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design and fabrication of motorized screw jack
for a four wheeler
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CHAPTER 1
LITERATURE SURVEY
Screw type mechanical jacks were very common for jeeps and trucks of World War II vintage.
For example, the World War II jeeps (Willys MB and Ford GPW) were issued the "Jack,
Automobile, Screw type, Capacity 1 1/2 ton", Ordnance part number 41-J-66. This jacks, and
similar jacks for trucks, were activated by using the lug wrench as a handle for the jack's ratchet
action to of the jack. The 41-J-66 jack was carried in the jeep's tool compartment. Screw type
jack's continued in use for small capacity requirements due to low cost of production raise or
lower it. A control tab is marked up/down and its position determines the direction of movement
and almost no maintenance.
The virtues of using a screw as a machine, essentially an inclined plane wound round a cylinder,
was first demonstrated by Archimedes in 200BC with his device used for pumping water.
CHAPTER 2
POWER SCREWS
A power screw is a mechanical device used for converting rotary motion into linear motion and
transmitting power. A power screw is also called translation screw. It uses helical translatory
motion of the screw thread in transmitting power rather than clamping the machine components.
2.1 Applications
The main applications of power screws are as follows:
(i) To raise the load, e.g. screw-jack,
(ii) To obtain accurate motion in machining operations, e.g. lead-screw of lathe,
(iii) To clamp a workpiece, e.g. vice, and
(iv) To load a specimen, e.g. universal testing machine.
There are three essential parts of a power screw, viz.screw, nut and a part to hold either the screw
or the nut in its place. Depending upon the holding arrangement, power screws operate in two
different ways. In some cases, the screw rotates in its bearing, while the nut has axial motion.
The lead screw of the lathe is an example of this category. In other applications, the nut is kept
stationary and the screw moves in axial direction. Screw-jack and machine vice are the examples
of this category.
2.2 Advantages
Power screws offer the following advantages:
(i) Power screw has large load carrying capacity.
(ii) The overall dimensions of the power screw are small, resulting in compact construction.
(iii) Power screw is simple to design
(iv) The manufacturing of power screw is easy without requiring specialized machinery. Square
threads are turned on lathe. Trapezoidal threads are manufactured on thread milling machine.
(v) Power screw provides large mechanical advantage. A load of 15 kN can be raised by
applying an effort as small as 400 N.Therefore, most of the power screws used in various
applications like screw-jacks, clamps, valves and vices are usually manually operated.
(vi) Power screws provide precisely controlled and highly accurate linear motion required in
machine tool applications.
(vii) Power screws give smooth and noiseless service without any maintenance.
(viii) There are only a few parts in power screw. This reduces cost and increases reliability
2.3 Disadvantages
The disadvantages of power screws are as follows:
(i) Power screws have very poor efficiency; as low as 40%.Therefore, it is not used in continuous
power transmission in machine tools, with the exception of the lead screw. Power screws are
mainly used for intermittent motion that is occasionally required for lifting the load or actuating
the mechanism.
(ii) High friction in threads causes rapid wear of the screw or the nut. In case of square threads,
the nut is usually made of soft material and replaced when worn out. In trapezoidal threads, a
split- type of nut is used to compensate for the wear. Therefore, wear is a serious problem in
power screws.
2.4.3 Advantages of Trapezoidal Threads
The advantages of trapezoidal threads over square threads are as follows:
(i) Trapezoidal threads are manufactured on thread milling machine. It employs multi-point
cutting tool. Machining with multi-point cutting tool is an economic operation compared to
machining with single point-cutting tool. Therefore, trapezoidal threads are economical to
manufacture.
(ii) Trapezoidal thread has more thickness at core diameter than that of square thread.Therfore; a
screw with trapezoidal threads is stronger than equivalent screw with square threads. Such a
screw has large load carrying capacity.
(iii) The axial wear on the surface of the trapezoidal threads can be compensated by means of a
split-type of nut. The nut is cut into two parts along the diameter. As wear progresses, the
looseness is prevented by tightening the two halves of the nut together, the split-type nut can be
used only for trapezoidal threads. It is used in lead-screw of lathe to compensate wear at periodic
intervals by tightening the two halves.
2.5 Designation of Threads
There is a particular method of designation for square and trapezoidal threads. A power screw
with single-start square threads is designated by the letters „Sq‟ followed by the nominal
diameter and the pitch expressed in millimeters and separated by the sign „x‟. For example,
Sq 30 x 6
It indicates single-start square threads with 30mm nominal diameter and 6mm pitch.
2.7 Torque Requirement- Lifting Load
The screw is considered as an inclined plane with inclination α.When the load is being raised,
following forces act at a point on this inclined plane:
(i) Load W: It always acts in vertically downward direction.
(ii) Normal reaction N: It acts perpendicular (normal) to the inclined plane.
(iii) Frictional force μN: Frictional force acts opposite to the motion. Since the load is moving
up the inclined plane, frictional force acts along the inclined plane in downward direction.
2.10 Efficiency of Square Threaded Screw
Refer to the force diagram for lifting the load, illustrated in Fig. .Suppose the load W moves
from the lower end to the upper end of the inclined plane. The output consists of raising the load.
Therefore,
Work output = force x distance travelled in the direction of force
= W x l
The input consists of rotating the screw by means of an effort P.
Work output = force x distance travelled in the direction of force
= P x (π dm)
The efficiency η of the screw is given by,
η =
=
=
tan α
Substituting P = W tan (θ + α) in the above equation,
η =
From the above equation, it is evident that the efficiency of the square threaded screw depends
upon the helix angle α and the friction angle θ.The following figure shows the variation of the
efficiency of square threaded screw against the helix angle for various values of coefficient of
friction. The graph is applicable when the load is lifted.
2.12 Efficiency of Trapezoidal and Acme Threads
The thread angle is 2θ.For isometric I.S.O metric trapezoidal thread,
2θ = 30°
For acme thread,
2θ = 29°
There is a basic difference between the force acting on the thread of square and trapezoidal
threads. In case of square threads, W is the axial load raised by the screw. It is also the normal
force acting on the thread surface. In case of trapezoidal or acme threads, these two forces are
different. The axial force on the screw is W, while the normal force on the thread surface is
(W/cos θ) or (Wsec θ).The frictional force depends upon the normal force.Therefore; the effect of
thread angle is to increase the frictional force by a term (sec θ).This is because of the wedging
action of the threads. The coefficient of friction is taken as (μ sec θ) instead of μ in case of
trapezoidal threads and the equations derived for square threaded screw are modified and used
for trapezoidal or acme threads.
2.13 Coefficient of Friction
It has been found that the coefficient of friction (μ) at the thread surface depends upon the
workmanship in cutting the threads and on the type of the lubricant. It is practically independent
of the load, rubbing velocity or materials. An average of 0.15 can be taken for the coefficient of
friction, when the screw is lubricated with mineral oil.
2.14 Stresses in Screw and Nut
The body of a screw is subjected to an axial force W and torsional moment (T).The direct
compressive stress Fc is given by,
Fc =
The torsional shear stress is given by,
Ft =
The principal shear stress is given by,
CHAPTER 3
SCREW JACK
A screw jack is a portable device consisting of a screw mechanism used to raise or lower the
load. The principle on which the screw jack works is similar to that of an inclined plane. There
are mainly two types of jacks-hydraulic and mechanical. A hydraulic jack consists of a cylinder
and piston mechanism. The movement of the piston rod is used to raise or lower the load.
Mechanical jacks can be either hand operated or power driven.
Jacks are used frequently in raising cars so that a tire can be changed. A screw jack is commonly
used with cars but is also used in many other ways, including industrial machinery and even
airplanes. They can be short, tall, fat, or thin depending on the amount of pressure they will be
under and the space that they need to fit into. The jack is made out of various types of metal, but
the screw itself is generally made out of lead.
While screw jacks are designed purposely for raising and lowering loads, they are not ideal for
side loads, although some can withstand side loads depending on the diameter and size of the
lifting screw. Shock loads should also be avoided or minimized. Some screw jacks are built with
anti-backlash. The anti-backlash device moderates the axial backlash in the lifting screw and nut
assembly to a regulated minimum.
A large amount of heat is generated in the screw jack and long lifts can cause serious
overheating. To retain the efficiency of the screw jack, it must be used under ambient
temperatures, otherwise lubricants must be applied. There are oil lubricants intended to enhance
the equipment‟s capabilities. Apart from proper maintenance, to optimize the capability and
usefulness of a screw jack it is imperative to employ it according to its design and
manufacturer‟s instruction. Ensure that you follow the speed, load capacity, temperature
recommendation and other relevant factors for application
3.1 The Screw
The screw has a thread designed to withstand an enormous amount of pressure. This is due to the
fact that it is generally holding up heavy objects for an extended amount of time. Once up, they
normally self lock so that they won't fall if the operator lets go, and they hold up well to the wear
of repeated use. If they are made with a ball nut, they will last longer because there is less
friction created with this type of jack. However, they will not self lock. This can be dangerous
and handled carefully.
3.2 Operation
The jack can be raised and lowered with a metal bar that is inserted into the jack. The operator
turns the bar with his hands in a clockwise direction. This turns the screw inside the jack and
makes it go up. The screw lifts the small metal cylinder and platform that are above it. As the
jack goes up, whatever is placed above it will raise as well, once the jack makes contact. The bar
is turned until the jack is raised to the level needed. To lower the jack the bar is turned in the opposite direction. An automatic screw jack has gears inside the jack that are connected to the
screw. Theses gears are connected by other gears and bars that are turned by a power source to
raise and lower the jack
3.3 Construction of Screw Jack
Screw jack consists of a screw and a nut. The nut is fixed in a cast iron frame and remains
stationary. The rotation of the nut inside the frame is prevented by pressing a set screw against it.
The screw is rotated in the nut by means of a handle, which passes through a hole in the head of
the screw. The head carries a platform, which supports the load and remains stationary while the
screw is being rotated. A washer is fixed to the other end of the screw inside the frame, which
prevents the screw to be completely turned out of the nut.
3.4 Function
The basic function of a screw jack is to lift a portion of a vehicle. Typically this is used to change
a tire although other maintenance is sometimes performed.
3.5 Features
All jacks have safety features to protect the user from accidental injury. Wide bases help to
stabilize a jack and prevent tilting or sinking into soft soil. Most car jacks also come equipped
with their own handle or cranking mechanism, but alternately many of these also will accept the
flat end of a tire tool to jack up a vehicle. When in the extended position, jacks will have a stop
point that prevents the user from overextending the jack beyond its rated capabilities. When in
the contracted position, jacks that are provided by the manufacturer will have a storage area
specially formed or designed for the jack to rest in when not in use.
3.6 Benefits
Equipping motorists with car jacks has provided many benefits to those who are on the road.
Most importantly, jacks have equipped drivers with the ability to change a tire in an emergency
situation without having to call for assistance, which can save service fees and potential towing
fees as well. Car jacks also provide the home auto enthusiast with a tool to use in maintenance of
their own vehicle with the simpler tasks such as changing brake pads, oil and belts. When used
appropriately with safety in mind, car jacks are an essential resource for anyone owning or
operating a motorized vehicle.
3.7 Types
Jacks are of mainly two types- mechanical and hydraulic. They vary in size depending on the
load that they are used to lift.
3.7.1 Mechanical Jacks
A mechanical jack is a device which lifts heavy equipment. The most common form is a car jack,
floor jack or garage jack which lifts vehicles so that maintenance can be performed. Car jacks
usually use mechanical advantage to allow a human to lift a vehicle by manual force alone. More
powerful jacks use hydraulic power to provide more lift over greater distances. Mechanical jacks
are usually rated for maximum lifting capacity. There are two types of mechanical jacks:
3.7.1.1 Scissor Jacks
Scissors jacks are also mechanical and have been in use at least since the 1930s.
A scissor jack is a device constructed with a cross-hatch mechanism, much like a scissor,
to lift up a vehicle for repair or storage. It typically works in just a vertical manner. The
jack opens and folds closed, applying pressure to the bottom supports along the crossed
pattern to move the lift. When closed, they have a diamond shape.
Scissor jacks are simple mechanisms used to drive large loads short distances. The
power screw design of a common scissor jack reduces the amount of force required by
the user to drive the mechanism. Most scissor jacks are similar in design, consisting of
four main members driven by a power screw.
A scissor jack is operated simply by turning a small crank that is inserted into one end of
the scissor jack. This crank is usually "Z" shaped. The end fits into a ring hole mounted
on the end of the screw, which is the object of force on the scissor jack. When this crank
is turned, the screw turns, and this raises the jack. The screw acts like a gear mechanism.
It has teeth (the screw thread), which turn and move the two arms, producing work. Just
by turning this screw thread, the scissor jack can lift a vehicle that is several thousand
pounds.
Construction
A scissor jack has four main pieces of metal and two base ends. The four metal pieces are all
connected at the corners with a bolt that allows the corners to swivel. A screw thread runs across
this assembly and through the corners. As the screw thread is turned, the jack arms travel across
it and collapse or come together, forming a straight line when closed. Then, moving back the
other way, they raise and come together. When opened, the four metal arms contract together,
coming together at the middle, raising the jack. When closed, the arms spread back apart and the
jack closes or flattens out again.
Design and Lift
A scissor jack uses a simple theory of gears to get its power. As the screw section is turned, two
ends of the jack move closer together. Because the gears of the screw are pushing up the arms,
the amount of force being applied is multiplied. It takes a very small amount of force to turn the
crank handle, yet that action causes the brace arms to slide across and together. As this happens
the arms extend upward. The car's gravitational weight is not enough to prevent the jack from
opening or to stop the screw from turning, since it is not applying force directly to it. If you were
to put pressure directly on the crank, or lean your weight against the crank, the person would not
be able to turn it, even though your weight is a small percentage of the cars
3.7.2 Hydraulic Jacks
Hydraulic jacks are typically used for shop work, rather than as an emergency jack to be carried
with the vehicle. Use of jacks not designed for a specific vehicle requires more than the usual
care in selecting ground conditions, the jacking point on the vehicle, and to ensure stability when
the jack is extended. Hydraulic jacks are often used to lift elevators in low and medium rise
buildings.
A hydraulic jack uses a fluid, which is incompressible, that is forced into a cylinder by a pump
plunger. Oil is used since it is self lubricating and stable. When the plunger pulls back, it draws
oil out of the reservoir through a suction check valve into the pump chamber. When the plunger
moves forward, it pushes the oil through a discharge check valve into the cylinder. The suction
valve ball is within the chamber and opens with each draw of the plunger. The discharge valve
ball is outside the chamber and opens when the oil is pushed into the cylinder. At this point the
suction ball within the chamber is forced shut and oil pressure builds in the cylinder.
3.8 Design of Screw Jack
3.8.1 Loads and Stresses in Screw
The load on the screw is the load which is to be lifted W, twisting moment M, between the screw
threads and force F at the handle to rotate the screw.
The load W is compressive in nature and induces the compressive stress in the screw. It may also
lead the screw to buckle.
The load F produces bending and it is maximum, when the screw is at its maximum lift. The
screw also experiences twisting moment due to F. the shear stress is also induced in the screw
due to the twisting moment between the threads of screw and nut.
CHAPTER 4
MOTORIZED SCREW JACK
Our survey in the regard in several automobile garages, revealed the facts that mostly some
difficult methods were adopted in lifting the vehicles for reconditioning.
Now the project has mainly concentrated on this difficulty, and hence a suitable device has been
designed, such that the vehicle can be lifted from the floor land without application of any
impact force.
The fabrication part of it has been considered with almost case for its simplicity and economy,
such that this can be accommodated as one of the essential tools on automobile garages.
4.1 Introduction
The motorized screw jack has been developed to cater to the needs of small and medium
automobile garages, which are normally man powered with minimum skilled labor. In most of
the garages the vehicles are lifted by using screw jack. This needs high man power and skilled
labour.
In order to avoid all such disadvantages, the motorized jack has been designed in such a way that
it can be used to lift the vehicle very smoothly without any impact force. The operation is made
simple so that even unskilled labour can use it with ease.
The d.c motor is coupled with the screw jack by gear arrangement. The screw jack shaft‟s
rotation depends upon the rotation of D.C motor. This is a simple type of automation project.
This is an era of automation where it is broadly defined as replacement of manual effort by
mechanical power in all degrees of automation. The operation remains to be an essential part of
the system although with changing demands on physical input, the degree of mechanization is
increased.
Degrees of automation are of two types, viz.
4.2 Need for Automation
Automation can be achieved through computers, hydraulics, pneumatics, robotics, etc.
Automation plays an important role in mass production.
For mass production of the product, the machining operations decide the sequence of
machining. The machines designed for producing a particular product are called transfer
machines. The components must be moved automatically from the bins to various machines
sequentially and the final component can be placed separately for packaging. Materials can also
be repeatedly transferred from the moving conveyors to the work place and vice versa.
Nowadays, almost all the manufacturing processes are being atomized in order to deliver the
products at a faster rate. The manufacturing operation is being atomized for the following
reasons:
To achieve mass production
To reduce man power
To increase the efficiency of the plant
To reduce the work load
To reduce the production cost
To reduce the production time
To reduce the material handling
To reduce the fatigue of workers
To achieve good product quality
Less Maintenance
4.3 Parts of Motorized Screw Jack
The main parts of the motorized screw jack are as follows:
4.3.1 D.c. motor (permanent magnet)
Description of dc motor
An electric motor is a machine which converts electrical energy to mechanical energy. Its action
is based on the principle that when a current-carrying conductor is placed in a magnetic field, it
experiences a magnetic force whose direction is given by Fleming‟s left hand rule.
When a motor is in operation, it develops torque. This torque can produce mechanical
rotation. DC motors are also like generators classified into shunt wound or series wound or
compound wound motors.
4.3.2 Batteries
4.3.2.1 Introduction
In isolated systems away from the grid, batteries are used for storage of excess solar
energy which can be converted into electrical energy. In fact for small units with output less
than one kilowatt, batteries seem to be the only technically and economically available storage
means. Since both the photo-voltaic system and batteries are high in capital costs, it is necessary
that the overall system be optimized with respect to available energy and local demand pattern.
To be economically attractive the storage of solar electricity requires a battery with a particular
combination of properties:
(1) Low cost
(2) Long life
(3) High reliability
(4) High overall efficiency
(5) Low discharge
(6) Minimum maintenance
(A) Ampere hour efficiency
(B) Watt hour efficiency
4.3.2.2 Lead-acid wet cell
Where high values of load current are necessary, the lead-acid cell is the type most
commonly used. The electrolyte is a dilute solution of sulfuric acid (H₂SO₄). In the application
of battery power to start the engine in an auto mobile, for example, the load current to the starter
motor is typically 200 to 400A. One cell has a nominal output of 2.1V, but lead-acid cells are
often used in a series combination of three for a 6-V battery and six for a 12-V battery.
The lead acid cell type is a secondary cell or storage cell, which can be recharged. The
charge and discharge cycle can be repeated many times to restore the output voltage, as long as
the cell is in good physical condition. However, heat with excessive charge and discharge
currents shortens the useful life to about 3 to 5 years for an automobile battery. Of the different
types of secondary cells, the lead-acid type has the highest output voltage, which allows fewer
cells for a specified battery voltage.
4.3.2.3 Construction
Inside a lead-acid battery, the positive and negative electrodes consist of a group of plates
welded to a connecting strap. The plates are immersed in the electrolyte, consisting of 8 parts of
water to 3 parts of concentrated sulfuric acid. Each plate is a grid or framework, made of a lead antimony alloy. This construction enables the active material, which is lead oxide, to be pasted
into the grid. In manufacture of the cell, a forming charge produces the positive and negative
electrodes. In the forming process, the active material in the positive plate is changed to lead
peroxide (pbo₂). The negative electrode is spongy lead (pb).
Automobile batteries are usually shipped dry from the manufacturer. The electrolyte is
put in at the time of installation, and then the battery is charged.With maintenance-free batteries,
little or no water is needed to be added in normal service. Some types are sealed, except for a
pressure vent, without provision for adding water.
4.3.2.4 Chemical action
Sulfuric acid is a combination of hydrogen and sulfate ions. When the cell discharges,
lead peroxide from the positive electrode combines with hydrogen ions to form water and with
sulfate ions to form lead sulfate. Combining lead on the negative plate with sulfate ions also
produces sulfate. Therefore, the net result of discharge is to produce more water, which dilutes
the electrolyte, and to form lead sulfate on the plates.
As the discharge continues, the sulfate fills the pores of the grids, retarding circulation of
acid in the active material. Lead sulfate is the powder often seen on the outside terminals of old
batteries. When the combination of weak electrolyte and sulfating on the plate lowers the output
of the battery, charging is necessary.
4.3.2.5 Caring For Lead-Acid Batteries
Always use extreme caution when handling batteries and electrolyte. Wear gloves,
goggles and old clothes. “Battery acid” will burn skin and eyes and destroy cotton and wool
clothing.
The quickest way of ruining lead-acid batteries is to discharge them deeply and leave
them stand “dead” for an extended period of time. When they discharge, there is a chemical
change in the positive plates of the battery. They change from lead oxide (when charged) to lead
sulfate when discharged. If they remain in the lead sulfate state for a few days, some part of the
plate does not return to lead oxide when the battery is recharged. If the battery remains in a
discharged state for a longer time, a greater amount of the positive plate will remain lead sulfate.
The parts of the plates that become “sulfate”, no longer store energy. Batteries that are deeply
discharged, and then charged partially on a regular basis can fail in less then one year.
Check your batteries on a regular basis to be sure they are getting charged. Use a
hydrometer to check the specific gravity of your lead acid batteries. If batteries are cycled very
deeply and then recharged quickly, the specific gravity reading will be lower than it should be
because the electrolyte at the top of the battery may not have mixed with the “charged”
electrolyte.
Check the electrolyte level in the wet-cell batteries at least four times a year and top each
cell with distilled water. Do not add water to discharged batteries. Electrolyte is absorbed when
batteries are discharged. If you add water at this time, and then recharge the battery, electrolyte
will overflow and make a mess.
Keep the top of your batteries clean and check that cables are tight. Do not tighten or
remove cables while charging or discharging. Any spark around batteries can cause a hydrogen
explosion inside, and ruin one of the cells.
On charge, with reverse current through the electrolyte, the chemical action is reversed.
Then the pb ions from the lead sulfate on the right side of the equation re-form the lead and lead
peroxide electrodes. Also the SO₄ ions combine with H₂ ions from the water to produce more
sulfuric acid at the left side of the equation.
4.3.2.6 Current Ratings
Lead-acid batteries are generally rated in terms of how much discharge currents they can
supply for a specified period of time; the output voltage must be maintained above a minimum
4.3.2.7 Specific Gravity
Measuring the specific gravity of the electrolyte generally checks the state of discharge
for a lead-acid cell. For instance, concentrated sulfuric acid is 1.835 times as heavy as water for
the same volume. Therefore, its specific gravity equals 1.835. The specific gravity of water is 1,
since it is the reference.
In a fully charged automotive cell, mixture of sulfuric acid and water results in a specific
gravity of 1.280 at room temperatures of 70 to 80ºF. As the cell discharges, more water is
formed, lowering the specific gravity. When it is down to about 1.150, the cell is completely
discharged.
Specific-gravity readings are taken with a battery hydrometer.Note that the calibrated
float with the specific gravity marks will rest higher in an electrolyte of higher specific gravity.
The importance of the specific gravity can be seen from the fact that the open-circuit
voltage of the lead-acid cell is approximately equal to
V = Specific gravity + 0.84
For the specific gravity of 1.280, the voltage is 1.280 = 0.84 = 2.12V, as an example.
These values are for a fully charged battery.
4.3.2.8 Charging the Lead-Acid Battery
An external D.C. voltage source is necessary to produce current in one direction. Also,
the charging voltage must be more than the battery e.m.f. Approximately 2.5 per cell are enough
to produce current opposite to the direction of discharge current.
Note that the reversal of current is obtained just by connecting the battery VB and
charging source VG with + to + and –to. The charging current is reversed because the battery
effectively becomes a load resistance for VG when it higher than VB. In this example, the net
voltage available to produce charging currents is 15-12=3V.
A commercial charger for automobile batteries is essentially a D.C. power supply,
rectifying input from the AC power line to provide D.C. output for charging batteries.
Float charging refers to a method in which the charger and the battery are always
connected to each other for supplying current to the load. In figure the charger provides current
for the load and the current necessary to keep the battery fully charged. The battery here is an
auxiliary source for D.C. power.
It may be of interest to note that an automobile battery is in a floating-charge circuit. The
battery charger is an AC generator or alternator with rectifier diodes, driven by a belt from the
engine.When you start the car, the battery supplies the cranking power. Once the engine is
running, the alternator charges the battery. It is not necessary for the car to be moving. A
voltage regulator is used in this system to maintain the output at approximately 13 to 15 V.It is a
good idea to equalize charge when some cells show a variation of 0.05 specific gravity from each
other. With proper care, lead-acid batteries will have a long service life and work very well in
almost any power system.
4.3.3 Screw Jack
The screw jack used in this project is a 5 tonne bottle (cylindrical) jack. It mainly consists of the
body, screw, nut and thrust bearings. In this type of a jack, the nut remains stationary while the
screw rotates and helps in lifting or lowering of the load.
4.4 Working Principle
The lead-acid battery is used to drive the d.c motor. The d.c motor shaft is connected
to the spur gear. If power is given to the D.c motor, it will run so that the spur gear also runs to
slow down the speed of the D.C motor. The screw jack moves the screw upward, so that the
vehicle lifts from ground.
The vehicle is lifted by using the lifting platform at the top of the screw jack. The motor
draws power supply from the battery. The lifting and uplifting is done by changing the battery
supply to the motor.
4.5 Advantages
1. The loaded light vehicles can be easily lifted.
2. Checking and cleaning are easy, because the main parts are screwed.
3. Handling is easy
4. No Manual power required.
5. Easy to Repair.
6. Replacement of parts are easy
4.6 Disadvantages
Cost of the equipment is high when compared to ordinary hand jack.
Care must be taken for the handling the equipment such as proper wiring
connection, battery charging checkup, etc.
4.7 Applications
1. It is useful in auto-garages.
2. This motorized screw jack is used for lifting the vehicles. Thus it can be useful for the
following types of vehicles in future;
Maruti, Ambassador, Fiat, Mahindra
CONCLUSION
Screw Jacks are the ideal product to push, pull, lift, lower and position loads of anything from a
couple of kilograms to hundreds of tonnes.The need has long existed for an improved portable
jack for automotive vehicles. It is highly desirable that a jack become available that can be
operated alternatively from inside the vehicle or from a location of safety off the road on which
the vehicle is located. Such a jack should desirably be light enough and be compact enough so
that it can be stored in an automobile trunk, can be lifted up and carried by most adults to its
position of use, and yet be capable of lifting a wheel of a 4,000-5,000 pound vehicle off the
ground. Further, it should be stable and easily controllable by a switch so that jacking can be
done from a position of safety. It should be easily movable either to a position underneath the
axle of the vehicle or some other reinforced support surface designed to be engaged by a jack.
Thus, the product has been developed considering all the above requirements. This particular
design of the motorized screw jack will prove to be beneficial in lifting and lowering of loads.