CreationDate stringlengths 23 23 | Body stringlengths 57 10.9k | Tags stringlengths 5 114 | Answer stringlengths 39 16.3k | Id stringlengths 1 5 | Title stringlengths 15 149 |
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2015-11-29T22:19:11.990 | <p>Given this circuit</p>
<p><a href="https://i.stack.imgur.com/aQ9eD.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/aQ9eD.jpg" alt="Question"></a></p>
<p>I want to deduce the relationship between the output voltage <span class="math-container">$U_A(t)$</span> an d the input voltage <span class="m... | |electrical-engineering|control-engineering|modeling| | <p>You can write two ODEs describing the relationship, and that would be in the time-domain. Alternatively you could describe things in the frequency domain and get the relationship as a transfer function. I will show the latter. </p>
<p>Using Kirchhoff's current law at the two nodes <em>K</em> and <em>A</em>, we get:... | 6350 | connectedness between the output voltage and input voltage |
2015-11-30T16:06:43.817 | <p>All the electrical vehicles I've ever ride make that humming sound (either cars or trains).</p>
<p>What exactly causes that sound? Is it drag force in the gears? Is it a fan?</p>
<p>Or is it because of the coils (see <a href="https://en.wikipedia.org/wiki/Coil_noise">coil noise</a>)?</p>
| |mechanical-engineering|electrical-engineering|automotive-engineering|power-electronics| | <p>Correct, coil noise is generated in the windings of the motor because of Pulse Width Modulation (<a href="https://en.wikipedia.org/wiki/Pulse-width_modulation">PWM</a>) driving current. Different frequencies of modulation cause corresponding sound frequencies (may create half or double frequency oscillations as well... | 6361 | What causes the sound coming from electrical vehicles? |
2015-12-01T23:07:27.200 | <p><a href="https://i.stack.imgur.com/bIFBO.png"><img src="https://i.stack.imgur.com/bIFBO.png" alt="enter image description here"></a></p>
<p>I have a cantilever shaft 6inches in length supported on one end using a ball bearing. I am having problems of shaft wobbling in the bearing. I cannot have support on the other... | |mechanical-engineering|bearings| | <p>If the dimensions are fixed, a careful selection of alloy or hardness that has a higher inherent damping would also reduce deflection while the shaft is rotating. </p>
| 6375 | How can the wobble of a rotating cantilever shaft be reduced? |
2015-12-02T00:51:38.413 | <p>I am designing a box and lid (for a home-made micro computer). Using Autodesk Inventor (Student Version), I've created my box which looks something like this:</p>
<p><strong>I plan on 3D printing (ABS Plastic) the box and lid in the end.</strong></p>
<p><a href="https://i.stack.imgur.com/CdyHb.png" rel="nofollow n... | |design|plastic|3d-printing| | <p>You seem to want an a slight interference fit so the top will snugly seat into the housing. Depending on your wall thickness and size you could probably oversize the "male" portion of the cap like .002-.003" compared to the "female" dimension. </p>
<p>That being said, and understanding that 3D printing generally ca... | 6379 | What should the size difference be between a lid and a container? |
2015-12-02T02:29:42.313 | <p>In the book, Design of Liquid-Propellant Rocket Engines, there is a practice problem written as such.</p>
<p>"Determine the design values of $(C_*), (C_f), and (I_s)_t$ for the engine thrust chambers of the stages of the hypothetical Alpha vehicle, with the following assumed design parameters."</p>
<p>I am given ... | |aerospace-engineering|thrust| | <p>So I figured it out, I first took this equation.</p>
<p>$(C_F) = (CT_F) - (E)(P_a)/(P_C)_N$</p>
<p>Then I isolated $(CT_f)$ and substituted $(C_F)$ equation resulting in</p>
<p>$C = \sqrt{\frac{2y^2}{y-1)}*\frac{2}{y+1}^{y+1/y-1}*(1-\frac{P_e}{P_C}^{\frac{y-1}{y}})+e(\frac{P_e - P_a}{P_C})} + e\frac{P_e}{P_C}$</p... | 6381 | What is the equation to calculate the Thrust coefficient within a set of parameters? |
2015-12-02T09:22:45.243 | <p>What determines the maximum torque of a DC motor?
How is this related to the equations</p>
<p>$$E=k\omega$$
$$T=kI$$</p>
<p>where</p>
<ul>
<li>$E$ is electromagnetic force / voltage (V)</li>
<li>$\omega$ is rotational speed (rad/s)</li>
<li>$T$ is torque (Nm)</li>
<li>$I$ is current (A)</li>
<li>$\phi$ is flux (W... | |electrical-engineering|motors|torque| | <p>Torque of a motor is directly proportional to current. Therefore, the maximum torque a motor can produce is limited by the maximum current it can handle.</p>
<p>The maximum steady state current a motor can handle is limited by the heat it can safely dissipate, which is proportional to the square of the current. T... | 6384 | What determines the maximum torque of a DC motor? |
2015-12-02T10:26:17.377 | <p>Assume you have a system model that is controlled by a PID controller (feedback). You want to add feedforward to improve the characteristics of the controlled system. How can you design the transfer function of the feedforward?
(Cf. <a href="http://engineeronadisk.com/book_modeling/images/feedback4.gif" rel="nofollo... | |control-engineering|feedback-loop| | <p>The idea of using a feedforward component in a control system is to provide near <strong>instant action</strong> of the plant output to the input command. So a suitable choice of transfer function which connects the command to the plant input directly is an inverse model of the plant. The feedback control can then s... | 6385 | How to improve a PID control loop by adding feedforward? |
2015-12-02T15:33:39.007 | <p>I am looking to test the <a href="https://www.tekscan.com/products-solutions/force-sensors/a401" rel="nofollow noreferrer">FlexiForce</a> sensor in measure force, however for accurate readings the load needs to be disturbed evenly over the sensing area. As such I am having "discs" made to cover the sensing area. For... | |materials|metals|manufacturing-engineering|deformation| | <p>1) I've used several brands of FSRs, including FlexiForce and you're very unlikely to get results usable in trade; their responses to pressure vary with temperature (because, I suspect, the stiffness of the polymers in the sensor itself vary w/temp.)</p>
<p><strong>2) The application guides I've read strongly sugge... | 6388 | Material selection for weight scale |
2015-12-02T16:42:57.263 | <p>In commercial fire sprinkler systems or large farm irrigation systems, is the thrust produced by the water a major design consideration? At what stage in the design process is this taken into account?</p>
| |systems-design|thrust| | <p>Product design often involves juggling many parameters at the same time, prioritizing them, then testing a design. In sprinklers themselves, the forces associated with the thrust are much lower that the forces the sprinkler experiences during assembly or from internal pressure; so typically they are not a design pri... | 6392 | Thrust consideration in sprinkler and irrigation systems |
2015-12-03T07:04:30.133 | <p>I am modelling my structure using FEM, and my structure contains line elements (1D) such as beams and columns and area elements (2D) such as walls and columns.</p>
<p>My question is that, how can I proceed to do modelling, and how can I interpret the results for stress and strain, especially at the places where 1D ... | |structural-engineering|finite-element-method|structural-analysis| | <p>Say we have a slab supported on a beam.</p>
<p><a href="https://i.stack.imgur.com/lVpmp.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/lVpmp.png" alt="Beam composite with slab"></a></p>
<p>The centroid of the slab and the centroid of the beam are not coincident. Fortunately, in FEM software pac... | 6399 | How should one model a structural model with both line elements and area elements? |
2015-12-03T17:13:29.183 | <p>While this question pertains to smartphone , it is being asked from purely an electrical engineering view (My electrical knowledge is very basic)</p>
<p>Trying to understand if charging a cell phone and using it is recommended or not, I came across this <a href="http://batteryuniversity.com/learn/article/charging_l... | |electrical-engineering|battery| | <p>Based on the answers here it shows that interpretation of my results was wrong.</p>
<p>This was independently validated and supported by Bruce Huang of Battery University. Main points from him were</p>
<ol>
<li>Parasitic Load would not delay current drop indefinitely, it does do momentarily.</li>
<li>Keeping the s... | 6406 | Charging a smartphone battery while using it |
2015-12-04T02:24:26.047 | <p>I'm trying to measure water elevation as a function of distance in a water tank, viewed through the glass wall, as shown here:</p>
<p><a href="https://i.stack.imgur.com/jWsei.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/jWsei.jpg" alt="tank"></a></p>
<p>The height variations that's of interes... | |measurements|optics| | <p>How about this?</p>
<p><a href="https://i.stack.imgur.com/boZoJ.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/boZoJ.jpg" alt="enter image description here"></a></p>
<p><em>Photo 1. Inclined tank level scale.</em></p>
<p>The inclined scale means that graduations can be spread more widely for e... | 6410 | Lens to "stretch" or enhance vertical resolution in a photo |
2015-12-04T06:56:49.583 | <p>I need a 8 m x 4 m x 0.6 m RC plinth (mechanical requirement) which needs to be built onto loose gravel. Obviously I am going to over excavate, back fill with selected material and bed my plinth on that. </p>
<p>The plinth accommodates 2 x 65 m<sup>3</sup> water tanks, placed symmetrically. The tanks are $\phi$3 m... | |structural-engineering|finite-element-method|foundations| | <p>Before jumping into elastic support conditions, you have to realise that it's <strong>not</strong> a ground beam. For three reasons:</p>
<ol>
<li><p>With a minor axis width to depth ratio of 6ish, it's not far away from a square. If you stick a wide support somewhere near the ends of the section, the load will si... | 6414 | How to model elastic support in FEM? |
2015-12-04T15:12:14.390 | <p>Below is a picture of two supporting posts in my basement. The posts are directly underneath the kitchen/dining room. Would it be feasible to remove one or both of the posts? What would the cost roughly be to make this change? </p>
<p>Note: I know that I should have a structural engineer take a look before actuall... | |structural-engineering|beam| | <p>Whenever one speaks about removing a structural element (column or beam), the initial hypothesis must always be:</p>
<blockquote>
<p>NO! GOD NO! WHAT ARE YOU DOING!</p>
</blockquote>
<p>The second hypothesis must always be:</p>
<blockquote>
<p>No. No. No. No.</p>
</blockquote>
<p>That being said, it can be d... | 6424 | Can I remove one or both of these support posts in my basement? |
2015-12-06T03:14:43.013 | <p>I know that digging tunnels is always <em>much</em> more costly than building ways or train above ground.</p>
<p>Why doesn't the Channel Tunnel start around the coastline? Why does it have an around 10 km long portion under land on the British side?</p>
| |civil-engineering|geotechnical-engineering|rail|tunnels| | <p>The picture, below, of the exaggerated long section of the Channel Tunnel was taken from <a href="https://en.wikipedia.org/wiki/Channel_Tunnel" rel="nofollow noreferrer">Wikipedia</a>.</p>
<p><a href="https://i.stack.imgur.com/MFNuz.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/MFNuz.png" alt="... | 6435 | Why does the Channel Tunnel enter the ground around 10 km from the coast? |
2015-12-07T03:09:39.203 | <p>I'm designing a little tester for a project which uses a pneumatic cylinder. The pneumatic cylinder's purpose is to apply an impact on a hard surface to test for deflection of the surface. When I looked around catalogs, the pneumatic cylinders have a theoretical force output, for example 3,016 N at 0.6 MPa with an e... | |mechanical-engineering|applied-mechanics| | <p>In general pneumatics are quite precise when it comes to force but modeling energy in this context brings in a lot of additional unknowns which make be difficult to measure. </p>
<p>The most common method of impact testing is to use an impactor fixed to a pendulum as it's fairly easy to determine the kinetic energy... | 6441 | Pneumatic cylinder force output and impact energy |
2015-12-07T12:02:59.790 | <p>The high water has some energy E = mgh. In the basic school, we were told that hydropower plants extract the energy of "falling water". Now, <a href="https://physics.stackexchange.com/questions/221243">that banned principle</a> says that if your water falls upon still turbines, you will loose energy. The water will ... | |energy-efficiency|renewable-energy|power-engineering|wind-power| | <p>The theoretical maximum efficiency of a wind turbine is the Betz Limit, which is $\frac{16}{27}$ ( ~ 59.3%).</p>
<p>The result <a href="http://www.reuk.co.uk/Betz-Limit.htm" rel="nofollow">dates back to 1919</a>.</p>
<p>The Betz limit is, as you note, speed invariant. To get an intuition as to why, consider the sy... | 6444 | What theoretical efficiencies can wind / hydro turbines achieve? |
2015-12-07T14:26:56.197 | <p>I'm studying the design of storm sewers and I had two questions relating to air gaps in storm pipes:</p>
<ol>
<li><p>According to sources I've come across, flow through storm pipes
require an air gap so as to maintain open channel flow. Do I need to
maintain a specific amount of air gap? Or will any amount of air g... | |civil-engineering|hydrology| | <p>There are additional features of the air gap besides pressure relief (Especially in small domestic pipes).</p>
<ul>
<li>Maintenance clean out access</li>
<li>View port for viewing if flow is blocked</li>
<li>Alleviating a small amount of BOD from system</li>
<li>Reducing odor problems with adequate air flow</li>
<l... | 6449 | How much air gap is required in a storm pipe? |
2015-12-08T04:51:30.537 | <p>I have two columns of water at different (but constant) temperatures. If I calibrate a pressure transducer using the first column at differing heights, when I measure the second column how do I account for the change in temperature (and water density)?</p>
<p>I want to measure pressure in megapascals (MPa) so for t... | |fluid-mechanics|pressure| | <p>The pressure will be the same regardless of the temperature. So, the two columns will have the correct pressure recording. However, the height of the column will vary. </p>
<p>i.e. - Say you have your pressure transmitter reading for calibration a 10C column (999.7 kg/m^3). The results are:</p>
<p>0.5m - 4.9 k... | 6460 | Calibrating and measuring pressure in Megapascals using a pressure transducer |
2015-12-08T14:52:14.787 | <p>Normal sealings and gaskets are made from NBR for use in conjunction with aqueous solutions of ethylene glycol which are common coolants for various purposes. </p>
<p>However to keep sulphur out of a cooling system and the surrounding area I want to change NBR sealings against silicone sealings. I've read some vagu... | |materials|cooling| | <p>Based on the available data it looks like it will perform well: </p>
<ul>
<li><a href="http://www.efunda.com/designstandards/oring/oring_chemical.cfm?SM=none&SC=Ethylene%20Glycol" rel="nofollow">efunda.com - (4) Good, both for static and dynamic seals</a><br></li>
<li><a href="http://www.pspglobal.com/fluid-co... | 6463 | What happens to silicone gaskets (siloxane rubber) in presence of ethylene glycol? |
2015-12-09T14:35:09.580 | <p>I want to contain a very small PCB (roughly a square centimetre) in a casing. For demonstration purposes I want to 3D print a couple of those casings as well.</p>
<p>The most obvious method available would be using ABS for the printed casings. However, nylon appears to be smoother and tougher. Those traits are ofte... | |electrical-engineering|materials|rf-electronics| | <p>I am not sure if this will help, but when I have used any plastic in antenna designs, or RF power amplifiers, I would put them in a microwave oven and see if they heated up. Most would stay cold, but every now and then some would get warm, and sometimes I could hear some audible arcing. My only experience is at Ham ... | 6481 | Are there any differences between using nylon or ABS for RF electronic cases? |
2015-12-10T00:35:23.007 | <p>How far must the surface temperature of a UL-listed combustion appliance rise to prohibit the manufacturer from specifying it for a zero clearance to combustibles installation?</p>
<p>(I looked in UL 127 but was unable to find a straightforward answer there.)</p>
| |combustion|heating-systems|ul| | <p>I <em>finally</em> found the answer to this in a BIA (Brick Industry Association) <a href="http://mha-net.org/docs/BIA01.PDF" rel="nofollow noreferrer">test protocol</a> for standardized brick fireplace designs. To quote what they're saying about UL-127:</p>
<blockquote>
<p>In general, after temperature equilibr... | 6486 | What surface temperature (rise) is required to (dis)qualify a combustion appliance from obtaining a "zero clearance to combustibles" rating? |
2015-12-10T17:40:55.017 | <p>I have to calculate the uncertainty of measurement for an LVDT Linear displacement transducer used for measuring length. Uncertainty calculations are ruled by ISO 17025 but there are no (at least haven't found) specific guidelines for the mathematical procedure of uncertainty for LVDT sensors. There are many guides ... | |sensors|measurements|mathematics|standards|metrology| | <p>For the Maths of calculating uncertainty the standard document is the <a href="http://www.bipm.org/en/publications/guides/gum.html" rel="nofollow">GUM</a>. Which describes all the maths but can be somewhat unclear if you don't already have some idea how it is supposed to work.</p>
<p>Depending on your current level... | 6494 | Uncertainty Calculation of LVDT displacement transducers for length measurement |
2015-12-11T00:37:31.507 | <p>I have a 5" x 4" x 3/8" plastic panel (wall thickness of 1/8", ribbed). I need to slide the panel over a 12" plastic track that is U-shaped (like a skateboard ramp). This motion could be repeated 2 million+ times. </p>
<p><a href="https://i.stack.imgur.com/CkuPE.png" rel="nofollow noreferrer"><img src="https://i.st... | |mechanical-engineering|materials|mechanical-failure|bearings| | <p>Without knowing additional details, my attempt at a catch-all answer:</p>
<p><strong>Summary:</strong> attempt to minimize wear. Millions of cycles is a lot for even low-load contact surfaces. Use components with high hardness and smooth materials. PTFE or UHMWPE backed by metal for full-contact bearings, and AISI ... | 6499 | Are Rolling-Element Bearings Practical for Light Loads? |
2015-12-11T06:58:38.283 | <p>What equations are needed to describe the forces and properties of the kind of mechanisms used in a machine that harnesses the gravitational potential energy of a suspended weight to rotate the shaft of a permanent magnet DC generator (i.e. the <a href="http://gravitylight.org" rel="nofollow">gravity light</a>)?</p>... | |mechanical-engineering|gears|energy-efficiency| | <p>Taking the force exerted by the mass and converting it to rotational force or torque will involve the following equations:</p>
<p>F = g*(mass) where g = 9.81 and<br>
T = r*F where r is the radius of the pulley from which the suspended mass is hanging. This is the torque that turns the generator.</p>
<p>When other ... | 6502 | Equations relevant to gravity powered clocks and machines such as the gravity light |
2015-12-11T20:44:47.790 | <p>I was searching for information about pressure-volume processes when I read, in a heat engineering book, "The process is polytropic with $PV^n = \text{constant}$." </p>
<p>How can I know that a real life process follows this model? Are all processes related to this heat engineering, pressure-volume, etc., in fact p... | |thermodynamics|pressure| | <p>No, all thermodynamic processes are not polytropic. As an example, consider a real engine cycle. Any undergraduate engineering thermodynamics text should have a plot showing the true P-V diagram. You also can see <a href="http://4mechtech.blogspot.com/2013/12/indicator-diagram-or-p-v-diagram-actual_9.html" rel="nore... | 6508 | Are all pressure-volume processes polytropic? |
2015-12-11T22:02:13.497 | <p>I have a quadrotor aircraft (4 motors/propellers around a center housing) with some electronics in an electronics housing. Looking to cool the electronics with propeller downwash. </p>
<p><a href="https://i.stack.imgur.com/RDKZW.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/RDKZW.png" alt="ente... | |fluid-mechanics|heat-transfer|aircraft-design| | <p>It depends on the velocity across P1 and the pressure differential across your blades. It would be hard to determine without testing or using computation fluid dynamics. That is probably overkill and its much easier to just change the geometry to do what you need. Hazzey mentioned a scoop in the comments; that would... | 6509 | Using propeller downwash for electronics cooling |
2015-12-12T17:04:15.657 | <p>I have a book that claims:</p>
<blockquote>
<p>A metal will have more of a tendency to dissolve another metal of higher valency than one of a lower valency.</p>
</blockquote>
<p>I interpret this as saying that a metal with higher valency will dissolve more easily into a host metal than it would if it had a lower... | |materials|metallurgy| | <h2>Summary</h2>
<p>Your book is correct. The same valence (+3/+3 solvent/solute) will be most likely to have large solubility, while higher valences (+3/+4) will be more likely to have high solubility than lower valences (+3/+2).</p>
<p>Putting them in order as an example:</p>
<pre><code>Solvent / Solute
+3 /... | 6511 | How does the relative valency of the impurity and host metals affect solubility in a substitutional solution? |
2015-12-13T09:07:18.393 | <p>A wooden police baton has to be hung on the back of an officer and released only when s/he wants it to be released. I thought about "push to stow, push to release". This is a thought experiment, I am not a manufacturer...</p>
<p>The baton is smooth without grooves so alternative solution of releasing by rotation (l... | |mechanical-engineering| | <p>The mechanism you're looking for is named <strong>push-push latch</strong>. They are used in a lot of places and there are various patents for that. You can check <a href="https://www.google.com/patents/EP1596030A2?cl=un" rel="nofollow noreferrer">this patent</a> granted at 2005. It is for a small holder but it can ... | 6516 | Mechanism for a mechanical latch/clamp |
2015-12-14T13:24:30.367 | <p>For simplicity we're going to ignore aerodynamics and vehicle mass for a moment...</p>
<p>Are small (around 1 litre) car engines designed to tolerate a higher duty cycle than large (2+ litre) car engines? </p>
<p>Cars are usually all travelling at roughly the same speed which means the engines will be putting out ... | |automotive-engineering|engines| | <p>Most (modern) small and large car engines are designed for 100% duty cycle. This means that at 100% rated power(gas pedal all the way down) the engine can run continuously. Heat dissipation is the limiting factor like Dave Tweed stated. Cars that are not designed to continuously dissipate 100% of the heat generated... | 6526 | Are small car engines designed to tolerate a higher duty cycle than large car engines? |
2015-12-16T08:02:52.703 | <p>I am working on a simple program that would help welder to count how much ferrite, austenite etc. there is in weld. I am focusing on stainless steel.</p>
<p>I have decided to use 3 graphs: Schaeffler, De Long and WRC. What I don't know is for which materials can I use each of these graphs, to get reliable results. ... | |steel|metallurgy|welding| | <p><strong>You are not exactly right. The purpose of Cr and Ni in stainless steel, besides the stainless part, is to tailor the microstructure. Cr promotes ferrite, Ni promotes austenite. Other elements have similar effects and must be taken into consideration. Beware of carbide formation changing properties and reduci... | 6545 | Schaeffler, De Long, and WRC welding diagrams - which steels can be used? |
2015-12-17T08:04:17.747 | <p>For the last hour I have been trying to understand what $\dfrac{\partial p}{\partial s}ds$ is in Euler's equation but I have a problem. You can see this image:</p>
<p><a href="https://i.stack.imgur.com/7scvT.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/7scvT.jpg" alt="enter image description here"></a>... | |mechanical-engineering|fluid-mechanics|civil-engineering| | <p>Whenever a fluid flows in a pipe, it flows due to difference in pressure. Due to this difference in pressure, there is a pressure gradient which is $\dfrac{\partial p}{\partial s}$. $\dfrac{\partial p}{\partial s}\ \text{d}s$ is the change in pressure over the length $\text{d}s$. $p+\dfrac{\partial p}{\partial s}\ \... | 6558 | ∂p / ∂s ds Component in Euler's Fluids Equation |
2015-12-18T05:08:20.240 | <p>A simple thermostat will turn on at one temperature and off at a higher temperature. This keeps the thermostat from cycling on and off too quickly. The difference between these values is sometimes called <a href="https://en.wikipedia.org/wiki/Deadband#Thermostats" rel="nofollow noreferrer">dead band</a> and sometime... | |control-engineering|terminology| | <p>The difference between the cut in and cut out of a temperature or a pressure control is the 'differential'. Simple controls have set differentials.
I would use 'hysteresis' where there is a loss of movement in a mechanical gear and/or lever train when the train reverses direction. This is sometimes termed the 'lash'... | 6576 | What do you call the difference between the on and off temperatures in a simple thermostat? |
2015-12-20T19:25:05.857 | <p>I have calculated the shear flows and center of an L shaped profile. I assume they are correctly calculated (I followed the same steps as during the lectures for an I shaped profile). However, I have some problems with the interpretation of the results. The results are shown in my simple sketch.</p>
<p>The height of... | |mechanical-engineering|stresses|structural-analysis| | <p>Firstly, the shear center is the point at which an applied load produces no torsion on the section. For a singly or doubly symmetric section, the shear center will lie on the axis of symmetry. For the unequal leg angle shown here, we can say by inspection that the shear center must be at the intersection of the two ... | 6601 | Interpretation of shear flow/shear center of L-profile |
2015-12-22T08:54:11.327 | <p>For torsional constant, analytical formulas are available for some standard steel sections as shown in this <a href="https://en.wikipedia.org/wiki/Torsion_constant" rel="nofollow noreferrer">wiki page</a>.</p>
<p>But what about arbitrary shapes? How can I obtain the formulas for torsional constants? If no such form... | |materials|structural-engineering|steel| | <p>For arbitrary thick-walled shapes, there are no generic formulas available. You have to calculate the torsion constant using numerical methods, e.g. FEM or BEM.</p>
| 6613 | First principle derivation for torsional constant |
2015-12-22T22:58:38.233 | <p>Could someone please explain me why the velocity of point P and P' aren't the same? Appearently it is because the angular velocity of point A and B aren't the same.</p>
<p><a href="https://i.stack.imgur.com/GH4r6.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/GH4r6.png" alt="enter image descript... | |kinematics| | <p>The velocity of P' is perpendicular to AD, and the velocity of P is perpendicular to BP. So clearly the directions are not the same. Thus there is relative velocity between P and P' as shown in the diagram. Now, if gyroscopes are mounted at D, P', or any point on AD, except A, they will all measure the same angular ... | 6621 | Why do 2 points on a mechanism not have the same angular velocities? |
2015-12-22T23:53:56.660 | <p>In <a href="https://engineering.stackexchange.com/q/6613/3353">this question</a> I ask about how to perform a first-principle derivation of the torsional constant of a section. It appears that there is no such analytical derivation for torsional constant, so my question therefore becomes: what about FEM derivation f... | |modeling|finite-element-method| | <p>Make a long shaft with your chosen section. Fix one end by 3dof restraints at each node. Put a closing plate across the other end and apply a torque, hence back calculate your torsional constant. Double the length of the shaft and check you get the same answer. St Venant's principle is the reason you want a long sha... | 6622 | How do I use FEM to derive the torsional constant of an arbitrary shape? |
2015-12-23T09:17:42.740 | <p>I'd like to compute the response to a step function of a electrical/thermal system. Generally I can "easily" compute the transfer function $H$:</p>
<p>$$H(\omega) = \frac{V_{out}(\omega)}{V_{in}(\omega)}$$</p>
<p>Since the Fourier transform ($\mathcal{F}$) of the Heaviside function is (computed with WA):</p>
<p>$... | |electrical-engineering|mathematics|signal|transfer-function|signal-processing| | <p>The main reason is likely due to Wolfram Alpha applying the inverse Fourier transform as a second Fourier transform. In fact, doing so "flips time" - as can <a href="https://en.wikipedia.org/wiki/Fourier_transform#Invertibility_and_periodicity" rel="nofollow noreferrer">be shown mathematically</a>: </p>
<p>Definin... | 6624 | Response of a system to a step function (Heaviside function) |
2015-12-23T10:15:03.643 | <p>I ve tried to solve this problem in so many ways but still didn't manage to do it...</p>
<p><a href="https://i.stack.imgur.com/y9G91.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/y9G91m.jpg" alt="enter image description here"></a></p>
<p>What would be the correct way to solve it please?</p>
<... | |mechanical-engineering|kinematics| | <ul>
<li>First you build a kinematic chain between <em>A</em>, <em>B</em> and <em>D</em> with radius $r$ between <em>AB</em> and the length $\ell$ between <em>BD</em>. The orientation angles from vertical are $\theta$ and $\phi$ respectively.
<ol>
<li>$(x_B,y_B) = (x_A,y_A) + (-r \sin\theta,r \cos \theta)$</li>
<li>$(... | 6625 | How to calculate the velocity of a piston-like linkage? |
2015-12-24T21:48:10.713 | <p>I am in the process of selecting a linear rail system for a 5ft x 10ft cnc laser cutter. <a href="http://openbuildspartstore.com/delrin-mini-v-wheel-kit/" rel="nofollow">Delrin polymer rollers</a> on 2 inch square extruded aluminum tube is an economically attractive solution. I have had success with them on a 3d pri... | |mechanical-engineering|failure-analysis| | <p>Given that you're using extruded aluminium rails polymer rollers are likely to be the best solution as anything harder will likely make the wear rate of the aluminium more of an issue.</p>
<p>To be honest using extruded aluminium for a machine tool is always going to be a cheapest rather than best solution compared... | 6639 | What is the longevity of Delrin rollers on aluminum linear rail? |
2015-12-25T09:07:29.317 | <p>I would like to design a long, uniform magnetic field using Hemholtz coils but am not sure how far I can separate them before the field lines diverge and become two loops that go around each coil rather than one which goes through both.</p>
<p>I have formulae for finding the magnetic flux at different points but I ... | |mechanical-engineering|electrical-engineering|magnets| | <p>Short answer: Not very far.</p>
<p>I had this question one or two years ago. At that time I did a simple calculation of $B$ along the symmetry line for Helmholtz coils with non-standard distance, i.e. the position of the two coils being different from $+R/2$ and $-R/2$ ($R$ being the radius of the two coils). The h... | 6642 | How to calculate the maximum spacing between Hemholtz coils? |
2015-12-27T01:57:30.460 | <p>I would like to essentially flatten or smooth the surface of a viscous liquid after dropping an object into it, without actually touching the liquid. For example, if I drop a rock into a tub of oil, I need the oil to move into the void and return to having a smooth surface as fast as possible.</p>
<p>It seems that ... | |fluid-mechanics|magnets| | <p>Some quick dimensional analysis for a Newtonian fluid suggests that the settling time scales as follows:</p>
<p>$$\tau = \sqrt{\frac{L}{g}} f\left(\frac{\nu}{\sqrt{g L^3}}\right)$$</p>
<p>where $\tau$ is the time it takes for the liquid surface to settle, $L$ is some characteristic length of the dropped object (sa... | 6659 | How to 'smooth/flatten' the surface of a disturbed liquid without contacting it? |
2015-12-27T15:29:02.230 | <p>I am familiar with the basic concepts of fits and tolerances, and I am aware of the various online calculators for determining them. However, I don't understand how to apply those numbers to my actual CAD design for the parts that I want to fit together. None of the calculators seem to account for the actual manufac... | |mechanical-engineering|machining| | <p>I think you may be getting a little confused here. There is a fit tolerance, which determines how easy it is to insert and rotate a pin in a joint, and then there is machining tolerance, which is how accurately a shop can match your nominal values. </p>
<p>If your shop can't meet your printed fit tolerances, you're... | 6667 | How do you apply fits and tolerances when designing hole and shaft? |
2015-12-28T00:20:40.777 | <p>I noticed many kitchen utensils or stand mixer attachments are made with injected aluminum. Aluminum (~\$20/kg) is usually more expensive than stainless steel (~\$10/kg) and is not compatible with dishwashers. </p>
<p>For instance, I have a peeler made with anodized aluminum and a KitchenAid attachment with some al... | |steel|aluminum| | <p>The aluminium has different temper, for the utensil usually use 1 series aluminum alloy which is much softer, so it's easier to cast. And aluminum is light, also aluminum can be recycled which is environmentally friendly. Most of all, for business, profits are very important. </p>
| 6670 | Why do manufacturers still make aluminum kitchen utensils? |
2015-12-28T18:59:59.827 | <p>I have a pump that I want to use to pump a solvent. It is hard black plastic so I'm pretty confident it is either ABS or polypropylene (it wasn't expensive enough to be some more exotic plastic).</p>
<p>My solvent will rapidly dissolve ABS but it will work great if its PP. Anyone have a strategy to tell which it is... | |plastic| | <p>ABS and Polypropylene have very different chemical resistances, with Polypropylene very resistance and ABS no so much. Acetone, Methyl Ethyl Ketone (MEK), 2-Butanone, and Methylene Chloride will dissolve ABS but not Polypropylene. Thus put a small drop of the solvent on the surface, and mush it around a little wit... | 6682 | How to determine whether plastic is ABS or Polypropylene? |
2015-12-29T13:04:38.090 | <p>How can I control a Four-Bar Infinity Coupler such that it does not accidentally become a Paralellogram Linkage? It seems to me that, when the bars are all horizontal, gravity could change the movement of the green driven linkage.</p>
<p><a href="https://www.youtube.com/watch?v=NZZtXUcRZVs" rel="noreferrer">https:/... | |mechanical-engineering|design|linkage| | <p>Gearing is complicated by the fact that the driver bar moves at a constant speed while the driven bar changes speed.</p>
<p>Could this gearing Solution work? The gear should only engage when the center bar is fully extended to the right or fully extended to the left.</p>
<p><a href="https://i.stack.imgur.com/99uRy... | 6696 | Design of a Four-Bar Infinity Coupler Linkage |
2015-12-30T02:35:30.890 | <p>For me, it's a bit hard to imagine where shear center can be, and what purpose it serves. <a href="http://www.civilengineeringterms.com/mechanics-of-solids-2/shear-center/">The definition</a> I found online is very vague:</p>
<blockquote>
<p>Shear center is defined as the point on the beam section where load is
... | |mechanical-engineering|structural-engineering|beam| | <p>I hope answering this after all this time is not a huge faux pass, but this question comes up on search engines when looking for shear center calculations.</p>
<p>First, some preliminaries.</p>
<ul>
<li>This applies to <a href="https://en.wikipedia.org/wiki/Simply_connected_space" rel="nofollow noreferrer">simply co... | 6705 | What is the mathematical derivation for shear center of a beam? |
2015-12-30T17:06:34.867 | <p>Are there any established (compact and simple) solutions for turning two 5mm rods/shafts side-by-side together by driving a singe motor? The torque is about 5kg-cm. The one I'm thinking of is the coupling rod:</p>
<p><a href="https://i.stack.imgur.com/JFAVT.png" rel="nofollow noreferrer"><img src="https://i.stack.i... | |mechanical-engineering|motors| | <p>This <a href="https://engineering.stackexchange.com/questions/6696/design-of-a-four-bar-infinity-coupler-linkage/6697#6697">Engineering SE Question</a> explains why a single parallel link will not work. When the link is at <a href="https://en.wikipedia.org/wiki/Dead_centre_(engineering)" rel="nofollow noreferrer">to... | 6712 | Rotating two shafts together - coupling rod? |
2016-01-01T05:57:11.507 | <p>I am studying the performance of volumetric solar receivers (specifically ceramic foams) versus the change of many parameters: solar flux, surface temperature, porosity, pore diameter, flow pressure and flow velocity. I have seen two ways in the literature to model porous media:</p>
<ol>
<li>Drawing a complex 3D st... | |cfd|turbulence|porous-medium| | <p>Short answer: The FLUENT approach is trivial.</p>
<p>Many information are lost due to the space-averaging process - over a representative elementary volume - of the governing equations (which is the essence of every porous model that tries to avoid the complexity of the real geometry of the porous media), So any tu... | 6723 | How safe is this assumption for turbulence modelling in porous media? |
2016-01-01T09:35:52.363 | <p>I have a setup in which a bolt threaded on two ends with an unthreaded shank in the middle will be rotated by the unthreaded shank area. That is, the bolt's axis of rotation is roughly the red cross:</p>
<p><a href="https://i.stack.imgur.com/Pu9wQ.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/P... | |mechanical-engineering|bolting| | <p>depends on the application but a TCB Stud may be a possibility - this has a left hand thread on the end opposite the spline and a right hand thread on the end nearest the spline. The left hand thread is tightened by the installation tool into a left-handed threaded nut and then the right hand threaded nut is tighte... | 6724 | Rotating a bolt around the centre |
2016-01-02T03:27:18.340 | <p>Suppose there is an accelerating mass along a straight line, and you would want to convert that linear motion into rotary motion. Is it possible to convert that accelerating linear motion into constant speed rotary motion? Could you suggest mechanisms that I can use?</p>
| |mechanical-engineering|applied-mechanics| | <p>Do you really mean<br>
ACCELERATING linear to
CONSTANT rotary motion? </p>
<ol>
<li><p>A variable ratio drive as in the DAF cone drive now used in a number of Japanese gearboxes would work.</p></li>
<li><p>Provided the accelerating linear motion is repeatable and predictable, below one turn this can be seen as a ... | 6735 | Converting accelerating linear motion into constant rotational motion |
2016-01-03T01:19:18.717 | <p>Recently I watched <a href="http://www.imdb.com/title/tt3659388/" rel="nofollow">The Martian</a> and the space vehicle <em>Hermes</em> in the movie had a rotating platform. I wonder if that would significantly cause the vehicle to be inclined in direction? Does a spinning platform/living space on a space vehicle, us... | |mechanical-engineering|aerospace-engineering| | <p><a href="https://en.wikipedia.org/wiki/Angular_momentum#Conservation_of_angular_momentum" rel="nofollow">Conservation of angular momentum</a> creates a <a href="https://en.wikipedia.org/wiki/Gyroscope" rel="nofollow">gyroscopic force</a> when the angle of the space craft is changed.</p>
<p>The trajectory however is... | 6744 | Does a rotating platform on a space vehicle affect the vehicle's trajectory? |
2016-01-04T01:28:09.690 | <p>I've been designing an electric skateboard which is driven by only one of the rear wheels (for the moment). As I was picking out motors for the board, I soon realized I would need to find a balance between torque needed to climb hills, and RPM to get a good top speed.</p>
<p>So I'm searching for the best KV (RPM/v)... | |electrical-engineering|motors|applied-mechanics|energy|kinematics| | <p>The answer provided by Dave is correct but it covers only a very specific case of no-friction and constant speed. There are three forces acting on a vechicle which must be accelerated from 0 to v speed over a slope:</p>
<p><a href="https://i.stack.imgur.com/mxvZb.png" rel="nofollow noreferrer"><img src="https://i.s... | 6756 | Calculating torque needed to climb a graded hill |
2016-01-04T18:18:02.730 | <p>We are testing a new ultrasound product using a Texas Instruments PGA450 automotive transducer.</p>
<p>Three of us are sharing a lab and we need some kind of ultrasound-blocking partition walls around each product to prevent interference. Think cubicle walls that absorb ultrasound.</p>
| |mechanical-engineering|electrical-engineering|automotive-engineering| | <p>Typical towels do a pretty good job of not echoing ultrasound around too much, and also attenuate ultrasound going thru them. Ordinary sheetrock walls are really bad because they are great mirrors for ultrasound.</p>
<p>There are special materials for absorbing sounds at various frequencies, but hanging a bunch of... | 6776 | How can I block ultrasound from an automotive transducer at about 8'? |
2016-01-04T20:39:11.923 | <p>I have a DC motor with a shaft with a diameter of x. It would produce some torque T because torque is proportional to radius. If I stuck a pulley on the shaft of radius 2x, then I would produce twice as much torque, right? And then if I attach this to a gear with a ratio of 2:1, I would again double the torque.</p>
... | |applied-mechanics|gears|torque| | <p>It is more useful to say that torque is proportional to the ratio of the radii of a pair of pulleys or gears. Also RPM is reduced or increased in the same ratio so a small diameter gear driving a larger one increases torque but reduces RPM at the output shaft. </p>
<p>E.g., if you had a motor producing 100 Nm of to... | 6780 | What is the relationship between drive shaft diameter and torque output? |
2016-01-04T21:27:18.527 | <p>I'm having trouble identifying the diameter of the reinforced steel bars in the structural steel design for a slab and a beam of a building complex. You can see it
<a href="https://www.dropbox.com/s/xszs9wurf8gmk65/POS%20300%2C400%2C500%2C600%2C700%2C800%20%281%29.pdf?dl=0" rel="nofollow">here (PDF)</a>.</p>
<p>I'... | |civil-engineering|structural-engineering| | <p>The column design schematics are "POS S1" and "POS S2", on the bottom center-right of the page.</p>
<p>The nomenclature here has some peculiarities I'm unsure about, so someone else might come up with a better answer, but here goes... You'll see that there are basically two ways to describe the rebar:</p>
<ul>
<li... | 6783 | Identifying the diameter of reinforced steel bars in a column design schematic |
2016-01-05T04:38:02.783 | <p>The interior girder moment formula for one lane loaded for the AASHTO LRFD method is:</p>
<p>$$\begin{align}
mg^{SI}_{moment}&=\left(1.75+\frac{S}{3.6}\right)\left(\frac{1}{L}\right)^{0.35}\left(\frac{1}{N_c}\right)^{0.45} \\
&= \left(1.75+\frac{13}{3.6}\right)\left(\frac{1}{100}\right)^{0.35}\left(\frac{1}... | |civil-engineering|bridges|aashto| | <p>The live load distribution formulas in the AASHTO LRFD Bridge Design Specifications cannot be derived. As I understand it, they are based on calibration to extensive finite element modeling.</p>
<p><a href="http://www.trb.org/Main/Public/Blurbs/159050.aspx">This is probably the NCHRP report you're looking for.</a><... | 6788 | Derivation of the AASHTO formula of interior girder moment |
2016-01-05T09:11:59.517 | <p>During the '80s and the '90s, a lot of media cases were made of thermoformed PVC. I believe this trend was created by Disney and Blackbourn with their VHS cases. Then with DVDs, industrial standards for media casing have changed in favor of injection moulded PP.</p>
<p>For example, the latest Neo Geo AES cases are ... | |materials|process-engineering|plastic| | <p>For injection molding this is typically done by etching or burning(EDM) a pattern onto the surfaces of the injection mold.</p>
<p>check out this PDF for more detailed information on this:
<a href="http://eschmanntextures.com/fileadmin/user_upload/flyer_neu/texturesguide_eng.pdf" rel="nofollow">http://eschmanntextur... | 6790 | How can I process plastic to give the impression of a leather finish? |
2016-01-07T05:50:11.737 | <p>I work in a lab, and I've been trying to replace a lost AC-DC power adapter. I got one recently that has the exact specs that I need, which are apparently pretty rare (15V, 400 mA). However, when I test the power adapter with a voltmeter, it's actually outputting ~22V, despite what it says on the plug. </p>
<p>Now,... | |electrical-engineering|consumer-electronics| | <p>What Russell said.</p>
<p>In addition, the reason the LED lights but the device no longer appears to work may be because the LED is just wired to indicate power, and the rest of the device is now blown out due to the much higher than specified voltage you applied to it.</p>
<p>Power LEDs are sometimes just a LED a... | 6810 | Is it possible that an electronic device "half-works" when the power adapter supplies too much voltage? |
2016-01-07T07:18:38.747 | <p>I recently bought my first lathe (A circa 50s PREMO, Australian built with tapered roller bearings) and the spindle has a little bit of wiggle parallel to the axis of the spindle. I decided to pull the spindle out to take a look at 'er, but I ran into a spot of bother with the gear that mates with the reverse tumble... | |gears| | <p>I decided that because of the lack of threads, it was more likely to be pressed on. So I whipped up a little shopmade gear puller, gave a little tug, and off it came. As it turns out, the gear and the spacer that I'd thought to be two pieces was actually one piece, and the key was under the spacer rather than the ge... | 6811 | How can I tell if a gear is pressed or threaded? |
2016-01-07T10:15:23.173 | <p>Suppose a 'D' shaped shaft with a 4 mm diameter like this type</p>
<p><a href="https://i.stack.imgur.com/nOVs5.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/nOVs5.jpg" alt="enter image description here"></a></p>
<p>is fitted inside a module 1 (plastic) gear with a round hole with the same diam... | |mechanical-engineering|gears| | <h1>Quick Answer</h1>
<ul>
<li>You can fit D shaped shaft into round hole if diameters are OK.</li>
<li>D shaft to D hole without a setscrew will be preferable to D shaft to round hole with setscrew if there is no axial movement. Best is D shaft to D hole with setscrew(s). However you can't always find D holes because... | 6812 | Using a 'D' shaped shaft with a set screw |
2016-01-07T15:28:19.507 | <p>I am trying to find a method of calculating the minimum shear area of the following rectangular thread form. It is a 4.125" square thread, 8 T.P.I., straight, right-hand thread. The thread is loaded in the axial direction, thus I would like to calculate the minimum thread shear strength.</p>
<p><a href="https://i.s... | |mechanical-engineering|threads| | <p>The area equation of the thread is PI * D * nut length * .060/(.060*.065)
PI = 3.14, D is 4.125-2*.050, nut length not given, probably 1" to 4", .060/(.060*.065) ratio of thread to machined out area</p>
| 6822 | How to find the minimum shear area of a rectangular thread |
2016-01-07T21:28:34.023 | <p>I am trying to calculate the power distribution of a planetary gear system, specifically a Wolfrom system like this one:</p>
<p><a href="https://i.stack.imgur.com/8kRDA.png" rel="noreferrer"><img src="https://i.stack.imgur.com/8kRDA.png" alt=""></a></p>
<p>In order to find the output power, I need to find the torq... | |mechanical-engineering|gears| | <p>In this answer, I'm going to use the sign convention that torques and angular velocities are positive if their direction points to the right (left would be an equally valid alternative for this answer too) using the Right Hand Rule, i.e. seen as clockwise if looking from the left hand side. Any gears spinning in the... | 6832 | Determine the sign of torques for a planetary gear system |
2016-01-09T14:55:44.470 | <p>I was studying the design of joints and came to knuckle joints. Generally compressive strength is greater than tensile strength, but <strong>considering knuckle joints compressive strength and tensile strength are considered equal</strong> (as mentioned below). What are the reasons for assuming equal strengths?</p... | |design| | <p>Assuming they're equal, it allows you to use the more commonly available tensile strength data, while also getting a conservative solution. If it turns out they're not equal, then your design will still work correctly but might not make optimal use of the materials.</p>
<p>Assuming uniaxial tensile and compressive ... | 6849 | Knuckle Joint: compressive strength equal to tensile strength |
2016-01-10T00:57:39.170 | <p>I see that POM gears are often not preferred in high torque settings - but how about 0.4Nm? Is that amount of torque too much for module 1 POM bevel gears? Say they are 16-tooth.</p>
<p>Is 0.4Nm considered moderately high torque?</p>
| |mechanical-engineering|gears| | <p>module 1 16T bevel POM (also called acetal or Delrin) gears are rated at 0.2Nm at <a href="http://www.huco.com/products.asp?p=true&cat=285" rel="nofollow">http://www.huco.com/products.asp?p=true&cat=285</a></p>
<p>The webpage also list larger module gears torque ratings.</p>
<p>0.4 Nm is considered low tor... | 6855 | Nylon gears for 0.4Nm torque |
2016-01-11T00:56:35.047 | <p>I came across this question of "can an isothermal process also be adiabatic?", and at first thought that yes, why not? If the temperature is constant and there is no heat loss to the environment, it seems perfectly possible.</p>
<p>Now, I don't have too much experience in this field, but I came across a lo... | |thermodynamics|heat-transfer| | <p><strong>No</strong></p>
<p>An <a href="https://en.wikipedia.org/wiki/Isothermal_process" rel="nofollow noreferrer">isothermal process</a> is, almost by definition, a process where the fluid beeing worked upon can keep its temperature constant by exchanging energy with an external reservor, while an adiabatic process... | 6862 | Can an isothermal process also be adiabatic? |
2016-01-11T13:53:43.720 | <p>When preparing load calculations for a slab, the quick method is to define the tributary areas of a slab for the beams/columns below. These are generally taken as lines at mid-span of the slab panels and, depending on the support conditions, at the edges at angles of 30 & 60 or 45 & 45 degrees.</p>
<p>Where... | |structural-engineering| | <p>The angles of those lines are determined by yield line theory. They are the axes of bending, should the slab decide to fail, which will require the least internal work to yield.</p>
<p><a href="https://theconstructor.org/structural-engg/yield-line-theory/6839/" rel="nofollow noreferrer">Here</a> is a very simple, w... | 6866 | Where do the tributary angles/ratios for tributary areas come from? |
2016-01-12T01:04:44.097 | <p>I'd like to design some things with bolts, fan belts, levers, motors, etc. So I'd add a bolt here, drill a hole there and maybe take it apart and rearrange. I'd like to do it in 3D and found SketchUp. </p>
<p>Can it be used to design, create and print out dimensioned components for manufacture and assembly? I'm n... | |computer-aided-design| | <p>I've used Sketchup for the last 6 years as my go-to 3D engineering program. When combined in the Pro version with Layout, it can be fully dimensioned, rendered, and turned into full scale 2D production drawings that the shop can build from. In the trial version, without the Layout program, it is only conceptual.</... | 6872 | Can Sketchup produce drawings that are adequate to manufacture components? |
2016-01-13T01:35:41.500 | <p>For a 3D printing application, I need to have a spinning disc(that I will rotate via geared stepper motors) that will wobble as little as possible. By wobble, I mean that it will only rotate around it's axis and not shift side to side. </p>
<p>The goal is to build a 3d printer that uses polar coordinates rather tha... | |mechanical-engineering|3d-printing|bearings| | <p>The bearings required will depend on the loads and rotational speeds involved. </p>
<p>In the situation you describe you will probably have a combination of axial and thrust loads ie the thrust load is the weight of the disk and axial loads come from torque on the drive shaft from the drive torque and unevenly dist... | 6888 | How to secure a rotating disc so that it has no wobble |
2016-01-14T14:05:17.647 | <p>We are designing a diagnostic electronic tool for a vibrating table.</p>
<p>In our PCB there are a gyroscope, an accelerometer and a bluetooth module.
Our PCB is attached to a vibrating table that works at 12 Hz with 10 mm peak-to-peak amplitude. It has to work for at least three years "always on".</p>
<p>When we ... | |mechanical-engineering|power-electronics| | <p>Anderson PowerPole connectors are used in high vibration critical systems to make reliable connections. At the board use a ring terminal and screw with a Nylock locknut. </p>
<p>I always solder the cables (no crimp) and use Silicone high strand count wires, the type used by radio control model battery power systems... | 6909 | How to choose an electronic connector/cable that works in a vibrating environment? |
2016-01-14T15:32:34.497 | <p>I am having hard time to fully undestand what those formula's actually mean. I know the meaning of each element:</p>
<ul>
<li>I : moment of inertia</li>
<li>H : angular momentum </li>
<li>$\alpha$: angular acceleration</li>
<li>$\omega$: angular velocity</li>
</ul>
<p>$I_{G}\alpha = \dot{\vec{H}}$</p>
<p>$I_{G} \... | |mechanical-engineering|dynamics|kinematics| | <p>============<strong>Short answer</strong>===================</p>
<p>If you are familiar and understand Newton's second law:</p>
<p><span class="math-container">$$F = m\cdot a = m\cdot \dot{v}$$</span></p>
<p>Then you should know that one way to interpret it, is that:</p>
<blockquote>
<p>the acceleration <span class=... | 6911 | How to interpete the formula: $I_{G}\alpha = \dot{\vec{H}}$? |
2016-01-15T02:13:14.547 | <p>I have a setup where I want to move a knife like blade through a body of liquid inside a container and I want to control the blade from outside the container. Apart from using magnets to move the blade, is there any way to form a dynamic seal around the blade as it moves along the container length? </p>
<p>I was th... | |mechanical-engineering|fluid-mechanics|magnets| | <p>One option is not to try to design a leak-proof seal, but instead just limit the leaks to acceptable levels and make maintenance possible.</p>
<p>My suggestion:</p>
<ol>
<li>Use rubber seals like you planned to.</li>
<li>Add a trough that will catch any leaking resin. Preferrably made of a material such as teflon ... | 6914 | How to form a seal around a sharp moving blade? |
2016-01-15T04:57:22.833 | <p>I have an application where I need two motors to drive one shaft via the use of belt drives but I need help on how to arrange such a system. The system constraints are:</p>
<ol>
<li>motor type - induction motors $(48\ \textrm{V}, 750\ \textrm{W})$</li>
<li>both motors will have pulleys of same dimensions</li>
<li>b... | |mechanical-engineering| | <p>Instead of these arrangements have 2 motors with equal qty of v belts and double the qty of v grooves on driven pulley with both motors having takeup device will work perfectly.</p>
| 6916 | Using two motors and belt drives to drive one shaft |
2016-01-15T18:24:20.900 | <p>According to this <a href="http://home.mit.bme.hu/~simon/publications/Sensys_2004_FloodingTSP.pdf" rel="nofollow">paper</a>, which deals with time synchronization in wireless networks, this kind of delay occurs, however I do not understand its explanation. The paper says the reciever (radio) has to determine the bit... | |electrical-engineering|terminology|wireless-communication|rf-electronics|digital-communication| | <p>This happens on a bit level of the receiver electronics. </p>
<p>For every byte you have to receive 8 bits. At this point in communication you only decoded the signal (eg. converted the electrical power or voltage) levels to bits. You receive bits in the buffer. </p>
<p>You are constantly filling the buffer (on a ... | 6925 | What is Byte Alignment Time in radio communication? |
2016-01-16T13:46:38.757 | <p>I have interested in walking bicycle. For the concept is just bicycle that you don't cycling pedal but stepping or striding to drive wheel</p>
<p>Which leads me to think that is it better if we use linear or ellipse motion of leg to transmit to bicycle</p>
<p>The closest mechanic I could think is piston crankshaft... | |power|pistons|bicycles| | <p>The biggest problem with a "two cylinder" crankshaft is that there is a dead spot in the torque curve whenever either "piston" is at TDC or BDC.</p>
<p>When you have your feet directly on the pedals of a conventional circular crank, you actually have the ability to apply force over greater than a 180° arc &mdas... | 6933 | Why there is no piston style pedal bicycle? |
2016-01-16T17:39:12.263 | <p>How to find out experimentally to measure the vibrational frequency of some type of spring without electronic or electrical instrument?</p>
<p>I am just wondering about the advance stage of the discovery of the theory of vibrations it became in the 19th century</p>
| |mechanical-engineering|experimental-physics| | <p>If the frequency is high enough, its sound can be compared to a tuning fork, ref <a href="https://en.wikipedia.org/wiki/Tuning_fork" rel="nofollow">https://en.wikipedia.org/wiki/Tuning_fork</a></p>
| 6935 | How to find out experimentally without electronic or electrical instrument to measure the vibrational frequency of some type of spring |
2016-01-16T18:59:40.263 | <p>How could I design a paper spool or drum that is moving at constant speed without electrical system? What mechanisms are available?</p>
<p>I know that some paper tracing system was being used in 19th century to track vibration frequency.</p>
| |mechanical-engineering|applied-mechanics| | <p>If you are trying to simulate 19th century technology, based on your other question, you could achieve this to a pretty good precision with a calibrated metronome and a skilled operator turning a crank. That could easily provide enough precision for your vibration measurement experiments.</p>
<p>Things don't need t... | 6937 | What mechanisms can be used to move a drum at constant speed without an electrical system? |
2016-01-17T15:52:00.113 | <p>What options do I have for creating a resistance to a mechanical movement apart from simple friction?</p>
<p>Assume I have a lever, which will result in either circular or linear motion. I want to be able to apply a resistance to this motion, so that the user will have to apply extra effort to move the lever in ei... | |mechanical-engineering|hydraulics| | <p>Your question immediately brings dampers into mind, but I think you might still be happier with friction. It depends on whether you want the resistance to increase with speed of movement (damper) or to remain constant (friction).</p>
<p>To keep the friction steady over the lifespan of the device, you can use a spri... | 6951 | How do I add a resistance to mechanical movement in both directions, apart from friction? |
2016-01-17T17:35:35.417 | <p>I have an issue with simulink, basically it's to do with a second order system, well two first order systems in series. As I understand it as you increase the damping factor (above 1), the system should respond slower and be more sluggish. The damping factor = (tau1+tau2)/(2root(tau1*tau2)). So, looking at this syst... | |electrical-engineering|control-engineering|chemical-engineering|process-engineering|simulink| | <p><strong>Time Constant and systems</strong></p>
<p>A second order LTI system in Laplace domain:</p>
<p><span class="math-container">$\hspace{2.5em}$</span> <span class="math-container">$H(s) = \frac{{\omega_{n}}^{2}}{s^{2}+\zeta\omega s+{\omega_{n}}^{2}}$</span></p>
<p>The solution is:</p>
<p><span class="math-contai... | 6953 | Problem with process controls/simulink? |
2016-01-18T10:30:20.017 | <p>First of all, I would like to know about the service life of a <a href="https://en.wikipedia.org/wiki/Flashback_arrestor" rel="nofollow">flashback arrestor</a>. In my laboratory, I got three flashback arrestors {WITTgas RF53N(1/4”NPT-F), Brass} from the ex-students who used those items in 2012 and already finished t... | |piping|safety|gas|valves| | <p>The <a href="http://2.wittgas.com/filepool/Datenblaetter/usa/armaturen/flashback_arrestor_rf53n_dn_nsk_nu_u_usa.pdf" rel="nofollow">manufacturer says this</a> about maintanence:</p>
<blockquote>
<ul>
<li><p>annual testing of the non-return valve, body leak tightness
and flow capacity is recommended </p></li>
... | 6964 | Service Life of a Flashback Arrestor |
2016-01-18T14:28:21.247 | <p>Lets say you have a measurement device of which you do not know the accuracy, and a reference measurement device. Both measure a variable $x$. The range of interest is $x_0<x < x_1$. How do you determine the accuracy of the unknown device in this range?</p>
<p>My course of action would be to gather values for... | |measurements|statistics|metrology| | <p>I was on a team of quality engineers (but not one of the experts), and they had a visual where they used a 2d plot where X axis was first measurement and Y was second measurement of the same observable feature.</p>
<p>They would repeat the measure/remeasure and create what they called a "sausage chart". They would... | 6969 | How do you determine the accuracy of a measurement device? |
2016-01-19T10:11:22.373 | <p>What kind of furnace is used to create alloys for aluminum die casting?</p>
<p>I have only been able to find information about how to create alloys or how to process them afterwards in the die casting process.</p>
<p>Any insight on which kind of furnace you use to create the initial alloy would be highly appreciat... | |aluminum|alloys| | <blockquote>
<p>Aluminum is a metal that can be used in die casting to make parts easily. Many die casting techniques like permanent mold casting and sand casting are used for casting aluminum. Permanent mold casting is highly repeatable and helps to decrease the spin balancing processes and secondary machining operati... | 6981 | Furnace for aluminum alloy creation |
2016-01-19T13:54:09.730 | <p>I'm working on an application in which sparks (specifically from static discharge) present a severe safety hazard. One component in question is a piece of PVC water pipe. It has been proposed to "ground" the pipe to minimize the risk of static shocks between humans and the pipe, and between other components and th... | |electrical-engineering|safety| | <p>As pointed out, non-conductive plastics can build up a charge. In certain applications industry code call for all piping in ex-hazard areas (or where the inside is an ex-hazard area!) to be conductive material, and grounded. To my knowledge,there's no conducting PVC. Hoever both PE and PP can be bought in a coductin... | 6987 | Will PVC build up an electric charge and cause a spark? |
2016-01-19T17:44:37.480 | <p>I am trying to solve the following problem. If someone can just point me in the right direction it would be appreciated. I don't have the textbook and online resources are proving to be absolutely worthless.</p>
<blockquote>
<p>A piston-cylinder device containing a fluid is fitted with a paddle
wheel stirring ... | |thermodynamics| | <p>The work that the system does on the atmosphere by pushing the piston outward is just $$W=\int{PdV}$$
From your problem statement, it looks like you have a constant pressure of 101 kPa and a change in volume of $\Delta V=\frac{\pi}{4}(0.59\ \mathrm{m})^2(0.7\ \mathrm{m})=0.19\ \mathrm{m^3}$. The work done by the sy... | 6992 | Find net work on the system |
2016-01-20T16:47:56.673 | <p>While I've designed tons of plastics for corrosive service, the fasteners to hold the plastics together are inevitably metallic. There have been a lot of ways to protect them from rusting (due to exposure to things like <em>33% HCl, 50% H2SO4, 50% NaOH, and 15% NaOCl</em>, for example) that I've seen, but here is a... | |mechanical-engineering|materials|chemical-engineering|corrosion|fasteners| | <p>This link specifies that Alloy 20, specifically CARPENTER® alloy 20Cb-3, has an amazing resistance to chemicals containing chlorides and sulfuric, phosphoric, and nitric acids. It also resists pitting, crevice corrosion, SCC, and intergranular attack. It can be used for pickling tanks, gas scrubbers, piping, heat ex... | 7015 | How does Alloy 20 compare with Ti 6-4, C-276 and 316 stainless for corrosive service? |
2016-01-20T22:11:39.683 | <p>I am practicing engineering drafting and sometimes I am near on finishing my work but suddenly I make a mistake. Is it possible to remove the ink? If yes, how? Where can I buy such tools? I am using a <a href="http://rads.stackoverflow.com/amzn/click/B001U3RCGQ" rel="nofollow">Staedtler's Mars Matic 0.5mm</a>.</p>
| |drafting| | <p>Yes, it can be removed but it is a delicate task requiring some experience...I first did this over 50 years ago. You should be drawing on some heavy velum that can withstand the erasing. You will need an erasing shield and electric eraser with the coarse dark grey eraser to gently sand a layer of paper off with th... | 7019 | Is it possible to remove Staedtler ink from a paper? |
2016-01-20T22:25:29.150 | <p>I'm curious about pumping a fluid through two different tubes (coming from two different pumps) into a Y connector. The third side of the connector runs into a collector without any resistance (other than that of the length of tubing).</p>
<ol>
<li><p>If each pump runs at a different rate, say one is twice as stron... | |fluid-mechanics|pumps| | <h2>Pumps are complicated</h2>
<p>Many questions regarding fluid machinery start with these two assumptions:</p>
<ol>
<li>A pump or gravity is needed to make the fluid go faster</li>
<li>High pressure means faster flow</li>
</ol>
<p>All of these are correct in principle, but none of them are accurate. The first is ina... | 7021 | How do pumped flows combine in a Y connector? |
2016-01-21T00:01:33.367 | <p>I accidentally dropped my <a href="http://rads.stackoverflow.com/amzn/click/B001U3RCGQ" rel="nofollow">Mars Matic 0.5mm</a> and noticed that maybe I broke the needle. I was having a hard time writing with it so I tried to clean it, and while cleaning I accidentally bent the needle part. After all the trouble that I ... | |drafting| | <p>You can buy a replacement nib. The following picture is from eBay. I just wanted a picture to show you that it is possible to remove the existing nib and replace it. </p>
<p>I would suggest you make enquires with pen supplier, or search the internet for a replacement nib.</p>
<p><a href="https://i.stack.imgur.com/... | 7023 | How do I fix a technical drawing pen with a bent needle? |
2016-01-21T17:45:38.973 | <p>I am interesting in replacing a solid strut with tubing, but I do not want to destructively test the strut to determine its yield point. I do not want to make assumptions about the yield point based on material, because heat treatment and other factors can affect the yield point.</p>
<p>Can I cantilever suspend the... | |mechanical-engineering|structural-engineering|stresses| | <p>The other answers say that this isn't possible in the way that you want to do it, but they don't provide the equations that show why.</p>
<h3>Deflection of a Cantilever</h3>
<p>The <a href="https://en.wikipedia.org/wiki/Deflection_%28engineering%29#End-loaded_cantilever_beams" rel="nofollow">equation</a> for the d... | 7038 | Can the strength of a strut be determined by deflections? |
2016-01-22T00:51:53.827 | <p>I'm interested in learning what I might call "advanced statics" but am not sure what concepts this would include in engineering parlance.</p>
<p>Would it actually be called "matrix structural analysis"?</p>
| |civil-engineering|statics| | <p>The field of statics is based on analyzing finitely many (solid) members and discrete forces acting in equilibrium. It is a purely algebraic method of analysis (no calculus is necessary). To move to topics more advanced than this while still assuming equilibrium, you have to start eroding away at the "discreteness... | 7043 | What engineering topic builds upon the concepts of basic statics? |
2016-01-23T20:34:36.600 | <p>I'm well aware of Helmut Hoeltzer's "Mischgerat" analog computer, and I read that it not only served as a kind of "fly by wire" computer on board of the missile, but also as a simulator on the ground that calculated V2 trajectories.</p>
<p>But, I didn't find any clue about how it did it - how Hoeltzer calculated o... | |electrical-engineering| | <p>My pardons for addressing this question six years on.</p>
<p>The ballistic trajectory for a particular target was calculated by hand by a computing group within the V2/A4 project. If you've seen the movie "Hidden Figures", just replace African American women with Nordic men.</p>
<p>Based on these calculati... | 7059 | How was the trajectory of the V2 ballistic missile (during boost phase) calculated? |
2016-01-23T21:36:50.767 | <p>recently I bought 3 solar panels rated at 5V 200 mA each. I want to use them to charge a 5V battery bank to charge a phone. Thinking about the proper way to put them, I thought i can connect all in parallel to get maximum current, but realized that if the sun light was a little weak it will no generate full 5v thus ... | |electrical-engineering|photovoltaics|solar-energy| | <p>A panel "rated" at 5V 200mA will normally put out 5V 200mA at it's maximum power point, in full sunlight.</p>
<p>In lower light, it will put out less power.</p>
<p>But the voltage depends on the battery, not on the light. When you have more light, you have more current, and the battery charges faster.</p>... | 7060 | Did I wire these solar panels correctly? |
2016-01-24T17:16:11.273 | <p>It sounds logical untill I tried some thought experiments. So I must be doing something wrong. Or I am missing a fundamental aspect.</p>
<p>What I thought of was: </p>
<p>-lets say you have an orthogonal parallelepiped which is pulled in tension by a stress-strain test. (in the long axis or z-direction).</p>
<ul>... | |mechanical-engineering|materials|metallurgy| | <p>First poisons ratio for isotropic materials applies equally between each pair of dimensions. That means that if the axial length is stretched $1\%$ both of the lateral dimensions would reduce by $\nu 1\%$. I don't know where you're getting the 0.25 number from.</p>
<p>Second, this approximation only works when the ... | 7066 | Why is the Poisson's ratio for isotropic 1/4 and the maximum value 1/2 (when there is no net volume change)? |
2016-01-25T05:59:33.450 | <p>I would like to create beam models having various cross sections on ProE tool.</p>
<p>Can I create a beam model like below by only extrusion?</p>
<p><a href="https://i.stack.imgur.com/NEwmF.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/NEwmF.png" alt="enter image description here"></a></p>
<p... | |mechanical-engineering|structural-engineering|modeling| | <p>If pro-e is anything like solidworks then you need to draw a 2D version of the extrusion pattern. In your case, one large square with the 4 smaller squares within it. </p>
<p>Then select the area you wish to extrude and extrude it. </p>
<p>I recommend looking up some basic tutorials for ProE as I'm sure this would... | 7071 | beam cross section modeling by extrusion on proe |
2016-01-25T06:25:35.537 | <p>I've heard that materials that need to slide against each other should be of different materials. Why is that?</p>
| |materials|friction| | <p>For a sleeve bushing, you want a soft slippery material with sufficient yield strength to withstand any deformation of the hole surface during operation. For the shaft, you want a hard smooth material with sufficent yield strength to withstand being deformed/bent in order to ensure that the surfaces of the shaft spi... | 7072 | Why use bushings of different material than what they contact? |
2016-01-25T14:32:16.590 | <h1>Background</h1>
<p>In the world of <a href="https://www.youtube.com/watch?v=kklBFX62F8U" rel="noreferrer" title="2012 Olympics - Elite Men's Main Event">bicycle motocross, also known as BMX racing</a>, gearing is a hotly-debated topic.</p>
<p>Since the bikes are all single-speed, gear ratio is a fixed number ... | |mechanical-engineering|gears|measurements| | <blockquote>
<p>A "44.2 tooth" gear still can only push 44 links of chain per revolution, which pushes a 16 tooth cog around 2.75 times. There's no getting around that.</p>
</blockquote>
<p>I think that is the question that has everyone's head smoking. So I made a visualization.</p>
<p>Here we have small gear with ... | 7080 | Is it possible for a bicycle chainwheel to have a fractional number of teeth? |
2016-01-26T13:47:00.400 | <p>Does the material with which I make the mold for carbon fiber parts affect the finish the part will get? If it does, I would like to understand how a given material may affect the finish.</p>
<p>Another thing that is confusing me is the exact definition of <code>finish</code>. Does it refer only to the smoothness o... | |materials|composite| | <p>The finish of the mould will certainly have an effect on the finished part. How much of an effect depends on the exact process, for example if you use a gel coat then that will pick up the surface texture of the mould pretty closely. Without a gelcoat the ratio of fibre to resin will determine how much the weave of ... | 7101 | Impact of mold material in carbon fiber part finish |
2016-01-26T20:39:10.750 | <p>I have heard that error correcting codes are used to store and retrieve data in hard-drives but are they used in the processors in common laptops? Is the information encoded before it is processed?</p>
| |electrical-engineering| | <p>Error correction means extra bits are stored along with the data. Think of it as a advanced checksum. A checksum can detect when the data is corrupt. A error correcting "checksum" allows recovering some limited numbers of errors, usually a single bit error in the chunk of data being protected by the checksum.</p>... | 7107 | Error correcting codes in processors |
2016-01-27T02:25:29.153 | <p>When a fluid, like air, is moving at some velocity and "hits" or collides with a surface: </p>
<ul>
<li>If the surface is at an angle, the fluid will tend to be propelled in a similar direction (anything else?). </li>
<li>If the surface is perpendicular, the fluid will tend to kind of splash out in all directions... | |fluid-mechanics| | <p>When the velocity of the air is less than about Mach 0.3, there is hardly any change in pressure or density as it impacts the surface. For flows greater than $M=0.3$, you can calculate the stagnation pressure, density, and temperature with the following equations:</p>
<p>$$
\frac{p_0}{p}=\left( 1+ \frac{\gamma - 1... | 7111 | Air colliding with surface, local effects? |
2016-01-27T16:36:41.783 | <p>Let's say I have a pump pushing fluid through a 250 ft pipe, 1.5'' diameter, at a rate of 20 gallons per minute. I would like to calculate the delta in energy required to pump this fluid with and without a restriction at the end of the 250 ft line. The restriction results in 0.01 psi pressure drop.</p>
<p>What equa... | |energy| | <p>The pump power equation can be used to calculate the energy required in both scenarios. Convert the additional $\Delta P$ to head, then calculate the difference in required hydraulic pump power. Both of these equations are on Engineering Toolbox. </p>
<p><a href="http://www.engineeringtoolbox.com/pump-head-pressure... | 7119 | How do I calculate the additional energy required to pump fluid through a restriction? |
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