CWU | MET
TESTING METHODS
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In total, there will be six mechanical powertrain tests. These tests will determine whether or not the powertrain system of the AutoJack has successfully met the set design requirements. These tests consist of a “Hydraulic Cylinder Power Test”, “Hydraulic Cylinder Speed Test”, “Total Collapsed Height Test”, “Total Expanded Height Test”, “Cross Rod Deflection Test”, and a “Total Powertrain Weight Test”. These tests have been briefly described below. It is important to note that these powertrain tests will be conducted at the same time as the other mechanical frame tests.
In order to evaluate the overall functionality and performance of the AutoJack, all of the mechanical (powertrain + frame) must be considered. Two of the most crucial features that the total system must be tested for are “lift stability” and “resistance to compressive loads”.
In order to test the lift stability of the AutoJack, the link arm system will be raised by charging the hydraulic cylinder with compressed air. As the system rises, pre-determined side loads (pushing and pulling) will be applied to the ends of the upper frame. Measurements will be taken during the applications of each load. If the system has less than 1inch of play in all directions (x, y, and z), the AutoJack lifting process may be considered stable.
In order to test the AutoJack’s resistance to compressive loads, the entire powertrain + frame assembly will be placed within a confined area of the power lab. The lower frame of the device will be secured to the ground using fasteners and clamps. Then, slabs of different weights will be added to the upper frame. With each increasing load increment, measurements will be taken at each critical point along the system. This will continue until either a 5000lb load has been achieved, or there is a system failure. In order to be considered successful in this test, the AutoJack must have less than a ¼ inch of material deflection at any point. If so, the AutoJack design may be considered resistant to compressive loads (vehicle).
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Isolated Powertrain Tests:
(1) Hydraulic Cylinder Power Test:
This test will ensure that the hydraulic cylinder and power unit are functioning properly and that they provide the necessary power to lift the 5000lb load. This test will be conducted in the hydraulic lab by assembling the complete hydraulic circuit outside of the frame, mounting the cylinder in a clamp jig, and pushing a 5000lb slab. Obviously, the cylinder must move the slab in order to be considered successful in this test.
(2) Hydraulic Cylinder Speed Test:
This test will ensure that the hydraulic cylinder and power unit are functioning properly and are capable of moving the applied load at a rate of 1in/s. This test will be conducted in the hydraulic lab by assembling the complete hydraulic circuit outside of the frame, mounting the cylinder in a clamp jig, and pushing a 5000lb slab. The cylinder must move the slab at a maximum rate of 1in/s (using a tape measure and stopwatch) in order to be considered successful in this test.
(3) Total Collapsed Height Test:
This test will ensure that the hydraulic cylinder is functioning properly and has the necessary stroke to fully collapse the AutoJack frame. This test will be conducted in the hydraulic lab by assembling the complete AutoJack and fully extending the cylinder. With the cylinder fully extended, the total height of the AutoJack must be 4 inches or under (measured with a tape measure) in order to be considered successful in this test.
(4) Total Expanded Height Test:
This test will ensure that the hydraulic cylinder is functioning properly and has the necessary stroke to fully expand the AutoJack frame. This test will be conducted in the hydraulic lab by assembling the complete AutoJack and fully extending the cylinder. With the cylinder fully retracted, the total height of the AutoJack must be 35 inches (measured with a tape measure) in order to be considered successful in this test.
(5) Cross Rod Deflection Testing:
This test will ensure that the theoretical calculated deflection of each cross rod is accurate to the real world data. This will ensure that the cross rods do not fail in sure, bending, or fracture during the lifting process. This test will be conducted in the Materials Labusing the Tenuis Olsen machine. Each cross rod will be mounted at its ends, simulating frame support. A 2500lb load will then be applied and the results will be measured and recorded in order to determine the cross rods deflection at max loading. The cross rods must deflect minimally or less than the theoretical values in order to be considered successful in this test.
(6) Total Powertrain Weight Test:
This test will ensure that the completed powertrain has remained under the maximum weight limit of 70lbs. This test will be conducted in the Materials Labusing a scale accurate to the nearest pound. The powertrain system will simply be placed on the scale and the weight reading will be recorded. Obviously, the powertrain system must weight less than 70lbs in order to be considered successful in this test.
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Photographs of the AutoJack frame accepting the Hydraulic Cylinder components:
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Test 1: “Hydraulic Speed Test – Loaded”
One of the biggest safety advantages that the AutoJack’s powertrain design offers over other conventional jacking methods is its smooth, steady, and fluid lifting operation. This characteristic has been achieved through the use of hydraulics and fluid power. The AutoJack’s hydraulic circuit is composed of several components, with the primary parts being the dual-acting cylinder and DC power unit. These components work together in order to transmit power through fluid and into linear motion. In order to minimize safety risks, this linear motion must occur at a steady and consistent rate. Therefore, it is critical that the hydraulic system operates as it was designed to.
To ensure that the system was operating at consistent speeds, a test was in order. The test consisted of mounting the hydraulic system in a device jig and running the circuit with various applied loads. Please see the “Test Plan” located in Engineering Report Appendix I for full documentation of this test. During evaluation, time (s) and distance (in) measurements were taken. Afterwards, these values could be used to calculate linear rate (in/s) values. This test will ensure that the cylinder and power unit are functioning correctly and are capable of meeting design requirement 3; moving the maximum applied load at a rate of 1in/s.
After Test 1 had been completed and average calculations had been made, the results could be analyzed. On average, the AutoJack’s hydraulic system was capable of traveling the 12in set distance in 2.76 seconds regardless of the applied load amount (tested 100lbs-500lbs). This means that the AutoJack’s powertrain transmits enough power to lift the load at 4.35 in/s on average. Compared to the lifting design requirement of 1 in/s minimum, the powertrain system has surpassed all relevant expectations and excelled in lift speed. Therefore, the AutoJack can be considered successful in Test 1: “Hydraulic Speed Test – Loaded.” The testing and evaluation phase of this device will continue as outlined in the project Engineering Report Gantt chart schedule located in APPENDIX E. Like the results from Test 1, future results will be appropriately documented with photographs and tabulated data and then added to APPENDIX G.
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Fig 2-1: Diagram/Setup of Powertrain System Test 1: "Hydraulic Speed Test – Loaded”:
Vid 1-1: AutoJack Powertrain + Frame Motion Pre-Check/Test:
Test 1: Testing Issues and Test Evolution
Testing Issues/Modifications:
One of the biggest advantages that the AutoJack’s design offers over other conventional jacking methods is its self-actuated hydraulic system. This system enables the AutoJack to have a consistent and steady lifting operation. Therefore, in order to maximize safety, it is absolutely critical that the hydraulic system operates as designed. To ensure that the system was operating at consistent speeds, a test was in order. The test consisted of mounting the hydraulic system in a device jig and running the circuit with various applied loads. During evaluation, time (s) and distance (in) measurements were taken. Afterwards, these values could be used to calculate linear rate (in/s) values.
There was one major issue when performing this test. Firstly, when providing power to the circuit, the cylinder-clamp jigs would come out of perpendicular alignment. This would cause the cylinder to extend out at an angle and travel farther than the pre set distance. Due to the additional traveling distance, each test trial required a greater time window. It is also important to note that the degree at which the jig setup would misalign itself was completely random. Therefore, each traveled distance was completely random and likewise, so was the measured elapsed times. Due to these reasons, this testing issue rendered the results inaccurate and invalid.
Methods used to resolve issues:
In order to resolve these testing issues, extra out-of-class time was allotted to the project and additional care was taken to correct and ensure testing success. For the cylinder misalignment issue, the clamp jigs and connecting clevis pins were disassembled and taken back to the machine shop for a boring/turning operation. Using the lathe, the jig holes were re-bored to accept a larger 1.0in diameter pin. Afterwards, the clevis pins were turned down to 0.975in diameter(s). The powertrain system was then reassembled with the fresh parts. These precisely machined parts allowed the jigs, pins, and cylinder to fit together much tighter. This eliminated all system wobble, and thereby eliminated the room for misalignment. Test 1 was then conducted properly. It was found that on average, the AutoJack’s powertrain transmits enough power to lift the load at 4.35in/s. This has surpassed all relevant expectations and minimum lift speed requirements. Therefore, Test 1 and the AutoJack itself can be considered successful.
Results
The AutoJack powertrain was successful in nearly all of its testing and evaluation. The device has met all of the pre-set design requirements, with the exception of one. During the “Hydraulic Cylinder Power Lift Test”, the powertrain was only capable of lifting 3900lbs, 1100llbs short of the 5000lb requirement set forth in DR1. This is due to the un-foreseen electrical, hydraulic, and mechanical efficiency losses. By performing calculations using the data gathered from Tests 1-6, it is estimated that the AutoJackhas an overall system efficiency of 78.0% with no load, 71.1% with a 2000lb load, and 59.5% with a 4000lbs load. Beyond that, the efficiency losses exceed what the powertrain can provide and the system stalls.
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Original AutoJack Design Requirements (DR1-6):
(1) The powertrain system must be capable of lifting a maximum-5000lb vehicle.
(2) The powertrain system must lift the vehicle at a minimum rate of 1.0 in/second.
(3) The powertrain system must translate a 31.0-inch minimum lift range.
(4) The powertrain locking gear must support a 5000lb load independently.
(5) The powertrain system, with fluid, must weigh less than 70lbs.
(6) The powertrain system must operate with less than 3.0 gallons of hydraulic fluid.
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Results from AutoJack Testing (Tests 1-6):
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(DR1) Failed – Powertrain system lifted 3900lbs (1100lbs under DR1)
(DR2) Success – Powertrain system lifted applied load at 4.35 in/s.
(DR3) Success – Powertrain system translated 34.5lift range.
(DR4) Success – Powertrain system lock gearsupported 7,320lbs.
(DR5) Success – Powertrain system weighed 66.7lbs.
(DR6) Success – Powertrain system operated on 1.5gallons of fluid.
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The AutoJack has met the parameters of a successful CWU MET senior capstone project. Firstly, there is a significant amount of engineering merit in the design and re-design (the iteration process) of the AutoJack. Secondly, there is a vast amount of critical problem solving, through force, pressure, shear stress, deflection analysis, static and dynamic considerations, and mechanical design. Thirdly, the cost and budgeting estimation of this project was realistic, and replicated that of a professional real-life situation. Fourthly, there is physical and numerical proof in the success of the AutoJack design, through engineering green sheets, engineering drawings, 3D models, data tables, graphs, photos, and videos. Fifth and finally, there has been a significant amount of teamwork and collaboration that made the project possible. Therefore, the AutoJack project can be deemed successful and is a genuine representative of the greater student accomplishment made at Central Washington University.
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Vid 6-2: AutoJack Final Lift Test Success:
Fig 6-7: AutoJack Final Lift Test Success:
