design of hydraulic platform lift

8/12/2019 Design of Hydraulic Platform Lift

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Design of hydraulic platform lift 2013

Bishoftu Automotive Industry Page 1

Chapter one

IntroductionBefore the invention of weight lifting device such as screw jack, hydraulic jack, crane, etc., the early man

apply a crude way of lifting objects to great heights through the use of ropes and rollers, which was

mostly applied in the construction industry, where, it was used to raise mortar (cement, sand & water).

After industrial revolution, with the advent of automobile, the automobile industry was also faced with

the challenge of load lifting, because of the backlines of some automotive parts. Because of the interface

between the automobile and human lives, there is need for standardization of its component part improves

its performance, efficiency and reduces failure. For this reason car has to be taken during maintenance of

its component parts.

Because every machine is subjected to failure, maintenance is essential parts in handling machines. Fromtime to time the need to improved and lasting maintenance has increased in the automotive industry in an

attempt to reduce cost, for its reason, maintenance of vehicle needs to be efficient and reliable.

To keep good quality of maintenance and to create good working conditions for the workers a convenient

and easy way should be provided to identify and fix the problem. This report presents the study of a

hydraulic platform lift.

1.1 Problem Statement

In Bishoftu Automotive Industry light duty factory there is a problem to assemble and maintain

the lower part of the vehicle. The method used is ditch and the use of this method does not allow

free movement during assembly and maintenance and this leads to reduction in production rate

and quality.

1.1.1 Proposed SolutionTo create an easy and comfortable means for the maintenance of light duty vehicles Light duty

vehicles in Bishoftu Automotive Industry, a mechanism is designed to lift the vehicle from the

ground. This report presents the study of a hydraulic lifting platform that utilizes the pressure

power developed from hydraulic oil to raise or lower the vehicle.

A single piston hydraulic lift platform is designed so that it would be convenient for thepersonnel working on the vehicle to freely move around during working.

1.2 Aims and Objectives

The aim of this design is hydraulic platform lifting device that can be used for the assembly and

maintenance of light duty vehicles.The design conditions are to meet the following specifications;

The device is limited to an average load of 1900kg


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The device will have a maximum lift of 200 cm This objective is desirable to be achieved through the fluid power to raise or lower the

platform. The system must be operated on a flat surface.

1.3 Scope of the DesignThe design project starts by stating the problem statement and proceeds by collecting

background information on the problem type and the possible solution to it. The design of

hydraulic platform lift for light duty vehicles involves:-

The design of the platform for strength and bending as well as determination of thedimensions.

The design of the hydraulic circuit of the system. Calculations of the center of gravity for the model double cabin pick-up car. Selection of oil for the hydraulic pump, pump, reservoir, electric motor, hose, screw and

other accessories of the hydraulic circuit.


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Chapter Two

2.0 Literature Review

There are several distinct types of aerial work platforms, which all have specific features which

make them more or less distinct for different applications. The key difference is in the drive

mechanism which propels the working platform to the desired location. Most are powered by

either hydraulics or possibly pneumatics. The different techniques also reflect in the pricing and

availability of each type. An aerial work platform (AWP), also known as an aerial device or

elevating work platform (EWP), is a mechanical device used to provide temporary access for

people or equipment to inaccessible areas, usually at height. [1]

In recent years, various platforms or devices with various means of application have been

produced for use in the automotive industry. The automotive industry have also experience the

influx of various lifting platform, some of which are;

Electrically operated lifting device which is operated by the turning effect of electricmotor to drive the gear which will eventually turn a screw shaft to raise or lower load.

Hydraulic operated lifting platform which utilize the pressure power developed fromhydraulic oil to raise or lower a load.

Pneumatic lifting device which make use of air to create pressure or vacuum to raise orlower load.

The use of a scissors mechanism with a table platform that will be horizontal at everylevel.

Recent research also shows the use of air bag for raising or lowering load. [2]2.1 Various Lifting Platforms

2.1.1 Electric lifting Platform

These lift devices make use of electromagnetic power to raise or lower through the use of electric

motor. The device could be very expensive and there is high probability of jerking during startup

of the device through the torque created by the electric motor. [3]

The challenges of this system are;

Due to frequent raising and lowering of the lift, there is possibility of snapping in theelectric cable which could lead to exposure of the cable and could lead to electrocution.

It requires other accessories to be operated It requires trained personnel to operate it successfully. It requires regular maintenance Overheating in electrical coil could damage the system


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2.1.2 Pneumatic System

This device also operates like the hydraulic device, but it acquires its driving force/pressure from

the air [3]. The limitations with this system are;-

There is high risk of air leakage. Pneumatic systems are frequent with valve leakage. Precise control of movement is not possible due to high compressibility of air.

2.1.3 Scissor Lift

A scissor lift is a device used for lifting purposes, its objectives is to make the table adjustable to

desirable height. This mechanism comes with different actuation mechanisms like power screwand hydraulics. Its limitation is that it requires very large initial force to raise the mass from

minimum height and these results in high probability of system failure. [3]

2.1.4 Hydraulic-operated Lifting PlatformThe hydraulic lift makes use of fluid pressure to produce smooth movement during lifting. It has

some benefits when compared to other lifting device; firstly, its dependency on power supply is

eliminated. Secondly, it allows smooth movement without jerking due to steady increase in fluidpressure, majority of lift platform in market make use of hydraulic. Above all it has a high

capacity in terms of load lifting. [3]

2.2 Components of the Hydraulic Platform Lift

The hydraulic platform lift setup consists of the following parts:-

2.2.1 The electric motor

It is the prime mover of the system. It gets converts electrical energy to rotational mechanicalenergy. This is then made to drive the hydraulic pump via the belt that connects the shafts of the

motor and the pump. [4]

2.2.2 Hydraulic pump

Hydraulic pump is the unit that drives oil from the tank in to the cylinder. It is driven by the

electric motor. The pump, for this study, the external gear pump, which works by gears meshing

and rotating opposite to each other. As the gears rotate they trap oil between the teeth and the

pump housing and transfer it. [4]

2.2.3 Control valve

The control valve controls the flow of oil to the system and is used to stop when the desired

height is reached. [4]

2.2.4 Reservoir

The reservoir is also called tank is a unit where oil is stored. Oil pumped to rise the system is

made to flow back to the tank where it cools. [4]


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2.2.5 Hydraulic hoses

The hydraulic hoses used to transport oil to the cylinder and back to the tank. They are provided

with fittings for installation on the cylinder and pump. [5]

2.2.6 Hydraulic cylinder

Hydraulic cylinder (also called a linearhydraulic motor)is a mechanicalactuator that is used to

give a unidirectionalforce through a unidirectional stroke. A hydraulic cylinder is the actuator or

"motor" side of this system. The "generator" side of the hydraulic system is thehydraulic

pump which brings in a fixed or regulated flow of oil to the hydraulic cylinder, to move the

piston. The piston pushes the oil in the other chamber back to the reservoir.

Hydraulic cylinders get their power from pressurizedhydraulic fluid,which is typicallyoil.The

hydraulic cylinder consists of a cylinderbarrel,in which apiston connected to apiston

rod moves back and forth. The barrel is closed on one end by the cylinder bottom (also called thecap) and the other end by the cylinder head (also called the gland), where the piston rod comes

out of the cylinder. The piston has sliding rings and seals. The piston divides the inside of the

cylinder into two chambers, the bottom chamber (cap end) and the piston rod side chamber (rod

end / head end). [5]

The hydraulic cylinder consists of Cylinder barrel, Cylinder base or cap, Cylinder head, Piston,

Piston rod, seal glands, and seals.

The seal gland contains a primary seal, a secondary seal / buffer seal, bearing elements, wiper /

scraper and static seal. In some cases, especially in small hydraulic cylinders, the rod gland and

the bearing elements are made from a single integral machined part.

2.2.7 The Support Structure of the Top Platform

The top support platform is a horizontal rectangular bar mounted at top of the piston rod. It is the structure

that holds the vehicles chassis when lifting and during maintenance. It has two pairs of forks or arma that

open outward to support the vehicle at the chassis.
http://en.wikipedia.org/wiki/Hydraulic_motorhttp://en.wikipedia.org/wiki/Actuatorhttp://en.wikipedia.org/wiki/Forcehttp://en.wikipedia.org/wiki/Hydraulic_pumphttp://en.wikipedia.org/wiki/Hydraulic_pumphttp://en.wikipedia.org/wiki/Hydraulichttp://en.wikipedia.org/wiki/Hydraulic_fluidhttp://en.wikipedia.org/wiki/Oilhttp://en.wikipedia.org/wiki/Barrelhttp://en.wikipedia.org/wiki/Pistonhttp://en.wikipedia.org/wiki/Piston_rodhttp://en.wikipedia.org/wiki/Piston_rodhttp://en.wikipedia.org/wiki/Piston_rodhttp://en.wikipedia.org/wiki/Piston_rodhttp://en.wikipedia.org/wiki/Pistonhttp://en.wikipedia.org/wiki/Barrelhttp://en.wikipedia.org/wiki/Oilhttp://en.wikipedia.org/wiki/Hydraulic_fluidhttp://en.wikipedia.org/wiki/Hydraulichttp://en.wikipedia.org/wiki/Hydraulic_pumphttp://en.wikipedia.org/wiki/Hydraulic_pumphttp://en.wikipedia.org/wiki/Forcehttp://en.wikipedia.org/wiki/Actuatorhttp://en.wikipedia.org/wiki/Hydraulic_motor


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Figure: - 1 the platform lift setup


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Chapter Three

4.0 Design and Force Analysis of Components

4.1 Specifications for the System

The hydraulic platform lift presented in this report is to be used in Bishoftu Automobile Industry

for maintenance of light duty vehicles and it has the following specifications.

Overall vehicle weight of the model DD6479C to be lifted is 1740kg. [6]The maximumload on the piston of the hydraulic cylinder is taken as the sum of vehicle and platform

self-weight plus allowance for safety factor.

Stroke of the piston is taken as the maximum life and is 2000mm or 2m. The maximumsystem pressure should be greater than the pressure due to the load and is taken to be63.4bar

Due to cost and ease of maintenance and pressure specification, external gear pump isselected for the hydraulic system.

The maximum system pressure is required to be greater than the pressure due to the loadand is taken to be 63.4bar.

4.2 Determining Location for the Center of Gravity of the Vehicle

Typical load distribution for double cabin pick up is shown as follows. [7]

Figure: - 2 Typical load distribution for double cabin pickup


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Calculation for the axle load

Mass(M) Xcoordinate(mm) Mx(kg-mm)

Front bumper 20 0 0Power train 300 760 228,000

Front pass/seat 150 2385 357,00

Rear pass/seat 212.40 3715 789,067

Fuel tank 50 3610 180,500

Luggage/spare wheel 90 4880 439200

Rear bumper 30 5390 161700

Exhaust 30 3050 92400

Front structure 0.15x1625=243.75 812.5 198,046.9

Pass compartment

structure

0.18x2700=486 4325+1625/2 =2975 1445,850

Rear structure 0.12x1065=127.8 4325+5390/2=4857.5 620,7885

Total 1740kg 4251252.4

Table 1

Calculation for the axle load

Longitudinal position for center of gravity

Moment about front axle

Moment about rear axle


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Check for equilibrium

4.2 Force Analysis for the Platform

Design for plat form arms

The plat form pickup lifting position should be at the centroid where Total length of the pickup is the position of arm that support frontal part should set atthe position where power train lay.

Figure: -3 the total length of the pick-up

The position of front arm from centroid is calculated as


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Figure: -4 structure of the platform

Calculation for the link length CD (front arm)

Using Pythagoras theorem calculating for CD and,

The angle will be


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Calculation for the arm length AB (rear arm)

Using Pythagoras theorem calculating for AB and,

And the angle will be

Shear and bending moment diagram for arm AB (rear arm)

,


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Figure: -5 bending moment for the platform arm

,

Figure: -6 bending moment diagram for the platform arm


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Shear and bending diagram for arm CD (front arm)

,

Fig shear and bending diagram for arm CD (front arm)

Design of link AB with the cross section

Rectangular steel with hollow section with yield stress yield=855Mpa is selected. [8]


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Figure: -7 cross section of the arm

Data taken:-

Design stress for arm AB

Safety factor n


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,So the design is safe The total mass of the rear arms Design stress for arm CD

Safety factor n

,So the design is safe The total mass of the rear arms The overall weight of the structure

That means weight of the four arms and the weight of the plate.

Figure: -8 top plate


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Plate design, fixed at mid-point by bolt

From mechanical properties some typical material, we select that material steel form with yield

strength of which is steel with grade. [8] And h is thickness of the plate

Safety factor (n)


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Where,

Selection of screw

Specification on selection of the screw

Standard dimension of screw threads [9]

Table 11; 1 design dimension of screw threads, bolts and nuts according to IS: 4218(part iii)

1997

Designation

Pitch(mm) Major

diameter

Nut and

bolt

Effective or

pitch dia

nut and bolt

dp(mm)

Minor or core

diameter

dc

Depth of

thread

bolt(mm)

Stress

area()M36 4 36 33.42 bolt Nut 2.454 817

31.093 31.670

Checking for crushing stress on the threads and shear stress


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S Since yield crushing stress is greater than design crushing stress the design is safe.

Checking for shear stress

And A is stress area

Since yield shear stress is greater than design stress the design is safe


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Design of bolt

Figure: -9 dimensions for bolt

From mechanical property of steel bolts we select the bolt material to be medium carbon (Q and

T) with property class and the min tensile strength of Where p is

From Table 11.1 (coarse series), machine design by Khurmi and Gupta we find that the standard

core diameter is and corresponding size of the bolt is And also for bolt diameter of 28 we have hexagonal nut diameter of

for this

diameter of nut we have width and height and washer internaldiameter of 30mm and outside diameter of 56mm which have maximum thickness of 5mm fromappendix Shigleys mechanical design book[12] Where is length of threaded part.


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= 92mm

Design of pin

Assuming the pine material is steel with tensile stress having Reaction moment at the pin is calculated .

Maximum design stress of pin

Where d is the diameter of the pin.

Diameter of knuckle pin and collar Thickness of pin head


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Outer diameter of head

It is not such much necessary to design pin for other two arms because if it is designed for

maximum bending moment it will be safe for other, which have less bending moment.

Design of the cover plate for the cylinder rod

We select the cover plate material will be mild steel with Section modulus

Where wwidth of the plate and

Where outside diameter of the plate and Hole diameter of the bolt

Circumferential pitch of bolts

Size of the bolt Let size of the bolt hole would be

Minimum circumferential pitch of bolts

, 20 Maximum circumferential pitch of bolts

We know that for a leak joint the circumfrential pitch of bolts should lie between to , so that lets take the circumferential pitch will be Circumferential pitch of the bolt


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Where n is number of bolts

Outside diameter of cover plate

Width of the plate

=

Suction modulus

We know that moment acting on the cover plate

From bending equation of


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4.3 Design of the Hydraulic Circuit

Specification of the jobForce requirement of the job is Length of the stroke

This relates to the maximum lifting height and is taken to be

. Speed of piston and rod assembly

Minimum time is taken to be . The speed is therefore. Cylinder Size

Rod diameter is taken to be Cylinder selected with bore diameter of

Area of rod is And the pressure on the rod side is; - from we can get the pressure as This is the total pressure due to the weight of the vehicle. So the pressure applied by the pump

should exceed the above pressure and for this a pump pressure of is selected.

The capacity of pump needed

Maximum cylinder speed is; -

Flow rate: -


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But area of piston So flow rate becomes

The size of electric motor needed.

Power required to run the pump is calculated as; -

Efficiency of pumpThe type of pump selected is gear pump with efficiency of Shaft size, tape and electric source

Reservoir size neededReservoir size should be times the pump capacity Pump capacity is and this becomes

So the reservoir size is taken to be Pressure vessel and stress concentration in the hydraulic cylinder


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Figure:- 10 hydraulic cylinder cross-section

The force exerted by the fluid must be equal to the force exerted by the pipe walls; that is the

sum must be zero.

The force exerted by the fluid is , where is inside diameterThe stress acts around the circumference; that is the stress is hoop stress. [10]

The stress in the walls of the pipe is equal to the fluid force divided by the cross sectional area of

the pipe wall.

So the hydraulic cylinder has a pressurized fluid which would push the rod end and the stress

will develop along the length of the pipe to resist the pressure on the rod end. The shape of the

cup does not affect the longitudinal stress in the pipe.

Figure:- 11 pressure lines inside the cylinder

The force exerted by the fluid equals the force along the length of the pipe walls. Pressure acts

on a circular area of fluid, so the force exerted by the fluid is:-


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=The stress along the length of the pipe is

Figure:- 12 hydraulic circuit

4.4 Selection of Hydraulic Pump

External gear pump is selected for this system. External gear pumps are less efficient than

internal gear pumps, but have some advantages. They offer ease of maintenance, steady flow,

and are less expensive to buy and repair. These pumps can produce pressures ranging from to i, and their viscosity range is limited to (centistokes).


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4.5 Selection of Hydraulic Oil

With hydraulics there are two primaryconsiderationsthe viscosity grade and the hydraulic oil type.

The specifications are typically determined by the type of hydraulic pump employed in the system,

operating temperature, and the operating pressure.

The type of hydraulic oil suitable for this application and the external gear pump is found to be full

synthetic oil with viscosity of 4.6 Selection of Hoses and Fittings

There are places on many machines where rigid pipe or tubing cannot be used because of their

inflexibility. Rigid lines can cause problems at cylinders with pivot mountings, pumps on noise-

isolation mounts, or connections between separate units. Hose avoids these problems. Wire

braised hydraulic hose selection for hydraulic platform lifter is based on the following

specifications: -

For rated internal pressure of , a hydraulic hose with the followingspecifications is selected.

Part number Hose internal diameter 1in Hose outer diameter Minimum burst 4000Psi

Minimum bend radius Weight per foot 4.7 Selection of Electric Motor

The electric motor horsepower needed to drive a positive displacement pump is calculated from

the formula assuming a pump efficiency of whichwould be representative of most positive displacement pumps.

The motor most often used to drive a hydraulic pump is a 3-phase, induction type, design B

motor. The service factors on most open frame sizes is which means that the motor can beoverloaded about

above current shown on its nameplate, assuming it is being operated in a

normal temperature environment.[11]

The motor selected is therefore, as per the calculation, a 3-phase,, inductionmotor


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4.8 Installation and Operation of the Platform

The hydraulic cylinder with the support platform at the top of the piston rod is mounted below

ground with its fully retracted position and the support arms on the ground. The pump control

valves, reservoir, and electric motor are mounted on the ground and are connected to the cylinder

via hydraulic hoses.

This is because when the piston is initially at its fully retracted position, it is in such a way that

the top platform is just on the ground at its lowest level. The vehicle comes along and the chassis

is made to align with the platform arms at the position of the center of gravity. Oil is then

allowed to be pumped to the cylinder which raises the piston thereby lifting the vehicle.

The height can be adjusted anywhere in the range of the maximum limit as per the requirement

of the personnel working on it by controlling the oil flow via control valves.


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Chapter Five

5.0 Conclusion and Recommendation

5.1 Conclusion

In this project, the design of a hydraulic lifting platform is done for an average vehicle load of

1740kg and lifting height of 1.8m. The analysis includes the design of the hydraulic circuit, the

design of the support platform arms, the design of screws, bolts and other fasteners. Selection of

various components of the hydraulic system is also made based on the system maximum

pressure.

From the results obtained in the analysis, the following can be concluded:

Position for the center of gravity for the model double cabin pick up is at2443.25mm left to right from front to back. The prime mover for the system (electric motor) is found to be a 3-phase, 220-240V, 60

Hz induction motor.

The top T-platform that supports the vehicle is subject to bending due to vehicle weight. Pressure on the rod side (pressure due to the load) is found to be 6.69bar


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5.2 Recommendation

The design in this report is based on some specifications and assumptions. However the system

can be redesigned for any required applications and specifications

Based on the design specifications of the job, the following are recommended for use:

It is recommended that the vehicle is checked for proper alignment on the platform at itscenter of gravity before lifting.

It is also recommended to fix the vehicle chassis on the arms with the provided clampsand screws for balance during work.

It is recommended to check the hoses and change them continually.


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References

[1]Wikipedia, the free encyclopedia

[2]Design and manufacturing of lifting machines, by Q.S. Khan

[3]National fluid power association, Standardization of Fluid Power Components

[4]Applied Hydraulics and Pneumatics, by K.H. Rial

[5]Brand Hydraulics,www.brand-hyd.com

[6]Bishoftu Automotive Industry, Light Duty Vehicle Factory

[7]Automotive Engineering Fundamentals, by Richard Stone and Jeffery K. Ball

[8]Properties of Engineering Materials, Digital Engineering Library

[9]Design dimension of screw threads, bolts and nuts according to IS41 (part iii 1997 table 11.1)

[10]Text book of Machine Design, by R.S. Khurmi and J.K. Gupta

[11]Womack Machine Supply Co. Fluid Power Design Data Sheet 3-Electric motor Size for

Hydraulic Pump Drive.

[12] Shigleys mechanical engineering design text book
http://www.brand-hyd.com/http://www.brand-hyd.com/http://www.brand-hyd.com/http://www.brand-hyd.com/

design of hydraulic platform lift

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