International Journal of Scientific & Engineering Research, Volume 6, Issue 2, February-2015 81
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Design and Fabrication of an Adaptive Left Throttling Pedal for V-Boot Wagon 230 for Right LEG Paraplegic Patient
S. P. Ayodeji*, A. M. Yakubu and O.J. Fasan
Department of Mechanical Engineering, Federal University of Technology Akure, Ondo State, Nigeria
*Email of Corresponding Author: ayodejisesan@yahoo.com
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Anthropometry has been defined as the study of the measurement of the human body in terms of the dimensions of bone, muscle, and adipose (fat) tissue (National Health and Nutrition Examination Survey III, 1988). In making life comfortable for human being through engineering innovations and inventions, the physically challenged human beings must not be left out. The left foot accelerator pedal (LFAP) is an inexpensive low-tech device commonly prescribed by driver rehabilitation specialists to allow persons who cannot use their right foot to operate a motor vehicle. Persons with amputations or right hemiplegia from any number of causes (such as traumatic nerve or muscular damage, post polio effects, stroke, multiple sclerosis, arthritic damage and others) benefit from this automotive adaptive aid.
The ability to drive a motor car can radically alter the quality of life led by disabled people as inability to drive causes brooding and frustration when they cannot do a useful day's work or occupy themselves. Well-advised disabled drivers can drive to offices, shops, pubs, and cinemas without the need of a helper (Tachakra, 1981). The
objective of this work is to report the design and
fabrication of an adaptive left throttling pedal for v- boot wagon 230 for right paraplegic patient. This is based on collected information to determine the need for standards or guidelines to govern the design, manufacture, installation, prescription and use of Left Foot Adapted Pedals (LFAPs) in a safe manner.
In order to achieve the set objectives of this research work, the following factors were considered.
Anthropometric data of the client (paraplegic patient) was taken.
(1) Physical dimensions of available spaces for left throttle adaptor were measured.
(2) Design analysis which includes adaptive link mechanism, material selection, strength, forces, moments and angle of depression were determined.
(3) Fabrication, machining of parts and
assembling were based on the required standards and specifications
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(4) Installation of the fabricated throttle adaptor.
(5) Performance evaluation at the point of use.
The following instruments were used
(1) Body measurement sheet
(2) Metre Rule
(3) Tri-square
(4) Vanier Calliper
(5) Set squares
(6) Pencil
(7) Eraser
Anthropometric data of the Client
The measurements were limited to the use of metre rule, measuring tape, body measurement log sheets and sitting height pictures.
(1) The client or patient was asked to sit conveniently on his car as if he is about to drive.
(2) The patient’s head is maintained in the
Frankfort Horizontal Plane position.
(3) The left leg of the patient is positioned so that the skin can be marked for thigh and calf measurements.
(4) The figure 1 shows the exact positions and dimensions of the dynamic parts required for effective driving.
(5) All dimensions in millimetres.
Shear force Distribution on the link rod
SF= W
Bending Moment, Mb = -WL (1)
Where: W is the human effort on the foot pedal and
L, is the length of the rod; Deflection on the link is given by
(2)
I = (3)
This is given by the relationship;
σE = (4) Where
Ar = crossectional area of the rod
σE = axial tensile stress
This is obtained by the relationship,
(5) Where;
Mb = Bending moment acting at the given section
b = Bending stress
y = Distance from the neutral axis to the extreme fibre
Therefore bending stress,
(6)
Pi = 2840 d (7)
Where;
Pi = Initial tension on the bolt
d= Nominal diameter of the bolt
Stress Area on the bolt, As of size M8 is given by As = (8) Where;
dp = effective pitch diameter dc = core diameter
dn = Nominal diameter
Ls = As x Ps (9) Stress build-up, to initial tightening is calculated thus,
= (10) Torsional shear stress caused by the frictional resistance of the threads during tightening is given by;
τs = (12) Where;
τs = Torsional shear stress
T = Torque transmitted during shaft coupling
Where;
T = n b db
2.τs x Rb
(13)
E = Modulus of elasticity
I is the Moment of Inertia, I for solid shaft is given by
n b = Number of bolts
Rb = radius of bolt circle
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The weld is subjected to shear and the weld shear strength is limited to just about half the weld metal tensile strength. For intermediate weld positions, the value of strength and ductility show intermediate values.
Circular fillet weld subjected to bending moment
Maximum bending stress on the welded parts
σb (max) = (14)
( Khurmi and J.K Gupta, 2005)
Where M = Bending moment on the rod (Nm)
s = size (or leg) of weld
d = diameter of the rod. In this case,
Maximum shear stress occurring at the throat is given by;
τ tmax= (15) ( Khurmi and J.K Gupta, 2005)
Where T is the torque transmitted in Nm, s = size (or leg) of weld, and
L= length of the weld
The car was fueled and started to read a number of various engine speeds with the corresponding pedal displacements from idle position. Table 6 shows the tabulated reading of engine Speed in RPM with its corresponding displacement in millimeters.
The car was also fueled and ignited in order to read a number of various engine speeds with the corresponding pedal displacements from idle position. Table 7 shows the reading of engine Speed in revolution per minute with its corresponding displacement in millimeters.
The engines speed runs 2000rpm at an idle position of the existing pedal as shown by the red line in Figure 8 compared to the adapted pedal which runs at 1500rpm. This low speed indicates improved efficiency and minimizes fuel consumption. Also
when the two pedals were activated and pressed through an arc length of 45mm, both engine speeds read 6000rpm. Although there were little deviations in the curves at displacement position 20mm and
30mm respectively. These deviations have no significant effect on the performance of the engine.
The Left Foot Adapted Pedal, LFAP design and fabrication were based on the anthropometric data of the client,
evaluating the performance of the existing pedal as basis for functionality comparison .The above facts have been justified by using the design parameters to fabricate the project. Revolution of engine speed of 6000rpm through 45mm displacement arc of left foot pedal was achieved as compared with the existing pedal. Since Engineering is all about problem solving and making life comfortable for people, this design goes along way putting smile in the face of disables who intend to drive himself around with ease.The left foot accelerator pedal (LFAP) is an inexpensive low-tech device commonly prescribed by driver rehabilitation specialists to allow persons who cannot use their right foot to operate a motor vehicle. The LFAP is a mechanical adaptive device that allows left foot operation of the accelerator. This device transfers the throttling mechanism on the right side of the vehicle throttle pedal to the right. This work was initiated in response to a Right Leg Paraplegic Patient (RLPP) coupled with the Supervisions to conduct technical and ergonomics evaluations of the LFAP to determine the degree to which this adaptation could be better compared with the existing right foot pedal. Although great progress has been made by manufacturers and mobility equipment dealers in the field of automotive adaptive devices, the performance and safety of LFAPs is not currently regulated by Nigeria standards or guidelines.
[1] Andras V. (2002): Speed Regulation in Car Active Accelerator Pedal, IATSS Research Journal Vol. 26(2), Pp 5, Department of Technology and Society, Lund University, Sweden.
[2] Jae Yonglee (2010): A Novel Design of
Active Accelerator Pedal using Linear
Electromagnetic Actuator, A Journal of
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Mechanical Science and Technology (2010) Pp 3, Department of Mechanical Engineering, Yeungnam University, Korea.
[3] James, C. Patry and Suanne, L. (2000): Left Foot Accelerator Pedal Evaluation, A Journal of Mechanical Science and Technology (2000), Pp71-80, and Transportation Development Centre, Canada.
[4] John Fulland and Bjorn Peters (1999): Regulation and Routines for Approval of Passenger Cars Adaptor to Drivers with Disabilities, VTI Rapport (447), Pp 35, National Road and Transport research
institute, Sweden.
[5] Khupantavee, N and et’ al (2008): A meaning of Well-being, Experience of Paraplegic Thai people, A Medical Journal of Human Science Vol. 12, Pp 3, Department of Medical Nursing, Faculty of Nursing, Prince Songkla University, Hat Yai, Songkhla.
[6] Khurmi, R.S. and Gupta, J.K. (2005): A Textbook on Machine Design, First Multicolour Edition.
[7] Tachakra S. (1981): “The Needs for the
Disables” A British Medical Journal Vol.
283, Pp 25, British.
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Fig 1: Anthropometric data of the patient taken and used for the design
Fig 2: Position of the Driver on Vee-Boot Wagon Mercedes 230
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` Fig 3: Static Loading Diagram
Fig 4: Shear Force Diagram
Fig 5: Bending Moment Diagram
Fig 6: Performance Evaluation of the existing Pedal
Fig 7: Performance Evaluation of Adapted Pedal
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Table 1: Results of design analysis of the component parts of adapted left foot pedal
S/No | Parameter | Abbreviation | Value | Unit |
01 | Shear force Distribution on the link rod | W | 22.00 | N |
02 | Modulus of elasticity | E | 200.00 | N/mm2 |
03 | Rod length | L | 230.00 | mm |
04 | Deflection | 0.90 | mm | |
05 | Moment of Inertia for solid shaft | I | 4.909E-10 | m4 |
Table 2: Results of design analysis for axial tensile stress on the link
S/No | Parameter | Abbreviation | Value | Unit |
01 | Diameter of the link shaft | d | 10.00 | mm |
02 | Crossectional area of the link shaft | Ar | 7.855E-9 | m2 |
03 | Axial tensile stress | σE | 2.80 | N/mm2 |
Table 3: Results of design analysis for bending stress on the link rod
S/No | Parameter | Abbreviation | Value | Unit |
01 | Bending moment acting at the given section | M | 5.06 | Nm |
02 | Bending stress | b | 51.54 | MN/m2 |
03 | Distance from the neutral axis to the extreme fibre | y | 0.01 | m |
These values of axial stress and bending stress on the link rod form the basis for fastening selection and
welding design analysis.
Table 4: Results of design analysis for safe tensile load on the bolt during tightening
S/No | Parameter | Abbreviation | Value | Unit |
01 | Nominal diameter of | d | 8.00 | mm |
02 | Effective pitch diameter | dp | 7.19 | mm |
03 | Core diameter | dc | 6.47 | mm |
04 | Nominal diameter | dn | 8.00 | mm |
05 | Initial tension on the bolt | Pi | 22.72 | N |
06 | Stressed area on the bolt | As | 36.6 | mm2. |
07 | Permissible stress on the selected bolt | Ps | 60.00 | MN/m2 |
08 | Safe load on the bolt | Ls | 2.20 | KN |
09 | Stress build-up, to initial tightening | 0.69 | MN/m2 | |
10 | Torsional shear stress | τs | 12.20 | MN/m2 |
11 | Torque transmitted during shaft coupling | T | 0.65 | Nm |
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Table 5: Results of design analysis for safe tensile load on the bolt during tightening
S/No | Parameter | Abbreviation | Value | Unit |
01 | Maximum bending stress on the welded parts | σb (max) | 9.12 | MN/m2 |
02 | Bending moment on the rod | M | 5.06 | (Nm) |
03 | size (or leg) of weld | s | 0.01 | m |
04 | diameter of the rod | d | 0.01 | m |
05 | Maximum shear stress occurring at the throat | τ tmax | 0.31 | MN/ m2 |
06 | length of the weld | L | 0.03 | m |
Table 6: Readings obtained from testing the Existing Pedal
S/No | Engine Speed100(RPM) | Displacement of pedal from neutral position (mm) |
01 | 20 | 0 |
02 | 32 | 20 |
03 | 44 | 30 |
04 | 60 | 45 |
Table 7: Readings obtained from testing the Adapted pedal
S/No | Engine Speed100(RPM) | Displacement of pedal from neutral position (mm) |
01 | 15 | 0 |
02 | 30 | 20 |
03 | 45 | 30 |
04 | 60 | 45 |
Table 8: comparison of existing pedal and adapted petal
S/No | Engine Speedx100(RPM) Before | Engine Speedx100(RPM) After | ||
1 | 20 | 15 | ||
2 | 32 | 30 | ||
3 | 44 | 45 | ||
4 | 60 | 60 | ||
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