2 sides of the Pulley AB when considering the frictional
losses of 10 percent. Can be calculated as follows:
Considering 7.0441996 PS of Power is transmitted from the Pulley CD of diameter 300 mm.
Power loss due to friction: 10 percent
Shaft rotation: 157 Rad/sec
Angle of the pulley: 2A = 450
Diameter of pulley CD: 300 mm
Diameter of the pulley AB: 250 mm
Radial difference between the diameters of the pulleys
Power transmitted by the Pulley AB = (7.0441996) (0.9) [Considering 10 percentage
power loss]
Power, P = 6.34 Ps