indiana university – purdue university fort wayne
TRANSCRIPT
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Indiana University – Purdue University Fort Wayne
Department of Engineering
ENGR 410 -- ENGR 411
Capstone Senior Design Project
Report # 2
Project Title: Test Stand for Calibrating Strain Gaged Drive Shafts
Team Members: Alex Yarian EE Joseph Carnes EE
Isaac Larson ME Curtis Coverstone ME Darin Taylor ME Aaquib Asif ME
Sponser: Eaton Corporation – Clutch Division
Faculty Advisors: Dr. C. Chen and Dr. Younis
Date: May 5, 2015
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Table of Contents Acknowledgements ........................................................................................................................4 Abstract ...........................................................................................................................................5
Section I: Problem Statement .......................................................................................................6 a.) Problem Statement .........................................................................................................7
b.) Requirements and Specifications ...................................................................................7
c.) Given Parameters ...........................................................................................................7
d.) Design Variables ............................................................................................................8
e.) Limitations and Constraints ...........................................................................................8
f.) Safety, Environment, Economic, and Other Considerations .........................................9
Section II: Design and Build of System .....................................................................................10 a.) Calibration Test Stand..................................................................................................11
1.) Frame ...............................................................................................................11 2.) Sliding Base .....................................................................................................11 3.) Design Changes of Frame and Related Components .......................................15
b.) Selection of the Ratchet ...............................................................................................17
c.) Epicyclic Gear Train Design: .......................................................................................18 1.) Original Gear Selection....................................................................................18
d.) Changes for Torque Multiplier ....................................................................................19
1.) Ring Gear .........................................................................................................19 2.) Input Shaft ........................................................................................................20
e.) Safety Guard Design ....................................................................................................22
1.) Safety Guard Loop Design ..............................................................................22
f.) Data Acquisition System Selection .............................................................................25 1.) Hardware and Wiring Setup ............................................................................27 2.) Torque Cell ......................................................................................................28
g.) User Interface ...............................................................................................................29
h.) Block Diagram .............................................................................................................30
i.) Costs .............................................................................................................................32
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Section III: Test Runs ..................................................................................................................35 a.) Data Collection ............................................................................................................36
b.) Method 1 ......................................................................................................................37
c.) Method 2 ......................................................................................................................38
d.) Method 3 ......................................................................................................................40
e.) Comparison of All the Methods ..................................................................................41
f.) Frame and Related Components Test Results .............................................................42
Section IV: Recommendations ....................................................................................................44 a.) Frame ...........................................................................................................................46
b.) Ratchet & Pawl ............................................................................................................47
c.) Safety Guard ................................................................................................................48
Conclusion ....................................................................................................................................49
References .....................................................................................................................................50
Appendices ....................................................................................................................................52 a.) Appendix A: Overall Torque Multiplier System .........................................................52
b.) Appendix B: Torque Multiplier Gears and Carrier ......................................................56
c.) Appendix C: Parts for Allowing Use of Drive Shaft ...................................................66
d.) Appendix D: Ratchet & Pawl ......................................................................................72
e.) Appendix E: Data from Tests ......................................................................................75
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Acknowledgements The team would like to thank Eaton Clutch Corporation for their support of this project and for sponsoring our senior design Capstone Project at IPFW.
In particular, the team thanks Andrew Temple and Jim Hurl from Eaton Labs in Auburn for all of their help, support, and for being the primary contacts for the project at Eaton. They have given hours of their own time answering questions as well as meeting with the team at Eaton.
Finally, the team would like to express their gratitude to Dr. C. Chen and Dr. Younis who are the advisers for the project and have spent many hours of their time guiding and helping the team.
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Abstract Eaton Clutch requested the design of a test stand for calibrating strain gauged drive shafts for its staff to use in their Auburn Lab to perform in-house calibration tasks. The lab currently uses drive shafts with strain gages applied to the surface to measure the output torque from the transmissions of large trucks. A relationship between the output voltage of the strain gages and the input torque to the drive shaft must be found by applying a known torque value to the drive shaft. This calibration is currently done outside of the lab at one of two facilities that are several hours away. By developing a new calibration fixture, the company will save many hours of technician time by eliminating the transportation time to and from facilities. Additionally, this stand will be a cost savings for the Auburn Lab, as the other facilities charge for use of their calibration fixtures.
The frame of the design is created with A500 steel tubing. It is made to be lagged to the floor to help reduce the amount of deflection of the frame. It also supports the system well, but there are some recommendations in report for the frame as well. A torque needs to be applied to a drive shaft is an objective the system needs to accomplish. This is done using a torque multiplier with a load cell. The torque applied value is held on the drive shaft using a ratchet and pawl. There is a data collection system used to collect, readout, and calculate data results the user is looking for from the system. This system was created by using a daq, Labview, Windaq, and laptop.
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Section I: Problem Statement
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Eaton Clutch requested the design of a test stand for calibrating strain gaged drive shafts for its staff to use in the Auburn lab to perform in-house calibration tasks. This stand should be able to apply a variable torque load to said drive shaft with the capability of handling torque inputs up to 3500 ft. lbs. The stand must be able to accommodate different size drive shafts with variable length and diameter, and it is preferable to accommodate different spline configurations. A simple to read/use interface for the test stand is requested. The integrated user interface must be able to display the applied torque in real time. The interface should also be able to produce ready-to-use calibration factors that can be inputted directly into the equipment that reads the strain gage. Requirements and Specifications The test stand needs to apply a known torque to obtain strain gage calibration values.
• Torque Applied- The variable should be anywhere from 0 ft. lbs. to 3500 ft. lbs. It needs to be applied, held, and safely released.
• Application Display- It needs easy to read calibration values, applied torque, and simple
input interface.
• Drive shaft Configuration- One requirement is that it accommodates Dana Spline Configuration.
• Measure of Applied Torque- An accurate measure of applied torque will be displayed on
the readout.
• Mechanical safety guards must be included to restrain a drive shaft in the event of failure
• If a powered/automated means of torque application be used, then an e-stop (emergency stop) must be located on the front of the equipment that disables all systems instantaneously.
• Method of measuring torque applied must be able to be calibrated.
Given Parameters The following fixed-design parameters will strictly govern a portion of the project.
● Drive shaft Dimensions- The dimensions are approximately 0 to 104 inches in length, and
3 to 6 inches in diameter.
● Stand-alone Unit- This must give calibration results without additional calculations,
input, or system related parts. It must also contain control systems and torque application
systems all-in-one.
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Design Variables The below variables allow for flexibility in the design of the project in order to meet the given requirements.
● Torque Application- Manual or automated (hydraulic, pneumatic, etc.)
● Drive shaft Connector- Accommodates different drive shaft spline configuration, along
with short-tool change/setup (10 to 15 minutes).
● Stand Construction- Different materials are allowed in construction.
● Test Stand Mobility- Portable or fixed unit, either is viable.
● Device output- range of means for output of test stand.
a.) The bare minimum is to read applied torque and voltage output of the strain gage.
b.) The desired system should be computer integrated with the Test Stand. It is one
that will accept a full range of applied torque vs voltage readout and calculates
usable calibration data. The system should also control the applied load if an
automated loading system is used.
● Torque measurement method- may be a torque cell or a load arm.
● Computer interface system- could use a variety of software and data acquisition devices.
National Instruments data acquisition system (NI-DAQ) is preferred; however, it is not
specified. LabView software is preferred but not specified.
● Multipoint Calibration- Software should accommodate multiple calibration points across
the entire applied load range to allow for accurate characterization of the strain gage(s)
and drive shaft system.
Limitations and Constraints The test stand must follow given constraints as well as budgetary limitations.
● Budget- The entire project must fall below the given budget of $7500.
● Test Stand Footprint- Space is limited, and stand should be as compact as allowable per
tested drive shaft. It must be able to fit reasonably within an Eaton test cell.
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Safety, Environmental, Economic, & Other Considerations Safety is of the utmost importance for every part of the project; additionally, ensuring that the project is environmentally friendly is also a key concern.
● Safety Cage- Safety system (e.g., safety collar or full cage) to account for drive shaft
failure.
● Emergency Fail Safe- Emergency stop that acts as a disconnect.
● Hydraulic System- Must have hydraulic spill containment plan (if said system is used).
● Safety Regulations- Test Stand must comply with all Eaton, OSHA, and other safety
regulations.
● Power Supply- The system should be 120 volts (standard outlet voltage).
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Section II: Design and Build of System
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Calibration Test Stand: Frame: The frame was modeled as one entire piece in SolidWorks due to the difficultly and inaccuracy involving welds within SolidWorks Simulation. Using the assembly model of the frame with the sliding base, the base was placed halfway between the end and the middle of the frame, where the deflection from a torque would be the highest. The feet of the frame were fixed, and a torque of 3500 ft-lbs was applied to the bolt holes in the sliding base. The resultant finite element analysis (FEA) shows that the maximum stress in the frame is equal to 16.3 ksi. The minimum yield strength of A500 steel is 33 ksi, so the minimum factor of safety of the frame is 𝐹𝐹 =33 𝑘𝑘𝑘 16.3 𝑘𝑘𝑘 ≈ 2⁄ . A diagram of the stresses found from the simulation is shown in Figure 9.
Figure 1: FEA simulation of torque on the Frame
Additionally, the highest stress at a weld joint is 9.5 ksi. For weld in tension or compression, the yield strength is multiplied by 0.6, so the minimum yield strength is 19.8 ksi for A500 steel. Therefore, the factor of safety at the weld joints is 𝐹𝐹 = 19.8 𝑘𝑘𝑘 9.5 𝑘𝑘𝑘⁄ ≈ 2. Sliding Base: The base was also modeling and simulated in SolidWorks using FEA. The bottom was fixed, and the bolt holes were subjected to the drive shaft torque. The bolt holes had the highest resultant stress, about 5.9 ksi. The highest stress in the rest of the base was about 3.5 ksi. This is shown in Figure 10.
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For A36 Steel, the yield strength is 36 ksi. With a maximum stress of 5.9 ksi, the resulting factor of safety is 𝐹𝐹 = 36 𝑘𝑘𝑘 5.9 𝑘𝑘𝑘 ≈ 6⁄ . Clamp: The clamps were also simulated with SolidWorks FEA. To determine the load to apply to the clamps, a moment balance was performed on the sliding base, shown in Figure 10. From the diagram, the resulting force was shown to be about 3000 lbf. This force was applied to both surfaces of the clamp bearing load in the structure, as shown in Figures 12 and 13. The resulting maximum stress is 18.9 ksi. With a yield strength of 36 ksi, the resulting factor of safety is about 1.9. From the moment diagram:
�𝑀 = 0 3500 − 10 ∙ 𝑅 ∙ (7.25 12⁄ ) = 0
(Reaction forces equal from symmetry) → 𝑅 = 3000 𝑙𝑙𝑙
Figure 2: Sliding Base FEA
Equation 1: Moment Balance
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Figure 3: Moment Diagram on Sliding Base
Figure 4: FEA of Clamp
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Figure 5: Back Side FEA of Clamp
Adapter: The adapter piece is required to make the connection between the load cell and the companion yoke of the drive shaft. This analysis of this piece included FEA as well as bolt shear analysis. From the FEA analysis, for A36 Steel (tensile strength of 58 ksi, and shear strength of 29 ksi), the shaft diameter necessary was found to be 3.10 inches, which resulted in a maximum stress of 16.3 ksi, and a resulting factor of safety of 1.8 (shown in Figure 6).
Figure 6: FEA Simulation of Adapter
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Design Changes of Frame and Related Components:
Frame construction remained mostly the same, but some of the components saw changes to the original design.
First, the Sliding Base and Adapter pieces both interface with the companion flanges, which is what the drive shaft is bolted to. These pieces originally had a 12 bolt pattern, but when we received the flanges, we found that they had an 8 bolt pattern. These pieces then had to be modified. Additionally, the flanges we received have a pilot diameter step machined onto them. Because of this, these pieces needed a pilot diameter step machined out of them.
Figure 7: These two images show the design changes of the frame.
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The Fixed Base Assembly also saw a few design changes. First, the original design called for a square hole to be machined in the base plate, and the block to be welded at 2 edges into the square hole. This design was changed due to the high cost of this assembly method. The fixed base is now bolted with two ½” bolts to its base plate. Also, the strength of this method was not necessary, as this block does not support any torque from the driveshaft. It merely is supporting the weight of the output shaft, load cell, and adapter pieces.
Additionally, the block originally had a stepped ID hole to press in a bearing to support the torque multiplier’s output shaft. This was changed to a single OD and a brass bushing. This was done both to reduce cost as well as to better support the bushing.
Lastly, the base plate that the fixed base was originally sitting on was a separate piece from the plate that the torque multiplier was sitting on. These plates were combined, both for assembly purposes and ease of machining. Additionally, this plate was moved 2 inches from the end of the frame, for assembly purposes.
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Selection of the Ratchet: As shown in Figure 8 below, the proper ratchet size was determined from the calculated 25 degree angular displacement of the sun gear. This was calculated from the torsional displacement of the driveshaft at the maximum loading condition. Since the sun gear only allows for an angular displacement of 25 degrees, this severely limits the choices of available ratchets. The ratchet sizes with the largest diametrical pitch allows for the largest amount of teeth to be triggered by the pawl within the 25 degree rotational displacement limit. The chosen ratchet and pawl would allow for up to eight “locks” from the ratchet and pawl system, while other ratchets with smaller diametrical pitches would allow for much fewer.
Figure 8: Ratchet Gear with Angular Displacement of Sun Gear shown
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Epicyclic Gear Train Design:
Figure 9: Epicyclic Gear Train Design
Original Gear Selection:
Figure 10: Gear Setup for 1st stage of the multiplier
Planetary
Ring
Sun
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Changes for Torque Multiplier: Ring Gear: Initial design
Figure 11: Two Piece Ring Gear This initial design of the ring gear(s) called for a twin ring gear setup, where each ring housed the spur gears. A gear carrier links both stages of the toque multiplier, necessitating a gap between the two ring gears. This gap could potentially cause alignment issues between the two stages, as well as being difficult to install and affect maintenance/repairs throughout the life of the test stand. Therefore, this design was changed to a one piece ring gear setup. Final Design
Figure 12: Single Piece Ring Gear The final design utilized a one piece ring gear design; this mitigates alignment issues between stages, allows the gear carrier to be housed within it, and makes maintenance and disassembly much easier for the operator.
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Input Shaft: Initial Design
Figure 13: Key Input The initial design called for two keys machined through the first stage sun gear (spur), this would necessitate an adapter piece to allow attachment of the torque application bar (ratchet wrench) to the spur gear for torque application. This design would allow for a failure point to be designed into the keys allowing for minimalized damage to the sun gear keyways. This design was modified however, due to the complex and custom adapter piece necessary. Final Design
Figure 14: Input Shaft
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Figure 15: Exploded View of Input shaft The final design of the input shaft utilized a custom piece that transfers input torque to the first stage sun gear through screws and shear pins which attach the input shaft to the sun gear.
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Safety Guard Design: The original design was a safety box figure 16. This design was flawed based on the shear mass of the top. This design was then modified by splitting the lid into 10 pieces, with 10 latches and 10 hinges so make the design functional. This design interfered with the sliding block and clamp so this design concept was no longer useable so a safety loop design was created.
Figure 16: Original design of safety box Safety Guard Loop Design: The safety guard design goes on to the frame and the drive shaft is to be run thru the safety guard. The safety guard has gussets for structural stability. Figure 17 shows the simulation if the driveshaft breaks and hits the top or the bottom. With the max stress being on the gussets of 1.121e+8 where the yield strength is 1.724e+8 that gives a factor of safety of 1.53. The sides extend past the frame and ½” bolts secure it on the frame, this can be seen in figure 18 and figure 19. The finished safety guard can be seen in figure 20.
Figure 17: Drop test results
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Figure 18: Design of the safety guard
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Figure 19: Mounting the safety guard on the frame
Figure 20: Safety guard on frame
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Data Acquisition System Selection:
The chosen DAQ model is the DATAQ Instruments Model DI-718B 8-channel USB Data Acquisition System (see Figure 21) we will be using two of the eight channels for strain gage measurements so 2 strain gage measurement modules must be purchased for it as well. The two modules that need to be included for the strain gage measurements are DI-8B38-05 Strain Gage-based Sensor (see Figure 22`).
We selected this device combination for several reasons. It has the correct bridge resistance range of 300 ohm to 2000 Ohm bridge resistance and the bridge that will be used in the design has a bridge resistance of 350 Ohm. This module has a 10.0 V excitation voltage for the bridge as well which is the level that was originally requested by Eaton so no additional voltage source will need to be added to the setup. It has an input range of +- 20 mV, which according to the example data provided, will be more than enough to accommodate the anticipated readout range. This device also provides 100 dB reduction to common mode noise which is essential to reading these very small voltage levels that are involved here. The device has 14 bit precision which when coupled with the given mV and torque range gives a precision of 0.00244 mV (see equation 2).
This device, although not produced by National Instruments, is still completely LabVIEW compatible. When both a LabVIEW Plugin (ActiveX) and the driver program for the device (Windaq) are installed and running then all of the data that is being streamed in by the DAQ can be read and manipulated by LabVIEW.
The DAQ also has a very high accuracy of ± 0.05% and a linearity of ± 0.02%. The device is a calibrated instrument; so, it can very accurately measure the torque being applied and the mV output from the bridge.
Equation 2: Precision in mV over the range of -20 to +20 mV using 14 bit precision.
𝑃𝑃𝑃𝑃𝑘𝑘𝑘𝑃𝑃 (𝑚𝑚) =20 − (−20)(𝑚𝑚)
214𝑏𝑏𝑏𝑏= 0.00244(𝑚𝑚)
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Figure 21: DI-718B Data Acquisition Unit for strain gage based measurements.
Figure 22: DI-8B38-05 amplification module that provides 10V excitation voltage as well as a very precise measurement range of +-20mV. This module also provides 100 dB reduction in common mode noise.
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Hardware and Wiring Setup:
Below in Figure 23 is a diagram of how all the components in the electrical system will be laid out. The strain gages on the drive shaft are connected in a full Wheatstone Bridge configuration as shown in Figure 24. There are two 4-wire busses connecting the strain gages to the DAQ and the Torque Cell to the DAQ. A USB cable then connects the DAQ to the computer. Each of the buses has four wires in it. Two of them are to apply a 10V excitation voltage to provide power to the bridge. The other two wires are to sense the output voltage of the bridge.
Figure 23: Hardware setup of the electrical system showing the wiring of the strain gages and the Torque cell to the DAQ and the DAQ being connected up to the computer.
Figure 24: Shown here is the Wheatstone Bridge configuration.
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Torque Cell:
The Torque Cell that was chosen was the TRS – 50K shown in Figure 25. We choose this cell as it is an accurate load cell with appropriate ratings for the application. It has a maximum measurement range of +-50,000 in-lbs which equates to +-4166.67 ft-lbs. It has a safe overload limit of 150% or 6250.0 ft-lbs giving us a safety factor of 2.08. It uses a 10V excitation voltage which is compatible with the Windaq DAQ. The range of the load cell and the 14 bit precision of the chosen DAQ give a precision of 0.51 ft-lbs which was obtained from Equation 3.
Equation 3: Precision in ft-lbs using the given parameters for the load cell and DAQ.
𝑃𝑃𝑃𝑃𝑘𝑘𝑘𝑃𝑃 (𝑙𝑓 − 𝑙𝑙𝑘) =20 − (−20)(𝑚𝑚)
214𝑏𝑏𝑏𝑏∗
4166.67 − (−4166.67)(𝑙𝑓 − 𝑙𝑙𝑘)20 − (−20)(𝑚𝑚)
= 0.51(𝑙𝑓 − 𝑙𝑙𝑘)
Figure 25: TRS-50K load cell for measuring the torque applied to the driveshaft.
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User Interface:
The user interface for the LabVIEW program for data acquisition is shown below in Figure 23. The primary requirement of the Interface was to provide real time readout of the torque applied in ft-lbs and the readout from the strain gages on the driveshaft in mVs.
Figure 26: User Interface for data acquisition LabVIEW program.
In the upper right hand corner of Figure 26 outlined in red is the real time display of applied torque and strain gage readout. These displays are the average of 20 individual measurements taken by the Daq and converted to a ft-lbs and mV readings respectively. These two readouts update every 0.5s with new data. As torque is applied to the driveshaft these gages track the changing data values quickly with no noticeable lag.
Below the real time gages in Figure 26 outlined in blue are another set of outputs derived from the real time gages. They provide additional averaging of 30X for a more accurate steady state reading of Torque Applied and Strain Gage readout. They are a moving average of 30 samples of the original average of 20 samples of raw data. This gives an effective average over 600 Samples for more accurate results. However, since the 20 sample average only updates every 0.5 seconds it takes 15 seconds to provide a correct reading of the current data after the system stabilizes as it takes that long for 30 samples to pass into the data buffer of the 30 sample averaging function. The third readout in this group is the Calibration factor in ft-Lbs/mV. It is a division of the heavily averaged Torque applied value by the heavily averaged Strain gage readout value. Provided the bridge and the load cell are properly zeroed, then, once the torque is applied and the
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system stabilizes at 3000 ft-lbs, the Calibration factor readout contains the correct characterization of mV out versus torque applied for the driveshaft.
In Figure 26 outlined in green are three controls that were developed for the design. On the far left is one that is an offset for the Strain gage bridge that can be used to enter a value in mV’s to zero it when no load is applied. In the center is another offset value for the Torque Cell that the user can input a value in ft-Lbs to in order to zero out the load cell when no load is applied.
On the Right of the screen in Figure 26 is a XY graph that plots the values from the real-time gages as they are read in. below the graph are two control buttons that can be used to clear the graph as well as to export the current data displayed on the graph to the clipboard. The operator can then save the data and perform additional processing on it if they desire.
Block Diagram:
The daq used was a DI-718B manufactured by Dataq Instruments. It has 8 channels that can be used to collect data. The program this daq is made to be used with is Windaq, but with ActiveX driver it can be used with LabView. This is first done by downloading the ActiveX driver download, so LabView can collect data from Windaq. Using the sequence component you can create a start, stop, and channel node for collecting the data (figure 27).
Figure 27: This is the sequence component with the start and channel nodes shown. One of the objectives of the program is to run continuously as the torque is applied to the drive shaft. The way this is done, is on the block diagram there is a while loop that contains all of other components running the program. This is so the program runs continuously when the run button of LabView is pressed; until the stop button is pressed the program will not stop. Another function of the program is to average 20 samples of data collected from the daq for the torque cell (ft.-lbs.) and strain gage (mV). This is done using a “for loop” inside of another “for loop” to create a 4 by 5 array of 20 samples (figure 28). These 20 samples are then split up individually by using the index array component (figure 29). The samples are then put together
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in a 20 by 1 array so they can sum together. This sum is then divided by 20 to get the average that is then displayed.
Figure 28: Shown above is the “for loop” inside another “for loop” to get the 20 sample array.
Figure 29: Shown above is the index array that gets the individually sample from the array and displays it.
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Costs: Frame and Related Components Cost Analysis:
The following table details the raw material costs for the components used to fabricate the frame, as well as the sliding and fixed bases of the frame. The labor associated with machining and fabricating these pieces was completed at GT Automation, which did not provide us with a detailed breakdown cost to manufacture each piece. Because of this, the labor costs associated with these pieces is detailed in the torque multiplier cost analysis.
Table 1: Shown here are the costs for the parts of the frame. Qty Product Total
1 HR Round 1018; 8" Ø x 12" $ 265.92
1 HR Flat; 3 x 4 x 12" $ 63.55
1 HR Plate; 12 x 12 x ¼" $ 8.92
1 Square Tube Steel; 2 x 2 x ¼", 64' $ 329.78
1 HR Flat; 12 x 24 x ¾" $ 67.87
1 HR Plate; 12 x 12-¾ x 3" $ 219.20
1 HR Plate; 12 x 12 x 2" $ 166.40
1 HR Angle Steel; 2 x 1-½ x 1⁄8" $ 4.67
1 Delivery $ 20.00
1 Taxes $ 119.38
Total
$ 1,265.69
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Costs of Safety Guard Parts and Labor: Table 2: Cost of Safety Guard
Cost of raw material
3 16X48" 111.83
Total 111.83
Cost of Hardware
Graphite Paint $ 7.48
Nuts&Bolts $ 4.84
Total $ 12.32
Cost of Manufacturing
Labor $627.00
Total $627.00
TOTAL COST OF SAFETY GUARD $751.15
Cost of Torque Multiplier: Table 3: Shown below is the cost of labor and material for the Torque Multiplier.
TORQUE MULTIPLIER COST ANALYSIS ACTIVITY MFG PRICE Shop Labor GT Automation $8,652
Purchased Pieces GT Automation/Tork Products/McMaster Carr $1,567
Wire EDM Subcontracted Work $2,757
TOTAL: $12,976
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Cost of Data Collection System: Table 4: This table shows the costs of the needed parts for the data collection system.
Overall Project Cost:
The budget given to us by Eaton in the first semester was $ 7,500. If you look at table 4 it shows the total cost of the project. This cost more than doubled the budget we were given for the project. Even with this being negative, there were positives to go with this such as a more reliable system. The biggest factor to the project exceeding the limit was the cost of labor.
Table 5: In the table below are shown the total costs of each system of the project and the overall cost also.
Total Cost of Project
Each System Cost ($)
Frame 1265.69
Safety Guard 628.54
Epicyclic Gearing and Ratchet & Pawl 12,976.00
Data Collection System 1127.75
Overall Cost 15,997.98
Component Cost ($) Quantity (#) Total Cost ($)Daq (DI-718B) 595.00 1 595.00Modules (DI-8B38-05) 127.00 2 254.00Laptop (HP 15-f039wm) 278.75 1 278.75Total Overall Cost 1127.75
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Section III: Test Runs
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Data Collection: The collection of data for the system is a big part, because that is how you know if the drive shaft is reacting to the torque applied correctly or not. This measurement calculated from the torque applied (ft.-lbs.) vs. strain gage (mV) readout is the calibration factor. First, the daq was tested with the two module cards in it for the load cell and strain gage to make sure it was working correctly. This was done by setting up a bridge similar to the strain gage bridge with the use of resistors, shown in figure 30, and taking measurements across the bridge with the daq and LabView.
Figure 30: The image above is of the strain gage bridge.
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Method 1: This is the method that Eaton uses at this time when they go to Galesburg, Michigan to run their tests on the drive shaft. The way this method is done is by applying torque in 500 (ft.-lb.) intervals from 0 to 3000, and recording the calibration readouts as you go up intervals. After recording data from the whole range (0 to 3000), excel is used to plot the data. The calibration factor is found from the slope of best fit line.
Figure 31: The image above shows the graph of data record by the user with the best fit line of this data.
y = 554.45x + 3.7778 R² = 1
0
500
1000
1500
2000
2500
3000
3500
0 1 2 3 4 5 6
Torq
ue A
pplie
d (ft
-lbs)
Strain Gage readout (mV)
Strain Gage Calibration Plot Run #4
Torque vs mV readout run#4Linear (Torque vs mV readout run#4)
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Method 2: In this method the user interface of LabView is used. On this interface there is a graph that plots torque applied vs. the strain gage readout (5m). The program does this every half a second, and in this method this is done while increasing the torque applied from 0 to 3000 (ft.-lbs.). When the user is done applying the range of applied torque they can export the data of the graph (figure #32) to excel by using the ‘export data’ button on the interface.
Figure 32: This is the graph of the data done in LabView. After exporting the data to excel a graph can be created of applied torque (ft.-lbs.) vs. strain gage readout (mV). On this excel graph a best fit line can be created with the slope of the line being the calibration factor (figure #33).
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Figure 33: Shown here is an excel graph of the data exported from LabView with a best fit line.
y = 553.72x + 6.1073 R² = 1
0
500
1000
1500
2000
2500
3000
3500
0 1 2 3 4 5 6
Torq
ue A
pplie
d (ft
-lbs)
Strain Gage readout (mV)
Strain Gage Calibration Plot Run #13 Torque vs mV readout run13
Linear (Torque vs mV readout run13)
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Method 3: Out of all three methods this one works the best. The user of the system applies a torque of 3000 (ft.-lbs.) to the drive shaft and let the system stabilize for 20 seconds. While this is taking place the user can make sure the torque applied and strain gage readout were both at 0 for their intercepts. After the system stabilizes the user interface has a readout for calibration factor that they can use (figure 34). Figure 34: This shows the user interface with the calibration factor readout.
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Comparison All of the Methods: Table 6: The table above shows the 8 tests ran for each method to get multiple calibration factors for each.
Method 1 had the largest total spread of calibration factors, which was a range of 4 (ft.-lbs.). This spread as a percent was .74 %, but for Eaton they allow for a 5 % range for the calibration factor data collected so all three methods would work for them. Also looking at the chart standard deviation is shown for each method and method 3 has the lowest value that is why it is the recommended way of doing the tests.
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Frame and Related Components Test Results:
There was one goal from the test plan that was directly related to the frame and components. This goal was that the frame deflection of the rails directly under the sliding base (where the torque is applied) be a maximum of 0.010.” Originally, the deflection was going to be measured with strain gages applied to the frame rails, however we realized that it would be much easier to measure the deflection with LVDT’s mounted directly beneath the frame rails.
The figures below show example LVDT data from the left and right frame rails, respectively. Unfortunately, the frame was not able to be lagged during testing, because Eaton does not know where they want to place it in their test lab yet. This, coupled with the fact that the frame simply was not rigid enough, lead to a much higher deflection than anticipated.
Figure 35: Shown here is a graph of the deflection of the Frame with torque applied decreasing over time.
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Figure 36: Shown here is a graph of the deflection of the Frame with torque applied increasing over time.
A plan to reinforce the frame has been developed, and will be detailed in the “Recommendations” section of the report.
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Section IV: Recommendations
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There are a few different recommendations for improving the system design. The way the strain gage calibration test stands works now, it accomplishes the task it was designed for, but there are a few changes with the frame, ratchet & pawl, and safety system that could improve the system. Frame:
The frame saw a significantly higher amount of deflection than anticipated. Because of this, a plan to add reinforcements to the frame has been developed. The original frame, as well as the reinforced frame, is shown below.
Figure 37: Original design
Figure 38: Reinforced frame
A new FEA was run using the same parameters as the original analysis on the new design. The original design showed a max deflection of about 0.0134”. The new design showed a significant reduction of deflection, to a max of about 0.0007”.
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The figures below show a comparison of the FEA results between the two designs.
The material cost of these additional supports, including shipping, comes to about $120. It is highly recommended to add these supports. The design modifications, coupled with lagging the
47
frame to the ground, will nearly eliminate the frame deflection that we saw during testing. A cost breakdown of the materials needed is shown below in the table.
Table 7: The table has cost of improvements.
Ratchet & Pawl: One improvement to the ratchet & pawl that would make the system safer when releasing the torque applied is by adding an extension lever to disengage the system. At this time the user has to use a screw driver to release the pawl, but this could be made safer by attaching some kind of lever. Another improvement to this part of the system is more machining to the input shaft bushing to allow for the face plate to not restrict the movement of the torque multiplier gears when the face is tightened up. Figure 39: Shown here is where to fillet the edges.
Fillet interferes with input bushing
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Safety Guard:
The safety guard fits tightly on the frame. It does not slide well at all. To move the safety guard along the frame, the safety guard had to be removed then transitioned to the desired location then put back on to the frame. Recommendation: apply graphite paint to reduce the friction easing the process of installing the safety guard on the frame. During the install both safety guards should be grouped together at one end of the frame so that the driveshaft can pass thru them at the same time, then transitioned to the operating position. The operating position the safety guard should be placed 1/3 of the drive shaft length apart.
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Conclusions: The project designed and built does the job of applying torque, 0 to 3000 (ft.-lbs.), to a drive shaft and collecting data from the tests. The system can actually apply more than 3000 (ft.-lbs.), it was measure up to a little over 3500 (ft.-lbs.). These measurements taken in and also calculated by LabView can give the user the calibration factor. This factor is graphed (strain gage readout vs. Torque Applied) on the user interface of LabView, to help the user know if the system is working correctly (close to a linear line) or not. The cost of the project was higher than the budget given to us by Eaton. Most of this is due to the cost of labor for different parts of the project. Also the ring gears had to be custom made instead of factory bought like we thought we could get. These higher costs contribute to make the system higher quality so it last longer. Overall the strain gage calibration test stand does the task it was designed with precision, giving the user accurate results.
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References
• Wheatstone Bridge – Last used on 2/20/15
http://www.electronics-tutorials.ws/blog/wheatstone-bridge.html • System Requirements for LabView Development Systems and Modules-
Last used on 3/21/15
http://www.ni.com/labview/requirements/ • Data Acquisition Using LabView- Last used on 4/5/15
http://www.dataq.com/blog/data-acquisition/programming/data-acquisition-using-labview-dataq-instruments-activex-controls/?print=pdf
• Metals Depot- Last used on 4/1/15
www.metalsdepot.com
• Fastener Fundamentals- Last used on 2/20/15 http://www.strengthandstiffness.com/4_basic/images/bearing_stress.gif
• McMASTER-CARR- Last used on 2/20/15
http://www.mcmaster.com/ • Mechanical Engineering Design, by Shigley, Nineth Editions
• AMERICAN GEAR MANUFACTERS ASSOCIATION, Revision of AGMA 226.1 • AMERICAN NATIONAL STANDARD—Fundamental Rating Factors and
Calculation Methods for Involute Spur and Helical Gear Teeth • KHK Gears – Last used on 2/13/15
http://www.khkgears.co.jp/world/break/SRT%20SRTB%20SRT-C.pdf
• Berg Precision Parts—Last used on 2/13/15
http://precisionparts.wmberg.com/gears/spurGears/en
• QTC Gears (prices)—Last used on 2/13/15 http://www.qtcgears.com/RFQ/default.asp?Page=../KHK/newgears/KHK316.html
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• Measurement Computing – Last used on 1/20/15
http://www.mccdaq.com/usb-data-acquisition/USB-3102.aspx
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Appendices:
Appendix A Overall Torque Multiplier System
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54
55
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Appendices:
Appendix B Torque Multiplier Gears and Carrier
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58
59
60
61
62
63
64
65
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Appendix C Parts for Allowing Use of Drive Shaft
67
68
69
70
71
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Appendix D Ratchet & Pawl
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Appendix E Data from Tests
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The table below is of method 1. There were 8 test runs ran with different operators going from about 0 to 3000 (ft.-lbs.). The applied torque and the strain gage readout values were recorder for the intervals of 500 (ft.-lbs.).
Run # User
1 Applied Torque (ft.-lbs.) -0.2 591 1085 1577 2038 2519 3008
Strain Gage Readout (mV) 0 1.06 1.95 2.86 3.69 4.55 5.42
2 Applied Torque (ft.-lbs.) -7 598 1017 1572 2040 2522 3015
Strain Gage Readout (mV) 0 1.067 1.845 2.85 3.7 4.53 5.41
3 Isaac Applied Torque (ft.-lbs.) -2.5 519 1037 1534 2015 2504 3009
Strain Gage Readout (mV) 0 0.925 1.85 2.765 3.64 4.515 5.405
4 Isaac Applied Torque (ft.-lbs.) 4.3 515 1033 1536 2012 2501 3008
Strain Gage Readout (mV) 0 0.92 1.845 2.77 3.64 4.51 5.402
5 Alex Applied Torque (ft.-lbs.) 4.8 514 1035 1535 2009 2499 3001
Strain Gage Readout (mV) 0 0.917 1.845 2.765 3.633 4.505 5.391
6 Isaac Applied Torque (ft.-lbs.) -1.2 499 1021 1528 2009 2496 3006
Strain Gage Readout (mV) 0 0.891 1.825 2.75 3.63 4.505 5.402
7 Isaac Applied Torque (ft.-lbs.) 1.8 509.5 1031 1534 2007 2496 3004
Strain Gage Readout (mV) 0 0.915 1.835 2.761 3.625 4.502 5.398
8 Curtis Applied Torque (ft.-lbs.) 2.1 500 1015 1532 2008 2496 3005
Strain Gage Readout (mV) 0 0.892 1.812 2.756 3.625 4.503 5.401
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Graphs 1-8: These graphs are runs of the table above with the y-axis torque applied and x-axis the readout of the strain gages (mV). Graph 1: Graph 2:
Graph 3: Graph 4:
y = 553.77x + 0.3715 R² = 1
-500
0
500
1000
1500
2000
2500
3000
3500
0 1 2 3 4 5 6
Man. Run1
y = 557.2x - 7.6972 R² = 0.9999
-500
0
500
1000
1500
2000
2500
3000
3500
0 1 2 3 4 5 6
Man. Run2
y = 555.19x + 1.6201 R² = 1
-500
0
500
1000
1500
2000
2500
3000
3500
0 1 2 3 4 5 6
Man. Run3
y = 554.45x + 3.7778 R² = 1
0
1000
2000
3000
4000
0 1 2 3 4 5 6
Man. Run 4
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Graph 5: Graph 6:
Graph 7: Graph 8:
y = 554.26x + 5.1284 R² = 1
0
500
1000
1500
2000
2500
3000
3500
0 1 2 3 4 5 6
Man. Run5
y = 554.72x + 3.3767 R² = 1
0500
100015002000250030003500
0 1 2 3 4 5 6
Man. Run6
y = 554.84x + 2.0357 R² = 1
-500
0
500
1000
1500
2000
2500
3000
3500
0 1 2 3 4 5 6
Man. Run7
y = 554.46x + 4.1966 R² = 1
0
500
1000
1500
2000
2500
3000
3500
0 1 2 3 4 5 6
Man. Run8
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Method 2: The table shown below is one of the test runs for a user. This was repeated 7 more times for this method. Run-6
Operator: Curtis Strain Gage Readout (mV) 0 0.1 0.3 0.4 0.6 0.7 0.9 1 1.1 1.3 1.4 1.6
Torque Applied (ft-lbs) 12.3 66.7 151.3 228.6 310.3 389.8 489 568.8 642 723.6 786 889.5 Strain Gage Readout (mV) 1.8 2.1 2.1 2.3 2.5 2.7 2.7 2.8 3 3.1 3.3 3.5 Torque Applied (ft-lbs) 1005.4 1152.4 1162.6 1267.1 1391 1483.8 1496 1570.6 1668.8 1752.4 1842.5 1938.3 Strain Gage Readout (mV) 3.7 3.8 4 4.1 4.2 4.3 4.5 4.6 4.7 4.7 4.8 4.8 Torque Applied (ft-lbs) 2032.9 2118.8 2199.5 2280.2 2343.8 2412 2496.5 2561.9 2605.5 2629.8 2645.6 2644.5 Strain Gage Readout (mV) 4.8 5 5 5.1 5.2 5.3 5.4 5.4 5.5 5.6
Torque Applied (ft-lbs) 2689.1 2753.1 2800.2 2853.9 2899.9 2951.3 2983.7 3013.4 3058.2 3103.8
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Graph 9: This graph is of the data collected in the above table.
y = 555.58x + 1.3701 R² = 0.9998
0
500
1000
1500
2000
2500
3000
3500
0 1 2 3 4 5 6
Run6
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Method 3: The table below is 1 of the test runs done using method 3, seven more tests where done this way.
run17 Isaac St. Gage
(mV) Tor. A.
(ft.-lbs.) St. Gage
(mV) Tor. A.
(ft.-lbs.) St. Gage
(mV) Tor. A.
(ft.-lbs.) St. Gage
(mV) Tor. A.
(ft.-lbs.) St. Gage
(mV) Tor. A.
(ft.-lbs.)
-0.006 1 0.87 481 2.274 1272 3.806 2119 4.945 2741 0.01 2 0.933 526 2.406 1344 3.899 2165 4.994 2766
0.011 6 1.01 566 2.493 1394 3.985 2214 5.016 2784 0.051 29 1.08 605 2.593 1446 4.083 2270 5.081 2817 0.061 31 1.148 643 2.728 1522 4.182 2321 5.127 2841 0.062 36 1.237 691 2.808 1568 4.249 2355 5.187 2879 0.085 48 1.31 728 2.909 1618 4.316 2396 5.22 2894 0.109 58 1.411 788 2.992 1673 4.389 2434 5.245 2904 0.141 79 1.513 845 3.099 1729 4.467 2475 5.286 2932
0.2 112 1.594 889 3.229 1795 4.547 2525 5.337 2958 0.285 156 1.678 938 3.305 1839 4.589 2546 5.378 2982 0.355 198 1.772 995 3.369 1880 4.646 2575 5.413 3003 0.432 244 1.879 1053 3.452 1914 4.696 2608
0.538 294 1.991 1112 3.539 1975 4.76 2642 0.639 359 2.086 1168 3.614 2009 4.838 2679 0.761 426 2.199 1230 3.706 2054 4.884 2710
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Graph 10: This data is plotted from the method 3 done in the table above.
y = 554.16x + 4.5674 R² = 1
0
500
1000
1500
2000
2500
3000
3500
-1 0 1 2 3 4 5 6
Run17