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IOSRD El-Bow power transmission

Simple perpendicular power transmission element.
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IOSRD International Journal of Engineering
Volume 1, Issue 2, December 2014, Pages 71-77
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Design and development of EL-BOW power transmission
Devchander V1*, Karthikeyan S2, Sathyavrath R3 and Surendhran K4
1, 2, 3, 4
Department of Mechanical Engineering, Vel Tech High Tech Dr.RR Dr.SR Engineering college, India
*Corresponding author email address:
Abstract: This project “Design and development of El-bow power transmission” is simple and portable, hence skilful and has practical
influence in transferring power at right angle without any gears. The El-bow Mechanism transfers the driving power towards the driven
side in such a way that the angular forces produced in the holes are transferred with the help of el-bows which takes the driving power and
the right angle drive is transferred towards the output slack and rod assembly. Hence a little friction occurs while the power is being
transferred. Both hunting and back lash errors are absent. Therefore, an efficiency as high as 90-92% are possible in EL-BOW
transmission mechanism. Nowadays world requires speed in each and every field, hence rapidness and quick working are very important.
It is a working project and have guarantee of success. This project gives us knowledge, experience, and unique idea about manufacturing
Keywords: Bent links, El-bow, Perpendicular power transmission.
1. Introduction
It is a working project and can be manufactured in very short span of time. Hence we have selected this project. El-bow
power transmission is an ingenious link mechanism of slider and kinematic chain principle [2]. This mechanism is very
helpful for transferring motion at right angles. However in certain industries it can also work at obtuse or acute angle plane
and may be compared to worm and worm gear or bevel and pinion gear which are mostly used in the industry for various
applications. The important feature of this mechanism is comparatively high efficiency between the driving and the driven
power shafts with regards to gear efficiencies.
2. Literature survey
The most commonly used type of gear profile is involute [1]. They are used for cylindrical spur and helical gears as well as
for conical gears like beveloid, hypoid and spiral bevel gears. Some properties of involute [1] (cylindrical) gears that had
made them so unique are: Uniform transferring of rotational motion, independent of small error in Centre distance. The sum
of the contact forces are constant and the direction of the total contact force always acts in the same direction. An involute[1]
gear can work together with mating gears with any number of teeth. Manufacturingis comparatively easy and the same tools
can be used for machining gears with any numbers of teeth (Applies to hobs, shaper cutters, grinding worms, shaving cutters,
but not to profile tools like milling cutters and profile grinding wheels). If the gears are perfectly rigid and no geometrical
errors or modifications are present, the gears would transfer the rotational motion exactly, which means that a constant speed
at the driving shaft would result in a constant speed at the driven shaft. The idea of nil friction leads to that, the gears would
transfer the torque exactly. No force variations can exist and hence no vibrations and no sound (noise) will be generated. Of
course, at present, there are geometrical errors, deflections and friction present, and accordingly, gears sometimes generate
noise to such an extent that it becomes a quite problem.
-Author: Mats Akerblom
3. Working
This mechanism carries force through a el-bow. Transferring rotational motion around an axis generally involves gears,
which is complicated, inflexible, clumsy-looking and ugly. This mechanism converts rotational motion using a set of
cylindrical bars, bent to 90º, in a clever, simple and smooth way that transfers strong rotational force even in complicated
position.The cylindrical housing has one degree of freedom i.e.,(rotation), the bent link has one degrees of freedom
i.e.,(reciprocation). This condition is suitable for both driving and driven side. Initially when the drive is given at the input
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Volume 1, Issue 2, December 2014, Pages 71-77
side, the degrees of freedom of both cylindrical housing and bent links gets interconnected within one another and results in
rotational motion at the driven side.The El-bow mechanism transfers motions at any fixed angle between the driving and
driven shaft. This mechanism consists of number of pins that would be between 3 and 8, more the pins the smoother the operation is. Motion
is transferred from input to the output shaft through the el-bow which is bent to the angles between the input to output shafts.
These pins reciprocate inside hollow cylinders thus forming a sliding pair. Our mechanism has 3 such sliding pairs. Power is
supplied by an electric motor. Motion is transferred from input to the output shafts through the bent links which are bent to
conform to the angles between the driving and driven shafts. These bent links are located in the holes equally spaced in a
circle and they are free to reciprocate in & out as the shafts revolve. This type of drive is generally suitable where quite
operation at high speed is required. Even though this mechanism shows a perpendicular transmission, this drive can be
applied also to shafts located at intermediate angle between 0* to 90*.In making this transmission, it is mandatory to have the holes for a
given el-bow located precisely in the respective holes and must be equally spaced in radial and circumferential directions. If
the holes are not drilled in the ends of the cylindrical housing i.e., “blind” or closed ends, there must be a small vent at the
bottom of each hole for the escape of air compressed by the pumping action of the el-bow. These holes can use for
lubrication purpose.
Fig.1 Mechanism
4. Machine design
Machine Design is an art of designing the structure of a machine. The resistive bodies with relatively constrained motions are
known as machines. A machine is used to convert other forms of energies into mechanical energy (or) to transmit the energy.
Modification of the existing design is to create new machines or structures and to improve the existing machines, to convert
and control the motions. To design a simple component successfully, a better knowledge in applied sciences is vital. Primary
knowledge about the strength, properties of material and metrology are essential. To determine the velocity, inertia force, and
acceleration of the number of links in motion, knowledge in the theory of machines is important. The mechanics of machine
are involved in the design.
5. Concept of the M.D.P.
The following considerations are to be made in a machine design:a. The different types of stresses and loads created by the load.
b. The kinematics of a machine (or) the motion of a part which depends on the type of motion, i.e. reciprocating, rotary, (or)
c. In selection of a material, factors such as strength, resistance to corrosion, machinability, durability and weight of the
material are to be considered
d. Size and form of the parts.
e. Resistance to friction an easy lubrication.
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Volume 1, Issue 2, December 2014, Pages 71-77
Operation economy.
Using standardized parts.
Manufacturing facilities which are available.
Machine making cost.
The number of products or machines to be manufactured.
6. Machine design-general procedure
While designing the machine the following steps are generally adopted,
a. A statement of problems specifying the purpose of the machine is prepared.
b. For the desired motion, the relevant group of mechanism is selected.
c. The force and energy on machine member is calculated.
d. Suitable and appropriate materials are selected.
e. The size of component drawing is determined.
f. The component drawing is prepared and sent for manufacturing.
g. Manufacturing and assembly of the machine.
7. Machine testing and testing for machine functioning
7.1. Shaft Design
7.1.1. Bending
Material forces which are developed on any cross-sectional area of the shaft give rise to stresses in each and every point. The
so called bending stresses are the result of the internal or resisting moment.
7.1.2. Torsion
When the shaft is turned or twisted in such a way that both the shaft' axis and the axis of the couple coincide with each other. The shaft undergoes pure
torsion and the resultant stresses at any point of the cross-section are either torsion stress or shear stress[3].
7.1.3. Combined Bending and Torsion
In practice the shaft is subjected generally to the combination of bending and torsional stresses. The bending stresses are due
Weight of the belt
Pull of the belt
Mounting eccentricity
Whereas the torsional movement might be due to, the direct or indirect twisting. Hence the shaft’s cross-section is
simultaneously subjected to both the bending and torsional stresses.
T= π/16 .τ.d3
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Volume 1, Issue 2, December 2014, Pages 71-77
Power of motor = ¼ H.P = 746 x .25 = 186.5 N-m/s
Speed of motor = 1440 rpm
T = 1.23 N-m = 1230 N-mm
Considering 25 % overload
Tmax= 1238 x 1.25= 1525 N-mm
Diameter =10.2mm
Taking factor of safety = 2
Diameter(D) = 10 x 2 = 20mm
7.2. EL-bow Design
Power of motor = ¼ H.P = 746 x .25 = 186.5 N-m/s
Speed of motor = 1440 rpm
T = 1.23 N-m = 1230 N-mm
Considering 25 % overload
Tmax= 1238 x 1.25= 1525 N-mm
Diameter =10.2mm
Taking factor of safety = 2
Diameter(D) = 10 x 2 = 20mm
Table 1. Materials used
Cylindrical Housing, Shaft
Bright drawn steel
High tensile strength
Stainless steel
Corrosion resistance, Wear resistance
Manganese, chromium alloy steel
Corrosion resistance, Wear resistance
Chromium or Nitrate coated steel
High wear resistance
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Volume 1, Issue 2, December 2014, Pages 71-77
7.3. Static Load Analysis
Fig.3. Shaft
8. Efficiency improvement
A sliding pair is formed between the rods and the cylinder transmits the main motion. The lapping and cleaning of pins have to be done and made
capable of providing total interchangeability and similarly with the cylinder which are to be honed or lapped in order to achieve smooth finish of the
surface. This will enable lesser frictional loss and also reduced heat generation.
9. Methods of cooling and lubrication
All sliding members require lubrication to reduce friction and a cooling process to reduce frictional heat. The simplest
technique to achieve the twin objectives is to drill oil holes in the body of the cylinder and fill them up with oil. But as the
weight and use of the cylinders increase this technique may not be effective.
10. Modifications for enhanced performance
Increasing the number of pins can enhance the efficiency and performance of the machine. We know from the working of the
mechanism, the drawing pin is the innermost pin that pins the mechanism. By reducing the number required for the next pin
to attain the innermost position, the performance of the mechanism as well as its life can be increased.To reduce the friction
developed within the holes and to achieve Point contact the following design can be implemented.
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Volume 1, Issue 2, December 2014, Pages 71-77
10.1. Implementation of Liners
Fig. 4. The main reason to implement liner is to reduce the wear in holes of cylindrical housing[5].
10.2. Implementation of rings
Fig. 5. In order to reduce the area of contacting surface, rings can be used. This will reduce the friction.
10.3. Exploded View of Liner and Ring Assembly
Fig. 6. Exploded View Of Liner And Ring Assembly
9. Applications
a. This mechanism is used in gang drilling machine.
b. It can be used in angular drilling machine.
c. This mechanism can be used for a drive at clumsy location.
d. It can be used in submarines for periscope movement.
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Volume 1, Issue 2, December 2014, Pages 71-77
According to many engineering studies, the books on the subjects have elaborated that the gear drives have mechanical
efficiency of very low level. Because of the factors relating under frictional forces between the mating gear teeth, the erratic
hunting of the gears and the resultant backlash between the teeth is impossible to overcome and hence the efficiency will not
exceed 55%. The recent gears of worm bevel type produced with Poly Propylene and Epoxy material, which eliminate the
frictional forces comparatively, but used only very small applications due to less than 42% efficiency.This project is only a
designed model. It has not been extensively researched or tested. But it is confidently felt that with improved manufacturing
techniques and modifications, the efficiency can be enhanced to a considerable extent.
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edition, 2008) 436.
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