Car jack

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Executive Summary

Our group has chosen to look into the car jack product, produced by Initech. By analyzing the current product in great depth we hope to find opportunities to improve or add to your current product line. Our early steps in the process have included identifying aspects such as the customer needs, how the product functions, and general information about the product. The general idea being that the jack must be able to easily lift a corner of a car under many different circumstances, to allow the user to change a tire. This must be done safely and at the time the user needs this to be done. Next, we undertook a complete disassembly of the jack to become familiar with it, and begin to look at how it was manufactured, and the decisions made as part of the manufacturing process. The jack was built to a fairly simple design, the user rotates the crank arm which rotates the threaded rod, causing the arms to be pulled together raising the top of the jack and in turn the car. The disassembly gave us a good idea of what role each component plays and what effect they have on the complete device. Major components include, a base that sits on the ground and stabilizes the jack, arms that rotate at points generating a 4-bar linkage , top piece that connects to the car, a threaded rod that pull the arms together, causing the top to raise, and a thrust bearing that allows the threaded rod to rotate under force. In terms of manufacturing, parts are mostly stamped and bend sheet steel. It appears that the arms use the same die, again to make the process simpler and more cost effective. Upon becoming completely familiar with the product we then were able to use the knowledge we acquired to conduct a failure mode effects analysis (FMEA), design or manufacture analysis (DMA) , and design for assembly analysis (DFA). The FMEA, helped us to identify the different failure modes, most of which result on the part of the user and not through mechanical failure. The DMA further confirmed our post dissection conjectures about the manufacture of the jack. The DFA showed that the jack was designed to be easily assembled, but not easily disassembed, probably for user safety. A design for environment (DFE) analysis show that there was no environmental impact to using the device, and at end of live it can easly be recycled as scrap steel. We have also begun to conduct a preliminary analysis of the mechanics involved in the device, including the general functioning and when and why it can fail. This went into the FMEA, showing that failure will most likely result through user error rather than the mechanical failure of the jack. From all of this we have been able to gain a significant background in the product and see areas where improvement is possible, including such options as lighting, and more instruction on changing a tire.

Group Members

  • Matt Wasserman
  • Alberto Guzman
  • Sarun Soongsawang

Product Study

The first step in our analysis of the product was to conduct a product study looking a the various aspects of the car jack, to gain a better understanding of the reasons for use, how it is used, and what other aspects need to be taken into consideration for a redesign.

Function (Customer Needs)

Identifying the customer needs as well as the function of the product a necessary step in the product analysis. By identifying the needs and the function we can see what the necessary requirements are for the redesign. The customer needs/functions we identified are:

  • Typically used to lift up the corner of a car, normally for changing a tire.
  • This has to be done consistently, with minimal user input in circumstances that can be less than ideal.
  • This also must be done safely


Input represents what the user has to do, the input they have to give, to cause the system to function. For the car jack, the input is rotation the crank, which in turn rotates the threaded rod, causing the jack to raise.


The output is the result from the user input. In the case of the car jack the output is vertical motion up or down that locks in place. As a result of the design, this upward motion imparts a force, which is normally used to lift a car.

Normal Use

By studying the normal use we can see what the users as well as the jack go though during a typical use. This helps to give us an idea of opportunities for improvement. The typical use of the car jack is as follows:

  1. User kneels down in next to car.
  2. Jack is placed flat under car.
  3. Crank arm end placed into eyelet of jack.
  4. Crank arm held up in one hand and rotated clockwise with the other.
  5. When rotated, threaded rod also rotates pulling together arms, and creating a vertical motion.
  6. When vertical motion of jack gets close to car frame, user aligns jack as necessary make sure it is securely aligned with the pinch weld on the car's frame.
  7. User continues to rotate crank arm as the jack lifts the car until the desired height is reached.
  8. After the user is done changing the tire the crank arm is rotated counter-clockwise until the jack is completely closed.

While this is just the usage of the car jack it is usually used in part of a larger process of changing a tire. The basic process of changing a tire is as follows:

  1. Park car, and pull parking brake.
  2. Use breaker bar to loosen lug nuts by rotating them slightly counter clockwise.
  3. Use car jack as shown above to raise car.
  4. Loosen and remove lug nuts.
  5. Remove tire and replace with spare.
  6. Put lug nuts on and hand tighten.
  7. Tighten lug nuts with breaker bar tightening bolts across from each other, in basically a star pattern.
  8. Lower jack as explained above.
  9. Clean up and put items used away.

Special Considerations

In our study of the usage, and interviews we encountered many different situations where there were problems during usage. These special considerations are:

  • Might be difficult for some users to kneel down next to car and reach under for correct placement.
  • Depending on lighting, can be difficult to ensure proper alignment.
  • When rotating crank arm it is easy to bash knuckles into the ground
  • Must be careful (cannot rotate to fast, must be in right position) when rotating or else the entire jack, not just the threaded rod, rotates. The jack must then be repositioned. This is the case when the jack has not yet secured itself between the car and the ground.

Other Uses

While the typical use of the jack is to lift part of a car when changing a tire, in our study we found other uses. They are:

  • Separating two objects
  • Bending Pipe
  • Lift heavy objects
  • Push heavy objects.


The stakeholders are all the people who have an interest in the product. This is at all levels from usability to profit. The stakeholders we identified for the jack are:

  • Car driver/passenger (user)
    • They must use the actual product
  • Car Manufacturer
    • They must contract to another company or design and manufacture a jack to go with each automobile
  • Jack manufacturer, if not part of car company
    • They must design and build the jack for the car company or as an after-market replacement
  • Employees of car or jack manufacturer
    • They play a role in the design or manufacture of the jack and are paid for that role
  • Business and employees that sell after-market jacks
    • They sell and make a profit off of the after-market jacks
  • Suppliers and distributors of after-market jacks
    • Supply and distribute after-market jacks to companies to sell

Product Dissection and Mechanical Function

From the dissection of our study car jack were were able to learn a considerable bit about how the jack worked mechanically, components, materials, design and manufacture of the device. Generally, the jack was designed to be manufactured quickly and easily with a few components. Also it was made such that it could not be taken apart by the user. Most of the components are stamped and bend sheet steel, for quick and easy manufacture. A few components, like the arms, which have the same weights, are stamped using the same die, and just bent differently, again to simplify the manufacturing process. Using the top and bottom pins like rivets prevents the user from disassembling the jack, for reasons of ensuring safe use of the device and ensuring stability. Complete documentation of the dissection as well as an explanation of the mechanical function of the jack can be found on the Car jack product dissection page.

Design for manufacturing and assembly (DFMA)


During the dissection of the car jack it became quickly apparent that this product was not intended to be disassembled. All of the fasteners has been mechanical fixed using either a rivet or other forums of plastic deformation of steel to secure it to the complete assembly. Dissecting the jack required destroying these connection. This method of assembly reduces the possibility of a user disassembling the product and reassembling it in an incorrect and unsafe way. It is critical that these fasteners be secure as a failure of any component of this product could result in serious injury or death of the user. The fasteners used to join the upper and lower arms as well as the upper and lower base serve multiple purposes, both hold the parts together as well as acting as pivots to allow motion of the device. In other parts such as the collar the use of a separate fastener has been avoided by simply crushing the collar into to the thread. This securely fixes the two parts together without the need of an additional part.

These methods of assembly have been chosen to prevent user tampering. By ensuring a user cannot unknowingly modify the product. It insures the product will be safe to use anytime it is needed.


This jack has been designed to minimize manufacturing costs. The parts have been designed to be symmetric thus minimizing the number of unique parts required. For example the left and right upper arms are the same exact part utilizing the same dies during production. The left and right pins only differ in that one has a thru-hole while the other is tapped. There seems to be only two gauges of sheet steel used in the construction of this jack. This minimizes the number of separate raw materials that would have to be purchased to construct the product. By minimizing the number of different raw materials required, larger amount of necessary material can be ordered resulting in savings from buying larger quantiles.

Many expensive car jacks exist on the market. Some costing upwards of $200. This style of jack has been designed as an economic choice that is just as functional as any more expensive product. Keeping costs low encourages consumers to buy one of these products knowing it can be a very usefully tool in an emergency situation.

Design For Environment (DFE)

This style of car jack (manual screw jack) will require no renewable energy input during its construction. Energy will be needed to produce the steel used by all of the parts. Energy will also be used to run the machines that do the stamping/forming/assembly of the parts. Unlike hydraulic jacks which may require oil during there usage cycle this jack has been lubricated at the factory for the life of the product. The only input of energy needed during usage is work from the user.

This jack is made entirely out of steel. Parts have been coated with either a powder coat or some form of electro plating to protect them from the elements. Since all parts of this product are the same material recycling it would not require manual disassembly. The entire product could be shredded and sold as scrap steel to be recycled.

Failure Mode Effects Analysis (FMEA)

In the process of conducting the failure mode effects analysis, we were able to see that most of the failure modes dealt more with the user, than the jack itself. Preliminary analysis of the jack showed that it could stand up to a significant amount of force before failure, much more than it would take under normal usage. Where safety concerns come into play come mostly from users not using the product as intended or using it incorrectly. The complete analysis can be viewed on the Car Jack Failure Mode Effects Analysis page.

Preliminary Analysis

To go with the analysis of the car jack from the design, usability, and manufacturing standpoints we have bgun conducting a preliminary analysis from a mechanical standpoint. This is discussed in further detail in the page Car Jack Preliminary Analysis

Opportunities for Improvement

In our continuing study we have identified many different opportunities to improve the product. Identifying these opportunities is a work in progress, they are currently:

  • Automating the rotation of the threaded rod to prevent scraped knuckles, or to make the product easier and more convenient to use.
  • A better breaker bar for removing lug nuts,that is still of a compact size, but provides better leverage. Most breaker bas that come with the jack do not provide enough leverage.
  • A better way to ensure alignment of jack with car frame.
  • A way to improve visibility under car when aligning the jack with the car frame.
  • Improve lighting near jack/tire when using this product during the night.
  • Clear directions for a user who is not experienced using the jack.
  • Storage for any tools/lug nuts that may be needed during the use of this jack.
  • Problem with adding a light for visibility, people forget to check and have spare batteries in the car.

Ideas For Improvement

To go along with the opportunities for improvement we have identified, are some preliminary ideas on how to accomplish them. These are:

  • Device to rotate threaded rod, powered by the car.
  • Redesign breaker bar to make it compact, maybe collapsible.
  • Design an alignment device to make securing to frame easier.
  • Add a light source, maybe LEDs into the breaker bar.
  • Develop photographic instructions on the proper use of the jack and how to change a tire.
  • Add a case, threads or a magnetic strip where the lug nuts could go to prevent them from getting lost.
  • Maybe design a quick charge device that can plug into jack and charge batteries for light.
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