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Project No: D04
Mini Project Report
on
Analysis of Treadle Pumps
Submitted by Arpit Kumar Khandelwal (Entry No: 2009ME10566)
Kshitij Jain (Entry No: 2009ME10588)
Supervised by
Prof. S.K. Saha
Examiner
Dr. Harish Hirani
Mechanical Engineering Department Indian Institute of Technology Delhi
April 2012
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Contents
Certificate 2
Acknowledgement 3
List of Figures 4
List of Tables 4
Abstract 5
1. Introduction 6
1.1 Significance of Treadle Pump 6
1.2 Working of Treadle Pump 6
1.3 Problem Identification 7
1.4 Objectives 8
2. Literature Review 9
2.1 Pump Design Features 9
2.2 Modifications in Treadle Pumps 11
2.3 Performance Characteristics 12
2.4 Scope of Present Work 13
3. Development of Mathematical Model
3.1 Nomenclature 14
3.2 Assumptions 15
3.3 Governing Equations 16
3.4 Analysis of Current Design 18
3.5 Modifications in current design 22
3.5.1 Maximizing Q 22
3.5.2 Minimizing Ff 23
3.6 Other Suggestions to improve Performance 25
4. Preliminary Analysis of a new alternate mechanism 27
5. Conclusion 21
References 32
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Certificates
The work presented in this report has been carried out by us for the course MED310.The report
accurately reflects the work done by us. All the material taken from other sources has been fully
acknowledged. The report is free of plagiarism.
_____________ ___________
Arpit Kumar Khandelwal Kshitij Jain
2009ME10566 2009ME10588
______________________________________________________________________
Arpit Kumar Khandelwal and Kshitij Jain have worked under my supervision. I have read this
report. It accurately reflects the work done by the students.
_______________
Prof. S.K. Saha
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Acknowledgement
We would like to thank our guide, Prof. S.K. Saha for providing invaluable guidance, support
and assistance for completing this work.
We also thank Mr. Rajkumar from RuTAG IIT Delhi for giving us insights about the field
performance of the concerned device and the problems associated with the same.
Finally, we express our gratitude to our friends and family for their support and encouragement.
Arpit Kumar Khandelwal Kshitij Jain
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List of Figures
Figure-1: Schematic diagram of the pump in motion
Figure-2: Stages of operations
Figure-3: Free body diagram of the piston
Figure-4: Free body diagram of treadle
Figure-5: CAD Model of the current system
Figure-6: Plot of power (W) vs. piston diameter (mm) for current and new design
Figure-7: Variation of discharge Rate with piston diameter for current and new design
Figure-8: Variation of Force (N) with piston diameter (mm)
Figure-9: Plot of discharge rate with piston diameter for minimum force condition
Figure-10: CAD Model of a new design using slider crank mechanism
Figure-11: Schematic diagram of slider crank mechanism
Figure-12: Variation of power (W) vs. crank angle (θ) at different transmission angles
Figure-13: Variation of force (N) vs. crank angle (θ) at different transmission angles
List of Tables
Table-1: Performance characteristics of different type of treadle pumps
Table-2: Calculation of foot force and power for various cadences for the current design
Table-3: Ranges of allowable parameter variations
Table-4: System parameters of the new modified design for maximum Q
Table-5: System parameters of the new modified design for minimum Ff
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Abstract
Treadle pumps have come out as a low cost, sustainable, simple, green and revolutionary
alternative irrigation technology for the small scale poor farmers especially in developing
countries where lack of irrigated land is the major reason for the poverty and underdevelopment
of the farmers. This pump is also used in the villages of U.P. in India. Improving the
performance of the treadle pump by properly analyzing- all the design parameters, performance
characteristics, ergonomic aspects, is the objective of this project. The project is an attempt to
benefit the farmers in U.P., India who are facing some serious performance, ergonomic,
maintenance issues with the current device. Our approach toward the problem have been focused
towards optimizing the design by putting the constraints on human power, ergonomic features-
cadence and stroke length, and the human force according to the Indian conditions.
We have developed governing equations and modeled them in to excel sheets which can give the
optimized solution according to different input variables and conditions. As the result of this
project now we have an improved design which on theory, will require less human power and
human force to produce the same discharge rate and at the same time will be ergonomically
comfortable to use, which was the major problem for the farmers.
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Chapter 1
Introduction
1.1 Significance of Treadle Pump
One of the strategies used to combat food crisis and to meet the demands of the growing
population, especially in the poor developing countries is the introduction of cheap and efficient
technologies that would make it possible to produce food all year round, overcoming the water
shortage [1]
. One of the best ways this can be achieved is by making appropriate irrigation
technology available to farmers. Problem arises as there are many poor farmers doing farming on
a very small land, and can’t afford to use modern technologies for irrigation purposes like tube-
wells, diesel generators to run the pumps. That’s why there is a pressing need to identify an
alternative low cost water lifting device especially in the developing countries like Bangladesh,
India, Vietnam, Nepal, Cambodia and other African Countries where water tables are not so deep
and a less power intensive solution to pump out the water can be thought of, which led to the
development of treadle pumps. It was first developed in the Bangladesh in 1980’s [1]
.
1.2 Working of Treadle Pumps
Treadle pumps are foot operated pumps which use the human power to generate the
reciprocating motion of the pistons which is produced by the use of slider crank mechanism to
suck water out of the ground. The operator stands on treadles and presses them up and down in a
rhythmic motion – like pressing the pedals on a bicycle. This motion can also be described as
similar to walking and because of that farmers have readily accepted this technology. The treadle
action uses the large muscles of the legs, buttocks, and back. This allows sustained use of the
pump and the pumping of large volumes of water that are needed for irrigation [2]
.
There are currently several designs of treadle pump produced which are the modified versions of
the initial design according to the variation in the applications and the operating conditions of the
people in different countries. These modifications are done in terms of the basic mechanisms and
the materials used in the design of the pump.
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1.3 Problem Identification
In spite of the many virtues of the treadle pump, many difficulties arise as they are human
powered and humans can apply only a limited amount of power. It often happens that the farmers
who run the pumps feel pain in their muscles and are unable to operate continuously. The
RuTAG, IIT Delhi was approached by the Gramodyan Rachnatmak Vikash Sansthan, Deoria,
U.P. in December 2011, an NGO promoting this technology in the area, with the problems
people are facing in using these pumps for technical assistance. Following preliminary problems
were acknowledged from the interaction:
Lot of stress on the knees and lower upper side of the muscles of the feet was felt by the
users.
The rubber washer, which is used to provide a tight seal between the piston and cylinders,
had to be replaced in 15-20 days which increases the maintenance cost substantially as
one washers are 60 Rs./Pair
Foot stroke length is short, which makes it uncomfortable for people to use.
These problems arise due to the lack of proper analysis and research of the device used by these
farmers. These pumps are manufactured by the local mechanics which are based on their
empirical knowledge [3]
. These mechanics have replicated the pump design used in other
countries without considering the native conditions and the requirements of the users.
No prior attempts were made to solve the specific problem we had. Prior attempts made in the
field of the treadle pump technology have been very much specific according to the place where
it has been used. The major areas of development have been towards changing the materials so
that the cost can be minimized. There have not been any attempts to develop the governing
equation which can relate different design parameters, input variables and the different
constraints with the performance. So we identified that as the area of our work and attempted to
create such a model which can not only solve the specific problem we had, but can also be
generalized by just changing the input conditions.
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1.4 Objectives
After identifying the above problems and understanding the prior attempts we formulated the
idea and the objectives of our project which we planned to accomplish and which are following:
Study of the different designs of the treadle pumps which have been developed in
different countries. Their basic mechanisms, design parameters, performance
characteristics.
Analysis of the design that is used in the U.P.
Develop a general design optimization equation and model
Propose a new design, which overcomes the specific problems faced by the farmers in
U.P., India, and is more efficient and ergonomically comfortable.
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Chapter 2
Literature Review
The problem that we attempt to solve is very specific and there has been no direct attempt to
solve the same problem faced by the farmers in India. There have been studies on the treadle
pumps but almost every one of them has been done on either the pump used in Bangladesh or the
African countries, and in no study there has been any attempt to develop a generalize design
optimization equation which have been a major focus area of our project and by this approach
only we have tried to solve our problem. Also prior studies have been majorly focused upon the
doing the experimentation work on a particular pump, for a particular place and collecting data
for that. So what we have reviewed from these studies is to develop a basic understanding of the
mechanism, all the design features, ergonomics and to get the range of values as the input for our
design optimization model.
Our literature review deals with the following studies:-
1. ‘Treadle Pump -A human-powered pump for small scale irrigation in Developing Countries’
prepared for The Ramat-Warwick Linkage Programme.
2. Treadle Pumps for irrigation in Africa by Melvyn Kay and Tom Brabben, IPTRID
In these studies experimental range of values for different design features have been identified
which we have used as a base for our design optimization value. A comparative study has also
been done from the above literature of different pumps developed in history around the world.
2.1 Pump Design Features
Pump output requirements of discharge rate and pressure must be matched with the mechanical
components, such as the diameter of the pistons, their stroke length, the weight of the operator
and the cadence – the frequency with which the treadles are pushed up and down. The process
of design also requires to account for the wide variations of possible pumping needs of different
sites and the wide range and ability of operators, who must be comfortable when using the pump
and not bent over in some awkward uncomfortable position. The main pump design features are:
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Human Power
It is generally accepted that a reasonably fit, well fed human being between 20 and 40 years old
can produce a steady power output of around 75 watts for long period. This may not be the case
in many developing countries, so a more realistic output may be around 30 to 40 watts [4]
.
Pump Ergonomics
Ergonomics is the science of matching people with machines – in this case matching operators
with treadle pumps. In this way, the pump component sizes and dimensions are chosen to get the
best out of the human power input and ensure that the pumps are comfortable to operate. If the
parameters of stroke length, treadle spacing and the cadence are matched with the ability of the
operator, the operation of treadle pump becomes a very natural motion for the human body, and
can be sustained for hours.[2]
Piston/Cylinder Diameter
Pistons and cylinder diameters range between 75-150 mm, with 100 mm being a common choice
[2]. Piston diameter puts an upper limit on the pressure that can be achieved.
Foot Stroke Length
The foot stroke length is the vertical distance between the feet when one foot is raised and the
other is at its lowest point. If the stroke is too short, the leg muscles tire quickly, if it is too long,
the leg muscles are straining. A stroke length of 100-350 mm is a typical range [2]
.
Foot Force
For comfortable pumping, the downward force on the treadle should not exceed 50 percent of the
operator’s weight and not more than 70 percent for short periods. For the pump to be suitable for
men, women and children and for a range of pumping heads, it should be designed for a foot
force of 15-50 kgf (150-500N) [4]
.
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Mechanical Advantage
The ratio of the distance of the operator and the piston from the pivot point is known as the
mechanical advantage. It is also known as leverage as you can get greater force at the piston by
applying less foot force and leverage the pivot position of the treadles. Suggested mechanical
advantage ranges between 0.5 and 4 [1]
.
Cadence
Cadence is the average frequency by which a person can apply force during the treadle action is
known as the cadence. The cadence up to 60 cycles per minute is a comfortable speed for most
operators [4]
. It determines the discharge of the pump.
2.2 Modifications in treadle Pumps
There are many treadle pumps in use throughout the world. Many designs have been modified
from the early Bangladesh model to take advantage of local conditions and materials [4]
.
Bangladesh ‘Tapak Tapak’ Pumps
IDE Pumps-Zambia
Masvingo Pumps-Zimbabwe
Enterprise Works Pumps-The Niger
ApproTec Pumps-Kenya
Swiss ‘concrete’ Pumps
All of the types described above use the same operating principle yet they have some little but
very important differences. Different types of materials have been used in these like bamboo
and metal in TT pumps, PVC in IDE Pumps and Swiss pumps. Also some differences arise in
terms of the material of the piston cups like leather or PVC. Some modifications are also done
in order to adapt according to the ground water level and the topography of the land. Like in
Bangladesh water tables are high and the land are plane so the pressure required to lift the water
is low in turn the force applied by the operator is low which is achieved by using large diameter
cylinders and larger stroke length. The situation is opposite in other pumps where the water
tables are not so high and the pressure requirement is the prime concern. Also the Approtec
12 | P a g e
and the Swiss pumps use rocker arms instead of the pulley and the rope system which is used in
all other pumps.
2.3 Performance Characteristics
Pumps are normally described by their hydraulic performance, which indicates the discharge
and pressure that can be expected for the effort (or power) put in. For treadle pumps, this is not
an exact science because of the difficulty of standardizing the power input, which depends on
the physical strength of operators and their ability to sustain this power over a period of time.
Comparison between pumps from different suppliers is also made difficult because of
differences in design, e.g. material used, dimensions of components and standards of
workmanship. Moreover, the methods of testing under which the aforementioned pumps have
been tested are different. Thus, comparison of different treadle pumps is circumstantial and
depends on a no. of factors (human factors, terrain, water level etc.). Table below shows some of
the performance characteristics of different pumps [4]
.
Table-1: Performance characteristics of different type of treadle pumps
Item Piston
Diameter
(mm)
Stroke
Length
(mm)
Volume
per Stroke
(L)
Maximum
Suction
Head (m)
Maximum
Delivery
Head (m)
Maximum
Total Head
(m)
Bangladesh
Suction
76-178
290
1.2-1.7
5
0
5
Zambia
Suction
Pressure
89
100
300
300
1.8
2.25
8
6
0
7
8
13
Zimbabwe
Pressure
100
290
2.2
8
0
8
The Niger
Suction
Pressure
100-150
100
250
250
2.3-4.2
2.3-4.2
6
6
-
2
-
8
Kenya
Suction
Pressure
121
121
121
73
1.3
0.8
6.5
6.5
0
8.5
6.5
14
Switzerland
Suction
110
300
2.2
-
-
-
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2.4 Scope of the present work
After the identification of the problem and reviewing the literature carefully we formulated our
objective and the methodology. Our primary objective was to suggest the improvements in the
current treadle pump design. Since there was no analysis of the current device we decided to
first analyze the design theoretically so our approach was computational. After analyzing the
current device, our work was focused toward developing a design optimization model and then
using this model we suggested the improvements in the design according to the requirements of
our intended beneficiaries. We identified all the design features, ergonomic constraints
according to the Indian conditions and modeled them in to an equation and got the optimized
result by an iterative process. We could have approached our problem in different manner by
trying to design a new mechanism and analyzing it but because the adaptation of that new
device would have been a major challenge as told by the farmers, we didn’t focus on it much. So
we focused majorly on suggesting improvement by keeping the existing mechanism.
Work elements in the projects are as under:-
1. Literature Review
2. Theoretical Review
3. Identification of the requirement and constraints of the farmers
4. Identification of the design features
5. CAD modeling of current device
6. Development of a design optimization model
7. Suggesting a new design
8. Study of an alternative mechanisms
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Chapter 3
Development of a Mathematical Model
3.1 Nomenclature
---------------------------------------------------------------------------------
---------------------------------------------------------------------------------
---------------------------------------------------------------------------------
---------------------------------------------------------------------------------
Figure-1: Schematic diagram of the pump in motion
Abbreviations
lr - Length of the riser
lp- Piston stroke Length
WT- Water Table
y- Displacement from the bottom-most point attainable by piston
Mp- Mass of Piston
ρ- Density of water
Ap- Cross-section area of the piston
dp- Diameter of the piston
WT
lr
lp
y
Cylinder
Piston
Riser
Manifold
15 | P a g e
lf - Foot Stroke Length
Fp- Force at piston
Q- Flow rate from the pump
Cadence- No. of cycles per minute
Ff - Force applied by foot at the treadle
I – Inertia of a single treadle about the pivot point
Mt – Mass of a treadle (pedal)
ap- Acceleration of piston
ar- Acceleration of water in the riser
vp- Velocity of piston
vr- Velocity of water column in riser
vf- Velocity of foot while operating the treadle
f – Friction force between leather seal and cylinder
Cd – Coefficient of drag
Fs- Suction Force on piston
MA- Mechanical Advantage
Lt- Length of a treadle
3.2 Assumptions
1. All drag forces, including the drag in the riser and cylinder, along with that across the valves
have been neglected.
2. The friction force between the leather seal and the cylinder has been neglected.
3. All frictional losses in the revolute joints in the mechanism have been neglected.
4. All links in the treadle pump mechanism are considered to be rigid.
We can divide the motion of a piston in two stages, one where the piston moves upwards, and the
other comprising of its downward motion. As the upward stroke requires much more power and
peak force than the downward stroke, we will focus our attention to the upward stroke only.
16 | P a g e
Upward Stroke Downward Stroke
Figure-2: Stages of operations
3.3 Governing Equations
For a piston going up,
.Mp g . .( ).Ap lp y g
Figure-3: Free body diagram of the piston
Therefore, we get
( . .( )). ( . .( )).Fp Mp Ap lp y g Fs Mp Ap lp y ap -(1)
Now, suction force acts on the water column in the cylinder below the piston and the water
column in the riser to impart it sufficient acceleration to fill the vacuum created just below the
piston.
ap
Fp
Fs
17 | P a g e
Therefore,
( . . . . ). . . . . . .Fs Ap y ArWT g Ap y ap Ar lr ar -(2)
Adding (1) and (2), we get
. . . . . . . . . . . . . .Fp Mp g Ap lp g Ap y g Fs Mp ap Ap lp ap Ap y ap
i.e., . . . . . . . . . . . . . .Fp Mp g Ap lp g Ar lr ar ArWT g Mp ap Ap lp ap
i.e., . . . . . . . . . . . . . .Fp Mp g Ap lp g Ar lr ar ArWT g Mp ap Ap lp ap
i.e., .( ) . . . . . . . . . . . .Fp Mp ap g Ap lp g Ar lr ar ArWT g Ap lp ap
i.e., . .
.( ) . . .( . . )Ar ar lr Ar ap lp
Fp Mp ap g Ap g lp WTAp g Ap g
-(3)
Now, applying continuity equation, we get
. . . .Ap vp Ar vr
Differentiating both sides with respect to time, we get
. . . .Ap ap Ar ar
i.e., ( ).Ap
ar apAr
-(4)
Applying equation (4) in (3), we get
. .
.( ) . . .( . )ap lr Ar ap lp
Fp Mp ap g Ap g lp WTg Ap g
-(5)
For a treadle,
Figure-4: Free body diagram of treadle
Fp Ff Mt
g
Lt
cg
x
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Writing moment-balance equation for the treadle, we get
.( ) . .( ) . .Ff Lt x Mt g cg x Fp x I -(6)
ap
x
Here, we also define Mechanical Advantage as Lt x
MAx
Then, we have
.lp MA lf
vp vf
x Lt x
i.e., .vf vp MA
3.4 Analysis of the Current Design
dp= 110 mm= 0.11 m
Lt= 600 mm= 0.6 m
MA= 2
x= 0.2 m
lf= 200 mm= 0.2 m
lp= 100 mm= 0.1 m
lr = 10 m
WT =9.9 m
Mp=1.15 kg
Mt=3.23 kg
Inner diameter of the riser = 0.045m
23 2.(0.045)
1.59*10 m4
Ar
0.156 3.233*(0.2 ). | 0.2 |I x x
Figure-5: CAD Model of the current system
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Now, we assume
.(1 sin( ))
2
lp ty
, where 2 . / 60Cadence -(7)
lpat t=0, y=
2
3at t= , y=0
2
5at t= , y=0
2
Thus, the upward stroke is for 3 5
t={ 2 , 2 }2 2
n n
From the above function for displacement used, we get
. .cos( )
2
lp tvp
-(8)
2. .sin( )
2
lp tap
-(9)
Now,
Keeping Lt, Ar and lr same as the present design, using (8) and (9) in (5), we get
2 2 2 2
.sin( )
, 39. . 156 9810. . 15.6*
, 19.5* . . 4905. . . 490.5* . .
Fp A B t
where A Ap g Ap lp lp
and B Ap lp Ap lp lp Ap
-(10)
From (10) and (6), we get
2
' '.sin( )
. 31.7* 10.3 , '
0.6
. . . , '
0.6 2. .(0.6 )
Ff A B t
A x xwhere A
x
B x I lpand B
x x x
-(11)
20 | P a g e
Then,
0
0
( )
= . dt
. .cos( ) = ' '.sin( ) .( ) .(MA) dt
2
Energy consumed in one stroke for one cylinder
Ff vf
lp tA B t
With our assumed function, combinations of Ap and lp arise for which Ff becomes negative,
which is not possible practically. Thus, we will integrate the function for only positive values of
Ff.
Therefore, we get
A'>B'
(in one upward stroke) '.
If
Energy A lp
2 2
2
A'<B'
' ' ' (in one upward stroke) '. . . .(1 )
2 ' 2 4 '
If
lp A lp B AEnergy A lp
B B
-(12)
. ( )
P=
Av Power consumed in one stroke for one cylinder
Energy
-(13)
2. . .
, 60
lp Ap CadenceFlow Rate Q
Using above analysis for our present design, we get
21 | P a g e
lf
(mm)
MA dp
(mm)
Cadence
(cycles/minute)
Q
(m3/sec)
Ff
(N)
P
(W)
200 2 110 30 0.94 98 14.8
200 2 110 35 1.10 107 17.2
200 2 110 40 1.26 117 19.7
200 2 110 45 1.42 128 22.1
200 2 110 50 1.58 141 24.6
200 2 110 55 1.74 155 27.1
200 2 110 60 1.90 170 30.1
Table-2: Calculation of foot force and power for various cadences for the current design
From literature, we know that an average power of 30-40 W can be provided by an adult treadle
pump operator for long hours. Thus, we can select the present design being operated at
cadence=60.
Then, taking cues from literature, the parameters dp, lf, MA and cadence were varied across the
following range:
Minimum Maximum
dp (mm) 75 150
lf (mm) 200 230
MA 0.5 4
Cadence 30 60
Table-3: Ranges of allowable parameter variations
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3.5 Modifications in the current design
3.5.1 Maximizing Q [Ff<(Ff)present|P<(P)present]
lf
(mm)
MA dp
(mm)
Cadence
(cycles/minute)
Q
(m3/sec)
Ff
(N)
P
(W)
270 3 150 60 3.2 154.8 30
Table-4: System parameters of the new modified design for maximum Q
This condition corresponds to maximum output power condition, as
. . .( )Output Power Q g Total Head
In this configuration, we observe that lf and dp have been increased to increase Q. If all other
parameters are unchanged, it would require an additional power to suffice this change, which is
compensated here by the decreasing the cadence and increasing the mechanical advantage. The
peak foot force almost remains same for this configuration, as compared to present design.
Figure-6: Power (W) vs. piston diameter (mm)
0
10
20
30
40
50
60
70
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
Power @ MA=2, lf=270mm
Power @MA=3, lf=270mm
Power @ MA=2, lf=200mm
Power @ MA=3, lf=200mm
23 | P a g e
Figure-7: Discharge Rate (m3/s) vs. piston diameter (mm)
3.5.2 Minimizing Ff [Q>(Q)present|P<(P)present]
lf
(mm)
MA dp
(mm)
Cadence
(cycles/minute)
Q
(m3/sec)
Ff
(N)
P
(W)
250 4 150 60 2 80 16
Table-5: System parameters of the new modified design for minimum Ff
This condition corresponds to minimum effort condition. In this configuration, we observe that
MA has been increased to its maximum allowable value to decrease foot force, but if all other
parameters are unchanged, this should reflect as decrease in Q. To compensate for reduction in
flow rate, lf and dp have been increased adequately. It should also be realized that as the
mechanical advantage is increased, the unsupported length of the treadle increases, increasing the
bending moment, and thus, the resulting bending stresses. Therefore, strength of the treadle
should also be taken into consideration before increasing MA.
0
1
2
3
4
5
6
0 20 40 60 80 100 120 140 160
Q @ MA=2, lf=270mm
Q @ MA=3, lf=270mm
Q @ MA=2, lf=200mm
Q @ MA=3, lf=200mm
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Figure-8: Variation of Force (N) vs. piston diameter (mm)
Figure-9: Plot of discharge Rate (m3/s) vs. piston diameter (mm)
0
50
100
150
200
250
300
350
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
Force @ MA=2,lf=260mm
Force @ MA=4,lf=260mm
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 20 40 60 80 100 120 140 160
Q @ MA=2, lf=260mm
Q @ MA=4, lf=260mm
Q @ MA=2, lf=200mm
Q @ MA=4, lf=200mm
25 | P a g e
5.6 Other suggestions to improve performance
5.6.1 Use of Y-Manifold
In our present design, the manifold being used is rectangular in shape. If the shape of the
manifold is made like a Y-junction, it would result in lesser minor losses, hence
increasing the efficiency of the pump.
5.6.2 Use of spring
During operation of the pump, every time treadles reach the extremes of their allowed
motion, they have to be controlled by the operator in order to make them stop and change
direction. It requires a certain amount of skill. Unskilled treadle pump operators aren’t
able to control the motion of the treadle, and let it collide into the ground, stopping with a
jerk. It results in considerable amount of energy loss and discomfort to the operator.
Hence, if springs are attached at the lower extreme of the treadle motion, this jerk can be
prevented and it would result in a smoother, efficient motion.
Current Design Proposed Design
Spring
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5.6.3 Variable positioning on treadles
In the current design, an operator can stand only at a specified place on the treadle,
irrespective of his/her height, weight etc. If a person operating the pump is more
comfortable in applying more force while traversing a shorter stroke length, he/she
doesn’t have that choice. Thus, if treadles are manufactured with multiple places to stand
on it, it would become more comfortable to operate for all kinds of people.
5.6.4 Use of NRV at riser
In the current design, every time the pump is operated, it has to be primed. It can easily
be managed by installing a non-return valve at the bottom end of the riser so that water
does not go back into the aquifer when the pumping stops, and stays in the riser. Though,
it will add to the head loss in the pump, it would make it more comfortable for the
operator.
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Chapter 4
Preliminary Analysis of a new alternate mechanism
Figure-10: CAD Model of a new design using a different mechanism
This design is basically a vertical slider crank mechanism. The rationale behind this design is the
ease and comfortability with which bicycles can be operated. Arrangements can be made in this
design, so that the pump is operated by attaching a bicycle with it, used to provide crank rotation.
For our purposes, we have considered (based on our Q-maximising configuration)
Crank length, l2 = 135mm (lies in the optimum range for long distance cyclists)
Connecting rod length, l3 = l2/(sin ϒmax) where, ϒmax = maximum transmission angle
l3 = 270 mm (ϒmax = 30°)
l3 = 210 mm (ϒmax = 40°)
l3 = 176 mm (ϒmax = 50°)
Cylinder Diameter, dp =150 mm
Stroke, lp = 2.l2= 270 mm
28 | P a g e
Now,
To compare with the current design, all other parameters i.e. Mp, Mt, lr, WT are taken to be same
as the current design. Then, the required cadence which will provide same flow rate as in the Q-
maximizing condition with the earlier design is calculated.
Cdreq = 60.(90/270) cycles/min. =20 cycles/min
Figure-11: Schematic diagram of slider crank mechanism
The acceleration of piston depends on the angular velocity and joint angles of the mechanism,
which would then decide the suction force generated opposing the piston motion in the upward
stroke.
22 2 22
3
2 .cos 2 cos .sin 2 sin2.cos 3.sin . . .
3.cos 3 cos 3 cos
l l lap l l
l l l
Then, the torque to be applied at the crank is
.tan . 2.cos 3.cosFp l l
θ ϕ
θ
l2 l3
29 | P a g e
Figure-12: Power (W) vs. crank angle (θ)
Figure-13: Force (N) vs. crank angle (θ)
0
50
100
150
200
250
300
0 50 100 150 200
Power (30)
Power (40)
Power (50)
0
100
200
300
400
500
600
700
800
900
1000
0 50 100 150 200
Ff (30)
Ff (40)
Ff (50)
30 | P a g e
For upward stroke,
(Power)max = 214 W (for ϒmax = 30°)
(Ff)max = 720 N (for ϒmax = 30°)
(Power)avg = 118 W (for ϒmax = 30°)
Thus, it can be seen that the maximum force and average power to be applied in this mechanism
is higher than that required in the earlier design, but the ergonomic efficiency of this design is
expected to be higher in this design. Hence, a detailed analysis of this new design is required to
comment on the advantages/disadvantages of this mechanism over the other one.
31 | P a g e
Chapter 5
Conclusion
Some modifications in the existing design have been suggested by properly analyzing the all the
design features and constraints. These modifications will reduce the human power and force
requirement to get the same amount of the discharge rate as before and at the same time will be
ergonomically more effective. A design optimization model have been developed which can
generalized by the people around the world according to their ergonomic conditions, water
tables, head requirement, land topography etc. Preliminary level analysis of an alternative
mechanism have also been done but could not be done extensively because of the time
constraints which leaves the scopes for the future. The following aspects could not be analyzed
which leaves scope for the future:-
Prototype building of the new system with the new suggested modification can be
done and then performance analysis can be done by extensive experimentation.
New alternative mechanism designs can be extensively analyzed and best suitable
design can be selected among them and the similar process can be repeated for this
also.
An extensive material analysis is also needed
These are some areas which were identified and will be continued as part of the BTech
Project next year.
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References
[1] Book-The Treadle Pump Manual, Irrigation for Small Farmers In Bangladesh by Alastair Orr A. S. M.
Nazrul Islam Gunnar Barnes pg.- 1-50
[2] ‘Treadle Pump -A human-powered pump for small scale irrigation in Developing Countries’ prepared for
The Ramat-Warwick Linkage Programme.
[3] RuTag IIT Delhi Field Survey
[4] Treadle Pumps for irrigation in Africa by Melvyn Kay and Tom Brabben, IPTRID
