texts: Why do cars turn by turning the front wheel?

texts:
Why do we design cars to turn by turning the front wheel?

Wouldn't it better to keep all wheels straight and turn by rotating the wheels on one side of a car more then the wheels on the opposite side of the car, like tank tracks do? That way you can turn even if you are standing still. Why don't cars do this?


texts: Need electrostatic material to attract pet hair

texts: Looking for a durable material you can walk on that will attract pet hair from shoes without sticky or adhesive qualities.  Preferably won’t need active electric current but can consider that.


texts: Correct term for non-countersunk flat hex screw/ bolt?

texts:
There is a type of screw/ bolt that is flat on top so that it's almost flush when fully seated, but it is not counter-sunk, and it usually takes a hex driver (allen key). I see it used on Ikea furniture frequently, and the only pic I could find of it was from an Ikea manual:

Note that it is not counter-sunk so from the side it looks like a 'T'.

Does anyone know what the correct mech eng jargon term for this screw would be? E.g. if I'm telling someone to switch from a pan-head to this type of screw?

Thanks.


texts: Stress analysis for the same configuration but different material

texts:
The same geometry and the same free body diagram. However, if we replace the material from steel to glass, for example. How does that influence the analysis?

Two things I think are
1. steel is ductile and glass is brittle. This means the cross section when it fails will be different.
2. glass has lower yield stress, which means it is much easier to fail.

Is there anything else that I omit? Thank you very much.


texts:
When analyzing machines, how to tell if a point that was attached to another part will have only an $x$ or $y$ component or both?

why wouldn't point $B$, $C$ and $A$ have an $x$ component?


texts: Can you create concrete without using water and cement as a binding agent?

texts: I know sulfur concrete is one. Epoxy resin can also be used too. Are there any others?


texts: Linearization of dynamic equations/transfer function in control theory

texts:
I've gone through a control theory course, and after looking back at what we covered and how the subject was taught to us, I still have quite a few questions (which I unfortunately did not ask in class). As such, I thought I'd ask a few of them here, as separate posts, in order to clear up a few points that I don't understand.

Why do we linearize our dynamic equations/transfer functions when doing classical and state-space control? Is this only to allow us to be able to analyse stability and do initial specification design (rise time, overshoot etc.), where we know that the real nonlinear system won't actually act exactly in the above manner? I would have thought that since we'll generally be dealing with nonlinear systems in the real-world, it would be better to test our control implementation on a model that more closely resembles our real system.


texts: Simple beam deflection of cantilever beam

texts:
Recently I had need to prove the beam deflection equation for a simple cantilever beam with a point load at the end. The equation would be in reference to the Euler-Bernoulli theory taught in most basic engineering undergraduate courses. The only caveat is to not use "I" at any point in the derivation, but rather use basic concepts of force, moment, and some conceptual ingenuity to build the equation. The derivation would be specifically to find the angle ($\theta$) that is the result of the intersection of lines projecting from the two beam faces post-deflection. Another starting assumption would be a rectangular beam face.

My problem is that every time I derive the equation, I come out 2x too large. My initial equation is as follows:

$$2\int_0^{h/2} \frac{(r_i + h/2 + y)\theta - l_o}{l_o} (E) (y) (z) dy = Wl_o$$

This simplifies to:

$$\frac{(2)(E) (z)(\theta)}{l_o}\int_0^{h/2} y^2 dy = Wl_o$$

Ultimately leading to:

$$\frac{(E) (z)(h^3)(\theta)}{12l_o}= Wl_o$$

$$ \theta = \frac{12W{l_o}^2}{Ezh^3}$$

As you can see, I come up with an answer that is twice as large as (what I believe to be) the correct answer, and I can't seem to reconcile where I lost a 2.

My thought process behind the initial equation:

The initial fraction represents the strain
E represents the Elastic Modulus (which needs to be multiplied against the strain to get a force/area (pressure point))
For each pressure point you need to multiply by a distance to get the moment (I chose the center axis)
To account for the depth of the beam, multiply by $z$
Integration from $0$ to $h/2$ is necessary to sum the moment from center axis to top of beam
The $2$ represents the bottom half of the face of the beam that is equal in moment to the top half (so double the top half)
The $W*l_o$ represents the total moment being accounted for

With all that said, I've racked my brain and can't seem to find the discrepancy. Hopefully it's not a stupid mistake.. Thanks!

Note: This is a X-Post from physics SE.


texts: Why does corrosion take place at certain stressed regions?

texts: Why does certain parts of metal show more corrosion at the place where there is high dislocation density in comparison to the place where the dislocation density is less? I do sincerely feel that this is particularly because of the fact that the activity is less in that particular localized region where the corrosion is taking place. I think the situation is similar where grain boundaries act as stressed region but what has this to do with the activity. A detailed answer to the above situation will most certainly be welcome.


texts: Hydraulic System design help/ directional valves

texts:
Default Hydraulic solenoid valve issue
Hello all,

I'm having a weird issue with some solenoid valves in a simple hydraulic circuit, let me try and describe the situation as best as I could..

So coming out of a 2 station manifold, I have 2, 4 way, spring return, center drain valves. 120VAC, controlled through relay outputs by a PLC. Each valve controls a set of cylinders, A position down, B position up. Wired up such that 1 leg of each coil jumped together to my 120VAC control, the other 4 legs to their corresponding PLC output.

Initially, I had valves with a center position, A&B drain to T, P blocked. Everything worked correctly from a controls standpoint, only problem was when both valves were "off", I was holding at full pressure (~1700 psi)and building up alot of heat.

So I swapped out the valves for center position, A to B blocked, P drain to T. Wired up exactly the same as before. Now when I actuate, lets say, valve 1, side A, nothing happens...until I actuate valve 2 side A, then cylinder on valve 1 actuates, as well as the cylinder on valve 2. Electrically everything is right when I check with a meter, program is running as it should as well. So that leads me to believe that somethings going on hydraulically.

Anyone have any idea whats going on? It seems like when I have one valve, P going to A and the other "off" (P to T) that I might have to much pressure going to tank, preventing B to T thus keeping my cylinder from moving?

Let's assume that's the issue, how can I modify my design to remedy the problem? Im thinking, change from one, 2 station manifold to 2, independent station blocks and add check valves to the T outputs to prevent pressure from backing into the T line and preventing the oil from draining from the exhaust of the cylinder.

.
.
.
.
SOLVED!!!!

A "dump" or relief valve was added to the circuit, right before the solenoid manifold, plumbed into the tank line, right before the radiator. In the instances when the pump is running, but the machine/solenoid valves are not operating, the dump valve is opened, draining all pressure to tank through radiator.


texts: How do I connect a plate to a D-cut shaft?

texts:
i'm trying to connect a D-cut shaft to a plate for transmission of torque

This is the motor that i am using with a 'diameter' of 4.5+/-.1mm

My first question is whether I can use 5mm circular universal mounting hub like this to do so?

Secondly, i have access to a a laser printer. Would you recommend making a mounting hub similar to the one shown above but with a D-Cut hole? It has a precision of .2mm, so along with the uncertainty in the shaft of 0.1mm, I guess I would have to make the 'hole' 4.8mm. Would this potential difference in size mean that the torque may not be transmitted efficiently?


texts:
What kind of simplified structural system would a Leonardo bridge use?

I've tried approximating the system to a simple statically determined beam (see below) but our calculations did not give any realistic results. I believe it is due to a negligence of the potential strain in each beam. Maybe using a Spring Load Constant combined with nodes would help?

A Leonardo bridge is a bridge constructed without any kind of binding, but just using uniform length pieces of Wood. It can be constructed in this manner:

My own approximation is rough but each of the connections cannot be considered nodes because none of the pieces are loose or movable.

P.S. It would greatly simplify my calculations if any answers would consider a statically determined system even if it is a simplification.


texts: Calculate max. pressure of liquid in motion

texts:
Let's say I have a fish tank with a total volume of 0.25m3 (100x50x50cm) filled with 160l of water. There's no lid and the thing is placed in a room with sea level atmospheric pressure. The whole thing hasn't been moved for a while so the water is absolutely calm.

Now, if I were to lift the tank by 3cm in a seesaw motion in order for the water to start flowing and forming a wave, how would I go about calculating the maximum pressure the water puts on the walls?

Of course I'd wait for a fixed amount of time before lifting the other side of the tank so the wave stays the same in height.

I think I could do the calculations myself but I have no idea where to start or even where to look for a hint (piston pressure? mass inertia?
Bernoulli's equation?).

The reason I need this (or at least I think so) is to calculate the wall thickness. It's basically like a wave motion machine, but open and filled with water: Photo


texts: What is smallest distance you can reliably move an object?

texts:
I am trying to design a science experiment involving lasers and want to know if what I am planning to build it technically feasible.

Part of the experiment requires that I make tiny nanometer changes to the apparatus in order to lengthen the time it takes for a beam of light to travel a particular distance.  I need to be able to control the distance very accurately because I have to make calculations based on how far the light is travelling.

I'm guessing the weight of the apparatus is roughly a kilogram.  What's the smallest reliable distance I can move the apparatus with the specifications I have?


texts:
Question from a validation beginner in the pharmaceutical industry.

What are the common approaches to start writing validation protocols (esp. IQ,  OQ, PQ)?
What are the common approaches to start executing validation protocols?


texts: What is the longevity of Delrin rollers on aluminum linear rail?

texts:
I am in the process of selecting a linear rail system for a 5ft x 10ft cnc laser cutter. Delrin polymer rollers on 2 inch square extruded aluminum tube is an economically attractive solution. I have had success with them on a 3d printer, but I am not sure how well they will handle higher speeds (2m/s) and 12hr per day operation.

The environment is reasonably dust free, but not a clean room. I suspect the erosion of the Delrin over time may cause tolerance issues.

What are some successful implementations of delrin or other plastic rollers in an commercial/industrial setting? Will the plastic rollers typically outlive the bearings?


texts: How does power generation (hydro, wind etc...) account for variable power consumption?

texts:
I know in a power distribution system, the power is generated (from a dam or turbine or something) and consumed immediately.

But the power consumed is variable. So how does the generation system take that into account.

For example what happens to the hydro dam turbines (or wind turbines etc) when I turn my light off or unplug my laptop charger?


texts: How to determine whether a validation study produces acceptable results?

texts:
I have a method developed to predict results of a signal that outputs an root mean squared error (RMSE) for each subject. Combining all 40 subjects, I get a mean RMSE of 5.5 with a standard deviation of 2.8. This is comparable to previous literature.

Now I did a validation study using 5 subjects and obtained a mean RMSE of 12.4 with a standard deviation of 4.4.

To me these seem drastically different and I would not be able to conclude that the validation is good, but I want a more quantitative way to describe that. How would I go about this?


texts: shearing force distribution in a trapezoid

texts: I need help figuring the distribution of a horizontal shearing force in an elastic solid trapezoid. When force $F_1$ is applied to all the top surface of the trapezoid, at equilibrium, is the force in all horizontal layers of the solid the same? That is $F_1=F_2=F_3=F_4$? Or is the shear stress the same and the force varies between layers?


texts:
I am currently designing a tennis ball launcher. I am looking to use the friction wheel approach, where you have the ball passing through 2 spinning wheels and being launched by the frictional force. It needs to launch the ball up to 20 meters. So, for now, I am using RS555 Motor - 12V motor for both of the wheels in my design.
I believe it is a brushed DC motor. I want to be able to control the speed of the motor with a knob or switch on the side of the design. However, I am admittedly lacking in my knowledge of motors and motor components. What components do I need, aside from the two motors themselves, to operate the motors this way, so that I may incorporate them into my design?
And if I decided to not use variable speeds and just want the motors to operate at a constant speed, what components would I need?


texts: Can a 3018 or 1610 CNC router cut aluminum (foil)?

texts:
I'm wondering if anyone has any experience cutting aluminum foil on a very cheap CNC or laser cutter. I have a lot of 3d printers but haven't yet purchased a CNC router.

I am talking about aluminum foil about as thick as Reynold's wrap (brand named aluminum foil). So, that's about 0.2mm thick.

I have another use case where I may want to cut an aluminum sheet that is about 1.0mm tall. Do you think it would be able to cut that, in multiple passes even?

To what extend can a cheap CNC router cut aluminum?


texts: Can I mig weld to my skateboard truck? How can I test if it's weldable?

texts:
I have this skateboard truck for my off-road skateboard. I want to mig weld a piece of aluminum to it to mount a motor. How would I test if it is something I can weld to with a MIG welder? I think it is aluminum, how can I be sure?

From what I understand

if magnets don't stick to it, it is aluminum.
if I test for continuity with my multimeter and I don't have continuity, it is probably anodized.
if it were polished it would be very shiny and probably reflect light.

How do tell if it is in fact annodized, and if so, what do I need in order to weld through it? Do I sand it down? I was going to use a flux core mig welder.

For reflection

Also here is the inside where they have an existing weld.


texts: Please excuse my ignorance in advance, (I'm in cs not EE), I am trying to figure out how can I get the distance from a car to a wall, what form of technology could I use IR sensors, ultrasound, etc.(that is the most cost effective and easy to use), when its all said and done I just want it to send a numerical value of the distance from the car to the wall.


texts: Why does tensile testing in thin films (ASTM D882) require a non-dogboned sample?

texts:
The ASTM dicates a plain rectangular shape.  I understand that the material necks pretty quickly but I frequently get breaks in the grips, particularly with films of thickness less than 0.002."

Dog bone samples seem as though they would help, so why not use those?


texts: Can I use a wooden flat screw head with a washer to mimick a pan head screw?

texts:
For example - I am installing a fold up table from Ikea, it needs to hang from the wall, as shown below.

It explicitly says to use pan head instead of flat screw heads like shown in the picture, I would drill into hollow concrete and will use nylon anchors but my question is, would a washer on a flat screw head be a hack here to do the job of the pan head screw?


texts: Could a single person build a single modern computer from scratch

texts:
By “scratch” I mean, if someone with all the knowledge needed were put in the middle of a plot of land containing all the BASE COMPONENTS (e.g. iron, copper, whatever other materials you would need) needed to build a computer, would they be able to feasibly create a modern computer (such as your average desktop pc) by themselves within their lifetime?

Disclaimer: I haven’t seen this specific question asked anywhere so not sure if this is the right topic to be posting in. Just took my best guess.


texts:
I have a small machine shop and need to size a beam for a gantry crane. The design is a 4 post fixed design with 2 horizontal beams running parallel across the shop ends with 1 beam to be mounted perpendicular on trolleys on top of the two parallels making a crane that can traverse x and y travel with an electric hoist rasing and lowering loads.
The span is approximately 28 feet and the biggest hoist I have is a mere 1 ton but would like to size it so that I have 3000-4000lbs load capacity. Also consider that the x and y axis trolleys are not motorized so a small dynamic/torsional load will be imparted in the x and y when the payload is pulled around.
I'm thinking a wide flange 12*45 would be a decent size. I'm unsure though if in beam calculators they account for the weight of the beam or if it is just the payload. With a centered load and 4000lbs the deflection shows .311" over 28 feet which seems reasonable enough if I understand what I'm looking at.
I'm thinking I'm looking for a moment of inertia in the x axis if the beam is standing in the traditional direction. I'm also not too clear on deflection limitations on steel.
Thanks for the help.


texts:
I need some assistance understanding moments of inertia. I am doing some review for an upcoming exam, however I am slightly stumped by this question. I have already tried googling "moments of inertia" to try and understand the concept better, but I am having issues knowing when to apply which formulas.

I have attached my specific question and the "answer" to the question, hopefully someone can help me understand how to get the answer.

Two identical slender rods of length l and mass m are linked together at 90deg, as shown in figure Q4a (image attached), to form a link in a mechanism. Point B is midway between A and C, and points B, D, E, F and G are equally spaced along the lower link.

i) Determine the position of the center of gravity of the link

ii) Find the moment of inertia of the link about the point B

iii) Find the moment of inertia of the link about the point D

iv) Find the radius of gyration about the point G

ANSWERS:

i) Center of gravity is at D

ii) IB=(5/12)ml2 kg m2

iii) ID=(7/24)ml2 kg m2

iv) k= sqrt(17/24) l m

My attempts

i)

I know inherently that the centre of gravity is at D. How do i prove it mathematically?

ii)

I get the moment of inertial about B like so:

Ib = (ml2)/3 + ((ml2/3) - (ml2)/4)

But i don't understand why I am supposed to subtract. Is it because the centre of gravity is l/2 below B?

iii)

For Id I get the answer by doing:

Id = ((ml2)/3 - (ml2)/4) + ((ml2)/(3*16)) + (9ml2)/(16*3)

Why do I subtract (ml2)/4) if that rod is above D?

iv)

I'm trying to use IG to find the radius of gyration:

So for IG

Ig = (7/24)ml2 - ml2

Here I am using the parallel axis theorem, but why do I subtract the (md2) of the AC rod from the Moment of inertia about D?


texts: Bending a concave sheet metal lip in AutoDesk Inventor

texts: I am trying to bend this sheet metal concave lip inside the electrical box. I also need the top of the bent part below the top edge of the outside of the box.


texts: Can a sleeve bearing adapter be used with a plain bronze bearing?

texts:
I am looking for a replacement bearing for an old lathe.  The lathe spindle assemble features a collet-like bronze bearing with a nut for tightening the inner diameter.

Unfortunately, I cannot find this style bearing at the required size.  Is it possible to use a bearing adapter sleeve inside a plain bronze bearing?

If not, are there any suitable alternatives that would allow me to reduce shaft runout?


texts:
I'm looking for a low-power weight sensor which can withstand impacts of up to 1000 pounds. Is there a go-to supplier or brand for this sort of product?
I want it to give its output digitally; my end goal is to have it implanted in a punching dummy and send data to a Raspberry Pi.

Thank you.


texts: Reverse vs Drive When Slipping Backwards

texts:
I was trying to drive up an icy hill with a front-wheel-drive car (2006 Honda Civic Hybrid) when the front tires lost traction and the car started to slide backwards. The car then easily spun sideways as it slid backwards making it veer left/right and I nearly hit a telephone pole.

I repeated this a few times hoping to get up the hill. It seemed like I had much better control of the car during the backwards slide if I shifted the car into reverse (instead of drive) the moment I lost traction. In reverse, it didn't seem like the car would spin sideways. In these "Reverse vs Drive Experiments", I think I was sliding backwards at about the same speed (just "riding the brake" and not touching the accelerator pedal), but the reverse mode still seemed much more effective at keeping my car straight (while drive mode seemed to cause a spin-out with more random left/right motion).

My conclusion is that I am much safer changing to reverse mode if I start sliding backwards. Is this expected?


texts: Understanding AutoCAD plugin files by Example

texts:
I am interested in developing an AutoCAD plugin and am trying to understand the relationships between several different types of AutoCAD plugin files:

Managed DLLs that ship with AutoCAD plugins
ARX files that ship with AutoCAD plugins
CUIX files that ship with AutoCAD plugins

From what I can tell these three files are all inter-related and work together to initialize and load a plugin, I'm just not seeing the forest through the trees as to what information each file type contains, which files loads or depends on the others, etc.

It sounds like a plugin's core functionality is supposed to go inside the ARX file, and written in C++ and compiled for the native/target platform.

It also sounds like, at startup, AutoCAD loads its plugin DLLs, which are all managed .NET libraries (typically written in C#), and in turn they invoke their native/compiled respective ARX files. As to where the CUIX file comes into play, I still have no idea.

Can anyone help explain the relationships & dependencies of these files, and what types of code/logic/data goes inside of them? Thanks in advance!


texts: How to create Embedded System Program from Scratch using Keil µVision?

texts:
I have been learning the program embedded systems using Keil µVision 4.7 free version from Mentor graphic. So far all the learning has be using projects that have been already pre-defined. This has worked well so far. I would like to take the next step. Below are some of the several tutorial that I have tried with out much success.

Creating Applications using Keil µVision IDE from Mentor Graphic
Create a new project using Keil uVision4 for STM32 (tutorial)
Getting Started with Keil uVision

What the minimum step to create a new an Embedded System project using Kiel µVision (Including defining the micro controller, and even setting up the debugger) so issues describe below are avoided?


texts:
It's my first time posting on this specific forum. I hope I'm doing this right.

I am currently modeling fire spreading through different buildings via FDS, but I lack the properties of the materials modeled, such as heat of combustion and heat of vaporization. I've searched the internet for days and some information is still missing. And I'm not sure what to do.

Does any of you happen to know where I can find an extended combustion properties of materials table?

Thank you for your time.


texts: How to size a rectangular steel tube to hold certain weight?

texts:
I would like to build a shelf (1m width and 0.5m depth) using only four rectangular steel tubes on for legs.
Each legs are at the end of the rectangular tube.
I would like to put 500kg on the tubes, which are equally distributed.
How can I choose the width, height and wall thickness to ensure that the steel tubes are within a certain deflection?


texts: How to minimize temperature increase caused by compression of a cryogenic liquid in a multistage high pressure turbopump?

texts:
The cryogenic fuel I'm using is methane at 100 K and 300,000 Pa.

Based on my calculations, after compression, the pressure is 55 MPa and using the ideal gas equation the temperature is approx. 800 K.

I need to keep the methane at a temperature of 300 K - 600 K preferably as close to 300 K as possible.

I am after any designs or solutions to keep the temperature low, like regenerative cooling, or is that just ridiculous?

The application is for a rocket, temperatures in the vicinity will be high.


texts: Calculate the force when given the moment

texts:
I'm not sure how to calculate force $P$ when the moment is a given with the force $P$ at an angle.

I'm also having trouble breaking the moment into the $x$ and $y$ components.


texts: Need Help to Remove Sway from Steel Post + Glass Panels

texts:
I have spanned ~15' with 2x 10mm tempered glass panels.  They're connected in the middle with a 1.5" x 1.5" 16-gauge, 316 stainless steel post filled with concrete.  This post has a 316 base welded on and this is securely bolted to structure below the floor.  My spans of 88" are well within the specs of both the glass and the glass clamps, per their respective manufacturers.  You can see the setup in this photo:

The "base" footer on the post is ornamental only (shown with the green arrow).  I did not want to introduce any more holes into my waterproofing, so I epoxied some screw heads on it to appear functional.  But, in reality, it's just sitting there.  Either way, the base of the post is solid and cannot be moved.  A 9-layer waterproofing was then installed on top of the post's base.

The other ends of these glass panels are into structural elements of the house.  The one end is into wood studs, and the other end is into an 11-gauge 316 post, again filled with concrete, that is attached to structure at the top and the bottom.  Both ends are holding solid.

The glass panels have already survived a 60mph wind gust storm without any issues.  I was watching it through the window and I couldn't see it move at all.  So, I'm happy about that.  Also, if I lean on the pole away from the house, it does not budge.  Same thing if I pull on it towards the house.  It's completely sturdy and does not move.  The problem starts if I start moving the top of the pole back-and-forth (shown with the blue arrow in the first picture), away and then towards the house.  Just moderate pressure from my hand forward and backwards will start the post and both glass panels to sway (swing, vibrate, undulate) back-and-forth.  This is what I'd like to reduce and/or eliminate.

I've come up with some ideas on how to tackle this problem, and I've even discounted one idea.

Since the bottom of the post is stable and does not sway, I have to assume the sway is from the deflection of the tube steel.  So, I considered a simple, straight piece of 1/4" or 3/8" flat bar steel (piece A in red below), sistered to the post at the top and bottom.  My rationale here is that since the bottom is sturdy and the flat bar steel will provide rigidity and strength and will not deform, that this flat bar would provide strength to the post.
Again in thinking this sway or vibration is caused by the metal bending away from the base, I wanted to add additional support from the structure of the house.  Since this is a view-facing balcony, I want to block the view as little as possible, so I came up with the following cane-like design that would be made of flat bar steel and bolt into the post near the top, and then bolt into the side of the house (piece B in orange below).  The strength of the flat bar should then remove the motion of the post, like a flying buttress.  This allows me to add structure without puncturing the floor's waterproofing.  The post and glass is about 1-1/2" from the edge of the balcony.
Tear this all up and use an 11-gauge post.  Obviously this is my last resort.
Do nothing and live with the sway.
Do something else.

I also considered that the post was creating a wave effect between the glass panels.  I then considered a stabilizer between the glass panels, but I tested this with a piece of flat bar steel that I clamped onto both pieces of glass.  This did nothing.

Can you please let me know which option, 1-5, they think I should choose and why?  Thanks!


texts: How do elevators stop at the exact landing spot when reaching a particular floor?

texts:
The floor the elevator moves to, is controlled by the lift PLC with all the algorithms developed over the years, and that I understand well. What I am not able to understand is how does the lift stop at the exact landing position at a particular floor, neither too high nor too low, but on the same level as the elevator landing on the floor.

I understand that with modern Variable Frequency motor drive controllers and sensors this is not an unachievable task, but how did they do this in the olden days of relays? And even in today where the speed of the driving AC motor in many current elevator systems, is controlled through pole-switching? Do they use some special PID algorithm or some variant of that?


texts: Best way to make a sealed container for a long term storage of a USB drive?

texts:
I'm unsure if this is the correct community, so feel free to move it if you feel it's in the wrong area.

I'm trying to develop a water-tight/sealed box for a backup flash drive. The idea is to make something that is weatherproof enough so I can keep the box outside or in my basement for years, and if I ever need to retrieve the data, I can cut the box open and retrieve the USB stick. This would need to completely resist water/moisture and withstand temperature changes between say -40 C to 40 C without it breaking down.

Here is the concept I have so far:

First layer: Put USB stick into air-tight plastic container. Could be something cheap like a sealable zip-lock bag to protect from:
Second layer: fill a small box - not much larger than the stick - with a polymer sealant/caulk that will eventually solidify, fitting the form of the box.

My question is, what is the best material can I use for layer #2?


texts: How to convert ton force to pound force, manual pellet press

texts:
I'm looking into manual pellet presses and the one in mind lists a 12T clamping force and then goes on to detail that the analogue gauge goes from 0- 24,000 lbs. Are these two numbers related? When I try to convert T to lbs I usually get 26,880 lbs for 12T.

Thanks!


texts: Do pressurised cans still pose a risk to bursting in normal conditions, but after being exposed to heat?

texts:
We're planning on shipping some items from the US to Australia as you cannot get them here, that being:

https://www.chewy.com/sentry-stop-that-noise-pheromone-dog/dp/56486

I have been in contact with a freight forwarder who can ship them to Australia, but obviously they will need to be shipped as a hazmat item and go inside a particular sized box and be shipped by FedEx or DHL.

Now, as I understand it, the reason these are classified as hazmat is because  of the chance of bursting as well as being flammable.

As per the link above:

  Contents under pressure. Do not puncture or incinerate container. Do not set on stove or radiator, expose to heat or store at temperatures above 120°F (49°C), as container may burst.

I have no idea, but I assume they wouldn't be exposed to high temperatures such as that during shipping, but my question is...

Assuming we got them ok and they didn't burst, do pressurised cans such as these still pose a risk to bursting in "normal" conditions AFTER they have been exposed to high heat? Such as if they had been exposed to high heat during shipping, but we got them ok, would they still pose a risk to us with the possibility of bursting?

The manufacturer provides a Material Safety Data Sheet on their website, which you have to email them or register to get it sent to you, but if it's of any interest you can download it here from MediaFire.

Alternatively you can find instructions to download it via their site - see under "PRODUCT SAFETY INFORMATION".

If you don't want to download anything then you can see screenshots of the document I uploaded to an Imgur gallery here: https://imgur.com/a/gXKxVeE

Note though, the above data sheet was provided via their site that shows their old packaging, the link from Chewy above shows their new packaging, as far as I know the packaging is the only thing that has changed.


texts: What do you call the steel property that reduces the likelihood of shattering?

texts: What is the property of not shattering, in for example a brisant explosion, called? And what kind of steel would I want that has this property?


texts:
Can I ask about MATLAB code for simulating the LED and how to convert the input signal (modulated signal) into the optical signal (signal out from the LED)?
I need a hint or help, please.


texts:
I am an economist, so please keep replies simple ;)
I am searching for the relationship between heat rate and capacity for gas-fired power plants. Here is what I refer to as heat rate, i.e. the inverse of efficiency: http://en.wikipedia.org/wiki/Heat_rate_(efficiency)

From an IEA publication I got the following approximate relationship (for a CCGT plant):

maximum heat rate = 1.1 * minimum heat rate

Maximum heat rate holds whenever the power plant is operated at minimum capacity, and

minimum capacity = 0.4*maximum capacity

I'd like to know what the heat rate is when I run the power plant at a medium capacity of let's say:

medium capacity = minimum capacity + (maximum capacity-minimum capacity)/2

So

medium heat rate = ?

Is the relationship linear (i.e. = minimum hr+ (maximum hr-minimum hr)/2) or how would you estimate the heat rate here?


texts:
I have a Wemo Smart WiFi Smart Dimmer with me that can control CFL, Incandescent and LED lights. (https://www.belkin.com/us/p/P-F7C059/).

I am curious to know how one device can handle all type of bulbs.

As I understand that,
In order to dim the light, usually, Triac/Solid State switches are used. They are generally called phase-cut dimmers. They can be either leading edge, trailing edge or universal dimmers. These usually go well with CFL and Incandescent lights. These dimmers circuits accept 230V 50Hz input for operation.

Now, if I want to control a LED light, I probably will need a LED driver. These LED drivers work on PWM on either constant voltage or constant current.

So Wemo Smart dimmer works for all kinds of the bulb, they will have to have a LED driver inbuilt and an AC/DC converter to convert the 230V AC to DC for LED lights.

Now, I am not sure If I am right.
What do you think?

P.S - A shout out to the explanation Rod Elliott (http://sound.whsites.net/lamps/dimmers.html). It's a very well written piece of information on LED dimmers.

Edit:

I think I had a bit of misunderstanding. I think that the Wemo Smart dimmer can only control LED bulbs that are rated 230V. Bulbs like these( https://www.philips.co.id/c-p/8718696485583/led-bulb). And then you will need to a LED driver to control LED bulbs like MR16 LED bulbs (http://www.lighting.philips.com/main/prof/led-lamps-and-tubes/led-spots/mr16-gu10-par16). They are rated 12V...24V DC-DC with either constant current or constant voltage.

But again I want to make sure that my direction of thinking is right. I am no expert on LED lightning.


texts:
I am new to Ansys Fluent and am trying to model heat transfer through a system of fins. The analysis is in 3D.

I have set the Energy Equation as ON. The problem is that when I set heat loss by convection in the fins, a heat transfer coefficient is demanded by the software. However I am looking to evaluate the overall heat transfer coefficient of the fin system in the first place. Shouldn't the model be completely solved simply by knowing the material properties of the fin and the fluid and the velocity and temperature of fluid at the inlet?


texts: How can I develope a water loop cooler system sustaining with liquid nitrogen?

texts: Water will be circulated in the water pipe and liquid nitrogen tanks heat going to cool the water pipe,by the way to the water too. And fan is going to blow this cold air and heat is going to be decreased. Is it possible ?


texts: Is there an standard description for deformation at each point on a body?

texts:
I'm trying to come up with a way to describe deformation on a body at each point on that body. My problem can be expressed and solved in two dimensions. Given two triangles, one being the initial shape, the other being the initial shape transformed arbitrarily :

It's evident by looking at this that points along the left edge are now more distant to each other, points along the right edge are closer, points along the bottom edge have the same distance as before, and any point inside that triangle is blend of those three states. Is there any engineering standard to describe this, for any position on the body? I've looked at stress and strain, but I'm not sure if either describe what I want. In the end, I'm trying to find a value (or possibly two? Maybe a vector?) that describe, for a tiny area, if that area is compressed or stretched after the transformation.

PS.: I'm not a mechanical engineer if that wasn't already obvious. :)

Thanks!


texts: How do those "dipole-shaped" weights attached to sections of electrical power lines work?

texts:
I see these frequently on tall power lines like the one in the image below, sometimes a single one at each end, sometimes pairs as are shown here. Sometimes on one side of the tower but not the other.

I vaguely remember reading once that they are used to reduce swinging in high winds, and where I live typhoons come regularly.

What are these called?
Are they used to reduce swinging in high winds?
How do they do this?
When is a pair used instead of a single; why not just use a bigger one?

From Wired original: https://i.stack.imgur.com/pLy9u.jpg


texts: How to reconfigure a control box unit for an SCN5 actuator

texts:
An image of the actuator is below. I have a setup that was given to me where there is two configurations, namely 50mm travel and back, and 75mm travel and back to home position. There are two switches PC1 and PC2 which control the two programs via the CSRT switch.

Now I would like to extend the system to 4 program, example

home, 100mm travel, home
home, 75mm travel, home
home, 50mm travel, home
home, 25mm travel, home

To achieve this I plan to add 2 more switches, PC4, and PC8. After I add the switches my control box will look something like the following.

Below is an example wiring diagram.

Below is an example of the programming interface.

Below is an image of the electrical wiring interface.

Question: How do I wire the PC1, PC2, PC4 and PC8 so I can independently control 4 settings? Only 1 switched can be ON for a program. The other 3 switches have to be closed.
I am also open to hearing alternate solutions.
Here is the link for the vendor who sells the SCN5 actuator in question.
https://www.miraiintertech.com/home/scn5.php


texts:
Consider a series LCR circuit. Once power source is removed, the electrical energy oscillates for some time before damping out completely. I want a LCR circuit such that 1) it has high resonance frequency , say 1 GHz and 2) it oscillates for some time say 1 min.

Consider following numbers. To achieve 1 GHz, L and C must be very low. Let C=1 pF and L=25nH. This gives us resonance frequency around 1 GHz. At such high frequency the inductor wire will pose some resistance, let us assume R=0.001 Ohm, even though it is likely to be more. The attenuation factor $\alpha=R/2L$ is going to be high, which means the oscillations even if under-damped, will not sustain even for a second. Clearly there is a trade-off between high frequency and longer oscillation.

Is there a way to achieve both? It is ok even it is achieved without removing the power source, however, note that the voltage source is 10-100KV DC.
Just keeping the LCR connected to the power source will not result in oscillations, in my understabnding.


texts:
I am constructing an autonomous, unmanned boat for voyages of several months.  Traditional autopilots use a linear actuator to move the tiller but require several adjustments per minute. They will consume a lot of electricity and probably wear out mid-voyage.  We are looking at wind-vane designs to steer the boat.  Wind-vanes are able to steer for great distances without adjustment.  The boat will be approx. 5m in length.

In the image below, the 'Course Setting' is done by manually rotating the wind-vane and dropping a pin to hold this position of the two discs.  We need a way to rotate the vane fairly precisely and then lock it into position.  We are using 12V DC.  After it is locked, it should draw no power.

As you can see, the current design (not our drawing) would have any electromechanical mechanism hanging off of the end of the boat and attached to the rod of the trim tab.

Is there anything we can use to turn and then lock the wind vane in place?  Preferably something that could be proofed against wind and water.


texts:
Im working on a project that has gearing system integrated. From my simulation results im dealing with a relatively small amount of input force at the gearbox and would like to know if the force would be transmitted through the gears which i chose at all. I cant seem to find any consistent or not so complicated information about how to calculate the static friction to overcome before motion. Can anyone point me in the right direction? A simplified estimate or model will do. I would like information on spur and bevel gears. Thanks
Edit.
I added a pic as per request.


texts: What is the reason for a reduction in entropy in a compressor

texts:
I was under the impression that the entropy reduction in a system only works with either mass or heat transfer.

While I was researching intercooling of compressors I stumbled across a peculiar sketch (Figure 8-46 from Çengel: Introduction to Thermodynamics and Heat Transfer). I cross-checked with my thermodynamics textbook (Figure 9-43 from Çengel: Thermodynamics - An Engineering Approach).

The entropy gets smaller throughout the complete compression process. While I do understand that it gets smaller when cooled I do not understand why the entropy reduces prior and after the intercooling.
Figure 9-43 shows the compression as isentropic (which is often done to simplify the analysis).

What am I missing? The only idea would be a heat-loss during the compression. I then realised that a bit later in the book a similar graph shown in Fig. 7-34:

What is the reason for a reduction in entropy other that heat-loss in these cases?
Is it maybe a didactic choice?


texts:
I was wondering about the ethics of an interviewer asking to see your design notebooks in an interview.

First off, I'm not sure if it's even legal for someone to ask that, since many of the designs I have are covered by (Non disclosure Agreements) NDA'S  with various companies which the interviewer is not a part of.

Secondly, I'm not sure if the request to review my notes is even ethical?  Your design notebook is basically a screen shot of EVERYTHING you've worked on good, bad, right and wrong asking to see it is almost like asking to see your work email account from another company, in my opinion.

Guidance on this would be appreciated.


texts: How do I determine the pitch/roll stability of a buoy?

texts:
I am designing a loosely-moored spar buoy (large height relative to width), and the equipment on top needs to remain as vertical as possible while floating in the sea, within limitations of buoy cost, size and weight. I have done fundamental buoyancy and stability calculations that demonstrate that the metacentre (M) of the buoy is located above the centre of gravity (G) meaning the buoy is stable.
Stability increases as the metacentric height increases. But how do I know what metacentric height range to aim for?
Is there a more appropriate measure of stability (stability metric) than the metacentric height?
Or do I need to use complex calculations to determine the pitch/roll of the buoy for a given wave height and speed?


texts: I would be grateful if someone could explain me what does the value of zeros of a transfer function tell about the dynamics of the system.


texts: How to make a conductive paint over PDMS?

texts: Conductive paint by conventional technique using gum and graphite powder does not stick to the PDMS surface and comes off once the paint dries. How else can I make a conductive connection over the PDMS surface so that it can stick to it nicely?


texts: Can you help me to interpret technical drawings?

texts:
I'm trying to find out the angle/ length of the oblique line, or the solid angle of the conic part.
This is what I've tried so far:
According to the pythagorus theorem the length of the line is equal to:
$$\sqrt{(50-22)^2+14^2}$$
but obviously this method gives a contradictory results, because as you can read, the line makes a 45° angle with the vertical axis, so its length should be equal to:
$$\sqrt{14^2+14^2}$$
I make somewhere a mistake which I obviously don't see it.
The next question is about the dimension 15 ( marked in red ).
I spend an awful amount of time to figure it out, but still cannot say anything.
At the end I want to know if this is something I'll confront a lot in real life mechanical engineering ? I mean a really confusing old drawings of parts sometimes with wrong/incomplete dimensions ?


texts:
If a jet starts in extreme cold, i.e cold starts, then the jet cannot power the heat exchangers to heat the fuel. Then how do they heat the fuel to start the jets?

Obviously you can't use batteries/inductive heating to heat the fuel. Most batteries don't work at the cold start temperatures (-50c or so). Even if you want to use exothermic chemicals to heat fuel, you need stored power to open valves.

Then how do they do it? Do they just insulate the tank and hope for the best? even if you insulate tank, you need power to pump fuel.

say its a kerosene +oil based jet. or jet fuel A.


texts: Does the ultimate tensile strength of a material have a physical meaning?

texts:
For example, for yield point you can say that it is a point after which the material will have plastic (permanent) deformation. I'm wondering if there is any similar meaning to the tensile strength? And is there any importance to it?
The thing is, whenever we calculate tension of anything (in college), the tension in the material must always be lower than it's yield strength. So it makes me wonder why do we care about ultimate tensile strength?


texts: For an at-grade intersection of multi-lane roads, what are the (dis)advantages of a "turborotonde" or "turboplein" compared to a classical roundabout?

texts:
For an at-grade intersection of multi-lane roads, the "Turborotonde" (Dutch language Wikipedia article) or "Turboplein" (Dutch language wegenwiki article) is an alternative to the multi-lane roundabout:

Source: Juerd, Wikimedia Commons, CC-BY-SA 4.0

Or the larger turboplein:

Source: Rijkswaterstaat / Joop van Houdt, via wegenwiki

Compared to a classic multi-lane roundabout:

Source: Ferdrik, Wikimedia Commons, CC-BY-SA 4.0

For an at-grade intersection of multi-lane roads, what are the (dis)advantages of a "turborotonde" compared to a classical roundabout?  It would appear that the turborotonde should be safer, but it may be that there are disadvantages too.  For example, it appears not (legally) possible to turn around (full circle).  What are other disadvantages compared to a classic roundabout?

See also: Are there any turborotonde / turboplein designs with more than four exits?


texts: Electric flux density outside cylindrical surface?

texts:
What I did is that I draw a Gaussian contour with radius p>a.

The electric flux outside the cylinder is Ps/2

The electric flux inside the cylinder is PL/(2*pi*p)

When I add them it is not the same answer.

What is wrong , can someone show me the step of solving this problem

thank you


texts:
I am currently prototyping a part for a personal project. My CAD design was contracted out and there are some off the shelf parts that I need to order per the design (springs, screws, etc.).

My designer included two types of springs in the BOM:

3ID x 15mm (possibly 3LD??)
5ID x 5mm

I am not sure what the ID (or LD) naming convention means. Could use some help.


texts: In a warmer/sunnier climate, window (or roller shutters) superior to curtains?

texts:
When -on a hot day- the sun is incident on a window covered from the outside by a closed window shutter, the resulting heat is absorbed by the layers of air surrounding the shutter, subsequently circulating upward by convective motion thus drawing in new cooler air from below to cool down the shutter. If in stead a curtain was shut on the inside of the window (window shutter absent in this case), the same heating of the surrounding air occurs, but this time around this air is tapped from the interior atmosphere of the house and thus it screws up the overall insulation of the house's interior conditions from the outside. To (partially) offset this effect, one is forced to pick light-tainted curtains. Even then, it seems to me that in a sunnier climate, curtains are going to shed more particulate matter into the surrounding room and thus adversely affect the air quality?

Q: Is this a legitimate/complete assessment? Have I overlooked something?


texts:
So I have found this equation:

$F_\mathrm{suspension} = Kx + F_\mathrm{damper}V_\mathrm{contact}$

Where:

$K$ = spring stiffness
$x$ = the contact depth of spring(also known as spring compression)
$F_\mathrm{damper}$ = damper strength
$V_\mathrm{contact}$ = the speed at which the spring is compressing/decompressing

My questions are:

Is this accurate equation for calculating car suspension force?
What are the different factors in equations for different types of suspension setups found in multiple cars? This is meant that trucks and old cars use leaf springs while new cars mostly has coil springs, some cars has multiple springs or dampers etc.


texts: How to convert the velocity field to a pressure field for obtaining the sound level?

texts: I am studying jet mixing noise and I am given a velocity field, with $V_x$, $V_y$, $V_z$ in the Cartesian coordinates. I wanted to know if there is a method by which I could find some information relating to the sound level produced from the pressure field.


texts: ANSYS APDL Shape memory effect option of SMA not working

texts:
I am trying to define the material properties of a shape memory alloy material in ANSYS APDL V15. There are material properties for Superelastic materials (SUPE option) and material properties for Shape memory effect materials (MEFF option) depending on the option taken. Even after taking the right option for shape memory effect, the data shown is not the right model.

My code for defining the material with the trigger is as follows:

/PREP7
MP,EX,2,47.2E9
MP,PRXY,2,0.33
TB,SMA,2,1,7,MEFF,,
TBDATA,1,0,315.15,100E6,4.4E6,0.05,2.0E10
TBDATA,7,0

The output windows confirms that I took the memory effect option by saying:

DEFINE DATA TABLE  SMA   FOR MATERIAL     2
Shape Memory Alloys OPTION  MEMORY EFFECT
WITH A MAXIMUM OF  1 TEMPERATURES AND    7 DATA POINTS

However, the material model still displays the material constants as being "SIG-SAS, SIG-FAS, SIG-SSA, SIG-FSA, EPSILON, ALPHA" for a total of 6 constants. These correspond to the SUPE option.

Both the name and number of constants correspond to the Superelastic model and not the Shape memory effect, which I should have triggered using the MEFF option.

Why is this happening? How do I define this material using the constants for the Shape memory effect, rather than the constants for the Superelastic model?


texts: Maximum torque on thin walled aluminium shaft

texts:
I am trying to determine the maximum torque that can be applied to a 6061 Aluminium tube with O.D. = 55 mm and I.D. = 53 mm. The yield strength of 6061 Aluminium I have taken as 55 MPa and using the formula
$$T = \frac{tJ}{r}$$ and the polar moment of inertia of a hollow cylinder
$$J = \pi\frac{D^4 - d^4}{32}$$

This comes out to 247 Nm. I'm highly skeptical of this number as it seems quite absurd that an aluminium tube with a 1 mm thick wall can handle that much torque.

It's been quite a few years since I've done mechanics so I'm sure I'm missing something (or several things).


texts: How does a laser printer write with light on the photosensitive drum?

texts:
I want to understand how a laser printers laser writes on a photosensitive drum. I am trying to understand this process.

  the photosensitive cylinder is illuminated by a laser beam that projects above the negative of the image.

After you illuminate with laser beam what happens exactly on the photosensitive drum? What is this projection?
negative image? Where does this come from?
When the drum receives this laser light, the photosensitive drum material generates a current, voltage? How and what is handled this photosensitive drum variation due to the absorption of light?

I understand the process drum-toner but I don't understand this step well:

  when you want to perform printing, it is loaded with positive electric energy from the corona wire, an electric current thread that runs through it in all its length.


texts: How is the ideal Euler line on a pump curve derived?

texts: This website provides Euler’s equations for turbomachinery and solves a sample problem using velocity triangles. The problem prompt only provides the speed of the pump and the geometry of the pump and the final answer provides a single flow rate and head value. However, for a given pump geometry and speed, the pump can operate at a variety of head and flow rates as can be seen on any plot of a pump curve. So how is the ideal Euler line on a pump curve derived? Are the same equations and velocity triangle method from the link above used, or is there a different method. And why does the analysis in the link only arrive at a single head and flow rate value?


texts: I'm looking to measure and log the surface temperature of lithium ion cells (cylindrical and pouch). I tried using LM35 sensors with an Arduino, but, the drift was too much somehow. Any suggestions on how this system can be improved, as in - use different sensors or change the microcontroller?


texts:
I'm wondering, if you put an air compressor pipe into a micro turbine, lets say something like that attached to a motor, does air that get out of the turbine have the same energy as when it gets in ?

Because i get that the compressor might have to push harder, but the air itself still has to get out of the pipe, basically i don't get why you can't put like 10 of those turbines attached together and somehow get free energy, i know that it's impossible but i don't get why..

Is there a way to calculate the energy of that thing?


texts:
4 beams are supported by the column at one side, another side is jointed together at the intersection. I have assigned UDL of 20 kN/m on all the beams. 2 beams are longer (3m), 2 beams are shorter (2m) . Surprisingly, the BMD of the longer beams is hogging at the middle part , while the BMD of the shorter beams is sagging at th middle. Does it make sense.
Can someone explain this situation ? Why the BMD of the longer beam is hogging at the middle ? There's no column at the middle , how can there's hogging moment at the middle for the longer beam ?
I think the BMD of the shorter beam make sense and the BMD of the longer beam shall be teh same also (pure sagging in the middle and no sagging at all. ) Correct me if I am wrong ..


texts: Reaction forces at R1 and R2 and draw free body diagram


texts: What are the limiting factors on diesel engine compression ratios?

texts:
Higher compression ratios in internal combustion engines generally improve the engine's fuel efficiency. But diesel engines don't seem to go above a ratio of 25 or so. What is the limiting factor for the compression ratio in diesel engines?

(For anyone who's wondering about gasoline engines, there the compression ratio is limited by the undesired auto ignition of the fuel, which does not apply to diesel engines.)


texts: Difference between surface loading rate and surface overflow rate of sedimentation tanks

texts: Can anyone please explain to me the difference between surface loading rate and surface overflow rate when used during the design calculations of sedimentation tanks in water treatment plants?


texts: Thermodynamics, how can i do this with steam?

texts:
I have a problem with thermodynamics.
I have this question:

$q_{12} = ?$ Steam heating in constant volume. $p_1 = 1.76$ bar. Steam quality: $x_1 = 0.7$;  $T_2 = 200$ Celsius.
Where ’1’ is the current state of the steam, and ’2’ is the goal state.
What I need for this task is:

$h_1$, $s_1$, $p_1 = 1.76$ bar, $v_1$, $u_1$
$h”$ $s”$ $p”$ $v”$ $u”$ $t”$ (the line between the liquid-vapor and vapor region)
$h_2$, $s_2$, $p_2$, $v_2$, $t_2 = 200$ Celsius

My question is that how could I calculate this from a steam table? I know that this is isochoric changing, so $v =$ constant, but I couldn’t find any solution on the internet.

Thanks guys! I really appreciate it. It makes me mad for days :)


texts: Design a composite material with good wear resistance and electrical conductivity

texts: For a electrical switching device which opens and closes frequently and forcefully. Would a combination of a soft polymer matrix and a conductive metal fibre be a good choice for this? While polymer in itself is not known for having good wear resistance, since it is opened and closed forcefully, using an elastomer could take the energy from the forceful closing and just deform very shortly. The metal matrix inside is protected and could be the charge carrier. Are my assumptions correct? What other ways are there to achieve what I mentioned?


texts: Modulate a laser's wavelength? What are the inner workings of a laser, and is it possible to change the wavelength mechanically? Are there any lasers that can change wavelength?


texts:
I read the paper "Bilateral Control of Teleoperators with Time Delay",which is written by Robert J. Anderson and Mark W. Spong. In that paper, they defined passivity of an n-port flow as
$\int^\infty_0 F^T (t) v(t) dt \geqslant 0$
$F$ means effort and $v$ means flow.
And they said if a two-port system is passive, the system is stable. They didn't said that directly, but they said an system can be unstable by being nonpassive. They said that without proof, so I want to know why an passive system is stable.


texts: How can I describe cold work and atomic structure?

texts: A copper wire (42 cm x 0.25 cm diameter) twisted to failure did not change its dimensions significantly. How can I visualize or quantify the cold work done (tensile at the exterior, compressive in the interior)? Does it still have a regular crystalline structure, or is it just a bunch of dislocations held together by copper atom chains?


texts:
I have an application (a tube with parts in it) which needs a certain static pressure in it in order to contain a sustainable air flow. Unfortunately the fan I wanted to use in a push-configuration is not able to create this pressure. Thus I thought that I could install another fan with a higher cfm at the end of the tube (in pull-configuration), and thereby increasing the static pressure? Would that be useful, or is there another way to increase the static pressure in the tube?
Schematic is:

Neither F1 or F2 are able to provide the necessary static pressure alone.


texts: Are typical worms and worm gears self-locking?

texts: Does anyone know if typical/common worms and worm gears self-locking (plastic or metal)? Are the self-locking ones specially designed (with specific angles) in order to be self-locking? By self-locking, I mean that the worm gear can't turn the worm but the worm can turn the worm gear. Are they considered "special" worm drives, and thus cost more to make (and thus, less commonly used)?


texts: Current generated by piezoelectric material, say pzt

texts: A piezo material like pzt produces voltage upon mechanical stress application. But how much power it can generate or how much current it can generate as a function of piezo characteristics and force applied?


texts: Is it possible to build a perfectly spherical Prince Rupert's drop?

texts:
Prince Rupert's Drops are glass objects created by dripping molten glass into cold water. While the outside of the drop quickly cools, the inside remains hot for a longer time. When it eventually cools, it shrinks, setting up very large compressive stresses on the surface.

The result is a sort of toughened glass: you can hammer the drop head without damaging it, but a scratch on the tail leads to an explosive disintegration. Check out this video.

So, is it possible to build spherical Prince Rupert's drops? And if so, how?
One example of an application is as a replacement for traditional ball bearing spheres. There will be improvements in wear resistance and maximum loads tolerable, and a glass sphere would cost less anyway.


texts:
I need some sort of a smoke generator for a small wind tunnel. I have been thinking of making a system that pumps smoke fluid trough a small metal tube wand which has a heating coil at the end of it to vaporize the fluid. The same kind of setup is used in some commercial systems, but as they are too expensive I would like to build my own. I have some electronics experience as a hobbyist.

My question is that what kind of an coil should I use? Some sort of soldering iron heating element?

I think a heating element with a hole in the middle would be ideal, but i haven't seen one.


texts:
I have a question that I can't solve.
Coefficient of drag= x,
Coefficient of Lift= y,
it is given that x= 0.015 + 0.05*(y^2), FInd Max Lift to drag ratio

and I know that Lift to drag ratio is L/D= Coefficient of lift/Coefficient of drag. Can anyone tell me how to solve this

Thanks in advance


texts: I am doing mechatronics engineering and i am to choose an elective module. We have the choice of taking up Digital Signal Processing or Power Electronics and Drive. Majority of my friends are taking DSP cause our lecturer says its more useful for mechatronic student. I personally feel that PED has a better application for robotics. Could i get some advice on which is more reasonable for robotics.


texts: Wouldn't placing an inductor instead of a capacitor have the same effect in fans?

texts: A capacitor is kept in the circuit of a fan to overcome the trouble of having torques in both directions. I would like to know if the capacitor could be replaced with an inductor without resulting in any change in operation of the fan ?


texts:
I have a BITZER compressor type 4GE-23Y-40P, with a part winding start option

Nennspannung = nominal voltage = 380-420
Frequ = frequency = 50
Betr. strom = maximal operating current = 43.9
Anlaufstrom = starting current (A(Y) with the first winding, A(YY) second winding) = [A(Y)=97, A(YY)=158]
I am confused about what current should I consider in the sizing of the compressor starter parts (contactor, fuse, circuit breaker, thermal overload relay)?
Thanks in advance


texts: calculate output $y(t)$ from $Y(z)$ having discrete closed loop model with sine input - residue method

texts:
I have closed loop - discrete model. This is how it looks in matlab:

I need to compute analitically output $y(t)$ (same as in the Matlab's scope) having $Y(z)$.
Where
$Y(z)=U(z)*G(z)$
Input is sine wave so Z transform for sine is:
$U(z) = \frac{z\sin(\omega T)}{z^2-2zcos(\omega T)+1}$
and
$G(z) = \frac{G_o(z)}{1+G_o(z)} = \frac{kz^3}{(a+k)z^3+bz^2+cz+d} = \frac{kz^3}{(a+k)(z-z_1)(z-z_2)(z-z_3)}$
Where:
$\omega$, $k$, $a$, $b$, $c$, $d$ - are given parameters.
So:
$Y(z) = \frac{z\sin(\omega T)kz^3}{(z^2-2zcos(\omega T)+1)(a+k)(z-z_2)(z-z_3)(z-z_4)}$
I saw on Wolfram Alpha that roots of $z^2-2zcos(\omega T)+1$
are
$z_0 = cos(\omega T)-isin(\omega T)$
$z_1 = cos(\omega T)+isin(\omega T)$
and rest of roots ($z_2$, $z_3$, $z_4$) I compute using roots function in matlab from $G(z)$.
$z_2 = 0.9889+0.022i$
$z_3 = 0.9889-0.022i$
$z_4 = 0.8784$
The residue method is what I know but other would be good too.
For example:
$res_{z=z_0}=\lim_{z\to z_0}(z-z_0)Y(z)z^{n-1}=\lim_{z\to z_0}\frac{z\sin(\omega T)kz^3z^{n-1}}{(a+k)(z-z_1)(z-z_2)(z-z_3)(z-z_4)}=lim_{z\to z_0}\frac{\sin(\omega T)kz^{n+3}}{(a+k)(z-cos(\omega T)-isin(\omega T))(z-z_2)(z-z_3)(z-z_4)}=\frac{\sin(\omega T)k[cos(\omega T)-isin(\omega T)]^{n+3}}{(a+k)(-2isin(\omega T))(cos(\omega T)-isin(\omega T)-z_2)(cos(\omega T)-isin(\omega T)-z_3)(cos(\omega T)-isin(\omega T)-z_4)}$
$y(t)$ as you know is sum of residues for all poles.
In order to plot graph from my function $y(t)$ I have to get rid of imaginary parts of equation. How can I do this?
Yeah it's boring because it's a homework.


texts: Zeroing a ventilator's volume measurement in the face of drifty sensors

texts:
I'm a software engineer working with http://respira.works to build an open-source ventilator for COVID-19.  Notably, I'm not a controls person or a hardware person, so please forgive me.

Background

One of the things a ventilator needs to do is measure the volume of air in the patient's lungs.  Our ventilator has two venturi flow sensors, one which measures the flow of air going into the patient, and one which measures flow coming out of the patient.  We can then integrate the difference between these two sensors to determine the volume of air in the patient.

In theory, the volume of air in the lungs goes to exactly 0 when the patient finishes exhaling, right before they start their next breath.  In practice of course this might not be the case.

Some of the reasons the integral might not go to 0 are related to the patient.

Not all breaths are exactly the same size, and our zero point is arbitrary.  That is, the point that we declared as 0 isn't actually "zero air in the lungs", and if a patient exhales a lot, they could go below 0.
You can imagine similar situations, like maybe the patient doesn't fully exhale before taking their next breath; this is known as a "stacked breath".

Others are related to the machine itself, and in particular inaccuracies in our flow sensors.  Empirically it seems our flow sensors have two kinds of error.

One kind of sensor error is "white" noise.  Scare quotes because I don't know if it's technically white noise, but it randomly jumps around near a particular average.  This hasn't been a huge problem; we have ample time to take many samples and average this noise away.
The other kind of sensor error is zero-point drift.  That's what this question is primarily about.

What I mean by zero-point drift is: The venturi's pressure-difference (dp) sensor outputs a particular voltage when there is 0 flow.  We are sensitive to this zero value, because ultimately the flow signal is pretty small.  This zero-pressure voltage is usually constant, so we can calibrate it away.  But sometimes it changes.  These changes in zero point can be large, and they happen ~instantaneously.  The machine registers this change as a constant flow.

Description of the problem

OK, that's a lot of background.  Here's the problem I am trying to solve.

I want to show a graph of volume in the patient's lungs over time.  Ideally, this graph should hit zero in between each patient breath, if the patient is breathing "normally".  The graph shouldn't hide clinically-useful information like stacked breaths.  And, in the event of zero-point drift, it should recover quickly and without "too much" distortion of the graph.

Mathematically, how should I do this?

Thoughts so far on a solution

Here's my current thought about how to do this.  Let $v_0, \ldots, v_i$ be a series of observed volumes (before any correction), all of which "should be" zero.  Let $t_1, \ldots, t_i$ be the length of time between $v_{i-1}$ and $v_i$.

We estimate that $$ v_i = v_{i-1} + c_i + t_i \delta_i $$ where

$c_i$ is a constant error.  Usually $c_i \approx 0$.
$\delta_i$ is the error in flow due to zero-point drift (therefore $t_i \delta_i$ is the error in volume caused by flow error).  Usually $\delta_i \approx \delta_{i-1}$.

When I phrase it like this, it seems to me in my naïveté that I have just described a PI controller.  So...is that the answer?  Or is there something else I should be considering here?

Thanks for reading.


texts:
In Ansys workbench is it possible to import parameters with part geometry? Eg. if I create part or assembly in Creo or SolidWorks and define parameters for this geometry, can I export parameters with geometry and import and use those parameters in Ansys workbench (structural analysis)? Can you describe process?
If you answer question please also write which version of ansys and what program can be used in such way.


texts: Choosing significant figures when dealing with a wide range of values

texts:
In a calculation I have received a number of values in the range $1e4-1e6$. Now I would like to display the values with 3 significant figures according to the rules of using significant figures. But this causes some issues when the values vary in magnitude.

For instance, I have the values $34745$ and $211360$. It seems inconsistent to me to render these with 3 significant figures independently of each other, as $34700$ and $211000$, respectively.

On the other hand, choosing either as a baseline, rendering $35000$ and $211000$ or $34700$ and $211400$ seems to break the rules as well.

What is the standard course of action in this situation?


texts: Why do North American Roadways Use Yellow Instead of White to Separate Opposing Traffic?

texts: For those of us in the US, we're used to seeing roadways with yellow stripes separating traffic traveling against our direction of travel, and white stripes separating traffic traveling in the same direction. Of course, Chapter 3B of the Manual on Uniform Traffic Control Devices requires this. However, I noticed that countries such as England, Japan, Russia, Australia, etc., don't distinguish these features by color. What particular rationales are there for using the color yellow to separate opposing directions of travel on roadway facilities?


texts: I came across 2 creep coefficient diagram. First one is from Eurocode, second one is from elsewhere. I think the second one make sense, As the time progress, the creep coefficient shall increase, hence, the effetive modulus of concrete shall decrese. Can someone explain it ? I am confused.


texts: Does venturi effect helps in reducing temperature of a room?

texts:
I clearly didn't understand how this works, but the explanation and claim that it reduce the temperature of room by 5°c made me wonder, here I am trying to understand the Venturi-effect on temperature
This is something I found on web, Using old soda bottle and board they made some e-cooler

Note:- This system doesn't work, an enthusiastic professor did an experiment to prove it doesn't work. but is it possible reduce the temperature of room or a house using Venturi-effect ?


texts: Where on the data sheet is the supply current at 5 volts for the CD4081B?

texts:
I am trying to make use the CD4081B AND logic gate for starting basic Logic Gate circuits and I am trying to find the input current at 5 volts for the chip. I was wondering how to find it in the datasheet because I cannot. If anyone could help find it or show me how to calculate it myself that would be great.

Here is the link to the CD4081B datasheet:
http://www.ti.com/lit/ds/symlink/cd4081b.pdf


texts: How does a constant load affect the elongation of a steel cable?

texts:
I am sorry if this question has been asked before or if the answer is obvious, but I cannot seem to find the answer. A lot of the structural engineering problems we do involve calculating the elongation of certain types of beams/cables etc while under tensile stress. In particular there was a relatively straightforward question that asked for the total elongation of a structure comprised of two connected steel cables which have different cross sectional areas. Each of the two cables had consistent cross sectional area, and the structure was placed under an axial load of 800N.

Solving for the total elongation was simple with delta = (FL)/(EA) for each cable and adding the two deltas. My confusion however is with why this is considered the total elongation.

After the structure has undergone this elongation, it will become a 'new' structure, with a different length and different cross=sectional area for each cable. My question is, if the load continues to be applied after this 'initial' elongation (delta1+ delta1), then wouldn't the new structure still be under direct stress, and thus based on the new E of each of the now deformed cables, would each deformed cable undergo deformation again? And would this process not repeat until the object yields?

I understand that in tensile testing a specimen's stress-strain graph will be  obtained by deforming the specimen until it has yielded. This is why I am confused because under load, would these cables not just deform until they yielded? And if so, wouldn't total elongation then be based on the final length just before the yield point?

Edit: The two steel cables in the questions are connected together, with the cross-sectional areas of the two cables being distinct, i.e. a smaller circle stuck onto a larger one


texts: studying fluid mechanics, I see that viscosity relates shear stress to shear rate, like a slope. However, on graphs I see that they draw a triangle, and where I would expect to see $\Delta \tau $, I see $\mu_{ap}$ instead. Why is the slope being "drawn" along the y-axis, and not represented as the usual math slopes I have come across: $$\frac{d\tau}  {d \dot{\gamma}}$$.


texts: How to close a segment of a buried PE pipe

texts:
For a project we need to repurpose 2 buried PE pipes, by connecting them and closing off segments. My question is about how this closing off can be done.

Some details:
The lines are roughly parallel, DN 600 and DN 350. The connecting piece will be in DN 350. After the connection the pipework will look like an "H", then we close of one branch in each pipe to get a "U".
The medium is air at low pressure. To do the works, the pipes will be dug up.

An obvious solution would be to cut the old pipes and weld or flange the new pipe with a reduction and 2 arches on. I want to know if there's an alternative way, where I use weld on stubs and just close the branches of the old pipes I don't need. How would I close the branches?

Edit to add: After sleeping over this, we will very likely have the old branches excavated and disposed so the question is moot (for now).


texts:
Does anyone have a feel for the flatness of Portland Cement when poured in a standard/typical way? Say, for example, that I wanted to pour a cement "cube" (20"x 18"x 19.25") in a mold. How flat would the top surface be without any special procedures?

Background:
I am going to mount a forceplate on top of this cement block and I am trying to determine if I need to specify the flatness tolerance in the drawing.

Is there somewhere I can look for this information?


texts:
I've seen it in several data sheets - it is a measure of error of some kind, of course. The problem is I dont know the exact meaning. I've seen it in the context of repeatability, accuracy and linearity.

An example is the following data sheet: smc data sheet (On page 3)


texts: Why doesn't the European Type F plugs use a regular earth pin?

texts:
Plugs and sockets tend to differ between countries. Though many different standards exist the vast majority have one thing in common: The pins (earth included) are attached to the plug.
However this is typically not the case in Europe. The French type E plug has an earth pin on the socket while the German type F (Schuko) has two earth clips. The Schuko standard dates back to the 1920s and just by looking at it you can tell that a lot of thought has been put into the design (and at least one patent by Siemens) .
What are the reasons for avoiding an earth pin on the plug? Or put differently; what are the gains of the added complexity of the Schuko?
While type E/F systems are very safe when used consistently, earthed E/F-plugs may unknowingly be used with some unearthed sockets (eg type C and K).


texts: Why do recoilless rifle ammunition still have casings?

texts: Recoiless guns have breeches that allow gas to escape out of the back of the gun. Therefore, theres no sealing action to be performed by the casing. Why is ammunition with perforated cases used, when a propellant bag (like in other types of artillery) affixed to the shell would be cheaper an lighter? Is it necessary to build up the pressure for combustion of the propellant?


texts: Making a radial (only) seal inside a small tube

texts:
I'm trying to make a adaptor to fit a nozzle about 5mm wide which only applies pressure radially during insertion. Pushing in a standard O Ring would apply some force axially up or down the inlet due to friction.
The adaptor should seal in the inlet, before injecting gas to the object, see sketch. I can't change the object in any way, only the adaptor. Considering the size, can anyone suggest something off the shelf I can use for this? Or how I might make it at all?


texts: Searching for a material that respons to voltage change

texts: For a project, I need a transparent ball that is rigid, but under application of a voltage changes it's size, like a self-inflating balloon. Because it's rigid, however, and thus would break when expanded manually, I need to find a material that expands itself when the voltage is applied. I though about heating and about piezoelectric materials, but the changes are always too small, staying within a few milimeters of the original size. I've heard of electroactive polymers, but those aren't rigid. Shape memory polymers also seem to be an option, but I don't really know how well they work, and where to get them, etc. So, if anyone knows a material that can expand this way, or if someone finds a material that expands well enough when heated, please respond.


texts: How does a traffic light sense the proximity of vehicles?

texts: Some traffic lights don't operate periodically but instead detect when a car is close by and then turns green. I have heard that they use a magnetic sensor embedded in the road to sense cars as they come near. Is this correct? Do they use other means as well?


texts: How to calculate how much flow there is from a single source to multiple drains

texts:
Assuming that I have a water source ($Q$) that can flow into 3 drains ( $Q_1$, $Q_2$, $Q_3$):

Assume that we know that

The drain geometry is predetermined—we know the $x,y,z$ coordinates of the start and end node of the river/drain and we know the cross sectional information and length of the river/drain
The velocity is approximated by manning formula, $$V=\frac{k}{n}R_h^\frac{2}{3} S^\frac{1}{2}$$
The flow is incompressible flow, so $Q=VA$

where

$R_h$ is the hydraulic radius of the river/drain
$S$ is the slope
$k$ conversion between the SI and English units
$n$ the manning coefficient
$A$ is the cross section area of the river/drain

For one, I know that the water flow volume must be conserved

$Q=Q_1+Q_2+Q_3+...$

But I don't know what are the other factors that could help us determine $Q_i$.

Edit: After some research, I think that I need use Bernoulli equation to include headloss in this calculation, but I have no idea how to do it, how to proceed?


texts: In marker pens, why does the ink travel to the nib?

texts:
This question is specifically for felt tip pens and marker pens that contain a felt inner tube. The parts of the pen are:
- the body case
- the felt nib
- the felt inner tube

I do  not understand is why the ink within the felt inner tube moves up into the nib and then onto the surface in contact with the nib. Why does the ink not stay in the inner tube?

Please comment if you think any other tags should be applied to this question.


texts: Make a prototype of a braille tablet using arduino

texts: I want to basically make a pin matrix controller either by using spring, electromagnets or small motors. Spring being the most viable option. Something like what’s shown in the image. I'm pretty new to arduino and micro-controllers in general so any input would be appreciated.


texts: Does the voltage rating on transformer plates account for losses?

texts:
According to basic electrical machinery theory, all transformers experience power losses due to winding resistances, eddy currents, leakage flux and hysteresis. So when a load is connected to, say, a transformer with a 13800/240 V rating, the output voltage of  a transformer is slightly less than 240 V, for example 225 V.

My question is, when a real transformer has a rating of, for example, 13800/240 V etched on its plate, is this rating just the ideal rating based on the turns ratio N1/N2, or is the transformer built with a slightly different turns ratio to compensate for losses, so that at full load it ACTUALLY delivers 240V?

Also, the same thing for the power rating etched on the plate. Is it the ideal rating or does it take into account losses at full load?


texts: How to determine the work using volume and pressure in an adiabatic process?

texts:
$1m^3$ of gas undergoes an adiabatic compression from 1 bar to 10 bar. Determine the work required per kg, if its ratio of specific heats is 1.4.

I know that 1 bar is equal $1$x$10^5$Pa. I also know that $PV^k=constant$. I also know that through the adiabatic compression process that work, $w=[m*R*(T2-T1)]/(1-k)$ .
I tried using this equation. However how can I calculate the work using this equation if no mass has been specified and no change in temperature?


texts: How to mount a tube to a grease fitting?

texts:
I have a piece of mahinery with a grease fitting in an awkward to reach place. The fitting is of this shape ...

... but not screwed into place but pressed. So we can't have it removed and replaced with a pipe leading to a more accessible place.
My question is: Can I mount a tube to the fitting in a way that it stays there for the foreseeable future (a few years)? Grease will be applied twice a year. I have doubts that simply pushing a tube over the fitting and applying a clamp will suffice, as greasing will put some pressure on the thing. Any ideas?


texts: Why do the distress values for Pavement ME Design for alligator cracking and thermal cracking for AC pavements seem to give incorrect results?

texts:
When performing a pavement design using AASHTOWare Pavement ME for AC on AC Overlay, the pavement distress prediction for bottom-up (alligator) cracking and AC thermal cracking seem to give incorrect results.

First, the Reliability for both these distresses seems fixed at 50%. It does not allow me to increase the value.

Secondly, if I go ahead and run the program for 10 years the two distresses almost always remain zero (or close to zero).

Any ideas on this?


texts: How To Mount a Large Diameter Tire To A Smaller Diameter Axle?

texts:
I am building a cart from (What Type of Tires and Wheels Do I Need to Make a PVC Beach Cart?). I have a wheel whose central diameter is 3 inches and the PVC for the axle is 1 inch in diameter. I am planning on cutting a wooden circle and attaching it to the wheel and cutting a 1.25 inch hole through the center of the wood so the PVC pipe can pass through the wood. Is this a good idea or are there better alternatives?

Here is a picture of the wheel and tire


texts: What do you call a mechanism where rotation is transfered in one direction only?

texts:
I have the following to wheels that rotate on the same axis:

Assuming that they are stuck together, if I rotate the green one the red one rotates at the same speed and when I stop the green one the red one stops.

I'm looking for the name of the mechanism that makes it so that when I stop rotating the green wheel and I hold it in place, the red one keeps turning.

PS: I'm building a flywheel (represented here by the red wheel) and the green wheel here is connected with a belt to a crank. I want to make it so that the flywheel keeps turning even when the crank is fully stopped.


texts: Pouring aluminum into disks or cylinder shapes?

texts:
Is their a good method of making aluminum disks from molten aluminum?
I have a large amount of aluminum castings and I would like to make rounds that could be chucked into my late and used to turn parts. Typically the castings are reduced to molten and then poured into muffin tins for storage or use later.
It is difficult to hold the tapered shape in a lathe chuck. Is there a reusable method to pour longer shapes or am I stuck with sand casting the parts?


texts: How to center the potentiometer of a 9g micro servo without using a servo tester?

texts: I am trying to modify a micro servo for continuous rotation, but I am not sure how to center the servo's potentiometer without having to use a servo tester. The micro servo that I am using is  "SG90 Micro Servo Motor 9G".


texts: Why would you launch a large ship by dropping it sideways?

texts:
I'm referring to the process shown in this video:

https://youtu.be/Quyr5R1Rbfw?t=20

Or this image from Wikipedia:

In it, a large warship is launched into the water by essentially dropping it sideways down some ramps and off of a pier.  The ship rolls hard to one side, and then oscillates back to the other, making the process seem like a fairly risky one.  For instance, if it rolls back towards the pier too aggressively it might strike the structure and cause damage both to the pier and the shiny new warship.  Or if it rolls too far on the initial drop, the ship might capsize.

So my question is, what are the advantages of launching a large ship sideways like this, as opposed to, say, dropping or gently lowering it vertically into the water?


texts: Understanding pressure drop and mass average values

texts:
While studying some papers,  I didn't understand the following sentences:

  deltP the pressure drop across the turbine, evaluated using the mass average values at the inlet and outlet sections of the computational domain, respectively.

What is the exact meaning of the "mass average values"?

And is there such a option of "mass average values" in Fluent?  I dont know that how to compute this parameter in Fluent.


texts: Multiple sensor data to WiFi visualized on React Native app: Guidance

texts:
Objective: I want to connect multiple sensors to an item of equipment and visualize the data real-time on an iPad.

Mock of Desired Output:

Question: I need advice on the best methods to use to connect multiple sensor data and transfer the data through either wifi or Bluetooth.

Should I use / Is it possible to use Arduino (I have experience with this)

Are there existing wifi modules that allow for such a connection between multiple sensors and devices?

Considerations

I have experience with Reactjs and react native to build the application
Sensors are (RPM, flow rate, weight, and PSI)
This is pretty vague but I'm new to the IoT and acknowledge it will be a challenge.


texts: Plate thickness for repair of completely corroded web

texts:
The web of a H-section column has been completely corroded at the air-moisture interface with the concrete encasement leaving a hole in the web. The proposal is to break out the existing concrete and weld plates onto the web that will bridge over the hole in the web and will be welded on all four sides to good steel.

The plates will be on both sides of the web. If the web is 8 mm what should the thickness of the plates be? At a minimum should they be 4 mm to reinstate the loss of section?


texts: what college level teaches mechanical linkage design?

texts:
I'm 17 years old and learning first-year college math.

What college level math do I need for mechanical linkage design?
Can I learn designing and creating mechanical linkage without math but with my geometric intuition? or there's resource I can upgrade these skill?

It will be very good if you introduce some source textbooks which treat mechanical linkage design.


texts: Building oscillating magnetic field circuit

texts:
I wanted to create an oscillating magnetic field using an electromagnet which is rated for 12V continuous duty. I was thinking that I need an arduino to control the electromagnetic circuit by using a transistor. However, after doing some research, if I wanted to create an oscillating magnetic field that oscillates 1000 times a seconds, it would not work as the electromagnet would probably not respond that fast.

So I was thinking that maybe doing some research on an LC circuit or an H bridge would help me with my goal. But I needed some guidance as to whether or not there are other issues with my plan that I need to think about and where I should go to get the information I need?

Thanks


texts:
As most westerners know well, ceramic toilets are designed to be sat on, even by those who are quite overweight. However, since it's customary in Asian countries to squat when using the toilet, some visitors to western countries sometimes squat on the bowl of the toilet when using it.

When sitting, a proportion of the weight of the user is supported by the legs, but when squatting the user's entire weight is borne by the bowl.

This, and at least one report of a squatting traveller breaking a toilet bowl (!), leads me to wonder about the safety of this practice. I haven't been able to find any reliable scientific discussion of this online.

How much more force is borne by the toilet when standing/squatting on it? How strong is a typical ceramic toilet bowl? Is it safe to squat on a toilet?


texts: Why doesn't the Stress Power in the theorem of the expended mechanical power contribute to the kinetic energy?

texts:
The following is the formula of the expended mechanical power:
$P(t)$ $=$ $\frac{d}{dt}$ $\int \frac{1}{2} \rho\ v^2 dV$   $+$ $\int \sigma \colon d\ dV$
where $P(t)$ is the mechanical power entering a continuum medium, $\rho$ is the density, $v$ is the velocity, $dV$ is a differential volume, $\sigma$ is the stress tensor, and $d$ is the strain rate tensor.
The first part of the right hand term is the rate change in kinetic energy. It is logical that the forces (body forces and surface forces) exerted on the continuum body will do some work, and this work per unit of time is a power and will contribute to the total power of the system.
But as for the second part, it is referred to as the Stress Power. By other words, it is the work per unit of time done by the stress in the deformation process of the medium.
What I don't understand is that the Stress Power  is said to be the mechanical power that is not spent in changing the kinetic energy. How is that?
During the deformation process, a displacement of particles will take place. So, the particles will be changing their positions in the medium. And such a movement should as well create a velocity for them, hence a contribution to the kinetic energy. So stating that the stress power is not spent in changing the kinetic energy seems not logical for me.
By the way, I got the information from this video


texts: What are the disadvantages of concentrated solar thermal power?

texts: Concentrated solar power looks on the surface to be an excellent source of grid power. It's sustainable, has no obvious waste products to deal with either during construction or operation, and with thermal storage it can generate power at night or on a cloudy day. It seems to address every problem with fossil fuel, nuclear, PV, or wind generation. Is there some disadvantage to this that I'm not seeing? Shouldn't we be building these plants as fast as possible?


texts: Is it a good idea to start any engine once in a while?

texts:
So I was thinking that its not good to let a car engine sit. Since the oil and all moves down to the pan and all that other fun stuff, so what about small engines? I was thinking about whether it was good to start, for example, my 3 small engines. Being the push mower (4-cycle), riding lawnmower (4-cycle), and weed wacker/trimmer/eater (2-cycle). It seems to me to be a good idea since the oil and stuff must, like a car, sit someplace. And for 2 cycle all that lubrication would eventually dry up, and that would seize the engine, right? Now I am going to add that there is no fuel left in these engines. Well the rider does have a half tank.

So simplifying, is it a good idea to start these smaller engines like once or twice a month? Just to keep everything lubricated. Also adding, if this is benifitial, which one (4-cycle/2-cycle) would get the most benefit? Thank you

Side note: I hope this is fine for this site, but there is no place else to ask (that I know of).


texts: What type of control does the TCP protocol offer?

texts: I am asking for a categorization of the control mechanism that TCP uses for flow and congestion control. Obviously, it is closed-loop but would that be discrete? Event-based? Continuous?


texts:
I am trying create a graph similar to as shown below. However, I am confused as to how the torque is related to the characteristics.
The graph that is to be replicated for certain parameters:

The parameters that I have been given are:

All parameter values are known, however, no function of the torque is known. However, I have been given the following 2 equations:

So my question is how is torque related to the efficiency, power, current and speed, as I have conducted research on how these graphs are plotted but didn't find anything that helped. As I only know of single points and not full functions of the dependency of the paramteres on the torque. I am using MATLAB to plot these, below is the most up to date script:
v = 24; %voltage = 24 V
r = 0.7; %resistance = 0.7 ohms
j = 7.95e-5; %inertia of the rotor = 7.95e-5 kgm^2
k = 0.059; %motor constant = 0.059 Vs/rad
b = 6.65e-5; %damping coefficient = Nms/rad
l = 9.8e-4; %inductance = 9.8e-4 H
i = 0.4494; %steady state current = 0.4494 A
w = 400; %steady state angular velocity = 400 rad/s
T_l = 0; %Torque applied to the motor = 0;
time_period = 0.0014; %time period of the circuit = 0.0014 s

torque = 0:0.1:2;

I = ((v-k*w)/r)*torque + i;
figure
plot(torque,I);
xlabel('Torque');
ylabel('Current');

The equation I used for I is something I made up and I am not sure how correct this is; I thought of trying this because the example graph shows a linear relationship between current and torque. The graph that I got was:

Any help would be much appreciated.
P.S. I know it's a long read, but thanks for reading the entire thing.


texts: Specific CO2-Emissions of Natural Gas & Hydrogen Mix

texts:
consider I have a mixture of Hydrogen and Natural Gas.
The volumetric mixture is $\varphi_{H_2} = 70 \%$ and $\varphi_{NG} = 30 \%$.
So the $H_2$ makes up a mass fraction of
$$w_{H_2} = \frac{\rho_{H_2}\cdot\varphi_{H_2}}{\rho_{H_2}\cdot\varphi_{H_2}+\rho_{NG}\cdot\varphi_{NG}} = 21.2 \%$$
with $\rho_{H_2} =  0.0899 \frac{kg}{m_n^3}$ and $\rho_{NG} =  0.780 \frac{kg}{m_n^3}$.
How much CO2-Emissions does the combustion of $1 kWh$ of my mixture produce, if the combustion of Natural Gas produces $0.200 \frac{kg}{kWh}$? How does the calculation work out?


texts: Where is the "angle" in the first, second, etc. angle projections?

texts:
This question is about engineering drawing and representing a 3D shape on a 2D paper, so there are "four" angles of projections which we can use to draw, but I'm not sure about that, and I don't understand the meaning of "first angle" and "second angle". What does the "angle" mean in the first place? What are the quadrants which they are in? Please explain these concepts:

The angle
The quadrants

Please include a detailed answer for how many angles are there, and all the possible manners for drawing an orthogonal projection. and do not refer me to external books or links unless you specify a specific portion of them.


texts: How to calculate the energy needed to ionize air at a specific temperature?

texts:
I have not found any information relating to using electicity to ionize air with temperature, but I am sure that there should be some information available.
I am thinking of the nozzle of modern jet engine (about 2000℃)considering I don't have any sophisticated equipment.

Is there any way to measure or even calculate the energy(Joule) needed to maintain ionization of air at high temperature(2000℃)?


texts: How to calculate hydropower in kW without water head

texts:
I am trying to do some calculations to figure out how much power output would be produced from a water powered generator that uses horizontal current flow to move the generators coils rather than vertical water drop.

The formula to calculate power is:
$$\text{Power} = \rho gh\,Q\eta  $$

where:

$$\rho = \text{density (kg/m3) (~ 1000 kg/m3 for water)}$$

$$Q = \text{water flow (m3/s)}$$

$$g = \text{acceleration of gravity}$$

$$h = \text{falling height, head (m)}$$

$$\eta = \text{efficiency}$$

However, I am unsure how to calculate when gravity and falling head are out of the equation, as setting them to 1 or 0 will give incorrect answers.

the water flow is $3.1m^3/second$

the efficiency is $0.78$

If anyone could explain how to calculate the power output I would be extremely grateful.

Below is a link to a similar device to what I am describing: Waterwheel Documentary- Harnessing Electricity on the Zambezi River