texts: I'm working on a project to make a Heads Up Display in my car.  I need a way to present my project in front of my class, for I obviously cannot bring my car into the presenting room.  My professor told me to look into an OBD-II simulator, and since then everything I looked into has a VGA connection(like this one: https://www.sparkfun.com/products/9555).  I've tried looking into this, but I was not able to find anything.  Everything that I read talks a lot about VGA, but never explains why OBD-II used VGA.  It seems to me that an OBD-II connection is completely different from a VGA connection, and a VGA is for old computer monitors. So my question is: what are the similarities between an OBD-II connection and a VGA connecting, and why do these simulators use a VGA connection?


texts:
I want to build a professional CNC router for my garage.

I want to use the residential split phase configuration for power to my VFD and industrial power supplies.

I cannot find any straight answer regarding connecting 240V 1ph (L/N/E input) apparatus to 120V/120V (L1/L2/E).

Can I feed the other line to neutral terminal?

Step-up transformer is out of question since it's high current draw.


texts: How to find old (especially Soviet/Russian) blueprints

texts:
I am interested in old blueprints, especially if related to aerospace (and from the old Soviet Bloc), things like these: Vostok blueprints Soyuz blueprint.
Does anybody know if there is any methods to find them, if they are public domain/publicly available etc.?
They look like "official" documents, or at least made by someone in the field, as they are technical drawings with all of the trimmings.
Also, are there in general online repositories of old blueprints that can be publicly accessed?


texts: How much does loading a load cell in other directions than the direction it was designed for effect the readings?

texts: I am looking into using this  TAL230B miniature type load cell to measure forces in x and y direction. The normal sensor loading is displayed in image 1. What is the effect of loading them as in image 2? And what is the effect of putting a rotational force on the end?


texts: Is cast iron better that Copper or Aluminum for cooking steaks?

texts:
Folk wisdom states that Cast Iron pan is the best for searing steak because of its high heat retention relative to the aluminum/copper counterpart.
However, this doesn't make sense in practice... because it assumes no continuous source of heat. In reality, where we continuously supply heat to the pan (and assuming perfect heat diffusion within the pan), cast iron should offer no advantages.
Especially since there's no way the heat output from the system is greater than the heat input.
"Advantage" in this context means the ability to transfer heat to the food at an even and steady rate. (the common fear is that plopping a cold steak in the pan will instantly cool down the pan and make it unable to keep cooking, or change the rate at which to food cooks)


texts: How to make sure a pipe does not take all of the water from a stream?

texts:
I am trying to design a pipe which takes water from a river and transports it to a reservoir.

However, I do not want my pipe to take all of the water from stream, because that will create all sorts of environmental problems.

How do I make sure that this does not happen?

The flow rate in the stream is $0.02 m^{3}/s$ and the stream is $1m$ wide and $1.25m$ deep.

Do I just need to make sure that the flow rate in my pipe is not greater than $0.02 m^{3}/s$?


texts: Adiabatic compression maximum temperature achievable?

texts:
The TV($\gamma$-1) = constant formula appears to be unbounded, which begs the question how high can we go?
Let's say you have a theoretical fire piston, and want to increase the adiabatic temperature as high as possible. What are the maximum temperatures achievable in such a process? How would you do it?
If we play around with some parameters of the thought experiment:

Single-use situation where the equipment is destroyed in the process
Multiple-use situation - perhaps with tungsten or a refractory cylinder?
How would you increase the temperature of the compressed gas?
How would you increase the longevity of the system? Some kind of magnetic confinement system?
What practical factors limit the maximum temperature one can reach?

Let's set aside cost for now in this thought experiment.
I guess what I'd do to increase the temperature are:

Increase the size of the energy reservoir to do the work to compress the gas. If it is chemical energy (say based on a one-off gun barrel driving the fire piston) then increase the quantity of propellant. If it is a flywheel, increase the rotational kinetic energy.

Increase the efficiency of energy transfer between the energy reservoir and the piston. For example it seems mechanically coupling a flywheel to the piston would be easier than one based on chemical batteries. But still, how though? How would you suddenly connect a flywheel spinning at thousands of RPM to a linear piston without the shock of engagement destroying the apparatus?

Have a piston with lots of inertia - so a heavy tungsten piston head which is also advantageous for its high melting point, with perhaps an osmium body. For a one off system, a material with a high vaporization energy may be preferable to one with a high melting point.

Use an inert gas that does not disassociate, such as helium, neon, argon or xenon. Would a heavy atomic mass noble gas be better?

Presumably materials can be exposed to temperatures exceeding their melting or boiling points for very short times without substantial degradation, if their thermal conductivity and mass is high relative to the thermal impulse. Is this correct and is there a way of estimating how high temperatures a tungsten cylinder can be exposed to before it degrades within one cycle?

Geometry of the piston head. The change in volume with stroke distance is linear for a cylinder in a tube. If the piston head had a taper, and the tube's end had a countersink, would this cause a sharper compression event at the end, and therefore higher temperatures?

In terms of practical factors which limit the maximum achievable temperature, I think things like the material melting points, gas disassociation or even ionization energies, reflectivity of the interior (at very high temperatures radiative heat transfer to the cylinder is also an issue), size of energy reservoir, efficiency of energy transfer to the piston, inertia of the piston would be factors.
And the last question, of course, is how would you estimate the temperature-time history of the adiabatically compressed gas?


texts: Connecting a custom 3d-printed part to an SG90 servo

texts: I've very recently got into prototyping as I'm working on a project that I intend on making as simple as possible through conventional methods, just to learn general best practices. I have an SG90 servo motor that comes with arms that snap onto the motor, but I was hoping to replace these arms with a custom 3d-printed gear. I am close to getting the part modeled in Solidworks, but I'm lost as to how to connect it to this motor. Should I include the arm and attach a gear through pins as in example 1 or should I simply model a part that connects directly to the rotating piece, as example 2? My reservations with the first one is, I don't think I can find a stable enough rod to thread those small holes. My problem with the second though is that I don't know if I can 3d print a part that exactly to fit the shape of the shaft (which I can't seem to find online). Thanks and any help is appreciated!


texts: How to increase the sensitivity range of MQ3 Alcohol sensor?

texts:
I am using an MQ3 sensor for alcohol detection but the sensing distance is short. Is there any alternative approach or solution to detect alcohol present in air from a longer distance?

For example, the drunken driver exhales ethanol vapours, the sensor placed at steering should detect the alcohol content.
But MQ3 sensors cannot detect the ethanol vapours at that distance. Is there any solution to this?


texts: Using propeller downwash for electronics cooling

texts:
I have a quadrotor aircraft (4 motors/propellers around a center housing) with some electronics in an electronics housing. Looking to cool the electronics with propeller downwash.

I have a vent on the side of the electronics housing and one on the bottom. I assume the pressure on bottom P0 is atmospheric. Trying to determine which way the air will flow.

Would pressure P1 be higher or lower than atmospheric?

The propellers do work on the fluid and increase the dynamic pressure but there is also air at high velocities flowing past the side vents. Having trouble consolidating propeller dynamics with Bernoulli's principle.


texts: Preventing condensate backup at startup with orifice (venturi) steam traps on medium pressure batch process mains?

texts:
I am working with 1" medium pressure steam mains (45 psig) for a batch process. Time between batches is usually short (to the order of minutes) but depending on the day the delay can be hours, and even longer over weekends or holidays.

We recently installed a full set of orifice (venturi) type steam traps. When we start up, the orifices can't handle the condensate load and the back up condensate is causing water hammer in some sections of the piping.

We are a little tight on budget but will look to installing additional (non-orifice) traps in the problem portions of the piping.  In the meantime, we are resorting to manually opening/closing the bypass valves to vent the initial condensate.

Is there a better way to prevent condensate backup at startup on a batch process when using orifice/venturi steam traps?


texts: Thermoelectric Technology to Harvest Energy from Internal Combustions Engines

texts:
Background:
In an automobile, only 1/3 of the potential energy in the fuel is converted into mechanical energy and significant portion of the energy is lost as heat.

There have been previous attempts to recuperate this lost energy.  In the early 1990's, Porsche developed automotive thermoelectric generators (ATEG) which didn't go past prototyping stage. Currently, Porsche Motorsports is testing a thermal energy harvesting system in their LeMans series Race car.

In addition to Porsche's research, GM is in collaboration with Future Tech, LLC. to explore the idea of using themoelectric technology to harvest energy from internal combustion engines.  Other automotive manufactures, such as BMW, are also exploring this technology.

Currently the power usage in a

Small car is approximately 150 W
Full size truck is approximately 500 W

If this technology can successfully be implemented, then components such as the radiator, water pump, and alternator could effectively have reduced workload or removed from the system, thus reducing the load to the internal combustion engine.

Question:
With the growing interest in green technology, are there technology barriers beside efficiency that are preventing the implementation of energy harvesting from internal combustion engines using thermoelectric technology?

References:

Which one must be used matched output voltage or open circuit voltage?
Benefits of Thermoelectric Technology for the Automobile
The Promise and Problems of Thermoelectric Generators
Modeling of an Automotive ThermoElectricGenerator (ATEG)
Thermoelectrics to replace car alternators and improve MPG
Thermo-Electric Generator in Turbocharged Diesel Engine
Kettering University researchers are working with General Dynamics to convert the unused heat energy of their propulsion systems to useful and clean energy
Porsche 919 Hybrid LeMans Racer Goes After The Two Thirds of Gasoline’s Energy That’s Wasted As Heat
Germans trying to replace Alternator with Thermoelectric Generators or TEGs
Porsche 919 Hybrid LMP1 Le Mans prototype...

Footnote

The suggested duplicate is related, but still distinctly different.  The order of magnitude of energy available to recover from an internal combustion engine is significantly greater than within the GPU of a video card.  As such, the economies of scale are different and different solutions are therefore possible.


texts: I need a clear material that will allow sun in but won't insulate heat. Sun sun rays get in but doesn't trap heat. Any ideas?


texts: small gearbox for experimental wind mill

texts:
The gear box will have little torque as I am only using a 12 by 18" wing which rotates. The two shafts I am using are 1/4 ", one form the wing and the other going the to pivot for the wing to circle, with lift.  I can't find 1/4" gears and I am not sure how to attach them to the two shafts so that they cause rotation in different directions.  I know only two gears of equal size are needed, but I never made a gear box before.

I hope this helps.  Thanks in advanced!


texts: Why is local yielding considered the limiting case in context of buckling in Eurocode?

texts:
In Eurocode, when use buckling curves to calculate the maximum load that a compressive member can be subjected to before it risks buckling. Buckling curves are based on the Perry-Robertson formula. I'm reading a derivation of the formula here.

The formula is derived basically like this: we assume some initial eccentricity of the column in shape of a sinusoid, and then arrive at this expression for the deflection of the column at the mid-point:

$$y(\frac{L}{2})=\frac{\sigma_E}{\sigma_E-\sigma}a$$

where $\sigma$ is the stress compressing the column, $\sigma_E$ the Euler critical load of the column and $a$ the assumed eccentricity of the column at mid-point.

Then we use an expression for the maximum stress inside the column, summing the direct compressive stress as well as the stress that occurs from the bending moment:

$$\sigma_{max}=\sigma+\frac{Mc}{Ar^2}$$

where $\sigma_{max}$ is the stress on the extreme fiber on the mid-point of the column, $M$ the moment of the column due to load, $c$ the distance from the neutral axis to the extreme fiber, $A$ the cross sectional area and $r$ the radius of gyration.

Knowing that $M = Py(\frac{L}{2})$, we get:

$$\sigma_{max}=\sigma+\sigma\frac{c}{r^2}\frac{\sigma_E}{\sigma_E-\sigma}a$$

It is then said:

  At failure the maximum stress is the yield stress, $\sigma_y$
  .

and we proceed to set $\sigma_{max}=\sigma_y$ and solve for the compressive stress $\sigma$.

This last step puzzles me. Why do we set the stress to yield stress, if we are interested specifically in designing against buckling? If we design a column in this way, then yes we can limit the compressive load so that the extreme fiber (and thus the entire column) never reaches the yield limit anywhere, but how does this prevent a failure by buckling? We know buckling is a failure occuring from sudden sideways deflection of a member. But buckling can very well occur entirely elastically. This formula seems to only ensure that the member does not yield, but does not seem to say anything about how much the member deflects.

To me, it would make more sense to take the very first equation, the deflection of the midpoint, and set some limits on that, based on the slenderness of the column. So don't we really care about how much the member bends sideways as long as it does not yield, or have I misunderstood something?


texts: Finding Tension in cable in 3D Equilibrium

texts:
In a typical 3D Equilibrium problem.

Assume you have two cables points supporting a mass. The two cables are K distance above origin and form a quadratic triangle with the mass which is a the same distance K from origin but in + y axis. A strut from origin interest the two cables at mass.

My question is. To find tension in two cables, do I need to find moment about origin or do I just need to equate the I,j and k components of the two tension forces to zero and solve then using Cramer's rule?

When do I need moment to find tension? When don't I need it?


texts: Constant current load under varying input voltage

texts:
I am building a battery discharge system for LiPo batteries which accepts a charged battery and discharges it at a CONSTANT CURRENT regardless of the battery voltage, until a threshold is reached. The threshold is the LiPo storage voltage.

The purpose of the system is to measure actual delivered power under variable battery environmental conditions.

The question I have is regarding the load itself and the feedback system required  to vary the load to meet the constant current requirement.

So what is the recommended load?   e.g. motor or heater

How could the load resistance be varied in direct proportion to the battery voltage?

Any circuit references would be valuable.

(sorry I'm an ME not an EE)


texts: What standard and/or code covers building stormwater management?

texts:
As an energy engineer focused on energy efficiency in the built environment, I am familiar with the standards and codes covering energy use in buildings; specifically ASHRAE 90.1, the "Energy Standard for Buildings," and IECC 2018, the "International Energy Conservation Code."

Recently several areas of increasing concern are intersecting with this work, such as indoor air quality, but also stormwater management:

  Stormwater management is the effort to reduce runoff of rainwater or melted snow into streets, lawns and other sites and the improvement of water quality, according to the United States Environmental Protection Agency (EPA). (Source)

My question is what engineering codes and/or standards govern stormwater management in and around buildings?

Some teams we work with are concerned about how to manage the water which falls on the roof of the buildings they are designing. Are there guidelines related to collecting and/or treating this water before diverting it?

Note: my work is within the U.S., but I'm also interested to know of standards or codes that are in use in other countries.


texts: Wind turbines with down tower power units. Why aren't they more common?

texts:
Concerning the big megawatt wind turbines, if there is such a big trouble with gearbox bearings failing much earlier than expected and costly maintanence or replacement of huge gearboxes, what is keeping people from placing the whole power unit(gearbox, generator, transformer, etc.) down on the ground, connecting the gearbox and turbine rotor with a chain-sprocket drive?

With a belt or chain ,a certain margin of flexibility would compansate for misalignment of axis and absorb shock loads. Apart form delivery time, replacement of damaged parts would take much less time and effort.

Continuously variable transmission systems are already being adapted to wind turbines so such a drive should not be an unrealistic option. Turbines with hydraulic drives are already being built with down tower power units.

I know this would have been done if it had more advantages but what is the big disadvantage here that overcomes such a saving of time and cost?


texts: Working of spider gear in differential axle wheel mechanism

texts: What causes the spider gear to spin about it's own axis while the vehicle is taking a turn?


texts: What is the most efficient means of warming a building with a high ceiling?

texts:
Consider a large auditorium, a church, or some other very large, essentially one roomed building with a high ceiling.  Suppose that the building has many entrances which enable cold air in/hot air out and traffic in and out of the building is unavoidably large.

I would imagine that any attempts to control the temperature of such a large building would be very inefficient in terms of energy and cost, particularly because warm air rises.

Assuming that it's very cold outside and we're interested primarily in keeping the building warm at the ground level so that it is comfortable for humans to work and interact,  what is the best method to keep such a large, essentially one roomed building with a high ceiling warm when outdoor cold air exposure is frequent and unavoidable?

When I say "best," I'm interested in balancing energy, maintenance, and monetary costs over the life of the building.


texts: Why don't we have parabolic ceilings with mirrors & a light at the focus?

texts:
I'm thinking of big halls, especially those that use chandeliers for light. The idea's simple: build a parabolic ceiling that uses mirrors, place the chandelier at the focus, and illuminate the entire hall with light. Since the light would be coming from the ceiling, it wouldn't be possible to "stand in someone's light" either, which would be great for e.g. exams. One would also be able to use just one light source for the entire hall. Why hasn't this been done?

I feel like I'm missing some obvious reason but I can't place it. One guess could be that big parabolic mirrors are expensive, but we have such mirrors elsewhere (e.g. for telescopes, science museums). It could be that such a hall would look really bright if one looks upwards (at the ceiling), but that could be mitigated by, e.g., placing a one-way mirror between the ceiling and ground level that allowed light down but not up. What am I missing?


texts: carbon steel corrosion in chloride solution

texts: we have a alkaline solution with Cl content of 3500 ppm, and pH=10 ,my question is if the carbon steel material is proper for this solution or not?


texts:
The figure represents a rigid bar $ BCE $ connected to two steel ties $ AB $ and $ CD $ ($ E $ = 200 GPa).
The rods are connected by joints at the ends and have a uniform cross section of 6 $ \times $ 25 mm $ ^ 2 $.
Determine the value of the largest $ P $ load that can be suspended at the $ E $ point without the vertical displacement at that point
exceed 0.25 mm.

I calculate $\delta_B$, $\delta_C$ using FL/AE and with the equilibrium equations and equilibrium moments i got $F_{AB}=1.5P$ and $F_{CD}=2.5P$
And finally using virtual work i got $P*\delta_C - F_{AB}*\delta_B - F_{CD}*\delta_C$ =0 i got P=4405Kn
is my resolution also correct? Since theres a small diference between my result and the resultions result...
In the solutions they have done

From the analysis of the deformed diagram of the $ BCE $ bar it is concluded, by the equality of triangles:
\begin{equation}
\tan\alpha = \displaystyle\frac{\delta_\mathrm{B}}{x} = \displaystyle\frac{\delta_\mathrm{C}}{l-x}
\quad\Leftrightarrow\quad
\displaystyle\frac{\delta_\mathrm{B}}{\delta_\mathrm{C}} =
\displaystyle\frac{x}{l-x}
\end{equation}
Also taking into account that the ratio of length variations  $\delta_\mathrm{B}/\delta_\mathrm{C}$ can be expressed by:
\begin{equation}
\displaystyle\frac{\delta_\mathrm{B}}{\delta_\mathrm{C}} =
\displaystyle\frac{F_\mathrm{AB}L_\mathrm{AB}/A_\mathrm{AB} E}
{F_\mathrm{CD}L_\mathrm{CD}/A_\mathrm{CD} E}
\end{equation}
since $L_\mathrm{AB}=L_\mathrm{CD}$ and $A_\mathrm{AB}=A_\mathrm{CD}$,, the previous expression is simplified to:
\begin{equation}
\displaystyle\frac{\delta_\mathrm{B}}{\delta_\mathrm{C}}
= \displaystyle\frac{F_\mathrm{AB}}{F_\mathrm{CD}}
= \displaystyle\frac{1.5 P}{2.5 P}
= 0.6
\end{equation}
result,
\begin{equation}
\frac{\delta_\mathrm{B}}{\delta_\mathrm{C}} =
\displaystyle\frac{x}{l-x} = 0.6
\quad\Leftrightarrow\quad
x = \frac{0.6}{1.6}\,l = 0.374~l  \quad\mbox{(mm)}
\end{equation}
$$x =  93.750  mm$$
Due to the similarity of the triangles comes:

$\delta_B,~x,~\delta_E ~\longrightarrow~P$ :

\begin{equation}
\tan\alpha = \displaystyle\frac{\delta_\mathrm{B}}{x} =
\displaystyle\frac{\delta_\mathrm{E}}{L-x}~,
\quad \delta_\mathrm{E} \leq 0.25~\mbox{mm}~,
\quad x =  93.75~\mbox{mm}~,
\quad \delta_\mathrm{B} = 10^{-5} P
\end{equation}
whence it results:
\begin{equation}
P \leq 25000 \frac{x}{L-x}
\end{equation}

$\delta_C,~x,~\delta_E ~\longrightarrow~P$ :

\begin{equation}
\tan\alpha = \displaystyle\frac{\delta_\mathrm{C}}{l-x} =
\displaystyle\frac{\delta_\mathrm{E}}{L-x}~,\quad \delta_\mathrm{E} \leq 0.25~\mbox{mm}~,
\quad x =  93.75~\mbox{mm}~,
\quad \delta_\mathrm{C} = 1.667e-05 P
\end{equation}
whence it results:
\begin{equation}
P \leq 15000 \frac{l-x}{L-x}
\end{equation}
$$P \le  4411.765  N$$


texts: Internal Geneva drive calulations/design

texts:
So there is a lot of information out there about designing an external Geneva drive, but I can't seem to find anything about designing an internal one. I'm trying to design something similar to this (but with a different number of positions):

I know the internal drive is based off a calculations from a triangle, and I'd assume the the internal one is too, but it's just not clicking for me. Can anyone point me in the right direction? Thanks!


texts: Why doesn't steam/water flow backwards from expansion in power plant feedwater pump/boiler?

texts:
I think i understand the mechanics in a steam locomotive:

Fill boiler with water
Close off boiler
Heat boiler until pressure is sufficient
Keep boiler hot and use steam pressure until no more water left
repeat

Boiler is heated and energy is given to water in form of heat. Water gets hot and vaporizes. Water vapor tries to use a lot more space, this expansion is used in pistons to create mechanical force. Since the boiler is closed off while in use, the water/steam pressure has nowhere to go but to the pistons. This seems clear.

Now, in power plants (all types that heat water: nuclear, coal, gas and so on) water is circulated. This means that they do not shut down the plant to refill it with water. Here's what i have trouble understanding: if you have to use X amount of energy to pump in the water to a cold boiler to keep the pressure up, you would also have the same amount on energy available to extract on the other end. But if you heat it, you add energy to the water while it is in the boiler, you increase the pressure. Logic would say you have more energy now available on the other end. But wouldn't the pressure try to press out form the pump side also? The pump would have to fight more to keep the water in and waste more energy. So i think the pressure is not increased in the boiler. How is the heat energy then extracted by the turbines? Is the water converted to steam and the speed of the steam is increased using heat while keeping the pressure the same and then the energy is extracted from the very fast speed of the flowing steam(kinetic energy essentially)? Much like a jet engine, the last compressor stage is the highest pressure point and downstream only speed is added while pressure is lowered? If so then it would seem the pump would have to maintain pressure while the steam slowly leaves via turbines. Or is there some other mechanism that eludes me.

If somebody says that turbines work by using the pressure difference then please explain where does the energy come from if the pressure is generated by the high pressure feedwater pump before the boiler. All you could extract would be what the pump puts in and boiler should increase pressure both ways making it harder for the pump to put anything in at all.

Thank you.


texts: Engine Control Unit theory regarding highest priority task?

texts:
I am changing career paths and will be working on ECUs/VCUs and associated downstream electronic control modules. I am interested to find a research starting point in terms of Real-Time-Operating-Systems as related to Automotive applications and I figured that the highest priority task in Automotive applications might be braking or fire-related. Is this assumption correct and if not, what (in modern automotive design) is considered the highest priority task to deal with?

Thanks in advance for your responses.


texts: How does this obviously fake but convincing perpetual machine work?

texts:
Apparently, during a world fair (presumably Paris in 1889[Don't trust that fact]), an engineer showed a perpetual machine that could not be stopped. For months, he challenged visitors to stop it, but that machine always recovered the energy that people tried to take from it. Everyone was convinced it worked!

The "trick" was so simple: the action of trying to stop it would give the machine extra energy.

Now, I could have heard that from a highly unreliable source, but whether the story is true or not doesn't change my question:

What would that machine look like and how exactly would it work?


texts: How to design CAD bevel gears from known outside diameter?

texts:
I'm working on a problem where I need to design and 3D print bevel gears to fit in the inside of a box and transmit a gear train around the inside corner, as roughly illustrated by the cross section image below. The box is composed of 3mm thick material and the distance from each gear axis hole to the edge of the box is 15mm. How can I design these bevel gears?

I'm a fairly competent user of Solidworks and Autodesk Fusion 360 and I've attempted using the Toolbox design libraries and plugins respectively but both generate gears based on specific parameters (which do not include the outside diameter, or pitch diameter). I'm working under the assumption that I'll need to draw them based on the outside diameter so that they fit nicely into the corner of the box - is there another way of doing this, or is there a way of designing them to these constraints?

Edit - the constraints available in Solidworks to design the gear are the following:

Module
No. of teeth
Pinion's no. of teeth
Pressure Angle
Face Width
Hub Diameter
Mounting Distance
Nominal Shaft Diameter

It's also worth noting that some of these parameters are restricted to certain values by Solidworks i.e. I can't enter any random value, only pick from a drop-down list.


texts: Looking for program and file format for CNC Milling

texts:
I am creating subwoofer boxes out of MDF or Baltic Birch.  My local makerspace has  a CNC machine.  I am going to make all of the cuts with it.

What software is generally used or will work to get a file for a CNC machine?  In the makerspace's FAQ they say DXF or STL but it's under the section regarding Laser Cutting.  So I'm not sure if that's the needed file format.


texts: Do you know any mechanism that can pass a thread through several holes?

texts:
Well i am stuck trying to figure out this problem, actulally i see a machine that can make it with a torus, a torus coilling machine. But that not work with a multi turus shape.
I want to automate something like this:


texts: Functionally Matching Gears (teeth count) in Planetary Gearbox

texts:
I wonder, whether an equation

$$R = 2P + S$$

should give a geometrically sound design, where $R$ is the tooth count for the ring; $P$, for the planets; and $S$, for the sun.

I have tried to model a planetary gears with $R = 47$, $P = 16$ and $S = 15$. They do look well as for diameters, but the teeth do not match - it cannot be assembled.

Does the equation above guarantees, that the gears will fit each other? I now tend to think, that it does not take into account assemble-ability. Or perhaps I made a mistake somewhere.

Module is 0.9. Centre circle of planets was calculated as:

$$D = \frac{m(Z_1 + Z_2)}{2} = \frac{0.9(15 + 16)}{2} = 13.95$$

I double checked everything and didn't find any mistake yet.

EDIT

The gears should be precise, I used "Involute Gears" macro in FreeCAD, which should provide a proven correct gears. The carriage is based on precise fully constrained sketch and the parts are assembled in fully constrained assembly. Thus, there should be no imprecisions here.

Where I would look for possible mistake (but didn't findany) is the position of planets against outer ring and sun (calculated as shown above), imperfections of outer ring, which is produced as subtract shape of involute gear with 47 teeth from a disk. And starting rotations of the gears for assembly.

But what I'm thinking is, if it is even that easy. The outer ring has 47 teeth, which is a prime number (and selected on purpose, because correct gears should employ prime numbers and have to care about a common divider), meaning that one third (we have 3 planets) has 15,6 teeth. And that means, that if you set the carrier sou that it points into the middle of the tooth with one of it's points, the other two will be offset from a center of a tooth by 6/10 of a tooth. While in the same time, the Sun has 15 teeth which are perfectly dividable by 3 and we can have it set with all three i.e. gaps pointing in the direction of all three carrier lines. This is confirmed by creating three lines constrained at 120° and rotating with one (other two follow), I cannot find any position at which would each line point at the same place on a tooth.

Now, I'm thinking, that this prohibits same condition for every planet. Meaning this is not possible to assemble (as is). But perhaps I'm missing something; the pointed simulator does depict same configuration assembled, but then it's only infographics which could cheat...

So issue is still open.

EDIT 2

It is also good to point out what should be possible to assemble then. Well, one configuration which should work is $S = 15$, $P = 15$ and $R = 45$, but then it is a very bad design due to $S = $P (having the worst common divisor possible). Adding 3 to 5 I get 48, which won't fit the initial equation, but adding another 3 I get $S = 15$, $P = 18$ and $R = 51$ which doesn't seem to be that bad. The greatest common divisor of a Sun and Planet is 3, meaning sun will turn 5 times before the same tooth will meet same tooth on the other gear.


texts: How does this screw height adjustment mechanism work?

texts:
I've been puzzling over this for some time. In this picture, there are two steel frames, with four height-adjust screws controlling the height between them. The roller shown is applying a good amount of pressure (maybe analogous to someone rolling dough with a rolling pin). It appears that there is one screw going into a green "nut" fixed to the top frame and passing through to a sort of collar fixed (but allowed to rotate?) to the bottom frame.

My thinking is that the screw functions as a sort of lead-screw, rotating to bring the top frame up and down, while remaining fixed on the bottom frame. Of course, it also has to rotate.

The thing is, with the upward pressure, the green collar in the bottom frame would be pulled out, unless it snaps in on both sides. As well, there isn't anything visibly stopping the top frame's green collar/nut when upward pressure is applied on the roller (and thus the frame).

Unfortunately, no other information than this image of the fixture is given, and the images are evidently not great quality.

What mechanism could be used here to adjust the height? What methods are commonly used for precise height adjustment of platforms like this?


texts: Which is Worse: Car vs. Car or Car vs. Wall?

texts:
So I got myself questioning what could be worse for the driver... a collision of two identical cars at equal speed (frontal crash) or the same car with the same speed crashing through a wall? The first case I see it would double the impact, but also it will absorb the energy into the other car structure, otherwise, in a solid and rigid wall, all the energy would come back to the vehicle.

Which situation is worse for the passengers?


texts: A material to insulate a container so that water inside the container is not affected by microwaves?

texts: I'm running an experiment and I need to have a container filled with water. The container will be placed inside a microwave oven, but I need to minimize any effect the microwaves will have on the water. How can I go about running my experiment? I'm thinking I need to insulate the container with some kind of material that will shield the water inside from the microwaves generated by the microwave oven.


texts: What are the pros and cons of a traffic circle versus a traffic light intersection?

texts:
The debate of traffic circles (also called roundabouts or rotaries) versus traffic light intersections has been in progress for a while. Those in favor of traffic circles say that, among other things, that they are safer than traffic light intersections. This claim has been scientifically proven. On the other hand, traffic light intersections are more space-inefficient.

Even Mythbusters has joined the fun, testing the efficiency (which is one of the main arguments both sides seem to concern themselves with) of each method.

For comparison, here's a quick picture of a traffic circle:

And of a four-way traffic light intersection:

So, what are the pros and cons of a traffic circle versus a traffic light intersection?


texts: Purification of wet-process phosphoric acid

texts: I'm doing my senior design class and I have design a chemical plant that produces phosphoric acid by reacting phosphate rock with sulfuric acid. The phosphate rock has a lot of impurities, some of which I know how to separate but there are some impurities that I'm completely lost about. The impurities are: $\text{Al}_2\text{O}_3$, $\text{Fe}_2\text{O}_3$, $\text{MgO}$, $\text{Na}_2\text{O}$, $\text{K}_2\text{O}$. How would these react in a mixture of water, sulfuric acid and phosphoric acid and how would I purify them out of my crude phosphoric acid? Or at least, what's a reasonable assumption to make to make my plant design a little straightforward.


texts: What is the strongest way to fasten 8020 extrusions in this arrangement?

texts: I am making a project using 10mm aluminum extrusions. I am trying to connect all three extrusions like the picture below shows and I am going to make my own bracket (in red) out of aluminum since the variety of choices is very scarce for this 10mm size, but I will include a picture of something similar so you can get an idea of what I'm making. I am wondering which arrangement is stronger and more rigid- the left one, or right one? Or is there an even better way to do it?


texts: Working out RPM from car engine's lb ft?

texts:
Using an old copy of an automobile magazine, these are the cars with hp and lb ft I am trying to work out the RPM for:

2007 Honda Accord 2.4 sedan, 2.4-liter 187hp 4-cylinder, 164 lb ft pulling power

The math I did to work out RPM:

187 x 5252/164 = 5,988.56 (rounded up to 6000rpm, how far should i round up in significant figures or decimal places)?

2007 Peugeot 207 1.6 HDi 110 GT, 1.6-liter 110hp 4-cylinder, 177 lb ft pulling power

The math:

110 x 5252/177 = 3,263.95 (rounded up to 3,264 rpm, or should it be 3000 rpm?)

I used these formulas:

Torque and horsepower relations:
T = HP * 5252 / RPM

HP = T * RPM / 5252

RPM = HP * 5252 / T

In my two examples, have I got the math correct for car engines? With RPM, when do I need to round up correctly and what significant figure level do I need?


texts: Do submarines really have cranks for closing leaks?

texts:
It's common in submarine movies that when suffering some kind of shock (like a near miss by a torpedo or falling deep into a trench), water will start bursting into the cabin and the crew will run around turning little wheels or cranks to stop the leaks.

Is this realistic? What are those wheels doing? Is it even plausible for a submarine to leak without a catastrophic failure?


texts: An example is this pressure transmitter which has a BSL accuracy of 0.08%. I know the term "Best fit straight line" - BFSL. Is BSL just a short hand for this ("Best straight line")?


texts: What is the effect of end diaphragms on prestressed girder forces/deflections?

texts:
I'm encasing the abutment ends of prestressed concrete bridge girders in concrete before the deck pour. (For lateral stability and to prevent the soil from spilling through.)

Discussion of intermediate diaphragms for prestressed girders abounds, but I haven't found information on structural behavior of end diaphragms.

For purposes of a consulting engineer

My gut / engineering judgment is telling me the effect is negligible, but I prefer to understand what's actually going on before making simplifying assumptions.

Conceptually (versus a girder without the diaphragms):

Does this change deflections during the deck pour? What about long-term deflections?
Does this change the live load moments &/or shears?
Is there any logic by which the encased length should be a function of girder depth or span length?

I've put a sketch below since terminology and typical bridge configurations vary around the world.


texts:
I am currently integrating a C-Code (written by a third person) in a Simulink model. In the C-Code various sensor signals are filtered, using a PT1 filter with the following equation:

$$y(t) = \dfrac{u(t) + Cy(t-1)}{C + 1}$$

Where $y(t)$, $u(t)$ and $C$ are the output (the filtered signal), input and a factor applied for each signal individually, respectively.

Looking at the step function response, I can see a typical PT1-behaviour with a gain factor of 1.

I cannot figure out the derivation of this function from the general formulation (the differential equation) of a PT1, which is:

$$Ty'(t) + y(t) = Ku(t)$$

Can any of you guys help me out?


texts: Can a Peltier's device (i.e.Thermoelectric cooler) achieve cryogenic temperature efficiently?

texts:
Does the stacking of peltiers device shows promising results in achieving the cryogenic temperature? I have tried doing the experiment, the overall temperature of the system increased around 80ºC and then the dissipation of that heat was the prime issue? Heatsinks usually fail to dissipate this high amount of heat.
Is there any alternative technology to achieve cryogenic temperature electrothermally without producing much amount of heat?
Can any modifications in stacking help?


texts: Soapbox - GoKart material - Bamboo or steel?

texts:
I am building a soapbox (go kart) and I am planing on what materials I could use for the frame and the chassis. I have thought about using bamboo or steel.

Steel is normally the go to material when building the chassis and frame. However, I am starting to think bamboo may be a better choice. My reasoning is that:

Bamboo is less dense than steel, this makes the structure lighter and could enable it to go faster.
It is cheaper than steel. This leaves room for prototyping and allows me to iterate my way to perfection.
More flexible than steel this could be good as the go kart will jump over bumps and slides.
No welding would be needed.
Depending on the type of steel used, bamboo can have a higher tensile strength than steel.
More eco-friendly.

Also, it is possible to make a bamboo composite that produces a stronger bamboo based material.

Could you let me know your thoughts on what I should use: steel, bamboo or something else?


texts: How to heat up a swimming pool with the sun

texts:
I'm trying to figure out how to heat my pool most efficiently using the sun.
Currently, I've got 2 black panels (made up of a bunch of black pipes) on the roof that the pool pump cycles the water through as part of the normal cycle through the pool filter. That pump uses 0.75kw of power just to pump the water to the roof which seems extremely inefficient if it's for heating water.
So I went and bought a very small pump that pumps the water up to the roof and then through a couple of black pipes before pumping it down.
A couple of questions:

The water is cold(by feel right now) when it comes back out with both methods. Would it help if I stop the water with the small pump, wait for it to heat up a bit and cycle? I don't know enough about thermal conductivity to know if heat is transferred more efficiently when water is moving vs standing still as well as the temp of water relative to the plastic pipe being heated by the sun. Edit: ok, I see that the higher the difference in temp, the faster heat flow happens. Still don't understand the part of it being heating up for bot a long time before going back into pool.
Assuming I can repurpose the energy used for the pump (from my solar panels) would it make sense to just rather use a 600w heating element and cycle the water through a geyser / container with an element (don't want element in pool for safety)?
Anything else that's more efficient?

To add, I've got a thick pvc tarp over it (for kids) and I assume because of the air gap between tarp and water most of the heat is not transferred effectively.
The pool is around 15000 liters and ~2.5*5m (not sure of depth).


texts: How to calculate the right motor size & type for a soil sifter?

texts:
How would one calculate the proper size of an electric motor to properly drive a soil sifter?

Assumptions:
Screen:  flat, 18"x24", 1/4" to 3/4" wire cloth (interchangeable screens), total weight (including frame) = 4 lbs
Shake Info: total screen movement/shake = 6", shake rate = 132 shakes per minute
Load:  15 lbs soil or gravel mix
Other: Belt driven

Note:  I'd hate to use a 3/4 hp motor when all I might need is a 1/50 hp motor.


texts: I'm stucked at trying to find the vertical reaction at top and bottom constraint, i know how to do the rest. Can you show me how?


texts: Solidworks: Why is the Projected Curve position different from the preview?

texts:
Preview:

Projected curve:
If anybody has any ideas that would be great. Also, the issue is not only a 'visual' issue, but also a functional issue. I am attempting to use the projected curve in a swept cut, but I get errors. Thanks!


texts: How to prevent a cable going off a caster wheel pulley?

texts: When pulling a cable to the sides at large angles it has a tendency to come off a caster wheel pulley, how could you prevent it from sliding off the pulley?


texts: Setup for Testing Custom Ethernet Cabling with Network Switch

texts:
I am building a setup for performing a bandwidth test on custom cabling that carries two gigabit Ethernet channels. I have a working setup that includes two computers and two network switches to which the custom Ethernet cabling connects (see wiring diagram).
While not apparent in the wiring diagram, the network switches are included in the setup so that the fixture can accommodate several cabling configurations.  Each cabling configuration includes two Ethernet channels (ETH0 and ETH1) and both channels are tested simultaneously. Only one cabling configuration is tested at a time - therefore four ETH0 and four ETH1 ports are used during a test.

Is there any way to make this setup work with one network switch?  The aim is to configure the switch so that traffic between Computers 1 and 2 travels on the custom cabling under test.  I must prevent traffic from simply travelling between the switch ports to which the Computer Ethernet interfaces connect (as this would bypass the custom cabling under test).
Many thanks.


texts:
My problem:
I'm trying to model fatigue disbond growth in Abaqus. So far I've tried this using multiple approaches with mixed results.
What I've tried:
I first started with modelling a static general step. I've tried:

Interaction with fracture properties, I was not able to propegate a crack:

both with and without a "debonding with vcct" crack under interactions-> specials-> crack
both with and without material defined with traction seperation damage

Interaction with cohesive behaviour with damage, I was able to propegate a crack:
X-fem with material defined with traction seperation damage, I was able to propegate a crack:

both using no contact property and a vcct fracture property

I was initially hoping to use the debond using vcct because it seems like the thing to use for my case but I've set that aside for the time being.
I then moved on to modelling fatigue using a direct cyclic step. It's not something I've used before so I might have done this incorrectly. I've tried to figure it out using tutorials as well as reading the documentation but I'm not sure it's correct. The settings I used are:

cycle time period: 1 (standard setting)
incrementation: both automatic and fixed
increment size: ranging from 1 to 0.05, I've figured out that this is the step size one cycle is modelled in, but I'm not sure how the accuracy of this relates to the fatigue modelling
maximum number of iterations: 5 (instead of 200 in order to save computational time)
number of fourier terms: have not touched this
max allowable temperature change per increment: 1 to 1e-5 I think this is used to choose the optimum step size, not sure what a reasonable number is
fatigue: I include low level cycle fatigue analysis
cycle increment size: anything from 10 to 1000
maximum number of cycles: anywhere from 1000 to 100000
damage extrapolation tolerance: 1 I have no idea what this does so I haven't touched it

I've created an amplitude with:

frequency 6.28 (loading and unloading once per cycle)
starting time 0
initial amplitude 0.5
A 0
B 0.5 (combined with the intial amplitude this should mean the loading is from 0 to 1 I think)

Unfortunately I have not been able to get the cohesive interaction to disbond under fatigue loading. I think I might be supposed to change some of the keywords, but I've not been able to change them successfully.
The x-fem approach did work with the fatigue loading. However, I originally did this using a velocity constraint. When I switched to loading or a displacement constraint the crack did not propegate, even with loads significantly higher than the case with the velocity constraint.
Where I'm currently at:
I've got a model that sometimes cracks when using a direct cyclic step using X-fem with a vcct interaction. I'm very confused and don't know what I could try next.
My question:
How can I fix my model such that I can model disbonding under fatigue loading? I understand helping like this might not be easy so any resources that you could point me towards would be very much appreciated.


texts:
I have 2 plates that are fillet welded to each other. How can I determinate the max force the weld can take before it cracks?

The plates are only welded on one side because the other side is not reachable.

I added a image to clarify.


texts: Is shock spectrum always obtained for an undamped single degree of freedom system?

texts:
I am reading a textbook on fundamentals of vibrations and it has a very brief introduction to shock spectra. It mentions that

  For comparison purposes, it is customary to use the response of an
  undamped single degree of freedom system to obtain the shock spectrum.

So is it that we always find the maximum response of an undamped single DOF system to get the shock spectrum? If yes, then how does it help us, because can't the response of the structure which I am analysing (say a building) be widly different from that of a single DOF system? For example, consider two shocks. The shock which seems "stronger" (higher maximum response in general) when using a single DOF system may actually be weaker when using my structure.

Also, just saying an undamped single DOF system seems vague because response to the same shock may differ for different single DOF systems. Is there a specific single DOF system that is used here (like the mass-spring system)?


texts: What is the rated tensile strength of 2000 kcmil stranded copper conductor?

texts:
All the documentations I could find goes upto only 1000 kcmil. Please direct to a reference for larger cables.

Is there a method to extrapolate from smaller cable sizes?


texts: Can a magnetic lock be negated or overcome by a stronger electromagnet?

texts:
Magnetic locks seem to be fairly common on the doors of modern buildings, but I question their reliability when compared to a traditional, mechanical lock. I realize that the strength that it would take to actually pry a door away from a good electromagnetic lock would certainly be enough to damage the door or frame, just as it would be with a mechanical lock.

If you had an electromagnet strong enough, however, wouldn't it be possible to negate a magnetic lock by fastening your oppositely-polarized electromagnet on the outside of the door opposite the magnet on the inside so that, when activated, the outer magnet would overpower the attraction between the inner magnet and the magnetic material on the door, effectively opening the locked door?

If so, I feel this would be a pretty big disadvantage when compared to a traditional mechanical lock. Not that a powerful and portable electromagnet is necessarily a readily available and affordable thing, but...

Ignoring the practicality of actually owning and operating such a powerful electromagnet, is this even a plausible thing to do?


texts: Problem with cantilever beam and yield strength

texts:
Hey, I make a project in which I use a cantilever beam with distributed equal load across the whole beam and I'm using the formulas above to calculate the displacement, moment...

My specifications for the beam are:
4.5m long aluminum 2024 beam, 4x3 cm walls (the force is applied on the 4cm side), 2mm thickness. and a young's modulus of 70 GPa. a force of 40 N/m is applied

from my calculations the moment of inertia is 37 mm^4, meaning the maximum displacement should be 0.6m at X=4.5 and the maximum moment is 400 N-m at X=0.

When I put the results in the formula for bending stress, the maximum bending stress is 162 MPa, while the yield stress for this type of aluminum is around 300 MPa.

something here doesn't seems right for me. the beam is bent 0.6m but does not exceed the yield point, maybe I did a mistake somewhere?


texts: Evaluating Steady State Error Constant for a Discrete Time Control System with Kronecker Delta Input

texts:
Hello there, hope you are doing well.
I am working on a Discrete Time Control Systems homework and at a certain part of it, the question asks me to find the steady state error of the system. I calculated the transfer function and found the discrete time representation of the system as well (checked in on MATLAB and everything seems correct).
However I did not find any information about how can I calculate the Steady State Error - Constant when the input is Kronecker Delta. I predict that I need to use Final Value Theorem and multiply the transfer function by something while taking the limit. I do not know what is that constant. Can you help me with that?


texts: What are some cost-effective metal substances that can wet glass?

texts:
A highly desirable property of metals like gallium and indium is that they are able to wet glass.

Normally, as metals, they wouldn't be able to form an airtight seal when in contact with glass.  But they are able to do so, and they can be used in applications where an airtight seal is required (e.g. vacuum gaskets).

That said, indium and gallium are somewhat expensive (at press time, around 700 USD/kg and 250 USD/kg, respectively).  Industrial compounds that also have similar properties, such as Galinstan (even though the glass still needs a wetting with gallium oxide first), aren't much better.

What are some metal substances that are both cost-effective and able to wet glass with an airtight seal that can be used in industrial applications?


texts: How to calculate flow rate of viscous fluids through a funnel-shaped needle?

texts:
How would you determine the flow rate of a liquid that flows through a narrow microneedle channel and then through the opening of a funnel, i.e. pouring liquid through the other end of a funnel?

I've chosen arbitrary diameters but the pressures are from literature.
The diameter of the lumen/tip is 50 $\mu$m and the base diameter is 1 mm. The pressure at the tip is 25 mmHg and the other end is open to the air.

I've tried to split the problem into two parts: first determine the flow rate through the straight part of the needle, and then determine the flow rate through the funnel. I calculated the flow rate in the first part using Poiseville's equation but I think that there must be another model for narrow channels or fluids with capillary action coupled with initial pressure. The Reynold's number is clearly in the turbulent range for the first part and I'm not sure if the numbers should be this high for narrow channels.

Is there a fluid model that's better suited for microneedles?


texts: What type of grit separator can be installed between the inlet works and bar screen of a wastewater treatment plant?

texts:
An existing sewer treatment plant is experiencing maintenance issues with their first stage (bar screens) where grit which is just barely larger than the apperture (bar spacing) of the bar screens gets jammed in between the bars.

I have been tasked to solve the problem. It was suggested to install a grit separator upstream from the bar screens. The conventional approach is to provide  grit separation downstream however.

I could not find a solution in my normal literature (Metcalf & Eddy & MWH) and google, so am asking the question here.

If grit separation can be done upstream, what type would be used? I assume that it would probably employ a vortex type system.


texts: How do I calculate the density of seawater at different temperatures?

texts: I need to know the difference in seawater density at 28 and 98 degrees Fahrenheit for control system synthesis. How can I calculate the density for a given temperature?


texts: Finding Drag coefficient for flows with both Laminar and Turbulent part

texts: How will we find the overall drag coefficient for a steady flow which is laminar initially and then becomes turbulent after a critical distance?


texts: Why don't towers use buoyancy to reduce weight?

texts:
Instead of using steel and concrete to build towers why not use mostly light weight, high tensile materials and then suspend the four corners from four giant helium balloons?

The four main cables would be anchored to the ground at the bottom, and held apart at the top by the force of the balloons pushing off each other, as they are pulled inward by the tension required to suspend each floor. So the four corner cables would essentially form a parabola, like the top cables of a suspension bridge, except vertically.

Could a skyscraper be constructed in this way?

How big would the balloons need to be to suspend the building?


texts: Is Engineering card issued by Feani recognized in USA?

texts: I am holder of Engineering card, now I moving to USA and would like to avoid at least hustle about translating all diplomas and deal with transcripts. Engineering card issued by Feani have Bachelor/Master studies listed on it, is it enough for USA, Texas to be more precise?  As i understand I can't avoid EIT and PE test even if I am registered engineer in my country but avoiding transcripts would be nice start.


texts: How to calculate the failure rate of a machine with probability and mean failure time?

texts: I dont know how to approach this problem. Suppose that a machine has a probability of failure of 43% at 90 hours of operation. How can you calculate the failure rate and the probability of surviving x hours without having failures?


texts: What are some concepts I can look into to aide in creating a 'compression funnel'(?) without the aide of a motor?

texts:
In short I'm designing a 'Humane fly swatter' for my University application into bachelor of Industrial Design.

The idea is to utilise the energy of swatting a fly to capture air through an intake, compress it and ejecting it at a higher velocity in turn drawing more air through the intake creating a slight vacuum, enough to draw the fly into a holding container.

To reiterate I'm not looking to create a big suction from the intake itself. Think of the swatter more as a butterfly net. You are capturing the fly into the funnel and from within the funnel the air velocity would have increased enough to suck the fly the remainder of the way into the holding container.

Simple visualisation of air being compressed and ejected through a formed funnel.

So I'm wondering if anyone could at the bare minimum provide me with some keywords and concepts that I can use to help me research ways of achieving this and to use this information to inform my concept designs. My biggest issues isn't understanding the concepts but not having to vocabulary to be able to search for what I need.

Thanks


texts: Energy Wasted in Electromagnetic Motor Actuator Vs Human Muscle Actuation

texts:
I would like to know if the energy utilized by a robotic arm is greater compared to the energy utilized by human arm. Robotic arm is essentially servo motors that use electromagnetic field to create motion while human muscles use muscle fiber compression/elongation and to activate motion. So is there any comparison study that points out the efficiency for both?
It does appear that human muscles uses far less energy as the amount of cooling required for human to move say 1km is not significant (body temperature rarely reaches 38 deg C, while motors do tend to heat up to 40 deg C for mild load. Now this is probably oversimplification hence I would like to know if there is some analysis that concludes or indicates the efficiency of the human muscle vs motor for same or similar actuation?

Based on the comments, I would like to know if there is a comparison for both based on unit energy, keeping the mass of both the actuators same.


texts:
I am working with a public dataset (mentioned in few papers) of vibration measurements of broken and healthy gearbox under various load. Most of the measured channels posses the same parameters no matter whether the gearbox is broken or not - almost same FFT, same histogram of the raw data, same cepstrum, same IMF (obtained by EMD).
However one channel carry a significant difference in vibrations from the broken and the healthy gearbox (see picture). I checked some papers and books about this topic (fault detection in gearboxes, FFT analysis of gearboxes etc.), but they seems to represent way to nice and clean results far from the dataset observations I have. So I am still quite unable to understand why the FFTs looks different in this way. Few notes about the dataset:

frequency of measurement / or speed and size of gears are unknown (I guess something for the FFT x axis - it has no real meaning)
the broken gearbox suppose to suffer with a "broken tooth"

My question:
Can you form any hypothesis, why the frequency spectrum is changed in the way displayed in Figure in relation to "broken tooth" fault?


texts: Short sample in a 4-point bending test ( ASTM C 393 )

texts:
I would load a sample measuring 130 mm long in the 4-point bending test (ASTM C393)

According to the standard, the sample should be 150 mm long.

Top layers consist of laminates (laminates are Fiber-reinforced composite )

Can I do the test on the 130 mm sample?


texts: can someone tell me please the name of it or any info about it


texts:
I have a question that I had asked in the stack physics section and they told me that I should ask my question here.

So I am basically starting to work on an RC submarine, and I want to use a 200ml syringe as a ballast tank. My plan was to pull the syringe handle back with a gear system, that's being rotated by a small DC motor.

My question is: how can I calculate, how much force(Newtons) does the motor need to pull the handle back and suck water into that syringe?

After finding how much force it needs to pull, how can I calculate the minimal electrical power it needs to use in order for it to operate?


texts: How to draw orthogonal lines between two points in AutoCad which will be redrawn automatically if the points are shifted?

texts:
I was wondering how to do the following in AutoCAD:
Suppose we have two snap-points, say one at 0,0 and other at 100,50. I want to draw a line (or a polyline) between these two points such that (a) the legs are parallel to the axes (i.e. one leg of the line is between 0,0 and 100,0 and other between 100,0 to 100,50), and (b) if I drag the 100,50 to some other location then the line should get redrawn automatically while maintaining its legs orthogonal.
I have seen this happen in softwares built on top of AutoCAD (usually for P&ID drawing like CADWorkx), but never been able to do it in bare bones autocad.
Thanks!
Abhishek


texts:
Recently I've begun thinking about experimenting with the construction of a Tesla turbine for steam use. The key issue I can find is that most of the examples out there of such turbines use either optical discs or HDD disks to make the actual rotors. In the case of HDD disks, these work well because they're fairly stiff, but the use limits the size of the turbine to well, the size of the largest common HDD platter (3.5") - that is, unless someone can find me a link to the obsolete 8" platter size. This obviously installs an upper practical boundary on the power level of such a turbine.

One of the key issues against Tesla turbine development historically was the inability to develop both thin and stiffened rotors; while building it thick solves the stiffness issue, it drops overall efficiency.

So, I'm taking the time to actually learn some more about engineering - how is "stiffness" quantified in engineering, and what affects it (other than thickness)? What materials would be good candidates for something such as a Tesla turbine rotor?


texts: Transforming a Wireless Computer Mouse into a Wireless Switch

texts:
With no computer involved whatsoever, I want to be able to read oscillator outputs from my wireless mouse and switch an LED on a left click AND off on a right click. I have taken my mouse apart to try and understand the parts but overall I am stuck on how to approach transforming my usb receiver for this.
How would I go about using the USB receiver and interpreting it’s outputs.


texts: What can a licensed Mechanical Engineer do in the civil/structural field?

texts:
When I was younger, I had interned in a civil/structural engineering firm specializing in bridges that had many PE civil engineers on staff and a couple licensed mechanical engineers.

Now as a soon-to-be licensed mechanical engineer, interested in starting his own business, I'm wondering what is limit of a mechanical PE. Can a mechanical PE subcontract from a civil firm? Can the mechanical PE only work on certain tasks/items of a civil project? Of the little I remember, the mechanical engineers were the experts on moving bridges (bascule, swing). My specialty is finite element analysis.

I'd be curious if anybody knows where exactly this line is, and even better, if they can point to laws/regulations/policy documents that describe this. For specifics, I am located in California, but would be interested in all United States-based answers.


texts: angle of twist of gear relative to another gear

texts:
why the torque is negative in this case ? the question ask for determine the angle of twist of gear C with respect to B .

We have to 'fix' the B , and determine the twist of C ? So , imagine that we cut off the shaft and gear , now only left with gear B and gear C connected by a shaft . So , when B is fixed , the gear C rotate , with the direction of torques pointing to the left ( by using right hand grip rule )  ,
So , the finger point towards B  , so it's negative ?


texts:
I'm trying to make most of an engine from scratch (cylinder, crank case, piston). I've been reading about pistons and I've learned that many modern pistons are cam ground--slightly elliptical in shape (reference article). As I currently understand it, the reason for this is so that when the piston heats up to the operating temperature, it forms a more precise circular shape.

I only have access to a metal lathe and that got me thinking, is it possible to design pistons so that they can be machined circularly and they expand evenly? It seems that it would save on manufacturing costs; then again, why aren't modern pistons designed so they don't have to be cam ground and that they expand uniformly?


texts: Terminology for setting Set Points to avoid "Contact Bounce"-like characteristics

texts:
What is the terminology for having different/spaced-out on and off set points for a particular controlled process?

When a system does not have the set points set appropriately, it could exhibit something like contact bounce.
This is not limited to any particular kind of system. It can be for a electro-mechanical system with physical contacts and switches, or it can be for a software system. "Debouncing" can be done in a variety of ways, such as physical distances, time delays, introducing some kind of hysteresis behavior, etc.

E.g.

A thermostat controls the AC in a house. It is set to turn on at 90 degrees and turn off at 70 degrees. When the thermostat reads 90 degrees, it turns the AC on, and when the thermostat reads 70 degrees, it turns the AC off.

Bad Examples

If this system did not have the correct set points, it would exhibit something akin to contact bounce:

If the thermostat is set to switch on/off at 80 degrees, when the thermostat reads 80 degrees, it turns the AC on, but could bounce back and forth between on and off while the temperature varies slightly from 79-81 degrees.
Similarly, if the thermostat is set to switch on at 80 degrees and off at 79 degrees, when the thermostat reads 80 degrees, it will turn the AC on, and as the AC cools the temperature down from 80 to 79, it will turn the AC off. This will occur relatively rapidly but not as rapidly as the example given above.


texts: Relation between residual stress and von mises stress calculated by FEA in comercial software

texts:
Suppose we do nonlinear structure mechanics computation.

In each time step, we can get the results and can get Von Mises Stress at each node of the mesh. Can we say this number also means its residual stress?

If not, is there any way to get residual stress?

Thank you very much.


texts: Is using your mouth and lungs to blow away dust inside your computer somehow bad for the computer?

texts:
Bottles of compressed air are very expensive where I live. While it would be nice and ideal to have and do a "proper" cleaning, I've always used my mouth and lungs to blow air onto the dust so that it twirls around and gets all over the place, just as what happens with compressed air.
Is this bad in any way? Does my breath/air contain something that's bad for the computer somehow? I realize that my method is not sustainable in a professional setting when you are undusting 500 computers in a day, but this is one single computer. My computer.
Is there any reason that I need to buy the expensive cans of compressed air? (And also have to fetch them, besides the pure cost.)


texts: So I'm trying to get to the condition as shown in the picture below, where it says that if we have zero free length springs and k1r2=k2r1, then any configuration (pose) of the link is in equilibrium. So this means I need to construct the potential energy of this system and show that for the potential energy to be constant, I need to satisfy the condition below. So far no luck. Here the springs are assumed to have 0 natural length (as said in the text). Anyone could help me?


texts: Liquid Rocket Plumbing and Instrumentation Diagram: Standards and Presentation

texts:
I'm working on a team to build a liquid sounding rocket as a school project.  We need to present our plumbing and instrumentation diagram, but we are butting heads on what program and standards we should utilize to make the PID more readable.

Is there any strategies we can use to improve readability and represent different 'flow states' that the plumbing system can provide?  Are there any good examples of P&ID diagrams that we should reference for rocketry specifically?  Is there an industry standard tool we can buy for relativity cheap?


texts: Is there a way to use a radioactive elements (Americium in my case, but for demo, any radioactive material) to create a usable amount of energy (Power small LED?) AT HOME! Using materials that can be bought from eBay/amazon and the store?


texts:
Given:

My thermodynamics text reads as follows:

In SI units, the force unit is the newton ($N$), and it is defined as the force required to accelerate a mass of $1\cdot kg$ at a rate of $1\cdot\frac{m}{s^2}$. In the English system, the force unit is the pound-force ($lbf$) and is defined as the force required to accelerate a mass of $32.174\cdot lbm$ (1 slug) at a rate of $1\cdot\frac{ft}{s^2}$. That is...

$$1\cdot N =  1\cdot kg\times1\cdot\frac{m}{s^2}$$

$$1\cdot lbf =  32.174\cdot lbm\cdot\times1\cdot\frac{ft}{s^2}$$

Question:

For all practical purposes, such as at STP conditions or close to it like when we have a rounded off sea-level acceleration due to gravity of $32.2\frac{ft}{s^2}$ $(101\cdot kPa)$, can I just think of the $lbf$ in the following way...

$$W=1\cdot lbf=1\cdot lbm \times 32.174\cdot\frac{ft}{s^2}$$

and that for the weight of an object having a mass of $1\cdot kg$ (also at sea-level) in SI units as...

$$W=9.81\cdot N=1\cdot kg\times9.81\cdot\frac{m}{s^2}$$

Yes or no and why?


texts: Why do these memory spaces start at F8000 instead of F0000?

texts:
So above I have a memory design including a 74LS138 3-to-8 multiplexer which enables 8 memory banks comprised of 2732s which are 4Kx8 in size.

My question is why the memory addressing starts F8000 instead of F0000?


texts:
I am a photo technician working in photographic labs to repair printing machines.

I am trying to better understand how these machines operate.

Blue laser gun

Laser gun type = 473 $nm$ blue dpss.
On label = maximum output 50 $mW$, 473 $nm$, type 3b laser.
Actual output power according to the manufacturer specification = 102 $\mu W$.
Now when I read with the power meter = 40.6 $\mu W$.

Green laser gun

laser gun type = 532 $nm$ blue dpss.
on label = maximum output 100 $mW$, 532 $nm$, type 3b laser.
actual output power according to the manufacturer specification = 706 $\mu W$.
now when I read with the power meter = 279 $\mu W$.

My questions are:

If a 473 $nm$ dpss module outputs power at the exit window at 102 $\mu W$, what is the power of diode?

If a 532 $nm$ dpss module outputs power at the exit window at 705 $\mu W$, what is the power of diode? You can say approximately, according to your experience, just a starting point to start replacing experiment of laser diodes.

In this dpss laser modules the pump laser diode portion and the frequency doubling crystal portion are separated by a chamber. There is c-mount and to five 9mm laser diodes are used. I know how to replace / align a diode inside the gun.

Now I want to replace the original diodes with the new one for the both modules due to week output. Suppliers discontinue this product and they are not supporting it any more. My question is what is the output power of the diode in side the laser guns? Approximately what is the diode power to start replacing diode?


texts: How to calculate the volume of air required to keep electrical box cool?

texts:
I have a steel electrical box that is 15 cm x 15 cm x 10 cm. The weight of the box is 1kg. Inside the box is a relay that loses 30 Watts of heat while in operation (it's attached to a heat sink that limits the temperature rise to 2 $^\circ$C/W, though I don't think that matters).

I'm trying to figure out the required volume of air surrounding the box in order to keep the temperature rise outside the box less than 10 degrees C (assume air temperature to start is 25 $^\circ$C).

How would I go about calculating this? I thought about using specific heat equation but I can't figure it out.


texts: Same E for axial and rotational stiffness?

texts:
When we solve frames, we assume that the materials are infinitely rigid in axial direction, so all deformations are due to bending. So this means, we assume infinitely rigid modulus of elasticity, E, from formula:
$$ \text{axial deformation} = \frac{\text{force} \cdot \text{length}}{ \text{Area} \cdot E}$$
And for bending the stiffness is EI. Is this E not the same E as the one in the formula above? And if so, if we assumed that E to be infinity for axial, then the EI will also be infinity. Or we can take E as differently for axial and rotation, so there is the axial E and rotational E?


texts: How are planetary gearboxes held together?

texts:
I see that the housings of most planetary gearboxes consist of 3 parts: a front cap, a ring gear and a rear cap. Here's a common design:

In designs similar to this, the rear cap and the ring gear are held together by several (torx) screws. But how about the front cap and the ring gear? There's no sign of any screw or fastener. There is a circlip on the shaft, but I believe that's for holding the bearings in and not for holding the front cap. Does anyone know how the front cap is held fixed? Here's a video: https://www.youtube.com/watch?v=cMr9ciatm2s


texts: How to stop the leakage from the design?

texts:
I have the design attached. it is like a water cap design. I want to rotate the lid clockwise to seal the circle container. However, I noticed that when I shake the container, water leaks. Note, the lid rotates from the inside of the container, unlike most water bottles.
How can I guarantee sealing it with no leakage? should make the lid rotate from the outside? or is there a quick fix to my design?


texts: How borewell pump works? does water stays in pipe after stop?

texts: I have 6 inch borewell of 1200 feet (domestic use). With camera test, we could see water storage is at 960 feet. i.e approx storage of 200 feet. i.e around 1000 liters. my question is, can we put motor? will it work? What happens if we pump and water is just enough for pipe above? after we stop motor, will it discharge water back or will it hold in pipe and next pumping will push out?


texts: How to analyse periodic data obtained from a vibration experiment?

texts:
I have data from a vibration experiment on a structure. This data was obtained by attaching an accelerometer to a FFT analyser, which records the data at a high sampling rate (typically in kHz range) and can also perform real-time FFT of the recorded data.

The image above shows the recorded signal below and the FFT above. The FFT shows all the dominant frequencies in the original signals.

What more patterns/ important data points can I discern from this data, that might have utility ?

For example, one being, the RMS value of the signal. What else ?

Also, the recorded data here as a mat file, which can be loaded in matlab, the data in a variable called Track1.

The physics of the problem: The data is collected from a shake table, a rigid platform, that oscillates back and forth, so the sharp edges in the original signal periodically, representing the point of return.


texts: Are jeweled bearings commonly used for applications other than mechanical timepieces?

texts:
Jeweled bearings use a metal spindle with a jewel lined pivot hole (pictured below).  They have been important in the manufacture of mechanical timepieces since the early 1700's.  Their importance lies in the fact that they can be machined to very high accuracy, they have low and predictable friction, and their hardness gives them very low wear.  They are known for operating in sealed environments for decades with no servicing.

With the advent of synthetic crystal manufacturing in the early 1900's jeweled bearings became the standard for every important bearing in mechanical timepieces.  Every quality mechanical watch manufactured these days, for instance, has at least 17 jeweled bearings for the 'going train'.

$\hspace{150px}$

My questions are:

Are there any other common applications for jeweled bearings besides mechanical timepieces?
If so, what are the largest jeweled bearings used for?


texts: Difference between broadcasting operation and one-to-many in RF transceiver

texts:
While writing a report on data broadcasting I came across this paper where I found description on broadcast operation and one-to-many as shown below

  broadcast operation; where a single master address many RXQ2 modules
  concurrently. (using many RXQ2 modules set to the same address)

  one-to-many; A network consisting a master and many slaves (the
  receivers all have the same address)

My question is what is the difference between these two configurations of data transition?

As broadcast operation seem to be transmitting data synchronously and as for the one-to-many there was nothing to it. I could not find any information on this online as well.


texts: Why is longitidunal force of tyre calculated negative in SIMULINK?

texts:
With the help of the Vehicle Dynamics Blockset of SIMULINK, it is easy to obtain longitidunal force (tractive force) of tyre by some of inputs. You can see one of examples below.

In this simulation, Fz is sinusoidal (like Double Lane Change), vehicle speed is ramp and Axle Torque is constant.
What is the meaning of negative Fx? Is it possible?
Thanks,


texts: How to analyse a TEC cooler in the ansys workbench software?

texts: I am currently doing a project on Thermoelectric Coolers . I don't have any experience in the Ansys Workbench software , but we have to do the analysis of the cooler . The device pretty much consists of a peltier device , a heat sink on the cold side and the hot side and 2 CPU fans attached to it . As i said i do not have much experience in pretty much any softwares other than AutoCAD . We have modelled the components in Solidworks and don't know how to proceed further . We need to find the time- temperature relation and compare it to the real-life model . Sorry for any kind of ignorance .


texts:
How is the position of a train modeled in a computer control system?

I can think of two basic approaches but I am not sure which (if any) are used in the real world.

Lat, Long

Ex: (-42, 23)

The position of the train is modeled by its real world  position. The only issue I could see with this is extra work would have to be done at some stage to determine what track the train is on.

Distance, Track

Ex: (20m, Track 34-B)

The position of the train would be modeled by its distance from the start of the track, and the track it was on. This isn't exactly as intuitive right off the bat but I think it makes more sense.

I only ask because earlier I was reading some about PTC and as I was reading this popped into my head.

Edit:

As brought up by ratchet freak it most likely depends on the sensors on a track.

I was wondering if there is anyone out there who is or currently was part of the development of such a PTC system who could speak to which method is used.

Or if there is a link to a detailed specification of a PTC system (May exist because the conversion of railways is partially managed by the government).

My guess is probably something similar to (Distance, Track) for data gathered by on track sensors and then GPS is used as a fallback which can be converted into (Distance, Track).


texts: How to identify the time delay of manipulated variables which are important to the final quality of polymer product

texts:
In a polymer production process, there are a lot of manipulated variables(MV) such as temperature ,pressure , or level of reactor that affect the quality of my polymer product.

However, it usually has "dead-time" problems in a process especially when the scale of the system is quite large.

I've already collected empirical data from the process for 6 months. Now, I want to find out the "dead-time" of each MV that has significantly importance on the final quality.

For instance, if I increase the temperature for 1 degree C, after 1 hour, we'll see the viscosity of polymer also increase for 100 cP. The time 1 hour is the answer I'd like to figure out.

How should I do if I can only analyze the empirical data on hand without doing experiment on the production lines?


texts: The Volumetric Flowrate Under Suction Condition

texts:
For a National Board Exam Review:

  An air conditioning plant with a capacity of $400$ $kW$ of refrigeration
  has an evaporating and condensing temperature of $3$ $^oC$ and $37$ $^oC$
  respectively. If it uses Refrigerant 12, what volumetric rate of flow
  under suction condition?

Answer is $0.172$ $m^3/s$

So I try:

$${ V = mv}$$

$${ COP = \frac{T_{min}}{T_{max} - T_{min}} = \frac{Q_A}{W} = \frac{h_1 - h_4}{h_2 - h_1}}$$

$${ COP = \frac{ (3 + 273) }{37 - 3} = \frac{400}{W} = \frac{400}{h_2 - h_1}}$$

$${ W = h_2 - h_1 = 49.24859678 kJ/kg }$$

I've viewed every formula in the book and many other books. I cannot find a way to find m, for mass. even so... it's also hard to find the specific volume of freon without a given temperature. How am I supposed to go about this?


texts:
I really didn't understand how to do it. Please, can anyone help me??
Determine h (t) * x (t) when h (t) and x (t) are the rectangular pulses shown in Fig. A. Plot the result of this convolution.
I answered below, but I am in doubt if the path was correct:


texts: Are there any methods to work out what appliances are running in my home from an aggregate power consumption sampled 6 times a minute?

texts:
I recently got a gizmo installed at home that samples my electricity usage once every 10 seconds. I've become a little transfixed watching the graph update as various appliances in my home turn on and off.

For instance, turning on lights results in a small and simple bump up a couple of hundred watts. Turning on the microwave a huge 1.2KW jump. The washing machine usage moves up and down depending on where it is in the cycle.

I started wondering whether there'd be some ways to automatically work out what devices are running by what you might call their 'power signature'.

Essentially what I want is an algorithm that watches what is effectively a 0.1Hz signal representing usage in watts, and can say 'Looks like your washing machine was on between 09:00 and 11:00 today.)

The complication of course is that multiple appliances can be running. As a human you can sometimes resolve that (E.g. This shape looks like the washing machine was on, but someone also turned on the microwave in the middle).


texts: How to hide part of intersection in Solidworks?

texts:
I have imported STL into Solidworks, converted it, then built an intersection of this body with a plane. I got 3 objects: first half of a body, second half of a body and an intersection ellipse.
I can select any of these parts:

On this picture I have selected one half and hovered ellipse.
I would like to sketch in a plane, having this ellipse as a reference.
Unfortunately, the halfs of the body occlude sketch for me. Hence I would like to hide them, but can't: deselecting eye icon hides entire body and an ellipse.
How to accomplish?


texts: Why we need two conductors in a waveguide for TEM propagation?

texts:
Do the two conductors have to be separated (no current flowing) or two connected lines? Of course both connected to a generator?

Thinking about the Maxwell equations I guess the two conductors are separated so we just have a static electric field between the two pieces of metal. But if that's the case why do many figures in the books also show a magnetic field? The magnetic field for what I know can only be generated if a variable current is flowing? I am a bit confused about this topic.


texts: New Part Number for every firmware update?

texts:
When developing an ECR/ECN process, the question of when to roll a rev vs. when to create a new part number must be answered.

In researching this question, I've come across multiple sources that state the principle of "interchangeability" as being the arbiter of this decision.  If the change is such that old and new parts can be co-mingled in the same parts bin, then only a drawing revision is required. If they must be kept separated because there is a change in Fit, Form, or Function (the F3 rule) that affects the next assembly, then the old and new parts must be kept separate and a new part number is required.

This seems reasonable on the face of it.  However, some things can change fairly often, such as firmware versions.  Strictly applying the rule would imply that any firmware version change requires a new part number, but this seems that it can rapidly become excessive as bugfixes and minor features are rolled out.

To be clear, I'm not asking about the version of the firmware itself - that is easily handled.  I'm referring to the PCBA into which the firmware is loaded.  We order our PCBAs from our vendor with firmware already loaded onto it.  For example, let's say that part number 12345 Rev A is the PCBA with firmware version 1.0.  If we then move to FW version 1.1 (for example, let's say we add another set of translation strings to support a new language in our menu system), I would argue that the mixing the old boards with the new would cause confusion in the case that the old boards are sent to someone who needs the new language.  So, the boards with FW v1.0 and FW v1.1 should not be mingled.

So, the F3 rule then dictates that we should create a new part number with the new FW version, designate a new bin location to stock the parts, etc.  However, the rate at which seemingly minor changes in the FW (i.e. translations, bugfixes, etc) occur can lead to an explosion of part numbers, and consequently, warehouse bin locations, thus increasing cost.

Can anyone share an alternative for such a situation?


texts: Could stepper motor lose torque because of overheating?

texts:
I have a stepper motor on a 3D printer that heats up very bad because of the heated extruder (it is actually controlling the extruder). When this system starts, it works fine at the beginning, while the temperature is rising. But after the extruder has achieved its working temperature and stepper has gotten hot too, it start skipping steps. I am wondering whether it is possible for stepper to lose torque because of a high temperature?

In my thinking:

the higher the temperature -> the higher the internal coil resistance -> the lower the current flowing through those coils -> the lower the torque.

Does it make sense? What are "okayish" temperatures for steper motors like NEMA17?


texts:
A component of a control loop is approximated by the following relation between input $x$, and output, $y$:

$y = 5x^2$

During normal operation, the value of input to this component ranges between $1$ and $1.5$. In
stability analysis of the overall control loop, what is the gain of this component?

So, I'm not sure how to solve this problem. I don't know how to create a transfer function by performing a Laplace transform because this isn't a differential equation and there is only one component. Would really appreciate it if someone could point me in the right direction.


texts: How can the air pressures exiting from a blower be adjusted?

texts: During this covid-19, I was thinking about designing a low cost simple ventilator using a blower. There is a limit of the inspiratory and expiratory pressures, the inspiratory pressure being higher. Can anyone tell me how can I adjust the pressures? I also don't know how to control the fraction of the inhaled oxygen (FiO2). Will an oxygen concentrator work in this case? If anyone wishes to look into the plan, it is in this link.


texts: Control Volume Method for Calculating Pressure Distribution in a Turbomachine

texts:
I'm looking at ways to calculate the axial thrust of a turbomachine.  The ways that i've found in books aren't the best documented.
I know I can't use Bernouli's law since the impeller will chop up the stream lines.
Can I construct a control volume with $N$ flows in and $M$ flows out and determine the static pressure inside said control volume?
If so, could this be used to determine the pressure distribution in the impeller and casing of a turbomachine by chopping the turbomachine up into a number of control volumes?


texts: Definition of the "specific material removal rate"?

texts:
I've run across a term in some grinding manufacturing research papers called the specific material removal rate. The units given for this term are [mm$^3$/mm$\cdot$s] (I don't really like this style of formatting because it makes it unclear as to whether the [s] is in the numerator or denominator, but that is the style that has been used in all of the papers that I have seen with this term). I am familiar with the general machining term material removal rate (or $MRR$), which is the volume of material removed per second from a workpiece in [mm$^3$/s], but what is the "specific" part of the "specific material removal rate"?

Usually in machining when we say "specific" we're talking about per unit volume removed. So the specific energy of machining is normally expressed as unit energy per unit volume removed (e.g. [J/mm$^3$]). But for the specific $MRR$ it is a volume per second per unit length (after all, it wouldn't make any sense to have volume removed per unit volume removed). So I guess the real question is, what is this length that we are dividing the $MRR$ by to get the specific $MRR$? Why is this term useful?

This seems like a pretty basic question, but I have been unable to find a definition for the specific material removal rate anywhere. I've looked at several papers and from context in the papers it is rather unclear. I've checked my textbook, Fundamentals of Modern Manufacturing 5th Ed. by Mikell P. Groover, no answer there. It may be a term that is specific to grinding operations.

I would appreciate it if any answers could be backed up with a source.


texts:
I have equations for S11 and S21 parameters for a bandpass filter which are obviously frequency dependent. I know there are commands like sparameters() and rfplot() used specifically for plotting S parameter in Matlab. But I can't find the equations these commands use. Also I can't get the right plot from my code no matter what I try. The S parameter I get from equation are complex doubles. Using abs() command or magnitude formula sqrt(a^2+b^2) yeilds 1 for all frequency values so I assumed I should just ignore the imaginary part and plot the real part of S11. Am I correct? Should I convert just the real part of S11 to dB using 10log(S11)?
I would appreciate any help you can give especially if you have made s parameter plots on Matlab using your own equation.


texts: Due to pandemic, there are a lot of machine shops closed and delays in getting something custom made. I was wondering how to cut a triangular glass prism (~5cm hypotenuse) in the middle so I have two half slices? I was originally thinking of ordering some glass cutters that can cut up to 20 mm thick glass, but I'm pretty sure I won't be able to cut it into smaller pieces with just that. Are there any home made conventional ways of cutter thicker than normal glass? Or is there any specific tool I can order to cut thicker glass?


texts: Determining the properties of members of historic structures

texts:
From time to time I am tasked with additions or alterations to old buildings or structures. I would need to establish the "as built" structure and from that analysis see how the amended/new structure suits the existing structural components.

The challenge lies in the assumptions one is forced to make. Over the years things change, so do the material properties and standard member sizes. For example, I have come across a bombed bridge that had to be rehabilitated in Angola. The bridge was built by the Portuguese government some time before the Angolan war. The bridge was constructed from large steel I-beams as main bearers. We could not establish the type of steel used for the I-beams, and the sectional properties we established by measuring the beams with a tape measure.

How do engineers determine the material properties of members of old or historic structures? I am not aware of any document or database that captures all steel (or rebar) manufacturers of the world with their respective product lists and material properties over time, or what design standards were historically applicable at various times in various regions of the world.


texts: Why does a simple pin-ended triangular (arched/curved) beam deflect more due to secondary effects (non-linear analysis)?

texts:
I cannot wrap my head around this.

I have made two simple models, a triangular (or curved or arched) beam that is pin ended and has a single point load of 1N downwards at it's center, and a flat beam with the same loading/supports.

The secondary effects response for the flat beam makes sense to me, It looks like this:

a) Point Load (1N)
b) Deflection using a non-linear (secondary) analysis (Light Green)
c) Deflection using a linear analysis (Dark Green)
d) Un-deformed structure
e) Pin supports

Linear analysis: The beam deflects, tension is formed in the beam
Non-Linear Analysis: The tension in the beam "pulls up" the beam so it deflects LESS.

So then, why does the curved beam deflect MORE due to secondary effects? I would assume that since the load creates compression in the members, the secondary analysis would reduce deflection and push the beam upward.

a) Deflection using a linear analysis (Dark Green)
b) Deflection using a non-linear (secondary) analysis (Light Green)
c) Un-deformed structure
d) Point Load (1N)
e) Pin supports


texts: How much force does a lock's pin have due to the spring?

texts: I found this gif, and I was wondering how much force is applied on the pin due to the spring from the top? Also, is there an industry standard for the amount of force exerted?


texts: Powering LED light using smartphone headset jack

texts: Would it be possible to power a small LED light using the headset jack of a regular smartphone, and if so, how would you connect the LED light with an audio jack. How would such an implement look like. I'm not very versed in electrical terminology so simplified explanations are appreciated.


texts:
For example, if I have an ultrasoundsensor 1 m above the ground while there is a wind speed of 5 m/s, a rough estimate of the horizontal displacement of the beam would be
$$ t \approx 2 \frac{1}{343} = 5.831\ \mathrm{ms}$$
$$ d = t \cdot u  = 2.92\ \mathrm{cm}$$
Where $u$ is the wind speed. This would mean my sensor has to decently "spread" its beams so that it can capture one of them. Let alone if $u$ is larger, which might happen in my environment. Are there any decent sources on the effect of wind on the readings of an ultrasound sensor? And how I should compensate for it?


texts: Required diameter for ballast drop hole?

texts: I'm currently an underground Geotechnical Engineer, don't spend a lot of time on the surface. I'm trying to find a reference or method for calculating the required diameter of a service hole. My Mine is looking to install a 600mm drop hole to transport ballast underground, and the ballast itself is up to 150mm. I don't believe this will be large enough and that at some stage it will become blocked, this is based on past experienced, but nothing more. I'm struggling to find a reference or method to back this up and to provide an alternative diameter. There are several "rules of thumb" from older Engineers, but no references to support them. Any help would be appreciated.


texts:
I am using Simufact from MSC Software to perform numerical simulations.
To be able to create my own sub-routines I need to have Fortran compiler installed.
Simufact manual mentions only Intel Fortran + Visual Studio. Both of them are really expensive to purchase.
I wil lbe guessing, the same method can be used for Marc and Fortran coupling
Is there a way to use open-source compilers for that? Can you guide me in this matter?
Thank you.