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The wind tunnel located on the Penn State University Park campus is used for analysis of aerodynamic forces and moments. This information is vital in the aerodynamic research and design of aircraft components. The results of this research aids in the development and efficiency of new aircraft. The current wind tunnel force balance, donated by Boeing and used in three dimensional testing, is in need of a new lifting mechanism which will operate over a range of 20 inches. This lifting mechanism, capable of lifting over 2300 lbs, should be controlled from the test station, and its height should be visible in the LabView interface. The existing wind tunnel balance, provided by Penn State Aerospace Engineering, consists of a heavy duty steel frame with a 45” by 90” footprint. The balance is moved out of the wind tunnel for calibration two or three times a year which means the lifting mechanism must be mobile. During this movement, low clearance in the wind tunnel means that the lifting mechanism must not raise the balance by more than 5” in its lowest position. Dynamic Consultants has undertaken the task of designing a viable solution to this problem. The chosen solution utilizes an automotive lifting mechanism which will be retrofitted to provide a stable lifting base. Casters will make the balance mobile. During testing, the casters will be lifted off of the floor, eliminating the chance of movement. Further, the system will be stabilized with vertical guide rails. Finally, this system will be controlled with a control box at the testing station, and its height will be monitored through LabView using an ultrasonic distance sensor. Due to time restraints and complexity of design, the lift mechanism could not be fully constructed in a single semester. As such, the final result of this project is a completed design for the construction of the balance lifting system, including a manual of all construction steps. The automotive lift tracks, the main component of the system, have already been purchased and delivered to the Penn State Aerospace Engineering Department, as have a number of smaller components.
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Thanks to a donation from Boeing Commercial Aircraft, the Penn State Aerospace Engineering Department has an aerodynamic force balance which measures those aerodynamic forces in three dimensions. The use of the balance, however, is currently limited by its lack of efficient mobility and difficulty of operation. Further, there is no easy way to lift the balance into its testing position or to control its height during a test. Finally, if the height of the balance were easily controllable, it would be beneficial if the operator were able to control it from the test bench.
The objectives for this project include designing a lifting mechanism for an aerodynamic force balance with certain specifications. The lift mechanism should be able to safely lift a load of 2300 lbs over a height range of 20 in. The system should be stable enough to withstand forces on the aerodynamic model, up to 200 lbs in any direction, without substantial movement. Further, the motion of the lift should be able to be controlled from the operator’s test area. The height should also be able to be monitored and read-in to a LabView interface.
To provide the lifting force, a two-track automotive lifting mechanism will be used. This lifting mechanism uses hydraulic actuators driven by an electric motor and has a 6,000 lb capacity. The two lift tracks will be connected to form one solid structure by welding three support bars between the track bases. With these support bars, the lift tracks will effectively become one solid lifting structure.
The aerodynamic force balance frame will have casters added so that it can be easily moved around the lab. During this time, the lift mechanism will be pinned to the frame, held off the floor so as not to impede motion. Once in testing position, the lift mechanism will be unpinned and lowered to the floor. As the lift raises, the casters will be lifted off of the floor along with the balance, so rolling during a test is not possible.
During the lifting process, the lift tracks move both horizontally and vertically due to their linkage design. To accommodate for the horizontal motion, the balance is connected to the lift tracks using four ball-bearing rails. These rails allow the lift tracks to move horizontally with respect to the balance. The balance is then stabilized by vertically oriented ball-bearing rails which are attached to a steel frame anchored to the floor. These vertical guide rails ensure that the balance will only move vertically, even while the lift tracks are moving both vertically and horizontally. Further, the vertical guide rails stabilize the system against aerodynamic forces transmitted through the balance.
The lift design is shown in the solid model below, which should greatly clarify the description above. Here, the aerodynamic force balance is shown predominantly in red while the automotive lift structure is shown primarily in blue.
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The main deliverable of this project is the manufacturing process plan, which is included as an appendix of the final report. This plan contains all of the information necessary for construction of the lifting system, including a bill of materials, tooling list, and step-by-step instructions. The process plan is accompanied by many pages of drawings and solid models, showing the locations of the parts mentioned in each step.
The manufacturing instructions are broken into six sections: lift preparation, lift modification, lift assembly, balance modification, vertical guide rail assembly, and final assembly. Following these instructions, the manual also provides instructions for operation of the system. In the final report, post-construction testing procedures are outlined.
This design must be tested throughout the construction process to confirm safe and effective operation within the design specifications that were given for the project. Therefore, a number of test procedures, performed both during construction and upon completion, are recommended to evaluate the performance of the design and alert the construction team should any problems arise.
The first stage of testing is simply connecting the automotive lift system to they hydraulic pump and confirming uniform lift motion; this test has already been completed. Once they lift tracks have been modified and rigidly connected, they should once again be tested to confirm uniform movement. If possible, a large load should be added at this time to ensure that the lifts are capable of lifting the balance, as they should be based on manufacturer specifications.
Once the entire lifting system has been assembled, the lifts should once again be tested for uniform motion. During this test, the motion of the balance along the horizontal tracks and vertical guide rails will also be tested. For safe operation, the balance must move along the tracks and rails without binding. Finally, in its highest vertical position, the balance should be subjected to 200 lb loads in various directions. If any of these loads results in significant balance movement, it indicates that the guide rails are not providing enough stability and that, most likely, the guide rail frame needs to be strengthened.
Finally, the system should be tested in a wind-tunnel test situation. Ideally, this test would involve a model which has already been tested. During the test, the balance will be subjected to real aerodynamic forces, and any movement in the lifting structure should be carefully monitored. At the conclusion of the test, test results should be compared with previous results for the same model to confirm accuracy.
Dynamic Consultants feels that the design of this lift mechanism meets all of the design specifications and will provide a good solution for the wind tunnel lab team. Penn State Aerospace Engineering can now complete the construction of the lifting mechanism and install it in the lab. Once installed, the balance will be much easier to move and to operate in the lab environment.
As a final note, Dynamic Consultants recommends the use of experienced fabricators in the construction of the lift. In some cases, particularly that of the horizontal and vertical ball-bearing rails, precision is important to ensure proper functionality. It is the sincere hope of Dynamic Consultants that this design will meet the needs of the wind tunnel lab and, in so doing, improve educational opportunities for the students of the Penn State Aerospace Engineering program.
