texts: What kind of motion information can be extracted from 3-axis accelerometer and 3-axis gyroscope sensor data

texts:
I have 3-axis accelerometer and 3-axis gyroscope sensor data coming from my bike trip. Until now I have extracted only basic information like overspeeding, hard acceleration and sudden turns.

What additional motion characteristics can I infer from this data? I also have x, y coordinates.


texts: Use npn (2n4401) and pnp (2n3906) connected to single microcontroller to switch

texts:
I want to use a NPN (2n4401) and PNP (2n3906) with both base connected to a single microcontroller output in order to switch voltage to two inputs off and on.  I'm not sure how to create the circuit I need.  Tried a basic switching circuit without getting expected results.

Here are additional details:
I am using an attiny85 to control the circuit, 0-3.3v at input to base pins of the transistors. I'm switching two lines of an led display (ltd-2601). I want to switch the two lines every `10ms in order to drive the display. So the inputs to the 2601 would be 0v and 3.3v for 10ms and then 3.3v and 0v for 10ms.  That's what I hope to accomplish using the npn and pnp transistors together (shared base pin) driven by the single line of the microcontroller. Basically, when the micro-controller line is low the npn output would be 3.3v and the pnp 0v and vice versa when line is high.  The goal here is to use only 1 line of the attiny to switch the display rather than two lines.


texts: How to determine the deflection of a wire mesh under wind load?

texts:
I am trying to extend a metal wire mesh over a large distance, while tensioning it to limit the deflection of the mesh due to the wind as much as possible. After doing some research I came across Roark's Formulas for Stress and Strain, which has a number of formulas regarding the deflection of flat rectangular plates under a variety of support conditions. In particular, I have been trying to use this formula, for a plate under a uniform transverse distributed load, with tension applied to its short edges:

However, this is assuming it is a solid plate, not a welded wire mesh. I have tried to use these equations, but with the distributed load from the wind only applied to the percentage of the area taken up by the wires of the mesh. The other problem I have run into while using theses formulas is that there are only values of the three coefficients for values of P/Pe up to 5, and I would like to investigate the effects tensioning the mesh would have with higher values of this ratio. There are other ways of preventing the mesh from deflecting besides tensioning it, but I would like to investigate this method, as well as learn about the behavior of the mesh in a broader sense.

Are there any formulas/methods of calculating the deflection of a mesh due to wind out there? Or is there a way to use Roarks to solve this problem? Any advice or direction to additional resources is appreciated!


texts: How to get the surface area of trajectory [MSC Adams]?

texts:
I'm not sure if the upper question is clear enough to understand but here's what I've got:

I've made a model of excavator in Adams View and got trajectory of it's motion (boom, stick, bucket) using trace marker.
This image shows pretty much what I've done {not mine, from Wikipedia}:

Now, my question is how I possibly can get the surface area of it's uhh.. trajectory in Adams View? Or the area that is circled in purple (dashed line) - I'm not sure what to call that.


texts: How do ultra high pressure air compressors work?

texts: I am curious about multistage air compressors used in applications such as scuba tank filling or cryogenic fluid generation. Are there any special considerations applied to the pistons used in the high pressure stages? Is there an upper limit to the pressures obtainable with conventional pistons that use rings to seal against the cylinder walls?


texts: Petrol-Electric transmission drivetrain parameters

texts:
Pardon me if this question covers too many elements;
I am not yet informed enough to fully comprehend what would be the important parameters which must be matched for such a system to work, which is based on:
An internal combustion petrol engine,
whose output shaft drives a BLDC generator,
which in turn generates power for a BLDC motor.
Essentially, what is confusing is that I find information regarding BLDCs that they are actually (perhaps only some of them; but the ones I was looking at) 3-phase AC motors which then have rectifiers to change AC to DC (if a generator), or a converter to transform DC input power to 3-phase AC, if used as a motor.
Also, as far as I understood, to power the correct sequence of coils, if using a DC power from a battery, an ESC electronic speed controller is necessary.
So, would a Petrol>Generator>Motor setup be possible without such power conversion (directly 3-phase AC from the generator to the motor) and without electronic speed controllers?
[That is, if the petrol engine has a throttle, would that be sufficient as a means of controlling how much power the generator is providing to the electrical motor, therefore directly controlling the electrical motor power output, by the speed of the petrol engine? Or do the generator and motor have to be identical for that to work, that is, which parameters need to be matched between them? The kV of the electric generator and motor (RPM/V)? or maybe their rated RPM, or pole numbers, need to be the same?
I was trying to understand this setup with the following example parameters:
Engine:
2-stroke petrol

35kW @ 6000 RPM

Generator:
BLDC permanent magnet synchronous motor (PMSM), axial flux, sinusoidal three-phase, out-runner

33kW @ 6000 RPM, 120V

Motor:
BLDC PMSM, in-runner

33kW @ 8400 RPM, 120V

the generator efficiency at the mentioned RPM is 90-96% depending on torque, but let’s ignore the efficiency for the sake of clarity.
So, what I would be very grateful to understand, is what are the requirements for this system to work properly when starting the petrol engine & changing its speed/power?
Thank you


texts: For a small water pump like this one here, how can I roughly estimate how much thrust it would deliver considering the maximal pressure (PSI) and the flow rate (L/min). As a nozzle let's assume it is just a tube with a diameter d. I am a little bit confused because pressure and flow rate probably depend on each other as well as on the nozzle diameter.


texts: Should P-Δ effect be considered for struts of a braced excavation?

texts:
Building codes such as BS5950 provide clear guidelines on how to consider P-Δ effect due to sway of a vertically loaded portal frame or single storey building, causing additional moment in the columns.

Should this sway frame effect be extended to the horizontal members of the braced frame structure in an excavation if the walls are not so stiff (such as an interlocking pipe pile wall system in water) and can move longitudinally (in-plane)? If so, how would the effects of P-delta (I am only interested in the big delta) be applied to the waling-strut combination.

I would appreciate if answerers can point to relevant literature to support the answer.


texts: I want to mount a heat source onto several heat pipes. The heat will be forwarded to coolers (four heat pipes, 200 mm) which are able to distribute up to 120 W without increasing the temperature of the device which should be cooled. The device itself will generate up to 100 W heat. Now I was wondering what would happen to the mounting point: Will the mounting point resp. the clamp used for fixing the heat source on the heat pipes also heat up? If yes, how much?


texts: What is the smallest eccentricity achieved by an artificial satellite?

texts:
As you may know, as eccentricity gets smaller, the location of apoapsis/periapsis becomes less well-defined.  Rather equivalently, I've noticed that if eccentricity is < 4e-7 when converting from Keplerian elements to Cartesian and back again, significant errors start to creep in.

I'd like to know how small of an eccentricity my code should realistically be expected to handle.  I know these issues are handled well by equinoctial elements, but would rather avoid that complication if possible.

Wikipedia says, "Neptune's largest moon Triton has an eccentricity of 1.6 × 10−5, the smallest eccentricity of any known body in the Solar System."

That's very fine and interesting, but what about artificial satellites?  What is the smallest eccentricity achieved by one of those?


texts: Toy ball check valve functionality and details

texts: In the making of an inflatable toy ball (think of a basketball), a check valve is used to assist the user in the inflation of the ball by preventing backflow of inserted air. Is this check valve made of any metalic parts (such as conventional check valves) or is it all plastic? Also, what type of valve is it? Is there a maximum pressure this type of check valve can sustain before becoming damaged?


texts: unbraced length of the compression portion of a long member

texts: I am designing a truss. the bottom chord in the first two panels at each end or at the supports are in compression and the rest of the bottom chord is in tension. there is no lateral bracing along the whole bottom chord. what do you think the unbraced length of the compression portion of the continuous bottom chord should be. I don't think we should use the whole length of the bottom chord since the tension part just would not buckle. should I use the length of the compression portion? but there is no lateral restrain where the compression portion meets the tension portion?


texts: Nonlinear behaviour of control plant and adaptive or robust design

texts:
In a paper in the context of controller design for DEAP actuators I came upon the following sentence:

  Furthermore, the nonlinear behavior of the
  control plant requires either an adaptive or a robust design in
  order to ensure a precise and accurate control.

What is the relationship between a robust/adaptive controller and the nonlinearity of the control plant?
Isn't it somehow always necessary to design a robust controller no matter whether the control plant is linear or not?
Or are nonlinear plants in general more sensitive to parameter variations, e.g. nonlinear systems sensitive to initial conditions (chaotic behaviour)?


texts: Simple examples to illustrate the utility of the Laplace Transform

texts:
I am a math professor teaching an Intro ODEs course, and most of my students are going into engineering. As such, I like to give them lots of examples of how our material is applied.

We are coming up on the Laplace Transform and I'm looking for a relatively simple example from Control Theory. I was thinking of perhaps examining a PID control for the cruise control in a car or for a thermostat (these appear to be the classic examples) but I'm having trouble seeing why we really need the Laplace Transform, or transfer functions, at all: we already know how to solve linear ODEs with constant coefficients without Laplace.

I am hoping someone can show me why we really need (or are at least greatly helped by) the Laplace Transform and transfer functions in these examples, or point me toward a simple example where we do.


texts:
I am trying to understand how to size an electric motor to pull a person up a sloped incline.
I know that I need to take into account the speed desired, the weight of the person and the friction/resistance counteracting (including the efficiency of the motor).
I'd be interested to know how you would begin to calculate the requirements

From a purely hypothetical perspective
If we could measure it in the real world with a force guage


texts: what is a quarter wave decay response after Ziegler–Nichols tuning?

texts: Ziegler–Nichols tuning creates a "quarter wave decay". What does that mean? I cannot find anything online!


texts: Tolerancing considerations for temperature rated mechanical assemblies

texts:
I am currently designing a mechanical tensile testing setup to operate at different temperatures (-20 to 100 C) in a wet environment. I plan on machining two sets, one from stainless and one from PMMA. Of course, this setup will have a clamp setup similar to the below picture.

When I tolerance the drawing prior to machining, I would probably want to tolerance both of the threaded shafts and all four of the smooth bolts for a sliding fit. How can I (or should I even try to) assess the need to consider the various temperatures when tolerancing these parts?


texts: Do mechanical engineering students learn to use shop equipment?

texts: I'm going back to college next year to pursue a career in mechanical engineering. I was wondering, along with the theoretical and CAD material you learn, is it customary that ME students learn how to use lathes, mills and other shop equipment, or is that solely taught to technicians?


texts:
It may just be my perception, but it seems like water main breaks (at least in Pittsburgh PA) are more common in the winter during the cold weather. It may just that they are more news worthy in the winter (water+cold=ice > news).

Are water mains more likely to break in the winter? If so what can be done to limit or prevent the occurrence?


texts:
How can I quickly and accurately form batches (10 to 100) of parts from mild steel wire about 3mm diameter ?

The parts are 3D with bends of several radii,  about 200mm in the longest direction with a 0.2"diam 270 degree loop in one end for a bolt.


texts: Looking for translation of "закладная втулка" (threaded bushing?)

texts:
Sometimes we need a strong threaded joint in some part that is produced using molding. Say, this part itself is plastic. Then we design the part with a hole and insert there a.. "threaded bushing"? I don't know the proper name for this element in English. In Russian it is "закладная втулка" (insertable bushing/cylinder/etc - втулка/vtulka is a catch-all term for all things cylindrical that are used in an "axial manner" - something is inserted into them, or they are inserted somewhere, or both). I'm looking for a proper term in English.

I googled for закладная втулка and found this example relevant to my text:

In the text that I'm translating into English, these brass insertable threaded elements in a plastic part produced using molding look like this:

I found a DIN on one Russian page describing "закладная втулка" and this DIN led me to English terms "threaded bushing", "threaded insert". Are these okay?


texts: Calculating the lifting force $F_{Kab}$ with SolidWorks – according to VDI 2230

texts:
I’m not sure if my procedure to simulate the lifting force $F_{Kab}$ is correct. So I illustrate my way how to get the lifting force $F_{Kab}$ using SolidWorks and the simulation tool.

I hope you can give me a hint how to solve my issue correctly or perhaps you can also confirm my procedure. Many thanks in advance.

My procedure:

According to VDI 2230 I have to do two variants of calculation:

applying the minimum assembly preload (see step of calculation R1)

in R0 I get $F_{Mmax}$ using the table A7

table A7 you can find via a google search. Enter "vdi 2230 pdf" and I think then you get a pdf and look for table A7 (see annex).

with $\alpha_A$ the tightening factor I get the $F_{Mmin,variant1}=F_{Mmax}/\alpha_A$ which is applied to every bolt

applying the maximum reduction in preloading force (see step of calculation R4)

here my $F_{Mmin,variant2}=F_{Mmin,variant1}-F_z$ which is also applied to every bolt
$F_z$ is the loss of preload as a result of embedding during operation

In the simulation all possible loads are active and are acting on the housing. The bolts are tighten in the first simulation with $F_{Mmin,variant1}$ and in the second simulation with $F_{Mmin,variant2}$.

Perform the two simulations…

To get the lifting force $F_{Kab}$ I right click the simulation results and pick “list result forces”. And now I choose “free body force”, klick the appropriate housing surface and klick the update-button. Now SolidWorks shows me the (total) lifting force $F_{Kab}$. This force divided by quantity of bolts gives me the $F_{Kab}$ per bolt which I’m interested in.

For my further calculations according to VDI 2230 I have to take the smallest $F_{Kab}$ per bolt.


texts:
"In a sling psychrometer(with dry and wet bulbs), if the moist air is not saturated(with water vapour) then it evaporates some water on the wet bulb and in turn cools the wet bulb.So the wet bulb temperature falls below the dry bulb temperature" .This is the explanation given in the book Iam using(Fundamentals of thermodynamics by Moran and Shapiro).
        1)Does this mean, the wet bulb and dry bulb temperatures are initialy same(before exposing to air)?
          2)If evaporation occurs continuously as air is blown over the bulbs, why isnt the temperature reducing continuously(it stops at a point)?


texts: Aluminum tube frame to support 2300 lbs water tank

texts:
I want to build an aluminum tube frame strong enough to support a 2300 lbs water tank. The dimensions of the frame would be 28 " wide, 72" long and 16 inches tall.
My intention is to use 2" x 2",  1/8 wall tube for the sides, back, and vertical supports.
However, on the front face i would like it open for a 'drawer step'  spanning the 75 inches.
My question is what kind of aluminum tube could i use for a header across that face to support its share of the load.
I was considering 4" x 2" tube with 1/4 wall, installed on end, making a 4" header.  Would this suffice?

Is there more information i need to provide?

Thank you to anyone looking at my inquiry


texts:
I've been going thru the book by Hodges and Roithmayr regarding dynamics theory and I can't seem to prove that:

I have tried using multiple substitutions, including the fact that every component of the direction cosine matrix is equal to its cofactor, in multiple, different ways. But I feel like I've been walking in circles. The last attempt I made was, when using the definition of angular velocity:

And then writing every derivative of the coordinate system by substituting its direction cosines and substituting the cofactors inside. This led to another interesting thing:

Which may or may not be related to the proof I'm looking for, but I cannot work out how. My guess is that this would be a pretty standard equation to use, since angular velocity is such a big thing in dynamics, but I could not find it anywhere.


texts: Reaction force at a pin joint for a rod that is rotating about a fixed axis

texts:
In this diagram, assuming there is no friction between the pin joint and the rod, I understand that the rod will rotate about $O$. However, let's say that the rod is released from $ \theta = 0$ and that when $ \theta = 90$ the rod is vertical at that instant in time. If we drew the forces on the rod at this instant, there would be a weight force and a horizontal and vertical reaction force acting at $O$. What is confusing me is that surely the horizontal reaction force at this instant must be 0 since there is no other force to balance it and no acceleration occurs in the x direction (the angular acceleration at 90 degrees will be 0 and so it follows that the linear acceleration is also 0 from $ a = r \alpha$).
However, in order for the rod to keep rotating doesn't a moment need to be applied about $O$? And in the situation where $ \theta = 90$ the horizontal reaction force is the only force that can provide this moment, leading me to believe that this force is indeed non zero. Therefore, at $ \theta = 90$ will the horizontal reaction force be 0 N or non zero and if it is non zero how would you calculate it?


texts: Water pressure an salinity sensor connected to arduino

texts:
I am trying to design a project that Arduino would have connected water and salinity sensor, would be packed in a special box be dropped into ocean up to 500 meters. What sensors should I use and how should they be connected? I assume that I would need professional equipment, not Chinese stuff from eBay.
Hardware needs to be able to work under 50°C and up to 50 bar.

Budget is about up to 400 pounds for sensors.
Resolution of pressure sensor 0 to 100 bar.
Resolution of salinity sensor doesn't matter so much. Few percent's tolerance, just to measure it somehow.


texts: what is the most optimal cost effective diameter of a hyperloop tube ferrying ALL cargo between the US and EU

texts: what is the most optimal cost effective diameter of a hyperloop housing vacuum tube housing hyperloops that can ferry ALL cargo currently travelling by air and sea to and from the US and Europe? maximum 30 tonnes


texts: How to measure the air pressure of a pipe without having water resistant sensor

texts:
I'm having a question regarding the sensors and the techniques in fluid mechanics. Since my skills are amazing in this field, here I'm asking you questions xD

I want to measure the air pressure of this tube/pipe (P1,P2,P3). This pipe will be flushed with water and then with compressed air.

[![enter image description here][1]][1]

In principle, it should be just pressure sensor in each pipe and problem solved!


texts: How to calculate the square footage of a duplex building

texts: In a college project, I was instructed to design the floor plans and the conduit layout of a duplex building. It was instructed that the duplex is 2500 square feet. No other instruction was provided. Now while drawing, should I draw 2500 square feet for each of the floors (that is 5000 sq ft altogether) or 1250 sq ft for each (2500 altogether)?


texts: Are there any specifications that address the environmental conditions items traveling though international post should be able to tolerate?

texts:
In terms of temperature extremes, air pressure, humidity, shock, ... In determining what ranges to design for in a device are there any standards or at least guidelines either by postal services or governmental departments that can be used to gauge what would be reasonable when designing an electronic device that needs to remain functional during it's traversal of the postal networks around the world.

Or do I need to go with bomb proof?


texts:
The CGNS format appears to be only applied in CFD (computational fluid dynamics). Why is it not applied in CSM (computational solid mechanics)? Is there any technical reason?
The hierarchical structure seems very reasonable and resembles that of the novel VMAP standard being developed within the CSM community.


texts: Should an auxiliary cooling fan blow air or draw it?

texts:
I have a Li-Po battery charger that comes with its own cooling fan which, like most of the cooling fans, blows hot air out of the charger to cool the charger down.

I have a spare fan and I was wondering whether it should blow ambient air towards the charger or draw the hot air away from it?

It will be an external fan outside the casing of the charger. Charger itself is roughly the size of a normal Wi-Fi Adapter and the auxiliary fan has ben taken from a computer casing.

I know it does not really make much of a difference but was just curious as to which setup will perform better in order to dissipate the heat generated a little better.

Supplementary question:

If I had 2 extra fans would it be better if one was blowing air towards the charger and other was drawing away or both should be doing the same thing?


texts: Non Orthogonal Multiple Acess and Channel Quality Indicator

texts:
As we know in a 4G network, the LTE give us a correlation about the SNR of user and the data rate of the user. This correlation is usually a table called Channel Quality Indicator (CQI) which is found in Channel Quality Indicator Feedback in Long Term Evolution(LTE) System.

My question:  Is there something similar like -LTE CQI- in 5G networks in NOMA(Non Orthogonal Multiple Access)?


texts: Importance of equilibrium and compatibility equations in elasticity

texts: What is the importance and relevance of equilibrium and compatibility equations in elasticity.  What problem do they solve?


texts: How to show gated sr latch isn't edge triggered?

texts:
How do I show this is clearly not edge triggered

The truth table for this is as follows

E
R
S
Q
notQ

0
0
0
prevQ
prevnotQ

0
0
1
prevQ
prevnotQ

0
1
0
prevQ
prevnotQ

0
1
1
prevQ
prevnotQ

1
0
0
prevQ
prevnotQ

1
0
1
1
0

1
1
0
0
1

1
1
1
0
0

Edge triggering definition: In edge triggering the circuit becomes active at negative or positive edge of the clock signal. For example if the circuit is positive edge triggered, it will take input at exactly the time in which the clock signal goes from low to high

I'm confused how to show this


texts:
A bar of length L and of uniform cross-section area A and second moment of area 1 is subjected to pull P.If  the young's modulus of elasticity of the bar material is E,the expression for strain energy stored in the bar will be
1)P2L2/2AE  2)PL2/2EI
3)PL2/AE    4)P2L/AE

(Note:The  P2L2 and 2AE in the option is P squared,L squared and 2 times AE respectively)


texts: How to convert Square FT (in.) to Square FT (ft)?

texts:
I apologize for the confusing question title. I work with area rugs, and have almost never done measurements before. I am tasked with converting these measurements into the right unit.

I have four measurements:

6

19

39

81

These are all in Square Inches I believe. On the spreadsheet it shows "Square Footage (in.)"

I need to convert them to Square FT. I'm unfamiliar with measurements, but is it any different than regular inches? Would 6 square inches be 0.5 square ft?

Thank you.

EDIT: Some were saying the question is confusing, I agree. If it helps, here is the product width for each of these measurements.

6 = 24 inches wide

19 = 31 inches wide

39 = 63 inches wide

81 = 94 inches wide

I really wish I could provide more information, but I am just as confused on the entire thing as anyone else.


texts: Could a medical ultrasound device be used for recording the topography of a small river?

texts:
I work as a research assistant in the field of water resources management.
We build small scale physical models of rivers and make experiments with sediment. The model rivers are about 20m long and 3m wide, the water depth is from 0 to half a meter. The bottom is either concrete or gravel.

One important task is to quantitatively measure the bedform that results after a model run. (i.e. where the gravel got washed away and where it accumulated)

I was wondering whether there is a chance to use a medical ultrasound device
to record the topography of the (river) bottom.
I'm hoping that these devices deliver a 2D profile of the riverbed and if I track to position + orientation of the ultrasound probe I can put together a 3d topography.

Has anyone ever done some experiments like that? I mean alienated a ultrasound device? or can anyone tell me why my idea is theoretically bad / good? Where could be problems?
Is it possible to get spatial information out of an ultrasound image?
I mean in the image the ground should become apparent very clear as there is only water between the sensor and the ground.
I'm aiming at an accuracy of the resulting topography of about 5mm.


texts: Hydraulic energy recovery for high-pressure, low flow (non-steady state) conditions

texts: What would be the best way to implement hydraulic energy recovery while de-pressurizing a pressurized volume of silicone oil initially at 1500 bar. Can a piston pump be concievably repurposed as a hydraulic motor/turbine? From what I understand, power recovery turbines are generally designed for low pressure high flow applications, and here we have the opposite. We also don't have a steady state flow, but instead just occasional "bursts" of flow as the vessel is depressurized and oil comes out.


texts: Will water level of remain level between two points

texts:
I currently have a ditch that fills with water draining out into an area  lower than the water (via a hose), but the hose for most of the travel extend above the hight of the water.

As long as the hose stays filled with water, which it should assuming the water doesn't evaporate enough, this system works. Unfortunately, the water doesn't drain as quickly as I'd like after a rain storm.

Does the piping at all effect (e.g. the volume it holds) at what level the the basin will drain to?

If I increase the diameter of the piping will the volume of water flowing out per minute increase?

Bonus points for providing the physics principles being applied here. I'm not familiar with the names.


texts: In rock drilling, how does the drill pipe in horizontal directional drilling withstand the immense force?

texts: Unlike vertical drills where the drill bit is weighted down by gravity, in horizontal drilling, the drill string is pushed into the rocks. How does the drill pipes not snap under the immense force, especially since the pipes can end up being curved?


texts: Units for plasma etching of circuits: A (with degree symbol)/min

texts:
Background: I'm a statistician working with a design of experiments example regarding plasma etching of circuits, and unfortunately, the author does not define what is meant by the units used for the etch rate ($\mathring{A}$/min). A google search has proved fruitless due to the specialized symbol and the fact that other texts also assume you already know what the $\mathring{A}$ symbol means (which is probably true for those who work in this field, but not for the rest of us).

Question: What does the $\mathring{A}$ unit mean in a plasma etching experiment, for "Etch rate ($\mathring{A}$/min)."


texts:
I am specifying pipes for a water system with 500 ppm chloride in solution.  Ordinarily we would specify 316L stainless steel to limit the corrosion, but I was asked if we could instead specify carbon steel pipe with a corrosion allowance.  So instead of the typical schedule 40 pipe, could I realistically use schedule 80 or 120 etc?

My gut reaction is that you will never really even have a "protective" oxide layer with water continually flowing, so you will just continually corrode the pipes out.  All that will be gained with thicker pipe is that it will last longer before failure, but you will have increased corrosion products to remove from the flow stream over time.
I could not really find any good resources talking about chloride effects on carbon steel pipe since the general consensus is that stainless should be used for this application.


texts:
I am planning to build an e-bike and I realized that a car starter motor would be a good motor, as it has enough power (1kW, enough for my bike) and the voltage is practical enough.
Will it handle the stress?

A mechanic told me that the coil in it would be destroyed after 30 seconds, as it isn't meant to be used a lot.
I am only interested in the motor, not the solenoid.
I will be using it at 75% of its power, at most, so not too much stress.
Will it work?
It's going to replace a 50cc motor of a piaggio ciao.


texts: double integration of continues beam to find the deflection at mid span

texts:
does any one know how to derive the deflection equation of a continues beam of three span of equal length and equal UDL load
some of the steps of this explanation I didn't understand it Here's a link Deflection Formula for Continous Beam


texts:
I often select makeup air handling units for buildings using Greenheck's CAPS tool. When selecting a model, you first select the unit based on your airflow needs. Then it will provide some choices for burners which it gives in units of Btus per hour. It is my understanding that this is a function of the unit to deliver that amount of heat over a period of time based on the volumetric flow that was selected. This would generally follow the rule of thumb for air of approximately: $$\dot{Q}_{Btu/hr}=1.08\cdot\dot{V}_{CFM}\cdot\Delta T_{^{\circ}F}$$

Does this mean that when looking at the burner selection you would have to adjust for a lower air flow rate and subsequently less output or does the temperature delta change accordingly that the heat output for a given burner would still be effectively the same even at the reduced airflow?  On any of the software packages, I can't change the flow rate AFTER selecting a unit to see how the numbers change so that I could back into the answer to check for myself and if I simply pick a lower air flow rate, it gives me entirely different burner choices.


texts: Why railroad concrete tie tips become dry first after a rain?

texts:
I've witnessed this phenomenon:

Why are only the tie tips dry? Why are only the stones around the tips dry? This is a railroad in Ukraine in the morning after a rain at night. Around 80% of observed tips looked like that, slightly elevated tips were not dry.


texts: Find the irrigation pumping rate (mass flow rate of a pump) versus time

texts:
Here is what we are given. Time ranges from 0 to 10 hours, with t=5 being solar noon. $\dot Q = 90Asin(\pi t/10)$ Watts, where A is the solar collector area in square meters and t is the time after sunrise in hours. The solar collector efficiency is 40% of the incident solar flux. The flow rate of the water ($\dot m(t)$) through the collector varies so the collector outlet condition is saturated vapor at 150 Celsius. The isentropic (only entropy is constant) efficiency of the turbine is 70% and the outlet pressure is 8 kPa. The reservoir water pump lifts water 8 meters with negligible friction. The isentropic efficiency of the pumps is 80%. I found the solar collector area required to provide $\dot m_{Pmax}$ = 500 kg/min of irrigation water at solar noon (t=5). That is the max irrigation pumping rate. Then, I need to plot the irrigation pumping rate $\dot mP(t)$ versus time over the 10 hours. We are given the hint that the irrigation pumping rate is proportional to the maximum rate (500 kg/min) times the relative solar flux at any time compared to the solar noon flux.
Would that just be (500 kg/min)*$\dot Q(t)/\dot Q(t=5)$? Where does the height come into this equation? I have all of the enthalpy values for the system from a basic Rankine cycle analysis, but I am confused about the second part.


texts: Can Peltier Modules be practically used to cool a room?

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I am thinking of building a indirect Peltier AC to cool a room of approx size 30m3. Single/multiple peltier modules will be used to cool a insulated box with water inside. The box will be kept outside the room. A pump will circulate the  cold water of the box in a pipe which will go inside the room. Inside the room, The pipe will be connected to something similar to a radiator, but rather than throwing heat into the air, it will throw cool air.
Also, I want to achieve maximum efficiency, by correctly balancing the current, voltage and temp difference.
Pumping heat out of the peltiers will most probably not be a problem as they will be water cooled.
Is this practically possible?


texts: Continuous time and Discrete time systems

texts: Why we study continuous time systems if in the real life we control them using micro-controller which is discrete time .. ?


texts: Can the core of electrical transformers be made solely from copper?

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Most electrical transformers that I am aware of have either copper or aluminum cable wound around an iron core.

Can the iron core be replaced with a copper core? Would there be any performance differences?


texts: How do I calculate the forces on a desk and its legs?

texts:
I have a design for a desk, and I'd like to not just guess at how strong it'll be, but I can't find an explanation on how to figure out all the forces involved that doesn't assume I already know a lot about engineering already.
So, if I were to apply 300lbf (1334 newtons) straight down on the front corner of the desk, how could I calculate the stress from the desktop to the upright beams, to the diagonal braces, to the ground?
Assume A500 steel, 1x2x16ga.
Diagrams

Overview
Legs
Desktop


texts: Will there be other factors such that it will affect the exit conditions of the CSTR to change ? For example, the temperature of the reactants that will be lost to the surroundings


texts: How can I square off a piece of aluminum bar after cutting without a milling machine?

texts: When I cut aluminum bar or t-slot extrusion on my bandsaw I am not happy with how "square" this edge is.  I don't have a milling machine at home, and I have been told grinding aluminum is a very bad idea.


texts: Can a piece of conductor be made invisible to radar by overdamping?

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To my understanding every conductor reemits a bit of electromagnetic waves induced in it by radiation.
If theres a way in an antenna one could create a wave of opposite phase to the incident one so that there's no net oscillating field, could it make it invisible to radar?


texts: Does the decrease in speed of the train at the curvature changes the properties of Speed Time Curve Of Urban Service

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Ok, I wish to plot the speed time curve of the my urban service . The travel includes the curvature ( as shown in image ( just for reference )).

 The train speed is decreased while it runs along the arc ( i am pretty sure ) . The question is whether this decrease in train speed is considered while plotting a speed time curve or is it considered to be negiligible. I have to plot one .


texts:
I'm a mechanical engineering undergraduate student and I want to start learning python. There are lots of online courses (free and paid) on the web but I don't know which is the most useful for a mechanical engineer.
Can someone help me to choose a suitable program for learning python?
And secondly, which syllabuses of python learning programs are necessary for a mechanical engineer?
Thanks for your answers.


texts: How to implement Pade Appromixation into State Space form

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I have a State Space model and I need to create an Internal delay. Therefore I want to take a certain Padé approximation and convert it to ABCD matrices and extend my current model. However I do not no how to implement an Internal Delay to the State Space representation. I want to construct this by myself because my model is nonlinear.

Thanks in advance.


texts: Sign of the sum of Virtual work (Direction)

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I have trouble understanding Virtual Work (in statics) as I understand what's happening but I do not understand the signs or directions.
This is what I know. If the force acts in the opposite direction to the displacement then it's taken as negative. But sometimes we don't do this and instead we take the derivative of an angle. Then, the derivative will account for the direction. (Do we also assume the direction of the derivative and plot it and that is why the following part happens?)

In this exercise, the work would be the work done by the spring in the positive y and x axis (standard) and the $W$, multiplied by their respective distances. In this case I took $d_y=-0.45\sin\theta\text{d}\theta$ and $d_x=-0.45\cos\theta\text{d}\theta$.
What I thought was substituting $d_y$ and $d_x$ into $\text{d}U= Wd_y + F\cos\alpha\text{d}x + F\sin\alpha\text{d}y$.
However in the solution it is said that instead is $-Wd_y - F\cos\alpha\text{d}x + F\sin\alpha\text{d}y$.
What am I misunderstanding? I hope it is clear what I'm trying to say.


texts: Efficiency of a planetary gearbox as a function of the lubricants viscosity

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So I have a client that is asking about if they should switch from one lubricant to another in a planetary gearbox they have.

The main advantage that this new lubricant has is that it has a much lower viscosity (about 1/2 as much) and it is more thermodynamically stable.

With all things being equal, I'm looking to try to get a rough order of accuracy estimate for the efficiency increase in switching to this new lubricant. I've been looking through some hydrodynamic lubrication theory, but haven't found anything that is really what I'm looking for.

Any known references or established theories related to this would be extremely helpful! :)


texts: one question regarding bottom up fatigure cracking

texts: We have uploaded PMS database with bottom-up fatigue cracking in csv. and PMED in dgpx. file into CAT program (Calibration Assistant Tool) trying to do the coefficient optimization. However, at the initial verification step before any optimization, the predicted data from PMED dgpx. file showing in CAT keeps zero although the total fatigue cracking originally predicted in dgpx. file is not zero. We check the bottom-up fatigue cracking in dgpx. file is zero while the total fatigue cracking is not zero. We are wondering which fatigue cracking data was extracted from PMED into the CAT? If we want to use total fatigue cracking from PMED, is there any specific field name? We can only find "FatigueBU" one. Thanks!


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Is there a kind of "handbook" for general engineering ideas and possible applications?  I vaguely remember a machinist friend mentioning some standard book to glean ideas from...
I'm in need of an extendable arm.  I wish to raise something into the air ~10-12 feet (with no anchor above), hold ~3-5 lbs, and be as compact as possible when retracted.  Telescoping mechanisms are the obvious choice, but I think their collapsed size makes them already too long (especially to reach 12 feet, with their sections being >2 feet).  I'd like to be able to carry this on a belt or small harness without being cumbersome.

My mind keeps turning to something like a retractable tape measure but I'm sure there's a better solution, and that's not stable enough to hold the weight steady.

Thanks in advance, I appreciate you reading this!


texts:
How do I calculate the maximum force on a support beam if I know the weight of the roof?
I assume distribution will be even but I cannot find correct formulas.

For example: 3 beams 60cm apart supporting a roof of 70kg/m2


texts: Determine Heating costs in $/kWh for a specific location

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Suppose I wanted to find the average heating price for a specific location in the US, where:

heating_price: The price of equivalent unit energy intensity of heating energy source (e.g. natural gas), measured in $/kWh.

Is there a public API that would return such information for either residential, commercial or industrial spaces? After doing my own research I am able to find electricity costs/general energy costs but am unable to find endpoints or data specific to heating.
Disclaimer: I apologize if this is the wrong Q/A forum to ask in advance. If you could please redirect me to the proper site/SE site that would be helpful.


texts: How much steam is emitted from an electric arc furnace in a unit of time? I have not been able to find any data on this which is strange considering the amount of water that is used to cool an electric arc furnace.


texts: Two-way pulley system considering inertia of pulleys

texts:
This is the following question.

[![This is how i tried, but I know it is wrong.][2]][2]

This is our attempt but We can't seem to solve it with inertia.


texts: How do I change the coordinate system from x-y to n-t or r-theta by using Matrix?

texts: How do I change the coordinate system from two dimensional cartesian to two dimensional curve linear and polar by using Matrix?


texts:
I need to install a replacement air handler in a facility that has an area where a large volume of particulates are in the air.  Unfortunately, the previous designer tried to get away with the cheapest design possible and just put in pleated filters rather than the bag filters that were an option in the existing RTU.
In the new unit, I would like to put in bag filters, but realized that even if they allow more throughput for dirty air, they will still probably need to be cleaned out more frequently.  Thinking about this reminded me of a baghouse on a silo that I specified awhile back and it had the functionality to effectively backwash the bag filters by running air in reverse to clean off the filter.
Is anyone aware of such a design being available for HVAC where, perhaps, a damper would flip temporarily and change the flow through the filter to run backwards and it would route that airstream as exhaust that would be dumped to the outside periodically?


texts: How to transfer rotational energy into lateral energy only when rotating one way?

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Is there a general way to convert rotational energy from a gear or something into lateral motion toward or away from the gear? I could use a piston type construction, but I only want the lateral motion to be in effect when the rotation just begins.

For instance I have a motor that turns 180 degrees each direction at an equal time interval. When it is rotating clockwise, I need a "foot" on the end to move toward the pivot by about 1/4 the total length of the leg (about 4 centimeters) and stay there until the counterclockwise motion begins.

When rotating counter clockwise, foot is extended.

When rotating clockwise, foot is drawn in.

Edit:

Here is a drawing. It may not be any help at all, but I will try to explain it as best I can with this.

In figure one the leg is at it's full extension forward and placed on the ground.

In figure two the leg pivots backward to push the body forward. this happens when anything walks.

Figure three is where I'm having the problem: the foot needs to lift off the ground so it can begin it's forward motion to take another step.

In figure four, the foot is at full forward extension and is ready to be put back on the ground for the second step, which is continued back at step 1, 2, 3, 4 and repeat repeat ect.

any living thing that walks follows these steps in order to move. I would like to replicate it in my robot.

NOTE; I have not drawn any of the leg, since the solution to this problem will likely determine what it looks like. sorry if this doesn't help at all, but I think it must be required for there to be an image for this site or something like that. :)

I have considered both the answers for a similar question on robotics stack exchange, and most of them will not work because they require continuous motion whereas I only have 180* cycles. The accepted answer ended up not working because it interfered with the foot design needing to move straight up and down and because there was no-way to stiffen the gears of the mechanism reasonably without creating too much strain for the motor when it reached full extension.

Another idea I've fiddled with is an equal gear ratio essentially always keeping the foot level and being triggered by extraneous motion upon the top gear, but it failed for the same reasons as above.


texts: Verify parameters variation in local sensitivity coefficients for microkinetic model

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I’m performing a sensitivity analysis for a model of a set of elementary chemical reactions. I’m considering the variation in species concentration ($c_{k}$) with respect to the forward reaction rate constants ($k_{f}$). Let’s consider for the moment that there is only one reaction (for simplicity). So, I have to consider the following sensitivity coefficient, which must be thermodynamic consistent (equilibrium constant $k_{eq}$ held constant) in order to define system properties (rate limiting step, etc):
$$\left ( \frac{\partial c_{k}}{\partial k_{f}} \right )_{k_{eq}}$$

The species concentration follows a governing equation in time “t” of the form:
$$\frac{dc_{k}}{dt}=f\left ( c_{k}\left ( t,k_{f},k_{eq} \right ),k_{f},k_{eq} \right)$$

We can derive a differential equation for the sensitivity coefficients by taking partial derivatives with respect to the reaction constant $k_{f}$ (at $k_{eq}$ constant) on both sides of the above equation. This differential equation will have a jacobian term, which is no problem to calculate, and a term of the form:
$$\left ( \frac{\partial f}{\partial k_{f}} \right )_{k_{eq}}$$

One can calculate the above term by forward finite difference evaluating the reaction constant at an incremental value $k_{f}^{1}=k_{f}+\Delta k_{f}$, at constant $k_{eq}$. Here stems my concern.

The reaction constant actually depends on other basic parameters, pre exponential factor ($A_{f}$) and heat of adsorption of the participating species ($Q_{k}$), $k_{f}=k_{f}\left ( A_{f},Q_{k} \right )$. Both parameters have a defined range and since the derivative is taken at $k_{eq}$ held constant, both parameters set will vary. I’d like to verify that $k_{f}^{1}$ can actually be obtained from the range values of $A_{f}$ and $Q_{k}$. One way to do this is actually calculate the values $A_{f}$ and $Q_{k}$ that yield $k_{f}^{1}$, but this is too expensive because the numbers of parameters is too high and there is no need to calculate these new parameters. Is there any strategy to verify that a given $k_{f}^{1}$ belongs to the range specified for its basic parameters $A_{f}$ and $Q_{k}$?


texts: Sacrificial Anode Marine Growth / Biofouling

texts:
https://www.youtube.com/watch?v=1ed5jkbLEOs
A link to a video of an inspection for a group of zinc sacrificial anodes is above. The video is very long but all of the anodes have the same buildup on the exterior surface. Could this buildup prevent the functionality of the sacrificial anode? The anodes appear to be in pristine condition and I wanted to ensure that this was not because of the buildup preventing passage of current.
I am a mechanical engineer, so I have very little knowledge on this subject.


texts: Decibel calculations, when to use 20 and when 10?

texts:
I always thought 20 has to be used for voltage or field strength and 10 for electric power. Now I found this formula which uses power of antennas and they use the factor 20 instead of 10, why?

Friis transmission equation


texts: computer algorithm to calculate shear center

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Without using FEA, is there a computer algorithm or numerical method available to calculate the shear center of any 2D geometry if the following are known:

geometry of the individual components of the section mesh;  centroid;
   principal axes angle of rotation;
 area;
 perimeter;
 moments of inertia
   x and y;
 radius of gyration;

Thanks


texts:
I would like to automate a door lock. For reasons I won't get into, I'm not allowed to modify the lock itself, I can only attach things to the "safe side" of the door. On this safe side, instead of a keyhole, there's a knob. I've already attached a continuous servo to this knob (the lock needs multiple turns between its locked and unlocked position). The problem now is that when opening the door manually with a key from the other side instead of via the servo, the microcontroller loses track of what position the servo is in.
I would like to solve this with limit switches in the locked and unlocked position: that way, the microcontroller can instruct the servo to keep turning until the limit switch is depressed. If the lock needed less than a single turn between locking and unlocking, this would be easy to do, but because it need multiple turns, I can't really think of a way to do this.
I am looking for a way that allows two limit switches. I considered using a multiturn potentiometer, but decided against it because I would like to limit additional torque.
An ideal solution would be low-torque, cheap and ideally 3D-printable.


texts: What are the predominant types of concrete pumps and what are their working mechanisms?

texts:
I've looked around for different types of concrete pumps and simply don't know if there are many different types, what their mechanisms are and which ones are the most predominant ones.

What I've found:

This video explains how a pump with an S-shaped tube operates.
The relevant wikipedia page explains another type, which does differ in the way how the concrete is released

 (a concrete pump)


texts: Heat pump driven by a Stirling engine that requires no external work

texts:
I was considering some theoretical limits on transferring heat from one system at to another to another. It is well known that if you have two systems at temperatures $T_1$ and $T_2$, respectively, with $T_2> T_1$ then you need to provide work to transfer heat to the system at temperature $T_2$. Now, that work is then coming from some different thermodynamic process that we choose not to describe. But leaving that out is actually compromising the ideal solution as extracting work first and then having to dump that at the system at $T_2$ is not necessarily optimal.

This led me to consider three systems at temperatures $T_1$, $T_2$, and $T_3$, respectively, with $T_1<T_2<T_3$ where we want to pump heat to the system at temperature $T_3$ but now there is no external source of work. In the limit of infinite heat capacities, we then find that ratio between the heat supplied to the system at $T_3$ and the heat extracted from the system at $T_2$ in the optimal reversible case will be:

$$\eta = \frac{T_3}{T_2}\frac{T_2 - T_1}{T_3 - T_1}$$

See below for the derivation. So, in principle at least, one can construct a heat pump that heats a house using outside environments at two different temperatures without the need for work to be provided. E.g. in winter the outside temperature near the ground could be -10 °C while at some depth below the ground it could be 10 °C.

The question is then how to realize this in practice. Presumably one would need some sort of a Stirling machine. What can one expect about the amount of heat that can be extracted from the environment per unit time in some realistic setting?

To derive the efficiency formula, one can consider a Carnot process that extracts work from the systems at temperature $T_1$ and $T_2$ and another Carnot process that acts as a heat pump between the systems at temperatures $T_2$ and $T_3$ using the work provided for by the first Carnot process. However, a simpler derivation is to consider any arbitrary process that adds an amount of heat of $q_i$ to system $i$, the First law then implies that:

$$\sum_{i=1}^3 q_i = 0$$

Reversibility implies:

$$\sum_{i=1}^3 \frac{q_i}{T_i} = 0$$

Solving for the $\eta \equiv -\frac{q_3}{q_2}$ then leads to the formula given above.


texts:
I am analysing the forces within a certain frame, and for some reason there do not seem to be sufficient equations of equilibrium to solve for all the internal forces. Is there something about this structure than makes it unsolvable without more information?

There is a frame, ABCDE, shown below. Two equal forces are applied to it (both shown as F). Assume we know F, w, and h (and from the illustration, l = w/2). Let's try to find the forces within member ADC.

First, we can analyse the frame as a whole. It is straightforward to show that Ay = By = F.

Next, we should be able to analyse member ADC by itself.

If we sum forces in the y-direction, we get:

Ay + Cy - F = 0

Since we already found that Ay = F when we analysed the whole frame, we know that Cy = 0

If we sum forces in the x-direction, we get:

Ax + Dx + Cx = 0

And if we sum moments around A, we get:

F*w/4 + Dx*h + Cx*w/2 = 0

Without going any further, we can see that we have two equations with three unknowns (Ax, Dx, and Cx).

If we look at the other members in the frame, we don't get any new information, I don't think... So what's missing? How can this simple frame be an unsolvable physical conundrum?


texts:
How you would calculate engine oil pressure of an engine? I've noticed on my car I just got, it uses a pressure switch in the oil system to measure engine oil pressure it seems in my case the switch has a threshold of 6psi to turn the pressure switch on. The dash will actually display a psi value that does change with engine speed,etc for oil pressure.

I am assuming the ecu is using a algorithm to determine the oil pressure I see on my display. This is interesting to me where exactly would you start to create a algorithm to determine engine oil pressure.


texts:
I see some example of DLX assembly instructions such as:

LW Ri, 0 (Rz)

but I can't find out why Rz has brackets around it.


texts: Calculating a transfer function from a block diagram

texts:
I've been having trouble doing this school assignment. My professor has not taught the class how to read control block diagrams so I assumed that we were supposed to research on it. I've watched a few YouTube tutorials online and have been able to grasp the rough concept of it. But I'm stuck halfway through. Shown below is the question itself and my work.

I tried expanding everything out but I'm not able to get it into the form of the transfer function that the question is asking for.


texts: How to rule-out if there's lead in a pipe's alloy?

texts:
I have a 2" diameter, 6" long pipe that I believe to be steel and want to use IF it is, heck I want to use it if it's OK to handle (ie not lead, arsenic etc..guess I can only rule-out so much!), it is very clearly a single-alloy pipe and has no markings (it is from a trunk of old car-parts, I suspect it was a suspension-spring housing or something similar, just a strong tube)
I'm usually able to comfortably distinguish metals but wanna be sure here, is there any ways to rule-out lead w/o getting a lead-test-kit?  This tube:

is magnetic,
does not quickly rust (and shows bright-silver upon scratching; is hard-to-scratch)
is very rigid (no malleability, hard on the grinder, makes a sharp 'ping' noise when flicked not the dull 'bang' of tapping lead)

Can rule-out that it's not pure-lead but have no idea if such products are typically steel-alloys, pot-metal-alloys or what....the use-case would have me handling this pipe so I wanna find out for sure, I don't weld so was very psyched to find a piece of metal precisely as-needed for a project but gotta figure out if this metal can be safely held!


texts: How to find closed loop transfer function and use it to identify τ and k?

texts:
I have to answer a few questions on transfer functions using Matlab. The first question, which I solved without Matlab, gives a time response graph for an LR circuit, and asks me to find the first order transfer function. I ended up with:

$$ G(s) =\frac{2}{s+2} $$

The next question says "determine the CLTF if the system has unity negative feedback and calculate the new values for $\  τ $ and $\ k $. I'm stuck with this part - I know that the general CLTF for unity feedback is:

$$ G_c(s)= \frac{G}{1+GH} $$

and I know that $\ H = 1 $ because of the unity feedback.
This is as far as I can get, so any help with this is appreciated!
Parts I'm struggling with are:

Is $\ G(s) $ in the unity feedback system the same as the $\ G(s) $ I worked out already? These two questions are part of the same question but I can't tell if they follow on from each other or if they're separate. This is all the info the questions give so I can't think what else $\ G(s) $ should be in the feedback system.
I obtained a CLTF for the system using $\ G(s) = \frac{2}{s+2} $ and $\ H(s) = 1 $, and got $\ G_c(s) = \frac{2}{s+4} $, but as I said above I'm not sure I'm using the correct value for $\ G(s) $, because when I try to work backwards to find  $\ τ $ and $\ k $, I get the same values as before.
Most importantly - if these values are wrong, which I believe they are, how do I use Matlab or ServoCad to obtain new values for $\ τ $ and $\ k $? Where τ is the time constant and k is the gain.

Thanks!


texts:
I've got the following sketch:

(A vertical line of 3mm, 5mm from the center of the sketch, with an arc running from end to end.)
FreeCAD indicates that this sketch is fully constrained. However, removing the horizontal 5mm constraint, dragging the points around, and re-adding the horizontal constraint I can create the following:

My constraints and components are exactly the same. Why is this sketch "fully constrained"?
I've noticed other examples when suddenly an arc would become a full circle. How do I tell freecad "my arch should be less than 180 degrees" or "more than 180 degrees"?


texts: Is there any frame of reference in which we can neglect the gravitational force?

texts:
There is a laboratory in which there is a string tied to a bob on the earth.Consider the earth is perfect sphere ,rotates on its own axis in a circular path with uniform angular velocity.  Main Q of this concept is to find apparent weight of the object but I have some more Q related to this.
So , I tried to draw every possible frame of reference I can. Pls check if it is correct or not.

In earth frame of reference , I excluded the centripetal force and added a pseudo force. My confusion in this part is that if as an NIF , I look at the box from earth. Does it mean I am inside the earth on the ground or can I say I am a person running on the earth surface (I.e as if I am 1million feet in height )who has same acc as that of the box on the ground of earth or are both the situations same in meaning ?.
My Q 1:is that is it possible if we can take a non inertial frame due to which when I consider the FBD of the box , the mg or N force is not present.
It is more like I also wish  to know when do cos die the mg , N forces. I am not getting when to exclude them in NIF.


texts: Overcurrent protection, limit for nominal current or stall?

texts:
Background: I'm currently working on a robotics design that will drill through soil.
I have selected a 48V motor who's nominal current is 3.17A and has a stall current of 42A. I will be driving the motor with a microcontroller and motor driver.
However I am having some trouble with my design.
The motor driver includes over current protection circuitry, and I need to select a resistor to set the max allowable current.
Would it be more optimal to use a resistor that caps the current at exactly 3.17A? Or would it be better to provide some margin, and make it 4A?
The over current circuitry has a feature where it resets itself after every PWM cycle and checks if the current is too large again. I believe this is "current chopping" so the motor should start up. (Startup time is not necessarily important for this.)
Extra information:
Here's a link to the datasheet (overcurrent info starts at the bottom of page 12)
DRV83x2 Three-Phase PWM Motor Driver
Any input would be appreciated. Thank you for reading


texts: How can I validate the validity of a model of a dynamical system?

texts:
I derived a non linear differential equation system for a mechanical system. However I doubt the correctness of it.
So I compared the model's dynamics with a VREP simulation. I did this by
by Euler integrating the model with the same step size as in the simulation, and then comparing the state variable from the simulation and the  model.

I wonder if this is a valid approach, and if there are other ways of doing it


texts:
I have to design a model of a domestic boiler.
I represent the boiler as a heat exchanger (HEX1), as shown in the figure.
In many articles I have found that it is schematized with this equation:

$$ M C \frac{\text{dT}_{10}}{\text{dt}}=\text{c m$\_$dot} \left(\text{Ti}-T_{10}\right)-Q $$

where $M C$ is the thermal capacity of the boiler, and $Q$ is the heat product by the burner.

My question is: why there is $\frac{\text{dT}_{10}}{dt}$ at the left hand side of the equation? Why not $\frac{d\frac{\text{T}_{10} + \text{T}_{i}}{2}}{dt}$ or $ \frac{\text{dT}_{i}}{dt}$?

Thank you!

Update:
Connor thank you for the answer. However I don't understand:

  And finally, the rate at which heat is stored within the control
  volume is proportional to the rate of change of temperature of the
  exchanger: $$Q_{stored} = M C \frac{dT_{10}}{dt}$$

Why the temperature is $T_{10}$?
I have found that a possible answer is ralated to the so colled "well-mixed conditions", infact in a article:

  "the time derivative of the total energy in the mth block is
  calculated on the basis of the well-mixed condition"

Is there a better explanation of the well-mixed condition?


texts: What are the strengths and limitations of the antenna design of the Montjuïc Communications Tower?

texts:
The Montjuïc antenna is an interesting design for an antenna.  I presume the design is principally an antenna, but perhaps it is not?  If the ring + mast is an antenna, how does the ring work to augment the mast of the antenna?  Is there something that lets us know that the mast contains many smaller antenna, and the ring is just for aesthetics?

(I've heard it is also a sundial, so maybe the ring is purely to act as an horologue?)


texts: How many decibels does wind buffering reduce from ear muffs protection?

texts:
I have a hearing condition and need to wear ear muffs on my scooter.

My muffs are 3M Peltor with a dB rating of 35dB.

When riding my bike, the combined noise from the engine and the wind is about 80dB.

Now in theory that should get me into about 45dB, but it seems the wind buffering makes it louder.

In other words, the muffs take off 35dB at rest, but with movement and wind they get louder from inside my head because of the wind buffering.

Are there any specifications or any research done on wind impact decibel levels on muffs for ear protection?


texts:
When conducting an eigenmode analysis, we get a sequence of different modes with their respective eigenfrequencies.
My question is: Are all of those really relevant in every application? Take for a very simple example a spring in zero-gravity that is excited periodically by a longitudinal force. Surely it also has (among others) transversal eigenmodes, but they shouldn't get triggered, right? Since this is a rather abstract example, the same should apply e. g. to the longitudinal modes of a rotating crankshaft. So can we neglect such modes or do we have to assume every system is so imperfect that every mode gets triggered in some way (given its frequency is included in the excitement spectrum)?
Also, e. g. during startup, machines often audibly pass eigenfrequencies. But how can the corresponding mode be triggered if the drive just accelerates rotationally and does not oscillate?


texts: What type of test signal is appropriate for frequency response analysis of string instruments?

texts:
I want to test the frequency response of stringed musical instruments . My test set-up includes a piezo film transducer which is just taped onto the instrument and fed a signal which then vibrates the instrument. The resulting sound is picked up by a calibrated microphone and sent to a spectrum analyzer.  The strings are damped with memory foam so their vibrations are damped.

I would like to know if it matters what kind of test signal I send to piezo element. Should I use single frequencies, a sweep or "chirp" signal , or a broadband noise signal such as pink or white noise.


texts: During tensile test, why does the specimen's(let's say mild steel) volume changes during elastic deformation and does not change during plastic deformation?


texts: How to properly validate transverse isotropic elasticity Finite Element Code

texts:
I have written a piece of code solving the linear elasticity problem on transversely isotropic materials (before that, the code only supported isotropic materials).

I would like to validate it before using it for other applications, have you got any idea how to do it ? I would like to be sure that the 5 independents coefficients : E1, E3, nu12, nu13, G are well integrated in the code.


texts: How to find maximum acceptable deflection?

texts: I have a beam. I have its Young's modulus. I don't have its maximum acceptable deflection. How can I determine the maximum acceptable deflection without breaking the beam?


texts: What happens to silicone gaskets (siloxane rubber) in presence of ethylene glycol?

texts:
Normal sealings and gaskets are made from NBR for use in conjunction with aqueous solutions of ethylene glycol which are common coolants for various purposes.

However to keep sulphur out of a cooling system and the surrounding area I want to change NBR sealings against silicone sealings. I've read some vague information about reduced stability of these sealings in glycol containg coolants. But what is the detailed behaviour? Will it intumesce, brittle or deteriorate otherwise?


texts: Coupler to connect motor shaft to perpendicular rod/shaft

texts:
I have a stepper motor (this one). Its shaft is of type "oval" or whatever, so like a circle but with 2 flat sides.

Imagine the motor shaft pointing straight up, in the z-axis. I want a 6-inch rod, or shaft, (honestly doesn't really matter, I just want a rigid metal stick of some sort) to stick out from it. I.e. So that when the motor spins, this rod/shaft is creating a circle in the x-y plane.

I've gathered that what I want is a "coupler", possibly a "flexible coupler" which connects shafts which are NOT parallel.

1) Is there a standard term, or language, for describing my motor's shaft, as well as the coupler which would connect my shaft to a metal rod?

2) Am I even choosing the right things for this task of spinning a rod perpendicular to the shaft's axis?


texts: What are the pros and cons of using Zibgee over BLE or vice versa for IOT application?

texts:
I am currently working on develop an IOT architecture.  The sensing devices are to be integrated with microcontroller. The microcontroller will be integrated to some type of RF communication device.  As the community is well aware RF communication protocols that will fit the bill. Once in consideration are Bluetooth smart/BLE, uIP, zigbee and Zwave. I intend to use module primarily to address FCC certification issues. At this point Bluetooth smart/BLE and Zigbee are the prime candidates.

Question: From an Embedded Systems design standpoint what are the pros and cons of using Bluetooth smart/BLE over Zigbee or vice versa

References:

uIP (micro IP)


texts:
Given the dreadful surge of COVID cases in India, with people dying for lack of oxygen, I was wondering if the smart folks here could put our heads together to brainstorm a way to develop a how-to manual on how to cobble up a DIY oxygen concentrator to help them.
If I understand it correctly, the principle is simple enough - we need a zeolite-filled pressure vessel that can take around 20psi, pressurise it with air and then relieve the pressure. The gas that comes out first should be oxygen-enriched, with the gas at the end nitrogen-rich. Over time the oxygen enrichment in the gas coming out falls, and the nitrogen concentration rises.
The question is, how to cobble this together with everyday items with little to no engineering workshop capabilities, perhaps even in a home. The goal is to let the manual describe several DIY oxygen concentrators at varying degrees of complexity, based on the user's expertise and access to engineering support. So start with a basic human-operated one, and then add complexity such as automatic pressure swings perhaps controlled by an Arduino or Raspberry Pi, and an electric pump.
A bicycle inner tube is a possible starting point; it is common, can take pressures up to 120psi and already comes with a valve to pressurise and de-pressurise it. Couple this with a bicycle hand pump as the initial model. Alternatively a soft drink bottle can be pressurised from 30 - 50 psi, but a way to add a valve to it will be needed.
What about sourcing the zeolite? Do we need to worry about contamination of the zeolite by humidity, dust, etc? What about inhalation of the zeolite dust by the user? Which means we would need a filter and trap too, at the valve.
P.S. I don't know what the law is in India regarding the DIY development of medical devices in an emergency/pandemic, but one may hope that saving lives takes precedence over licensing in times like these.


texts: Calculate or approximate force required to expand a thin-walled elastic cylinder held rigidly at both ends?

texts:
How might one calculate or approximate the negative pressure applied to the outer surface of a cylinder required to expand it a certain distance, when held open rigidly at each end?

The cylinder ID = 20*the wall thickness and the material is very elastic.

Many thanks for your help!!

Oli


texts: Does gravity have any effect on metal casting?

texts:
I wonder if the presence of a gravity field, makes any difference in the properties of the finished parts?
That’s only if we can somehow, keep every other factor almost the same.


texts: How can a curve in Gabrielli-Von Karman graphs curve down?

texts:
Gabrielli-Von Karman graph plots the specific power, that is, power required to move certain weight, against speed. It gives an idea how much power is required to move certain mass at a certain speed using a certain vehicle.

There are some vehicles whose curves go down at some intervals, such as helicopter, racecar and jet fighter. How does this happen? Curving down implies that we need less power at higher speeds. Why would this be true, especially for aircrafts as we know air resistance is highly proporsional to speed?


texts: Could Bidirectional Rotary Damper be good for a 3D printed car steering?

texts:
I am designing a car steering and i do not want to use any sort of gears or motor. Would a bidirectional rotary damper work?
I want the steering to feel more real and not too free.


texts: Equations for power transmitted by a flat belt drive

texts:
I've come across two equations that relate power transmitted with the belt tensions:

$$\begin{align}
P &= 10^{-3}(T_1 - T_2)(k)(v) \\
P &= 10^{-3}(T_1 - T_c)(k)(v)
\end{align}$$

As you can see one equation is based on slack side tension ($T_2$) and the other is based on centrifugal tension ($T_c$).

My question is when should I use any one of those two equations to find power.


texts: What type of ultrasonic transducer would be suitable for ultrasonic welding?

texts:
Project background:
I am working on a project where i need to weld plastic using ultrasonic transducers.

Problem:
Since I'm still learning engineering, I have a hard time figuring out what all the factors are in order to choose the right transducer.

What I've done so far:
I have searched the internet to find information regarding this subject, but due to (what seems to me) the wide area of knowledge needed, I haven't found anything that I properly can comprehend.

Question:

Basically: What do I need to take into account when choosing a transducer?

Not-so-basically:
I suspect that the properties of the material certainly affects the welding process, so here comes a sidequestion: what properties of the material do I need to know in order to calculate/decide which transducer to use?


texts:
With linear bearings, could they be used to join one rod with another to form a cross-junction and rotate with around a 0.3N-mm torque? Suppose the rods are fairly thin, eg, 5mm in diameter. That is, could linear bearings bear a radial load? Would the bearings deform?

UPDATE Here's a diagram

Suppose the blue rod is attached to a gear driven by a motor. The blue rod itself is also attached to the bearing's housing. The blue essentially rotates and drives the black, exerting force/stress on the bearing. The idea is to mount a slidable camera on the black which can be rotated by the green gear.


texts:
I came up with this concept for a partial rotation, lubricant free, low friction bearing for a robotics application. Two complementary sets of tensioned tendon-like cables (or tapes) serve both to constrain the degrees of freedom of the joint as well as the rolling surface. Here's a render of a model I made to illustrate the idea:

I'm sure that I'm far from the first person to have had this idea, but having no clue about its proper name nor about how to describe it, I'm unable to find anything on the net. I guess it's best described as a kind of flexure, but what exactly? Has this mechanism found any real world applications?


texts: What are the differences between Gauge and Absolute pressure?

texts:
I am aware that Absolute pressure is zero-referenced to a perfect vacuum and Gauge pressure is zero-referenced to ambient air pressure. So, Absolute pressure is equal to Gauge pressure plus atmospheric pressure.

However, the Part B of this problem, confused me on what the absolute pressure under piston B is, which comes from the fact that the system is open on both piston A and B. In this case, is the (Weight of block)/(Area of piston), Gage or Absolute pressure?


texts:
I am running a simulation of fluid flow and then doing an actual physical experiment to confirm the results of the simulation.
My simulated results show a value of 0.529 m/s and my experiment show a result of 0.532 m/s. So the values differ by less than 1%. (* It really doesn't matter what the number refer to *)
I studied accuracy and precision in my Physics classes. But, I can't figure out how to "prove" to myself, using math or rational logic 8-), that a less than 1% difference is basically "accurate" or "the same"..


texts:
Exactly what are "ceramics"? I found a lot of similar "definitions" of that term online, e.g. on Wikipedia and here.

These (and other) sources essentially state that ceramics are non-metallic, non-organic materials. And they state the most prominent examples.

But these only seem to be necessary properties. Are there sufficient criteria based on which one can definitely decide whether a certain material is ceramic? Is this list of criteria comprehensive?

Is there even a widely accepted clear definition at all?


texts: What are the risks and possible mitigations of installing ground anchors under spread footings?

texts:
I am installing a retaining wall in front of an existing bridge abutment that is supported by a spread footing. Because of the geometry of the site, ground anchors are required to help support the wall.  These ground anchors will be be bored under the spread footing of the abutment.

The bored diameter of the ground anchors is approximately 6". These holes will be filled with grout after the steel anchors have been installed. The distance from the bottom of the spread footing to the anchor can be as little as a few feet vertically. This has raised a few concerns.

The biggest concern seems to be causing the bridge abutment to settle while the borehole is advanced. A secondary concern is the bored hole collapsing from the high soil pressure before it can be filled with grout.

Are these concerns reasonable and what methods can be used to mitigate the risks?

If these boreholes were typical drilled shafts, I would say that the holes should be cased while being drilled or slurry should be used. Neither of these options seems to be a common practice for ground anchors. This can't be a unique situation though.


texts: What kind of mechanism can be used to rotate a part in 180 degrees (Ψ (yaw)) and 30degrees in  (pitch) direction?

texts: Let's say we have a flat object. We are asked to create some mechanism so that the part can rotate in the shown angles above. What mechanisms can be used?


texts:
I was a doing a placement at a company, and they were designing a new heat pump. I was told the more compact you can make a heat-pump, the better it is for efficiency, and they mentioned something about this was because the power density was increased.

I get there are benefits from using less material and making something lighter which would improve efficiency in that regard, but I don't get the benefit of a higher power density in a heat pump. I understand that in a heat engine like a combustion engine you want a high compression ratio so you'd want to make the thing as compact as possible, but why is a better power density also good for a heat-pump? Is it this just the thing with all types of machinery which have some sort of volume which is compressed? If so Why?

Edit: I didn't really want to say COP but rather efficiency to keep the question more general. These guys seemed pretty certain that having a small high rpm heat pump gave improved performance, whilst I assume they meant COP could be something else they are looking at. Maybe a better way to ask this is: Are there any theoretical benefits to the COP of a heat pump by making it smaller?


texts: Locate the centroid of the plane area shown

texts:
QUESTION:

I need help, can someone help me show how we get the solution as stated in the question; as i am trying my very best to solve.


texts: Can we say kinetic energy is tangential K.E?

texts:
I saw this in my textbook that
$\dfrac{\text{d}K}{\text{d}t} = \dfrac{\text{d}(1/2mv^2)}{\text{d}t}= F_t v$ where $F_t$ is the resultant tangential force on the body.
Now, let $F_t= F\cos\theta$
$$\dfrac{\text{d}K}{\text{d}t} = F\cos\theta v = Fv = \dfrac{F\text{d}r}{\text{d}t} = F\text{d}r$$
So , by writing resultant tangential force . Does it mean that resultant force on the body only or this $F_t$ is a component of resultant force .
If it is resultant force and not a component of it. Then why to write tangential ?
Do we also have radial force then. A resultant must have two components where  $F\sin\theta$ is the radial force or 2nd component. So , we can’t use dot product here but have to use magnitude of  cross product right.. So , will that be right way to solve it ? .
$F \times \text{d}r$ (vector cross product and radial force)?


texts: Does impeller design have a specific cause on how the fluid will flow in a centrifugal pump?

texts:
I am a student learning about centrifugal pumps in my studies.

I’ve learnt about the 3 different type of flows - axial, radial and mixed.

I’ve also learnt about different impeller designs - mainly - opened, semi-enclosed, enclosed.

I was wondering, how does these 2 link together ? For the types of flow classifications, when does these different flows occurs ? And does the impeller design have a specific cause on how the fluid will flow ?

And also which flow is ideal to operate under ?


texts:
The Bond number is a dimensionless number typically used to analyze cases where two fluids of different densities are in contact and subject to gravity only.  I'm analyzing a system where gas and liquid are entrained in a pipe (think garden hose with trapped air pockets), and both are subject to high accelerations, much higher than gravity.  I'd like to modify the equation for the Bond number to use my known value of acceleration in place of gravitational acceleration, but I can't find any published literature where someone has done this.

What I want to do is this: $$Bo=\frac{\Delta \rho a L^2}{\sigma}$$ where $a$ has replaced $g$ in the traditional equation: $$Bo=\frac{\Delta \rho g L^2}{\sigma}$$  Anyone have experience or at least comments on my approach?


texts: Laplace transform and output of affine systems in Simulink

texts:
I have a system $h$ which takes as input $u(t)$ and outputs $y(t)$. It is known that the relation between $y(t)$ and $u(t)$ is affine (i.e. $y(t) = h(u(t)) = a u(t) + b$). Apply Laplace's transform to $h(t) = a t + b$ gives me the expression:
$$
H(s) = \dfrac{a}{s^2} + \dfrac{b}{s} = b\dfrac{(s + \frac{a}{b})}{s^2}
$$
If I understood correctly, the Laplace inverse of this expression is always $at + b$. Hence I assume that the two expressions $h(t)$ and $H(s)$ are related, if not the same (but only different in representation).
If I introduce a unit step into the input, in the time domain representation I expect a change of value from $b$ to $a+b$. As I understand, this should also be the same expected behavior with e.g. a continuous-time block. In Simulink, I tried to implement both representations (time domain using multiplier and addition blocks, Laplace domain using the transfer function block). I had no problem with the time domain representation, but the Laplace domain one did not give what I expected (it became a sort of ramp).
What could I have done wrong?


texts: How is a mechanical system designed and tested without building a physical model?

texts:
I am new to mechanical engineering, although I have a scientific background (postgrad in Mathematics), and I (mostly) code for a living.
I have an idea about creating a mechanical device; I envisage it will entail gears, linkages and actuators.
I have a rough idea where things will fit but I would like to be able to test and tweak the design in software before building the actual device. As a point of clarification, when I say "test," I mean view via animation, for example, whether two items will collide when in motion, or if there is sufficient leeway between them as they move past each other.
This allows me to do the design and simulation testing of the parts, before finalising the design and then building the physical system from the design.
The stages are:

Build the 3D design in software
Run simulation to see if it "works," if not fix design and iterate
Build physical system from design that "works"

I have figured out that the system consists of three subsystems working together.
So, I would like to design and test each sub-component before integrating them into the complete system.
My question then is this:

Is this how design is done in the real world?
What are the pros and cons of the scheme I have planned?

I am intending to use FreeCAD to do the design and testing.


texts: What is the maximum deflection and bending moment of a hinged hinged beam?

texts:
It is not a simply supported beam with one end hinged the other end with roller support. I am working on both the ends hinged beam. i.e at the two ends only rotation about z axis is allowed and all other dof are zero. Or constrained in X,Y,Z and about Theta X, Theta Y and  free to rotate about Theta Z only.
Point load is applied at the center of the hinged hinged beam.


texts: What are the longitudal tolerances of thread on metric nuts and bolts?

texts:
It's not exactly my area of expertize and I've spent a couple hours ears deep in norms, and I'm not really sure if what I found is correct (the figure I found was to the order of 1$\mu$m).

When using standard (off-the-shelf, not specialized) threaded pin / bolt and a matching nut for a lead-screw actuator, what degree of imprecision (free lengthwise movement of the actuator without the shaft turning) can I expect coming from the allowed technical tolerances of the thread?  In other words, what amount of play can I expect between a threaded bolt and nut?

To be more specific,  I realize there will be movement from lateral and longitudinal flexibility of the shaft; from its mounting bearings; from its axial twist against the drive; and probably quite a few other sources, but I'd like to know this specific factor - how much of a "give" or play can there be in a thread, allowing movement of the nut along the bolt without either of them turning.

I suspect that this changes with the shaft diameter, so a table or a method to calculate the amount of play for most common metric threads would be preferred for an answer.  If that's too difficult or doesn't exist, I'm most interested in the value for M10 thread.


texts: Is it practical to increase engine efficiency by preheating petrol from engine heat waste ? is it applied in any automobile?

texts:
I found some article related to preheating the fuel to increase fuel efficiency, but I rarely see such implementation, I assume that it's less effective compared to others

But is it really possible to increase the effectiveness of preheating ?
Is preheating using fuel waste applied anywhere ?

enter link description here
enter link description here


texts: How can I apply a load to an electric motor to simulate realistic conditions for an experiment?

texts:
I am trying to perform some experiments with a motor and I want to run it under realistic conditions (or at least not unloaded). Is there an easy way to load a motor?

A couple ideas I had include: attach water paddles to paddle water continuously, attach pulley to lift weight, clamping brake pads (getting desperate), ...

I am working with a 1/3 HP three-phase motor.


texts: Can Peltier Modules be used as an Air Conditioner?

texts: Air Conditioners are very expensive so I'm planning to build a split type air conditioner using Peltier modules for my sealed room that is 6.5 length, 7 feet height, and 5.6 wide. I plan to use nine modules. To cool the room, the cold side will be attached to a copper heatsink with pc chassis fans to circulate cool the warm room air in between the heatsink layers. To cool the other side, I'm going to insulate the hot side and I'll use a liquid cpu cooler with coolant where the radiator is placed outside the room. To increase the efficiency of the modules, I'll use a voltage regulator which can adjust from time to time. The cost source all of the parts is 60% lower than buying an air conditioner and the power usage per day is also lower as far as my computation. Is it practical or are there any designs/modifications that can make it better?


texts: Deriving the deflection force equation for a beam that is fixed on both ends

texts:
I want to calculate the force-displacement equation for a beam that is fixed at both ends. I think I should use the superposition principle but I am not very sure how to get started.

I know that for, say, a beam with one fixed-end and applied load $P$, then:

$$\begin{align}
EI \frac{d^2v}{dx^2}&=\mu_0\\
EI \frac{dv}{dx}&=\mu_0x+C_1\\
EI v(x)&=\mu_0x^2/2+C_1x+C_2
\end{align}$$

How can I solve this for a fixed beam on both ends?


texts: Why is the minimal bolt edge distance not affected by plate thickness?

texts: Eurocode specifies minimum distances from a bolt hole to the edge of the plate. But why is the bolt diameter the only relevant parameter? Why isn't the minimal distance also a function of the plate thickness? Intuitively, I would think that with a thicker plate we could place a bolt closer to the edge since there is more area perpendicular to the force affecting the bolts.


texts: When I try to spin my stepper motor faster then 1000 pps, it vibrates and doesn't move

texts:
Im trying to get my stepper to spin faster then 1000 pps, and my torque curve on my stepper's datasheet is showing it being capable of that(https://www.omc-stepperonline.com/download/17HS19-2004S1_Torque_Curve.pdf) but when i try to spin it faster then 1000 pps, it vibrates violently and does't move.
I'm giving a drv8825 24V 2A max as the datasheet specifies, and the DRV8825 max pulses is 250 khz, which is significantly more then 1000 pps, so I think its a code problem.
My code:
int main() {

xEN = 0;
yEN = 0;
xDIR = 1;
yDIR= 0;

for(int i = 0; i < 1000; i++){
                xSTP = 1;
                wait(0.001);
                xSTP = 0;
                wait(0.001);

            }

}

I've read stepper motors need to be accelerated towards higher RPM, but im not sure how to do that. Like, how would I achieve 3000 pps?
EDIT: This seems to spin incredibly quickly and loudly but anything in the middle of this seems to just vibrate violently
int main() {

xEN = 0;
yEN = 0;
xDIR = 1;
yDIR= 0;

for(int i = 0; i < 1000; i++){
                xSTP = 1;
                wait(0.0005);
                xSTP = 0;
                wait(0.0005);

            }

}


texts: problem in the calculation of pressure drop for an axial turbine

texts:
I am simulating an axial turbine. In this turbine, there are two domains.

The first domain is the piping before and after the blade and the second domain contains the turbine blades. The domain containing the blades rotates at 2000 rpm=209.43 rad/s while the other one is stationary.

There three pair of rotational periodic faces in numerical model( one is for inlet stationary domain and other one is outlet stationary domain and other one is for rotation domain). In fact, there are three pairs faces parallel to each other.

I validated torque of turbine with experimental values but pressure drop at inlet and outlet of turbine doesn't validate with experimental value correctly. In fact, pressure drop is law and it should be higher. How do i solve this problem?

I am grateful that guide me about this case.


texts:
I'm currently trying to replace a broken battery for an electric moped, but the old one had two power ports,  one for the engine and one for the lights/horn.  I haven't been able to find anything that seems suited for splitting a 48volt 30amp connection into one 25 amp and one 5 amp.
If anyone could share a blueprint and a quick explanation it would be greatly appreciated.


texts: Which components to use for a CO2 gas storage?

texts:
I have a CO2 production for my aquariums (currently 2, but the solution should be extenable to - let's say - 5) based on fermentation of bio mass (CO2 is used as fertilizer there) which consist of a bottle, a connector, valves and diffusors and flippers which help dissolving the CO2 underwater. They're connected with 4/6mm tubes.

Since the efficiency of the fermentation is irregular the presure in the system varies. Extranous CO2 is released into the water, but can't be dissolved and thus is waisted.

I want to avoid that by adding a storage which collects CO2 if the pressure in the system is above 2 bar and releases it when it's below. What components can I use for such a system?

Plan:

CO2 source -->--|-- valve 1 -- Aquarium 1 (diffusor, underwater)
                |
                |-- valve 2 -- Aquarium 2 (diffusor, underwater)
                |
                |-- ...
                |
                |-- storage

Functional sketch of my idea for a storage:

                                                      |---------|
-->- backstop valve opening > 2 bar before storage ---- Storage ---- pressure regulator opening < 2 bar after the storage --
                                                      |---------|

The storage isn't necessary in the scenario since the CO2 is cheap and over-pressure could easily be released in the room (1 1.5 l PET bottle with water and sugar can't cause a hazard). It's more of an engineering exercise.


texts:
I have a 3 phase motor and 3 phase power supply (400V, 50Hz)

Currently this motor produces 1.5hp in torque and ~1750rpm. I need it to produce less.

My question is:

Is the best way to go about this, a rheostat or a VFD? The cheaper the better.


texts: I have searched everywhere for the stiffness matrix of GFRP, but there isn't a single paper or site that experimented the full matrix. Is there any sort of database for the stiffness matrix of many composite materials?


texts: Drilling holes in ground and fillin with gravel - to what ends?

texts:
Near where I live there's a construction site for a new supermarket. The last week or so they did things I don't quite understand.

Some background:

The ground in our area (Ruhrgebiet) is rather clayey
The site is near a small hilltop, the area generally drains into the Ruhr
The site was excavated maybe 2m deep (below ground level) and filled in with 1.5m of sand gravel mix.

Now the part that I don't understand:

An excavator with a drill drilled through the sand-gravel and the soil beneath, maybe 3m total depth (below ground level), I guess 0.5 m diameter
The holes are set in rows, maybe 2m apart
A huge machine that on first glance looks a bit like the ones they set sheet pile walls with drives up to each hole, inserts a pipe and (appears to) fill the hole with gravel - not the sand gravel mix, but fairly large, roundish individual stones with no small infill material
I see no way that a binder or water could be added to the gravel - there's just a funnel for the gravel and a loooong pipe that is entered into the hole. I don't think it's for a pile foundation.

Picture of the machine (not from "my" site, but from here - sadly no explanation what the ultimate purpose is):

The funnel can be hoisted up near the end of the pipe, or lowered to be filled by front loader.

My theory is that this is for surface water drainage - water will percolate through the sand-gravel mix and then into lower ground layers though the highly porous gravel. There are a few other sites close by dedicated to infiltrate storm water into the ground, so maybe this is a thing in my locale. The image source has someone describing the machine purpose built for "Kieseleinbausäulen" (Gravel infill piles) but I don't find that term anywhere else.

Ultimately I don't know (and the only way to really find out is to ask one of the guys on site, but so far they've been to far away from the fence when I came by), my question is: To what end does one drill holes and fill them with gravel? Is my hunch correct, are there other explanations?


texts: Solidworks Simulation- Large displacement with Inertia Relief

texts:
I'm trying to use the Solidworks simulation package to solve for the stresses inside a body as it accelerates (very rapidly). Because I expect some small features to deform quite a bit, I need to use the large displacement option, but because the object translates through space, I need to solve it using the inertia relief option. When I start the simulation with both option checked, I get the error message:

Inertia Relief with Iterative solver is not supported by Large Displacement. Please use the Direct Sparse Solver.

At the conceptual/math level, why can't I use both the Large Displacement option and the Inertia Relief option with the default FFEPlus solver?


texts: Transporting water uphill at the highest efficiency possible?

texts:
I have a passing interest in water desalination projects. One of the challenges of desalination is simply moving the water from the ocean to the desalination plant. Typically the plant is built above the height of sea level, possibly by tens to hundreds of meters.

Is there a highly efficient mechanical method already devised, to use the weight of the waste water returning to the ocean, to lift more supply water to the desalination plant?

Since purified water is removed by the desalination plant, the brackish return water will be slightly lower in volume than the supply, and there will be losses from viscous drag in the pipes, so there's not a huge amount of energy recovery available.

But it seems like some useful percentage of energy saving / energy recovery should be possible, using the stored potential energy of the lifted return water, to offset the energy requirements of lifting the supply water.


texts: Diode and transistor have reverse breakdown voltage. Are these devices permanently destroyed under such voltage? Also,  do these devices have breakdown voltage when AC voltage is applied? How much AC voltage and frequency these can tolerate,  say $1V$ at $50$ Hz,  $1V$ at $1$ MHz?


texts: Where is the positive terminal on the laser pointer

texts: I want to connect this to wires , I know where the negative terminal is on this ( the spring) but I can’t figure out where the positive terminal is, I can’t find and answer online anywhere else either.  It’s a blue laser. Please help


texts:
Based on the description of friend I drew this small example of a specific pan-tilt mechanism I'd like more information on, but as I'm not an engineer I don't really know what terms to use and can't seem to find anything.
I think I might have seen it somewhere related to nautical devices once, but I'm not sure.

The system I'm looking for uses two cylinders with a slanted face. Both are able to rotate around their central axis. As part B (top part) is connected to part A (bottom part) at the center of their slanted faces, it moves together with part A but is also able to rotate around it's own axis, combining both their movement and creating a lot of freedom in achievable positions.
See the image below for a 3d impression of the shapes and a 2 schematic of how they rotate (where the dotted line would be their rotational axis).

Any idea what this is called, or what to look for?