texts: Would a centrifugal flyweight governor system slow down the descent of an object that is free falling down to the Earth's surface? (Revised design)

texts:
I am wondering if rotating flyweights would slow down the descent of a object that is free falling down to the Earth's surface.
Please reference the conceptual drawing below:

This drawing is showing a cross-sectional view of a sealed hollow cylinder. Inside this hollow cylinder would be two DC electric motors with each having two rods attached to their rotor shaft and would have two thrust bearings sandwiching each rod which would allow each rod to freely pivot up or down as the motor shaft rotates. At the end of each rod will be a flyweight.
There would be a battery attached to the bottom of the cylinder to power the DC motors and to also act as a dead-weight so the cylinder remains in this upward position as it free falls down to Earth's surface. The drawing is also showing a metal plate with a hole in it located at the top of the cylinder to enable this to be dropped from a balloon or helicopter. The DC motors would be counter-rotating to each other in order to keep the cylinder from spinning around.
A balloon or helicopter would take this cylinder up to a certain height and then release it. Just before releasing it, the two DC motors will be turned on and the flyweights will be rotating at a 90 degree angle to the motors' rotor shafts.
Once the cylinder is released and starts to accelerate downward, the rotating flyweights should pivot upwards to a certain degree (as shown in the drawing) and should act as a drag on each of the motors' rotor shafts and thus a drag on the falling cylinder, thus slowing down its descent. I believe the faster the flyweights rotate, the more drag they will produce and the slower the cylinder will descend.
Would rotating flyweights slow down the descent of an object that is free falling down to the Earth's surface?
EDIT
I have created a revised design that I believe should slow down the descent of the falling object.

The revised drawing above is showing that a round disc with an O-Ring around it which been inserted into the cylinder. This disc has two metal posts attached to the bottom of it. Each post has a thrust bearing and a shaft bearing on top of it. Attached to the shaft bearings are steel cables that are attached to the rods that are attached to the motors' rotor shafts. The inner lining of the cylinder would have some kind of lubricant on it to allow the disc to slide up or down.
The concept is that the air pressure inside the cylinder, below the O-Ring, could be set at ground level pressure (14.7 psia) while the air pressure above the O-Ring will be lower due to the lower ambient air pressure outside of the cylinder. There will be holes in the top of the cylinder to allow air to enter in or exit out of the top section of the cylinder.
In order to create a decelerating force, the DC motors would need to be turned on and off in a continuous loop. When the motors are turned off, the disc will move towards the top of the cylinder and when the motors are turned on, the disc will be pulled back down. A temporary decelerating force should be created during the time periods when the disc is being pulled down.


texts: Calculating proper specs of DC motor for rig driven on the rope

texts:
I'm trying to build a cablecam, a picture that serves only for illustration is:

The DC motor is

48V
5000W
6000rpm
6000 oz-in stall torque
85% effiencity
0.066 Ohms Resistance
135Kv (RPM / Volt)
Reduction ratio with timing belt is 1:2, so speed on 60mm output pulley is 3000rpm.

Battery is Li-Ion

48V
15Ah
70A constant/120A peak for 20sec.

Mechanical properties

Max load 40 kg (including motor, wires, frame, electronics, pulleys...)
Friction coefficient is 0.7

I want to know if this 48V DC motor can even start this mass on the rope without burn itself. I would like to know if it could reach speed of 50km/h within 10 seconds or 50 meters of travel on rope.


texts:
How to deal with thermal expansion in a city wide heating system?

Background:

As part of the program to combat pollution in and around Beijing, my adopted city of Zhuozhou (population, over half million, about 90 minutes Southwest of central Beijing, inhabited for at least 5,000 years) is installing a hot water heating system. In the last 3 weeks, they have torn up every major street in town, and they are in the process of installing pipes.

There are two pipes because the water will be conserved; according to my father in law, the hot water will flow through one pipe, they enter nearby buildings, flow through the radiators in the building, then return back to the central heating facility.

Of course, everyone is happy as this will stop a lot of coal burning, and vastly improve the air quality. Nobody seems too bothered that every street in town has been dug up at once. While traffic is horrendous, it seems like they want centralized heat.

What I have seen thus far is that they put the pipes close to each other, then weld them together.

I think when the heat is running, the length and size of these pipes will change drastically. How do you make sure the street above the pipes won't buckle? When the pipes get longer, how to prevent them from leaking? Won't the welds break? Also, are they a special type of pipe?


texts: Should I run 2-wheeler at constant speed?

texts: I have been recommended not to run the two-wheeler (Suzuki Access) at a constant speed (I give a constant throttle in a way that I run essentially at a constant speed of about 40-45 kmph). In fact, I have been told to keep changing the acceleration (smoothly though) for lesser fuel consumption. I want to understand the technical reason behind this claim.


texts: Effect of friction (or horizontal motion) on vertical surface deformation

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I am trying to model the dynamics of some system.

In summary, the system consists of one horizontal linear actuator that drives an object along a planar surface and one vertical actuator that brings the object in contact with the planar surface.

The planar surface (plate) deforms as the vertical motion of the object comes into contact with it. After the plate deforms, the object is dragged along the surface, giving arise to frictional force that opposed the horizontal motion.

My question is, does the normal reaction force from the elastic plate depend on the frictional force?

Initially I thought that because the two forces (normal and frictional/tangential force) should not interfere with each other as they are described by unit vectors perpendicular to each other. But placing an encoder on the vertical actuator, I found that moving the object tangentially along the deformed surface (along x-axis) affects the vertical motion (displacement/velocity along y-axis).

Thanks.


texts: What does multiplicity of a multiple natural frequency mean?

texts: I'm doing some vibration tests on planetary gear sets and a lot of the information I´ve read mentions a lot about mode shapes and multiplicities of the natural frequencies. I understand how one can derive the natural frequencies from the equations of motion of the gears and even the eigenvalues, but I don't understand what the multiplicity of the natural frequencies mean. Does it refer to the harmonics of each natural frecuency? If for example there's a fault it will probably be a multiple of the 1st harmonic? Also, does the eigenvalues have to do with the modal modes?


texts: Shear strength of reinforced concrete filled PVC pipe

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BACKGROUND: I'm burying a 3 foot x 4 foot drainage box (2 foot tall) in my driveway to hold/distribute excess gutter flow (1" of rain produces ~21cuft). I've constructed the walls with brick, laid on their edge so that the water can drain out through the 10 holes in each.  I need to construct a cover that, when itself covered with ~3" of crush&run will support a potentially heavy vehicle driving over it.  To further support the cover, I'm laying 1.25" iron pipe across the top (counter sunk into the brick), at 1 foot in from each side, so that the top is supported on one foot centers (horizontally: earth, then 3" gap to brick wall, then 12" gap to pipe, then 12" gap to pipe, then 12" gap to brick wall, then 3" gap to earth).  I could pour a 4" slab over the hole, but then it would be nearly impossible to lift, should the need arise.
QUESTION:  If I fill 5' long 1.25" pvc pipe with quikrete and a rebar, and then covered the top with them (placed tightly), then covered the top with the 3" of crush&run, would that be strong enough to support a heavy truck (UPS, Dump truck, etc.)?  (This way, if I needed access, I could just dig up a few of the pipe.)


texts: Maximum torsion shear stress in cylinder

texts:
I am trying to figure out am I doing this calculation correctly.

To get the maximum shear stress for a solid cylindrical pipe I need two formulas:

Moment of inertia = pi/2*r^4

Not sure what this formula is called but its:

max = T*r/ Moment of inertia

I tried to calculate these numbers for a solid shaft that is 20mm in diameter with a torque of 1255nm.

1255*0.02/((pi/2)*0.02^4)

Pascals = 99869726.7902
MegaPascals = 99.87

The material that I have has a yield strength of 490 MPa.

Is the calculation saying that even at 20mm radius the stress will be below the 490MPa that would cause this pipe fail elastically?


texts: What is the effect of changing the angle of a helicopter flybar?

texts:
A helicopter flybar is a kind of gyroscopic stabilizer which acts in feedback to the pitch of the blades.  The effect, in words, is that as the helicopter starts to pitch or roll in a particular direction more lift is applied on that side, keeping the helicopter level. These devices are commonly found on the inexpensive RC helicopters which are on sale at all major department stores.  An example of the flybar from one of these RC helicopters is shown below.

Although it isn't obvious from the picture, there is an angle between the flybar and the rotors.  On my RC helicpoter at home the angle is roughly $35^\circ$.  I believe that this angle has the effect of introducing extra phase in the feedback loop.

My questions are:

What is the effect of changing the angle between the flybar and the rotor?
How can I mathematically describe the effect of this angle?
What would happen if the angle was changed to $90^\circ$? What about $0^\circ$?


texts: What's the flow resistance of a honeycomb sieve?

texts:
Honeycomb sieves are starting to see applications in wastewater screening. What is the flow resistance of a honeycomb screen?
I would expect something similar to the Kirschmer formula (used for bar screens):
Headloss = constant, dependent on bar shapes X function of square of velocity
(Actually, the Kirschmer formula would be corrected for angle and for loading of the screen)
where velocity means in the screen, so the free survece is taken into account. While a honeycomb can have a far larger free surface compared to a screen with holes, I would expect the first factor to be different to, as the thinner bars in the honeycomb allow for a different flow regime immediatly downstream.
What is the headloss for flow through a honeycomb screen?


texts: Can we run ANSYS Fluent/OpenFOAM simulations in AWS or any free server?

texts:
I was planning to run some FSI related simulations. But the computation capacity that I have is not sufficient. But I had heard that there is a possibility to create instances in the Amazon EC2 or the Lambda and use it for computations. But it is not very straight forward. But I wanted to know if it is even possible at all to run such high computations on the Amazon server.
If anyone knows a way to use a free server for some software like fluent or OpenFOAM then please do mention the previously asked question or share the way to use the services.


texts:
I am attempting to drive a device with a motor, but also require water input.

Is there such a device that serves as both a drive motor with a water pump through the motor's shaft?

In essence, it would have the functions of both a motor and a water pump in one.


texts: Calculating final temperature of humid air and cool stone

texts:
I'm trying to gauge the efficiency of a night-cooled stone to condense water from the humid air at seashores at noon. I'm assuming the stone is thermally insulated once it's in thermal equilibrium with the lowest possible temperature at night. Then at noon, the humid air is passed through the stone and the (assume thermally isolated) system now consists of hot, humid air and the cool stone.
I understand that at lower temperatures, air holds lesser vapor, so if hot humid air is condensed, some vapor will condense.
I'm using the specific heat capacity of vapor, air and stone to try and come up with the final temperature, so that I can see how much vapor will air condense at that temperature by subtracting the after-cooling holding capacity per meter-cubed from the initial one.
The problem here that I must use the latent heat of vaporisation for the energy lost to the stone for the water condensed, but then the vapor is at a temperature lower than 100 Celsius so should I use the specific heat capacity of vapor or latent heat or specific heat capacity of water?! I just got confused.
As $q_{vapor}+q_{air}=-q_{stone}$, I came up with this $$m_{vapor}c_{Pvapor}(T_{1}-T_{F})+m_{air}c_{Pair}(T_{1}-T_{F})=-m_{stone}c_{Pstone}(T_{1}-T_{F})$$
Something just seems wrong to me here because of the vapor temperature being below boiling point of water. I know that temperature is AVERAGE internal energy of a mass of substance and all. However it still confuses me. Someone clear it up for me.


texts:
I am searching for some Engineering terms but couldn't find any of the definition.

Direct safety
Indirect safety
Warnings

Thank you in advance


texts: Control systems to control position of antenna with motor?

texts:
I want to design a control system with microcontroller to control position or orientation of antenna with BLDC motor with high precision like 0.1 deg and I don't have idea which motor position controller IC I can use or if there is an other idea please share with me.

Thank you.


texts: weight bearing capacity of a reinforced concrete floor slab

texts: What is the weight bearing capacity per square yard of a 4" monolithic concrete floor slab poured with 3000 psi concrete in 50' x 50' squares, reinforced with 6" x 6" x 10" steel wire mesh, laid over 4" crushed limestone slag, with 4 mil poly vapor barrier?


texts: Timoshenko Beam Theory for Quasistatic Cantilever Beam: Shear Term

texts:
I'm trying to determine the effect of shearing force on the deflection of a quasistatic cantilever beam.  In his book, Theory of Elasticity, Timoshenko added the following term to the deflection:

$$\frac{Pc^2}{2IG} * (l-x)$$

but the Wikipedia article on Timoshenko beam theory added the term

$$\frac{P(l-x)}{kAG}$$
https://en.wikipedia.org/wiki/Timoshenko_beam_theory

Both of these reduce to the Euler-Bernoulli form when shear is disregarded.
What is the difference between these two forms?  Should both be included in the deflection?


texts: How much of a battery needs to be replaced for it to be a fresh battery?

texts:
If I take a battery that is "dead" and completely replace the electrolyte and maybe the terminals, would it be a "fresh" battery?

So instead of pulling up to a charging station in your electric car, plugging in, and waiting half an hour or more to be able to continue, could you pull up, suction the electrolyte out, pump some fresh stuff in, and be back up to a fully charged state?

Would the electrolyte have to be charged before pumping it in?


texts:
I'm doing a project for which I need to calculate heat dissipation from a water tank. I'm not well versed in thermodynamics and I can't find any place where this has been answered.
I don't know the exact dimensions of the tank I'll be performing this on so I assumed a dimension of $2m \times 1m \times 1m$ and it has a capacity of 2000 litres of water. For a first estimate, I assumed wall thicknesses to be zero and used Newton's law of cooling, essentially turning it into a floating cuboid shaped blob of water with the transfer coefficient of concrete and the surface area is all six faces of the cuboid ( I don't know if this is even remotely reasonable).
Heat Transfer coeff $= h=12 \mathrm{W/(kg.K)}$
Surface Area $= A=10 \mathrm{m^2}$
Mass $= m=2000 \mathrm{kg}$
Volume $= V=2 \mathrm{m^3}$
I used the equation:
$$ T(t)=T_{env} +(T(0)-T_{env})e^{-t/\tau}$$
where
$$ \tau=\frac{mc}{hA}=\frac{2000\times 4200}{12\times 10}=70000$$
$$T_{env}=281K$$
$$T_0=298K$$
making the equation
$$T(t)=281 +(298-281)e^{-t/70000}$$
and heat loss equation is;
$$\frac{dU}{dt}=C\frac{dT}{dt}= (4200\times2000)\times\frac{17\times e^{-t/70000}}{70000}$$
where $C$ is heat capacity.
Would this equation be a reasonable assumption? Are there any other factors I should take into account?
Also is there any analytical solution for Newton's cooling law in Two layered systems or something, if so where can I find it?


texts: How to calculate the time to heat up a tank using recirculating liquid

texts:
My question is about a tank filled with some liquid (properties of the liquid are known and can be considered constant. Specific heat equals 1.5 kJ/(kg.K)). The initial temperature of the liquid in the tank is 90 ºC. Now imagine that 2000 L/h of this liquid are recirculating, but before returning to the tank they are heated somehow (doesn't matter how) until they reach 240 ºC (assume it remains a liquid at this temperature).

How can I estimate how much time it would take before the tank temperature reaches 230 ºC. The liquid volume on the tank is constant and equal to 10000 L.

It's kind of an open problem (the values are only hypothetical so that the problem can be implement on Excel). How should I start analyzing it? What equations should I be looking for?


texts: water leak through subterranean cable penetrations in concrete

texts:
See the image below for the detail of 4 no. cable ducts that run from a trench in a raft foundation (on the left) through an approximately 1 m square penetration in the raft foundation, through soil (if it had been backfilled) and through an approx 1 m square penetration in the retaining wall for the basement of an industrial structure. At present there is a continuous flow of water through the base of the penetration in the retaining wall.

My questions are:

Given that the structure is approximately 50 years old what are the likely original construction details? My theory is that the cable ducts were fed through, the penetration at either end was sealed with mastic but I am unclear if it would have been possible to backfill around the cable ducts or whether the cable ducts are likely in a void filled with ground water?
What approach could be used to prevent water ingress in through the retaining wall penetration. Is it possible that the existing mastic sealant has degraded with age? Would raking it out and reinstating with a modern product be effective? Is there a system that can be applied on the internal face of the retaining wall that would be effective? Is the best approach leak management to a sump to be pumped out?
If you were to construct this detail today what approach would you take? My instinct would be to use a puddle flange for each cable duct  that was cast into the concrete rather than leaving 1 m square voids to be sealed with mastic. I believe this would have prevented water ingress? What is current best practice for construction these cable duct penetration details?

I apologise for the quantity of questions. I could break it into a series of independent questions if required but I felt it better to keep everything together.


texts:
I have a situation that I am hoping to solve with the use of electric motors, and a variety of controls.
I have a hydraulic winch which turns at speeds from 0-60 RPM.  This winch is coiling and uncoiling a rope.  Under normal operation, it would have anywhere between 200-300 pounds of pull on the rope it is coiling or uncoiling.
There is a situation, in our shop, where we would like to simulate the working conditions of our hydraulic winch.  I would like to attach another electric winch that would pull 200-300 pounds on the rope as the hydraulic winch is unspooling and also keep a pull of 200-300 pounds on the rope as the hydraulic winch in coiling.
What would the simplest way of achieving this be?
Thank you very much for your support.

Hello Everyone,
I would like to thank you all for your great input.
As much as I would love to hang a weight off the end of this winch, which would work out perfectly, there are situation where that setup would not work.
I need to be able to simulate this 200-300 pound pull.
The best way I can describe the situation is this.
Lets say you are on a boat traveling though the water pulling in a rope with a buoy attached in the middle of your rope.  As you are sailing though the water there is a constant pull on your rope but if you stop there will no longer be that constant pull on your rope.  If you are sailing and you winch in your rope, the buoy will reach the winch and get wrapped up nice and tight the way it is supposed to. If the boat stops, there will be no pull on the rope that is in the water allowing buoy to fall forward on the winch as it passes over the top of the winch.  This will cause big problems.
So with all that said, I am trying to build something that can be used in our shop and on the ship to retrieve the system if they have a propulsion failure.
So it needs to be relatively small, shouldn't be a problem with only 200-300 pounds pull and i can attached as much feedback \ encoders on either unit I want.
I have been looking at some oil shear technologies but would much rather do this electrically.
Thanks and I look forward to hearing more about your suggestions.


texts: Method to simulate a dipole antenna in salt water?

texts:
I am looking to simulate the radiation pattern of a 2.7Ghz half-wavelength dipole antenna immersed in salt water.

I've been using Altair FEKO software to try and accomplish this. I've tried two different ideas without much success:

Idea 1) Directly change the properties (relative permitivity, conductivity, density) of the free space medium.

When I start changing these properties far from their defaults I start getting a lot of geometry errors. For example, to model salt water, I give the free space medium a relative permitivity of 80 and a conductivity of 4 S/m. But then trying to solve this model gives "ERROR 114: Segmentation rules have been violated (wire segment is too long)". I attempt to resolve this by shortening the length of the dipole antenna to wavelength/10, but then I start getting mesh errors like "WARNING 18189: The geometry is much smaller than the model extents. This could cause tolerance issues." Is this normal? Do I need to just keep playing with the antenna vs mesh dimensions until it works?

Idea 2) Create a sphere surrounding the antenna and assign the region a new medium with the correct properties.

I create a sphere with a width several times the length of the antenna, but no matter what medium I assign to the region inside, FEKO treats it as a lossy space. For example, giving the region the default free space medium, and the faces are all perfect electric conductor, results in all gain from the antenna being destroyed and "WARNING 3397: The power loss is larger than the active power". Shouldn't a spherical region of free space be treated the same as the rest of the free space geometry? Why does FEKO treat it differently?

I know this is possible because I've read several research papers talking about using FEKO to model antenna underwater, but so far I haven't figured out the key.

Any suggestions?

I'm also open to switching to Matlab if someone believes it would be easier to use that.


texts: Ignoring Mechanical Material Properties and Design Implications, in a Compressor, does the Thermal Density of the Blades Affect Efficiency?

texts:
Consider an ideal adiabatic compressor, ignoring the remainder of the thermodynamic cycle. In this case, the heat flow q into and out of the compressor itself is zero, by definition of adiabatic compression. The output shaft work then is:
$$h_{out} - h_{in} = w_{shaft}$$
However, if we then consider the case of a compressor which experiences no losses excepting thermal inertia and heating. It follows logically that there would be losses to the output work due to heat energy imparted to the compressor itself. My question is, suppose we have two identical compressors, one which is made of Copper, and one which is made of Steel. If we ignore phase changes and assume that both materials can infinitely absorb heat. Will the losses imparted on the exhaust of the compressors be different in any way? Just because Copper will increase in temperature more than Steel for the same input of energy, does this have any impact on the efficiency of a compressor?


texts: Are there different moments of inertia for shapes and bodies?

texts:
I'm confused by this. There is a moment of inertia for a shape, let's say circle:

But if you make it 3D, you have a new moment of inertia:

Is there any connection between these two?


texts: What is the meaning of negative exponents in SI units?

texts:
Please could someone explain the reason for using negative superscripts in SI units, and more precisely when to use negative versus positive?

I do not understand, for example, why the volume of a fuel would be given in m3 but heat of combustion would be given in J m-3.


texts: Solidworks 2D static nonlinear simulation convergence problems

texts:
I'm trying to do the following 2D nonlinear static simulation in SolidWorks (video was made in Ansys): https://we.tl/t-m3XQrUZZ5U
However, I've been getting these convergence problems I can't seem to resolve on my own - see picture below. The setup consists of two horizontal beams with predescribed displacements, clamping a titanium clip.
Especially when the tips of the clip start to touch there are problems. Decreasing mesh size and timestep didn't work (as well as changing about any other setting). I simulated with large deformation option on. I also tried large strain option and reducing the singularity elimination factor. Running this simulation in 3D did converge, but with a significant increased simulation time, which is not desired as I need to do more of these kinds of simulations for my graduation project. I started out with a simplified model without the notches and without friction but that didn't work out either.
Would anyone with simulation experience be willing to help this student, still learning simulation, out? Please find attached the solidworks file: https://we.tl/t-SFwcMZczeV.
Any help is appreciated, thanks in advance! Thomas


texts: How can I separate gear oil from metal shavings to weigh worn metal?

texts: I have tested a gear box for many hours. Where the gears are made of a hardened steel alloy and the housing is 7000 series aluminum. Now I drained the gear box of its gear oil and I need to weight the metal shavings in that oil. So I can put in fresh oil and test the gear box for a couple more hours. And then do the test all over again. Can anyone give me a good idea as to how I can accurately separate the oil with out losing the tiny pieces of metal? I thought I could filter the oil through coffee filters then give it a thorough cleaning with hot water and soap, then drying it in the oven. Can anyone tell me if this is a good idea or can you come up with a better one?


texts:
I love ejection seats and the flying contraptions they usually reside in.  In fact, I like them so much that I want to make my own, despite my profound lack of training and inexperience with mechanical engineering in general. After doing a little research into the materials for my ejection seat, I found a large collection of aluminum alloys to choose from.  Some are fairly simple to eliminate like the 1000, 2000, and 3000 series.  However, between the various grades in the 5000 and 6000 series, I have a lot more trouble.

I read that 6061 is the most common alloy for reasons of weldability, corrosion resistance and a few properties.  Also, I intend to rivet the chair together because that's what I see in my detailed source pictures though I have a little experience with TIG welding so that may be an option too.

In the benign environment of my office, will it really matter which alloy I pick?  Can I just use common 6061 sheet or is there a better, cheaper alternative?


texts: Does a car starter motor use a starting resistor to limit the high starting current? What is the type of connection between field coil and armature? Series, parallel or mixed?


texts: Is there any option other than a gas welder

texts:
I want to repair a dent in a piece of cast iron with brass. I want to fill the site with brass.

For some reason, I want to do it by myself. I can buy an instrument for this work in a limited budget(within $200)

I dont like to buy a gas welder to be used at my home since the storage is a risk.

Is there any other option for this work?


texts: When tolerances are mentioned without +/-, should they be considered as a span?

texts:
In casual conversation, and often in bill of materials, tolerances are specified without the qualifier +/- xx%, often because the specific ± character is hard to obtain (especially in legacy UNIX EDA systems) E.g.

100R 1% 0603 resistor

Is there a convention as to whether this should be interpreted as +/- 1% i.e. resistance value from 99.0-101.0 ohms or as a total tolerance, i.e. resistance value from 99.5-100.5 ohms?

The datasheet should specify this of course, but I was wondering if there is a convention in scientific / engineering speech whether unspecified tolerances are one or two-sided?

Edit: To all: I understand that everyone is trying to be helpful but I not asking for how to solve the problem. My question is literally with regard to whether there are any conventions in interpretation, in electronic engineering, of just "1%" as +/-1% or +/- 0.5%.


texts: Method of Characteristics nozzle - outputs area ratio?

texts: I am designing a rocket engine as my final project at college, and I tried using a MatLab code developed by youtuber JoshTheEngineer. However, after running the code, it seems that the output points and plot show the variation of area ratio (A/A*) along the nozzle length. Is this how the method is supposed to work? My understanding was that the method should provide the nozzle contour, hence the code must output the coordinates of points along the nozzle contour. Is there another manipulation I have to do to obtain the coordinates?


texts:
Abstract:The detergency property in oil comes from a chemical additive called detergent which has a property of preventing the deposition of carbon deposits and wash it away.
There is also this property of lube oil being Dispersant where an additive is added to divide the larger size deposits into tiny particles to be carried in a colloidal suspension evenly throughout the bulk of oil, which can be removed while filtration of the oil.

Question:Can this property of detergency and dispersancy measured so as to ascertain how much or how easily it can react and dislodge unwanted particles in an engine?


texts: Advice wanted on time to digital converters for speed of sound in fluids

texts:
I'm using the speed of sound to analyze the composition of aqueous solutions with sound velocities between around 1000 and 1400 meters per second. It's a process control application with continuous monitoring of a flowing fluid.
The plan is to have two piezoelectric transducers at one end of a pipe with a flat reflector plate at the other end, emit a sound wave from one transducer and detect its reflection with the other. It's done this way rather than with a transducer at each end of a tube so that the effect of the velocity of the fluid on the speed of sound is cancelled between the incident and reflected waves.
The chamber needs to be isothermal to close tolerances, and this limits its length to about 10 centimeters. I need to determine the range between the two speeds with the resolution of at least 20,000 points, ideally more. A time resolution of one nanosecond would be plenty.
I've looked at a number of chips that handle the interface between the transducers and the Arduino and I've identified three that offer the required performance. Those being the MSP430FR6047 and TCD1000 from Texas instruments and the TDC-GP22 from AMS. From the data sheets these all seem capable of doing the job. From what little I've been able to glean from forums, interfacing with the Arduino is quite complicated. These chips have a lot of functionality that I don't require because they're aimed at ultrasonic flow measurement and heat metering, but their temperature handling features are not sufficiently precise for my purposes and therefore I have to do that independently.
Does anyone have any advice about what chip they think would be most suitable, or if they have experienced another chip that would be better?


texts: What is relief amount in grooving operation

texts: Can somebody please explain what relief amount at the end of cut in a grooving operation on lathe is?


texts: I need some help with 'pattern mirror' tool in Solidworks

texts: I drew a quarter of my element and i want to generate the whole part by using 'pattern mirror'. The actual element is totally symmetrical (as you can see in the first image sketched by yellow curves) but in my final results (the second image) that ain't so and I have absolutely no clue why!


texts: What kind of signal is the signum function? A power signal or an energy signal?

texts:
I'm studying "signals and systems". We can indentify two kinds of signals: power signal and energy signal.

The definitions are:

Energy of a time-continous signal
$$ E_x = \int_{-\infty}^{+\infty}{|x(t)|}^2dt $$

Power of a time-continous signal
$$ P_x = \lim_{Z\rightarrow+\infty}{\frac{1}{2Z}\int_{-Z}^{+Z}{|x(t)|}^2dt}$$

An energy signal satisfies $0<E_x<+\infty$ and $P_x=0$.

A power signal satisfies $0<P_x<+\infty$ and $E_x = +\infty$.

Now, if we have a signum function

$$sgn(t)=\left\{\begin{matrix}
1 & if\;t \ge 0 \\
-1 & if\;t < 0
\end{matrix}\right.$$

and we calculate the formulas, then we obtain:

$$P_x = 0 \;\; E_x=0 $$

My question is, as the title said: the signum function which kind of signal is?


texts: How does 4G know the reception of a voice call?

texts:
I know that the 4G network is only for data and doesn't support voice calls. Most of phones switch to 2G/3G when receiving a voice call.

But my problem is how does the phone gets to know about the reception of the voice call when it is in 4G network. We can think, a signal is sent over 4G data to the phone to switch from 4G to 2G/3G. But what will happen if the mobile data is switched off in the device, when receiving a phone call.


texts: What is the purpose of the capacitors on LDO Regulator Circuit?

texts: What is the purpose and benefit of the two capacitors on both the input and output pins of a LDO Regulator?


texts:
In bridge design normally base supports are strong,fixed/rigid. Why did he choose thicker arch sections at middle above mid-river and narrow sections at abutment supports? If he chose a  simply supported condition, then for what structural advantage?

EDIT1:

Could it be some combination of arch and beam design?

Between arch abutments it spans 5 pillar span lengths.Treating main structure as a long span Beam bridge simply supported at ends bending moment at mid-span is maximum so midsection should be designed deeply trussed as done here.

However does it not compromise benefits of pure membrane arch action ( like St. Louis Gateway arch, Missouri design as a catenary) creating stress concentration by lower section property utilization?

Eiffel Rail-Road Bridge Portugal

"In 1876 they designed the 1,158-foot steel railroad Ponte Maria Pia (Maria Pia Bridge) over the Douro River in Oporto, Portugal".


texts:
I have a Proportional solenoid valve that uses a 0-30VDC for control (opening the orifice) I only have capability to provide 0-5V or 0-10V. I need to control the valve using my PC. Is there any DC Power supply device that I can control using PC to provide 0-30V (that I can change continuously as required during operation)? I have tried a voltage multiplier circuit. I am getting the required voltage but the Transistors (BC547) are burning out quickly due to over-current/heating.

I am not a electrical/electronics engineer hence don't know if there is a better transistor or how to choose one.

Hence, searching for the PC controllable DC Power supply. if available.


texts: Ideal op amp circuit with variable voltage gain, how do I calculate the current?

texts:
I am currently calculating various quantities for the circuit shown below. However, I am stuck on how to calculate the current (Ix) and the input resistance (0 output current). The circuit is an ideal op amp circuit.

There should be a virtual short between the two opamp inputs so that in the active region, the are at nearly identical voltages. I am still unsure how to calculate the voltage at the non-inverting input.


texts: Is there any good way to measure humidity constantly in a concrete block?

texts:
So, there is this teacher who wants to test how an chemical compound acts in the velocity of drying in concrete. Basically, i want to measure continuously (it would be great if i could do it with an arduino) the humidity level in a block of concrete.
What is the best option? To use a air humidity sensor (DHT22, for example) or an ground humidity sensor? Or any other better option?
The main purpose here is to store every measure of humidity along approximately 12 ou 13 hours. Any ideas? Thanks!


texts: How do nuclear power plants prevent fuel rods from depleting nonuniformaly?

texts:
Power output of nuclear reactors is controlled by control rods that sit in between the fuel rods:

These are pulled out to increase fission rates - and lowered to decrease them.

The control rods are made from neutron absorbing materials - such as cadmium.

When lowered completely, so many neutrons are absorbed, that no chain reaction is maintained. Pulling them out increases the neutrons that are available for fission.

My question:

The lower tips of the fuel rods will almost always be exposed to neutrons, so these should burn down much faster (have their uranium  fissioned) than the upper parts that rarely have the control rods removed from them. Is there some engineering going on to have the fuel rods burn down at the same rate along their whole length?


texts: Production technology for hexagonal shaft ?

texts:
The shaft is the most important element in my machine, so i rather prefer forging for production technology, the circumscribed circle of the shaft is about 140 mm and the length is about 1400 mm.

What kind of dimensions should i specify on my drawing to help the operator to manufacture it ? The diameter of a circumscribed circle here does't help.


texts:
I understand this is a multifaceted question and I apologize . All of it is relevant to be understood.

On Earth Fly wheel storage devices are used as an alternative to batteries. Even with magnetic bearings these devises expand and contract making the clearance between parts an issue. Between the Earth and Moon temperature can rang from −270 °C and −454 °F.

Maintaining the bearings in them and the weight make them less efficient then batteries. Transporting them while they are spinning is also an issue. Moving parts that touch wear out. Bearing must be maintained and has it own set of issues.

I propose this as an alternative: This type of magnetic levitation below can be used in place of the magnetic bearings at 0 gravity and possibly on Earth or moon. Are flywheels used in space and in this way?

The lower drawn model below on the left will work on Earth but the gravity and air slow it down. No air on moon even better in space. The flywheel can be much heavier and be contained/entrapped using 2 magnetic bases and the magnetic core in the center of the flywheel.

Using timers to apply Gauss to a curved edge of the magnetic core it could be spun faster similar to spinning a basket ball on your finger with out knocking it off the axis, but also like a brushless motor. This would also be easier to transport.

Would there still be any friction other than when electricity is collected or Gauss is applied while spinning? The picture below is my version of a bearingless version of a flywheel storage devise . The design is basic, but is it plausible?  When up scaled? Why not?

I am hoping someone could improve the design. The disks would be 2 parts to a space station. The flywheel would be large and heavy to the point of simulating gravity if you where standing inside the drum also heavy enough where power drawn shouldn't cause a noticeable shift in gravity.  It doesn't have to spin fast if it is heavy. Since the main part do not touch they will last indefinitely. Constructing the magnets can be done in parts.

This link demonstrates well.

https://media.giphy.com/media/OffasXBv2RmOQ/source.gif


texts:
With the start of the leaf raking/blowing season just a month away, I have been thinking of a way in which I could make my old leaf blower more effective so I can spend less time doing leaf blowing. I know that I can go out and buy a more powerful leaf blower, but before I do that there is an idea that I have that I believe will increase the effectiveness of my current leaf blower.
It would involve building an air amplifier attachment for my leaf blower which would increase the overall air flow by making use of the Coanda Effect. I was inspired with this idea after recently watching a YouTube video on how the Dyson air multiplier fans work.
Please reference the drawing below:

I want to point out that this is a cylinder-shaped attachment which would be made out of a lightweight yet durable plastic and that it would be hollow. Also, it would be designed to attach to the standard leaf blower tube which is 3.5 inches in diameter.
Would this air amplifier attachment increase a leaf blower's effectiveness?
EDIT
This attachment would most likely need to be screwed on to the tube or held on with a couple of latches otherwise the back pressure inside of the attachment would likely cause it to pop off.


texts: Cannot Create Centerline between 2 Holes in Solidworks Drawing

texts:
I am new to Solidworks, my part has several holes (created using the Hole Wizard) which needs Centerlines drawn to connect them.

However when I click on the Centerline tool in the Drawing, then click on one hole followed by another hole, I get the error message

Unable to create centerline from the selected entities

What should be the correct way to create the centerlines?


texts: Are there succesful solid fueled internal combustion engines?

texts: Are there any succesful solid fueled internal combustion engines? Particularily, ones that produce shaft power (not rockets and not ramjets)


texts: What are the conditions for a signal to be an energy signal and a power signal?

texts:
I know how to find the power and the energy of a signal. What I have a problem with is knowing whether a signal is an energy signal or a power signal.

According to my teacher, a signal is a power signal if its power is finite (less than infinity) and non-zero and a signal is an energy signal if its energy is finite (less than infinity). What he does not specify is what happens if the energy of a signal is 0 such as in the case of the signal x(t) = 0.

The energy is obviously 0. Is this signal considered an energy signal or the signal x(t) is not considered a signal at all since its zero?

Furthermore, is it possible for a signal to be neither a power signal nor an energy signal?

Thank you.


texts: What loads are office desks required to withstand?

texts:
This question about calculating loads on parts of a desk made me finally ask my first question on SE.

What generally applicable standards are there for office furniture (desks, let's say), that define the loads that they must be able to survive?

In aerospace, the regulations ask for all structural parts to comply with all foreseeable loads in the complete operational scenarios during the entire life of the aircraft (static loads, dynamic loads, fatigue loads, etc); and 1.25 or 1.5 times that load is the ultimate load that each structure must be able to bear (even if for a few seconds).

I'd like to know open source materials, and real life experiences if available.


texts: Rate of flow of liquid nitrogen from a static tank through an orifice in a submerged vessel

texts:
My background is in electronics, not mechanical engineering and fluid dynamics, so please keep that in mind. Also, this is not a homework or academic assignment.

Q: A dewar is partially filled with liquid nitrogen (LN2) and is open to the atmosphere. If a container, open on the top, has a hole in the bottom and is lowered into the liquid, how quickly will the liquid fill the container?

Specifics:
The dewar has an inside diameter of 14" and has 8" of LN2 ( volume ~1200 cubic inch).
Second container is 4" outside diameter, 3.75" inside diameter, 7" height.
A small hole, ~40 mils, is drilled in the bottom of the container.
Container will be lowered into the LN2 to a depth of 6".
Atmospheric pressure: Sea level.

I need to determine the rate of flow into the secondary container so I know how quickly it will fill to a 6" depth (~66 cubic inch).


texts: Sizing a pressure safety valve for two-phase flow

texts:
I understand that valves in two-phase vapour / liquid were sometimes sized by considering the required vapour and liquid flow rates separately, and then adding the results together. But this is now considered an outdated practice.

I have also heard of the homogeneous equilibrium model (HEM), but I am under the impression that there are a number of other accepted sizing techniques.

My primary question is: what are the currently accepted practices / standards for sizing relief devices with two-phase vapour / liquid flow?

Otherwise, if the older techniques are still valid, under what conditions or assumptions behind each technique are they still valid?


texts: What is the specific issue with frequency fluctuation in the grid?

texts:
I understand that if supply and demand are not in equilibrium synchronous generators make the difference by increasing or decreasing their rotational energy - thus changing the electrical frequency in the grid. It is usually noted that a frequency shift $\geq 1\%$ is unacceptable and might damage the grid; however, I cannot find anywhere what in particular such frequency shift can damage. Which components of the grid are the ones we are mostly scared of getting damaged?

I am also curious what are the usual methods of mitigation of such situations, if I understand correctly, if the generated power is much higher than the demand the power stations disconnect and a blackout occurs (i.e. on a very windy night in a country powered by wind power stations). Similarly when the demand is much higher than the supply then some areal blackouts are purposefully introduced to decrease the load.

Lastly, are there currently any methods - beyond classical generators - that are widely used to increase the grid inertia?


texts: When does the minimum temperature in a four-stroke cycle occur inside the engine cylinder?

texts:
I've checked on quite a few places on the net and some say it occurs at the beginning of suction stroke and others say at the end of suction stroke. I believe it to be at the end of suction stroke because after exhaust some of heat absorbed by cylinder from combustion products remains and when suction is completed, the fresh charge will absorb some of that remaining heat thereby making the cylinder cooler. I'd like an explanation with graphs(ACTUAL T-S diagram, if possible would be much appreciated) and also citation of some credible sources if possible. I've uploaded a T-S diagram for SI engine but this is the ideal T-S diagram which like ideal P-V diagram(of otto cycle) misses the portion where scavenging and actual suction occurs after the expansion of remaining gases that remain at the end of exhaust stroke(this difference is clear from other two images of ideal and actual P-V diagrams). Also I'd like to know if there is any difference between its occurrence(the minimum temperature timing) in S.I and Diesel engines.

Lastly this question is a multiple choice question of an exam with options:-
a) End of exhaust stroke    b) end of suction stroke    c) Beginning of suction stroke     d) beginning of exhaust stroke


texts: Is a particular bund/embankment geometry more stable than others?

texts:
I am interested in  structural stability of earthen bunds. They are susceptible to being eroded by water. Let us assume I have a rice field that is surrounded on all four sides by earthen bunds. I have seen in my travels two geometries (shape of bunds). Some are rectangular and others are curved. Is there an objective way to analyze(mathematically I mean) which geometry would be more resistant to flooding i.e. rectangular(or square) vs. curved ? Water can hit the bund vertically from above(during precipitation) and/or horizontally (water from surrounding fields can flow towards a bund)

Here is an example of a rice field surrounded by bunds - Earthen bunds.
This one is a bit curved but I have seen rectangular bunds as well.

Let us assume I have flat surface area.


texts: Why do instructions on creation of roller chain sprocket tooth profile require redundant measurements?

texts:
I'm CADing a tooth profile for a bicycle chainring model and I'm referring my measurements and formulas to these sources:

http://www.gearseds.com/files/design_draw_sprocket_5.pdf
https://data.epo.org/publication-server/image?imageName=imgf0003&docId=2977669

One of them is the main instructional document while the other just presents a drawing of the profile with the same variables and equations as the first one. (though they do use different units)

They ask me to calculate some variables which will provide a graphical Point A and they make me calculate for the Angle B between a Line C and the x-axis with Point A as vertex, and it always ends up that Line C just connects the center of the roller circle and Point A. They also instructed me calculate for a length of Line D which is the same length of Line C from the circle's edge to Point A.

Why can't they just tell me to do that instead? I'm just wasting my time calculating for these practically redundant variables. It's not like they're teaching this for manual sketching, as they specifically use terms that are present in 2D drawing/CAD programs.


texts: Electric Current Based Shape-Memory Alloy

texts:
Would it be possible to create a piece of metal, made out of an alloy or combination of alloys, that undergoes a shape-memory-esque change in structure in reaction to an electric current? Could it also react differently depending on the type or orientation/direction of the current?

Ex:
A wire that, when electricity is passed through it one way, conracts/coils but extends when the currents flows in the opposite direction.

+__________- contracts
-__________+ expands


texts: On a Diesel/hydraulic DMU train what exactly does the “go faster” lever control?

texts:
Let's say that you are driving a Diesel Multiple Unit† with either mechanical* (i.e. an actual gearbox with multiple ratios) or hydraulic (i.e. two or more torque converters) transmission. When you move the “go faster” lever to a higher notch, what exactly is being commanded?

Possibilities that I can think of:

Higher mass flow of fuel into the engine cylinders, whatever happens after that, happens
Engine governor set to a higher rpm, whatever happens after that, happens
Something else

This weirdly specific question does relate to a question presented by a client, but I'm not being paid to solve it.

† My question is specifically about DMUs — and not locos — examples of the kind of train I'm interested in include: Class 150 Sprinter and  Class 172 TurboStar

* Although unusual, and for a long time considered obsolete, there are still mechanical transmissions for this application in production. For example, the Voith DIWARail pack for small railcars, derived from a bus power pack, and I believe that ZF offer a similar solution.


texts: what thickness steel sheet for a motorcycle turntable

texts:
i have a 300kg motorcycle with a 1630mm wheelbase. I have a lazy susan 1000kg bearing, which will be centrally mounted on the steel plate. what is the minimum thickness steel plate at 350mm wide i need in order to support the motorcycle with both wheels off the ground.
I am only 5’ tall and need to keep the turntable as low as possible. I initially considered using wood but the thickness required would mean my short legs wouldn’t touch the ground!
Thanks for the framework suggestions. I can maybe now combine steel and wood into the design to reduce height and weight.
Thanks to all you very knowledgable engineers who have given me quite a bit to think about! I will post a photo when....or if, I manage to make a workable turntable.


texts: What is the pressure-temperature rating for a stainless steel Class 150 nipple?

texts:
Which ASME standard defines Class 150 Nipples - material stainless steel? What is the pressure-temperature rating for such a fitting?

I don't have ASME standards available but I don't believe ASME B16.11 has any mention of double-threaded hexagonal nipples. I am interested especially in pressure/temperature dependence.


texts: How can I set an upper limit on mass imbalance in Fluent?

texts:
I studied a paper about simulation of turbines using Fluent that included the following sentence, which I don't understand:

  All  converged solutions  had  a  mass imbalance  of less  than
  0.3%

What does the mass imbalance of converged solutions refer to?

How can I ensure this condition is met in Fluent?


texts: How to use failure criteria in isotropic material (NASTRAN)

texts:
I'm quite new in NASTRAN enviroment, and I am wondering how to use failure criteria which I can define when creating my isotropic MAT1 material for 1D elements (like CBEAM).

From the Quick Reference Guide, (MAT1) I am able to define 3 stress limits during the material creation.

What type of related output should I expect?
Can I obtain failure indices or security indices? (like PLY composites)
I've tried to launch a SOL101 but I can't figure out how to obtain these values, unless they are in the colums of F06 file named M.S.-T and M.S.-C (I can't find a reference in the guide, though!)

Other types of SOLutions effectively use these stress parameters?
I'm actually interested in SOL111.

Thank you in advance for any help.


texts: Suppose there is a given piezoelectric material and under a given force it produces voltage $V$. If an external electric circuit is attached with load $R$, the current will be $I= V/R$. Also power generated will be $V^2/R$. By choosing $R$ very low, high energy can be obtained. Is this understanding correct?


texts: Force required to vertically pull a post out of ground with various soil types

texts: I am trying to determine the force required to vertically lift a typical traffic sign post (round, square and/or channel) out of the ground based on typical soil types at standard installation below grades depths of 30" and 36".  To make the calculation simpler, assume that the post coming out of the ground is just a 4" stub and that actual sign assembly is not part of the equation.


texts:
I have a question on the Bauschinger effect. Let's say that we have a material with yield stress $400 \,\mathrm{MPa}$, and let's say that the actual applied stress is tensile for starters. If we load the material to the point where the stress is, for example, $500 \,\mathrm{MPa}$, then that means that the loading has surpassed the material's yield stress by $100 \,\mathrm{MPa}$ and that the material has entered the inelastic region.

If the direction of stress is now reversed, from tensile to compressive, the Bauschinger effect tells us that the new compressive yield stress will be lower than the initial one and will be $-400+100=-300 \,\mathrm{MPa}$.

What I want to know is: What happens if in my initial loading of the material I don't surpass the yield strength? In other words, if yielding occurs at $400 \,\mathrm{MPa}$, I apply less than that ($350 \,\mathrm{MPa}$, for example). If I now unload and start loading with compressive stress, does the Bauschinger effect apply? Or is the yield stress for compressive loading still $-400 \,\mathrm{MPa}$?

Thanks in advance.
Note: I don't know what tags to add, so if you know of more suitable ones, please add them.


texts: shape of cylinder in the fluid mechanics

texts:
in the following picture, we should find the viscosity of fluid and we have to have the Area surface of cylinder that is in touch with the fluid.
the area surface depends on the bottom of the shape.
but i have no idea what's the shape of this cylinder. what is that curve on the bottom of cylinder? does it mean that cylinder is empty inside or what?

and the solution of this problem:


texts: What is the use of v notch in Izod charpy test

texts: While testing the toughness of brittle material by izod or charpy test why do we provide v notch?


texts: How to compute the mass and max speed of a ball moving on a circular track under the influence of gravity and a spring

texts:
How to finish part (a) and (b) of this dynamics problem?

There are no solution or answer in the book...

My professor say that this problem is very tricky, don't even try by yourself.


texts: How are small refrigerator compressors started?

texts:
Small refrigerator compressors in the US generally all have exactly the same design and I am trying to understand their starting mechanism better. How exactly does it work?

What I generally understand is that the motor is a squirrel cage motor which has two sets of windings in a "star delta" configuration. On the outside of the motor is a small black box with a two holes that connect to two pins coming out of the compressor called the "positive temperature coefficient relay". One pin is the hot for the "star" windings and the other is for the "delta" windings. When the compressor starts the PTC directs house current to the first pin very briefly, then due to the wire getting hot, quickly switches over the current over to the other pin (the "run" pin). Is this basically correct?

If so, my main question is what kind of star delta motor is being used? I believe there are 5 different types: Normal, Enhanced, Combined, Partially Wound, and Uninterrupted.

Since there are two sets of windings in star delta motor, that would seem to increase the weight of the motor a lot, but makes it cheap to start it, since you only need a very cheap, small relay to do it. Is that the tradeoff being made from a design perspective? I assume that in operation only the run windings are used, so the start windings essentially are dead weight at that point, is that right?


texts: Is there any reason why "inner-flange" style trains are almost universal?

texts:
There's basically two ways train wheels can operate, the flanges could be either "inner" or "outer".

Switches can be made in equivalent ways for inner and outer flanges.

We could expect that, just like some countries, as well as different railway companies within countries, picked up different rail gauges, they could have also varied between inner- and outer-flanges railways.

We could imagine that, just like today some countries have left-hand and right-hand traffic, there would be inner and outer style rail wheels. Except this is not the case, the "inner" style is almost universal. Almost, because the "outer" style indeed did exist in railways' debuts.

Is there a technical reason that makes the "inner" style preferable ?


texts:
I would like to get my hands on a mechanically-set timer (wind up is fine, so that it's self-powered) which sends a small electrical pulse to a mag-lock once the timer goes off, thus causing the mag-lock to open. Is there anything out there that does this?

If not, what would be the cheapest / easiest way to replicate such function, i.e. some mechanical way to produce a small electrical impulse once a mechanical timer finishes. I don't mind electronic methods, but since this is for heavy outdoor use I'd prefer a purely mechanical setup.


texts: Real world applications where one would use a force function in PLC programming?

texts: I'm curious about which scenarios one would use a force function when using a PLC programming interface. Examples pertaining to process engineering, manufacturing, or industrial settings would be ideal.


texts:
I am modellign some examples using the modelling language Modelica. Unfortunately, I am not an electrical engineer, so it is hard to understand the physical behavior of the following example (DC motor):

Where emf "transforms electrical energy into rotational mechanical energy".
The model "emf" looks like this:

The input voltage is plotted in the following graphic (top).
I dont understand the following things:

Why is the current zero in steady state?
My interpretation: In steady state, the voltage input is equal to the voltage drop at the emf. The angular velocity is proportional to the voltage drop at emf.
What is the "emf model" in a real DC-motor?

Thank you very much for your help


texts: Torque Required for a stepper motor to rotate a socket wrench ratchet around an axis point

texts:
I'm trying to build a kinetic machine that rotates socket ratchet tools (e.g. https://en.wikipedia.org/wiki/Socket_wrench) to make a bunch of ratchet 'clicking' sounds for an art project. I'm trying to determine the proper stepper motor to do the job so I'm mostly looking at how much torque will be required. I just wanted to go through my calculations to see if I'm estimating the required torque properly. NB: keep in mind I'm not taking into account the friction imposed by the socket clicking mechanism....
I'm modeling the ratchet as a lever with equally distributed weight (M=1.4 kg) and of Length=R=0.475m) to calculate the moment of inertia for a lever:
I = (1/3)MR2 = 0.089 kg-m2
If I want to be able to rotate the ratchet, I have to apply acceleration to get it moving from rest. I want it be able to make one rotation per second. alpha = 1(rev/s)*2$\sf\pi$/1s = 2$\sf\pi$
Therefore, I'm estimating that the torque needed to get the ratchet to start moving would be T >= I*alpha = 0.56 N-m . Does this seem right?
Also, I'm wondering how I can reduce the torque constraint. For instance, if I attach an arm appendage to the shaft on the motor so that its pushing/rotating at the edge of the socket wrench, it seems like this would significantly reduce the required torque? How would I factor this into my calculation?
Any advice would be super appreciated! many thanks in advance!


texts: What is the load response of a threaded fastener?

texts:
Due to the fact that pipe flanges rely on bolts, and bolts rely on friction, it seems obvious to me that in deflecting to meet the load, the nut will immeasurably turn.  So my question is - how much?

In other words, given a time based varying load on a given threaded fastener, what would be the rotation of the nut?  Has there been any experiments done to show an equation between a simply varying load (like a sine wave in the axial direction) and the rotation of a threaded nut?


texts: How is this aluminum heater mounted to the stainless plate?

texts:
I'm looking for a way to mount a 1000W electric heater to a stainless base. Electric kettle heaters could fit my requirements, but I'm wondering how the Aluminium heater is mounted to the stainless base.

The pictures below show a kettle heater on a stainless base. The steel is SS304 and the element's metal is a manganese-aluminium alloy.

How is it mounted and what is the maximum temperature it can sustain?


texts: What is strain/loading rate dependence/sensitivity of compressive strength of brittle materials?

texts: What is the definition of strain/loading rate dependence/sensitivity of compressive strength of brittle materials? Is it general strain/loading or it is specific for the brittle materials?


texts: How do I get data from my Hardware to server or so?

texts:
Brief I am actually of 17 not even in college but I have dream for making my project/dream/aspiration/or So to come true so I am thinking of making a device that performs a function say like Thermometer measures Temperature, now working and doing the function is not a concern of now (a Question for me), the thing is if I got the data of Reading of final Temp (assume it has performed its temperature calculation and given output [Yep its digital]) so now it gave me some value x .

Problem I want to get this value x into my server or website (maybe I am unable to express it but I want to get it to me through Internet) and store that value for data of  Person P so , I am not sure how I would achieve that. Assume all calculation and functions are done and are independent of device now I just need to know how to store that value for use?  Would it require something like connecting it to a wifi card or similar and making an OS (Till now this has came across my mind )


texts: What is the difference between a piston and a plunger compressor/pump?

texts:
My research has found a Quora link and another source giving two different, albeit not contrasting, definitions. Also, as far as I have seen, looking up "plunger compressor" also refers me to pumps.

I am looking to understand the proper definitions, and see some animated GIFs should you have some, that exactly tell these two apart.


texts: Why wont Petrol engine run on Acetylene?

texts: Boiling temperature of Acetylene is -84°C and that of Petrol is 95°C (at Atmospheric Pressure). So the spark is efficient to ignite the compressed Acetylene and run the Engine. But why wont that work ? Is any other factor that I miss or misunderstood ?


texts: How to analyse an electronic circuit in a more intuitive way?

texts: I want to understand how to analyse complex circuits (for example with diodes, transistors,  amplifiers...etc) in a more intuitive way. My question is not about application of the basic principles of electronics, but about reaching the intellectual prespective of my professor, who apparently assume I would understand his "linguistic" analysis of the circuit, while what I only learnt is the robotic mathematical analysis of circuits. I think its about reaching a new abstract level of thinking, in which new but larger elements of electronics emerges. I am not writing here to get an answer. I am asking for books, from which I can reach that level of thinking.


texts: Why loads in serviceability limit states usually don't include factors of safety?

texts:
For example, characteristic combination found here:

It can be seen that the dead loads $G_k$ are taken as the characteristic values instead of multiplying them by some factors of safety as in the case of ultimate limit states. Why are loads serviceability limit states taken as characteristic values instead of applying partial safety factors into their values?


texts: A stable transfer function which diverges?

texts:
This question might sound stupid as I'm more of a software guy and never really had to do control engineering (besides the 101 classes).

So I have a second order system I could approximate, with the following denominator:

$$s^2 + a_1s + a_0$$

Both $a_1$ and $a_0$ are positive, which means, for a 2nd order system, that it is stable.

However this system's input is a motor's command (not a speed but a PWM cycle value), and the output is the robots angle.

Technically, my angle will go to $+\infty$ with a constant input, which means my system will never stabilize. So the system should not be stable.

Besides, plotting my transfer function's output to a constant input using scipy gives me the expected result (an angle which ends up growing linearly as the speed stabilizes).

So what am I missing here? Is my model completely wrong? Or did I miss something on the definition of "stability" itself? It would make sense if I worked on the speed but the variable I work on is the angle.


texts: Is it possible to store leftover pressure from burning a propellant in a pressure vessel?

texts:
Say, in a firearm, after giving off a shot, if the barrel were to be closed off, does there exist a way to store some of it in an external pressure vessel, without requiring a mainly-external source of power and complex machinery?

Forgive the possibly stupid question, I'm a bit of a layman as far as engineering goes.


texts: Large deflection of a cantilever beam with distributed normal load

texts:
I have a strip of stainless steel encastree'd at one end to which is applied a constant pressure on one side, and I need to know what the deflection equation y = f(x) is at equilibrium.
If the deflection was small I would be able to use one of the very well known deflection formulas which assume vertical loads, but it isn't.

I am trying to work out the bending moment M=f(x) using integrals to use:
$$y(x)=\int\int_{beam} \frac{M}{EI}dx^2$$
But I'm getting more and more confused. What is the right approach to solving this problem?

Here is a diagram:


texts: Performance of RC car under different gear ratio, measured data vs hypothesis

texts:
Assuming the driveshaft of the rear wheeled drive RC car follows the linear DC motor theory for stall torque and no-load RPM, also voltage supplied is constant and no inductance as well. Note: the motor is running above its operating voltage 3V, the motor voltage supplied was measured 5V.

Motor used: product.mabuchi-motor.com/detail.html?id=9

Forming hypothesized result:
speed are directly proportional to voltage, I directly multiply the voltage ratio with the expected speed then multiply again by the gear ratio. Gear ratio was verified by calculating its' teeth. Actual applied voltage was measured using a multimeter and measure the voltage across the motor. The hypothesized stall torque were also multiplied by the same voltage ratio and the gear ratio.

The base of this experiment uses the  formula

ω=Vk-Tk2*R

where the ω is the no-load speed, v is the voltage, k is the electrical constant or the torque constant assuming they are equal to each other.

Hypothesized results of a 7.3 gear ratio
Stall torque=0.065

No load rpm=4200

Measured result
Stall torque=0.02

No-load rpm=6500

The stall torque is measured using an arm and applies the force on the weight scale on both sides. The no-load speed was measured using a non-contacting tachometer. It is found out that the no-load hypothesized speed is less than the measured no-load speed, the stall torque of the hypothesized result is higher than the measured results which is expected, because of power loss.

So, the question is why the measured no-load speed is higher than the hypothesized speed? Is it because of inaccuracy or some unaccounted factors?


texts: Flow velocity in exhaust chimney - typical design value

texts:
I'm looking at a project where stationary CHP engines will be replaced, leaving as much of the infrastructure in place as possible. Current exhaust velocity in the chimney is ~42m/s and it will be a bit higher (~47m/s) with the new engines. I've seen 'around 40 m/s' as a typical exhaust velocity to design the chimney for, but I've also seen far smaller values and none of this with a source.

What is a 'good' design value for the exhaust velocity? Please provide a source/and or reasoning!


texts:
What order of magnitude would common strains take on within concrete bridges? I am looking for types of strains that develop over longer periods of time as well as strains due to dynamic loading.

Wikipedia states the following on their page on concrete creep and shrinkage:

  Changes of pore water content due to drying or wetting processes cause significant volume changes of concrete in load-free specimens. They are called the shrinkage (typically causing strains between 0.0002 and 0.0005, and in low strength concretes even 0.0012) or swelling (< 0.00005 in normal concretes, < 0.00020 in high strength concretes).

I suppose this is a type of strain that develops over longer periods of time. How about strains due to earthquakes?


texts:
I have a quick question guys. I am gonna select a brake but I am not sure.
A Crane Hoist motor has a rating of 300 HP and maximum speed of 1800 rpm. This motor is attached to a gearbox with a perfect (100% efficient) reduction ratio of 53.739:1. The API 7K specifications call for a safety factor of 2:1 (200% of motor full load torque) static holding torque from the brakes. The lining coefficient of friction is 0.40 (static) and the brake shoe face is 6.0 inches wide. Two (2) brakes need to be installed diametrically opposite each other on a large disc mounted directly to the cable drum (on the output side of the gear box).
Which disc diameter, and resultant brake torque is fine?


texts: What is the smallest grain size achievable using mechanical methods?

texts: What is the smallest grain size achievable (both theoretical and practical) using mechanical methods to crush a fracturable mineral composed primarily of a single molecular species? Example minerals include: calcium carbonate minerals such as limestone or chalk; silicon dioxide minerals (quartz, sand); diamond (carbon); sapphire (aluminum oxide).


texts:
I have this setup:

-Pully with a mass attached.

-Worm gear drive to lower the mass with a constant speed. (Section A-A)

Now if we look at the cross-section A-A, we can see the worm gear drive:

M1 is the torque applied by the mass on the pully and hence on the gear.

M2 is the torque applyed by the worm gear.

Now my question is:

If M1 > M2 is it still possible to lower the mass at constant speed ? ...or in other words, is it possible to make the gear (above the worm gear) turn at a constant rotational speed ?

...or will it just block the system due to friction ?

I will rephrase my question: Let's suppose it is a autolocking worm gear, how can I calculate how much M2 needs to be for the mass to lower at a constant speed ?


texts: Do outer fillets|chamfers also reduce stress as inner ones do?

texts:
I kind of have an intuition or at least imagination about how fillet|chamfer of inner edges|vertexes reduce stress (concentration).

But does that apply to outer edges|vertexes aswell? Maybe to a lesser degree or not at all?

So should one use outer fillets|chamfers for this reason?

(Lets take a thin hollow brick-shaped object (case or box) as an example.)


texts:
By using, transformation of the stress tensor property, the stresses can be calculated for transformed orientations. The properties are unique in case of isotropic in all directions.
But what will be the case for which the orthotropic material is transformed? How the transformes stress matrix can be calculated for it?


texts:
I have begun to study control engineering by several books and awesome youtube videos by Brian Douglas. I love them because they give me new understanding of math that I learned before but I still can not get the point of what actually control engineers do.

What is meant by systems here? I mean all examples always are just physical systems like springs and etc, but all of them are governed by physical laws and no matter how dissatisfied with output we are, we are not able to modify physical laws. And in the case of, for instance, mobile robots what do control engineers do? Deriving PID coefficients? I feel like missing the most crucial part of it.


texts: How to deal with inverse distributed load ramp starts and ends somewhere along the beam?

texts: I know how to solve it by moment line methode but i want to use singularity function here and i'm very confused. My strategy consist of writing the correspond singularity function for each element but i have absolutely no clue how can i write the right singularity function for the inverse ramp distributed load at the right side?


texts: Ultrasonic transducer is used to detect flaws. What is the smallest flaw that can be detected by ultrasonic technology? One thing I know is that higher the frequency, higher is the sensitivity of the transducer i.e. smaller is the size of the flaw it can detect.


texts: Schematic Reading - Fluid Control Limit Switch Question

texts: Does limit switch LS1 remain pressed on until the piston moves to LS2?


texts: Why Does Particle Size Matter For Bridge Pillars here?

texts:
I was watching this engineering video here and it talks about a technique used to prevent the pillars of a bridge from falling over in an earthquake. The pillars of the bridge are partially submerged under water, but instead of resting on sand at the bottom, they actually rest on a bed of gravel just above the sand. The rationale for this is that gravel has a larger particle size than the sand below it and therefore the pillars are less likely to fall over when they shake and move.

So my question is, why is it easier for pillars to move on gravel than sand? What role does particle size play in this? Does it reduce the friction when the pillars slides and if so why? It feels like this question should be obvious but I can not seem to fully understand why.


texts: Why is the wheel lug count on vehicles increasing over time?

texts:
There seems to be a very strong trend of the number of wheel lugs on cars and trucks increasing over time. For instance, many small cars in the 80s used 4 lugs, but have since switched to 5 (e.g., Honda Civic, Volkswagen Golf).

More stark examples can be seen in trucks. Consider the M35 series of trucks used by the US Army. The standard model weighs nearly 13,000 lbs empty, and is capable of carrying a load of around 5000 lbs. Its wheels use 6 lugs. (See top photo)

The latest version of the Ford F-150, a truck weighing about 4500 lbs with payloads in the 1500-3000 lb range, now has 6 lugs. (See center photo)

Meanwhile, a vehicle more comparable in weight and cargo specs to the M35 is the Ford F-550. It has a Gross Vehicle Weight Rating of 17,500-19,500 lb range. It uses 10 lugs per wheel. (See bottom photo)

(credits: Wikipedia & ford.com)

So why the lug inflation? This answer states "To some extent, the number of bolt studs depends on the anticipated torque on the wheel." While it's true that engine output and braking power have increased over the years, have they really increased enough to merit a 66% increase in the number of lugs in this example?


texts: Why do electric trains arc at high speeds?

texts: When I watch videos of high speed trains I always see explosions of electricity near the top, or arcing. Why does that happen? I know that the Acela does it a lot but other high speed trains have it, too.


texts:
Trying to find examples of structures, components etc. in plane strain (under normal loading conditions).

Is a thin-walled-pressure-vessel in plane strain?

(I thought it was plane stress but could be wrong)

regards


texts:
I have been repeatedly told when dealing with some data for Navigation purposes that I can assume it follows a "bicycle model". I am not very familiar with vehicle dynamics so I consulted online. I saw many different models varying on the level of sophistication but most of them seems to consist in planar Dynamics similar to the following:

\begin{equation}
\begin{bmatrix}
x_{k+1} \\
y_{k+1} \\
\theta_{k+1}
\end{bmatrix} = \begin{bmatrix}
x_{k} \\
y_{k} \\
\theta_{k}
\end{bmatrix} + \begin{bmatrix}
v\cdot\Delta t\cdot\cos{\theta_k} \\
v\cdot\Delta t\cdot\sin{\theta_k} \\
f(\gamma,v)
\end{bmatrix}
\end{equation}

where $\gamma$, and $v$  are the steering angle and the velocity, both inputs from the vehicle sensors, and $\theta$ is the angle respect to the origin of a fixed frame. $f(\gamma,v)$ is some function relating both angles.

My doubt arises from the fact that the data I have been granted contains only the following fields: $x$,$y$,$\theta$. My assumption is that, if we know it must follow a bicycle model it should hold a correlation like the following:

\begin{equation}
\begin{bmatrix}
x_{k+1} \\
y_{k+1} \\
\theta_{k+1}
\end{bmatrix} = \begin{bmatrix}
x_{k} \\
y_{k} \\
\theta_{k}
\end{bmatrix} + \begin{bmatrix}
d_k\cdot\cos{\theta_k} \\
d_k\cdot\sin{\theta_k} \\
\Delta\theta_k
\end{bmatrix}
\end{equation}

Where $d_k$ and $\Delta\theta_k$ are known at every time step and are the distance traveled and the change in the angle respectively.

If I generate data this way, starting from an initial point $(x_0,y_0)$ and building up, it doesn't seem to correlate well with the actual data I have been granted.  My question is if the deduction exposed has any conceptual mistake, so I can clear out if the problem is that the data given is very noisy and deviates after a while or that what I think is a bicycle model is not


texts: Measuring longer distances with high accuracy

texts:
I am involved right now in the fabrication of steel structures on the order of 5-50 feet long. Presently, we measure these structures with garden variety commercial tape measures. Most of the time, we work to a tolerance of about +/-1/16" and don't have any problems. Recently, we're trying to make some items to a very high tolerance (at least +/- 1/32", approaching 1/64" or .016") This tolerance is due to visual not mechanical criteria, but it is still very important to our management.

My question is, how can we reliably measure these sorts of distances with that level of precision? I'm prepared to order some NIST traceable tape measures, but it's not clear to me if they'll really improve the situation. Are there other technologies or techniques that could practically be applied in a fabrication setting? Are any surveying tools accurate enough to solve the problem? Cost is obviously a factor, but we're more concerned with repeatability and robustness than price.

I realize this tolerance will sound ridiculous to most, but I imagine that some other industries may have to perform similarly, perhaps large engines for ships or power plant components?


texts: My first post here. I'm curious about how power is balanced in multiple diesel-electric locomotives. I understand to that two locos can be ganged in terms of controls, to set speed etc, so that one set of driver controls manages the whole pulling group. (sorry, I don't know the correct vernacular) How is it possible to ensure that each is pulling it's weight evenly compared to the others in the group. Or, put another way, how can I avoid one loco pulling at 5000Nm and a second pulling at 6000Nm. Is it possible to read the tow force in the couplings?


texts: Beam with internal hinge - Reactions help

texts:
can someone explain why the highlighted area (at Mb=0) is - 5x2 and not positive? Since the rest of the loads(and the rest of that very same load) pointing down were documented with a +,
I dont understand why this part is calculated with a minus.

1:

Thank you!


texts: How to create rotating, artificial dipoles?

texts:
The electromagnetic field can be thought of as a superposition of light waves.

I am attempting a physical Fourier Transform - i.e. take simple plane waves of the electromagnetic field (a.k.a. light) and recreate basic fields by superposing the plane waves correctly.

My background is in theoretical physics and so I have little to no knowledge of applications. I know that the field of a rotating electric dipole becomes the simple plane wave I am looking for at large enough distances.

So my question is: How do I actually create a rotating dipole field, or do you have a better idea that suits the application?

I do not wish to use LED's due it's quantum nature and I wish to stay within the fuzziness of classical mechanics.


texts: How to move a thin metal piece with a tiny string or anything else?

texts:
Recently I was experimenting with a metal piece, and I came across a challenge.

A small piece of thin copper metal (5cm x 3cm x 0.2 cm) has to be pushed forward and to be rotated. The problem is how to get a force behind the metal piece and have a force to rotate it. The metal piece must go from left side to the right side of the picture2.

The initial idea was to bind the metal piece with a metal bar and to rotate it so that metal will rotate accordingly. However the bar is too thick. I need to use  a thin, ideally <5mm, string, metal piece or anything else to control (to move forward and to rotate) the metal piece (see picture below). Using a 0.2 cm copper wire  after tying a knot with the metal piece I failed to be able to rotate.

Can you give me some hints what kind of thin string or bar or anything else I may use to accomplish a forward movement through the gap of 0.5 cm between object 1 and 2 (see picture 2) and the rotation of the metal piece afterwards?

Picture 1:

Picture 2:


texts: Should I reject a concrete mix design for having too high of a compressive strength?

texts:
I usually design precast concrete members for the common concrete strength of f'c=4,000 psi at 28 days. Occasionally, a mix design will be submitted that has a very high strength. In one case, the mix that was submitted had a history of cylinder breaks above 7,000 psi. This is 175% of the specified strength!

Normally in engineering extra strength is good, but this seems excessive. Steel grades typically specify a strength range (min and max), but I have never seen a maximum compressive strength in a concrete specification.

Should I reject these very-high strength concrete mixes?

What could be the complications of too high of a compressive strength?

There are only two possible areas of concerns that I can think of:

Modulus of Elasticity is directly related to strength. A high strength may cause the concrete to be more prone to cracking (serviceability concern).
Un-designed high strength may be detrimental in seismic design where you want members to fail in certain locations and in certain modes.
Note, my situations typically include moments (either beams or beam-columns). There likely wouldn't be any concern in a purely compression member.

The reason for submitting such a high strength mix seems to be that the precaster wants to get the piece out of the form quickly, so they add lots of cement to insure that the strength requirement is met.


texts:
I encountered a problem in measuring electrical energy using a multi ratio current transformer (CT). The catalogue of CTs is unavailable.

I have little information about the type of CT I am using. I have several questions about this matter. Firstly, the CT I work with has 7 connections:
X7,100,200,300,400,500&600.

The connection for ratio 100/5 was on X7 & 100. Something that is confusing  me is that X7 a common connector and if connection X7 to 100  measures 100/5, are other windings from 200 to 600 in circuit or open? If they are in circuit how does it produce a 100/5 ratio, and if they are open how it that possible for a CT?

Secondly, the power transformer has delta connections and the CT connection is a Star. After I have connected the meter to the CT I get an error in energy metering. Is it possible that this error is due to the star connection of the CT and should it be a delta connection, as for the power transformer?

Its impossible to change the CT connection to delta. Can I define any coefficient factor to remove this error with out changing the circuits?

The power transformer ratio is 14400/3300, with a delta connection and the
CT's ratio is 200/5, with star connection.


texts: Choosing sides of a shell and tube heat exchanger for oil cooling

texts:
I recently took a quiz from POWER magazine that asked the following question:

In a typical cooling system for lubricant oil in a gas turbine, which configuration is preferred to prevent leaks and contamination?

There is no clarification about what we are preventing leaks or contamination to or the type/size of the gas turbine, but their "correct" answer was to put cooling water on the tube side and oil lubricant on the shell side. They did not provide any further explanation.

I don't see why this would be the preference. There are more consequences of the water contaminating the oil, so you should put the higher pressure oil through the tube so if there is a leak oil leaks into the water. Plus, if the oil goes on the shell side and is higher pressure, the exchanger will cost more because there is more material that needs to be able to withstand a higher pressure. Lastly, I would assume oil will be more prone to contaminants than water and more fouling will occur on the oil side. Thus, you ought to put the oil in the tube for maintenance purposes as well. Am I missing something here or did they select the wrong answer?


texts: Designing bulk material handling system for injection molding

texts: does anyone have any resources for designing a bulk material handling system for an injection molding outfit? Currently we get material in gaylords and vacuum it to the hopper on each molding machine independently. I would like to start buying pellets by the truckload and stored in a silo to be fed to each machine from a central location. I am unsure of what equipment I would need other than the silo itself to do such a thing. Any leads?


texts: Common points to consider when building a window seat

texts:
I am trying to construct a window seat like this one:

I live in Canada.

I was wondering what are the common construction code points to consider on this one?

Materials - does it matter if this is just a seat and not a bearing wall, I was planing 2x4s from Home Depot.
Screws vs Nails - I was thinking screws with pre-drilling.
Framing - should I follow the spacing guidelines for the wood frame or as long as it's sturdy it's all that matters?

Electrical Heating Element

I also have an electrical heating element attached to the wall right where the seat will go, so I was thinking to move it onto the face of the seat once completed. Is there any specific plating that has to be installed to drywall?


texts: Identifying reason for instability in Sensing System powered by Wall Wart

texts:
Currently I  am working on a capacitive sensing and actuation system powered both by battery and AC/DC (Wall Wart) power adapter. The system works well when powered by battery and bench top power supply. The system sometimes behaves unpredictably when connected to AC/DC power adapter.
The AD/DC power adapter is 6V and is rated at 1000mA. The capacitive sensing/scanning  part of the system draws less than 1mA. The sleep/standby mode draws in the uA range. The actuator needs about 500mA for a very short period and activated sparsely. About 50 times in a 24 hour period.  The actuators active time duration is about 30 milliseconds.
I have measured the voltage and current usage with a multimeter, I don’t see any issues.
Any thoughts on what might be causing the instability of the system when used with an AC/DC adapter. Thought on next steps to identify the issue(s) and develop a solution.
Thanks in advance for your help!


texts:
There are several machines that have (rotating) cutting blades. For example the kitchen aid Vorwerk Thermomix can cut pieces of Food in hundreds of pieces within a few seconds. But why it is so?

If the blade hits something, there must act some Forces that cut it into pieces. How to compute the Forces that act on a blade to the Thing that the blade is cutting? Can I also compute stress values during the cutting process?

Is there any literature in Engineering mechanics that unravels the mystery of cutting?

And I wonder why knives are classified with Rockwell hardness. I would be happy about a Basic introduction into this topic.


texts: Estimating trunk rotation using frontal and sagittal views

texts:
I am doing an experiment regarding elbow flexion's effect on peak sprinting velocity and we want to measure trunk rotation and shoulder rotation during our trials. We don't have an overhead camera so we have to make do with cameras in the sagittal and frontal planes. Is there a way of estimating the trunk rotation and shoulder rotation this way? Perhaps using angular area and estimating based on the known width of the participants and distance from the camera (although my geometry skills aren't good enough to find a closed form for any such equation)? I can't think of any other way to do it. Any suggestions would be much appreciated.

Thanks


texts: Diametrically magnetised ring magnet, opposite poles on the inside?

texts:
I am wondering about the magnetic field on the inside of hollow magnets. As an example, will use a ring magnet. In a diametrically magnetised ring magnet, does the magnet have the same pole on the inside and outside diameter, like this?

Or, does it have opposite poles, like this?


texts:
I am a complete solidworks novice trying to create the part pictured in the orthographic schematic below but i am really struggling. I hoped someone might be able to guide me in creating this part.

I began by creating a sketch as follows but i get stuck after this. I'm not sure how to align the top two circles in the center of the plate or how to create the rounded edge on the bottom of the plate.

Any help would be greatly appreciated!


texts: Identifying a connected plate on a gear liquid-metering pump

texts:
This is part of an electric resin-extruding machine.

What's the part, and if possible, who makes it?

Any additional information regarding what the part is, or what the assembly is called, is greatly appreciated.

Here's the part:

Here's the back side:

Here's where it connects:


texts: What is the purpose of digging up trench and then filling with something similar to asphalt crack filler?

texts:
Recently there has been road construction around on the main road leading into my office building. I observed the construction crew removing asphalt in the form of a trench as showed in pictures below. Later on they filled up with aggregate and poured a layer of black tar and filled with something. The trench has been filled and resurfaced in line with the existing road surface.

Attach is the before picture (Satellite) captured from google maps.

Attach is the before picture (Street) captured from google maps.

Question: The rain water is being directed to a near by manhole. What is the engineering explanation for digging the trench later on was poured with liquid tar (asphalt crack filler)?

References:

Practical Guide to Street Works


texts: Does a rotating platform on a space vehicle affect the vehicle's trajectory?

texts: Recently I watched The Martian and the space vehicle Hermes in the movie had a rotating platform. I wonder if that would significantly cause the vehicle to be inclined in direction? Does a spinning platform/living space on a space vehicle, used to provide artificial gravity, create momentum that inclines the trajectory of that vehicle?


texts: Will 25% ammonia vapor balance water vapor between 350°C - 550°C corrode 304 SS? If you know the answer how did you find it what was your source or equation or book?  Will it cause pitting or stress corrosion cracking as it moves through a 304SS pipe?


texts: Need help identifying this vacuum chamber flange

texts:
I know this might not be the most ideal place to ask this question, but I couldn't think of any place better.

I recently purchased a high vacuum chamber setup and have been disassembling it for transport. I removed the hot cathode ion gauge, and then on further inspection, I realized it used an unfamiliar mounting flange. It is a gendered connection. Does anyone know what type it is?

I was weary of trying to remove what looks like a brass gasket. It's pretty thin.

No Conflat style knife edges, but the edge on the first step is fairly sharp, and might ramp upwards (hard to tell)


texts:
I'm trying to solve this

which is to find the total deformation of the bar.

I'm trying to implement the finite element approach, but I am getting way too large of numbers. Here is what I did in Excel.

I thought my units were wrong, but they seem to be fine. The only difference from the other problem I solved was that the second boundary condition was supported; this one has a free end.

Thanks for any help.


texts: Can shear links be designed to hook between inner layers of top and bottom reinforcement?

texts: I am tasked to design a bridge pile cap. Shear links are required. However due to heavy reinforcement used, contractor requested to hook the links between inner rebars to ease construction. Is this allowed in British Standard? How should this be taken into consideration if it is allowed?