Hydraulic jack
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Contents |
Executive Summary
In order to learn more about the process of designing a part, group 10 took apart a Big Red car Jack. The device is designed to use hydraulic fluid and one-way valves to raise a ram rod so as to lift 4-ton vehicles in order for the user to be able to change tires. The jack is operated using a removable handle, which is pumped up and down, raising the jack, which in turn lifts the car.
After testing and dissection, we concluded that the jack was both easy to use and very compact. The jack did not take very long to achieve the desired result and required minimal energy to use. In order to get a better understanding of the jack we performed Failure Modes and Effects Analysis (FMEA), Design for Manufacture and Assembly (DFMA) and Design for Environment (DFE).
FMEA allowed the group to get a better understanding of the failure modes and the impact the failure modes had on the user. One possible failure mode is the jack could slip from under the car causing the elevated car to fall on the user.
DFMA gave us knowledge on the manufacturing and assembly. We concluded that the product and the manufacturing had been fairly optimized since the product does not have very many extraneous parts and the product is relatively cheap.
DFE showed the group the environmental impact of the jack. EIO-LCA (Economic Input Output-Life Cycle Analysis) was used to see the greenhouse gas emission over the lifetime of the product in the various sectors of the US economy. It was concluded that the production of the hydraulic fluid had the largest percentage of Carbon.
Stakeholder Needs
The main stakeholder for this product is the consumer. The consumer is the main person operating the device and is the one who will suffer the most if it fails. Cost, reliability and safety are a few of the needs the consumer has from the product. However, the consumer isn’t the only group that this product has an impact on. Retailers, manufacturers, and Shippers/transporters also have interactions with the product.
Consumers
- Cheap
- Reliable/Maintainable
- Easy to use
- Safe
- Moveable between cars
- Compact/Light
Retailers
- Easily displayable
- High Demand
- Low to no maintenance required
- Profitable
Manufactures
- Made from common materials
- Few parts
- Easily assembled
- Assembly can be automated to reduce cost
- Replaceable parts
- High demand
Shipping/Transport
- High Demand
- Easily shippable/Light weight
- Durable
Product Functionality
Step-by-Step Instructions
To raise:
- Turn valve screw clockwise to tighten it and create a pressure seal
- Place jack under car and turn extender rod until it reaches the bottom of the car
- Insert handle into pump handle housing
- Raise and lower handle to pump up car
To lower:
- Turn valve screw clockwise
- Twist down extender rod
- Pull jack out from under car
Usability Study
How it's used
The Big Red Hydraulic Bottle Jack can be operated with everything in the packaging. It does not need any additional fluid, or an electrical source. The eight-pound jack can lift vehicles weighing up to 4 tons simply by moving a handle up and down. Once the vehicle is lifted the jack can maintain the car at the required height to change a tire. To compensate for different size cars, a worm screw is attached at the top tat can extend upwards to assist in the lifting of cars that are taller.
User Study
When the group tested the jack, without using the instruction, we found the jack very confusing. However, once we read the instructions and tried operating it, we discovered that the jack was in fact very easy to use. Although it was easy to use, there were some problems with the jack. It had trouble getting under smaller cars, which is understandable since it is designed for 4-ton cars. Also pumping the handle was challenging since the user had to kneel on the ground and lift the handle once it was lowered to pump it repeatedly. The release screw was also difficult to rotate by hand. However, with the handle bar inserted, the task became easier, but still challenging.
One of our group members gave the jack without instructions to another Carnegie Mellon student and had them jack up their car. Without help, the person also struggled initially using the jack, but ultimately decided that the jack was very compact and easy to use.
After doing research and self evaluations on the jack, the group has concluded that the item is very compact and light for a jack. The group also concluded that its size makes it very easy to store in a car and the design makes the jack very easy to use. Since there aren’t very many exposed moving parts and there is not combustion, the jack is fairly safe. Its steel design also makes it very robust and hard to damage. Some of the corrections the group would make is possible widening the base to prevent tipping as well as improving the handle to prevent it from getting lost. Also allowing the jack to work for a larger variety of cars cold be another improvement.
Assembly
The following is an exploded view of the hydraulic jack. The parts each number corresponds to are listed below the picture and in the Bill of Materials section.
1. Inner Handle
2. Outer Handle
3. Alligator Clip
4. Pins
5. Pump Connector Rod
6. Link Connector Screw
7. Pump Handle Housing
8. Pump Rod
9. Pump O-Ring
10. Pump Plastic Ring
11. Pump Housing
12. Pump Housing Washer
13. Valve Screw
14. Valve Screw O-Ring
15. Valve Ball Bearing
16. Base
17. Plastic Bumper
18. Plastic Fluid Filter
19. Base Plastic Washer
20. Ramrod Rubber O-Ring
21. Ramrod Plastic O-Ring Retainer
22. Ramrod Base
23. Ramrod Shell
24. Extender Screw
25. Inner Chamber
26. Outer Cylinder
27. Rubber Plug
28. Large Plastic Cap Ring
29. Outer Cylinder Screw Cap
30. English Warnings
31. Alternate Language Warnings
Bill of Materials
The following is a list of the 31 parts that make up the hydraulic bottle jack. Most pieces are made of steel, that has been shopped in some way, usually on a mill or a lathe. The non steel parts are either rubber or plastic and are purchased or injection molded. The table can be sorted by Part Number, Quantity, Weight, Material, and Manufacturing Process.
Part Number | Name | Quantity | Weight (g) | Function | Material | Manufacturing Process | Image |
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1 | Inner Handle | 1 | 78 | Inner handle piece, used to pump fluid | Painted steel | Bent, Welded | |
2 | Outer Handle | 1 | 134 | Outer handle piece, used to pump fluid | Painted steel | Bent, Welded | |
3 | Alligator Clip | 2 | <1 | Used to hold Pins (#4) in place | Aluminum | Purchased | |
4 | Pin | 2 | 7 | Used to hold pump structure together | Steel | Purchased | |
5 | Pump Connector Rod | 2 | 25 | Connects Pump Handle Housing (#6) to Base (#16) | Painted steel | Stamped | |
6 | Link Connector Screw | 1 | 5 | Connects Pump Connector Rods (#5) to Pump Handle Housing (#7) | Painted steel | Riveting | |
7 | Pump Handle Housing | 1 | 98 | Connects handle (#1&2) to Pump Rod (#8) | Painted steel | Stamped, Bent, Welded | |
8 | Pump Rod | 1 | 42 | Moves up and down to pressurize the jack | Painted steel | Automated Lathe Process, Drilled | |
9 | Pump O-RIng | 1 | <1 | Creates a pressure seal for the pump | Rubber | Purchased | |
10 | Pump Plastic Ring | 1 | <1 | Holds the Pump O-RIng (#9) in place | Plastic | Purchased | |
11 | Pump Housing | 1 | 74 | Limits the Pump Rod (#8) motion to 1D | Painted steel | Automated Lathe Process, Threaded | |
12 | Pump Housing Washer | 1 | 1 | Provides separation between the base and the bottom of the Pump Housing (#11) | Steel | Purchased | |
13 | Valve Screw | 1 | 18 | Allows for release of pressure in jack | Painted steel | Automated Lathe Process, Threaded, Stamped | |
14 | Valve Screw O-RIng | 1 | <1 | Creates pressure seal around the Valve Screw (#13) | Rubber | Purchased | |
15 | Valve Ball Bearing | 3 | 1 | Creates or releases liquid seal allowing for flow between chambers | Steel | Purchased | |
16 | Base | 1 | 1049 | Holds entire jack together, houses the various valves in the jack | Painted steel | Cast Steel, Automated Mill Process, Threaded | |
17 | Plastic Bumper | 1 | <1 | Holds Valve Ball Bearing (#15) in place | Plastic | Injection Molded | |
18 | Plastic Fluid Filter | 1 | <1 | Filters debris during liquid flow | Plastic | Injection Molded | |
19 | Base Plastic Washer | 1 | <1 | Seals base of Inner Chamber (#25) | Plastic | Purchased | |
20 | Ramrod Rubber O-Ring | 1 | <1 | Creates pressure seal around Ramrod Shell (#23) | Rubber | Purchased | |
21 | Ramrod Plastic O-Ring Retainer | 1 | 1 | Holds Ramrod Rubber O-RIng (#20) in place | Plastic | Purchased | |
22 | Ramrod Base | 1 | 98 | Keeps liquid out of Ramrod Shell (#23) and prevents sticking to Base (#16) | Steel | Automated Lathe Process | |
23 | Ramrod Shell | 1 | 310 | Moves up and down lifting and lowering anything on the jack | Steel | Automated Lathe Process, Threaded | |
24 | Extender Screw | 1 | 176 | Allows for extra heigh to be reached by the jack | Steel | Automated Lathe Process, Threaded, Riveted | |
25 | Inner Chamber | 1 | 314 | Constrains Ramrod Shell (#23) to 1D motion | Steel | Automated Lathe Process, Threaded | |
26 | Outer Cylinder | 1 | 405 | Houses liquid | Painted steel | Stamped, Bent, Welding | |
27 | Rubber Plug | 1 | <1 | Allows for initial filling of jack with hydraulic fluid | Rubber | Purchased | |
28 | Large Plastic Cap Ring | 1 | <1 | Prevents rubbing between Outer Cylinder Screw Cap (#29) and Outer Cylinder (#26) | Plastic | Purchased | |
29 | Outer Cylinder Screw Cap | 1 | 160 | Caps jack and prevents pressure leak | Painted steel | Cast Steel, Automated Lathe Process, Drilled, Threaded | |
30 | English Warnings | 1 | <1 | Provides warnings in English | Paper | Printed | |
31 | Alternate Language Warnings | 1 | <1 | Provides warnings in Spanish and French | Paper | Printed |
Mechanical Function
The jack is made up of a series of concentric cylinders each of which is pressurized and holds differing amounts of hydraulic fluid. When the handle is inserted into the pump mechanism and moved up and down, fluid is pumped from a reservoir in the outer cylinder into the space in the bottom of the inner chamber, pushing the ramrod shell upward. This fluid is kept inside the inner cylinder by a high-pressure valve located in the base of the jack, consisting of a check valve and a debris filter to keep unwanted solids from breaking the seal created by the ball bearing. The jack can be released by loosening the valve screw at the jack’s base, thus allowing the fluid to return to the outer cylinder until the valve screw is tightened again. This release of fluid will then lower the ramrod shell, lowering the car and allowing the jack to be removed. The ramrod also has a section that can be unscrewed, providing extra length to the mechanism.
Design for Manufacturing and Assembly (DFMA)
Chanshu Tongrun Auto, the company that manufactures this particular product, produced roughly 10 million car jacks in 2010 [1]. As a result, the jack is made with two primary design goals: sufficient strength to lift 4 tons of material off the ground and simple, easily mass-produced parts.
Manufacturing
Nearly all of the parts in the hydraulic bottle jack are either machined from steel stock or purchased from other suppliers, with the exception of the cast steel base and end cap. Most of the machined steel tubes appear to have been turned on a lathe in a job shop, but given Changshu Tongrun's incredibly high output, they were probably made in some sort of automated process.
Design for Manufacturing Features and Improvements | ||
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Design Objective | Strengths | Areas of Improvement |
Minimize Part Count |
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Standardize Components |
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Commonize Product Line |
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Standardize Design Features |
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Keep Designs Simple |
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Multifunctional Parts |
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Ease of fabrication |
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Avoid Tight Tolerances |
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Minimize Secondary & Finishing Operations |
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Assembly
To simplify assembly, nearly all of the parts are designed to screw into one another, eschewing complex fasteners or joints. The only major exception is the pump assembly, which experiences the greatest range of motion and is therefore held together with simple pin joints. In addition, almost the entire pump apparatus is contained within the cast steel base, making assembly significantly easier at the cost of making the part more difficult to manufacture.
Design for Assembly Features and Improvements | ||
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Design Objective | Strengths | Areas of Improvement |
Use Sub-assemblies |
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Mistake-Proofing |
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Minimize Fasteners |
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Minimize Handling |
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Minimize Assembly Direction |
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Provide Unobstructed Access |
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Maximize Assembly Compliance |
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Failure Modes and Effects Analysis (FMEA)
After considering all of our system components, we identified eight major areas where our product could fail. Most of the major areas are made up of external components of the product, parts which the user interacts with while he/she operates the system: the handle assembly, the pump structure, the base, the extended screw, the alligator clips, and the valve screw. Unless the product is dissected, the remaining areas cannot easily be reached.
Even though the probability of failure of the internal components is low, their severity and detection of failure are very high. If these parts needed to be replaced it would be extremely difficult for the user to take the system apart. We recommend a design that makes these parts more accessible. That way elements such as the hydraulic liquid and parts can be changed when needed. This will allow the user to maintain the jack which will guarantee safety and durability.
The external components failure depends on their design and on the user. The probability of the components failing ranges from moderate to high. If these parts fail, the system will not work properly and the user will potentially be placed in serious danger. In order to prevent such failures, we recommend redesign, testing, and new material designation for parts.
- FMEA Ratings are based on tables 14.12 ("Rating for Severity Failure"), 14.13 ("Rating for Occurrence of Failure"), & 14.14 ("Rating for Detection of Failure") from the textbook "Engineer Design" by Dieter, G. and L. Schmidt.
FMEA - Hydraulic Bottle Jack | |||||||||
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Item & Function | Failure Mode | Effects of Failure | S | Causes of Failure | O | Current Controls | D | RPN | Recommended Action |
Base | Tips Over | Car falls causing injury to the user and/or damage to the vehicle. | 10 | The jack is not properly placed under vehicle. The user does not place car supports after lifting. An uneven surface does not provide stability. | 4 | Position jack under a flat surface of the car, place supports, don't work on uneven ground. | 9 | 360 | Change the shape of the base, more surface area. Make a multifunctional package to use as support for base. |
Valve Screw | Removed, Leaks | Loss of hydraulic fluid. Balls bearings can fall out of place. | 9 | User unscrews the valve all the way out. | 6 | The manual instructs user on how to close and open valve. | 5 | 270 | Place a stopper in the inside to prevent user from turning the valve further once opened. |
Alligator Clips | Slip out/Deform | Pins fall out of place, pump structure no longer works. | 8 | Overload and misuse | 3 | Make sure to use pumping system appropriately. Do not overload pump connector rods. | 10 | 240 | Use a different way to connect pins. Change the pins to a screw-nut system and eliminate this part. |
Extender Screw | Placed on an uneven surface | Car may slip and screw bend | 8 | Jack is not properly placed under vehicle. | 4 | Position screw surface area under a flat area of the vehicle. | 8 | 224 | The shape of the contact area could be altered. |
Bends | Can no longer use the jack, component must be replaced. | 8 | Overload | 2 | Limit weight on screw | 9 | 144 | Make component a replaceable part. | |
Gets Jammed | Height cannot be adjusted. | 8 | Wear/Corrosion | 4 | Lubricate when needed | 3 | 96 | Provide lubrication oil with product. | |
Handle Assembly | Inner and/or outer handle bends. | Cannot properly pump the car jack. | 7 | Misuse or damage by customer. | 4 | Do not overload the material. Store it in a safe place | 8 | 224 | Design a rigid handle with a high Young's Modulus to resist deformation. |
The inner and outer handles separate. | Pumping the car jack becomes difficult and can lead to injury. | 3 | The user pulls while pumping which causes separation. | 7 | While pumping make sure the outer handle does not slip out of place. | 5 | 105 | Design a handle assembly that locks the inner and outer handle. | |
O-rings | Wear leads to breakage | Loss of hydraulic liquid | 10 | Wear | 2 | If the jack has not been used for a while or has been used for years, test that it works before lifting a vehicle. | 10 | 200 | Change system so it's easier for the customer to notice and maintain. |
Plastic Bumper | Gets out of position | One of the ball bearings will fall out of place. | 10 | Wear or lack of lubrication, can cause plastic part to break and pop out of place. | 2 | The hydraulic liquid is a multifunctional component that provides lubrication. | 10 | 200 | Allow the user to add liquid to the system if liquid lost. |
Pump Housing & Pump Connector Rods | While pumping/setting up the mechanism the user's finger(s) get stuck in between. | Immediate injury. | 6 | Improper use of handle. The user leaves finger(s) at the pin connection while pumping. | 5 | The user should keep hands at a safe distance. | 6 | 180 | Place a rubber stopper between the pump housing and the connector rods to prevent injury. |
One of the components bends. | Cannot properly pump the car jack. | 7 | Misuse or damage by customer. | 3 | Limit the force applied to these components. | 8 | 168 | Use a rigid material to resist deformation. As a customer prevent damage by using the product appropriately. |
Design for Environment (DFE)
This section discusses the major sources of greenhouse gas (GHG) emissions associated with this product, shown in detail in the table below. The largest source of GHG emissions from this product is the use of hydraulic fluid in the jack. This fluid is a petroleum product and is therefore made up of a large percentage of carbon. If congress were to pass a tax on CO2 emissions, the cost of the hydraulic fluid would be likely to increase, therefore increasing the initial cost and cost to maintain the jack. Cost of manufacturing the jack itself would also increase, but not so significantly as that of the fluid. That being said, overall the cost of both the jack and an initial fill of fluid is unlikely to increase by more than a dollar, so it wouldn't have a major impact on the sales of the jack. It is important to note that there are also GHG emissions associated with disposing of the jack. Because the fuel is petroleum based, it will release CO and CO2 into the environment as it decomposes. Recycling the jack would be a better option because you could safely dispose of the fuel and reuse the steel. Additionally, GHG emissions from the hydraulic fluid could be cut down by using a more environmentally friendly fluid such as a vegetable oil based product[3] or by choosing a fluid that does not need to be replaced so often.
Another area where GHG emissions can be reduced is in the manufacturing of the jack. Already many parts of the jack are manufactured by processes with relatively low energy intensity. Most notable are the parts made by stamping and bending sheet metal, which are processes requiring relatively low energy input. The manufacturing of many other parts of the jack, such as its inner cylinders, seem to have been produced by an automated lathe machine. These processes can be designed to reduce energy usage by minimizing machinery necessary for their production.
DFE - Hydraulic Bottle Jack | |||||||||
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Production | Use | End of Life | |||||||
Pump Manufacturing | Hydraulic Fluid | Landfill | Steel Recycling | ||||||
[9] | [5] | [10] | [11] | ||||||
Sector | #33221B: Handtool Manufacturing | #324199: All Other Petroleum and Coal Products Manufacturing | N/A | #331110: Iron and Steel Mills | |||||
Total mtCO2e/$1Million | 648 | 2160 | 3360 | ||||||
Unit | 1 Hydraulic Jack | 1 Bottle of 32oz AW-32 Hydraulic Oil [4] | 7 lbs of Steel | ||||||
Units Per Lifetime | 1 | 15 | 1 | ||||||
Cost per Unit | $15 | $5 | $1.26 | ||||||
Lifetime Cost | $15 | $75 | $1.26 | ||||||
Implied mtCO2e | 0.0097 | 0.16 | 0.012 | 0.0042 | |||||
Cost with CO2 Tax of $30/mt | $0.29 | $4.86 | $0.35 | $0.13 | |||||
Assumptions | *30 year lifetime | *Jack is frequently used and maintained *Replaced oil every 2 years [4] *Oil costs $5 for 32oz [5] | *Oil is petroleum based and therefore 85% carbon [6] *all of the carbon ends up as CO2 | *assumed it costs $360/ton of recycled steel [7] |
Notes on this table:
- The landfill CO2 is unlikely to be taxed, but are included here simply for reference.
- These results are approximate, as each sector represents a range of products far beyond what's involved in a car jack.
- If hydraulic fluid is changed every two years as recommended, then it is clearly the biggest source of CO2 emissions. However, if users rarely or never replace it, then CO2 emissions from the fluid will be on about the same scale as those from the other sources.
Team Member Roles
Melanie Jasper: Design for Environment (DFE) Lead
Derek Lessard: Design for Manufacturing and Assembly (DFMA) Lead
Daniel Mark: Bill of Materials and Mechanical Functions Lead
Gloriana Redondo: Failure Modes and Effects Analysis (FMEA) Lead
Daniel Tabrizi: Executive Summary, User Study, and Stakeholder Needs Lead
References
[1] Sales Volumn. http://www.tongrunjacks.com/static.php?id=5
[2] Dieter; Schmidt. Engineering Design, Fifth Edition. New York: McGraw-Hill, 2013
[3] http://en.wikipedia.org/wiki/Hydraulic_fluid
[4] http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=529258
[6] http://en.wikipedia.org/wiki/Petroleum#Composition
[7] http://www.steelonthenet.com/commodity-prices.htmlhttp://www.steelonthenet.com/commodity-prices.html
[8]Carnegie Mellon University Green Design Institute. (2008) Economic Input-Output Life Cycle Assessment (EIO-LCA), US 1997 Industry Benchmark model [Internet], Available from:<http://www.eiolca.net> Accessed 3 February, 2014.
[10]http://afexsystems.com/industries/landfill/
[11]http://thinkoutsidethebin.com/2011/04/30/anything-made-with-steel-can-be-easily-recycled/