texts: Does there exist a device which can construct a perfect parabola?

texts: For instance, a compass can create a perfect circle, and two pins can be used to create an ellipse. Devices such as Spirographs can also be used to draw all sorts of continuous parametric curves. Is it then possible to construct other (simple) devices that may continuously draw parabolas? (Or hyperbolas, for that matter) If not, why not?


texts:
I have a copper tube that I'm heating (quite a lot) with a  torch, I have to connect a PVC pipe in the entrance of the copper and one in the exit (so water can flow through the copper pipe). The only problem is that the copper tube is too hot, so the PVC pipe melts, any ideas on how to connect them? Maybe a ceramic or fiberglass joint?
Thanks


texts: I need textbooks for studying clinching process (an alternative to spot welding in some applications) for my project. A text which covers basic or an indepth working process about different tools or calculating forces is highly recommended.


texts: Strength of human hand compared to robot

texts:
I was working on designing some robotic grippers and I find I have to make a pretty large device to have anywhere near the same power as the human hand.

Is this other engineer's experience? Is the human hand, cubic centimeter for cubic centimeter just really strong compared to a machine?

I guess this translates down to how ants can pick up "boulders".


texts: Can a level shifter convert power from 3.3v to 5v and then back to 3.3v?

texts:
I need a digital output from a raspberry to power a stepper driver that takes 5v as input.
After that, the output from the stepper driver must be converted back to 3.3V because a Pi can't handle 5v on the GND-pins.
I bought the following level shifter: https://www.spikenzielabs.com/Catalog/adafruit/breakouts/4-channel-i2c-safe-bi-directional-logic-level-converter-bss138
But since it is I2C-safe, im not sure if it will allow being turned into 5V because the "master" only handles 3.3V?


texts:
How does a single pivot side-pull caliper bicycle brake work? The brake cable only pulls on one of the arms, so what is causing the force on the other arm? I understand that it is a normal force due to the cable housing, but why is this force developed?

EDIT

I'll elaborate on my questions a bit. Let $A$ be the point where the cable is attached, $B$ be the point where the housing pushes on the other arm, $P$ be the point of pivot, $C$ be the point where the first arm touches the rim and $D$ be the point where the second arm touches the rim. $APC$ is then the arm pulled on by the cable and $BPD$ is the arm potentially pushed by the housing.

Let's say the cable pulls at $A$ with some tension force $T$. A normal force $N$ from the wheel must then push on $C$, in order for the torque with respect to $P$ to be zero. We have $N = (|AP|_x/|CP|_yS) $, if $x$ and $y$ are in the horizontal and vertical direction respectively, and $T$ is vertical and $N$ horizontal.

The force $N$ gives a lateral force on the rim and a torque on the wheel. They could be balanced by a normal force of the same magnitude at the other brakepad. By symmetry, $B$ would then have to be pushed by a force of magnitude $T$.

But couldn't they also be balanced at the hub? Does it have to do with the construction of the wheel, i.e. because it's spoked? If the wheel were in the form of a solid cylinder (which would of course be very impractical!), would the situation be different?

image source wikipedia


texts: Engage and disengage DC motor from free-spinning reel

texts:
So i want to have a reel (~4cm diameter) that will pull a ~80cm string with a torque of ~8kg-cm (edit: thanks for the clarification). To pull I want to use a gear motor. E.g. 12V DC motor like this:
The problem is that I want to be able to  easily unwind the string with my hands when the motor is not pulling in the string. So I would need some kind of possibility to disengage the motor. The problem is something like a sprag clutch (or one-way bearing) would not work as I pull the string in the opposite direction of the way the motor would spin. I found something like the "freecoaster" designs for bikes, but I don't know how I could build this cheap and easy especially given the small form factor (and limited tooling: mostly a 3d-printer, and normal tools). My other idea would be to try and create some kind of clutch that i would engage using a servo motor, by sliding a clutch like this on the axle using a servo motor. But I am not sure how well that would work or if there is a better alternative.
So what would be your suggestion to create a system that allows me to engage the motor to a free spinning spool when I need it to wind the string.
This motor will only be used to pull in the string once every month or so, so it doesn't need to be able to withstand thousands of cycles. But when it is used, it should work relatively reliable. I also found this question that seems to try and solve a similar problem. But I don't know how well that would work for my usecase. Thank you for your help!


texts: Maximum amps from a switching voltage regulator

texts:
Looking at a part like this
LM2596

It is rated for 3Amps with a voltage range from 3.3-12 volts.

Does that mean that this voltage regulator will only output a maximum of 3amps?


texts: Analysis of Machine Frames With Cut Outs

texts:
I have a structure that is used to support two shafts which are carrying relatively high loads. It is composed of two columns and a "shaft supporting block" in the centre (almost acting as a beam). The block is just a rectangular block of steel with two through holes in the centre. I want to analyse the stresses in the columns and block in order to verify if they are suitable and do not yield or fail. I need a relatively accurate solution and so I want to avoid approximate methods. The loads act at the bottom of each hole, in the centre of the thickness and therefore torsion is negligible or can be considered as 0.

My first thought was to idealise the shaft supporting block as a beam and apply the moment distribution method. However, due to the two holes for the shafts to pass through, the block has a varying moment of inertia and therefore cannot (at least in my understanding,) be solved using moment distribution.

I also thought of trying the column analogy method however, did not work due to the same above reason.

I do not have access to use finite element analysis (computer) and want to use standard structural analysis methods (e.g. moment distribution and not stiffness method). I have attached a rough sketch image of the real structure and idealised system for reference.


texts:
I am new to fluid mechanics and am trying to understand the fluid mechanics of a simple valve.

Let's assume we have a simple tube, which is supplied with a constant stream of liquid using a pump.
At the end of the tube is a valve, which closes periodically.
What kind of changes, would I except in the tube due to the closing of the valve?

In my naive understanding, I would assume, that the velocity should approach zero (since there is no way, where the fluid could go), however the pressure should stay constant - there is no fluid flow, but the pump provides still constant pressure.

Is this understanding correct? Do you maybe have some papers / literature / videos, where this is explained in more (maybe mathematical) detail?

Thank you very much!!


texts:
Part of my project is to compare linear elements and quadratic elements with a Quad mesh within Ansys workbench - static structural. The button that my classmates have to change between element orders is missing on my Ansys. Has anyone had ths issue and knows a solution or knows something I need to check to get the button to show? the option should appear under relevance in the Defualts section of the mesh.

Kind regards,
George Packham


texts: Solar powered kettle - how much power for 1/2 litre

texts:
I want to create a solar powered kettle but first, I need to know how much power will be required.

This means, I think, I'll need to know how much water I want to bring up to a certain temperature.

I'm trying to understand how to work this out, and I'm frankly stumped.

Is it possible to work this out, if I knew I wanted to bring 0.5litres to 60 degress C, how much power would I need to achieve this within 30 minutes?

My end goal here is to find a suitable solar panel powerful enough.


texts: Heat Transfer From Resistance Element to Metal Component

texts:
I have a device that produces heat via Nichrome coils. I want to heat another small piece of metal (in this case stainless steel) with those Nichrome coils. I need to reach 175 degrees C, and so far I haven't found a readily available thermal adhesive that will work in my temperature range.

Is there a high temperature thermal adhesive available to consumers that I could use? Any suggestions on another way to effectively transfer the heat from the coils to my small metal component?

Thanks in advance for your help!


texts:
I would like to clean and change de belt in a Schaublin 70 Lathe, but when removing the main shaft, I noticed this weird bearings:

How would I remove it what should I take care about?


texts: What is the process of transferring an engineering license from the United States to Germany?

texts: The United States have different rules about exactly how one obtains an engineering license, but the general process is the FE exam, a few years of work, and the PE exam. Suppose one then wishes to practice engineering in Germany. What are the legal requirements for doing so?


texts: How can you calculate the specific fan power of a fictitious HVAC system?

texts:
I am working on a concept involving an HVAC system drawing air in from outside.
Known information: Air flow rate (calculated), change in pressure accross fan (given) and total efficiency (assumed). No other information is available and would have to be assumed or neglected.
P_el = Air flow rate * change in pressure
I worked out that with an air flow rate of 5000 l/h and delta p of 100 Pa, I would have a P_el of 0.139W. With an efficiency of 60%, that's 0.232 W.
My system operates for 1600 h/a. How do you report the result? I.e. do I have to multiply the 0.232W by 1600 h? Is the result actually correct? My professor gave me the pressure drop value of 100 Pa, which seems very low to me.
This is definitely not my area of expertise. Many thanks in advance!


texts: What's the difference between Fuzzy PI, PD and PID controllers?

texts:
I am investigating fuzzy control and I am a little confused, I have come across 3 models and I can't quite fathom out what is going on.

In this PD+I controller, I can see the error signal being scaled by Kp and the derivative of the error being scaled by Kd and being fed into the fuzzy controller. I can the integral of the error being scaled by Ki and being fed into the summing junction along with the controller output scaled by Kh.

In this PID controller, I can see the error is fed into GE and GE4 which are the proportional scaling factors, Discrete Derivative Filter 1 and 2 which are the derivatives of the error which are being scaled by GCE and GCE1 respectively and are then fed into their respective fuzzy controller. This is where it becomes confusing, the output of Fuzzy logic controller 1 is scaled by GCU and then integrated which would seem to be the exact same as the PD+I controller in figure 1, it seems that controller 1 is a PID controller 2 is a PD controller?

Finally, this controller is the 1 that really bamboozled me, I can see the error e(t) being scaled by Ki (shouldn't this be Kp?) and the derivative being scaled by Kp (shouldn't this be Kd?) and the output from the controller is integrated with no scaling factor, apart from the absence of the scaling factor before the integral, this looks the same as the PID.
I suspect that my understanding of Fuzzy controllers are not correct so I would be very appreciative if someone could shed some light on this. Thanks in advance.


texts: How to determine the lateral earth pressure in a double-walled cofferdam?

texts:
The design of a retaining wall commonly involves determining the lateral earth pressure using either Rankine theory or Coulomb theory. Both theories involve mobilising the shear resistance of a triangular wedge of soil extending for a considerable distance away from the base of the wall.

In the case of a double-walled cofferdam, such as the one in the picture below, the short distance between the two walls would prevent such failure wedge from extending all the way down to the bottom. In which case, how does one go about determining the earth pressure from the sand fill material in between the two walls?


texts: Solidworks 2014 - Convert a complex assembly into a single "inert" geometry file and import it

texts:
I have a large and unwieldy Solidworks assembly and I would like to save it as an "inert" geometry file such as an STL or STEP format.  Then I want to import this into another project assembly and move it into a specific location.

It seems that I am unable to move the STL version from its default insertion point in the new project.  I have tried opening the STL file and saving it as a SLDPRT file and bringing this into the assembly but I am unable to move that either.

The reason I want to do this is so that there are no dependency links between one project and the other, in order to avoid any possibility of design corruption while I'm experimenting with the new assembly.

In a nutshell, how can I import and position an inert STL (or STEP or whatever) into an existing SLDASM file and be able to move it around?


texts: What is the physical meaning of Cumulative Passing% in Grain Size distribution?

texts:
When preforming a grain size distribution on a sample of Soil using Mechanical Sieves (e.g. Sieve #4 and sieve #10 and sieve #40) one of the necessary calculation need for drawing the particle size distribution curve is the Cumulative Passing percentage of Soil Particles (aka Percent Finer).

The formulas are pretty straight forward, but what is the physical meaning of Percent Finer? What does it imply ?

Here is a reference table:


texts: Beam stiffness matrix with sliding end release in arbitrary angle

texts:
I know how to get the stiffness matrix of a beam with any type of end releases (hinges and rollers) by applying Guyan reduction (static condensation) to the beam stiffness matrix in local axes. However, by doing this, the rollers sliding direction is parallel to the beam local axes.

First question: Would I get the rollers parallel to the global axes if I apply the Guyan reduction to the beam stiffness matrix expressed in global (rather than local) axes?

Second question: What if I wish to get a roller in a direction which is not parallel to neither local nor global axes? Is it just a matter of transforming the matrix in two steps? I mean: first step, apply a transformation matrix from local axes to roller axes. Apply Guyan reduction there. Then apply a second transformation matrix from roller axes to global axes, and you have the beam stiffness matrix with the desired end release, ready for assembly because it's in global axes.

Would it be as easy as that? Is there any book covering this? (I found end releases explained in several books, but only in local axes).


texts: Exponential stability under a global coordinate transformation

texts:
Consider a system of the form
\begin{equation}
\Sigma\colon\ \dot{x}=f(x),
\end{equation}
where $x\in \mathbb{R}^n$ and $f\colon \mathbb{R}^n\to \mathbb{R}^n$ is a sufficiently smooth function vanishing at the origin. Assume that $\Sigma$ has a globally exponentially stable equilibrium at $x=0$. Now apply a global coordinate transformation
\begin{equation}
z=T(x),
\end{equation}
where $T\colon \mathbb{R}^n\to \mathbb{R}^n$, $T(0)=0$ is a global $\mathcal{C}^1$ diffeomorphism. Accordingly, we obtain the transformed system
\begin{equation}
\Sigma^\prime \colon\ \dot{z}=g(z):=\frac{\partial T(x)}{\partial x}f(x)\bigg|_{x=T^{-1}(z)}.
\end{equation}
Question: Is $\Sigma^\prime$ globally exponentially stable at $z=0$?


texts:
I think I'm missing something important here.

For a fluid with a velocity $u$ in a pipe with cross section area $S$, the volumetric flow rate is equal to:

$$Q_v = uS$$

If we now consider vectors, the volumetric flow rate is:

$$ Qv = \int \vec{u} ·\vec{n} dS$$

Where $\vec{n}$ is the normal vector to the cross sectional area. For example putting numbers, considering only one axis $x$:

$$ \vec{u} = 10 \vec{i} \qquad \vec{n} = \vec{i} \qquad S = 10 \\ Qv = 100$$

However from the divergence theorem we know that:

$$ \int \vec{u} · \vec{n} dS = \int \nabla · \vec{u} dV$$

And for incompressible fluids $\nabla · \vec{u} = 0$, so it would give $Q_v = 0$.

Obviously i'm doing something very wrong here, but I cannot see what. Am I considering something wrong in these equations? Is the normal vector in the divergence theorem refering to another surface in this case, or to both surfaces, these being, both $\vec{n} = \vec{i}$ and $\vec{n} = -\vec{i}$?


texts: which kinds of lubricant / grease can attack carbon fibre components and which kinds cause no harm or damage?

texts: It's easy to find many non-expert opinions about the dangers of using grease on carbon fibre components. Which kinds of lubricant cause no harm to carbon components, and which, if any, can damage them?


texts:
I just don't get the concept of Boolean Geometry... Can you help me understand how to solve these homework problems?
Thanks!


texts: Can an event on the critical path have non zero slack time in critical path method?


texts:
How can the vertical wind direction be measured?

For a project I have to design a wind turbine and I would like the blades to make slight adjustments based on the wind direction in order to achieve the most efficient energy conversion. Whilst I can use a wind vane to get the direction of the wind on a horizontal plane; I have been unable to find a method for finding the direction of the wind on a vertical plane.

I would appreciate any help.


texts: Sound insulation, absorption and diffusion. Can they be part of the same process when wanting to both soundproof and acoustically treat a room?

texts:
I understand that insulation, absorption and diffusion in acoustics are different concepts. Notwithstanding, would it be correct to assume they may be part of the same process when all are used to achieve 'sound proofing' and 'acoustic treatment' in a certain scenario?

To put it differently, is it correct to say that by treating the sound within a room (with proper absorption and diffusion techniques) we can limit (up to a certain extent) the pressure of certain sound waves that will exit the room?

More specifically, I would think that by treating a room with high absorption coefficients, a certain amount of sound energy will be transformed into heat energy (for instance using mineral wool). Shouldn't this mean that less energy will 'get out' of the room? Also, shouldn't this mean that we could potentially plan a room's construction with both sound proofing and acoustic treatment at the same time, without them being completely separate activities at the design stage?

Therefore, in the aforementioned example could we not say sound insulation, diffusion and absorption may be part of the same process instead of being treated separately. When a room's structure (both inner and outer) is defined can't we limit sound transmission to a certain degree by adding non parallel walls for instance, thus decreasing vibrations?


texts: Why does decrease in dislocation density result in higher ductility?

texts: Why does a decrease in dislocation density result in decrease in yield strength and increase in ductility?A slightly detailed explanation is what I am looking forward to.


texts:
I'm looking for a name of a part. It looks like a cable inside another cable. The idea is that you can just pull on the inside cable and get the force at the other end. You can just attach the outside cable somewhere, and don't have to bother about pulleys and such.

Does this exists, and what is it called?


texts: How can double I-section walers be spliced to ensure effective moment transfer?

texts:
I notice that quite a number of deep excavation projects adopt double I-section walers to form a box beam since standard rectangular hollow sections don't come with such large sizes. The I-sections are usually factory butt-welded together at the flanges.

How are such members spliced together? Unlike a single I-section, the inner flanges of the double I-section would not be accessible. There would also be problem connecting the webs due to the same accessibility issue.

From the pictures I found on the internet, it isn't clear how this can be done to achieve effective moment transfer.


texts: Tiled/block pavement used to pave high traffic roadway?

texts:
We're normally paving the high-traffic road with concrete or asphalt. While for sidewalk/garden, we use pave block/tiles (either concrete or else)
Common reason is because pave block/tiles doesn't seems comfortable for high speed vehicle, because it tend to have up-and-down structure, cannot be as plain and smooth as pouring asphalt on it.
While this is true, instead of making pave block/tiles as flat as possible, why do we choose to keep using common surfacing method? Is there any  other reason?

Considering from what i understand, in compare to common surfacing method, block/tiles have either environmental, aesthetical or mechanical advantage over it


texts: Optical methods for reaction engineering

texts: What optical methods can be used to measure the concentration of reacting gases in a packed bed reactor during an exothermic and fast reaction? I need to monitor and measure the local concentration of gases used to produce methane (i.e. methane, carbon monoxide, carbon dioxide, water, and hydrogen) along the length of the reactor bed in order to be able to clarify the kinetics of this reaction.


texts: Knowing how many times the rear wheels have rotated, and the angle of the front wheels at every time interval, how do I find the location of a car?

texts:
I'm making a robot for the Sparkfun AVC. I was curious if I could use only the knowledge about

How the car is being steered at every time interval,
How many times the wheels have rotated,

to get a general sense of where the car is. I would use computer vision to avoid immediate dangers.

The biggest problem is any slipping causing false counts.


texts: What is the most efficient way to remove the cardboard center piece from a roll of paper?

texts:
For a temporary job I'm working, one of the tasks we are sometimes required to do is to unroll these giant spindells of paper (think rolls of toilet paper the size of a trash bin except the paper is tough) and pack the paper into a box for recycling. The goal, really is to remove the cardboard center piece. The way they've been doing it is to cut through it with a knife. But this is tiring and takes a while.

Is there a more efficient way of doing this? I was thinking about maybe cutting in the middle to try and remove the center piece but it's just in there so tight.


texts: For my rube golberg project I have to twist a lightbulb in and have it turn on. I have seen different videos on how they do it but they never explain it and most of the videos are blurry. We can't have the lightbulb already in partway to screw it in.   Does anyone know what the best way to have something screw the lightbulb in and a great power source for it to turn on?


texts: Difference between a "Pulley" and a "Wheel and axle"

texts:
A "Pulley" and a "Wheel and axle" seem much similar to each other. What is their actual difference and what are their precise definitions?

My understanding of the two terms is much relied on the context of Simple machines. The wikipedia articles of the two terms provide a definition which makes them seem very similar.  But since simple machines are considered (by ancient greeks) as six distinct different basic machines then they must have an important difference.

I'm not sure, but maybe modern treament of mechanical machines in terms of "Linkage synthesis" could give a better explanation. If it's possible, please explain the differences and the definitions both in the context of "Simple machines" and "Linkage synthesis" methods.


texts:
In qualifying the results of a Finite Element (FE) beam  model, I'm realizing that I dont understand FE beam elements as well as I should.

Is there a procedure to determine what order beam element is required?

Specifically, for the 2D tip-loaded cantilever beam shown below:

The analytical solution given by Euler-Bernoulli Beam Theory is used to qualify my FE results, where:

  $y(x) = -\frac{F}{6EI_{zz}}(3Lx^{2}-x^{3}) \; \rightarrow \; \therefore y(x=L) = -\frac{FL^{3}}{3EI_{zz}}$
  $\sigma_{xx} = \pm \frac{M(x)c}{I_{zz}}$
  $\tau_{xy} = \frac{F}{2I_{zz}}(\frac{h^{2}}{2I_{zz}}-y^{2}) \; \rightarrow \; \therefore \tau_{xy}(y) = \frac{3}{2}\frac{V}{A}$

I am testing Beam 188 elements in ANSYS using Linear (2 Node) and Quadratic (3 Node) beam elements.  For both linear and quadratic elements, I increment the number of elements required until the FE model convergences with the analytical (Euler-Bernoulli) solution.

For the single element, linear Beam 188 solution:

  The maximum displacement is ~7% less than the analytic solution!
  The maximum bending stress is 50% less than the analytic solution!

I thought that the stiffness matrix for a linear beam element was formulated from the differential beam equations, making it an exact solution for a beam subjected to point loads.  As I understand it, higher order elements are required for distributed loading,curved beams, etc.

I understand the stress gradient cannot be captured without additional elements, but is it possible to calculate stress along the beam from the beam equations and interpolated (shape function) values? Still, are the nodal displacements accurate for a single element?

Are linear beam element solutions ever exact and when are they used in practice?


texts:
I have a small device emitting up to ~90 Watts thermal power over a surface of 2x2 square centimeters. What is the best way (both commercially and DiY) for keeping the temperature of the device constant, maybe +- 1 degree at room temperature?

I have a thermoelectric element I could use, which has a surface area of 18x10 square centimeters for the cold plate. It is capable of removing up to ~75 Watts thermal power at 0 degrees temperature difference. How efficient will it be when I put the electric device on top of it? How much will the size difference effect the efficiency of the TEC? I know that it is rated for lower thermal powers, but it can be used as intermediary solution while keeping the device at lower powers.

The device itself is a solid state laser diode, which means that even small changes in the temperature (i.e. degrees) will shift the wavelength, something I do not want (I prefer having it at ~20 degrees). The diode can emit up to 90 Watts, depending on how much output power I request, but the upper limit is 90 Watts.


texts: In the diagram bottom of the image uploaded , it's clear that width of the section after and before the cut are the same , right , which is 25x3=75mm , why the author stated that the width of section after cut become 25mm ? I cant understand


texts: What optics system can create an image both smaller and further away from the system than the source object?

texts:
My system comprises of: a light source, a set of lenses, a projected image of the light source.
I want the projected image to be both further away from the lenses and smaller than the source. Which is in contradiction with the optic law that :
source size / source to lens distance= image size/ image to lens distance.

Do you know optical tools that could help me ?


texts: How can I calculate the amount of heat my copper water trap can dissipate?

texts:
My small (1.5hp) air compressor is connected to a water trap made of 8mm copper of about 4 metres length. The idea is that you push the compressed air through the piping which cools it, condensing the water out (which you drain away) and thus sending dry air to your air tools.

I know the system works, but i would like to understand the maths behind it. I started trying to work it out with help of the below graph from engineeringtoolbox.com but didn't know where to go next.

How can I mathematically determine the temperature drop of the air in the piping? We can assume an average ambient temperature of 25 degrees Celcius with air coming out of the compressor at 100 degrees Celcius.


texts: Resolution of MRI can be improved if FOV is reduced keeping other factors constant, but this reduces voxel volume,  which in turn reduces SNR. How much SNR is enough for good imaging?


texts: Conceptual question about rotational and translational kinetic energy

texts:
My real life problem is to calculate initial translational and angular velocities of a vehicle in a loss of control to a stop. (The vehicle will translate and rotate about it's center of mass.)
Initial strategy is to use energy-work theorem, therefore:
$K = W$
where $K$ is the initial kinetic energy and $W$ is the work due to friction (F) between the tires and the road surface (assume that's the only external force at play), therefore:
$\frac 1 2 mv^2 + \frac 1 2 I\omega^2 = \int F\,ds + \int \tau\,d\theta$
Assume I know how to calculete the RHS of the equation. The problem with this, is that i have two variables($v$ and $\omega$) with only one equation.
The question is: Is it valid to write two different equations, one for rotation and the othe for translation, as following?
$\frac 1 2 mv^2 = \int F\,ds$
$\frac 1 2 I\omega^2 =\int \tau\,d\theta$
This way i would be able to solve for $v$ and $\omega$, but I am not so sure i can do it without violating some underliying principle..


texts: Information regarding plastic hinges that can hold the position

texts:
I am trying to find some information regarding the design of plastic hinges that can move freely but also hold a position in any degree, like in this little camera: https://www.kickstarter.com/projects/podolabs/podo-the-first-stick-and-shoot-camera

I want to know the considerations of design and if there's any kind of reference.


texts: Where/why would grease be required on this electric motor?

texts:
Here's the nameplate from a 5 HP single phase electric motor - used in an air compressor:

Note that it reads:

HIGH TORQUE GREASE BEACON 325

which I interpret to mean that you should use high temperature grease of which "Beacon 325" is an example or recommended brand / product.
I'm familiar with electric motors which either have used permanently-lubricated sealed or shielded bearings, or alternatively bearings which required oil. But I haven't come across any which require periodic grease maintenance.
Although a permanently sealed bearing would of course have grease I'd be surprised if a motor was expected to be disassembled for regular grease service. And I don't see any grease fittings.
So what does this mean? What service is implied by the grease statement on the label? Could this refer to the motor application (air compressor) and not the motor itself? But it seems like a general purpose motor.


texts: How can I cheaply drill a 0.1 mm hole in a small piece of tungsten?

texts:
I have a 10 mm diameter rod of 99.5% pure tungsten that I want to drill a 0.1 mm hole in using my Grizzly G0768 lathe. The hole only needs to be between 0.1 mm and 1 mm deep and is for a 3D printer hot nozzle. I don't know if this will break the bit yet, but I will try it when the drill chuck comes in the mail. If the bit breaks, I'll move up to a 0.15 mm hole, and so on...

I can't afford a high precision mill that costs more than $1,000. Assuming my lathe can't drill such a small hole, what other options do I have to accomplish this task on a budget? When I have gone shopping I have seen no indication of the stability / precision of the tools.

I could send the pieces of tungsten off to get drilled, but I expect that might cost a fortune.

If anyone has experience making holes this tiny, I would like to know the approach you used.

I have nice $12, 0.1 mm PCB bits made in Germany from Tungsten Carbide that break if you so much as look at them. I also found some cheaper bits on eBay but they don't look like drill bits so I'm not sure if they'd even cut a hole.


texts:
NPSHa formula - h(sp) +/- h(s) - h(f) - h(vp)

h(sp)- static pressure head (absolute) applied to the fluid

h(s)- elevation difference between fluid level in reservoir to pump inlet

h(f) - friction loss in suction piping

h(vp)- cap or pressure of the liquid at a stated temperature

How do I determine whether h(s) is a positive or negative ?

I’ve researched that-

Pump below reservoir , h(s) is a positive and vice versa but I don’t know the reason behind it ... I’ve been told that if it’s not good for the pump, u have to substract away from the NPSHa formula which makes sense for h(f) and h(vp). and if it’s good for the pump, you have to add.

am I right to say it’s because the fluid loses more energy as it needs to fight against gravity , that is why h(s) is negative if the pump is above the reservoir, this means more work for the pump.

and if pump is below reservoir, the fluid doesn’t lose much energy.


texts:
Aerospace engineering textbooks make frequent use of non-dimensional coefficients like $C_L$, $C_D$ and a whole host of others. Usually, for equations of motion, it is preferred to replace variables with non-dimensional coefficients. However, fundamentally I do not understand why.
I have two questions:

Why do we make aircraft parameters non-dimensional ($L$ to $C_L$, $M$ to $C_m$)?
An often-heard response is you need the coefficients in order to compare different aircraft; $L$ and $D$ are really dependent on aircraft dimensions and flight conditions. However, as far as I know, coefficients $C_L$ and $C_D$ are also dependent on aircraft dimensions and flight conditions! Where is the inherent superiority of one over the other?

Does non-dimensionalizing make the coefficient independent of anything (weight, aircraft dimensions, dynamic pressure, Mach number etc.)?
Some textbooks state that non-dimensional coefficients are independent of weight and aircraft dimensions but do not give an argument for why that should be the case.


texts: How can I estimate the rate of consumption of oxygen in a car engine?

texts: I need some approximate figures for how many litres of oxygen per minute a typical car engine requires. How would I estimate this?


texts: Why do pitching machines use wheels and not solenoids, actuators, servos or peumatic cylenders?

texts:
I guess that generating movement is harder then keeping a wheel rolling, but in terms of power consumption is it possible to compare the power consumption of a motor for driving wheels to that of a circuit that charges a capacitor and powers a solenoid? Running on high voltage solenoids can be very fast and powerful, and also pneumatic cylinders can be very fast.

Let's say we talk about a 5g ball that is shot at a speed of 10m/s.

Will the preferred motor be different for different weights and speeds? E.g. will an actuator be the choice for heavy and slow situation? Why?


texts: It seems dynamic magnetic field may damages electronics components like diode,  transistor etc, probably via electromagnetic induction.  How much strength and what frequency magnetic field is dangerous? Surprisingly there is hardly any info on Google on this.


texts: How does Nonlinear Viscous Damping work? In what way are Viscous Dampers typically nonlinear?

texts:
Viscoelastic materials like metal cables/wires/strings/webs/beams can be modeled with a variety of combinations of springs and dampers as described here.
For example, one simple common structure to represent these materials is as follows:

The spring, represented by Young's Modulus of Elasticity, has a generally predictable nature to its nonlinearity which is described and shown here:

Is there any general concept by which the nonlinearity of a viscous damping coefficient can be similarly displayed or understood?
In simple terms, say for a piece of metal being stretched/bent:

Would a viscous damping coefficient be higher or lower at higher velocity of bending/stretching?
Is there any similar published data or curves that could demonstrate the relationship between the damping coefficient and velocity of bending/stretching?

The only information I can find on nonlinearity of viscous damping tends to pertain to models like the Bouc-Wen Hysteresis Model .
Perhaps that model actually answers my question and I don't realize it? I'm not sure. I think that more pertains just to capturing damping due to displacement (rather than damping due to velocity/viscosity).
Thanks for any ideas or help.


texts:
If you look at a tire from the rear, you'll notice that the tire isn't quite a cylinder. It has edges that are slightly beveled. Sometimes this effect is clearly apparent, but other times, as in many car tires, it's hard to see.

I can understand the use on motorcycles, since they are typically angled on turns, but cars are, in general, not designed to take corners on two wheels.

Why do cars have beveled tires?


texts: Calculate the torque needed to turn a rod it's own axis

texts:
If a rod is turned around it's own axis, force/torque is needed.

Let's assume the rod it self has a diameter $d$, a length $l$, the mass $m$ and should be turned by a motor on one side. The other side is laying on a support, that prevents it from moving sideways which is not frictionless $\mu_{rod-supp}$.

How strong must this motor be?!

So far I tried around a bit with Moment of Inertia. But I don't know how to go from there.

It is a real life problem I need to solve. The rod needs to turn once in 3-8 minutes and I have to find a fitting stepper motor for that, that's why I need the torque.


texts: Are small car engines designed to tolerate a higher duty cycle than large car engines?

texts:
For simplicity we're going to ignore aerodynamics and vehicle mass for a moment...

Are small (around 1 litre) car engines designed to tolerate a higher duty cycle than large (2+ litre) car engines?

Cars are usually all travelling at roughly the same speed which means the engines will be putting out proportionally similar amount of power, however a small engine would be operating at a greater proportion of its output than a large one to maintain the same speed.

For some background to this, I have a 1.1 l car and I spend quite a lot of time with my foot completely flat on the floor, especially going uphill on a high speed road (60 or 70 mph limit) to keep up with the traffic. I think my record's somewhere around 2 minutes on full throttle.


texts: PU vs Polyester resin for exterior moulding

texts:
I am designing a sculpture based on a Gothic window which will consist of a steel frame with 3 inset panels in cast resin. The panels will be the 3 larger interior ares in the drawing with detail on both faces. Each face will be moulded separately and then joined in a 'clamshell' type arrangement with the gap filled with rigid foam (possible with additional internal reinforcement).

The panels will have a lot of surface detail (based on a pattern made by primary school children) and the exterior surface will be metal filled resin (probably aluminium) and approximately 20mm thick, backed internally with several laminations  of glass mat.

These panels will be bolted to the steel structure via weld brackets. They are not inherently structural but will be subject to light loads form flexing of the main structure plus wind loads etc.

In the past I have used polyester resin for this application but had problems with casting defects largely caused by the high viscosity of the resin plus metal powder. I have had much better results with PU casting resin for smaller, well supported castings but I'm not sure how it would bear up under long term outdoor exposure.

So I am looking for nay thoughts on the relative merits of PU vs polyester for this application. The mouldings should have a life of at least 10 years outdoors in a temperate climate (UK).


texts: Uniform linear movement to uniform rotary movement

texts: How to convert uniform linear motion(mm/s) to uniform rotary motion(deg/s). I.e. table saw blade tilt mechanism. Something like reversed Scotch yoke mechnism.


texts: Why laptop keyboard has so many bus lines?

texts:
I changed one laptop keyboard on the new one and while changing it I noticed that it has 30 line bus.

But from my VLSI practice, I know that keyboard can use only 1 data line and 1 clock line (PS/2) or 2 data lines on (USB).

The question is why it has such number of lines? Is it because it doesn't have a microcontroller in it and it is presumably located on the motherboard? Please explain the structure in detail if you can.


texts: How do I Calculate Pressure at Multiple Points in Time while Filling a Container with Water?

texts: Say I have a container completely full of water with a volume of 3000 gallons and I'm filling this container with water at a rate of 8.2 gallons per minute, it's already full at 200 PSI, how do I calculate how much pressure I've gotten up to at 10 sec, 20 sec, etc?


texts: Connections between RC retaining walls and sheet pile retaining walls

texts:
I'm working on a flood defence scheme in which a section of RC flood wall becomes sheet piles. The reasons for this aren't important, but the solution isn't to simply make all walls one or the other.

My issue is how to connect these two very different types of wall in a way that provides an expansion joint for the concrete but is also water-tight. This isn't an issue for connecting individual concrete panels as a waterstop is simply cast into the expansion joint, providing a seal. However, sheet piles don't have anything to 'cast' onto.

My idea so far is to design a sort of concrete (possibly mass, probably RC) 'pilaster' at the end of a section of sheet pile that will allow a water stop to be cast into. However, sheet piles deflect a fair amount which is making me wary of casting a rigid concrete section at the end of the sheet pile.

I'm at a bit of a loss here and struggling to find a precedent of a connection like this. SURELY it's been done before?

I've attached a quick hand sketch. I'm not too bothered about detailed calculations for this; I'm more interested in solving the buildability issues at the moment.

Dimensions are subject to minor alterations but roughly:

The RC wall penetrates 1.5 m below ground level
Sheet pile penetrates 6 m below ground level
RC wall stem is ~350 mm thick
Sheet pile section is 450 mm thick (AU25 section)


texts: What is the point of this valve that only allows air in and not liquid?

texts:
I'm looking at googles mocktails maker. And it puts 2 holes in a container. 1 hole is connected to a pump that will take water out and the other connects to a backflow prevention valve that only allows air in and not liquid.

What is the point of having that valve? It doesn't connect to anything. Also when I test it with and without having that valve the water does the exact same thing.

Reference:
https://github.com/deeplocal/mocktailsmixer#step-19-attach-tubing-and-check-valve

EDIT: Does it have to do with keeping the container pressurized? Why would I need to have a constant pressure if the pump doesn't require it.


texts:
Under Hooke's law, we know that sigma stresses are responsible for volumetric strain, while shear stresses are responsible for the formation of form strains. In a lecture at my university it was shown as follows (drawings). However, one thing puzzles me: if our cube were subjected to very high shear stress resulting in large gammas, shouldn't the top wall of the lecture cube move downwards (red arrow)? If so, then we would have a change in volume (shortening height) without a sigma. In that case, does Hooke's law only make sense for very small taus resulting in negligible gamma? Did I make a mistake somewhere in my thinking?

Thank you.


texts: Is lead filter same as PD combined with a low pass filter?

texts: I am curious to know the difference between a lead compensator (lead filter) and a PD controller with a low pass filter. From the theory I can see that the transfer function of both these controllers are same. By choosing appropriate gains and placing zeros and poles at right frequencies, we can obtain same bodeplot (magnitude and phase plot). So, what is the real difference between the two? Why use different names for the same controllers?


texts: Gear design for symmetrical opening of two parts

texts:
I'm trying to build a lamp which has about 20 identical layers stacked on top of each other. There is a central spine and, on each level, a pair of arcs attached to the spine that are hinged and which meet each other (this looks like a big rib cage, where the ribs are free to rotate in and out). I'd like to create some gearing such that moving one side of one layer will move the other one symmetrically, keeping each layer symmetrical. I don't need any automation to move them, but I just want them to be constrained to symmetry.

The general gear plan could be something like this: http://www.gearsket.ch/#c74a934963cc29f8

...but I'm not able to attach the outside gears (which would be attached to the ribs) at the rotation axes of the ribs, because of the hinges.

I may be able to get that to work, but I'm getting worried that the gears (to be CNC machined out of wood) are getting to be pretty big (each layer, when closed, is a circle about 8 inches in diameter), and are going to take over the look of the lamp.

Are there any alternate gear or linkage designs that would help to constrain these to symmetrical opening/closing motion?


texts:
I have assembled a small DIY drip-irrigation system for my terrace garden. Please have a look at the attached image. I switch on a small pump to start the drip-irrigation system and then switch it off. But even after that, the water keeps flowing through the system and stops only when I physically lift the pump out of water.

How can I stop this water flow without requiring any physical action?

Please note that I plan to automate the switch-on/off of the pump using a timer so that it functions without requiring my physical presence.

========================================================================

I tried the suggestion of "Making a pinhole in the highest point of the pipe." It worked like a charm and solved the issue I was facing. Completely loved it, more so, because it does not involve procuring new stuff.

I also like the option of using a solenoid-valve, but have not tried it yet. Will use it when I install such a system again where the tank is at a considerably higher place than the plants.

Thank you everyone who took the effort to write an answer, and that too with detailed explanations.


texts:
I am measuring BLDC motor vibrations with ADXL345. I use 2 propellers, one perfectly balanced and other bad, which vibrates a lot. The problem is I get similar results from accelerometer with both props. I tried ODRs from 200 to 3200 and results look similar with both props (1000-5000 RPM). I get real time data from MCU which reads raw data from accelerometer, then my program draws a real time chart (amplitude vs time, no processing just raw accelerometer data), so I visually check the results while trying different things.

What can be the problem here? I want to be able to detect vibrations on the motor.


texts: What does the author mean? Turbomachinery - Reaction

texts:
I am reading a book of Fundamental Energy Systems.
The author describes the rate of change in head for a turbomachine as:
$$ \frac{1}{2}[(V_1^2-V_2^2)+(U_1^2-U_2^2)+(V_{R2}^2-V_{R1}^2)] = H =U_1V_{u1} - U_2V_{u2} $$
and the static effect as:
$$SE =(U_1^2-U_2^2)+(V_{R2}^2-V_{R1}^2) $$
However he later says:

His wording states $ R = SE/H $. But he actually wrote it as we see above:
$$ R = \frac{SE}{2H} = \frac{(1/2)SE}{(1/2)2H} = \frac{(1/2)SE}{H} $$
I tried deriving his result from $ R = SE/H $ but it was not possible, I just want to make sure my conclusion is correct (R = (0.5*SE)/H ; instead of R = SE/H ) as the author does not seem to mind his own wording.
Thanks for illustrating me.


texts: Why Taylor's microscale gives us information about the smallest scales of the flow?

texts:
So I understand the principles of two-point time correlations (covariance) and how you can just normalise that to get the autocorrelation. I also understand the integral time scale which is quite intuitive really and tells us the largest scales in the flow.

Now Taylor's microscale is sightly trickier it seems. We look at the slope of how quickly the autocorrelation decays from 0-seperation which seems to be related to a short-time microscale $\lambda$ by an inverse-square law!? For clarity I am of course talking about

$$
-\frac{2}{{\lambda}^2} = \frac{d^2\sigma}{d{\tau}^2}
$$
where $\tau$ is the time seperation and $\lambda$ is the Taylor's microscale. So can anyone explain what Taylor was thinking and how he got to this? Was it just a hypotheses which seemed to work or did he justify in theoretical ground? (probably a combination)

P.S. I am of course a mechanical engineering student and not a mathematician however still interested in these details so long as it could be explained simply.


texts: If anyone can provide me information about this part right here, please tell me.


texts: Feedback loop and zero - error in steady state

texts:
I need help with this exercise. I 've tried many times with pen and paper but I'm stuck. I don't want a full answer but some feedback .

Here is my progess:
$$\frac{dx}{dt} = Ax(t) + Bu(t) \Rightarrow sX(S) = AX(S) + BU(S) \Rightarrow \\\Rightarrow X(s)=(sI-A)^{-1}BU(S) \ \ \  (1)$$
Now let's note as $$G(t) = \frac{x(t)}{u(t)} $$ So : $$G(s)= (sI-A)^{-1}B $$
Then we can write: $$\frac{U(s)}{R(s)} = \frac{1}{1+G(s)k} $$
Now , we need a zero - steady state: $$\lim_{t \rightarrow \infty}u(t) = \lim_{s \rightarrow 0}sU(s) =0$$
$$sU(s) = s\frac{1}{1+G(s)k}R(s)$$ but $$R(S) = \frac{1}{s}$$ so
$$sU(s) = \frac{1}{1+G(s)k}$$
This can happen , iff : $$\lim_{s \rightarrow 0}G(s)k =\infty$$
$$\lim_{s \rightarrow 0}((sI-A)^{-1}B)k)=\infty \rightarrow \lim_{s \rightarrow 0}(\frac{adj(sI-A)}{det(sI-A)}Bk)=\infty \rightarrow   \lim_{s \rightarrow 0}adj(sI-A)Bk=\infty$$
But $$(sI-A)= \begin{bmatrix}
s+7 & -10\\
1 & s
\end{bmatrix} \rightarrow adj(sI-A) = \begin{bmatrix}
s & 10\\
-1 & s+7
\end{bmatrix}$$ and
$$\begin{bmatrix}
s & 10\\
-1 & s+7
\end{bmatrix}\begin{bmatrix}
1\\
0
\end{bmatrix}k=\infty$$ ...
And here is my struggle...


texts: How are train crossing signals and highway traffic signals coordinated?

texts:
Some roadway intersections that are near railroad tracks have signs that light up when a train is approaching. These signs warn that certain turns are not allowed because of the train. One of these signs is shown below from the City of Edmonton.

My understanding is that normal train crossing signals are the responsibility of the railroad and that traffic signals are the responsibility of the highway department. This wouldn't normally seem like a big problem, but these are two completely different systems and organizations.

Obviously there is some way that the two owners coordinate and communicate the train warning information.

How does the train warning signal get passed from the railroad signal to the traffic signal? Is this as simple as a wire run from the train signal that is "high" while lights are on? Is there standard way that this connection is done?


texts:
For civil engineers,
There is a high drain connection work is under progress in my location. Few days ago, a contractor visited my house and asked me to construct 2ftX2ft inspection chamber inside the premise for connection with high sewage drain. Now I found that there is another inspection chamber being construct outside my premise building(at road) and these are finally being joined with manholes.
My question is, what is the need of 2 inspection chamber just inside and outside the premise building?


texts: Designing a pneumatic system for consistent pressure/flow

texts:
Fellow engineers, I need your help in improving my design for a pneumatic system for maintaining a constant supply of at least 90 PSI and 20 CFM for a particle analyzer with stringent air requirements. Its expected to draw air every 2 seconds. Here's the breakdown of the components used in the setup (in this order). Picture attached.

A: Bulk water separator. This should help with removing moisture from the air because our plant air is heavily moisture-laden at times.

B: Particulate filter: 0.01 micron air filter to ensure clean air, free from particles.

C: Desiccant air dryer: Heat-less desiccant dryer for dry air. -40 C pressure dew point to ensure that there is no further condensation beyond this point and the air stays dry till it makes its way all the way to the analyzer. The dryer is rated for an inlet flow of 45 SCFM. I up-sized it because this is a heat-less dryer so a certain percentage of the air going in to the dryer will be used to regenerate the desiccants as well. The dryer has an in-built filter that will prevent any of the desiccants from leaving the dryer.

D: Globe valve: This is to contain the flow rate coming out of the dryer. This was suggested to me by another engineer. Since we are filling up a large tank, the air coming out of the dryer could potentially exceed the rated flow rate of the dryer which could damage the desiccants.

E & F: Check valve and booster pump in parallel. The booster pump is meant to charge the receiver tank to a pressure of 95 - 100 PSI. The check valve is there to reduce the charge time by allowing air to pass through up to the inlet pressure. This could help take some of the burden off of the booster pump so that the pump only cycles when the tank pressure needs to be raised to setpoint.

G: Air receiver tank: This will help create a reservoir of air that will ensure that the analyzer never has to wait for air. The tank is rated for 200 PSI but I won't be charging it more than 100 PSI. Still debating if I should go with a smaller tank because 80 gallons is an awful lot of volume for the booster to fill.

H: Filter: To get rid of any of the remaining particles and oil vapors left in the system.

I: Pressure regulator: To maintain the desired pressure for the equipment

J: Equipment - Particle analyzer.

Any suggestions on improving this design?


texts: Exporting Civil 3d Model to Google Earth (KML) shows strange triangular shadows

texts:
I am trying to export civil 3d model but when i do so the kml output shows shadows. Please refer attached image.
Is there any settings in Civil 3d to remove them.
Please help


texts: How can I get the spindle driver current internally?

texts: I am working on monitoring research. During it I found a lot of papers use Hall effect sensors to get spindle current. However some of them are accessed internally to spindle driver current. I will be thankful if any cnc professional can guide me how to access internally to spindle current and which types of cnc have this ability?


texts: Dynamics Simple Pulley System - Stuck on the Process

texts:
Have spent hours poring over this homework question but am having difficulty getting the right process going to solve the problem. I don't really know where to start, and I'd really be grateful if someone could show me the ropes (pun intended ^_^). There are two components to the question.

(a) What is the tension force $T$ in the cables at this instant (Newtons)

(b) What is the net horizontal thrust force required to produce the truck's motion? This includes drive force from the wheels, rolling resistance and air resistance.

My (flawed, obviously) attempt at A went something like this:

Draw FBD for block A
Apply Newton's Second Law, where tension in cable is constant throughout its length $F_{y,A} = 2T-m_A\cdot g = m_A\cdot a_A$
Length of cord is constant, so $L = -2X_A+X_T + C$, and $-2a_A+a_T = 0$, so the acceleration of block A is $\frac{1}{2}a_T = 1.2\text{ m/s}^2$.
Rearranging equation from (2) provides $2T = m_A*g + \frac{1}{2}m_A\cdot a_T$, and then T = 456.5N.

Part B I struggle with altogether, because I don't have a clear process in my head to tackle the problem.

Edit~ A written attempt at a solution - Not sure how to factor in the angled a(T) as proposed...


texts: How to use consumer electronics for industrial application on high temperature

texts:
I need to measure the width of a bar made out of glowing red steel (900-1200 degrees Celsius) using computer vision.

In order to ensure resolution of a 0.5 millimeters/px, the camera is needed to have enough pixels and, considering the field-of-view, to be at a certain distance from the bar.

Can anybody think of a way to use a camera at a distance of 0.5m from the glowing hot bar? Air refrigeration? Refractory enclosure?

Let's talk about it?


texts: What is the principle behind electric hoists having two load capacities?

texts:
Electric hoists such as this one http://www.builderauthority.com/product/6013242/ commonly have two load capacities depending on whether a single-line or double-line configuration is used. What is it about the double-line configuration that allows the load capacity to be doubled?

Thanks in advance.


texts: Does thickness impact resolving loads for an inclined beam?

texts:
I have a 3 m x 1 m x 1 m cuboid weighing approximately 10,000 kg. I am trying to resolve the vertical forces that will support the cuboid if the cuboid must rest at a 45 degree angle.

Which of the two solutions below (if either) is best for calculating the resolving forces?

In both cases I assume a 2-D cross section of the cuboid where the resolving forces act at the bottom two corners.

The first method is to treat the cuboid as a beam and the weight as an continuously distributed load. This results in an even distribution of the load between the two resolving forces being even irrespective of the angle.

The second method is to assume the weight to be a point load at the center of mass. Then use the sine rule to determine the position the force acts along the base line of the beam. This gives an uneven distribution of the loads with weighting slightly towards the lower corner but seems to be dependent on thickness.

I am reasonably confident it is the second but I want to know the mathematical explanation.


texts: What is the formal term/process for writing down a design?

texts: I forgot what all of it is called but there's this specific way you draw the different components of a device or machine, kind of like blue prints but on plain write paper. You break the device down into larger pieces and draw each piece orthographically from like 3 different perspectives with labels and uncertainty in measurement requirements and all that, very standard. Anyone got a clue?


texts: Are the modal participation factors bounded for shock response spectrum analysis?

texts:
Recently dug myself into the theory of shock response spectrum analysis, but one thing is not clear for me.
The theory says that the peak response of the structure can be calculated as the product of the participation factor and the pertaining point of the shock response spectrum.
The participation factor is calculated as:
$$
\Gamma_{kj}=\phi_{j}^{T}\textbf{M}\textbf{1}_k
$$
where $\phi$ is the eigenvector, $\textbf{M}$ is the mass matrix and $\textbf{1}$ is the corresponding rigid body motion vector.
Since the partcipation factor calculation includes the eigenvactors, which are not exact as they are scaleable, it would mean, that the response of the strcture would depend on the eigenvector normalization.
So my question would be that does it mean that it is assumed that for this type of analysis the eigenvectors are mass normalized and if so are they bounded to a specific value?
Reference:
https://www.comsol.co.in/multiphysics/response-spectrum-analysis


texts: How to convert output of controller (control signal) into PWM signal?

texts: I am trying to control a mechanical system with some transfer function T (output is position & input is voltage). I have implemented a state feedback controller in order for the output of the system to reach a certain position. The actuator of the system is an RC Servo Motor which is actuated by PWM signals. I want to convert the output of the controller into proper PWM in order to control the system. Are there any guidelines which I should follow or is there a specific way in order to manage to convert the signal ?


texts: What are functional and manufacturing datums

texts: Can somebody please explain what is ment by functional datum and manufacturing datum, with respect to dimentioning and tolerancing.


texts: Foundation Excavation: How much larger than the RCC footing?

texts:
I am trying to estimate the volume of excavation needed for the foundations of a structure from the drawings provided.

The drawings clearly give the dimensions of the RC / cement footing but I suppose the actual excavation will need to be larger than this? How much larger should I plan for in the costing calculations.

Any rules of thumb?

Another issue that comes to mind is that although the RC / cement footing structures are rectangular or various dimensions, any practical excavation would have a slight slope in the walls that increases the excavation volume? Or is that not so significant?


texts: PE Designation on business card if firm doesn't offer engineering services

texts:
I went through all of the work and experience at a previous job to get my Professional Engineer's license, however, my new firm is not licensed to provide design services.  Is it still allowable to place "P.E." after my name since I am a licensed professional engineer even though I will not be providing sealing and stamping of documents?
I know some engineers will get their licenses even if it is not required, but I wasn't sure how this lined up with presenting your credentials on a business card.


texts: What size of fan requires motors with a transmission?

texts: I am wondering at what fan size/speed a direct drive motor is no longer sufficient to drive a fan?  Phrased alternatively, what size/speed of fan requires motors with a transmission? For an axial fan.


texts: How do I size a condensing unit for a commercial refrigerator having the following info:

texts: McCall reach-in M# 4-4070C; S# M713863; 70 cu.ft. (very little info on this frig.) Operating temp range 35F-43F. Evaporator temp range probably is 20F-25F  Currently set-up to operate with R22. I would like to convert it to R134A so I will need to replace the condensing unit and expansion valve. The problem is that its 25 years old and the MFR (now Delfield) has no data on conversion. Oh, also I found out that the replacement expansion valve is rated at 1/4 Ton. The replacement compressor is rated at 1/2 Ton (1/2HP). (remember it's an R22 TXV and compressor). The Beacon site load calculation for the box size and insulation is 3500 BTUH. I've always thought that horsepower was horsepower, but how do I compensate for the differences in the refrigerants. Or do I even need to?


texts: How to decide initial size increment in Abaqus Dynamic Implicit?

texts: I am using Dynamic Implicit to model a rolling problem. But I am not really sure what to choose as Initial increment. The default suggestion by Abaqus is the step time.


texts: Why is the normal stress assumed to be 0 in plane stress?

texts: If a plate is elongated in the x and y direction, why is the stress sigma z considered negligible with respect to sigma x and sigma y?


texts:
Why can we neglect the inertial (but not viscous) term in Navier-Stokes at low flow and high viscosity?

Complete Navier-Stokes: $\rho \frac{D\vec{v}}{Dt}=\rho g - \nabla P+ \mu \nabla ^2 \vec{v}$

Inertial term:
$\frac{D\vec{v}}{Dt}=
\frac{\partial\vec{v}}{\partial t}+
\frac{\partial\vec{v}}{\partial x}v_x+
\frac{\partial\vec{v}}{\partial y}v_y+
\frac{\partial\vec{v}}{\partial z}v_z$.

And as we assume a stationary flow and low rate: $
\frac{\partial\vec{v}}{\partial t}=0,
\frac{\partial\vec{v}}{\partial x}\approx0,
\frac{\partial\vec{v}}{\partial y}\approx0,
\frac{\partial\vec{v}}{\partial z}\approx0$. And so it follows that the inertial term can be ignored.

However in my material it is also stated that the $\mu \nabla ^2 \vec{v}$ will be the dominating term during these circumstances. Why will it not be so that $\nabla ^2 \vec{v} \rightarrow
\frac{\partial^2\vec{v}}{\partial x^2}\approx0,
\frac{\partial^2\vec{v}}{\partial y^2}\approx0,
\frac{\partial^2\vec{v}}{\partial z^2}\approx0
\rightarrow \mu \nabla ^2 \vec{v} \approx 0$ as well?


texts: For a building on a slope, should the grounded earth lightning protection be downhill or uphill from the structure?

texts: Would it be best to place the earth protection (the copper spike) for a building on a slope downhill (A) or uphill (B) from the structure? Assume that lightning is most likely to strike at (C), the hill which is also much higher than the lightning rod on top of the building. Assume the soil is rocky and there is no way to drive the stake in at B far enough to get BELOW the foundation.


texts: How to heat CO2 coming out of a gas canister to human breath temperature?

texts: I am releasing CO2 from a cylinder into a ventilated room and want to mimic a human breathing (let's ignore the in/out breath). Problem is that the gas that comes out is at room temperature (or lower due to decompression) not body temperature. How can I heat the gas that comes out of the cylinder to 37ºC?


texts: Do the steels 1.4404 and 1.4571 look the same?

texts:
A contractor delivered three components, all are supposed to be in 1.4571. Part A is actually done in 1.4404 / (X2CrNiMo17-12-2) (according to pretty conclusive documentation). Part B is allegedly done in 1.4571 / (X6CrNiMoTi17-12-2), but the material looks like part A (shiny, silvery). Part C meanwhile is also allegedly done in 1.4571, but looks different (silvery gray). "Allegedly" means that for the documentation for parts B and C is far less conclusive.

So, from someone who has encountered both steels: Would I expect them to look the same?

Or, to rephrase my question: Part A and C look the same but, according to the documentation provided, should be different materials - does this tell me something is amiss?


texts: Problem with RHP zero in transfer function

texts:
I have a transfer function with a RHP zero in $s=+1$, and I am trying to show in Matlab thath this limitation is present. In particular, initially I had a MIMO system, which I decoupled and then I started doing this analysis on the two separate SISO system that came out of the decoupling.

My code is the following:

s = tf('s');
G = [2/(s+1) 3/(s+2);1/(s+1) 1/(s+1)];

d_12 = -(G(1,2)/G(1,1));
d_21 = -(G(2,1)/G(2,2));
D_simp = [1 d_12;d_21 1];  %decoupler
F1 = G*D_simp;

k1 = 5;
k2 = 2;
k3 = 50;

loop1 = loopsens(F1(1,1),k1/s);
loop2 = loopsens(F1(1,1),k2/s);
loop3 = loopsens(F1(1,1),k3/s);

figure;
bodemag(loop1.Ti,'r',loop2.Ti,'b',loop3.Ti,'g'),grid
figure;
bodemag(loop1.Si,'r',loop2.Si,'b',loop3.Si,'g'),grid

where I am trying to increase the bandwidth of the system by increasing the gain.

The expected result is that if I increase the bandwidth , I should have worse performances as the bandwidth increases, but what happen is exaclty the opposite:

can somebody please help me solve this problem?


texts: Is there some temperature at which all "5w" oils should have about the same viscosity?

texts:
Is there some temperature at which all "5w" motor oils should have about the same viscosity?  (5w-20, 5w-30, 5w-40, 5w-50, etc.)
I am looking for SAE or ASTM wording or chart that says it straight out, by definition.  But it's not exactly jumping out at me.
Maybe it is not that simple?  Maybe they don't define it that way?
Could I find the answer by using ASTM D341 graph paper to chart out a few oils with known mfr specs for viscosity at 40 deg C and 100 deg C ? (which they all have)

One little problem there is I would need the chart that covers from 100 deg C all the way down to, I don't know where, but some pretty low temps, and I can't see the limits on any of their 7 charts.  And I don't know if those charts are accurate for modern motor oil either.


texts: Low-Flow Nozzles for Corrosion Spray Testing

texts:
So, for a cyclic corrosion test system, I need a nozzle or arrangement of nozzles that provides a flow rate of 45ml-140ml of salt solution per hour to an area 60cm square. All commercial nozzles I've been able to find with non-flat spray patterns have much higher flow volumes. Does anyone know if a specialty supplier for this type of equipment?

Also, I need to ensure that the area is saturated as evenly as possible - what sort of FEA or simulation program would be best for analyzing the distribution of mass/fluid in a spray arrangement?


texts: Does having 2 engines together increase anything?

texts:
If I have a vehicle (V1) with one 100 kW engine and an identical vehicle (V2) with 2 of these 100 kW engines, will this mean that V2 will have double the torque of V1 and double the top speed of V1?

Suspected Answer

It's not like in a series circuit in which, when you have two identical batteries in series, the the voltage doubles.

I'm guessing that there will be some increase (but not double) in torque, but the top speed would remain the same between V1 and V2 whilst pulling an identical load.  I suspect that the difference between V1 and V2 will be that V2 may be quicker to achieve the top speed, but the top speed won't increase by much.  I.E. V1's max speed pulling 30 kg will be 20 kph but might take 10 seconds, but V2s max speed pulling 30 kg will be 20 kph but might take 8 seconds.


texts: There is an airport bus (Germany) which has it's rear wheels covered by the fender. Even front wheels have strange shape of fender around them (tilted toward front). What purpose of that?


texts:
I'm not exactly sure where this question would go, so I've decided to post it here. Hopefully you can help.

Using a smaller computing device (i.e. an Arduino or Raspberry Pi) and other outside tools, would it be possible to construct a magnetic stripe device with an extremely low coercivity so that its code could be changed on the fly by a computer and an encoding device? If this is possible, what devices would be best for this kind of project?


texts: Why is there still no truly omnidirectional treadmill? (technical reasons)

texts:
Disclaimer: I'm not a (device) engineer. I don't know the terminology. So I suppose some of my statements, questions or ideas could sound either naive or vague.

As far as I undestand, the most advanced (and publicly known) omnidirectional treadmill is the Infinadeck. But with current state of the progress on this treadmill, it's clearly not ready for a mass market. One of my biggest concerns is the shape of the treadmill: why don't the Infinadeck's engineers use a disk instead of a square?

I was thinking about possible implementation. I'm not sure how easy it would be to implement. Because, of course, the biggest issues are often related to  implementation details. I would like to hear your thoughts about it. As well as some comments on Infinadeck's shape.

This description isn't touching the vector generation or movement initiation, it's just about directionality of the treadmill.

Figure 1.

Figure 2. Single engine: the sphere and the conveyor parts. This figure doesn't show the spikes, though.

So the shape of the device is cylindrical. There are three major elements: shell, engines and platform.

Shell is just a container for the engines.
Platform is a thick metal disk wrapped in a thin elastic and seamless case. So it's like in regular one-directional threadmills, but radial. The case, of course, is smooth on the inside to lower the friction. But on the outside it has numerous tiny sockets that are used for pulling the case in the desired direction. And of course it's not fixed by some kind of joints or anything. It lies on top of the engines. There also may be some supporting columns beside the engines. On the other hand it needs to be restricred by the shell, so that it stays inside.
There are multiple engines, spread inside the shell. Each one of them consists of the two major parts:

The sphere that translates its movement into movement of the case above it. The sphere isn't a smooth ball. It's covered with numerous spikes all around it which precisely fit the sockets of the platform's case. So when the sphere rotates, it pulls the case in the same direction.
The same spikes are used to rotate the sphere. There is a pair of conveyor belts(see Figure 2) that translate their movement into the sphere's. I suppose the easiest way is to make the spikes penetrate the belts. And this pair of conveyors can move around the sphere horizontally depending on the required direction but independently of the vertical movement of the belts itself.

UPD: The platform should be able to move in any direction at any moment (with reasonable latency, of course). And the vector is generated in real time by Neural Network watching the user of the treadmill. So the person just walks in random direction and the neural network instantly generates the vector, which is then translated into engines movement.

How far this concept from reality?


texts: Finding force distribution using accelerometer data

texts:
The team I'm currently working for is trying to compare bushings with different durometer ratings in the front suspension using single axis(z) accelerometer data during curb impacts. The current problem at hand is that the amplitude recorded is close to one g or two and noisy at curb impacts. I did a FFT and PSD analysis to check that none of the contributing frequencies match the resonance frequency of the accelerometer. This was followed by Inverse FFT of that signal.
Now my team thinks of forming some kind of force distribution using the denoised data.
Is it a good experiment using accelerometer data to compare the two different durometer bushings? For some reason, I think there is a better way to compare the ride quality using the different bushings.
The two accelerometers are attached below the seat and on the link connecting bushing to the base.


texts: Wireless communication modules transmitting through body

texts:
I wanted to be able to transmit data from a wireless module to an Arduino. It is possible that a human body could come between the wireless module and the Arduino or someone might cover up the module with their hands. So I was looking for some kind of wireless module around 100 MHz because the human body transmits these signals without interference or absorption. I have found many 433 MHz radio wave modules online but nothing around 100 MHz range.
I was wondering if there is any off the shelf component or is there a simple strategy for creating a wireless module around this frequency range on my own?


texts: How does the number of cycles for averaging in a lock-in amplifier relate to low-pass filtering and where do I set it?

texts:
Please forgive me if I ask too many questions at once or I am too much of a rookie. I want to understand the working-principle of lock-in amplifiers (LIAs).
I understood the calculation that yields the outputs for X,Y,R and Φ. I am only interested in R (the root-mean-square amplitude of my original signal that was buried in noise).
But then I got bamboozled: In all these explanations on LIAs, it seems to be assumed that R is constant??? But R is not constant, my original signal can vary over time! When it is said that LIAs only measure AC and are not capable yet of DC signals, I am sure they refer to the modulation, not the original signal. But then I thought, that probably you would just average over a certain time period and this would give me a trade-off between signal response and noise cancellation.
--> Is this train of thought accurate ?
Also, where do I set the time span over which I want to average? Is this the bandwidth of the low-pass filter?
(Maybe too off-topic: Can someone tell me what DC offsets are in the context of LIA ?)
I would be really happy for responses and I hope I don't get downvoted for asking non-expert questions...


texts: Cast iron sewer pipe being used as stove pipe

texts: There is a house for rent with a big barrel stove in the basement, the stove pipe is insulated where it comes through the floor however it is made of old sewer pipe, cast iron I imagine, it's about a 15-ft section, this doesn't seem like a good idea to me.  I can find lots on specs for stove pipe (gauge of steel etc) but nothing the actually says what not to use for stovepipe.  Would appreciated clarification.


texts: Is it true that four-wheel drive is less efficient and if so, why?

texts:
I have heard many times that four-wheel drive is less efficient than two-wheel drive. Many car producers have a normal drive mode where only two wheels are powered, and turn the four-wheel drive on only when needed, to "save energy".

I have never understood why it should be so. You need to transfer only half the energy to each wheel (which must also save the material wear), so the total energy consumption must be the same.

Please answer the question also for the case of electric cars with four separate small engines each attached to a single wheel.


texts:
I'm building a small hobby CNC machine out of aluminium with the end goal of milling plastic, aluminium and possibly some harder stuff like steel (although if you saw the machine you'd laugh me out of the room).

The machine isn't as rigid as I would've liked in it's current incarnation. My solution to this would be to use a carbide endmill (~6-8mm or so) at high RPM (~8k) so the tool pressure is reduced and the machine doesn't flex. I've learned that HSS cutters will dull if the chip load isn't high enough, hence the use of carbide as it's a lot harder. I've tried researching this but all I can find are calculators and charts for chip loads for different brands of end mills. My spindle is 3-phase and will happily spin up to 24k RPM.

Can I use a carbide cutter at high speed to reduce chip load? Do I risk breaking the cutter by doing this?


texts: Differential Equation for: Locking a laser's frequency with a PI controller

texts:
I think I have a good understanding of differential equations, so I would like to first try to understand my system in terms of differential equations before transforming my system into the more standard Laplace-transform, looking-for-poles-type analysis that's standard in control theory.
Specifically I'm interested in finding the differential equation that governs what is known as a "Pound-Derver-Hall (PDH) lock" in optics.
In this locking scheme, an optical system is controlled with a piezo, and the goal is to have to use the piezo to correct for changes in the optical system. The system is set up like this:

A voltage is sent to the piezo in the mechanical-optical system. An error voltage is generated from the output of this system, and is sent to the PID controller. The error voltage looks something like this:

So, if you asked me, my differential equation describing this would be the form:
$\frac{dVin}{dt} = k_p V_{error} + k_i \int V_{error} + k_d\frac{d}{dt}V_{error}$
so in the area that my error function is strictly linear:
$V_{error} = g V_{in}$
then this becomes:
$\frac{dVin}{dt} = g k_p V_{in} + g k_i \int V_{in} + g k_d\frac{d}{dt}V_{in}$
Now what's confusing to me is that when I consider only proportional gain (ie $k_i = k_d = 0$)
Then I can solve my diff.eq. exactly:
$V_{in} = V_0 e^{g k_p t}$
which has a "sink" at zero as t approaches infinity.
Now I know from experience that "position only" controllers typically have lots of oscillations and don't necessarily converge to the solution but oscillate around it. Now if I had an "inertia" term to my differential equation that added a second derivative to the differential equation, then I would get a sinusoidal solution that I recognize as the typical "oscillations" in position-only control.
But generally speaking, is there a way to infer what this "inertia term" is?
Am I making some kind of mistake in my model?


texts: Vacuum vessel at 10mbar with a diaphragm pump: do I need a venting valve?

texts:
I'm working my way through learning vacuum technology.

I have a 10l vessel which I want to evacuate to < 10mbar. I'll use this diaphragm pump.

Do I need to add a (manual) venting valve to the system, or will switching off the pump do the job?


texts: Stress Concentration: Hole in infinite thin plate loaded in biaxial tension vs biaxial compression

texts:
Is there a difference in the stress concentration of a hole in an infinite thin plate loaded in biaxial tension vs biaxial compression?

I ask because in numerous books (one of them in the screenshot above), there is a calculation that determines the Kt in biaxial tension. I've also created a FEM model that correlates nicely. I created another FEM model where I just reversed the loading to put the plate in compression, and received the exact same Kt. I can't seem to find anything in the book or online about the biaxial compression case. Is this true?


texts: What is micro-electromechanical systems (MEMS)?

texts:
I know definition but how would you explain to complete layik ( as me ) what is MEMS and how it is used.

Examples: Silicon nanopore membranes (SNM) have been prototyped from silicon substrates by an innovative process based on MEMS technology.

micro-electromechanical systems (MEMS)


texts: Can a signal below -176 dbm, which is 1.6 db below thermal noise at room temperature, be decoded irrespective of the modulation type?


texts: Motors, Horsepower, RPM and Litres per minute

texts: How do I get a rough estimate of how many litres per minute a motor can push?


texts: Deflection of beam, according to thickness of top plate and bottom plate

texts:
When there is one rectangular beam like below image,

I would like to know how the beam is deflected according to thicknesses of top plate and bottom plate.

My concerning cross section patterns are like below.

The conditions are as below.

Thicknesses of both side plates are same.

Type 1 : thickness of top < thickness of bottom

Type 2 : thickness of top = thickness of bottom

Type 3 : thickness of top > thickness of bottom

Which type is less deformed? and Why?


texts: Torquing a nut beyond a known value using degree of rotation?

texts: I want to torque a nut to 320 ft lbs, but my torque wrench measures only to 250 ft lbs.  Since I know I can get it to 250 ft lbs, is it possible to use that value to calculate the additional degree of rotation it would take to get it to approximately 320 ft lbs?  For example... torque to 250, switch to another ratchet to avoid damaging the torque wrench, then rotate the nut an additional 45 degrees.


texts: consumer plastics that can take a bit of heat

texts:
I'm throwing a party with themed drinks, and one is a shot topped with 151, and set on fire.

I'll need to serve about 15 at a time, and don't own that many shot glasses.

Is there any disposable drinking glass that can be safely held at ~130 f (the only actual number I found online, but probably not too precise) for less than a minute?  What plastic number (the recycling number) should I look for?


texts: Calculating the minimum reflux ratio for separation of Acetone and Chloroform

texts:
Acetone must be recovered from a waste process stream, which also contains chloroform , so that it can be reused in the chemical process.
    The chemical process requires however that before the recovered acetone can be reused in the process that it meets certain criteria. The distillation column to be used for this separation is already in place and has the equivalent to 12 theoretical trays (not including the reboiler)
    The waste stream is a mixture containing 60 mole % acetone and 40 mole % chloroform. The chemical process  requires the top product to contain not less than 90 mole % acetone in order for it to meet specification required for reuse into the chemical process. It is also required that the bottom product contains  50 mole % acetone. As part of the setup of the existing distillation column there is a heat exchanger on the feed line into the column that allows the feed to enter at its bubble point and at a rate of 100 mol/hr.

So far I have tried to calculate the equilibrium curve which looks something like this:

I am unsure though if this curve can be used for the calculation


texts: Computer engineering vs Computer Science?

texts:
Sorry if this is in the wrong place; I haven´t posted in SE Engineering before, and the site said that SEE is also for students.

I´m a High School senior and I´m debating between Computer Engineering and Computer Science. Can someone give me practical ¨real world¨ differences between the two? I think I´m more interested in embedded systems, VR, AI, and electronics than just software (though who really knows until I actually study it!) Especially virtual reality and AI because they´re such new, promising fields. If I want to work in those fields would either degree be more applicable?

Thanks for your input! I´d really appreciate some replies from outside sources or personal experience.


texts: What are 'inside' and 'outside' dimensions in reference to castings?

texts:
I am looking at a company-written standard for cast parts. The castings are blanks for driveshaft yokes, similar to what is pictured below. The standard defines general tolerances for the dimensions on the part, and it classifies them into two categories:

Outside dimensions and center-to-center distances
Inside dimensions (core dimensions) 1

There is some confusion between us and our supplier as to what constitutes an inside dimension. Obviously, anything that requires a core (such as pilot holes for the yoke ear holes seen below) will be an inside dimension.

However, when our internal inspection requirements were laid out, things such as the distance from inside edge to inside edge of the ears were determined to be inside dimensions, while the outside edge measurement on the ears is an outside dimensions.

First, is this terminology common to castings (or even forgings) in general? I have looked at ISO standards regarding general tolerances, but they make no reference to it. If it is common, are inside dimensions strictly related to features requiring cores? Should other dimensions be considered "inside"?

For reference, the tolerances for outside dimensions are asymmetrical, with the high end being larger than the low end (e.g. +1.0/-0.5), and the inside tolerances are symmetrical to the same absolute value as the low end of the outside dimensions (e.g. +/- 0.5 to match the first example).

1. This is verbatim how it is listed in the standard.


texts: What is the formula to work out time to remove water from an open vessel with vacuum?

texts:
We have an open container sitting at 1000mm off the ground and a receiver tank sitting one metre above it. Container holds 400l of water and is connected to the receiver by 80mm id pipe. I was planning on using extraction fans sitting in the open end of the receiver to create a vacuum to remove the water.

What is a formula I could use to work out how inHg needed to be produced by the fans to remove water in x amount of time?


texts: Why would a bearing plate that further concentrates load onto small surface be used?

texts:
Here's a photo of a bearing plate where a bridge reinforced concrete beam meets the earthfill

The bridge span is about 20 meters long and consists of two reinforced concrete beams each resting on two bearing plates like the one shown - one plate for each end of each beam, total four plates. The bridge holds a railway track designed for 25 tons per axle cars. The bearing plate is made of cast iron (or maybe steel) and consists of two large parts joined through a hinge.

25 tons per axle cars means the bridge bears something like several hundred tons when a train is passing which we can assume causes at least one hundred tons per bearing plate shown. Yes, I just ignored the bridge weight.

Not only the plate upper and lower surfaces are rather small but the plate further concentrates the accepted load and transfers it onto the hinge through even smaller surface. Basically this rather small hinge alone accepts more than one hundred tons. And this is designed on purpose.

Why is the load deliberately concentrated instead of being distributed or at least transferred through some part with uniform section?


texts: Low pressure Diesel pumping with High pressure Gasoline pump?

texts:
We are in desperate search of suitable pumps for one of our applications.
We need to be able to pump Diesel fuel in a range going from 5bars to 125bars.

To do such thing, I've been looking at Bosch HDP5 gasoline direct injection pump (and it's prop valve conveniently attached).

Ok now... two problems :

I have doubts about it's behaviour at low pressure (5bars)
It's a gasoline pump and we plan to pump diesel

Structurally, it's a piston pump and my limited understanding of it don't see where the problem could be in pumping lower pressure than it's max.

And as far as diesel fuel go, it's got a higher lubricity so I don't see it being a problem either...

But being far from an expert, I'd like to have your feedback on it.

The other option would be to use a Bosch CP1 or CP3 which is a high
pressure diesel pump.
Now the fuel is right but the pressures involved are way higher than we need. The pressure compatibility question still stands...
And the last option would be to use a simple External gear pump such
as the Bosch Rexroth ones but also derating them a lot in terms
of the pressure and putting diesel fuel in it...

They are also given for a minimum viscosity of 5mm²/s which is pretty much the viscosity of diesel fuel at ambient temperature, which is a problem since it is usually heating up with time (return/bypass system)
I can understand the limitation of pumping a liquid with too high a viscosity but I have trouble seeing where it could fail pumping a liquid with too little viscosity.

Thanks for your inputs!


texts: Maintaining constant speed of a CVT engine during a slope

texts:
I am not sure if this question is related to this community. But nevertheless. I work on CVT engines, I had a new idea of modifying my controller during a slope or a gradient on the road so that the Vehicle speed does not take a hit.  I have a radar attached on the vehicle, which gives me information about an upcoming slope. I.e., at what distance is the slope (meters) and percentage of the slope (100% being a 90deg wall).

Before I continue, I need to mention that this entire discussion is in the Cruise Control mode. That is, the controller maintains the vehicle speed irrespective of the engine RPM.

The first approach I did was slowly increasing the engine RPM when the slope approaches so the vehicle speed does not take a hit. Below is the simulation I have done.

1) The red 1 is where I simulate 5% slope and the speed drops by around 10%.

2) The red 2 is where I simulate 5% slope again but before the slope, I slowly increase the Engine RPM so the vehicle speed drops only by 4%.

From this, I do conclude that increasing the Engine rpm is a good method. But I do it without any proper math behind it (how fast or how slowly I should do it). I want to implement it with a proper logic and math included. If anyone can help me with the proper math or guide me in a proper direction, I'd be grateful


texts: In a reinforced concrete detail drawing what does 'reinforcement to be GK 60' mean?

texts:
Consider the following extract from a British reinforced concrete drawing from 1970:

It states that 'REINFORCEMENT TO BE G.K 60. UNLESS STATED OTHERWISE'

What is the meaning of GK 60? What property of the steel reinforcing bar is it referring to? To which standard does it pertain?


texts: How do I calculate the best mass for the highest linear speed?

texts:
I have a motor whose specifications say that its torque is 190g*cm. If I have the formula for the mass of the wheel vs radius, is there any way I can find the radius to get the best linear speed?

The formula that relates mass and radius is

$m=1.14r-0.948$

where the m is mass in grams and r is radius in cm


texts: What Is The Liquid Depth Inside The Tank?

texts:
I know that $P_{total}=P_{gauge}+P_{atmosphere}$, so $P_{gauge}=P_{atmosphere}-P_{total}$

$P_{atmosphere}=101.325 KPa$ and $P_{gauge}=0.2 psig=1.38 KPa$.

$P_{gauge}=(0.8 \times sin{30})(900)(9.807) - (900)(9.807)(h)=1.38 KPa$

This implies that $h=0.4m$, however the answer is $0.24m$.


texts: Meeting point of turning wheels with rear wheels

texts:
I was watching this video about how steering on a vehicle. It states:

  If you track the meeting point of the left and right wheels, you can see that the meeting point always lies on the rear wheel line.

I have a few questions about this:

If the car is longer or shorter or wider or thinner, the meeting point of the left and right wheels would not be on the rear wheel line. How then is the steering setup such that the meeting point is always in line with the rear wheels? Is there a process for determining it?
Below is a photo of the meeting point not aligning with the rear wheels:

Why does the meeting point need to be in line with the rear wheels? Would the wheels skip or slip along otherwise?


texts: What does it mean for a machine design to be "kinematic"?

texts:
I've seen the term "kinematic" used qualitatively to describe machines several times in books and on YouTube. I think I understand what kinematics is as a study, but I'm not sure what people mean when they say a structure or machine "is kinematic".
Here are two examples:

Multiple times I've seen people describe a tool with three feet as being kinematic. As in "This height gauge has three points of contact with the surface plate which makes it kinematic."

In "Precision Machine Design" there's a paragraph on machine structure where the author says "If the design is not kinematic, bearings can become overloaded by the forced geometric compliance between the structure to which the bearing rails or races are mounted and the smaller structure of the platten or spindle."


texts: ADAMS/View - how to plot part orientation?

texts:
it is a simple question but I am new to this software. Both in Postprocessor and within Measure Characteristic options there are only angular velocities and accelerations - and no angle (orientation) itself. I saw Angle and Orientation Measure options but this must be something more advanced, since all I need is generalised coordinate of a part.

Also, is it possible to obtain set of generalised coords against time in table form instead of plot? If so, please explain how.

Thank you in advance,

Maverick


texts: Why is there no widely-used standardized unit for indentation hardness?

texts:
The last hundred years have seen a great degree of standardization of units, and the expression of units of measurement in standardized, instrument-agnostic, objective terms, often in the SI units.

So I wonder why this has not happened in the case of the indentation hardness of solid matter.

It seems that the measurement of indentation hardness is fragmented into one scale per instrument, with one or more instruments being customarily used for each material, and it seems like the scales are mostly semi-qualitative and probably non-linear -- and they make it difficult to compare dissimilar materials.

Off the top of my head, I can name:

Rockwell B: Used for soft steel, mostly.
Rockwell C: Used for hardened steel and similar materials
Brinell: One of the more quantitative-seeming scales, but uses an instrument that has some downsides. Used mostly for nonferrous metals and soft steel.
Shore 00 and A durometers: Used for elastomers and soft gelatinous materials
Shore D durometer: Used for "hard" plastic
Knoop: Uses a weird-shaped indenter, usable for metals but mostly used for ceramics and other brittle stuff.
Vickers: uses a pyramid-shaped indenter but not the same one as Knoop, apparently generates quasi-SI hardness measurements but isn't that widely used.
Mohs Scale: Incredibly nonlinear empirical scale based on what materials can indent each other

Is it just because of the "There are now 15 competing standards" issue? Or is there a definitional problem in the concept of "indentation hardness" that makes it hard to reduce to a single value?


texts:
In my lab we use a number of materials which are hygroscopic and must therefore be stored in a dry environment. For that purpose we have numerous dry cabinets very similar to the one shown below (Amazon link here).

These cabinets run on electricity, do not require  desiccant, and do not have a water outlet such as one finds with home dehumidifiers, yet they are able to maintain low relative humidity (RH) values of < 40%.  The temperature inside the cabinet is also the same as (or very close to) the temperature outside of the cabinet, and there are no other connections aside from the electrical plug.

How do these cabinets maintain such low humidity values?
Assuming they are removing water from the air, where does the water go?


texts: Calculating discharge on the pipe diameter and the pressure?

texts:
Is it possible to сalculate discharge / flow rate on the pipe diameter and the pressure (for constant pressure)?

For example:

Pressure_internal = 5 bar, Diameter_pipe = 36 mm, Density_water = 1000 kg/m^3

Bernoulli's Formula (online calculation):

$$\frac{\rho v^2}{2} + \rho g h + p = const$$

$$v \approx \sqrt{(p_i-p_a)\frac{2}{\rho_w}} = \sqrt{(5 \mathrm{bar}-1 \mathrm{bar})\frac{2}{1000 \frac{\mathrm{kg}}{\mathrm{m}^3} }}=28.284 \frac{\mathrm{m}}{\mathrm{s}}$$

Then the discharge should be (online calculation):

$$Q = Sv = (\pi r^2) v = \pi * (18\mathrm{mm})^2 *28.284\frac{\mathrm{m}}{\mathrm{s}} = 1717.81 \frac{\mathrm{l}}{\mathrm{min}}$$

But these values are very far from reality. How can I perform a calculation correct?


texts: Why did the Soviet Alfa-class submarines have a titanium hull?

texts:
My limited knowledge in engineering tells me:

Titanium is expensive, stronger and heavier than aluminium, lighter and weaker than high yield steel.
The most significant advantage of titanium is the good strength to weight ratio.
In case of submarines, weight is not really a big concern, as long as the weight is manageable (less than the displacement and bigger than displacement - maximum ballast mass).

The mentioned points exclude the use of titanium. Since the designers decided otherwise, and surely had some good reasons, I wonder where my misunderstanding is?


texts: In terms of fully saturated vapour and liquid for water. Why in a real world heat pump cycle for example may the water not exactly reach these saturation lines as indicated in an ideal cycle?