A Car Jack Is A Mechanical Device Engineering Essay
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A car jack is a mechanical device used to easily lift heavy loads cars, to gain an easy access to sections underneath vehicles or to simply just change a wheel. The most important fact of a jack is that it gives the user a mechanical advantage by changing rotational force into linear, allowing the user to lift heavy structures up that would be impossible to do without this tool.
There are different types of car jack structures, some consists in having a screw threaded component that allows the changes in height, others are more "automatic" as they use a hydraulic or pneumatic system that pump fluid and pressured air to make components rise and force the structure to operate; some structures require more mechanical force than others.
SCISSOR CAR JACK - a scissor car jack is a type of device that helps to raise a vehicle off the ground; it's called a scissor jack as the structure consists in having diagonal metal components that expand and contract in the same way of a pair of scissors. It works by lifting loads vertically and applies the pressure on the bottom supports of the structure. It has a very compact diamond shape when it's closed and the operation of the jack can also be motorised. The scissor jack is able to lift great forces as it turns rotary motion into linear; this is because of the screw threaded component. This component is situated where the two bottom supports are attached to the two top ones (see fig.1.), as this component as rotated either clockwise or anticlockwise, it forces the two meeting points of the supports to move on an horizontal plane, causing them to attract or expand; this operation forces the entire structure of the jack to higher or lower depending on which way the threated component is turned. This component is easily turned as the operator can attach a long handle to it, allowing an easier rotational movement. As the thread is very fine, it does take many rotational cycles to gain the right height of the vehicle but the thicker the thread is, the more input force would be needed for its operation.
http://www.ehow.co.uk - Car jack specifications-2012
Figure 1 - Scissor jack - www.walmart.com - 2012 http://i.walmartimages.com/i/p/00/61/52/68/10/0061526810152_500X500.jpg
Fig.1. shows a picture of a scissor jackconsisting in the base structure, the lower and upper arms, the screw component which connects the two supports and operates the jack, and the top bracket which is the part that the car is attached to.
AIR POWERED/PNEUMATIC JACK - Pneumatic jacks have a very different structure compared to scissor jacks. This type of structure requires much less input force by the user to operate the product. Instead of using a simple mechanical structure, it uses pressurised gases to create mechanical motion. It consists of a piston that when pressurised gases are let into this piston, it expands, forcing the structure to rise. This structure also consists in having an air control valve that controls the amount of compressed air going into the piston. This valve is then opened to let the gases escape and lower the structure.
These types of jacks have an average lifespan of 10 years if operated properly and regularly serviced.
The efficiency of pneumatic jacks is lower when compared to other structured such as hydraulic; this is because pneumatic jacks are powered by air and the moisture in the air can cause pneumatic tools to freeze up, making them unusable. These jacks are also loud to use and not as precise as some others because the air that is used is more compressible therefore cannot be controlled as precisely. There is also another issue with these types of jacks, the hose that connects the air compressor to the jack structure, if not tightened properly, can break free and move in the air at high speeds, this could be potentially dangerous to the operator.
There is also a newer version of this type of jack which consists in having a hose that connect the exhaust pipe of a car to the main body and by having the car running, the fumes from the exhaust, instead of escaping into the atmosphere, they are collected by this pipe and forced to go in the main body of the jack (balloon), causing it to inflate and lift the car; the vehicle can remain lifted for up to 45 minutes. As the structure of this is made from very soft materials, it would make the vehicle very unstable during operation.
Fig.2. shows a picture of an air powered jack with leavers to control the amount of compressed air going into the lifting mechanism.
Fig.3. shows the new type of air powered jack, with hose attached to the exhaust of a car.
http://www.engadget.com - Titan's air jack lifts your car with hot air-2012
http://www.ehow.com - Car jack specifiations-2012
Figure 2 - air powered jack - www.liftandshift.com - 2012
Figure 3 - New compressed air jack - www.engadget.com - 2012
HYDRAULIC JACK - A hydraulic jack has a structure that uses a liquid to push and operate a piston for the lifting of the structure. This type of mechanism uses Pascal's principle which states that if there are two cylinders connected to each other, by applying a force to the smaller cylinder, would result in the same amount of force in the large cylinder but as the larger cylinder has a bigger area, the output force would be greater. The more the difference in size of the cylinders, the higher the output forces.
The mechanism of this is represented by the following equation:
F=PA F=force P=Pressure A=Area
As shown above, the pressure that would be applied in the small cylinder is the same as the one in the larger cylinder but by having a bigger area to be multiplied by, it creates a larger force.
This type of structure consists in the reservoir which stores the hydraulic fluid, a pump which draws the fluid that is operated by a leaver: by pulling the leaver up, it allows the fluid to enter the small cylinder and by pushing the leaver back down, it forces the fluid to enter the main piston causing it to expand, allowing the structure to rise. There is also a valve that stops fluids from escaping from each cylinder. When the jack needs to be lowered back down, a release valve is opened which allows the fluid to go back in the reservoir.
Fig.4. represents a hydraulic jack with the leaver that allows the circulation of the fluid from the pipes to the small and main cylinder.
http://www.ehow.co.uk/ - Car jack specifications - 2012
http://www.physlink.com - How does a hydraulic jack work?-2012http://merchantmachinery.com/wp-content/uploads/2010/04/three-ton-hydraulic-jacks.jpg
Figure 4 - Hydraulic jack - www.merchantmachinery.com - 2010
ADVANTAGES AND DISADVANTAGES OF DIFFERENT JACKS
TYPE OF JACK
Easy to operate.
Low input force for operation.
No cost to run.
Supports less weight when compared to others.
Material can snag under pressure.
Lift heavier load compared to others.
Low input force.
Less power needed compared to Pneumatic.
Stronger than pneumatic.
High initial cost.
Occupies a lot of space.
Risks of leaks.
Possible fire hazard (oil leaks).
High pressure fluid can leak at high velocity and cause harm.
Oil must be filtered regularly.
AIR POWERED/PNEUMATIC JACK
Quieter compared to hydraulic jack.
Stronger than scissor jack.
Lower initial cost compared to hydraulic.
If leaks occur, there is no mess as its compressed air.
More expensive than scissor jack.
Expensive to run.
Occupies a lot of space.
Some systems use gas that could be toxic instead of compressed air.
Table - Advantages/disadvantages of car jacks
http://www.ei.org/ - Engineering information-2012
http://www.enme.umd.edu/ - 'Portable contrsuction trash compactor'-2012
All the types of car jacks researched share the same problems that were stated in the proposal document.
The problems that will be attempted to solve are:
The operation of the car jack on un-even, off road surfaces as well as on the road.
The operation of the car jack in poor or no light conditions.
The ease of use of the car jacks (the aim is to design an attachment that would make the operator know how to use the tool, even if they have no experience in the operation.
Sustainability is a big problem in the world of today; an aim that would help to solve this problem by designing a jack structure that is very sustainable, but at the same time, needs to have equal or better properties than existing products.
EXISTING OFF-ROAD JACKS DESIGNS
The high lift jack is a mechanical device used to lift cars in a vertical direction while being off road. They are usually built with a combination of cast and stamped steel. They have a very large structure that varies from 36 to 60 inches in height.
As shown in fig.5. the jack consists in a long bar that allows the high to occur, a steel handle for its operation, a handle spring clip which holds the handle in position, a large base unit for stability and an extruded component that is hooked to the car that needs lifting. The long bar also has climbing pins which allow the mechanism to rise and not fall down to its original position.
The maximum weight that this type of jack can hold is 2273kg.
Even if this type of jack can hold a large amount of weight, there are some important problems with the structure; being such a large tool, it can't be stored in an everyday car as heights can reach up to 4ft. Another problem with this product is its weight; being such a large tool it weighs 14kg which means that not everyone is able to operate it with ease. It is also an expensive tool and having so much material, not as sustainable as it could be.http://shoreline4x4.com.au/images/60%20high%20lift%20jack.png
http://shoreline4x4.com - High lift heavy duty 60" jack-2012
Figure 5 - Hi-lift jack - www.shoreline4x4.com - 2012Fig.5 shows an image of the Hi-lift car jack, consisting of the base unit, the height bar and the leaver that allows the lifting due to the climbing pins.
SAND CAR JACK
The name of this type of car jack explains its purpose; this is an off road jack that is easily operated on sand.
There isn't much information on this particular tool but the information gathered show that it has wide, anti-flotation tyres for easy movement on the sand and capable of lifting the weight; it can lift a structure up to 1.5 tonnes and it has a 14 inch stroke for easy lifting.
Its axels are made from 1 ¼ inch diameter steel and hubs made from 6061 with pressed in oil-lite bushings to handle the weight.
Considering the size of the tool, it can be relatively light when compared to the hi-lift jack.
This is a good tool for the operation on sand, but it too has some problems and disadvantages:
Like the hi-lift jack it has a large structure that cannot be stored in a car easily, it's only suitable on sand surfaces and cost between £100 and £200.
The main problem with this type of structure is that it wouldn't be able to be operated on different surfaces as the wheel might start to roll as this type of jack does not have a brake, and also it wouldn't be suitable for un-even harder surfaces such as mud or fields where the wheels cannot sink in as much as they would on sand. Finally, having such a large structure, the product is not as sustainable as it potentially can be.
http://www.duneguide.com/ - Product review - Sand car jack-2010
Fig.6. shows a picture of the sand car jack being operated (lifting an off road buggy on sand).
Figure 6 - Sand car jack - www.duneguide.com - 2010It shows the wheels that are sunk in the sand for stability of the structure; as stated above, this would not be the case on different types of surfaces.
MATERIALS CURRENTLY USED FOR MANUFACTURING OF JACKS
MEDIUM CARBON STEEL
LOW ALLOY STEEL
Table 2 - Properties of materials - CES Edupack - 2012
After researching existing car jack products it came to the conclusion that there is a big market for off road jacks usage on uneven grounds.
This is because, all the existing car jacks that cars are equipped with are designed to be operated on the road, and the ones that are designed for off-road use have limited operations; for example the sand jack is limited for usage only on sand surfaces as the wheels would not give the same support on different surfaces; this is because if it is operated on a different surface, the wheels might roll, causing the jack to move, and they wouldn't be able to sink in the ground properly to gain stability. The Hi-lift car jack, even being able to be operated on different surfaces, it has a very large structure and it could be potentially difficult and dangerous to handle and operate. Both of these types of jacks are not very sustainable as they use a lot of materials to be manufactured. The biggest problem that all the above jacks have also in common is that they can only be operated on relatively flat surfaces; they would not be able to be operated if the surface is un-even.
There are also some other minor problems which when solved, would improve the quality and use of the product; for example, an off road jack would be used off road, which means that the surroundings of the area where it would need to be operated could have low/no illumination; this could possibly be solved by having small LED lights attached to its structure. Another slight problem is the knowledge of operation; some users might not have any knowledge on how to use a car jack and might attach it to the car in the wrong way, so by having a very simple and clear attachment it could make the operation much easier.
All these major problems could be solved by having a smaller structure which requires less material, having a base unit that would be suitable for all different types of grounds (on and off road) and studying materials to discover the most efficient one fit for its job, considering cost, strength and the environment.
More in depth, possible solutions evaluation will be carried out to finalise the different solutions and solve the problems.
When researching for new possible solutions to solve problems, the user has to be careful that the new design is "legal". This means that some general research has to be done on existing patents to make sure that the design is not copied from patents. This includes every part of the structure, from the entire frame, to smaller parts such as the attachment of the jack for cars.
These are a couple of examples of existing patents that designers have patented for copyright reasons:
Google patents, 1936 'vehicle jack' Patent num. 2054211
Figure 7 - Car jack attachment patent -1936- Google patents.
Fig.7. shows some technical drawings of a patented component of a car jack. This specific component is an attachment for vehicles. It shows different views of the component and includes section views to explain further how the part works. This is patent 2054211 which has an issue date of the 15th of September 1936. It also has a description of the component stating what it is and how it works included within the patent document. (see appendix â€¦.. for full patent)
Figure 7 - Car jack structure patent - 1974 - Google patents
Fig.7. shows a drawing of another patented design; this is a patent for the entire structure of the jack. It explains how the structure works to lift vehicles up. The full patent also has different views of the design and different sections such as the background and summary of the invention.
At the beginning of the patent there is also an abstract which is a couple of sentences explaining what the patent consists in and how the product works. (See appendixâ€¦. for full patent.)
Google patents, 1974 'Extendable mechanism' Patent num. 3806093
As stated before, the current jacks that are out in the market of today have some problems; to try and overcome the problems some possible solutions were generated in terms of new designs. These potential solutions will then be evaluated using specific quality tools that will be researched to discover which potential solution is the most suitable one for this project.
OPERATING AT NIGHT
The first problem that was evaluated was the operation of the jack in poor or no light conditions; this is a big problem as the type of jack that will be designed is for off road use, which means that there would be a high chance that the operator would have to use the jack in a poorly lit area.
There are a couple of possible solutions that can potentially be used to overcome this problem; the first solution is to have a structure that would glow in the dark; this way the user can see where the jack is placed and attached to the car. There are also more feasible solutions such as attaching some LED lights to the base of the structure; this would allow the user to easily see both the jack and the section of the car that the jack needs to be attached to. The attachment of the LED lights also split into more potential solutions when the power to run them is considered; the source of power used could be from a simple battery placed inside the base of the jack, another more sustainable source of power could be using kinetic energy; the LEDs would be connected to a mechanism that generates energy by turning a handle multiple times, attached to the base. The final potential solution is having solar powered LEDs. This would consists in the LEDs being connected to small solar panels attached to the jack's supports which would produce energy; this solution does have a problem as normally, the jack would be stored in the car where it cannot get any sun-light to charge the battery that would operate the LEDs.
OPERATING ON OFF-ROAD/UN-EVEN SURFACES
Another problem that was looked at is the most important problem for the usage of this type of jack; the problem of operation on off-road/un-even surfaces. The first potential solution was to have a bigger base unit that would help to spread the weight of the vehicle, allowing the jack to remain on the surface and not sink in, this would work off-road but not on un-even surfaces; this problem was solved by placing six legs perpendicular to the base of the jack to allow a stable structure.
Another solution was to attach a tripod type structure to the base; it would have three legs at an angle which are attached by a large (20-30mm diameter) threaded component; the base unit would have a threaded hole to allow the tripod to be screwed on and off easily. This would cause all the stress of the structure to concentrate on the attachment of the legs, so the legs would have to be designed in a very strong structure that would support the weight.
A different type of legs attachment was also sketched; this is a simpler design; it is similar to the tripod structure but all it consists in is three legs with a threaded area at the top that would simply screw in the base unit thanks to the threaded holes
Fitting mechanisms can vary in cars so this is a problem that could potentially be solved by improving the fitting of the jack.
The first solution was to design a simple long circular component which would be permanently attached to the bottom of the car (male) and having another attachment on the jack (female) that would slot in the component on the car, creating a tight and stable fit. This would make the operation clearer and easier to do.
The other potential solution was to design a component attached to the jack that started with a big surface attachment that would gradually decrease until the two ends would meet; this would allow the attachment to be a universal fit, at different sizes of car attachments can be attached to this jack thanks to the change of length of this particular component.
TYPE OF STRUCTURE
Many different types of structures were considered such as hydraulic and pneumatic powered jack, but only simple mechanical structures were used in the possible solutions, as one of the aims of this project is to keep the product, cheap and sustainable.
One type of structure method is to use gears, by having a main gear that is powered by a handle operated by the user would force a second or even a third gear to rotate which would be attached to a component that would rise and contract according to the rotation. This turns rotary motion to linear motion but it does not change horizontal force to vertical.
The other type of structure consists in using a simple structure made with standard supporting arms that would use a threaded component to the operation; this uses the same method as a scissor jack. This type of structure also turns rotary motion to linear, and changes horizontal force to vertical.
(includeâ€¦â€¦"refer to appendixâ€¦.. " ) (scan sketches to put in appendix)
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http://www.walmart.com/ip/Torin-Jacks-1.5-Ton-Scissor-Jack/14560046 Date accessed 15/10/2012
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http://www.liftandshift.com.au/index.php?fuseaction=product.view&productid=137&ctu=&type=&lvl=1 Date accessed 15/10/2012
Tim Stevens, 2012 'Titan's air jack lifts your car with hot air' [online]
Date accessed 15/10/2012
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http://www.ehow.co.uk/list_7674036_car-jack-specifications.html Date accessed 01/10/2012
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http://merchantmachinery.com/tag/hydraulic-jacks/ Date accessed 15/1/2012
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http://www.ei.org/node/101 Date accessed 24/10/2012
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http://www.enme.umd.edu/undergrad/designday/sp2010/documents/portableconstruction-poster.pdf Date accessed 24/10/2012
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Date accessed 24/10/2012
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Date accessed 24/10/2012
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http://www.offroadadventures.com/articles/view/id/347 Date accessed 24/10/2012
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http://www.hi-lift.com/media/pdfs/jack_instructions.pdf Date accessed 24/10/2012
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http://shoreline4x4.com.au/high-lift-heavy-duty-60-jack-p-802.html Date accessed 24/10/2012
Crowley Offroad LLC, 2010 'Product review - Sand car jack' [online]
http://www.duneguide.com/ProductReview_SandCarJack.htm Date accessed 25/10/2010
Ehow, 2012 'Pneumatic jack guide' [online]
http://www.ehow.com/way_5815004_pneumatic-jack-guide.html Date accessed 29/10/2012
Gaurav Kumar-Physlink, 2012 'How does a hydraulic jack work?' [online]
http://www.physlink.com/education/askexperts/ae526.cfm Date accessed 29/10/2012
Tom C. White, 1936 'vehicle jack' [online] Patent num. 2054211
Date accessed 01/11/2012
Fumio Itazu, 1974 'Extendable mechanism' [online] Patent num.3806093
http://www.google.com/patents?id=oF0rAAAAEBAJ&pg=PA2&source=gbs_selected_pages&cad=2#v=onepage&q&f=false Date accessed 01/11/2012
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