HIGH TORQUE FLEXIBLE SHAFT SYSTEM

Mini Project report submitted to

Visvesvaraya Technological University, Belagavi in partial

fulfilment of the requirements for the degree of Bachelor of
Engineering in Mechanical Engineering

by
Pranav Ankith C (1BM20ME114)
Mohammed Imaad (1BM20ME089)
Pascal Uwimpuhwe (1BM20ME202)
Sumukh B R (1BM20ME167)

Under the guidance of

Dr. Bheemsha Arya

Professor and Vice Principal

Department of Mechanical Engineering B.M.S.

COLLEGE OF ENGINEERING
(An autonomous institution affiliated to VTU, Belagavi)
Bull Temple Road, Basavanagudi, Bengaluru 560019

February 1st, 2023

Department of Mechanical Engineering

B. M. S. COLLEGE OF ENGINEERING
Bull Temple Road, Basavanagudi, Bengaluru - 560 019
 Certificate
Certified that the mini project work entitled ’High Torque Flexible Shaft System’ is a
bonafide record of workdone carried out by

Pranav Ankith C 1BM20ME114

Mohammed Imaad 1BM20ME089
Pascal Uwimpuhwe 1BM20ME202
Sumukh B R 1BM20ME167

in partial fulfilment of the requirements for the degree of Bachelor of Engineering in

Mechanical Engineering of the Visvesvaraya Technological University, Belagavi,
during the year 2022 – 23. It is certified that all corrections/suggestions indicated
during the internal assessments have been incorporated.

Signature of Guide Signature of HOD

(Dr. Bheemsha Arya) (Dr. G. Giridhar)

Signature of Principal
(Dr. S. Muralidhara)

Semester End Examination

Name of the Examiner Signature with Date

1.

2.
 Declaration
We, hereby declare that the mini project work entitled ’High Torque Flexible Shaft
System’ has been carried out by us under the guidance of Dr Bheemsha Arya,
Professor and Vice- Principal, Department of Mechanical Engineering, B. M. S.
College of Engineering, Bengaluru, in partial fulfilment of the requirements for the
degree of Bachelor of Engineering in Mechanical Engineering of Visvesvaraya
Technological University, Belagavi.
We further declare that we have not submitted this report either in part or in full
to any other university for the award of any degree/diploma.

Pranav Ankith C 1BM20ME114

Mohammed Imaad 1BM20ME089
Pascal Uwimpuhwe 1BM20ME202
Sumukh B R 1BM20ME167

Place: B M S College of Engineering Date: 01/02/2022

 Acknowledgement
This work would not have been possible without the support and the facilities of the
Department of Mechanical Engineering, B. M. S. College of Engineering, Bengaluru
as well as the comments and suggestions from the committee members of project
work evaluation.
We are especially indebted to our guide and mentor Dr. Bheemsha Arya,
Professor and Vice Principal, Department of Mechanical Engineering, B. M. S. College
of Engineering, Bengaluru, who has been supportive and instrumental in completing
the academic goals in time.
We are grateful to our teacher, Dr. L. Ravikumar, Professor, Department of
Mechanical Engineering, B M S College of Engineering, with whom we had the
pleasure to work and complete this project work.
We would like to express our sincere gratitude to the mini project coordinator, Dr.
G. Saravanakumar, Associate Professor, Department of Mechanical Engineering,
BMSCE, for the help rendered in learning the art of publishing.
We would like to thank our Head of the Department, Dr. G. Giridhar, Professor &
Head, Department of Mechanical Engineering, B. M. S. College of Engineering,
Bengaluru, and our Principal, Dr. S. Muralidhara, Principal, B. M. S. College of
Engineering, Bengaluru.
We would like to thank Our Parents, whose love and guidance are important to
us in whatever I pursue. They are the ultimate role models who provide unending
inspiration to us. Finally, we would like to thank the one and all who have directly or
indirectly helped us in completing this project work successfully.
 Abstract

The existing modern flexible shaft transmission systems have been widely applied due
to excellent accuracy and reliability. However, the major drawback of existing flexible
shaft transmissions is low efficiency due to errors like backlash and considerable
vibrations. These vibrations engender noisy operation and cause more wear and tear
resulting in low life span. The proposed flexible shaft system transmits power with
optimum number of kinematic links according to the projected diameter of the hubs for
the most efficient power transfer. Equivalent stresses and deformation are determined
by means of static structural analysis for obtaining structural comparison between the
mechanisms through fixed angled links and kinematic chain joint links at a defined
angle. The geometric modelling is done by Solid Edge and the simulations by using
ANSYS Workbench 15.0. Furthermore, the expenditure regarding the fabrication of the
system is considerably inexpensive in comparison with the arrangement with other
available transmission elements. The results of the theoretical and simulation-oriented
analysis ensured power transmission capability and the reliability of the proposed
system.

Keywords: Efficient power transmission, Flexible shaft,

 Contents
Abstract……………….…………………………………………………………………………………… i

1. Introduction

1.1 Aim

1.2 Problems and drawbacks identified in rigid shaft power transmission

1.3 Objective

1.4 Proposed Solution

1.5 Literature Survey

2. Kinematic Analysis

2.1 Arrangement of coupling rods in the hub

2.1 Analysis for optimum number of coupling rods

2.1 Degrees of freedom and mobility

3. Design Analysis

3.1 Determination of input torque

3.2 Design of shaft

3.3 Design of hub

3.4 Design of coupling rod

3.5 Design of pin for coupling rod

4. Simulations and Case Study

4.1 Comparative analysis of proposed shaft system and already existing

Shaft systems

5. Results and conclusion

6. Bibliography
1. Introduction

1.1 Aim

To analyse and obtain optimal design of flexible shaft system which can transmit
power at high torque capacities efficiently with minimal wear and tear.

1.2 Problems and Drawbacks Identified in Rigid Shaft Power

Transmission

The major drawbacks of conventional rigid shaft power are as follows:

i) High rotational inertia especially for larger diameters.

ii) The shaft must be perfectly straight for installation. A slight offset, or shift in
centroidal axis is undesirable.
iii) Heavy, hence adding to material cost.
iv) In applications where the shaft is exposed to very high temperatures, solid
shaft made of mild steel bends even at rest. Special metal is used for this
application thus adding to the cost.
v) Not preferred for use in applications which involve high vibrations and
shocks.
vi) Can only transmit power at a prescribed angle between shafts as in the case
of geared transmission.
vii) Frictional and heat losses

1.3 Objective

The primary objective of the project is to design and validate an efficient flexible
Shaft power transmission system.
The secondary objective is to realise various applications and uses of the proposed
Flexible Shaft System in diverse fields of Engineering and Technology.
1.4 Proposed Solution

The proposed flexible shaft system comprises of 2 Hubs manufactured from

Chromium Steel (10NiCr5-4) or Cast Iron (450 Grade) and 8 Coupling Rods
manufactured from Stainless Steel (Stainless Steel 310). The Coupling Rods are
linked by means of a Pin and form a revolute pair with respect to the linked
Coupling Rod. The Coupling Rods form a slider pair with respect to the 2 Hubs and
can be made to slide coaxially along the axis of the 4 slots provided in each Hub.
Stainless Steel High Speed Linear Bearings are inserted in the slots of the Hub
between the Hub and Coupling Rods to reduce friction acting on the sliding pairs,
that is, the Coupling Rods and the Hub pair, thereby increasing the transmission
efficiency.
The mechanism is designed in such a way that the rotational motion from input
shaft via the input Hub is converted to linear motion or sliding motion of the
Coupling Rods and consequently again converted to rotational motion at the
output shaft via the output Hub. This transmission system can therefore transmit
motion at any angle between the driving shaft and the driven shaft.

The proposed flexible shaft system is based on the principle of Hobson’s

coupling. A Hobson's joint or Hobson's coupling is a type of right-angle constant-
velocity joint with rod(s) bent 90° to transmit torque around a corner.

Fig 1. Proposed Flexible Shaft System

1.5 Literature Survey

Patel Harshil K et al - estimated the design stress of the shaft and housing of the
transmission setup for proper and smooth working of the shaft by selecting the
desired factor of safety

Puneet Pawar et al - Shows the gearless power transmission arrangement used for
skew shafts. 3 Bend links were used in the elbow mechanism. While working on
experimental it brings that to put forward the process used for any set of
diameters with any profile of shafts for skew shafts of any angle but the shaft’s
must be having the rotational motion about his own axis, transmission of motion is
very smooth and used only for the same R.P.M. of driving shaft and driven shaft to
make use of pins for suitable joints for revolute pair.

R. Ranjith Kumar et al – Although this transmission is an old one many mechanics

are sceptical about its operation, however it is not only practicable but has proved
satisfactory for various applications when the drive is for shafts which are
permanently located at given angle. Although this illustration shows a right angle
transmission this drive can be applied also to shafts located at intermediate angle
between (0 and 90 degree) respectively. In making this transmission, it is essential
to have the holes for a given rod located accurately in the same holes must be
equally spaced in radial and circumferential directions, be parallel to each rod
should be bent to at angle at which the shaft are to be located. If the holes drilled
in the ends of the shafts have “blind” or 7 closed ends, there ought to be a small
vent at the bottom of each rod hole for the escape of air compressed by the
pumping action of the rods.
2 Kinematic Analysis

2.1 Arrangement of Coupling Rods in the Hub

The Coupling Rods are made to slide through the slots provided in the Hub,
forming a siding pair. The coupling Rods should be parallel and equidistant from
each other. The angle between the consecutive slots must be equal.
High Speed Stainless Steel Linear Bearings are inserted in the slots to reduce
friction between the Coupling Rods and the Hub

Fig 2. Angle between consecutive slots being equal to 90 degrees, Linear

Bearings shown in grey
2.2 Analysis for Optimum Number of Coupling Rods

From the following analysis, the minimum number of Coupling Rods required is 3
for smooth and continuous transmission of power between two shafts as shown
Table 1. Implementing more number of Coupling Rods makes the power
transmission more smooth.

1 Coupling Rod 2 Coupling Rods

Remarks : Forces are unequally distributed and Remarks : Forces are unequally distributed and
are imbalanced, hence it is not possible for are imbalanced, hence it is not possible for
transmitting power continuously. transmitting power continuously.
3 Coupling Rods 4 Coupling Rods

Remarks : If the coupling rods are not placed Remarks : Coupling Rods are placed symmetric.
symmetrically, forces are unequally distributed Forces are equally distributed and there is
and are imbalanced, hence it is not possible for continuous power transmission.
transmitting power continuously.
If the coupling rods are placed symmetrically, the
forces are equally distributed and there is
continuous power transmission.

2.3 Degrees of Freedom and Mobility

The study of motion of the flexible shaft system can be illustrated by the degree of
motion. The motions of kinematic chain link can be broken down and categorized
by sliding pair and turning pair. Transitional movement of the sliding pair, that is,
the Hub and the Coupling Rod is constituted by two elements so one is constrained
to have a sliding motion relative to the other. Turning pair or rotational movement
occurs when connections of the two elements are such that only a constrained
motion of rotation of one element with respect to the other is possible, the pair
constitutes a turning pair, as in the case of two Coupling Rods joined together by
means of a pin.
The Coupling Rod has two degrees of freedom (DOF = 2). That is, both one sliding
pair + one turning pair relative to hub) the pin joint has one degree of freedom
(DOF = 1) (only turning pair as pin is fixed and allows to rotate the same plane)
Total DOF of kinematic chain pair is three (DOF = 3)
The number of constraints (denoted by C) that a pin joint with one degree of
freedom imposes is C = 6 − F = 6 – 1 = 5.

Mobility accounts the number of parameters that define the configuration of a set
of rigid bodies that are constrained by joints or links connecting these bodies. The
joints, that connect the Coupling Rods in this system, remove degrees of freedom
and reduce mobility.

𝑗
𝑀 = ∑𝑖=1 𝑓

The above formula shows that the linkage must have an even number of links, so
we have l = 2, j = 1.

𝑀 = 3(l-1-j) + j = 3(2-1-1) + 1=1 The mobility of a planar linkage is 𝑀 = 1 and the

result is 𝑓 = 1.
3. Design Analysis

3.1 Determination of input torque

Consider motor of 0.5 kW power operating at 3000 rpm

6
Torque is given by 𝑇 = 9.55×10 ×𝑃𝑜𝑤𝑒𝑟
𝑟.𝑝.𝑚

6
= 9.55×10
3000
×0.5

= 1591.67 N-mm

Considering torque overload up to 2000 N-mm

Working torque is considered as 2000 N-mm.

3.2 Design of Shaft

𝜋
Torque capacity is given by, 𝑇 = 𝐷3 𝜏
16

𝜋 122
2000 = 𝐷3 × (FOS is 15 considering
16 15
applications at very high
torques)

Implies D = 10.77mm

Taking diameter of shaft ≈ 12mm.

4 Key Slots are provided to prevent slipping of shaft with respect to the Hub, with
dimensions
Width = 3.75mm
Height = 1.25mm
Length = 24mm
Taper = 1:100
3.3 Design of Hub

The maximum deflection of the coupling rod due to static torque is given by

1 𝐹𝐿3
𝑦=
3 𝐸𝐼
𝑇𝑜𝑟𝑞𝑢𝑒 2000
𝐹= =
𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝐷1

2000
1 ×3003
𝐷1
1= 𝜋
3 2.1×105 × 154
64

Taking permissible deflection as 1 mm, and effective length of coupling rod as

300mm, we obtain the distance of Slot from the centre of the hub, that is,
𝐷1 = 35mm

4 Key Slots are provided to prevent slipping of shaft with dimensions

Width = 3.75mm
Height = 1.25mm
Length = 24mm
Taper = 1:100

3.4 Design of Coupling Rod

The maximum deflection of the coupling rod due to static torque is given by

1 𝐹𝐿3
𝑦=
3 𝐸𝐼

Taking max permissible deflection as 3.5 mm and effective length of rod as

200mm,

2000
1 2003
3= 35
3 2.1 × 105 × 𝜋 𝑑 4
64

Solving for d, we get value of d close to 8mm.

Therefore, diameter of coupling rod can be considered as 8mm.

3.5 Design of Pin for Coupling Rod

Material selected is stainless steel.

Since no direct stresses act on the pin, the diameter of the pin can be empirically
taken as 3mm, length 8mm which is the diameter of the Coupling Rod.

The pin must be strong enough to withstand impulses due to inertia of the
Coupling Rods at high RPM.
4. Simulations and Case Study

4.1 Comparative analysis of proposed shaft system and already

existing Shaft systems

From the below ANSYS Simulation of a similar type of flexible shaft system based
on Hobson’s coupling principle, we observe that stress is almost uniformly
distributed and operation is hence smooth with very less deformations

Source: JETIR2107483
Figure: Source: Source: expertfea.com,90 deg bevel gear power transmission

From the above ANSYS Analysis for Geared Transmission, we observe stresses are
not equally distributed. Hence the rate of wear is higher for geared transmission
Figure: Source: CV Joint Analysis, www.intes.de

The above ANSYS Analysis shows stress distribution for a Universal Joint.
We observe that the stresses are more uniform compared to Geared Transmission,
but lower stress distribution compared to the Flexible shaft based on Hobson’s
Coupling.
5. Results and Conclusion

From the research analysis, we observe that the proposed flexible shaft system is
the most efficient to transmit power at any angle between the driving shaft and
the driven shaft.
Designing of Flexible Shafts nowadays are instigated with assumptions and random
dimensions because no significant development has been done before in this
unchartered territory. With software support and assiduous endeavour the final
optimal design has been obtained. The final design thus obtained is capable of
transmitting torque and power at varied angles depending on the angular
limitation of the existing joints. With further research and advanced analysis in the
design wide-ranging applications of the drive can be discovered
6. Bibliography

The Meccano Magazine ―(106)-A Curious Right-Angle Drive‖ Pg. No. 1079,
Print-1927

Charles Kostka ―A PIN-AND- SLOT, ANGLE-DRIVE WRENCH‖ Ser. No. –

735276

Prof R. Somraj , B. Shailesh- “DESIGN AND FABRICATION OF GEARLESS

POWER TRANSMISSION FOR SKEW SHAFTS”, International Research Journal
of Engineering and Technology (IRJET) , Volume: 04 Issue: 04 | Apr 2017.

Neeraj Patil, Jayesh Gaikwad, Shital Patel- “Gearless Transmission Mechanism

and its Applications” International Journal of Innovative Research in Science,
Engineering and Technology, Vol. 6, Issue 3, March 2017

Ashish Kumar, Puneet Pawar, Sagar Rana, Shishir Bist, “Multi-Angular Gearless
Drive” International Journal of Scientific & Engineering Research, Volume 6,
Issue 7, July2015

Shiv Pratap Singh, Yadav, Sandeep, Gaurav Kulkarni- “Design, Analysis and
Fabrication of Gearless Power Transmission by using Elbow Mechanism”
International Journal of Engineering Research &Technology (IJERT) Vol. 6
Issue 04, April-2017

Amit Kumar and Mukesh Kumar- “Gearless Power Transmission for Skew
Shafts (A SRRS Mechanism)”International Journal of Advanced Science and
Technology Vol.79 (2015), pp.61-72

Prof. B. Naveen Bardiya, T. karthik, L Bhaskara Rao- “Analysis and Simulation

of Gearless Transmission Mechanism", International Journal Of Core
Engineering & Management (IJCEM) ,Volume 1, Issue 6, September 2014,
Page.no: 136-142. Australia