texts: How to ensure natural ventilation through a shaft?

texts:
I have a small shaft, 2.5m wide by 4m deep, sunk into the ground. Due to explosion protection I should ensure "natural ventilation" - this is the termgiven in the relevant ordinance, no air flow specified. As the shaft is sunk into the ground, in the summer months it will always be colder than the air above. I see no way to ensure passive ventilation, so I will need a small blower.

Or am I wrong and there is way to ensure natural ventilation?


texts:
the Bristol Motor Speedway is 0.533 mi long racetrack. The road is banked and circular. The straights are banked to 6–10° and turns to 26–30°. I have made a small diagram for ilustration.

Before the cars fully enter into the turn, they have to pass through a section of the track where the banking graually progresses from 10° to 30°. Does anyone knows how is determined the lenght of the road between two levels of banking?


texts: How to set measure display units in Solidworks drawing?

texts:
I have already set millimeters in document propertis, nevertheless the display units are meters

Why and how to fix?


texts: Is there is vanadium-free high speed steels?

texts:
Vanadium is present in all high speed steel grades. unfortunately vanadium not only very expensive but is also a will known cytotoxic metal. some workers get severe persistent cough lasts for months for just contact with vanadium containing dust or vapors which are present in any workshop !!

I searched a lot but can not find any high speed steels without vanadium ,  except some research grades which replaced vanadium by niobium but unfortunately  niobium forms very coarse carbides which are so detrimental to steel toughness.

so my question is if there is vanadium-free high speed steels or any temper-resisting steels with similar hardness exist ?


texts: Circuit that multiples two numbers together?

texts:
Design a combinational circuit that multiplies two numbers together, and outputs the result.

The biggest product will be 3 * 3 = 9.
Four bits to represent the product.

0: 00
1: 01
2: 10
3: 11

I need a 4 bit register for the outputs, right?

How do I start my truth table? like this?

A B C D | Output | AB | CD
0 0 0 0   0         0    0

and so onto minterm 15?

How will I form the expressions from the truth table?
I know how to solve with a K-map, but I'm having a hard time visualizing and building it.


texts: Calculate press tonnage from impact momentum

texts:
I have an application where a person drives a bush into its housing using a hammer of about 3kgs.
Suppose the same application is to be done with a hydraulic press,is it possible to calculate the press tonnage(probably using an approximated calculation of the kinetic energy of the hammer).
TIA
Thomas


texts: 4 bar mechanism how does this 4 point method work

texts:
I'm wondering if somebody could explain the 4 position method a bit more understandably. I am trying to follow the explanation in here. What I fail to understand is how does the actual fourbar linkage in this case look like?

Image 1: Situation described.

From the image and description I gather that:

F is one of the ground joints (pink)
The pink Circle is length of that link (link 3)
P23 and P'23 are location of next link joint, and thus the length of that link is F to P'23 minus the pink circles radius (link3)

However what I don't understand from the description is where the other ground joint is. Does it happen to be M'? But that seems awfully short when looking at the demonstration piece? What about P13?


texts: Radar/lidar for detection of humans in indoor rooom

texts:
I have a room (waiting room) about 10x10 meters and I would like to locate people in there. Celling in the room is really high, so I can place the radar above in any height I want. My questions:

Is it possible to use some ready/made radar/lidar solution to detect what seats in the room are currently used by people?

Is it possible to detect people moving in the room on the fly (~30fps)?

Is it safe to use radar on humans?

I know there are papers on this topic. However, I am not sure if there is any reasonable inexpensive solution for ordinary people. Something I can plug in PC and read raw data to process in any software I develop.
Further info:
There will be cameras. This measurement should be a complement to the camera machine vision to make it more reliable. I have experience with development of machine vision systems in difficult environments (mainly industry environment) and they have never worked as intended.
I also thought about tensometers, accelerometers, or microphones in the chairs to just locate sitting persons, but I would like to avoid collecting 20-60 channels.


texts: what is issue with my room brick wall? How can i solve it?

texts:
I have seen a sort disformation on wall of my room I have attached snapshot of both inside view(from inside room) and out side view(that is out of room)

inside view is below

out side view is below


texts: What object characteristics may cause significant distance measurement deviations in Sharp optical sensors?

texts:
Not sure if this is the right place to ask this question, but anyways. I'm not very fond of circuits and stuff, but I've got a test question I really need to answer. The question is in the title, possible answer options are:

Fibrous surface
Temperature
Thermal conductivity
Velocity
Opacity
Average density
Color
Electromagnetic radio waves radiation (as far as I understand, the question suggests that we're speaking about waves produced by the object that we are measuring distance to itself)

Multiple choices are possible. I didn't manage to find an answer on the internet, so I hope someone can help me here.


texts: Force exerted on the CPU socket by heatsink

texts:
I am currently designing a replacement bracket for AM4 CPU coolers that will be compatible with different cooler models and allow them to be installed facing different directions, as AM4 socket is non-symmetrical, and the current design looks like this:

This a draft and I want to use FEM to reduce the amount of metal covering, so more air could get through and also cool the VRM's and other chips in the CPU vicinity, but to do that I need to know what is the maximum force I need to design for. I think calculations using just the mass of the cooler would not be accurate, as I also have to take into account the force exerted by screws that are used to hold heatsink in place.

tl;dr: how much force should I account for when designing mounting bracket for CPU cooler?


texts: How can I verify my engineering work experience without having worked under a PE?

texts:
First a little background, I've been working in Michigan as an engineer since getting my BSME in 1998 (I graduated with my MSME in 2010). I've worked for a number of companies in a variety of industries as an engineer, but never under the direct supervision of a licensed PE since all of the work I've done has been considered under "industrial exemption".

Now however, I'm becoming less interested in simply being an employee and more interested in working for myself and being a PE would be advantageous. I'm reasonably sure I can pass the exam (with copious amounts of studying, naturally), but my concern is getting my experience verified. The PE's that I know, I've never worked with, either as a subordinate or as a peer.

Has anyone had difficulty finding enough PE's to verify their experience when getting licensed? If so, were you successful in getting your experience verified? How do you recommend finding PE's to verify engineering work experience?


texts: I am attempting to determine which material has been used in a spring. I know that the spring is ferrous. However, I would like to know whether the spring would have been heat treated.


texts: Difference between an angle grinder and an abrasive saw

texts: It seems to me that abrasive saw is a term mainly used in the US (the Wikipedia article on it has no links to pages in any other languages), whereas angle grinder has some 20+ translations. So, can someone clarify whether discs for abrasive saws are interchangeable with (thin/cutting) discs for angle grinders and what other differences there might be between these two tools (even if just in the US)?


texts: Was Isaac Newton's solution to the problem of solid of least resistance comfirmed in space programs?

texts: I was very surprised when i found out that Newton's solution to the problem of solid of minimal resistance was a body with somewhat strange nose cone - the end of the nose cone is  a plane perpendicular to the body's axis. So my question is, was Newton's calculation confirmed and used somehow by space programs?


texts: I'm pursuing Mechanical Engineering and i need to learn AUTOCAD, is there any site where i can download free video tutorials


texts: What instrument does a surveyor use to accurately find North?

texts: The obvious answer is a compass. I have an old (1952) transit that has a compass which seems to be accurate to 15'. However, that doesn't seem too incredibly accurate at all. Furthermore, most modern digital theodolites I see don't appear to have a compass (correct me if I'm wrong). I'm curious how a surveyor actually finds north with high accuracy. Are there digital theodolites or other instruments with compasses? Are north-south lines set out with GPS? I'd appreciate any insight.


texts: How to generate a repeating semi-circle waveform using a mechanical linkage

texts:
How can one, in a smooth way, produce a semicircle wave, as opposed to a sinusoidal wave ?
Imagining the machinery and linkages behind the movement.
I mean the trace. For example a point fixed in wheel of a car may engender a cycloid. Others curves may be a Cyclogon, or a curve produced by a point fixed inside a sharkwheel, when rolling(not gyration).
The motivation behind the question, it is because in the usenet, there is a user called Archimedes Plutonium that has semicircle waves instead of sinusoidal.
I have curiosity if it will be possible to produce such kind movement in at least one way. The mechanism that produce the curve does not need to be contained inside a plane.
Other way of thinking on it may be in the sense of producing such movement in a non-trivial way, similar to producing a straight line using the Peaucellier–Lipkin linkage.

Question re-phrased by @Transistor:

Figure 1. A cycloid can be generated by a point on the circumference of a circle. Image source: Britannica.
Can a similar waveform consisting of a series of semi-circles be generated by a mechanical linkage?


texts:
I have to solve the differential equation for radial disks, and therefore I need the shear force distribution. The disk is rotationally symmetric.
I want to use the superpositions principle and set 3 areas.

$0 \le r \le D_i / 2$

$D_i / 2 < r \le k / 2$

$k/2 < r \le D / 2$

The shear forces are for area 1
$\sum F_z = 0$
$F_{rz1} \pi r - \frac{\pi r^2}{2}p = 0$
$F_{rz1} = \frac{p r}{2}p$
Area 2
$0 =  -F_{rz2} \pi r + F_s \pi k $
$F_{rz2} = F_s \frac{k}{r} $
Area 3
$0 =  F_{rz3} $
The solution confirms $F_{rz1}$ and $F_{rz3}$ for me. However it states that only after $F_{rz3}$ is known one can solve for $F_{rz2}$ for the area $D_1/2 < r \le D / 2$
The solution should be $F_{rz2} = F_s \frac{k}{2r}$
Did I cut correctly?
What am I missing here?
I know realized I had to insert $k/2$ instead of $k$ and then I get the correct solution for
$0 =  -F_{rz2} \pi r + F_s \pi k/2 $
$F_{rz2} = F_s \frac{k}{2r} $
However the question that remains is, why the hint to extend the area? Why is it not possible to calculate $F_{rz2}$ before $F_{rz3}$ when it apparantly is possible?


texts: can base current be far less than collector current?

texts: I'm using an NPN transistor to pull the gate of a P-channel FET low. I'm driving the base with 3.3v and a 10k series resistor. I have a 100k resistor in series with the collector and the gate of the P-channel FET which is then pulled up to 5.4v with another 100k resistor. So my base current is about 20x my collector current. Any trouble with that?


texts: How to calculate new focal plane position when adding a lens to a lens system?

texts:
I am currently struggling with some lens equations. I hope this is the right place to ask such questions.

What I'm trying to accomplish is to add a separate single lens to a camera setup and calculate the new focus plane (See the added image).

To calculate the new focus plane I am assuming the 16 mm Kowa lens (on the camera) to behave like a thin 16 mm lens. Using simple lens equations, I then calculate how adding the separate lens would shift the focal plane.

However, the results I get from these calculations do not correspond to what I see in my experimental setup.

What am I doing wrong? Does substituting the Kowa lens for a thin 16 mm lens in my calculations make that much of a difference? If so, how could I calculate this without knowing exactly what is inside of the Kowa lens?

Writing out my calculations here would make this a wall of text, so I left them out. If they are required though, I would be happy to add them.


texts: Why adding less than optimal level water but just enough water to drench the sausage in general isn't the quickest way to cook?

texts: The exact reason why adding less than optimal level water but just enough water to drench and dive the whole sasuage in during boiling in a pot isn't the optimal quicking cooking method? My intiuion is that adding a swimming pool of water or a few drip of water won't cook the sasuage.


texts:
Why is the jacket or sheath of fibre optic endoscopes always black?
Is it just a convention, or is there a more logical explanation for this?


texts: Looking for a gear similar to bicycle freewheel

texts:
I have an engineering application where I would like to use a single 24v DC Stepping Motor to power two different axles of opposing direction. Basically when the motor turns clockwise, Axel A will spin and Axel B will be stationary. When the motor turns counter-clockwise, Axel A will be stationary and Axel B will spin.

I need it to be as cheap and simple as possible. So far, the best solution that I could come up with to accomplish this is by using two gears similar to the bicycle Freewheel / Freehub. The problem is, I cannot for the life of me find a gear that is similar to that application, but for uses outside of bicycles (possibly because I don't know that specific gear's name). Can anyone recommend a gear or something that is similar to the application that I need?

I have a general idea of the function that I need, but I don't know the name of this type of ratcheting gear.


texts: Pressure drop across column in gas phase: what changes?

texts:
If you force high-pressure gas through a packed-bed, the gas pressure drops. However, the ideal gas law states:

$$P = \frac{RT}{v}$$

so for an ideal gas, the pressure drop must be associated with a property change of the gas itself as it moves through the packed bed. My question is: how does a typical gas moving through a typical packed bed adjust its pressure: is it primarily by a decrease in temperature or by an increase in specific volume?


texts: Why rotation factor of bearing for inner ring is 1 and for outer ring is 1.2?

texts:
V is a rotation factor to account for the difference in ball rotations for outer ring rotation vs. inner ring rotation.

V = 1 for inner ring rotation
V = 1.2 for outer ring rotation

From Shigley's Mechanical Engineering Design - Ninth Edition

What is the reason behind this?


texts:
Alright so this is my question lasses and lads: a disc with a mass moment of inertia 0.125kgm^2 about its central axis is rotating at 180rad/s about the axis. What is the angular momentum of the disc about the axis?
Soo, this is what I did: $\omega \cdot  I_o= 180 \cdot  0.125$ and got $22.5[\frac{kg m^2}{s}]$?
But isnt that too easy?
Can someone tell me if they agree or maybe if I am going wrong somewhere?


texts: Column Buckling: Which is more useful to plot; Buckling Load vs Slender Ratio, or, Stress vs Slender Ratio

texts: Both have a linear relationship, is there any merit in plotting one over the other?


texts:
I am researching about ways to continuously determine black spots (size 50+ micron) in our product stream. This stream consists of imperfect spherical polymer beads (size 3 mm) of different materials (ABS, SEBS, etc.) and colors (opaque and transparent). I want to be able to count them as well as characterize them (size).

I have been looking into a couple of options:

Visual observation using computer vision
NIR spectroscopy:

What other options do I have and which one is most effective (preferably also least expensive)?

Update:
In our production plant we produce at 500 kg/hr and the pellets are transported along a conveyor as a monolayer of around 50 cm width at around 5 cm/s. However i can imagine that is simply too complex to begin with and i am not opposed to having a secondary stream with much lower massflow and then upscale in a later stage or just have labscale setup to check samples taken of the productstream. I am ok with an approximate count as long as it is reproducible. I would also be ok with initially only detecting 100+ micron black spots.


texts: Plasma torch air speed in transferred vs. non-transferred arc

texts:
My question is does anyone know if there is a difference in gas speed between transferred arc and non-transferred arc plasma torches? I am referring to the speed that the gas leaves the nozzle at. I have not been able to find any information about this online.
Thanks!


texts: How do you determine how many pumps you need in a pipeline?

texts: I am working on a pipeline design scenario and I am trying to determine how many pumps I need. In addition to this diagram, I'm given a flow rate range and an acceptable velocity to also determine the diameter of the pipeline, which I have (using a Turbulent Flow III approach). The part that I am stuck on is determining how many pumps I need. Any help will be very appreciated


texts: Could car waste heat be used to lower drag?

texts:
If the waste heat was moved to areas of lower pressure such behind the car-green area-

Could this reduce the drag from these areas of lower pressure.  From what I understand this hot air would increase pressure in those areas but equally hot air is less dense so would it increase drag?


texts: Crude Oil Velocity Flow Within Rock-Soil Matrix

texts: In order to run some numerical simulations, I would like to know some rough values (estimates) of the velocity at which the crude oil flows through the rock or soil matrix from which it is extracted. I found lots of data about production rates (bpd), which is the main parameter of interest from the engineering point of view, but so far, nothing about this technical aspect. One last thing, I am an outsider (civil engineer and applied mathematician), not an specialist.


texts: Why do different air compressors have different flow rates?

texts:
I bought a little compressor that does 2.6 SCFM at 90 PSI. But I have a tool that needs 10 SCFM at 90 PSI.

If you imagine PSI as voltage, and flow rate as amperage, then it might follow that the only thing limiting the flow rate is resistance. If so, why don't all air compressors reduce air resistance to achieve the same high flow rate?


texts: Are there any negative aspects to using baseband frequencies in radar systems?

texts:
Is there any application or circuit design for RF radar systems to use directly the transmitter frequency for the receiver side.

From what I've seen, a mixer is always used to get the frequency difference to calculate the distance. Is that still applicable to use for Ground Penetrating Radar systems?

What determines the frequency required for scanning depth and size of the objects to be detected?

As far as I know, the use of higher frequency results in more finer details but it's difficult to penetrate deep into ground. I guess the maximum of 1GHz is enough to penetrate about 1 meter into the ground, of course depending on the conductivity of the soil. But I am not sure which specifications I need to process that much frequency. How much bandwidth do I need to use?

One said that you need to have a bigger bandwidth to have a higher resolution for depth information. But I am not sure if I use 1GHz do I need some sort of bandwidth about 2 GHz or sth. That much bandwidth supplied to ADCs are about 3000 USD and I am not sure if I am looking to correct direction.

Can you guide me a bit?


texts: Circuit to provide position control for double action hydraulic actuator

texts: I was wondering how to construct a hydraulic circuit to control a hydraulic double acting piston/actuator enabling the electronic control of the piston extension. I have found the following pneumatic solution. However, I am not sure if this can be applied to hydraulics too.


texts: Can aggregate gain almost 200 grams of water when submerged in water for a day?

texts:
I'm doing this special project where I have to make concrete using a Martian simulant provided from a commercial source.

I measured it as 500 grams initially, then submerged it in water for a day. It came back as 727 grams, meaning that it gained 200 grams of water, as it is now in its saturated surface dry state.

$$A = \dfrac{W_{SSD} - W_{OD}}{W_{OD}}\times100\%$$

Following this equation to measure the absorption value, it would mean that the value would be around 50%, which is very high. Usually, normal aggregates on Earth have an absorption rate of around 10%!

Is there anything that I may have been doing wrong? I am very skeptical of my results


texts: why is the auto ignition temperature of petrol is more than the diesel even though petrol is more volatile than diesel?

texts: My question points that why the auto-ignition temperature of petrol is more than diesel even though petrol is more volatile and got least flash point than diesel.


texts: Is it possible to generate energy from indoor draft by opening windows on opposite sides of the building?

texts:
Wind flow always generates naturally when I opening windows on the opposite sides of the building.
Is it possible to put turbine on the way and generate electricity from that?
It could be optimising by building a tunnel and protecting walls for better indoor/outdoor temperature differences.


texts: Help with cantilever table top questions

texts:
I'm hoping someone can help me with some questions to know whether or not the table can be supported by this design and how to calculate the length of the support runners and the width necessary to prevent tipping/rocking along the width as well.

Table length and width ~90" x 36"

Angle of the cantilever arm (terminology?) either 130 degrees or 50 degree

Which of the two designs from the elevation view would provide better support (could I use either as long as runners are long enough?) Which would require shorter runners [longer overhang]?
What would the minimum width between the two support arms would I need to prevent horizontal tipping?
How do I calculate tipping weight on the end of the table (opposite of the support)?

Material is wood. I found some figures for "E = modulus of elasticity" and for the wood I'm using it'd be between 1.6-1.7 and the user posted this note:

  units of measure are psi, values must be multiplied by $10^6$.

This is all beyond my math skills, but am willing to try and learn!


texts: Why are fine metal filters made of meshes?

texts: Given that we have mechanisms of performing photolithography at 10nm, why are metal filters often meshes? Wouldn't it make a lot more sense to buy a single chunk of metal, and use the UV lasers to poke lots of N micron holes in it?


texts: can simply beating cast material with a hammer inside a mold improve it's strength

texts:
I asked my materials science proffesor if forging a cast part (inside a mold to prevent shape change) can increase it's strength to that of a forged part.
She told me to find out myself and tell the group next lesson. I googled for a bit on post casting treatment but haven't got a clear answer to my question. Is it possible?


texts: I can't even see how can i solve this truss question

texts:
I can't even see how can I solve this truss question
I'm an engineering student, our professor assigned us this truss problem.
I have found an answer saying that it is a zero member.

I have tried but I couldn't even see where should I start from.

update [answer attempt]

i am working on this problem but i couldn't find any value once i reach a joint with 2 unknowns

like this joint for example [B]
[]3

i have even used the momentum equation but i can't go anymore


texts: How to calculate flow coefficient to choose a pressure regulator

texts: I'm attempting to choose a pressure regulator(for use with an inert gas) for a personal project I am working on. I know that the inlet pressure will be 2000 psi and outlet pressure of 300 psi. I also need the mass flow rate to be approximately 1 g/s. I've done some calculations with the perfect gas law and got a volumetric flow rate of 415.943 SCCM based on the inlet pressure. The Cv's I've calculated thus far does not seem correct as they are very small numbers. I'm wondering how to properly choose a pressure regulator that can fit these parameters and how to calculate the Cv properly. Any help is great!


texts: What's sort of "sidewalk" pavement is this?

texts:
I was recently walking down a road when a car came my way (I'm an inveterate jaywalker). I moved over to the sidewalk, only to notice it clearly wasn't a sidewalk at all. The pavement looked like this:

The paving stones are embedded into and perpendicular to the ground, making it rather uncomfortable to walk on!

Now, what is the purpose of such pavement? Is this layout meant to improve drainage in case of rain (this is in London, so it's always raining)? But then why pave the ground at all instead of simply using grass or greenery to anchor the soil and prevent erosion?


texts:
I am currently studying Mechanical Engineering and am doing an assignment where I have to design a wire rope tensioner where a wire rope is unspooled from a drum, but the wire has to be at a specific tension when unspooling. Therefore I am looking for ways to put an adjustable amount of resistance into the axle of this drum. I can't find much information on this subject.
Things I've thought of so far:

A mechanism similar to drum brakes in cars (this is however not accurately adjustable and wears out quickly, also heat will form a problem).
Using an electric motor for braking torque (Not sure if this is possible when the wire tension needs to be about 200kN, and what to do with the generated electricity).

I'm curious if you might have some more ideas?
Thanks in advance!


texts:
In common US usage, the heights of tall things are sometimes converted to a "number of stories". The thinking is that people can better compare heights to similar tall buildings that they might have seen.

The US conversion is usually:
$$\text{Number of stories} = \text{Round}\Big(\frac{\text{height in feet}}{10}\Big)$$

I assume that something similar is used in metric countries like:
$$\text{Number of storeys} = \text{Round}\Big(\frac{\text{height in meters}}{3}\Big)$$

I am assuming that like most things that are common usage, this conversion is not correct in practice.

What is a more accurate height of a building story?
How does this cause confusion when comparing the height of a building in "stories" to the actually number of stories?


texts: General formula for calculating torsional and warping constants of built-up section

texts: In order to calculate the elastic critical moment of a laced double I-section, I need the torsional and warping constants. Is there a general formula to obtain this? BS 5950 only has formulas for single I-section. I tried Googling but it seems such information is not readily available.


texts: Getting the damping ratio from a frequency response function v.s. transfer function

texts:
I'm trying to find the damping values of a specimen, based on sweeping the forcing frequency from 0-10 kHz. As shown in the diagram, I measure the input force from the shaker, and the subsequent response using an accelerometer on top. (The steel plate in the diagram has known properties and was used to isolate my system from sources of noise).
Using the force sensor and accelerometer, I have time-series and frequency responses of input force and output acceleration.

This is where my question arises. Can I extract damping from just the response (acceleration), or do I need to do it using the transfer function (output/input)? These give quite different peaks, and damping values. I've attached a picture showing the frequency response of the accelerometer on top, the force sensor on the bottom, and the transfer function.
(The thick black lines represent the average of multiple runs, the red dots are automatically-detected peaks in the transfer function).

Most resources I've seen online use the transfer function, but from what I understand, the response by itself should also be usable (?).
If it's just the transfer function, then is it sufficient to present data in acceleration/force units, or should I convert both to force/both to acceleration such that the transfer function is dimensionless?
Thanks in advance!


texts: basic second order system transfer function - natural period and natural frequency

texts:
I have a question about general second-order system transfer functions. I notice two takes on this transfer function. One has a denominator of:

$$\tau^2 s^2 + 2\zeta\tau s + 1$$

where $\tau$ (tau) as they defined it - is 'natural period of oscillations' (not time constant), which is seen (for example) in the formula at this link here.

And then there is another transfer function (seen in other control engineering textbooks) with a denominator of:

$$s^2 + 2\zeta w_n s + w_n^2$$

Now, if I divide the first expression by $\tau^2$, I get:

$$s^2 + 2\frac{\zeta}{\tau}s + \frac{1}{\tau^2}$$

So I can now compare $s^2 + 2\zeta w_n s + w_n^2$ and $s^2 + 2\frac{\zeta}{\tau}s + \frac{1}{\tau^2}$.

Equating the constants of those two expressions above, I get:

$$w_n^2 = \frac{1}{\tau^2}$$

which boils down to $w_n = \dfrac{1}{\tau}$ or

$$\tau = \frac {1}{w_n}$$

Now, the natural period of oscillations $\tau$ is supposed to have units of time (eg. seconds). And angular frequency $w_n$ is supposed to have units of radian per second.

The actual mathematical relation between angular frequency and period is supposed to be $w_n = 2\pi \frac{1}{\tau}$, where $1/\tau$ is $f_n$ (the cyclic frequency in Hz).

The comparison of the two second order transfer functions leads to $\tau = \frac{1}{w_n}$. But formally - the relation between $\tau$ and $w_n$ should actually be $\tau = 2\frac{\pi}{w_n}$.

That is $\tau = \frac {1}{w_n}$ versus $\tau = \frac{2\pi}{w_n}$.

The question is - why is the above mathematical conflict occurring? A factor of $2\pi$ out.

I'm definitely missing something here. But would definitely like to understand the missing link.

Could it be that the $\tau$ seen in $\tau^2 s^2 + 2\zeta\tau s + 1$ has been incorrectly defined as the natural period of oscillations?


texts: defining the dimensions of a bucket elevator chain link

texts:
how to define the shape of a heavy duty chain link when the pitch of the chain and the traction load that the chain is subjected to is known?
lets say i consider the traction load as the maximum load the chain can support, how can i do the back calculation from that to find the required dimensions?


texts: There are many places I see a knob used to set the vertical position of an object (like in a microscope stand), but how does it not just simply slide down due to gravity once the knob is released. It's not like they first have to pull/push out the knob before turning it so as to lock it first. Instead once you turn it, it just remains in that position. I believe it's a rack and pinion mechanism, but I don't understand how it locks itself in place after it's been set.


texts:
I am using Engineering Equation Solver, and it has been telling me the units of my distribution are inconsistent.
According to a the book I am reading, I think it should be unitless (as it is a probability).
However EES, says
$$ h = \frac{k}{c}\cdot \left(\frac{v}{c}\right)^{k-1}\cdot exp\left(-\left(\frac{v}{c}\right)^{k}\right)$$
In theory, v and c have the same units [m/s] and k is unitless. I do not understand why the units are not working out.
Hope you can help me out.


texts: choice of steel plate for simple application

texts:
I am an occasional hobbyist "DIYer" (not an engineer) who needs help choosing a steel plate for a small home improvement project:

I will use it to create a 20" circle, suspended from a bolt at the center. It should be able to hold 350lbs pretty much evenly distributed over its surface.

There is already a generous safety margin built into the 350lbs estimate.

What is a reasonable choice of steel plate (steel type + thickness) for me to go with?

Just to be clear, this is not a critical application -- ie, no one will be hurt (fall/get squashed) if this fails.


texts: What makes a good piping and instrumentation diagram tool?

texts:
A while back, I asked this question for a free Piping and Instrumentation Diagram (P&ID) software on softwarerecs.SE. I described the core features of a P&ID software thusly:

  Where a proper P&ID software differs from a drawing tool like Visio or Diag is that the P&ID tool can output a parts list listing all components and connectors. Components and connecting lines can have additional specifications (like the power and type of a motor, or the size and material and pressure level of a pipe). This specifications can then be written to the material/component list.

Confession time: I've never worked with a P&ID software, this is just what I think (from poring over plans and counting valves) would be really helpful.

What core features do working engineers need from a modern P&ID tool?

Edit to clairfy: I'm not looking for a specific product, I'm looking for the core features that make a tool great.


texts:
First of all, this is not a homework question.
I simply have a hard time finding relevant sources or help. Therefore, I am asking this question here. Hopefully, someone can help me.

I would like to calculate the analytic solution of the deflection curve of the L-Shaped cantilever beam as shown in the following image:

It is difficult, because the force acts out of the plane, and will therefore induce an out of plane bending of the cantilever. The cantilever will exhibit torsinal and bending stress.


texts: How do I cut a crack into a polymer/plastic?

texts:
We need to cut a very thin crack into a polymer plate for a research project. The closest thing to what we are looking for is Wire EDM but since the polymer we are using is not conductive we cant use that method. Any suggestions? Is there an insulator version of Wire EDM?

Edit:

a is the crack length and we want the crack thickness to be less than    1 mm. It should be as thin as possible.


texts: Investigating the potential of generating energy from moving water in pipes on a water production site

texts:
I work on a water production site, we have a staggering amount of water flowing, much of which is just using gravity pressure and feeding into reservoir tanks. (flow on various sites ranges from 100 litres per second to over 1,500).
I am wondering if there is a potential here for energy recovery?
Either a kelvin thunderstorm (unlikely I guess but would love to see why it may or may not work) or a waterwheel generator inside the pipes or at the outlet?
But I am struggling to find any real figures to help me ascertain what kind of power this could generate and if it would be feasible / cost effective?
any input would be greatly appreciated.
If an example helps to give some base figures, I can think of one specific pipe that drops about 10 meters and has an average flow of 240litres per second. the pipes diameter is about 1 meter


texts: Is it true that computer chips "float" inside of the computers ? Can someone give me references(books, articles, papers...) about that fact ?


texts: If production line is for production, what is the name of the line for decomposition?

texts:
A production line is a sequence of processes and operations applied to a workpiece to create a product.
Now consider another line that tries to decompose a given product, and extract raw materials from it.
For example, an old car gets in. In the first workstation, tires are removed. In the second station, glass is removed. In the third station, wires are removed and so on.
What would be the name of this line?


texts: Dynamics of structures: combined plane stress and plane strain conditions

texts:
Problem statement

For an engineering project in school, we are checking the stability in the longitudinal direction of an apartment building, taking into account the dynamic effect of earthquakes. For this, we are making a two-dimensional finite element model in Matlab. We have to assume that:

There is a plane stress condition in the columns
There is plane strain condition in the floors and walls.

The stability of the building is guaranteed:

In the transverse direction: membrane action in the columns and the walls.
In the longitudinal direction bending stiffness of the connections between the columns, the floors and walls.

The picture attached shows an apartment building with properties:

Nine bays (each 5 m width and 0.25 m thick)
Six floors (each 3.5 m height and 0.25 m thick)
Depth of the building is 12 m.
The building is supported by twenty columns (each 1.6 m width and 5 m height)
The thickness of the columns has still to be determined but should lie between 0.2 m and 0.8 m.
E = 35 GPa
Coefficient of Poisson = 0.25
Mass density = 2500 kg/m³
Finishing layer of 350 kg/m²

Plane strain and plane stress can be modeled by means of beam elements, provided that in the elements with plane strain condition adjusted values E' and ν' for the Young’s modulus and the coefficient of Poisson are provided:

E'=E/(1-ν^2) and ν'=ν/(1-ν)

Questions

We are struggling with the implementation of the plane stress and plane strain conditions.  We have tried to model this as follows:

Plane strain: We modelled the building with a thickness of 1 m for the superstructure. Therefore, we adjusted the mass density from 2500 kg/m³ to 12 m*2500 kg/m³.  In this way the mass of each element is obtained by multiplying by the thickness and length of the element.
Plane stress: We doubled the stiffness of the column to include both columns at  the base.

This implementation gives not the results we are hoping for. Are there any suggestions for improvement?


texts: Thai Cave Rescue- Why the narrow portions are not being broadened?

texts:
Tham Luang cave rescue incident is taking combined effort of Engineers throughout the world. Various news media is telling currently it is not possible to pass more than one person through some very narrow portions of the cave tunnel (so the boys have to learn diving within cave).

This is a Map by BBC, perhaps from here of BBC; showing the narrow places in cross sections.

Now; my question is; why the engineers are not attempting to use abrasion (with a grinding wheel or such thing) and rock cutting wheels to broaden these "too narrow" parts so that later on 2 people (a diver carrying a boy) can come out at a time?

Is there any hidden risk of attempting so? Is that the cause for not atempting so?


texts: Trim parts against parts in assembly level solidworks

texts: In solidworks , is it possible to trim a part against another part in assembly level


texts: I'm running an FEA on a vessel that has a "splashing water" effect with vibrations.  The problem I'm really coming up against is what kind of Young's Modulus and Poisson's ratio to use for the fluids? - air and water.  I have been successful in using the bulk Modulus, and treat it as uncompressible - i.e. Poisson's ratio of 0.5, but I never used it for vibrational analysis, just static analysis.  Are these still good assumptions in a dynamic analysis?


texts: How does turning off electric appliances save energy

texts:
We all know if we use less electricity we save energy.
But the energy we're getting is result of burning (not necessarily the literal meaning) the fuel. Even if we don't use that energy that fuel is gone forever. (Except saving money on bills)
My questions

Am I wrong in above statement? If yes then how does actually electricity production work so that we're able to save it?

Do power plant (or associate agencies) constantly monitor demand and reduce the production of electricity on real time thus saving fuel (hence energy)?


texts:
I'm trying to find a battery that I can use for a project. Let's be hypothetical for a moment.

I have 5-8 of these Adafruit Servos, connected to this Adafruit Servo Shield. Leaving the Arduino itself out of the equation, how can I calculate the amperage draw that these motors and this shield will pull? And additionally, how can I use that with the Ah of a battery to calculate the time that the circuit could be on and in motion with the battery in question?


texts: Сircuit diagram of a plasmapheresis machine

texts:
I a working on my course project on "Circuit design of Biomedical Devices". The topic is "Plasmapheresis machine". I wouder, if there are any materials (books, patents, service manuals) that contain electrical circuit diagrams (or at least block diagrams) of such machines?
I have found somef service manuals, but they all contain only general diagrams of how to connect some peripheral devices to the machine. But I am interested namely in electrical diagrams.
Thanks in advance!


texts: Difference between partial derivatives and derivatives in physics

texts: Please explain me the difference between $\lim_{x->0}\frac{\partial E}{\partial x}$ and $\lim_{x->0}dE/dx$.In physics I encountered something similar while reading about Newton's Law of Fluids.While in F.M. White its done using partial derivatives.I want to know the physical difference instead of the highly mathematical one. Having said that I am well conversed with the first principle of derivatives.


texts: Injection and lose of fluid injected and pressure drop down?

texts:
I am trying to develop a field by using water injection.

I am facing a problem that the average reservoir pressure is dropping down and the BHP of the production wells dropping down as well until it reach the limit and stop producing.

Therefore, my injection is not achieving its purpose by maintaining the reservoir pressure and the production. The injectors are in the layers 4, 5 , 6 , 7 and 8 While producers are in the layers 1, 2 and 3 Would you please suggest to me how can i maintain the pressure and the production


texts: What are best safety practices for visits to waste water treatment plants (WWTP)?

texts: In my position I'll frequently visit wastewater treatment plants, often when refurbishments work happen. What are best practices I should adopt to avoid accidents?


texts: I'm trying to build my own weatherstation for my home, I want to measure temperature humidity and wind strenght and direction. For the wind I have a question. I want to measure the wind with a ball on top of a stick (schematic), and measure the bending of the stick with some strain gauges. Is this possible or just a crappy idea. And what material would I need for the stick that it bends for low wind forces too?


texts: In terms of calculated stress, strain, displacement etc which method yields more conservative results. Analytical calculation or numeric calculation?


texts: What is the Meaning of To Warm Up an Engine?

texts:
I have both car and motorbike. Just common car and motorbike. My car is Toyota 2005, and my motorbike is Honda 2016, I bough both brand new. Both them are fuel injection. Before them, I owned car and motorbike, but both them were carburetor. With those old automotive, I have to warm the engine up until they reach their stationary. The requirement time will be around 5-10 minutes, depend on the weather and time. Morning in rainy season will be different to day time in dry season, however.

With my new automotive that are fuel injection, my habits still there, I still need to take that time to warm up the engine. But I read in many occasions in automotive news said that for fuel injection just required half and maximum one minute to warm up. For my car, since I start the engine up, it will go to around 1,300 RPM, and required around 7 minutes to become stationary, around 700 RPM. The stationary's RPM is clearly stated at the engine cap, with a yellow poster posted there. For the motorbike, I have no idea as no stationary indicator. But another car, Honda, I saw that it takes shorter time, and one Mazda car I saw just required around half to one minute to warm up, as said in the automotive news.

In my understanding, warm up is intended to warm the engine up slowly to avoid the engine's temperature changes so quickly that of course is not good for the engine itself. So my question is, how that warming the engine could be so different? And what is actually that warming up intended? Several time I tested my car without proper warming up, the result is very bad, something like knocking in the engine.


texts: Differentiating between Two Orthographic Projections

texts:
I came across the infamous control handle assembly in two different books, referencing the views differently. One of the had it like the following photo

The other book labelled the side view in this photo as the elevation (front view).
The question here is how to determine the correct choice of views? I remember from school that this will also determine the dimensioning on the views (in which direction numbers are put, and their relative positions' to the dimension lines), so if somebody could point me to the standard used in settling this issue.

One colleague told me the elevation should be the view with the greatest dimension, but I think the given example doesn't totally agree with this point. I mean there should be a decisive factor because in many machine parts it is not obvious which is which.


texts: Can secondary beams be supported to columns occaisionally?

texts:
If there are secondary beams running between primary beams, and columns support the primary beams, then is it allowable to have the occasional secondary beam pinned to a column? Otherwise it seems to me that it would be impossible to connect a secondary beam to a primary beam at a location where a column is. For example, in the picture below, it appears as though the third secondary beam from the left is connected directly to the column. In this case, is the primary beam completely unaffected by this beam?

I was taught that if a beam is connected to a column then it is no longer a secondary beam. Moreover, would the analysis of a single primary beam not include the concentrated loads of the secondary beams which connect only to the column? And in practice, do structural engineers often do this?


texts:
Suppose I have the state space system $a\dot{x} = -x + \frac{1}{k}h(x) + u$, and output $y = h(x)$, where $a,k > 0$. The only information I'm given about $h(x)$ is that $h\in[0,k]$. I want to show that the system is passive using the storage function $V(x) = a\int_{0}^{x}h(\sigma)\ d\sigma$. The definition of a passive system is $u^\intercal y \geq \dot{V}$ for all $(x,u)$. Thus,

$$
\dot{V} = ah(x) \dot{x} = h(x) (-x + h(x)/k + u) = \frac{1}{k}h(x)(h(x) - kx) + h(x) u.
$$

Rearranging this gives

$$
h(x)u = yu = \dot{V} + \frac{1}{k}h(x)[kx-h(x)].
$$

In order to prove passivity, I need to show that $\frac{1}{k}h(x)[kx - h(x)] \geq 0$, for all $x$. However, all I'm given is that $h\in[0,k]$ so how can this be true in general? Am I missing something really simple here?


texts:
How to create a 3D model of a person's veins using ultrasound? How to do something like this, CARTOSOUND® Module:

  This 3D ultrasound technology gives you all the benefits of traditional intracardiac echo

Why is most ultrasound 2D?
Is 3D ultrasound a separate technology from 2D?


texts: Is it possible to convert uniform loads to point loads?

texts:
I want to perform a structural analysis on a portal frame using a finite element solver to get a displacements and reactions for a load. The software library only accepts loads applied to node, not to the member. The node loads have 6 parameters: 3 translation (x,y,z) and 3 rotation (xx,yy,zz). My load is a uniform load of 1 kN/m along one rafter.

Is it possible to convert the uniform member load to point loads that I can apply at the nodes?

Portal frame dimensions:

span: 10 m
eave height: 5 m
apex height: 6.34 m
rafter length: 5.18 m
roof pitch: 15°

EDIT: fixed apex height


texts: Robustness to Additive Uncertainty Proof using small gain theorem

texts:
I am trying to use the small-gain theorem to prove the robust stability condition for additive uncertainty. I have been stuck on it for a while now.
Question: How can I use the small-gain theorem to prove the following condition. For a noice model $ \tilde G(s) = G(s) + \Delta(s) W(s) $, the condition for robust stability is $||W(s)C(s)S(s)||_{\infty} < 1$, where:

$C(s)$ is the controller transfer function
$S(s)$ is the sensitivity transfer function $S(s) = \frac{1}{1 + G(s)C(s)} $
$W(s)$ is a weighting transfer function in the uncertainty

Does anyone have a link to a complete proof using this method? I find notes on the internet that simply leave it as an exercise for the reader, but I am getting stuck along the way.
Any help is greatly appreciated.


texts: Can you detect the operation of a wireless radio (or other wavelength) receiver?

texts:
I am Comp-sci student doing a software engineering paper about designing a program, planning the software like you were actually planning a real-life software project, short of writing actual pseudo-code or code. For my project, I picked doing an app that can detect a physical man in the middle attack. Like monitoring for a tap on the line.

It got me thinking, can you monitor for someone catching wireless communication? Like the latest WEP2 hack. If someone were monitoring your wireless traffic passively to capture your secure handshake, could you detect them snooping wirelessly without them transmitting packets?

My knowledge of EE stops at MOSFETs and timing of electrical currents through logic gates and metastable currents propagating through circuits because the timing of logic gate was off. My knowledge of EE certainly falls short of radio broadcasting.  So I am not even sure if such a feat is possible, I suspect it isn't but it's out of my ken.

I suspect if you were close enough a receiver would leave behind some kind of detectable EM footprint.


texts: Safe, cheap method to dissolve nitrogen in small batches of water (10l)

texts:
I am interested in creating a nitrogen infused drink. I want to be able to make small batches of my drink (its not coffee) and testing the market before having to buy expensive equipment.

I think a way to do this is to buy a strong sealable container, fill it with my beverage and add liquid nitrogen to it. I'll then seal the top and wait some time for the liquid nitrogen to infuse throughout the drink.

I will then decant from my stronger container into smaller sealed bottles for trials.

A few questions I have are these:

Will the liquid nitrogen evaporate immediately as I add it to the drink, being lost to the atmosphere and thus not infusing the drink at all.
In order to counter part 1 can I just add a lot more liquid nitrogen than would be needed to fully dissolve in the drink in the knowledge that the container can handle the pressure.
If a beer bottle can maintain the carbonation of a drink, can it also maintain the nitrogenation of a drink?


texts: What is the good reason if the curves between two results are not similar?

texts:
According to my results, I can have this curves.
And somehow in this figure, it is not pretty much similar,
What can I say if it is asked why I still want to use the FEM results?
Or how can I validate the FEM results from this figure?

Any help?
I really appreciate it
Thank you very much in advance


texts: Right angle gearbox, proper name or design

texts:
I'm looking for right angle gearbox, but everything is horrible expensive or in parts like two bevel gears from aliexpress.
Where I can find or how to name transmission like this in the picture but in box case (if possible with mounting holes)?
I need right angle transmission 1:1, no matter what type of gear or something else. Looking for compact size, outer size of one arm, max 40mmx40mm. Maybe I don't know proper name to find it.
Also if I don't find good out of the box solution, how to proper design that type of transmission? I know I need bearings on shaft and screw, but how to avoid skipping on teeth?


texts: Why not to calibrate accelerometer in IMU filters?

texts: I have been reading various research papers regarding IMU filters and I came to the question of why do we not need to calibrate the accelerometer values as we do for the gyroscope and magnetometer?


texts: Does bulk specific gravity (Gmb) of asphalt specimen change with sample size?

texts: If a 6"x4" asphalt sample is cut down to smaller dimensions (let's say to prepare a DCT testing specimen), does the Gmb value change from the original bigger sample? If it does change during testing, then what might be the factors affecting this change?


texts: Estimating wind velocity behind a wind turbine

texts: According to the Wikipedia page on the Betz Limit, the outgoing wind velocity behind a wind turbine can be as low as 33% of the incoming wind velocity. However, this figure assumes that the turbine is operating at the theoretical Betz limit. Since most turbines operate below this limit, is there a straightforward formula for calculating a more realistic estimate of the wind velocity behind a turbine?


texts:
what is the physical interpretation of poles and zeros of a mechanical system?
I'm asking things like the meaning if I have only 0 or only complex numbers. And about the number of the poles and zeros, it should be equal? What can I infer about the stability?


texts: Why phase margin and gain margin should be positive?

texts: In many textbooks it's given that gain margin (in db) and phase margin of the system needs to be positive for the system to be stable. I could not find the reason behind this. Could someone explain this?


texts: Buckling of a cantilever with midway support

texts:
I'm trying to understand the implications for buckling and column sizing in the drawings below.

A 3000mm 120x60 RHS steel column supports a 350mm horizontal steel beam. The column base and right side of the beam are both fixed but can pivot. They are joined by a continual fillet weld "T" join, so the junction can rotate but will retain its angle. The only load is a vertical static force on the left-most 100mm of the horizontal beam.  The column can be placed at any position under the beam, as shown in the 3 drawings (nearer to the right would be better). The thickness of the beam is thick enough that it will not deflect noticeably or materially.  The thickness of steel in the RHS column is to be based on calculations.

My question is this:

The column's required cross-section clearly depends on the axial compressive force, which varies according to the column's position.  But the eccentric load is a concern and I can't be quite sure if I am right to ignore it here.

Assuming that the beam is sufficiently rigid and won't noticeably deflect, then when the column position changes to the right (as shown), does the column experience only an increased axial compressive force, or should I also consider an additional bending moment imposed on the column as well?

My reason for thinking I can ignore it and only consider the axial compressive load on the column, is that wherever the force applies on the beam, the column only experiences it as an axial load. But I'm not 100% sure since if the beam deflects even slightly (as it must), this must cause bending of the column (as they are welded) and therefore a bending moment in the column (however slight).

Is this effect significant compared to the increased axial compressive force, or is it trivial and dominated by the increase in axial compression? Do I need to allow for an additional bending moment in my buckling calculations, in this situation, to ensure the column profile is adequate?

(NOTE - I am based in Europe so any specific calculations would be Eurocode not North America code based. That said, the question isn't really about specific code calculations and it shouldn't matter)


texts: Need help with reverse engineering a sensor

texts:
I have a pressure/temperature sensor for a vehicle, which I decided to tear apart to see exactly how the sensor works.

This sensor as designed by the manufacturer it is meant to be immersed in oil to detect fluid temperature. The pressure sensor side of it seems pretty straight forward in that there is a hole in the sensor physical body and a PCB.

I am stuck on how the temperature sensor works in this specific sensor, if you look at the picture I attached the entire PCB is covered in a glue like substance I am guessing to insulate it from the oil. The temperature sensor is covered in some sort of cement like substance and is bonded only to a metal rod.

I am a little loss as to how the temperature sensor would be able to detect change in the fluid temperature if there is all the insulation glue on the board isolating the sensor from any fluid. My only guess is the metal rod acts to conduct heat towards the temperature sensor on the PCB. So to prove this I have tried measuring the temperature signal via a pin on the sensor and oscilloscope. I've immersed the sensor in oil, raised the heat of the oil and applied the proper 5 V to the sensor. For some reason the temperature signal will stay only at 1.3 V regardless of oil temperature.

I am beginning to think maybe the sensor can only read the temperature with a pressurized fluid, and not just sitting in fluid. Any input is appreciated thanks


texts: Second Moment of Area for slanted triangle?

texts:
Consider this triangle with its centroid at $C$:

Then this is how I believe we can calculate the Second Moment of Area along the $x_{C}$ and $y_{C}$ axis:

$$\begin{align}
I_{xc} &= \frac{bh^3}{36} \\
I_{yc} &= \frac{hb(b^2-st)}{36}
\end{align}$$

So far so good.

But then we have this triangle:

Questions

Is there any similar way of calculating the second moment of area for a slanted triangle, like the one above?
Will even the same equations work?
How is $s$ and $t$ derived in that case? Can they be negative?

Please assume we can NOT rebase the triangle — we must use $LR$ as the base.

Source for equations


texts: Programming a gas mass flow controller rig

texts:
I'm trying to upgrade a multiple gas flow controller, which must be capable of controlling the mass flowrates of three gases independently through one outlet line to our system, and am in need of a bit of advice on programming it. I'm using an arduino and a few DACs to tell the proportioning solenoid valves how open they should be. The current setup schematic is below, though I have more pressure sensors and mass flow sensors at my disposal if necessary.

My colleagues' advice is to use PID loops for each of the gases. This would be easy, particularly as there's an arduino code already available - however I'm not convinced that's either necessary or the best option, because:

There is hardly any inertia in the system, unlike the thermal inertia in an oven for example. If it were just one gas, with one inlet pressure and one outlet, just the P part of a PID would be enough I think.
The flow rate of each gas is dependent on the pressure differential before and after the valve, which is then dependent on the mass flow of the other gases and the outlet pressure, hence a PID could reach the optimal flow for one gas but in doing so change the flow rates of the other gases - leaving oscillation in the system.  (the pressure in the system at the outlet may be changing slightly also)
I don't know if its possible, or if so then how, to write a PID loop for simultaneous multiple input/outputs.

Hence I would appreciate any ideas, or solutions that exist which I was unaware of, for how my program should go to control the proportioning solenoid valves?

P.S. I'm not asking anyone to actually write a code for me, but just a basic idea of how I should do it would be great please?

P.P.S. (There is a formula for gas flow rate here, so I suppose you could try to work out theoretically what the optimal signal to the valves would be based on some kind of simultaneous solution of this formula for the three gases, taking into account friction factors for all the little fittings and parts in the system and expansion factors for the particular gas mixtures concerned (I don't think any of the gas cylinders are absolutely pure mixtures) etc. but I would think it's possible not to go that complex here!)


texts:
I have no formal training or professional experience as a mechanical engineer. I would like to design a rotating base that is powered by a motor. I would like to accomplish the following:

Smooth, quiet operation
Self-locking (as could be accomplished with a worm drive)
Minimal wobbling of the rotating part of the base
Minimal loss of power (forgive me if "power" is the wrong word here) due to friction.
The rotating part of the base doesn't fall off if the device is held up-side-down.

I'm thinking of using a worm drive (with a helical worm wheel) and thrust bearings. But I'm confused about how the thrust bearings would be attached such that the thing would be able to handle the axial loads from the worm drive, as well as avoid simply falling apart. Believe it or not, I've been researching this question for weeks and I'm still confused. Maybe I'm not mechanically inclined. Can anyone point me in the right direction?


texts: How to digitalize a UV image (create an array of the light output at the pixel level)?

texts:
I would like to display an image onto a screen using a digital light projector and somehow record the amount of light the screen is receiving from each pixel.

I have thought about using a visible light filter over an array of very small photovolatic cells and recording the voltage output by each cell, but the logistics of the wiring would be immense, not to mention I can't seem to find cells small enough.

I have searched for 'UV screens' and many other terms but I can't seem to find anything. There are many results for UV diodes but they are too large to get the resolution I need.

Does anyone know if such screens exist?

Let me explain a common problem where this is an issue:

This frequently occurs with 3D printers that use ultraviolet-cured resin:

The theory is: projector displays black&white (binary, not grayscale; uniform regions of 100% brightness and 0% brightness) image onto the bottom of a transparent container of the resin, curing one "layer" of the item, then the layer is lifted (using a mechanical actuator), the space fills with more uncured resin, and next layer is displayed and cured.

In reality the projector's light is non-uniform - some areas brighter, other dimmer. This depends on a lot of hard to determine factors, like light source construction, lens alignment errors etc. As effect, rhe resin will cure to a different degree in different areas of the image.

Independently, the projector is capable of displaying full grayscale (or even color) images (for no other reason that that's what's cheapest due to demand and economy of scale).

Therefore, if you know the brightness layout of the projected image, you can compensate in software - adjust the projected image of item layer, by dimming areas that were brightest; display a grayscale image instead of 1bpp, that results in actual uniform exposure of the "screen" surface, and uniform curing of the resin.

But in order to generate these adjustments, you must obtain the individual map of brightness of the projected image, as generated with this specific projector. With visible light, that wouldn't be very hard, just take a photo of the screen displaying a white sheet using a normal camera. This being ultraviolet though makes it quite tricky.


texts: Why noise canceling headphones do not attenuate the signal itself?

texts: Noise canceling headphones use a microphone to capture noise in order to cancel the same. The microphone will capture whatever acoustic signal reaches it. Since it is in the vicinity of the speaker, it must capture the sound coming from the speaker apart from the noise, particularly low frequency components. This should result in not only removal of noise but also of some portions of the signal. How it is ensured that only noise is removed?


texts: Is the same amount of force required to rotate these reels?

texts: Assume the motor on the vertical reel is fixed, and the entire base of the reel rotates on the bottom plate. If both of these hose reels weigh the same amount, will the vertical reel require the same amount of force to rotate as the horizontal reel? Or could the vertical reel be rotated using a less powerful motor?


texts: What is 'wavelength' with reference to turbuence?

texts:
When reading about turbulent flows and turbulence spectrum I frequently come across the terms 'wavelength' 'wavenumber'. I understand that the energy is transferred from larger eddies to smaller ones and so there is a spectrum of different sized eddies spinning at different velocities. But what does the wavelength and frequency of turbulence mean?
Is wavelength the diameter of the various sized eddies? Does the frequency of turbulence mean the angular velocity of vortices or the frequency of variation of different state variables?
I have a feeling that the wavelength is related to some characteristic length of the eddies but why term this 'length' the 'wavelength'? How is it related to waves?


texts: Is the tolerance of pitch of a thread standarized?

texts:
As I was browsing ISO 965-1 it defines tolerances on a plenty of variables regarding metric threads, but it gives the pitch of the thread as a simple number from an allowed set ( 3 – 2 – 1,5 – 1– 0,75 – 0,5 – 0,35 – 0,25 – 0,2 ), and no tolerances on these are ever given.

Why is it so? Are they defined in some other standard or is there a specific reason why they aren't defined to a given tolerance? Specifically, when I'm using a threaded rod as a lead-screw actuator, I'd like to know what inaccuracy can I expect coming from imprecision of pitch - how accurately do 1000 turns of a M10x1 threaded rod convert to 1000mm travel distance of the nut (minus backslash etc)?


texts: How much weight can this aquarium stand hold?

texts:
I purchased this aquarium and stand secondhand, and a few people I’ve spoken to have been suspicious of the stand’s ability to hold the aquarium when filled with water.

The tank holds roughly 55 gallons. The legs are 1/2” diameter cold rolled steel. The lower frame is about 8” from the ground. The upper frame is 30” from the ground. Both frames are welded to the legs. The upper and lower frame are angled steel, approximately 1” x 1” x 1/8”.

I am confident that this stand can hold the 600lb filled tank. Can this stand reliably hold 800-1000 lbs?


texts: Shear between which two fluids is better for atomisation - liquid & liquid or gas & liquid?

texts:
In designing an atomizer which generates a spray of liquid, one can adopt atomisation through shear.

Shear in the following cases are to be considered:

stagnant Gas- moving Liquid: in this gas case the gas is stagnant but the liquid is injected at high velocity. This encountered in daily diesel IC engines.
moving gas - moving liquid: this is used in aircraft engines wherein the fast-moving gas atomises the liquid due to shear
moving liquid - moving liquid: this is a not-so-often encountered area but shear does occur when two liquid layers move one over the other.

Comparing the atomization/shear intensity, which of the following will be the highest?


texts: What chemical can be used to restore synthetic rubber?

texts:
When rubber (I don't know the specifics, but I assume it's butyl rubber) gets old, it turns into one of two states usually:

It becomes sticky and gummy.
It becomes hard and brittle.

I'd like to know if there's a way to change hardened or sticky rubber back into its original condition. The only thing I tried so far, is heating it up gently with a hot air gun to ~60°C which makes hard rubber more malleable.

I understand there are different kinds of synthetic rubbers, made of different polymers, and henceforth, there might be a range of chemicals that might be used to treat those various kinds. I couldn't find any information on such "pairings", for instance I was searching specifically to treat butyl rubber, but I couldn't find anything.

The air ducting in cars is made of some sort of hard rubber (I'm not sure what kind of polymer), and I've heard that Ballistol can be used to soften it, but it's hearsay, essentially, I'm not sure about that.

I'm not looking for a way to completely "rejuvenate" rubber parts like that, just to have them restored a bit, so they are easier to work with.

Same thing with sticky rubber. Is there a way to make it less sticky?


texts: How can I calculate the smallest voltage a given adc can read?

texts:
I have a project where I'd need to measure small voltage (0.05 mV) output of a wheatstone bridge with an arduino mini pro.

Based on my previous question most probably it can't be done with its analogue input directly.
what is the range of the measurable relative elasticity with a commonly used strain gauge

The question is that can a hx711 module measure so small voltages?
Based on the calculation in the question it has the resolution of 3 uV from 0 to 5V excitation voltage.

How can estimate that what resolution I can expect in practice?


texts: Is having a keyway in aluminium for 30Nm a bad idea?

texts:
I'm designing an aluminium shaft hub for a 16mm keyed shaft with a maximum torque of 30Nm. However, stress analysis tells me that the keyway can suffer too much stress:

If my understanding is correct, keyways have little or no fillet, then how is stress relieved? In general, is driving an aluminium hub with a keyed shaft for ~30Nm a bad idea? There are some aluminium hubs with keyway on the market, but it's not clear if they're designed for 30Nm. Could I be missing something in my design?

UPDATE: I've added 0.5 fillets in the keyway, but the stresses are still very high:


texts: Alternative to HDPE Piping for long range sea-water + water transport

texts: Is there an alternative for the expensive HDPE Piping for long range sea water transport?


texts: Analysis Of Statically Indeterminate Structures By Hand

texts:
When double-checking/confirming results produced by structural analysis software, many engineers recommend verifying and spot-checking key or critical members if the entire structure is not analysed.

However, for rigid jointed structures with sway, it is not possible (at least in my understanding) to analyse individual members. This means that hand calculation methods such as moment distribution or slope deflection cannot be applied directly.

How would I go about analysing those members in a sway frame?

Also, to what storey of an indeterminate structure would you analyse purely by hand calculations without computer software when considering code requirements?


texts: How fast movement (cycles/s) can I reliably read with PSoC4 quadrature decoder?

texts:
PSOC4 provides a quadrature decoder functionality but I was unable to find specifics on its performance in the datasheets. Sure I know I need to read and utilize the count until the 16 bits of its counter overflow, but that's some 32k per iteration of the main loop of my program. If a precise encoder is attached to a fast motor, that produces lots and lots of pulses in a very short time, and I'm worried the decoder module won't be able to keep up.

So, does anyone know what is the maximum performance of the decoder block - the minimum timings of its input?


texts: Why don't propeller designers use multiple profiles?

texts:
I'm designing a ducted fan, and I'm deciding on the airfoil profile. NACA 16-series profiles are well-suited to M > .5 or .6, but they're not particularly efficient at lower Mach numbers. On the other hand, older profiles, like Clark YM, work quite well at lower speeds.

My question is, why do propeller designers generally only use one profile (with scaled chord and thickness) throughout the propeller? Is there some reason not to use, for example, a Clark YM for 2/3 of the blade and a NACA 16-709 for the outer 1/3?

Note: this being a ducted fan, laminar profiles will not work, so they aren't under consideration.


texts: Can we calculate the torque acting on the last gear determine teeth of the gears of the gear train in the below addressed manner?

texts:
The specifications of the generator is as follows:
Efficiency- 70%
Rated Torque- 0.56Nm
Rated current- 14.3A
Voltage- 24V
Rotor shaft dimension- 1cm(diameter)

The gear train is designed such that a spool/winch will be attached tot he last gear of the gear train.
A weight block will be suspended through that spool/winch and the gear box must be designed in such a
manner that it will provide a rotation of 2900 rpm but the rate of drop of the weight must be 1meter/min.
Diameter of shaft= 1cm
Circumference of shaft= Πd
                         = (22/7) *1 cm
Circumference is equal to one revolution
Generator RPM= 2900
Total length covered by generator shaft per minute
                              = 2900*22/7
                              = 63800/7 cm

Total length required at output of motor 1meter/min
                =100 cm

Required gear ratio= (63800/7)/100
                   =638/7

Output torque is= gear ratio* input torque* efficiency    // This is the torque acting on the gear
                                                                     attached with the spool/winch
             = (638/7)* 0.56* 0.7
             =35.728 Nm

The gear teeth to achieve the drop rate of 1meter/min is:
1st layer= 7 and 25
2nd layer= 5 and 29
3rd layer= 5 and 22

I am a CS graduate so this is not my field of expertise. It happened so that during this quarantine i am trying to indulge myself into some DIY mechanical projects. Please guide me in case i am wrong somewhere.


texts: How to measure / calculate Tait-Bryan angles of a moving platform in SimMechanics

texts:
I exported a model of the mechanism created in SolidWorks to SimMechanics in order to explore the possibilities of control. To solve the problem, i need to know the angular position of the mobile platform. In reality, I can do this with the help of a sensor.

How to calculate these angles in SimMechanics?


texts:
I have spent two days searching the web but haven't found out how to define the following parameters for weep holes in retaining walls.

horizontal and vertical (if staggered situation) spacing between each weep hole;
slope degree;
diameter;
the space between bottom of the ground and the weep hole also form the top as well.


texts: Is VLF-EM scanning for fractures a valid way to find groundwater for a well?

texts:
I need to choose where to drill an agricultural well. I am trying to get as much water as possible (at least 100 gpm).
I am considering hiring a guy who claims to be able to find water using a device called an ABEM WADI. My understanding is that this devices uses VLF signals from far away transmitters to identify fractures in the ground. He says he walks in a straight line in a candidate area for well drilling, and looks for fractures noted on the screen of the WADI. He claims that areas with a certain type of fracture (I think he said 45° fractures were the best) are more likely to yield a lot of water.
To what extent is this method scientifically valid? It sounds legit, but methods of "dousing" or "witching" for water are often little more than divination, so I'm skeptical. I googled around and found some scientific papers about VLF-EM scanning, but I lack the science/engineering chops to interpret them.


texts: Beam Reaction Problem With Hinged Joints

texts:
The problem was assigned in my Structural Analysis class, and I am having some difficulty with it.

My professor said the problem is "very easy" if we just think about what the fixed end moment on a cantilever is. However, I don't see how this is relevant considering the member ACE is not a cantilever...

The only other way I see to do this is using the moment distribution method, but I'm uncertain as to what happens with the internal hinges; we've never had a problem like this in class, and there is no relevant example in my textbook. Any suggestions?


texts: What is the relationship between drive shaft diameter and torque output?

texts:
I have a DC motor with a shaft with a diameter of x. It would produce some torque T because torque is proportional to radius. If I stuck a pulley on the shaft of radius 2x, then I would produce twice as much torque, right? And then if I attach this to a gear with a ratio of 2:1, I would again double the torque.

Here is an image to clarify:

This bugs me because it means the larger a pulley I can fit on a shaft the more torque I get. What am I missing? Are the RPMs reduced?


texts: Which case is used to check Drift and P-delta for a building subject to seismic forces?

texts:
Which case is used to check the drift and P-delta for a building according to ASCE ?

Static lateral force procedure (with a period Comparing T the real fundamental period with CuTa)
Static lateral force procedure (without comparing T with CuTa)
Modal response spectrum analysis (without scaling)
Modal response spectrum analysis (with scaling)


texts: Advice for designing internal structure of glider wing

texts:
I am interested in designing a scale model semi-monocoque wing for a glider. I've done some research on the framework and internal structure. I have found out about the spars, ribs and stringers and I am trying to produce a design with the highest strength to weight ratio. I am planning on making the wing 0.5m long with a chord length of 0.1m along the cross section (so no tapering).

Here is my design so far:

If anything is unclear please let me know. In my first diagram, I have placed 2 spars through the wing about 10% of the chord length from the leading edge and 15% from the trailing edge, leaving 75% of the chord length between the two spars.

In the second diagram is a rough plan of how many ribs would be used and where they would be placed: the solid outline is the wing outline, the thick black lines are the spars and the dashed lines are the ribs.

I have used a triangular configuration, as the triangle is the strongest shape and resists shear, torsion, compression and tension better than any other shape. Then I have placed a rib going down from the top corner of each of the 3 triangles to the bottom of each. Then I have placed ribs (or stringers) between each of the bottom corners of the triangles.

My question is, how can I improve or optimise that design? Is there a certain number of triangles I should use and how big should they be relative to the wing? Should they be equilateral triangles or is isosceles stronger? Also, how many ribs should I be considering using?

I'm not looking for anyone to figure out exact quantities. If there is some kind of calculation I need to carry out to find the optimal number or triangles and ribs, I would be happy to do that. Unless it is way beyond A-level maths/physics standard then I probably will not be able to do it. But I would like advice on how I can figure it out. If my question is vague or unclear, please inform me, and I will gladly edit it.

Thank you


texts:
Ion thruster has very low thrust due to its low mass flow rate. However is it possible to increase the mass flow rate? Together with its high exhaust velocity, won't the ion thruster be able to reach that of chemical rocket's thrust considering how the exhaust velocity of chemical rocket is much lower?

Or is it not possible to increase the mass flow rate due to the limited amount of electricity that the rocket can carry? I know there are other things to consider like the screen which will affect its efficiency(prevent all the ions from leaving) but I don't know how much it will affect the maximum mass that can flow.


texts: What are the advantages of wastewater treatment technology that can work in both anoxic and oxic condition?

texts: I was looking at some papers related to moving bed Biofilm reactor and it says that it can be used both in anoxic and oxic condition. So, I want to know what are the advantages of treatment plants that can work in both anoxic and oxic conditions?


texts:
Given:

A problem in my thermodynamics text is stated as follows...

Determine the mass and the weight of the air contained in a room whose dimensions are $V=$ $15ft$ x $20ft$ x $20ft$. Assume the density of the air is $\rho=0.0724\cdot\frac{lbm}{ft^3}$.

My Solution:

First find the mass...

$$m=\rho\times V$$

$$m=0.0724\cdot\frac{lbm}{ft^3}\times 6000\cdot ft^3$$

$$=434.3\cdot lbm$$

Now find the force acting on the air due to gravity. This is the weight of the air assumed at sea-level...

$$W=m\times g$$

$$W=434.3\cdot lbm\times32.174\cdot\frac{ft}{s^2}$$

$$=13976\cdot lbf$$

Question:

I find it hard to believe that in an average size room the air weighs a whopping $14,000\cdot lbf$. Did I do something wrong in my calculations or is this correct? If this is correct perhaps we earthlings living on the surface of the earth are the real extremophiles.


texts: Can you please suggest what kind (type) of hinge / pins I should use to make the mechanism in the attached file. I was considering to use the pins shown in the second image. But I am not sure if it will work.


texts:
I'm trying to find an answer to a question in one of my thermodynamics textbooks. (Undergraduate chemical engineering is the context).

It is a conceptual question, asking, "Do all systems in equilibrium continue to be in equilibrium if they are instantly isolated from their surroundings?" What does everyone think?

I've consulted a few authoritative sources, and the answer becomes confusing and conceptual and even philosophical. I figured there might be a very straightforward answer.

Thank you.


texts: Elastic Modulus in Arbitrary Direction for Orthotropic Material

texts:
Suppose I have a material with an elastic modulus of Ex in the x direction and an Elastic modulus of Ey in the y direction.

How would I find the effective elastic modulus in an arbitrary direction (say for an angle theta from the x axis)?


texts: Fluid Mechanic Buoyancy problem. How to determine the height?

texts: I tried to solve it but I don't know how to bring the Area A in this equation. I used the area of the small vessel, but this one shouldn't be in the equation. Thanks a lot


texts: Any idea on how this type of pneumatic solenoid works? I know that NC is normally closed, NO normally open, but not sure how air flows? Thanks!


texts: Finding the diameter of a Triple Thread Worm Gear

texts:
For a Board Exam Review:

  A triple thread worm has a diameter of 3 inches. The wheel has 25
  teeth and a pitch diameter of 5 inches. Material for both the worm and
  the wheel is of phosphor Bronze. Compute the Helix Angle

Answer is 0.2

Helix Angle can be obtained by trigonometry:

$${ \tan(H) = \frac{\pi \times D_{worm}}{L} }$$
$${ L = N_t * P_a }$$

Where L is the lead, N is the number of threads and P is the Axial Pitch.

$${ L = 3threads * 3in }$$

Well thats where I stopped. I don't know how to find the diameter of the worm gear without it being explicitly given to me. I tried other formulas but they were more of the diameter of the wheel instead of the gear. Is there a formula for solving the diameter of the gear?


texts: Per the ME Pavement Design Guide MOP, Section 5.3.6, Eq 5-18b, how is p02 assumed if not entered in Pavement ME?

texts:
The MOP, equation 5-18b calls for p02, which the MOP describes as the "Percent passing the 0.02 mm sieve".  I assume that this is the percent passing for the subgrade.  We only input down to the p200 for our subgrades.  For example, our clay entry is the following:

3/8” = 99.9
No. 4 = 99.5
No. 10 = 97.7
No. 20 = 96.0
No. 40 = 90.7
No. 100 = 68.3
No. 200 = 57.5

Therefore, how is Pavement ME calculating the p02 input for us of the site factor (SF)?
Note that if 0 is assumed, then the equation would have an error because LN(0) is undefined (ie. no value), so I assume that some value must be assumed.


texts: Where does the equation for shear stress of a rectangular beam (3/2 V/A) come from?

texts:
I am writing a report and need to reference every equation used. I am using the equation for shear stress in a rectangular beam of
tau = 3/2 * V/A
but am not sure where it came from or what textbook to reference it from! It just seems like common engineering knowledge so I don't know who to put down as the originator of the equation.
Thanks


texts: How to obtain relative movement and rotation of bridge bearings?

texts: In structural analysis of a bridge using whatever software, such as MIDAS or SAP 2000, it is easy to obtain the deformation of individual nodes. However, for bearings, what we want is the relative displacement of top and bottom nodes. As we have thousands of load cases, we envelope them into load combinations to get the maximum and minimum forces and deformations. How does one derive the bearing movements with ease?


texts: Order of matrices when rotating a vector

texts:
I would like to calculate the vertical velocity of a drone by integrating accelerometer data, problem is that the accelerometer measures in the frame of reference of the drone and not the the earth.

I know how much the frame of reference is rotated along the x and y axes and I know the position of the vector in this frame of reference.

I would like to rotate the vector back to get actual vertical acceleration but the order of operations matter for matrix rotations.
The drone rotated on both axes simultaneously so I don't know which rotation to calculate first.

I don't necessarily believe that this is the right place for this question but other communities suggested I try here.


texts: Using a thermos flask as a vacuum chamber

texts:
I want to create a vacuum chamber (-900 mbar) that can withstand heat (120°C).
I thought about using a pressure cooker similar to most DIY vacuum chambers, but then thought about using a large food thermos flask (since you get insulation for "free").
Is there any risk/downside I might be overlooking?


texts: How can I decrease strip tension with bridle rolls in tension leveller? How can I find total elongation after the strip exits initial bridle rolls?

texts:
I'm working on a tension leveller design which consists of 3 main sections. These are

Input Bridle Rolls Zone: Increase the strip tension coming out of the decoiler.
Leveller Zone: Strip goes through reversed bendings and gets plastically deformed under tension.
Output Bridle Rolls Zone: Decrease the strip tension to recoil.

Both 1. and 3. sections use s-rolls. I found out that in the 1. zone the mechanics of "Capstan Equation" is utilized.
I understand how the strip tension is increased but I couldn't understand how it can be decreased. I would really appreciate any insight.
With elongation,
I've used the approach where I tried to find tensions in each sections, from that I've found stresses. By using stresses I've found strains from stress strain diagram and from strains and initial length, I've found final lengths hence elongation. I've imagined a 1 metre piece and find total elongation of that piece at the exit of input bridle. From that by scaling the ratio to whole strip length I've tried to find how much as a whole the strip elongates. Is that a wrong approach?


texts: Identifying O-rings with a low friction ratio

texts:
I want to make a precision syringe pump and need some O-rings for its piston. The cylinder is made of stainless steel (maybe later I'll order a glass one). The lower the friction ratio, the better the precision of the pump.

What sort of rubber is the best in this case? BuNa? Viton? Silicone? Something else?

Also, what should be used to keep it lubricated?


texts: My robot is not able to maintain balance while turning

texts:
I am making a robot for my college project. For now, the robot simply has to move forward, reverse, right and left. While the forward and reverse thing is very smooth but while taking a turn it wobbles continuously. I tried to add weight and slow down the speed but the vibration is still there. I need to know what I am doing wrong. Attaching the youtube links of the wobbling robot.

Wobbling robot during turning
Smooth movement in the forward direction


texts:
I came upon enough 3"x3" structural aluminum square tubing to build a countertop over the washer, dryer, and sink. I wanted to double check the sag/deflection of the tubing but am having trouble figuring it out. I think it should be strong enough but just wanted to double check. Where is a simple calculator that I can plug in the components and see if the aluminum will bend. The front piece is 3x3x7.5'- 1/4" thick. There will be 3x3x24" pieces going to the back wall to support as well. Really I'm concerned about the main span. I don't imagine it would get over 300 lbs across the whole weight.
Thanks


texts: Breath Sensor: A low range pressure sensor that won't be affected by humidity

texts: I am designing a device that will measure the force of a breath through a tube. A small differential pressure sensor like this https://www.digikey.ca/product-detail/en/MPX10DP/MPX10DP-ND/464046 would be ideal but I believe that the humidity from the breath would impact the pressure reading. What kind of small, cheap pressure sensor could I use that would perform in a humid environment?


texts: Is it true that if the structure damaged or corroded, the stress will be lower?

texts:
I  am comparing the stress results between original or non-corroded model to corroded model.
I found that the stress value in non corroded model is lot more bigger than the corroded model,
is it correct?


texts: How to get soft touch matte finish on my resin cast parts?

texts: I'm working on a prototype electronic consumer product for which I intend to use silicone molds with polyurethane casting to get the plastic body. I have seen a few products with a smooth satin finish which almost feels like rubber to touch but is actually plastic. Requesting advice on achieving similar surface finish.


texts: The Heat Added in a Reversible Polytropic Process

texts:
The question: Consider $1\ kg$ of air at $32\ C$ that is expanded by a reversible polytropic process with $n=1.25$ until the pressure is halved. Determine the heat transfer.
Specific heat constant volume for air is $0.1786\  kJ/kg.K$

The correct answer is: $17.02\  kJ$ heat added

My work so far:

$$\frac{T_{1}}{T_{2}} = \frac{P_{1}}{P_{2}}^{\frac{n-1}{n}}$$
    $$n = 1.25$$
    $$\frac{P_{1}}{P_{2}} = 0.5$$
    $$T_{1} = 32+273$$

You'd get $T_2 = 350.352$

$$ Q = m*Cv*(T_2-T_1)$$

I get $8.00\ kJ$ something.

What am I doing wrong?


texts: What is meant by "perfect geometry" in the context of Euler buckling?

texts: In this question for example (in the first answer) it is said that the Euler critical load formula is unrealistic, because it assumes perfect geometry and perfect alignment of the load. I've found similar statements from other sources as well. What is meant by these? I've seen some derivation of the Euler buckling formula, but there is no mention of the assumption of "perfect geometry" or that the load needs to be "perfect aligned". The Euler buckling formula seems to follow quite directly from Euler beam theory. So could somebody clarify a bit what do these assumptions mean? Thank you!


texts:
I have a large DC Motor I ripped out of a treadmill and I'm curious if the back emf generated from manually rotating the motor is a DC output or an AC output. Is it AC only when it's from the power grid and other sources treated as DC? How can I always tell?
For context, the motor is a 2.65Hp, 21.4A, P.M.D.C Motor
Thank you!


texts: Stability implies frequency response existance

texts: I was just wondering why when a system is stable there is a frequency response $\left(H(p) \rightarrow H(j\omega)\right)$ and when the system is unstable the frequency response doesn't exist?


texts:
I need to remove 5" x 48" of the middle of a 6"x12"x16' header so I can clear the AC units on the top of my motorhome entering the carport. The header supports a 6/12 pitch roof with trusses.  What method of reinforcing should be accomplished.

Thank you


texts: What are the tradeoffs between using hydraulic motors and electric motors?

texts:
My limited understanding of hydraulic systems is that they aren't nearly as efficient as electrical systems, and that wire is cheaper than high pressure lines.

Example:

In a zero turn mower, each of the drive wheels has a separate pump and hydraulic motor geared down with a planetary to the actual wheel shaft.

It occurs to me that doing this with the engine running a generator and putting electric motors to drive the wheels would be a simpler design.

(I am faced with replacing an Eaton Gemini drive unit to the tune of $1500 for the unit, plus labour.  Seems to me that there should be a simpler way to make systems like these?)


texts: Thickness of a 3d print general purpose plastic/PLA 230 V ~ isolator?

texts:
I'd like to design a minimal thin light switch which holds an illuminant with standardized socket, e.g. E14, E27, and has itself such a socket to be screwed in a support and a switch which will be very small and distant from the thread and socket. Apart from the switch the object should be 3d printable with PLA for the thread and socket and the conductive parts will be printed as well or mounted after the print.

Now there's the question about the thickness of the PLA support at the buttom where the ground and phase are isolated against each other. I found no information which material is used in average sockets and which criteria it has to fulfill.


texts:
From my experience, I've been calculating RSS tolerances by squaring all relevant tolerances, summing them up and then square rooting the sums... ie: RSS=[Σ(tol^2)]^0.5

I've also heard of other methods to calculate RSS including dividing by 3, ie: RSS=3*[Σ(tol/3^2)]^0.5

What is the main difference between these two methods?


texts: Why are hyperboloid towers not popular anymore?

texts:
Hyperboloid towers were very popular in the end of 19th and the first half of 20th centuries - water towers, powerline anchor towers, sometimes tall radio towers were built using this design. The claimed advantage is using less steel compared to other designs for the same strength.

They are very rarely used nowadays (to such extent that old hyperboloid towers are treated as cultural heritage objects and protected by the state in some countries).

Why did they lose popularity? Is there any inherent defect it the design? Is steel not expensive anymore?


texts: Use magnetic levitation to lift a carousel capable of turning 9000lbs

texts:
Allow me to describe my current situation. I have a 18 ft (5.486 m) carousel that is assembled using steel beams that are bent into two circles, an outer and an inner. And there are steel spokes running in between these two circles creating the 18 ft (5.486 m) carousel. The carousel has wheels in it currently that roll along a flat steel base plate that is secured to the ground. I'm able to turn around 9000 lb (4082 kg) with this configuration. I'm trying to see if it were plausible to do the same thing, but using reverse magnetism rather than standards wheels. Essentially the variables I am locked into are, a 18ft diameter area, and a 9000 lb (4082 kg) weight capacity. The configuration of the top portion of the carousel, and the configuration of the base can be changed to some degree.
From what I've come to understand, the surface area of the conductor is related to the strength field. I can change the shape of my current carousel, i.e. make it flatter and even or thicker, or anything along those lines, the same with the base. But I have to use steel, and I have to be able to support the 9000 lb (4082 kg) load.
This has proven to be hard to research without getting a physics degree, so I'm hoping to find some help here. I'd like to better understand the math behind all this so I can at least determine if this is a viable endeavor. Given the situation described above I'd like to get a formula I could use and manipulate the variables too as to test different setups and configurations. What variables are the most important to consider for this? Is it the shape of the conductor (carousel, base plates) or more so to the current? And how could I determine the degree a change to the conductor will have on the current needed?
Thanks in advanced, any help or direction would be much appreciated!!


texts:
I want to design and create a gearbox that allows an input shaft to be continuously rotating in one direction, while the output shaft rotates one full turn in the same direction but then half a turn in the opposite direction and repeat that cycle.
The application for it would be attaching to a drill and automatically tap holes to cut threads.
The only way I can see it working at the moment is by creating a gear which has teeth missing so that it rotates to a certain point  (1 full turn of output) and then slips, being pulled back by a return spring) and hits a stop to restrict back rotation to half a turn.
However I have concerns about the reliability of this design and the fact that it would be difficult to allow it to work in both directions.
Having a mechanism that can operate in both directions by changing the rotational direction of the input shaft is ideal because it would allow it to be used to cut both right and left hand threads.
Any ideas about how to achieve such a gearbox would be greatly appreciated.
And sorry if this sounds really confusing, it’s quite difficult for me to explain.


texts: How to determine if an engineering process is stable and capable?

texts:
Mostly interested in understanding how engineers determine if an engineering process is stable and capable, particular in design for manufacturing (DFM) frame work for components. Some example components to consider are:

Flow rate for Solenoid Valve
Torque for a Brushless DC Motor
Capacitance for a Capacitor

Note: There are infinite amount of examples.

How does an engineer confirm if a vendor has a stable and capable process (incoming material)? To be cost competitive it is important to have the least amount (optimal) manufacturing test and inspection processors yet ensure the end product meets specification.  How does an engineer ensure the final product meet specification (outgoing material)?