Difference between revisions of "Team:DTU-Denmark/Hardware"
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| − | <p style="text-align:justify;">An important part of this project was for us to be able to characterize the material properties of the fungus. | + | <p style="text-align:justify;">An important part of this project was for us to be able to characterize the material properties of the fungus. Despite having specialized equipment at our disposal, for this purpose of future prospecting teams, we wanted to create an alternative, cost-efficient way of making measurements, that would be independent of expensive machinery. We built a hydraulic press for us to perform compressive and tensile strength tests. These kinds of tests are needed in order to determine the stiffness of the material, which is an important factor for evaluating the viability of a building material.<br> |
| − | This page will give a brief introduction to mechanical testing and the physics behind it, building instructions of the hydraulic press, characterization and discussion of the press’s abilities. | + | This page will give a brief introduction to mechanical testing and the physics behind it, building instructions of the hydraulic press, characterization, and discussion of the press’s abilities. |
</p> | </p> | ||
| − | <p style="text-align:center;"><a href="#buildinginstruk"><img src="https://static.igem.org/mediawiki/2018/b/b4/T--DTU-Denmark--hardwaregif.gif" style="width: 80%;"></a><figcaption><p style="text-align:center; font-size:14px;">Click <a href="https://www.youtube.com/watch?v=itpHre49MBk" target="_blank">here</a> | + | <p style="text-align:center;"><a href="#buildinginstruk"><img src="https://static.igem.org/mediawiki/2018/b/b4/T--DTU-Denmark--hardwaregif.gif" style="width: 80%;"></a><figcaption><p style="text-align:center; font-size:14px;"><b>Fig. 1:</b>Click the image for a detailed description, or, for a fun video of the fabricating process, click <a href="https://www.youtube.com/watch?v=itpHre49MBk" target="_blank">here</a></p></figcaption> |
</p> | </p> | ||
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| − | <div class=" | + | <div class="verticalLineright textbreather interlabspace verticalrightelem"> |
| − | + | <h2 class="media-heading" style="text-align: right;margin-bottom: 35px; color:#F8A05B;">Material characterization</h2> | |
| − | <h2 class="media-heading" style="text-align: | + | |
<div class="textwrap interlabspace"> | <div class="textwrap interlabspace"> | ||
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| − | <p style="text-align:justify" >When wanting to determine material characteristics, one way to do it | + | <p style="text-align:justify" > |
| + | When wanting to determine material characteristics, one way to do it is to perform destructive tests. These tests enable us to accurately predict how a material will act when under load. An important parameter is Young's Modulus. It predicts how much a material sample extends under tension or shortens under compression. The Young's modulus directly applies to cases of uniaxial stress, that is tensile or compressive stress in one direction and no stress in the other directions. It is a measure of how stiff/rigid a material is in its linear region. When a material is experiencing stresses, in its linear region, it will return to its original shape when the stress is removed (elastic deformation). Outside of the linear region, in the non-linear region, the material will undergo permanent deformation until catastrophic failure. (1)<br><br> | ||
Young’s modulus is defined as: | Young’s modulus is defined as: | ||
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\end{equation} | \end{equation} | ||
| − | E is the Young's modulus (modulus of elasticity) [Pa or N/$m^{2 | + | <ul> |
| − | F is the force exerted on an object under tension< | + | <li>E is the Young's modulus (modulus of elasticity) [Pa or N/$\textrm{m}^{2}$]</li> |
| − | A is the actual cross-sectional area, which equals the area of the cross-section perpendicular to the applied force | + | <li>F is the force exerted on an object under tension</li> |
| − | $\Delta L$ is the amount by which the length of the object changes ( $\Delta L$ is positive if the material is stretched , and negative when the material is compressed)< | + | <li>A is the actual cross-sectional area, which equals the area of the cross-section perpendicular to the applied force</li> |
| − | + | <li>$\Delta L$ is the amount by which the length of the object changes ( $\Delta L$ is positive if the material is stretched, and negative when the material is compressed)</li> | |
| − | < | + | <li>$L_{0}$ is the original length of the object</li> |
| − | During our testing we measured compressive strength. To get a more complete picture of the material properties of our fungi, | + | </ul> |
| + | <p style="text-align:justify" > | ||
| + | During our testing, we measured compressive strength. To get a more complete picture of the material properties of our fungi, we would need to also perform tensile strength tests. | ||
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</div> | </div> | ||
| − | <div class=" | + | |
| − | <h2 class="media-heading" | + | |
| − | </h2> | + | <div class="verticalLine textbreather interlabspace verticalleftdarkblue"> |
| + | |||
| + | <h2 class="media-heading" style="text-align: left;margin-bottom: 35px; color:#001D43;">Building Instructions</h2> | ||
| + | |||
| + | |||
| + | |||
<div class="textwrap"> | <div class="textwrap"> | ||
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<h3>Bill of materials</h3> | <h3>Bill of materials</h3> | ||
| − | <p style="text-align:center;"><img src="https://static.igem.org/mediawiki/2018/2/21/T--DTU-Denmark--hardware1.png" style="width: 100%;"> | + | <p style="text-align:center;"><img src="https://static.igem.org/mediawiki/2018/2/21/T--DTU-Denmark--hardware1.png" style="width: 100%;"><figcaption><p style="text-align:center; font-size:14px;"><b>Fig. 2: </b>All the materials needed to build the cheap hydraulic press.</p></figcaption> |
</p> | </p> | ||
</p> | </p> | ||
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<li>Hex nuts (8)</li> | <li>Hex nuts (8)</li> | ||
<li>Washers (8)</li> | <li>Washers (8)</li> | ||
| − | </ol> | + | </ol><br> |
| − | Here is a fun video demonstrating the <a href="https://www.youtube.com/watch?v=itpHre49MBk" target="_blank">fabrication process</a> | + | Here is a fun video demonstrating the <a href="https://www.youtube.com/watch?v=itpHre49MBk" target="_blank">fabrication process</a> |
| − | <p style="text-align:center;"><img src="https://static.igem.org/mediawiki/2018/4/41/T--DTU-Denmark--hardware2.png" style="width: 100%;"> | + | <p style="text-align:center;"><img src="https://static.igem.org/mediawiki/2018/4/41/T--DTU-Denmark--hardware2.png" style="width: 100%;"><figcaption><p style="text-align:center; font-size:14px;"><b>Fig. 3: </b> Illustration covering each step of fabcricating the frame. </p></figcaption> |
</p> | </p> | ||
</p> | </p> | ||
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<h3>Fabrication steps</h3> | <h3>Fabrication steps</h3> | ||
| − | <p style="text-align:justify"><span style="color: #ff0000"><b>Caution</b></span>: When working with metal, be very careful of your environment and work piece. You cannot see/feel if metal is scorching warm before | + | <p style="text-align:justify"><span style="color: #ff0000"><b>Caution</b></span>: When working with metal, be very careful of your environment and work piece. You cannot see/feel if metal is scorching warm before it is too late, and you get 2nd degree burn on your fingers. The machinery is spinning very fast, and has <b>A LOT</b> of torque. It wont stop or even slow down if your hair or sleeves get caught. Wear protective eyewear. After every cut in metal, make sure to <b>deburr ALL edges</b>. The metal is razor sharp after a cut/drill. |
| − | Frame: [Square tube, threaded rod, 8 hex-nuts, 8 washers] | + | |
| − | <ol> | + | |
| + | <h5>Frame: [Square tube, threaded rod, 8 hex-nuts, 8 washers]</h5> | ||
| + | <p style="text-align:justify;"><ol> | ||
<li> Cut a 30 cm long piece of square tubing. </li> | <li> Cut a 30 cm long piece of square tubing. </li> | ||
<li> Cut your piece in half, lengthwise. You now have the top and bottom of the frame. </li> | <li> Cut your piece in half, lengthwise. You now have the top and bottom of the frame. </li> | ||
<ol> | <ol> | ||
| − | <li> If you are not able to use a saw for this step, a grinder with a cut-wheel will work. However; if you do this, | + | <li> If you are not able to use a saw for this step, a grinder with a cut-wheel will work. However; if you do this, you will need to mill the edges in order to make them square. </li> </ol> |
| − | <li> Measure out where | + | <li> Measure out where you will have to drill holes. The edge of the drilled hole should be 2.5 cm from any edge. Use one tap with a center-punch. </li> |
<li> Drill the holes. The holes should be drilled in steps in order to not destroy the drill. Start with 4mm → 6mm → 8 → 10mm. </li> | <li> Drill the holes. The holes should be drilled in steps in order to not destroy the drill. Start with 4mm → 6mm → 8 → 10mm. </li> | ||
<li> Cut two, 30 cm long pieces from a threaded rod. Ø10mm </li> | <li> Cut two, 30 cm long pieces from a threaded rod. Ø10mm </li> | ||
| − | <li> Assemble according to the schematic. </li> </ol> | + | <li> Assemble according to the schematic on fig. 3. </li> </ol> |
</p> | </p> | ||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | <ol> | + | <h5>Car jack: [Car jack, pressure gauge]</h5> |
| + | <p style="text-align:justify;"> | ||
| + | This step will depend heavily on which car jack you acquire. We bought a car jack without a pressure gauge. If you buy a jack with a pressure gauge, disregard this part of the instructions. I will explain how to hack the car jack in general terms, and how to determine which pressure gauge to buy.<br> | ||
| + | |||
| + | <p style="text-align:justify;"><ol> | ||
<li> Completely disassemble the car jack, everything, even the ball valves. </li> | <li> Completely disassemble the car jack, everything, even the ball valves. </li> | ||
<ol> | <ol> | ||
| − | <li>There will be some hydraulic oil; save it. Note how you disassemble it, | + | <li>There will be some hydraulic oil; save it. Note how you disassemble it, you will have to assemble it again later.</li> |
</ol> | </ol> | ||
| − | <li>Measure the diameter at the widest part of the innermost main piston (inside the red square on the | + | <li>Measure the diameter at the widest part of the innermost main piston (inside the red square on the fig. 4). </li> |
<ol> | <ol> | ||
<li> This is the point at which the piston is experiencing hydraulic force. You need this area to determine which pressure gauge to buy.</li> </ol> | <li> This is the point at which the piston is experiencing hydraulic force. You need this area to determine which pressure gauge to buy.</li> </ol> | ||
| − | <li> Measure where to drill (Ø1mm) an L-shaped channel in the base of the jack. This means that | + | <li> Measure where to drill (Ø1mm) an L-shaped channel in the base of the jack. This means that you will have to make 2 plunges that meet inside the base of the car jack. </li> |
<ol> | <ol> | ||
| − | <li> This step might be a bit tricky. Just be sure to make straight plunges with the drill-press and not to drill all the way through. Make well measured and well considered plunges. Look at | + | <li> This step might be a bit tricky. Just be sure to make straight plunges with the drill-press and not to drill all the way through. Make well measured and well considered plunges. Look at fig. 5. </li> </ol> |
<li> Enlarge the outer hole to be able to accommodate the threads of your pressure gauge. </li> | <li> Enlarge the outer hole to be able to accommodate the threads of your pressure gauge. </li> | ||
<li> Tap the enlarged hole with the appropriate thread pitch. </li> | <li> Tap the enlarged hole with the appropriate thread pitch. </li> | ||
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<li> Assemble the hydraulic press, fill it with the hydraulic oil. </li> | <li> Assemble the hydraulic press, fill it with the hydraulic oil. </li> | ||
</ol> | </ol> | ||
| − | + | <p style="text-align:center;"><img src="https://static.igem.org/mediawiki/2018/8/8e/T--DTU-Denmark--DisPump.png" style="width: 100%;"><figcaption><p style="text-align:center; font-size:14px;"><b>Fig. 4: </b>Picture of a completely disassembled car jack.</p></figcaption> | |
| − | <p style="text-align:center;"><img src="https://static.igem.org/mediawiki/2018/2/27/T--DTU-Denmark--hardware5.png" style="width: 100%;"> | + | </p> |
| + | <p style="text-align:center;"><img src="https://static.igem.org/mediawiki/2018/2/27/T--DTU-Denmark--hardware5.png" style="width: 100%;"><figcaption><p style="text-align:center; font-size:14px;"><b>Fig. 5: </b>A 3D view of the L-shaped channel, that needs to be drilled.</p></figcaption> | ||
</p> | </p> | ||
<h3>Deciding on an appropriate pressure gauge</h3> | <h3>Deciding on an appropriate pressure gauge</h3> | ||
<p style="text-align:justify"> | <p style="text-align:justify"> | ||
| − | In order to determine what pressure gauge to buy/order, | + | In order to determine what pressure gauge to buy/order, you will need to do some calculations and measurements. Not to worry, it will be easy. |
| − | + | I will use our car jack as an example. we used these youtube videos as references: <br> | |
| + | <a target="_blank" href="https://bit.ly/2mLPkqz">Video 1</a><br> | ||
| + | <a target="_blank" href="https://bit.ly/2LuJjNE">Video 2</a> <br><br> | ||
| − | + | You will need to know the area of the innermost piston in order to calculate the maximum pressure the gauge will need to be able to withstand. The formula is as follows: | |
\begin{equation} | \begin{equation} | ||
| − | \frac{\textrm{Maximum lifting capacity of the jack}}{\textrm{ | + | \frac{\textrm{Maximum lifting capacity of the jack}}{\textrm{Area of the innermost piston}} |
\end{equation} | \end{equation} | ||
The car jack our team bought had a maximum press capacity of 2000 kg (4409.25 lbs). | The car jack our team bought had a maximum press capacity of 2000 kg (4409.25 lbs). | ||
| Line 170: | Line 179: | ||
\begin{equation} | \begin{equation} | ||
| − | \frac{\textrm{Maximum lifting capacity of the jack}}{\textrm{ | + | \frac{\textrm{Maximum lifting capacity of the jack}}{\textrm{Area of the innermost piston}}=\frac{4409.25 \textrm{lbs}}{0.70 \textrm{in}^2}=6288.1 \textrm{psi} |
\end{equation} | \end{equation} | ||
| − | Now you know that your pressure gauge will need to be able to go to 6300 | + | Now you know that your pressure gauge will need to be able to go to 6300 psi. Buy a pressure gauge with its maximum pressure rating as close to 6300 as possible, while making sure that the dial has a high resolution.<br> |
| − | We opted to buy a pressure gauge that could go to 3626 | + | We opted to buy a pressure gauge that could go to 3626 psi. This means that our maximum pressing capacity is lower, but the minimum resolution is higher since the dial has more digits. <br> |
| − | To determine the resolution of the hydraulic press | + | To determine the resolution of the hydraulic press we will need to multiply the minimum dial feature/step with the area factor: 1 bar (14.50 psi). Multiply this with the area of the piston 0.7. |
\begin{equation} | \begin{equation} | ||
| − | 14.50 | + | 14.50 \cdot 0.7 = 10.150 lbs |
\end{equation} | \end{equation} | ||
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| − | |||
| − | <h2 class="media-heading" style="text-align: | + | |
| + | <div class="verticalLineright textbreather interlabspace verticalrightelem"> | ||
| + | <h2 class="media-heading" style="text-align: right;margin-bottom: 35px; color:#F8A05B;">Characterization of the hydraulic press</h2> | ||
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<p style="text-align:justify" > | <p style="text-align:justify" > | ||
| − | In order to verify the hydraulic presses real accuracy, we tried to characterize it using a normal bathroom scale. This is not optimal | + | In order to verify the hydraulic presses real accuracy, we tried to characterize it using a normal bathroom scale. This is not optimal since we are only able to verify the very bottom of the range of the press (0-100 kg). The press goes to 1150kg. In theory, the press should be able to press with 4.60 kg/bar. This was verified. At higher pressures, the hydraulic press seemed to lose some of its power. This most likely stems from air bubbles on the inside of the pressure chamber. We were offered to have it certified with a calibration load-cell through its whole range but were not able to make it in time before the deadline. |
</p> | </p> | ||
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| − | <div class=" | + | <div class="verticalLine textbreather interlabspace verticalleftdarkblue"> |
| − | <h2 class="media-heading" | + | |
| + | <h2 class="media-heading" style="text-align: left;margin-bottom: 35px; color:#001D43;">Limitations | ||
</h2> | </h2> | ||
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<p style="text-align:justify" > | <p style="text-align:justify" > | ||
| − | The machine we used to characterize our fungi with was the Instron 6022. Its maximum load capacity is 10,000 newton, or 1 ton. Its smallest step size is approximately 0.5 $\%$ of its maximum load capacity, which is 50 newton. This load, on our test samples, results in a pressure of 0.8 bar, because the area of the sample is 6.25 $cm^{2}$ | + | The machine we used to characterize our fungi with was the Instron 6022. Its maximum load capacity is 10,000 newton, or 1 ton. Its smallest step size is approximately 0.5 $\%$ of its maximum load capacity, which is 50 newton (2). This load, on our test samples, results in a pressure of 0.8 bar, because the area of the sample is 6.25 $cm^{2}$ |
\begin{equation} | \begin{equation} | ||
10,000N \cdot\ 0.5 \% =50N\\ | 10,000N \cdot\ 0.5 \% =50N\\ | ||
| Line 231: | Line 242: | ||
| − | 5.10 kg is the smallest resolvable load the machine can perform. Under this value, there is simply too much noise in the signal. Our homemade hydraulic press had a resolution of 4.60 kg. Our \$50 hydraulic press has a finer resolution than a \$93.000 machine.<br><br> | + | 5.10 kg is the smallest resolvable load the machine can perform. Under this value, there is simply too much noise in the signal. Our homemade hydraulic press had a resolution of 4.60 kg. Our \$ 50 hydraulic press has a finer resolution than a \$ 93.000 machine.<br><br> |
| − | This all sounds very nice, but there are some major caveats though. The homemade hydraulic can only be used to test the yield strength of any given material | + | This all sounds very nice, but there are some major caveats though. The homemade hydraulic can only be used to test the yield strength of any given material that will likely break before 1150 kg. This is done by closely observing the pressure gauge and looking for when the pressure drops on the gauge. You will usually also be able to hear when the yield strength has been surpassed. This is not the case for foam-materials though, because these do not have a defined “drop-off” in their compressional strain/stress curve. This is a limiting factor since we cannot record the continuous deformation/strain of the materials. We are essentially only able to “maybe” determine a yield point, using the hydraulic press. The Instron 6022 is able to electrically and continuously record the materials’ response to stresses, which makes it the more suitable machine in the end. What makes these machines expensive is their certification and calibration, making them very accurate throughout the entire range of the load-cell. |
| − | The Instron 6022 is able to electrically and continuously record the | + | |
| + | |||
| + | </p> | ||
| + | |||
| + | |||
| + | </div> | ||
| + | |||
| + | |||
| + | |||
| + | <div class="verticalLineright textbreather interlabspace verticalrightelem"> | ||
| + | <h2 class="media-heading" style="text-align: right;margin-bottom: 35px; color:#F8A05B;">Results</h2> | ||
| + | |||
| + | |||
| + | |||
| + | |||
| + | <p style="text-align:justify" > | ||
| + | |||
| + | After having characterized the hydraulic press it was used to perform the very first of our compressional strength tests. As it is apparent from the table below, high drying temperatures are favorable, since it resulted in a higher yield point of our fungus. | ||
| + | |||
| + | <p style="text-align:center;"><img src="https://static.igem.org/mediawiki/2018/6/63/T--DTU-Denmark--FungusResults.png" style="width:90%;"><figcaption><p style="text-align:center; font-size:14px;"><b>Table 1:</b> Table showing the very first test results using the cheap hydraulic press. </p></figcaption> | ||
| + | </p> | ||
</p> | </p> | ||
| Line 251: | Line 281: | ||
| − | <p style="color:#000; font-size:14px;"></p> | + | <p style="color:#000; font-size:14px;">(1) Roylance D. 2008. Mechanical properties of materials. Retrieved <a target=”_blank” href=http://web.mit.edu/course/3/3.225/book.pdf>here</a>. <br><br> |
| + | |||
| + | |||
| + | |||
| + | (2) Interview with prof. Christian Berggren, DTU institute of mechanical technology | ||
| + | </p> | ||
</div> | </div> | ||
</div> | </div> | ||
Latest revision as of 03:20, 18 October 2018
Hardware
An important part of this project was for us to be able to characterize the material properties of the fungus. Despite having specialized equipment at our disposal, for this purpose of future prospecting teams, we wanted to create an alternative, cost-efficient way of making measurements, that would be independent of expensive machinery. We built a hydraulic press for us to perform compressive and tensile strength tests. These kinds of tests are needed in order to determine the stiffness of the material, which is an important factor for evaluating the viability of a building material.
This page will give a brief introduction to mechanical testing and the physics behind it, building instructions of the hydraulic press, characterization, and discussion of the press’s abilities.
Fig. 1:Click the image for a detailed description, or, for a fun video of the fabricating process, click here
Material characterization
When wanting to determine material characteristics, one way to do it is to perform destructive tests. These tests enable us to accurately predict how a material will act when under load. An important parameter is Young's Modulus. It predicts how much a material sample extends under tension or shortens under compression. The Young's modulus directly applies to cases of uniaxial stress, that is tensile or compressive stress in one direction and no stress in the other directions. It is a measure of how stiff/rigid a material is in its linear region. When a material is experiencing stresses, in its linear region, it will return to its original shape when the stress is removed (elastic deformation). Outside of the linear region, in the non-linear region, the material will undergo permanent deformation until catastrophic failure. (1)
Young’s modulus is defined as:
\begin{equation}
E = \frac{\sigma(\varepsilon)}{\varepsilon} = \frac{F / A}{\Delta L / L_{0}} = \frac{FL_0}{A \Delta L}
\end{equation}
- E is the Young's modulus (modulus of elasticity) [Pa or N/$\textrm{m}^{2}$]
- F is the force exerted on an object under tension
- A is the actual cross-sectional area, which equals the area of the cross-section perpendicular to the applied force
- $\Delta L$ is the amount by which the length of the object changes ( $\Delta L$ is positive if the material is stretched, and negative when the material is compressed)
- $L_{0}$ is the original length of the object
During our testing, we measured compressive strength. To get a more complete picture of the material properties of our fungi, we would need to also perform tensile strength tests.
Building Instructions
Bill of materials
Fig. 2: All the materials needed to build the cheap hydraulic press.
- Pressure gauge
- [a,b]: Car jack, 2 tons
- Steel square tube, length (30 cm), width (10 cm)
- Threaded steel rod, length (30 cm), Ø (10mm)
- Hex nuts (8)
- Washers (8)
Here is a fun video demonstrating the fabrication process
Fig. 3: Illustration covering each step of fabcricating the frame. 
Fabrication steps
Caution: When working with metal, be very careful of your environment and work piece. You cannot see/feel if metal is scorching warm before it is too late, and you get 2nd degree burn on your fingers. The machinery is spinning very fast, and has A LOT of torque. It wont stop or even slow down if your hair or sleeves get caught. Wear protective eyewear. After every cut in metal, make sure to deburr ALL edges. The metal is razor sharp after a cut/drill.
Frame: [Square tube, threaded rod, 8 hex-nuts, 8 washers]
- Cut a 30 cm long piece of square tubing.
- Cut your piece in half, lengthwise. You now have the top and bottom of the frame.
- If you are not able to use a saw for this step, a grinder with a cut-wheel will work. However; if you do this, you will need to mill the edges in order to make them square.
- Measure out where you will have to drill holes. The edge of the drilled hole should be 2.5 cm from any edge. Use one tap with a center-punch.
- Drill the holes. The holes should be drilled in steps in order to not destroy the drill. Start with 4mm → 6mm → 8 → 10mm.
- Cut two, 30 cm long pieces from a threaded rod. Ø10mm
- Assemble according to the schematic on fig. 3.
Car jack: [Car jack, pressure gauge]
This step will depend heavily on which car jack you acquire. We bought a car jack without a pressure gauge. If you buy a jack with a pressure gauge, disregard this part of the instructions. I will explain how to hack the car jack in general terms, and how to determine which pressure gauge to buy.
- Completely disassemble the car jack, everything, even the ball valves.
- There will be some hydraulic oil; save it. Note how you disassemble it, you will have to assemble it again later.
- Measure the diameter at the widest part of the innermost main piston (inside the red square on the fig. 4).
- This is the point at which the piston is experiencing hydraulic force. You need this area to determine which pressure gauge to buy.
- Measure where to drill (Ø1mm) an L-shaped channel in the base of the jack. This means that you will have to make 2 plunges that meet inside the base of the car jack.
- This step might be a bit tricky. Just be sure to make straight plunges with the drill-press and not to drill all the way through. Make well measured and well considered plunges. Look at fig. 5.
- Enlarge the outer hole to be able to accommodate the threads of your pressure gauge.
- Tap the enlarged hole with the appropriate thread pitch.
- This mostly follows a standard e.g. American Standard Thread.
- Clean All of the car jack parts in engine cleaner/ethanol.
- Screw in the pressure gauge after having taped the threads with teflon/plumbers tape. Optionally use an O-ring.
- Assemble the hydraulic press, fill it with the hydraulic oil.
Fig. 4: Picture of a completely disassembled car jack.
Fig. 5: A 3D view of the L-shaped channel, that needs to be drilled.
Deciding on an appropriate pressure gauge
In order to determine what pressure gauge to buy/order, you will need to do some calculations and measurements. Not to worry, it will be easy.
I will use our car jack as an example. we used these youtube videos as references:
Video 1
Video 2
You will need to know the area of the innermost piston in order to calculate the maximum pressure the gauge will need to be able to withstand. The formula is as follows:
\begin{equation}
\frac{\textrm{Maximum lifting capacity of the jack}}{\textrm{Area of the innermost piston}}
\end{equation}
The car jack our team bought had a maximum press capacity of 2000 kg (4409.25 lbs).
The radius of the innermost piston was 0.47 in. This makes the area 0.70 in ($\textrm{area}=\textrm{radius}\cdot\pi^2$).
\begin{equation}
\frac{\textrm{Maximum lifting capacity of the jack}}{\textrm{Area of the innermost piston}}=\frac{4409.25 \textrm{lbs}}{0.70 \textrm{in}^2}=6288.1 \textrm{psi}
\end{equation}
Now you know that your pressure gauge will need to be able to go to 6300 psi. Buy a pressure gauge with its maximum pressure rating as close to 6300 as possible, while making sure that the dial has a high resolution.
We opted to buy a pressure gauge that could go to 3626 psi. This means that our maximum pressing capacity is lower, but the minimum resolution is higher since the dial has more digits.
To determine the resolution of the hydraulic press we will need to multiply the minimum dial feature/step with the area factor: 1 bar (14.50 psi). Multiply this with the area of the piston 0.7.
\begin{equation}
14.50 \cdot 0.7 = 10.150 lbs
\end{equation}
This makes our press’s minimum resolution 4.60 kg/bar and the maximum load 1150 kg (2535 lbs) after having converted the units to metric.
Characterization of the hydraulic press
In order to verify the hydraulic presses real accuracy, we tried to characterize it using a normal bathroom scale. This is not optimal since we are only able to verify the very bottom of the range of the press (0-100 kg). The press goes to 1150kg. In theory, the press should be able to press with 4.60 kg/bar. This was verified. At higher pressures, the hydraulic press seemed to lose some of its power. This most likely stems from air bubbles on the inside of the pressure chamber. We were offered to have it certified with a calibration load-cell through its whole range but were not able to make it in time before the deadline.
Limitations
The machine we used to characterize our fungi with was the Instron 6022. Its maximum load capacity is 10,000 newton, or 1 ton. Its smallest step size is approximately 0.5 $\%$ of its maximum load capacity, which is 50 newton (2). This load, on our test samples, results in a pressure of 0.8 bar, because the area of the sample is 6.25 $cm^{2}$
\begin{equation}
10,000N \cdot\ 0.5 \% =50N\\
\textrm{area of test sample:} 2.5^{2}=6.25 cm^{2}=0.000625m^{2}\\
50N/0.000625m^{2}=80,000Pa=0.8bar
\end{equation}
Using the website convertunits.com, it states that 1 bar exerts 0.816 $kg/cm^{2}$. Our samples size is 6.25 $cm^{2}$, this gives us a resolution of:
\begin{equation}
6.25 cm^2 \cdot 0.816 \frac{kg}{cm^2}=5.10kg
\end{equation}
5.10 kg is the smallest resolvable load the machine can perform. Under this value, there is simply too much noise in the signal. Our homemade hydraulic press had a resolution of 4.60 kg. Our \$ 50 hydraulic press has a finer resolution than a \$ 93.000 machine.
This all sounds very nice, but there are some major caveats though. The homemade hydraulic can only be used to test the yield strength of any given material that will likely break before 1150 kg. This is done by closely observing the pressure gauge and looking for when the pressure drops on the gauge. You will usually also be able to hear when the yield strength has been surpassed. This is not the case for foam-materials though, because these do not have a defined “drop-off” in their compressional strain/stress curve. This is a limiting factor since we cannot record the continuous deformation/strain of the materials. We are essentially only able to “maybe” determine a yield point, using the hydraulic press. The Instron 6022 is able to electrically and continuously record the materials’ response to stresses, which makes it the more suitable machine in the end. What makes these machines expensive is their certification and calibration, making them very accurate throughout the entire range of the load-cell.
Results
After having characterized the hydraulic press it was used to perform the very first of our compressional strength tests. As it is apparent from the table below, high drying temperatures are favorable, since it resulted in a higher yield point of our fungus.
Table 1: Table showing the very first test results using the cheap hydraulic press. 
(1) Roylance D. 2008. Mechanical properties of materials. Retrieved here.
(2) Interview with prof. Christian Berggren, DTU institute of mechanical technology