Overview of Status of Analysis, Design, Fabrication, Tests, etc.
Further and more complete strain gauge analysis and design has been done
Old hard drive tester has been tested and works, power source has been obtained and is being wired by Ray (the lab technician in CMRR)
Monday the fabrication of the ice dish was completed
Preliminary bending beam analysis with shim stock has been done
Preliminary static friction testing of Teflon on ice in a tray has been done
Accomplishments from Previous Week
Contacted more strain gauge companies including semiconductor strain gauge company (Vishay, (Daniel C., Bryan)
Completed machining of ice dish (Daniel C. Paulo Bryan)
Tested dish on hard drive tester (worked amazingly smoothly) (Bryan)
Preliminary coefficient of friction calculations of Teflon on ice (Daniel C)
Contacted capacitance gauge suppliers (Daniel W.)
Bending beam analysis tests on shim stock we ordered (Daniel W, Paulo)
Goals for Next Week (list names after each item). Use specific and measurable objectives.
Finalized strain gauge (Bryan)
Finalized beam design (Daniel W.)
CAD drawing of hard drive tester and strain gauge set up (Daniel C., Bryan)
Test smooth ice creation methods in the dish (Paulo)
Sponsor Comments from Last Meeting and Actions Taken to Address these Comments
Sponsor’s assistant was worried about the vibrations of the motor from the finalized design
Sponsor provided an old hard drive tester which features a smooth rotating turn table with a RPM reading mechanism.
Wants us to run deflection tests on beams (to compare to our calculations)
Ordered shim stock and ran a few deflection tests
Finalize design and pricing before we get any money
Further research on optimal strain gauges and practical deflection tests to prove our calculations
Sponsor would like the team to obtain free power source.
So far have found one power source for free and are in the process of locating another (5V should be easy to find)
Sponsor wanted a physical dish attachment
We have machined a dish and tested it on the hard drive tester and it worked very well.
Sponsor said the selected load cell was not sensitive enough for our application. Sponsor recommended using bending beam with strain gauges
Actively researching strain gauge and beam combination suitable for this project also looked at alternative methods
Instructor Comments from Last Meeting and Actions Taken to Address these Comments
Compare strain calculated from beam bending spreadsheet to max range of strain that strain gauge is meant to work in
Semiconductor strain gauge manufacturer said that ideal strain is around 500 microstrain, but will work for lower strains as long as we are able to read small voltages (The engineers estimates was a 20mV reading for 50 microstrain).
To get maximum signal choose beam so the strain you get is just less than the operating range of the strain gauge
To reach the ideal strain for the strain gauge, the beam would either have to be much smaller than our already generously small dimensions or our applied force would have to be increased by a magnitude of 10.
Can you mount semiconductor strain gauges yourself, or could you have the company?
A representative said that they offer “backed” strain gauges, which can be peeled off a clear plastic tape and be installed easily. They also said that they offer installation for a price depending on the complexity of the installation.
How will you calibrate the strain beam?
The strain beam will best be calibrated by doing a static test. We will be looking into using gravity and very light masses to determine the true gauge factor. The gauge factor is given from the manufacturers with a tolerance, so we will need to determine where our gauges lie within that tolerance.
How flat will ice be? Could you test the device with something flat such as a hard disk?
Ideally, the ice would be perfectly level. We are going to have to try a couple of our ideas to see how flat we can get it. During our preliminary test, the tray of ice that was made was not very level due to the top layer freezing first, then bursting due to the water freezing and expanding underneath.
To protect delicate beam, create hard stops.
This is probably what we are going to end up doing, because it is easy and dependable.
Look into capacitance sensors
Although they would work very nicely, these are probably out of budget for our project as they cost around $1500. We did find some that were cheaper, but would not work for the measurement we are looking for.
Peer Comments
Maybe look into thermistors for temp – Allen Tan
These look like they will be a very cheap and easy way to measure the temperature. We will most likely be pursuing this.
Will ice melt before test is done? – Jonathan Thinh
Since the tester is in a temperature enclosed area, we are assuming that the temperature of air will keep the ice frozen as friction probably won’t play too large of a role in the melting of the ice.
How long does each test last? – Brian Miller
Each test will last long enough to get an accurate reading of the strain in the beam. We are not exactly sure how quickly it will take the machine to get up to speed with the dish full of ice on it, but we hope to get a better idea as we progress through this project.
Do you have to account for different qualities of snow/ice? – Brian Miller
Initially we were going to try to use snow, but snow might be too difficult to mimic and work with for this project. We can use different kinds of ice by freezing different kinds of water.
Will hardware be effected by temperature environment? – Jonathan Thinh
The strain gauges are able to withstand temperatures down to -85C, which is much lower than the range that we are looking for.
What speeds do you get out of 1800/2700/3600 RPM? – Vincent Sherman
11.3/17.0/22.6 m/s (40.68/81.36/122.04 km/hr) with a 6 cm radius.
How much accuracy does the sponsor want? – Alex Zhernachuk
From our understanding, they would like it to be fairly accurate and able to be distinguishable between low strains in order to compare similar materials.
Will the HD tester withstand the temp range? – Alex Zhernachuk
The motor that spins the dish is fairly insulated by the top of the hard drive tester. We can also open the frame of the hard drive tester to increase air flow that would cause the motor to heat up the temperature enclosed environment.
Gel vibration dampening – Alex Zhernachuk
If we see that the hard drive tester is causing a lot of vibrations that would have an effect on the measurements, this would probably be a good way to reduce this noise.
Use of fulcrum to amplify frictional force? – James S.
This was an idea that Jorge proposed a while back that we weren't sure would work. We thought that friction in the bearing might cause an inaccurate reading, but this is something we are looking further into.
Risks and Areas of Concern
Selecting a strain gauge and beam combination to get the most accurate reading for friction
Possible vibrations with the thin shim stock beam
Ice not being very smooth
Resources or Information Required but not Available
We would like to use a large freezer to test the hard drive tester which was provided. We have no knowledge about the tester because it is so old and would like to see its performance at low temperatures
Schedule
Purchase strain gauge by Wednesday 2/8 (Bryan, Daniel W.)
Complete smooth ice creation methods 2/2 - 2/7 (Paulo)
CAD drawing of actual hard drive tester w/dimensions 2/6 (Daniel C, Bryan)
Finalized beam type and size Wednesday 2/8
Brainstorm modification idea of the Hard Drive Tester (All)
Implement individual test data into report form (All)
Budget (list amount spent and amount remaining)
$20 – Shim stock
Waiting for Professor Talke’s approval of strain gauge expected $60 - $120
Progress on Report and Webpage
Webpage has all individual component reports
Webpage has weekly progress reports
CAD drawing on front page
Report – keeping data and pictures of our preliminary tests for use in the report