texts: A couple of questions about making an electric hobby car from scratch

texts:
So I'm a high school student doing some competition (a wallet-sized one, unfortunately) and I'm supposed to make an electric car. Think an RC-car, (about that size) without the remote control. I want to make one from scratch, so I decided on using an arduino for a micro controller. Unfortunately, I don't really have an adviser that's particularly knowledgeable about this stuff, so I decided to ask here. (brace yourself for quite a few possibly dumb and vague questions. I do understand this question will likely be edited/closed for being too vague, but if, by any chance, someone has answers, I'd also like explanations -- mostly because I want to learn something.)

I've decided on using an aluminum chassis and soft wheels, since the competition wants a car that can go as fast as possible. I've chosen soft wheels because that should give me higher friction, and an aluminum chassis because I want to reduce weight. Now, here comes the first problem. The competition specifies a maximum of a 9v battery to power everything, including the arduino and the motors. Now, of course, we only need to go about 10 meters (I just want sub 3s times). My original design involved having 4 separate dc brushed/brushless motors, and then connecting each dc motor directly to the wheel. The dc motors could be held on with brackets, and then connected to an Arduino connected to a MOSFET, at which point I could then use a motor encoder to see how far to go.

I now have a couple of questions:

Should I try having a 9v to 12v converter? or a 9v to 24v converter? That might cut the current significantly, but I'd also be able to use a much more powerful motor. The problem I have with this is that it might be adding a lot of potential weight -- as I understand it, I can't convert directly from DC 9v to something else.
I've decided on having a rear wheel drive rather than a 4wd -- but is it worth getting a gearbox and an axle and just having one motor?
Should I use a gearbox at all? Or should I try to change the speed based on the size of the wheel I use?
Would I try to maximize RPM or torque by getting a geared-down brushless?
If I have a 9v battery, can I have 2 9v motors in parallel? Or is that unsafe because 9v is only nominal?

If anyone has tips on how to improve the question, I'd be glad to incorporate them into my edits.

some info, by the way:

looking for sub3 second times
using banebots 2-7/8 inch diameter wheels
hard floor
will need to back up after 9m
only going straight, doesn't need to be able to turn
thinking of a PID loop with a physical rotary quadrature encoder if one axle. thoughts?
the car will be ~1kg and I won't be carrying anything else.


texts: How much does the weight of urban structures (buildings) affect the compaction (permeability, porosity, density) of alluvial sediments below a city?

texts:
Original Question was here.

I live in Van, Turkey. Van City is situated on an alluvial plain beside Lake Van. General geological structure of the area can be seen on pages 43-44 in this conference book. One of the images is below.

According to the article in the link, sediment layers has a slope of 15-30 degrees toward the lake.

With the construction of every building, the pressure over the sediments increases. Obviously, this increase is greater in downtown area which has a lot of apartment blocks (mainly 5 to 7 story high reinforced concrete buildings). Downtown area is roughly in the middle of the plain.

I want to know that how much does the weight of urban structures (buildings) affect the compaction (permeability/porosity/density?) of alluvial sediments below a city and how does this affect the flow of underground water?

How much the stress caused by the weight of the building decreases with depth? (of course if at least a broad value can be given to help to explain the size of the change). I wonder to understand that either the effect of the weight of urban structures is generally negligible, or not.


texts: Is analog|digital different from continuous|discrete?

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(Discrete systems for my question are further divided into periodic and event based)

By reading around I have a feeling that analog does not equal continuous and that digital does not equal discrete.

For instance, in the case of a periodic discrete control the measurements may not be digitized, not even quantized and simply fed into a controller. Is this correct?

If yes, does this mean that there can be 6 types of systems? Analog-continuous, analog-periodic, analog-event_based, digital-continuous, digital-periodic, digital-event_based?


texts: Comparing 2 shock scenarios with different magnitudes and times

texts:
For example,
How does one compare 100 g's for 6 milliseconds to 45 g's for 11 milliseconds. These are two different shock scenarios with different magnitudes and times, so how can I compare them? If I have something that is shock rated at 100 g's for 6 ms does this imply that it will withstand 45 g's for 11 ms?

I have tried finding a "shock equivalence" chart or a metric for comparing two shock scenarios but I haven't found anything.

I was thinking it may depend on the mass of the equipment that is being shock rated:

$$v=at$$
$$F=ma$$
$$Power=Fv$$

An energy metric like power may give me a reasonable estimate to compare, but I am just guessing here. Is there a standard way to compare two scenarios? A chart or equation would be nice..

Thank you for the help!


texts: Swapping transmitter and receiver locations

texts:
Pardon me if this is a silly question, because I don't quite study RF.

Let's say I have a set of transmitter (radio + antenna) and a set of receiver (radio + antenna), at location A and B respectively. Then I transmit a signal at a certain power, for example 5W, and I measured the signal at the receiver, say 3.4W, due to losses incurred when it travels from point A to B.

Then, I swapped the locations of the transmitter and receiver. I have also rotated the antennas by 180 degrees, this is to ensure consistent gain at the angle towards the other antenna, if directional antennas are used (I'm not sure if I'm making sense here).

Will this result in the same received power (i.e. same loss)? What are some things that would affect the results and that I have overlooked?


texts: I am trying to draw a section from the front look of the unit and I am struggling with the stairs. The stairs on the plan below are located on the right side and I wish to draw the view out of them from the front view. How can I achieve this?


texts: Better way to cancel “hammer beating wall” noise

texts:
I live very near a bulding contruction site, so the "hammer beating wall" noise is a constant in my daylife for the next one year and half (when the building construction will be finished).
In order to cancel the hammer noise, I use a 40 mm headphone with fan noise playing in medium to high volume (I mean, not low volume, but not maximum volume). (My headset doesn't have noise-canceling feature by the way.)
I ask:
1 - Based on Acoustics Science, is this the best way to cancel a "hammer beating wall" noise?
2 - Is there any other frequency, or combinations of frequencies, which I could build using a software, which would be the perfect match for canceling hammer noise? I mean, even better than fan noise frequencies?
Hearing a loud fan noise with headphones is not that nice thing, but is way better than the hammer. It cancels the hammer noise (I hear nothing, but I feel the floor vibrating a bit). So I am searching for the ultimate sound for cancelling the hammer beating wall noise.
Thank you for any help.


texts: Choosing a blower for a Pneumatic Conveyor

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Basically we are designing a pneumatic conveyor system for transferring 11 tons of beans per hour.
We need to decide on the specifications of the blower. What are the calculations necessary to decide on a blower wrt. static pressure, flow velocity and type of blower?


texts: Along which direction is the area moment of inertia taken in bending moment equation?

texts: Is it in the same direction of the applied load or in the co-planar perpendicular direction to the load applied?


texts: How is it possible for trajectory and streamline to coincide in case of stationary velocity field?

texts:
In continuum mechanics, the definition of trajectory or pathline is the locus of the positions occupied by a given particle in space throughout time.
And streamlines are a family of curves which for every instant in time are the velocity field envelopes.
For a stationary velocity field, trajectories and streamlines coincide..
How is this possible? Even if the velocity didn't depend on time, and was only changing with the change of position, it doesn't make sense for the streamline and trajectory to coincide because they hold different physical meaning.


texts: Are recoil operated crossbows/ballistae feasible?

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This question is specifically about stationary or vehicle mounted crossbows, not man-portable ones
The projectile size would measure about 1.8 - 2 meters in length, so the crossbow would have corresponding proportions
The materials would be wood and metal/metal compounds, no plastics
The goal is to have a siege engine capable of cocking itslef, like a recoil operated firearm would

The easiest concept I have in my head for this would be as follows:

There's a carriage riding on two rails that carries the projectile
The carriage has two holes on the sides
A wire is threaded through these holes
At the front of the crossbow two springs are placed around the wire
When the carriage gets released and propells the projectile it hits the springs and gets pushed back into it's resting position

(simple sketch of it)

Could the cocking springs provide enough energy to push against the limbs and get the carriage back into it's resting position?
Are there any pitfalls with a system like this?
Is there a more efficient way to build a recoil operated crossbow?


texts: How to get element coordinate system information (location, angle) for each element using ANSYS Mechanical APDL

texts:
We can get local coordinate system information (location and rotation angle (in degrees) relative to the global Cartesian coordinate system.) by using *GET, Par, CDSY, N, LOC, X (Y or Z) or *GET, Par, CDSY, N, ANG, XY (YZ or ZX).

Is there a way to get the element coordinate system information for each element?


texts: Overhead cable vs batteries for vehicles

texts: This mainly would concern Europe, since part of the infrastructure is already in place (trolleys overhead cables). What economic reasons prevent electric autos sans large  batteries from being feasible in European cities? Lithium is considered by most environmental unfriendly, both extraction, usage(flammable), and disposal. I would see Europe being forefront of electric autos without batteries if it were feasible.


texts: Fragmentation of a curved cantilever beam under compression

texts:
Suppose we have a curved beam of a rectangular cross-section $A$, Young's modulus $E$, and a constant radius of curvature $R$. We now expose the beam to a vertical point load of magnitude $P$ at its free end:

What I now want to know is where the beam will snap (I am assuming perfectly brittle material behaviour, and that the beam material is far stronger in compression than in tension). For this simple case, this is relatively straight forward (the beam will snap very close to the point of force application), but I want to know what happens when $P$ is shifted along the negative x-axis closer to the clamped end of the beam. For clarity:

Etc. pp.

Intuitively, as $P$ is shifted along the x-axis, the dominant type of stress will shift from bending to compression; if $P$ is applied very close to the clamped point, it's essentially a buckling problem, while it's similar to the bending of a straight cantilever beam when $P$ is applied at the free end. Now what happens in between, and how does this transition take place?

My gut feeling is that as $P$ is shifted (for clarity, I don't mean to imply any dynamic loading here), the point at which the beam will snap will increasingly move away from the point of force application, so if we were to start loading the beam at its far end until it snaps, then move the point of force application to the new far end and so on, we would end with snapped fragments of the beam which increase in length. However, I have thus far failed to come up with a sensible model that would allow me to predict whether this is what is actually happening, and would be grateful for any hint.


texts: Use 4 to 5-second timer to disengage/engage mechanical system

texts:
So I am working on a project. I need a drone (quadcopter) to ascend for 5 seconds, then cut off power to the drone, then let it stay in the air for as long as possible without power. My idea for allowing it to glide is to have some rubber bands attached to some parachute like material, and the rubber bands will be stretched and held in place by some pins. After 4 to 5 seconds, the pins will disengage, allowing the rubber bands to compress, expanding the parachute-like material. An image is included to illustrate what I mean.

The red lines illustrate the rubber bands. The black are the quadcopter arms. The blue circles are where the pins would be located. After the timer stops, the image on the right demonstrates the rubber band straightened, and the purple is the parachute area. There will be one parachute per rubber band, and each rubber band will have its own locking mechanism.

So what I want to figure out is how to design a mechanism that will retract a piston/pin after 4 to 5 seconds. I did some research on pneumatic cylinders, and I figured I could have pressurized air entering the cylinders with air leaving the system slowly until the piston disengages the rubber band. There would be some measuring to get the required air pressure needed to have the pistons last 5 seconds, but these cylinders are too expensive and too long for this application. Then, I read the post linked at the bottom of this post, and I think the mag-locks would be great, but I have only found them in rectangular forms; none of them have the geometry needed for this, so I figured I could have the mag-lock attached to the bottom of the drone, and the mag-lock would pull pins that were attached to springs that are attached to the top of the drone; when the mag-lock deactivates, the pins would retract, allowing the rubber band to disengage.

However, I am having issues with finding timers that are suitable for my task. Kitchen timers don't work well when it comes down to setting them for 5-seconds. I want to know if you guys have any ideas regarding getting a timer that would be well suited for this task and if you guys have any suggestions as to how I could improve the design of the parachute mechanism I have planned.

Post mentioning mag-locks: Is there a device like this?


texts: Is a 3 Hz beat frequency from my neighbor's HVAC a sign of a malfunction?

texts:
I'm being annoyed by a pulsating hum which comes from my neighbor's HVAC system. I read up a little on the design of HVAC systems and I came to a tentative conclusion that what I'm hearing is a compressor being driven by an AC induction motor. A frequency spectrum shows a spike at 120 Hz and another at 117 Hz; which of course produces a 3 Hz beat. The 117 Hz spike actually moves around between say 117 and 118 Hz. I guess what I'm hearing is called a "slip frequency beat"? I'm in the US, where the mains frequency is 60 Hz; so 120 Hz is the audible hum produced from magnetic fields in motors, transformers, and so on.

According to this document (p. 3), the "slip frequency", defined as "per-unit slip times line frequency" is the "actual frequency of current in the rotor conductors". Per-unit slip is proportional to torque and is commonly 0.03 - 0.05. This means 3 Hz could be a typical slip frequency, and I guess 117 Hz could be a slip-frequency sideband of 120 Hz. But there is no 123 Hz spike, and in fact the rest of the spectrum is pretty quiet except for spikes at 59 Hz and 29 Hz. There are harmonics at 234 Hz and 240 Hz, but the harmonic at 352 Hz is stronger than that at 234 Hz. All the harmonics have much less energy than the 117 Hz and 120 Hz fundamentals (say >20 times less). The 29 Hz and 59 Hz spikes don't seem to vary much when the compressor turns on and off, and neither does the 120 Hz spike. Only the 117 Hz spike and its harmonics show an "on-off" square wave in a time-series plot, corresponding to compressor activation at 10-minute intervals.

I can't provide decibel-calibrated sound pressure levels (and since I don't have access to the equipment, I can't measure the actual vibration intensity). I would say the sound is not loud enough to be annoying unless you have to live next to it.

I have calculated that the sound amplitude in the 117 Hz "spike" is 3 times higher than that in the 120 Hz spike. I don't know if this reveals anything significant.

I've read that the speed of an AC motor is 120 Hz / (number of poles), and that the minimum number of poles is 2, so I'm concluding that the motor cannot be turning at just under 120 Hz (7200 RPM) but rather must be going at some slower speed like 60 Hz (3600 RPM). This seems to imply that the 117 Hz vibration is not mechanical vibration from the rotor - but I'm not sure what else it could be. The linked document mentions certain faults producing vibrations at 2 x RPM, but it seems these should be concurrent with vibrations at 1 x RPM. But, as I said, the 59 Hz spike doesn't vary with compressor activation.

Here's a time-series plot of various spectral amplitudes, taken over 6 hours at night. The spectral bands shown here are 58-59 Hz, 116-118 Hz, 174-177 Hz, etc. You can see that compressor activation doesn't seem to affect the 59 Hz spike, but there is a clear signal at 117 Hz and 3x117 = 351 Hz. (I also appended a spectrum plot)

According to the linked document, some amount of vibration is normal and the surest way to diagnose a developing fault is to take spectral readings over time and see if anything is getting worse. The neighbor's HVAC system is 20 years old, but I only have readings for the past six months, and there seems to be a lot of fluctuation just from weather conditions and diurnal temperature variations influencing the propagation of sound across the property line. Because of this I can't say that there has been an obvious trend upwards in sound amplitude over this time period.


texts:
I am trying to write a program on Aspen Hysys. Hysys has a script manager to write scripts using Visual Basics for Applications syntax. Having no background in VBA, I'd like some help to:

Import the current value of a controller's output signal (OP).
Compare it with it's previous value (in a dynamic simulation).

Any help would be appreciated!


texts: Toggle position of a fourbar slider-crank

texts:
In the fourbar mechanism as in the following picture, I have to find the toggle position, the sliding distance and the time ratio.

Here is my understanding/plan to do this:

The toggle positions ("extreme ends") of the slider (block B) take place at 2 time, when link 3 and "offset" are aligned, and when link 3 and 2 are aligned.
The sliding distance can be calculated via trigonometry from the above conclusion
Assume the working cycle is the part where block B moves from left to right, I have to find the working angle of this movement at crank ($\beta$), the time ratio would be $\frac{360-\beta}{\beta}$.

Am I right in my understanding so far? If not, where do I have it wrong. And then, how do I obtain the value for $\beta$


texts:
I am trying to emulate the resistance of a hand wheel which moves a table via a series of shafts and chains which turn an acme screw. I am switching to a CNC system that will allow the user to keep the old style crank for manual positioning. The crank will instead attach to an encoder which will command the CNC system.

My problem is encoders don't have shaft resistance or enough resistance. What I am looking for is a method to produce shaft resistance that feels sticky. You could quickly accelerate it but you have to put a bit of effort behind the motion and the crank would stop dead and hold its position when let go. I tried searching for such a device but perhaps I am searching for the wrong terms. In my head I picture one or more slotted discs sealed in a housing filled with a very viscous or sticky liquid. The only thing that comes close is a viscous shaft coupling. But they are couplers. I need a through bore or keyway whose housing can be mounted to a frame.


texts: How the optical cd disc gets drawn in when we gently push it? what is the mechanism behind it?

texts:
We have seen CD drives that have slits. The CD gets drawn inside upon a gentle
push. how the CD gets drawn inside upon a gentle push? How it's mechanism works?


texts: How to stop DC-motor with heavy weight from moving?

texts:
I'm planning to build a machine which at some point tows a heavy weight on a rope in the air. Once the weight is heigh enough up in the air I want to keep it there for about an hour or so, before I want to put it down again in a controlled manner.

As far as I know, I can brake a DC motor, but I think this takes energy so I would like to avoid doing that for as long as an hour. I guess there should be other options, such as putting a lock of some sort on the rope, but I have no clue how something like that would work.

Could anyone give me some tips on what a usual/best way of blocking a rope for a long time is?


texts: Can a rod be attached perpendicular to the motor shaft

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So, I was trying to make something like this

.

However, While I have the motor, the motor has a vertical shaft and I need something to connect a rod to it in a T shape

Is this even possible? And if yes, then what should I get?


texts: How to calculate the gear ratio of planetary gear?

texts:
I saw this picture today:

They give an ratio of 5/352. I think this is not possible with a simple gear. Maybe the upper sides ratio is the cause for it.

Which formula do I need to calculate the ratio for first half and which one for the upper half?

I want to use it for a stepper motor (nema 17) as a gear box to increase the torque.


texts: Why are parts of a cylinder closer to centre elongated less during torsion?

texts:
Say we have a fixed cylinder with a radius of $R$. Looking at any cross-section, the shear stress at a radius ($r$) is given by $\tau = G \gamma $.

I understand that the particles at the outer radius ($R$) twist (or elongate) more than those at any inner radius ($r$) so it makes sense that they would have more stress. However, I was wondering why it is that the outer radius particles twist more than the inner in the first place if the same force is applied at all radiuses.

To make it more clear:

Picture a large circle being twisted due to a shear force $F$. Why is it that a circle with a smaller radius will twist less due to the same shear force $F$? What is the reason behind this?


texts:
A piston pump has a swash plate that pivots back and forth to control the flow rate of the hydraulic fluid.

Is there a version of this pump where the swash plate rotates like a cam instead of the pistons rotating?


texts: Why does audio equipment buzz/humm when a long signal cable is used and how do I eliminate it?

texts:
I have two 5.1 speaker sets, one in the front and one in the back of my living room. I have connected them together with an "audio wire" (non-shielded unfortunately) that's 12 meters in length.

Since I did this, the speakers started buzzing/humming when turned on. This however stops when I connect the audio wire (through an Y splitter) to my laptop. This got me curious: What happens if I connect the COMM wire on from the Y audio split to the COMM on my laptop charger? The buzzing/humming stops!

There exists some circuit in the laptop charger that is being able to cancel/even out the noise.

Why does the humming/buzzing happen? And Why does it stop when I connect audio COMM to charger COMM?

Can I fix the buzzing/humming noise by making some circuit using passive components I have lying around from DYI kits (Arduino etc)?

This is how the setup looks like in diagram form:


texts: Why do drag race semi trucks slant to one side?

texts:
I've been watching drag races of semi trucks and found that, especially during the initial phase of acceleration, they all bend to their right-hand side.

I understand, that the huge torque in rear wheels would lift the whole front of the truck, but why does it slant to one side?
Can rotational inertia of the drive shaft be strong enough to cause such a phenomenon?


texts: Transfer function of a temperature controlled incubation system

texts:
I am a computer engineering student and currently having my undergraduate thesis. My thesis is about temperature control system of a chicken egg incubator. I searched over the internet and found this research. Please verify if i can use this transfer function for my temperature control system of an chicken egg incubation system with desired temperature of 37.8 °C.Inside the research, the researcher calculated the transfer function
from the equation Q = CT and the netwon's law of cooling and arrived at this transfer function.

Question 1. Is this transfer function applicable to my chicken egg incubation system?
Question 2. Is there other things to be added or considered for calculating the transfer function of a thermal system aside from what the researcher calculated?
Question 3. The paper tells us that Tau is the time it takes to achieve the maximum temperature of the incubator. I turned on the 200W heat rod in my incubator and the time it took to reach 37.8 °C is 240s. Isn't that very fast? Cause i did a simulink of this transfer function and the transient response(rise time, overshoot, settling time) is very fast compared to the real scenario. I tried 940s and its closer to the real system than 240s.


texts:
I would like to calculate the spring constant of a frame structure.
I thought that I could do it like this:

I apply a point force on the structure:

Then I calculate the displacement at that same point:

Finnaly, I asume that the material bends within its elastic limit:
$k=\frac{F}{\delta_y}$

Question1: Do you agree with this method ?

Question2: If I have a different type of loading, for instance a distributed load, would the spring constant change ?


texts: Heat Transfer coefficient calculation for hot air flow inside rectangular duct

texts:
I am working on modeling of air-heater component. A simplified representation of system is as follows:

Cold air flow enters steel duct at one end. Inside duct is Calrod heating element shaped as ellipse. Follwing heat transfer occur simulteneously:-

Air gains heat from surface of heated calord.
Air also exchanges heat with duct inner surface.
Calrod element radiates heat to duct inner surface.
Duct loses heat by radiation to surroundings as well as convection.

System is solved by taking energy balance equations on Air mass, Duct mass and Heater element mass.

My question is in regards to convection between air and duct. In model, I have considered whole assembly to be made of 5 parts along duct length. In each part respective thermal balance on air, duct and heated element mass is taken. In each part, I consider air to be lump-sum mass. Entering air gains heat from calrod and gains some temperature ( which would in real world be average temperature). Problem occurs when that temperature is used for convection transfer with duct. In actual process, air flow is fast enough (0.013 $\frac{m^3}{sec}$) so that air that actually is in contact with heater element doesn't reach duct surface. So air that exchanges heat with duct inner surface is at lower temperature than average air's temperature. This gives incorrect duct temperature predictions. How can I properly set $\Delta T$ for convection heat exchange with duct?


texts:
I am designing an NSAM crane. I have encountered the following issue when designing the vehicle:

Generally the pivot(or the point about which the NSAM crane rotates) is in the center. But from two online sources(https://patents.google.com/patent/US8002074, https://www.tandfonline.com/doi/abs/10.7158/M12-108.2014.12.1) I have found that if the pivot is in the center, then the NSAM crane has easy maneuverability and tip over stability. If the pivot is away from the center and towards the rear axle, the roll over stability is more.

Even though some calculations have been given in the sources, I am not able to understand why this is the case and which stability is more important for the NSAM crane?

Also please help me with any Simply supported beam type of calculations for the stability if any.

Any references would be appreciated.

Thanks


texts: Why is the left-side view called like that?

texts:
The top view looks at the top of the objet from the top of the object, the front view looks at the front of the objet from the front of the object. All seems logical.

So why does the left-side view looks at the right of the object from the right of the object?

EDIT:

I'm talking about first angle projection. I'm not entirely sure but I think I doesn't change anyway with third angle projection.

For those who say it doesn't. It's in the words: yes, for the left-side view, the observer looks towards the left. But the side that he sees if he looks towards the left is the right-side of the object.

If we were following the same logic, front view would be the back-side of the object because the observer would be looking towards the front. But it isn't: for the front view, the observer looks towards the back.

The naming isn't consistent. Either we name the view after the direction we are looking towards, or after the side of the object that we see.

The position of the plane of projection doesn't change anything, it just changes were we draw it on the paper when we unfold the view.


texts: What is the name of this thing? (hex key reduction?)

texts:
What is the name of this thing?
I am trying to find it by keywords like "hex hey reduction" etc. but so far no results. My problem is that the plastic socket is easily damaged and I want to find a similar item, but made from metal only.


texts: Powder form of material with high thermal transfer

texts:
The Engineering Toolbox presents a chart of "common" materials and their thermal conductivity coefficients. I'd read or learned some time ago that diamond was superior in this respect. The chart shows diamond at 1000 W/m K compared to the next closest, silver at 429 W/m K.

My objective is to reduce the grip of a thermal pad between a heated bed and a glass surface. The heat transfer from the bed to the glass was improved by the addition of this thermal transfer pad, but the pad is very sticky, one millimeter thick and relatively fragile. I've only now discovered that this product is discontinued!

Pursuant to this objective is the ability to lift the glass, with the thermal pad (dusted?) remaining on the heater, without the pad adhering to the glass. It's not adhesive, but it sticks with the power of gekko.

I'm considering to powder one surface of the pad, but do not wish to reduce the thermal conductivity. I'm aware that diamond powder exists for lapping/grinding purposes, but have also found that most of the product listings provide the expression "synthetic diamond" in the description.

Even though SE discourages more than one question per post, these are all related to my objective.

Is there a better choice than diamond powder to provide a thermally conductive release mechanism between the thermal gap filler pad and the glass?

Related:
Will synthetic diamond powder display the same thermal transfer characteristics?

Edit Added from comments:
The bed is a flat electrical heater (3D printer) with a range from ambient to about 100°C. There is normally a 1mm air gap to the glass bed. As such, the air gap has to be heated before the glass reaches the desired temperature. Having installed the 1mm transfer pad reduced the elapsed time involved.


texts: Derivation if the formula for the surface moment of inertia of an isosceles triangle

texts:
For a isosceles triangle with base b and height h the surface moment of inertia around tbe z axis is $\frac{bh^3}{36}$ (considering that our coordinate system has z in the horizontal and y in the vertical axis and got it's origin on the triangle's center of mass (which is at $\left\{\frac{b}{2},-\frac{h}{3}\right\} $ if you put your coordinate system in the bottom left corner if the triangle).

I know that the formula for the moment of inertia around the z axis is $I_z  \int_A{y^2 dA}$, but I can for the love of god not figure out how to derive the formular from that. How is it done?

Any help would be highly appreciated!


texts:
According to James Cameron, the submarine barely had any space for him to move around etc., and as he approached the bottom of the Mariana Trench, the submarine shrieked down by a few inches (due to pressure).

Why was the challenger deep designed to be just big enough for James Cameron to fit in?


texts: Frequency dependence of electromagnetic shield metal

texts:
I know that the effectiveness of metals used for electromagnetic shields heavily depends on the used frequency or frequency range.

I could not find a resource in the web (tables or graphs) that give me the information which material (especially ferromagnetic vs. diamagnetic) should be selected when shielding a component from a given frequency.

Is there some information about this in the web? Which is the most effective metal for a frequency of 125kHz?


texts: Inverse kinematics solutions pros and cons

texts:
I know at least 3 different approaches to solve inverse kinematics problem. They are pseudo inverse jacobian, cyclic coordinate descent and ANFIS networks. I would like to know advantages and disadvantages of these methods comparing to each other.

I know that CCD suffers from local minima but as I heard this problem seldom arises in practice. However it is more intuitive and easy to implement comparing to pseudo inverse jacobian. Therefore I wonder why would one use inverse jacobian instead of CCD?

While these two methods I have found to be the most popular there is another approach called ANFIS networks which requires gathering training data from forward kinematics equations and training a neural network. It seems a bit overcomplicated to me. Why would one prefer ANFIS to CCD or pseudo inverse jacobian methods?

Thanks.


texts: Sonomotors, Sion: Can this electric car really charge up to 30km only from its solar cells?

texts:
Maybe you have heard about Sonomotors and its futuristic electric car, the Sion.
If not, here is the link to its website: https://sonomotors.com/

Anyway, the manufacturer claims that this car can recharge up to 30km on one day using its own solar-cells.

I have come to Physics Stackexchange, because I want to know: Can this be true ?

(I am looking for well-researched, fact based, answers without any bias for or against this car.)

EDIT: got some good answers... but let's really crack it down... Can we chose Germany for instance, look at the solar radiation per month and compute an expected range per month?


texts: What grade of Neodymium magnets are commonly used in hard drives?

texts:
I want to buy some magnets, but the ones that I have found on online shops are mostly grade N38. They are pretty cheap, but they need to be as strong as the ones found in a hard drives. I am afraid hard drive magnets are N52 (or at least a higher grade than N38).

Is this correct?

edit:

Is there a minimum grade that must be used in hard drives?

maybe for the possible heat? that there should be used N42SH or something?


texts: Can You Identify This Deep Groove Ball Baring Bearing and/or Give an SKF Equivalent?

texts:
I am changing out my motorcycle engine bearings from the Chinese CJB brand to a high quality brand like SKF (Explorer range).
I am still waiting on a heat gun in order to remove the bearings from the engine case, and one bearing has been installed with it's codes facing into the blind seat.

I do know that its dimensions are 17x47x14mm, so it's a 6303 series.
All of the other bearings have a C3 fit, so I assume this will as well.
The other bearings all use PA66 or Glass-Fibre Reinforced PA66 cages, but they look quite different to this cage.
All other bearings are Class 6 Precision, so I am assuming this is as well.

Can anyone recognise the type of cage in this bearing? Do you know an SKF-equivalent suffix or prefix, or any brand's suffix that matches it?
Please let me know if you need any further information.
Thank you,
Nicholas


texts: How can I derive the KVL equation for the voltage-divider bias circuit of PNP BJT?

texts:
When I was studying the "Electronic devices and circuits - Conventional current" book floyd, I came across the following circuit and its KVL equations,

My doubt is when I apply KVL for the circuit (a), I end up with the $+V_{BE}$ in the equation if I trace the voltage drop in the clock-wise direction. But in the equation, it is $-V_{BE}$.

And for the circuit (b), I could not understand how they got $-V_{EE}-V_{BE}-V_{TH}$ in the equation?


texts:
Determine:

the distributed load $w_0$ at the end of D of the beam for which the reaction at B is zero
the corresponding reaction at C.

Please show me how to get the right answer to this question.:
$$\begin{gather}
R_1 = 1/2 \cdot w_0 \cdot 9 = 0/2 w_0 \\
R_2 = 1/2 \cdot 3.5 \cdot 9 = 63/4\text{ kN} \\
\text{For }B = 0 \\
\sum M_c = 0 \\
9/2 w_0 \cdot 8 - 63/4 * something \\
\end{gather}$$
Thats where I stopped I don't know what to do
May someone please show me the solution and explain to me his/her steps?


texts: Using a Threaded Rod and Internally Threaded Tube as a Piston Pump

texts:
Im looking for a low cost, high pressure pump with good flow/pressure control for an espresso machine (a lot to ask, I know).
My first thought was using a screw-driven piston. This will work, but Im wondering if I can forego the piston head and just use a threaded rod in a threaded tube.
I'm worried about fluid leaking around the threads; is there a screw thread equivalent to an o-ring? Any advice/thoughts are welcome!


texts: small touchscreen for handheld instrument

texts: I'm trying to find a small approx 2.5" touchscreen display that would be good for utilization in a small battery powered handheld instrument that has a frequently updating value that it reads.  e-ink/e-paper displays are low power but have refresh rate issues.  Other types of screens I'm finding use too much power to run off of a 9 volt for more than a day.


texts: Stainless steel wire mesh spot welded to a frame

texts:
Can anybody tell me how to make a similar welding job - that is to spot weld a thin stainless steel wire mesh to a stainless steel frame. What machine and technique  should be used to accomplish this job.

The time has come to replace the torn wire mesh.

Thanks in advance.


texts:
A common problem with ultra-high vacuum viewport windows is that often the window material deforms, into a saddle or Pringles chip shape. .

An engineer from a viewport  manufacturer explained to me that this can happen when the hoop stress around the window is not fully symmetric. If it were symmetric, the window would simply bulge or cup in the middle. That seems intuitive, but why would an uneven stress cause a saddle-like strain in particular? What is a simple physical explanation for this? So far, the fact that uneven stress in x/y directions cause different curvatures seems intuitive. What is also important is that glass is a very stiff material and cannot stretch (so volume/thickness is assumed to be conserved).

Here is a rough illustration of a stressed window in a metal sleeve typically found in experiments:

EDIT: the brazing pad (thick black) is where the metal sleeve (thin black lines) is brazed to the braze adapter (red lines representing another cylinder). The glass is hermetically sealed to the bottom of the metal sleeve.


texts:
I have thin weir, really just a sheet of metal with a smooth and straight upper edge. I want to know how much water will flow over this weir, when the water level on the higher side is a few cm above the edge.
I'm interested in the special case when the water on the lower side i below the level of the weir:

What formula describes this flow?
What are important caveats?


texts: In our Factory we have a Compressor which rates 660 CFM (Kirloskar Make), which is a VFD Compressor.  And next to compressor, we have a Receiver tank.  Next to Receiver Tank, we have a Dryer. The Consumption of the Total Plant is around 350-400 CFM. The Flow in the Dryer Outlet was around 400-450 CFM, whereas the flow is uniform for 4 to 5 min.  Then the flow drops down to 50-70 CFM and remains in that for 40 Secs. But still all the machines were in the same running State. And after 40 secs, the Flow in the Dryer Outlet was about 400 to 450 CFM.  Why this kind of low CFM is happening in the Dryer Outlet?


texts: I was told that PMMA is preferred over glass for windows in cold climates because of it's R-value being higher than glass.I wish there were a stick-on film made of glass! That could be used to cover PMMA windows, to eliminate the "scratch" factor if nothing else.


texts: How to push an endoscopic camera upto 20 meters in a horizontal pipe?

texts: I have a small endoscopic camera (custom made). I wanted to push the camera inside a horizontal pipe of dimensions varying from (25 mm to 65 mm ID). But the wire attached to the camera is not stiff enough to push the camera. After a certain length, camera stops moving (cz the wire coils inside the pipe). But I have seen Companies like Olympus etc., push their camera even up to 25 meters. I know that they have a special cover over the wire which is stiff and flexible for pushing the camera. How can I make a cover similar to that ? I have enquired many places but could not find a solution. Thanks in advance for your help.


texts: Which correlation for heat exchange in a partially adiabatic channel?

texts:
I'm modelling a heat exchanger inside a channel. Talking about convective one:
Geometry is simple, square of 1.5 cm but only one side exchanges heat.

The "problem" is that only one side exchanges heat with environment, the others are adiabatic.

At the moment I think best correlation to use is a simple internal correlation (e.g. Gnielinski), rather than an external correlation because this doesn't take into account boundary layer which can't grow up since there is the "roof" of the channel (characteristic length is no more a constant) making Nusselt number constant!

but I'm not sure about this... I've never handled a problem like this!

an example of my "fear":

  $Re_D = 61000 $, certainly turbulent flow
  using Gnielinski (internal flow correlation) I get $Nu_D = 125$
  and since $L/D=3000>>60$ the most of the pipe is in Fully Developed region >that ensure me to average Nu == local Nu:
  $Nu_{average}=Nu_D=125$
  while if I use an external correlation, at the end of the pipe, I get:
  $Re_L = 2e+8 $, certainly turbulent flow
  $Nu_L=0.0296*Re_L^{4/5}*Pr^{1/3} = 1.1e+5$
  $Nu_{average}=(0.037*Re_L^{4/5}-871)*Pr^{1/3} = 134384$

  this is the numerical proof about my doubt

Some additional data:

  flowing fluid is air at $ T=700 [°C]$ , $p=10 [bar]$ , $m=36.56 [g/s]$ ;
  these result in $\rho=3366.18 [g/m^3]$ , $u_{mean}=48 [m/s]$ , $\mu=4e-5 [Ns/m^2]$ , $Pr=0.734$ , $k=6.8e-2 [W/mK]$
  walls are ceramic-made: adiabatic ones have infinite thickness while the only one which exchanges heat is 1 [mm] thick
  channel is 50 [m] long and hydraulic diameter is 1.5 [cm]
  ambient is at constant temperature of 675 [°C], we can think to a fluid in phase-transition, so with a negligible thermal resistance, so don't worry about ambient...

EDIT: I want to share an online PDF which try to talk about it (here) inter alia at pagg. 46 and 264


texts:
I'm designing a solenoid valve for an automated irrigation project that I'm working on. After having looked at some designs, I have a question.

For most of the designs I've seen, the orifice is smaller than the pipe diameter. Wouldn't this reduce the flow rate? If this is the case and if I'm using such a design, do I make that opening bigger?


texts: How is an digital coherent receiver able to achieve 100 Mhz line-scan rate for detecting coherent light in the presence of incoherent light?

texts:
Recently, I read an October 2006 IEEE JOURNAL OF LIGHTWAVE TECHNOLOGY, article titled, High-Sensitivity Detection of Narrowband Light in a More Intense Broadband Background Using Coherence Interferogram Phase written by the esteemed Ricardo C. Coutinho, Member, IEEE, David R. Selviah, Member, IEEE, and Hugh D. Griffiths, Fellow, IEEE from highly respected University College of London.

  In this excellent article which is available publicly, it describes
  that the frame rate of  the scan is 150 microns per seconds in steps
  of 0.1 micron which is equivalent to 1500 seconds time duration for
  detecting the presence of a coherent laser light in an incoherent
  light background with averaging

  Page 3656 "A 10-μm scan length, corresponding to a 20-μm path
  difference range, was chosen, and this was scanned at a speed of 150
  μm/s in steps of 0.1 μm."

Please correct me if I am wrong about this calculation.

Then, tonight I read in the July 25 2016 Optics Express journal, an article titled "Optical digital Coherent detection technology enabled flexible and ultrafast quantitative phase imaging" by Yuan-Hua Feng et al. from Peking University Electrical Engineering Department. This article is currently open and availabe at the Optical Society Of America web portal.

Dr. Feng and his colleagues report that "we present a digital coherent time-stretch microscopy system that is capable of delivering ultrafast QPI of fixed cells in a scanning rate up to 100 MHz without averaging" . In addition, these researchers state that "bebefiting from a digital coherent receiver, we can retrieve intensity and phase information with high quality simultaneously. Because of the improved Signal to Noise (SNR) of the  proposd imaging method, the amplitude and phase images were processed without averaging. So we can achieve an effective line-scan rate as high as 100 MHz."

Both of these papers are very important to use because we wish to protect pilot's vision from increasingly sophisticated laser pointers on the ground 150 meters away aimed at the Boeing 747-787 cockpit windows. If we can detect the presencen of coherent laser light in an incoherent background within 10 milliseconds of arrival , we can then activate an electro-optic shuttter to block the laser ray and then funnel the recovered incoherent light signal to an Planar(@TM) transparent display.

My question is which of the two papers is most effective for accomplishing the aforementioned purpose. In addition, how is the digital coherent receiver able to achieve line-scan rates as high as 100 MHz? Please use equations to explain this if necessary.

Any help is greatly appreciated.


texts: What is the force needed to exert on the piston for a certain extrusion rate of a syringe tube?

texts:
I am trying to design a syringe pump for microfluidic extrusion uses. I have a 5cc syringe tube that I will use as the cartridge. We would be using it to extrude a variety of materials so the viscosity is uncertain.
I want to know what's the best way to find out what the maximum linear force is needed from the piston to deliver a certain extrusion speed of certain materials.

I was thinking maybe doing an experiment with different materials in the cartridge would be the most straight forward but at this time no one is allowed back in the lab...
Is there a good theoretical way to find a ballpark range of force that might be needed (so I can choose the right motor)? Maybe the Poiseuille Equation?

I am very new to this. Thanks for any advice!


texts:
I am using Bernoulli's equation in order to calculate a relative area between two points in a pipe. Problem is, based on the solution I have obtained, I end up with imaginary numbers and not sure what to make of this practically. Here is my math:

$$\begin{gather}
P_1 + \dfrac{1}{2}\rho v_1^2 + \rho gh_1 = P_2 + \dfrac{1}{2}\rho v_2^2 + \rho gh_2 \\
v_1 A_1 = v_2 A_2 \\
\dfrac{A_1}{A_2} = \sqrt{\dfrac{v_2^2}{v_2^2+\dfrac{2}{\rho}\left(P_2-P_1\right)}}
\end{gather}$$

I know my velocity at location 2, density, and pressures. I have no change in height so I got rid of third element in Bernoulli's equation. I am trying to obtain an area ratio between both points.

It is very possible in my model that I will have a low P2 and high P1 leading to a negative denominator and an imaginary solution. I feel like I am missing something practical or mathematical here that is simple but my mind has drawn a blank.

As a side note, I am assuming non-compressible airflow. Cannot assume laminar flow.


texts: how does one obtain motion in the theta and phi direction with motors?

texts:
I'm not a mechanical engineer,but I'm guessing this is something that is well known by MEs. Say I have a rod and I want to move my pitch one direction, and my azimuth the other direction. How can I do this to get a full spherical direction capability for the rod? How many motors does it take, and  What is the correct placement of motors/gears? A picture or video might help.
Thanks.


texts:
I'm mechanical engineering student who want to construct 3D printer. I have a problem choosing right and cheap material for bed. Bed will be big for a 3D printer, around 700mm x 500mm. I want to print PLA, PETG, ABS, PC. Bed MUST be heated, and i sensor for height is also necessary.

I googled it a lot, I have been checking out forums (even here), but I still don't know what to choose. I just know i don't want to have borosilicate glass, because it is too heavy and bed will be moving up and down along Z.

This is my list of material for bed:

PEI great surface, even here i think this is what everybody is suggesting. These are sheets, so I will need a base to put it on. What should be a base? Alu is great for machining but it has really big temperature coefficient. Do you think zerodur is OK? Does anybody has any experience with it? Can I buy it in EU? Zerodur

Phenolic laminated G10-FR4 this is composite that MarkForged uses it on their printers. I had an opportunity to work with Mark 2 and i like it a lot, but glue is really necessary for good adhesion. Is it because Mark2 does not have heated bed? I saw it has a lot of different variations of material and not everything is good for bed surface.

Coropad - Tom's 3D really praised it. It is magnetic, so you can peal it of base. But what can i use for base? Regular S235 steel or C45? Can i use anything lighter and still magnetic? Does anybody uses it here?

This is my list, I'm choosing between one of them. Do you have any other materials that you recommend? What would you choose. IMO this is is critical component of 3D printer, while we know that most of mistakes on print is because of first layer adhesion. Hopefully you'll help me choose right surface :)


texts:
Honeycomb structures are made of top and bottom shells and honeycomb geometry at core. In terms of bending load, maximun normal strains take place on top and bottom hence, sheet parts can support them as expected.

However maximun shear strain take place at the center of the cross section which coincide honeycomb structure. As I know, stiffness of the honeycomb very low even negligible. So, what is the idea behind shear stiffness of a honeycomb structure?


texts: How to determine the angular velocity of the platform as a function of motor rotations per second?

texts: Hello all of you engineering geniuses. Awhile ago a very talented individual on here helped me work out the conceptual mechanics of this design. As you can see from the model, there is a lead screw assembly that pushes a rod forward which elevates the platform. The total travel is 0° to 60° (theta). The equation shown is the linear travel of "Xblock" as a function of theta. If you were to plot this function, you will see it is not quite linear. The terms, Wp, Ht, Hp, and Lrod are all constants. I am trying to determine an equation for angular velocity of the platform, which is actually decelerating as Xblock moves forward at a constant velocity. Of course the linear travel is easy enough, simply the rps of the motor x lead x time. The lead is 8mm but the lead and rps can be treated as constants. I could simply take the derivative of function, but it's a function of position as a function of another position, not time, so I'm not entirely sure where to go from here.


texts:
I want to attach a 12 toothed spur gear with a bore diameter of 6mm onto the shaft of this motor (6mm diameter). How would I go about doing this? From what I see, the shaft is smooth so is my only option to find a gear with a set screw? Or is it sufficient to attach a gear with no set screw and simply rely on the friction of the bore? The torques will be low.

Are there any websites that one would recommend for finding gears like this? I'm finding it impossible to find gears with a module of 1.0, bore diam. of 6mm, and a thickness of less than 20mm to fit onto the shaft.

Any help would be greatly appreciated.


texts: How to get my product IEC tested and certified

texts: What is the procedure to get proper IEC certification for a product? What is cost of such action? I am talking about, let's say, a fan or an oven (if size and complexity of product makes any difference)


texts: Is thermodynamic data of fresh water a good approximation for saline water?

texts:
I am currently working on desalination project for my final year. The design is based on flashing of hot liquid in low pressure vessel and then condensing the extracted the steam to produce pure water.

The problem I am facing is that there doesn't seem to be any thermodynamic data (under saturation dome) available for saline water. The need for saturation data is because I need to calculate the required mass flow rate based on daily desalination goal.

For example, if the goal is to produce 100 L/day with average sunlight of 8 hrs, then desalination rate must be 0.0035 kg/s. If I know the quality (percentage of steam produced) of the liquid gas mixture, I can easily calculate the mass flow rate of saline water corresponding to desalination goal.

The only data I could find related to this problem was from a MIT resource Thermophysical properties of seawater, but unfortunately it only provides a single value for enthalpy at any given saturation temperature or pressure.

Right now, I can see only three options:

Use steam table, and consider the values an approximation and incorporate the error produced in my design by slightly overdesigning
Consider the enthalpy of seawater (from MIT resource) as enthalpy of saturated liquid (i.e. $h_f$), and enthalpy of vapor (from steam table) as $h_g$ and then perform my calculations
Thirdly, I could take the enthalpy of seawater (from MIT resource) as the value that is halfway between $h_f$ and $h_g$ (from steam table), and then calculate the approximated value of $h_f$.

$h_f=$ Enthalpy at saturated liquid line;
$h_g=$ Enthalpy at saturated vapor line

Any help/guidance in this regard will be highly appreciated


texts: How do I fix a technical drawing pen with a bent needle?

texts:
I accidentally dropped my Mars Matic 0.5mm and noticed that maybe I broke the needle. I was having a hard time writing with it so I tried to clean it, and while cleaning I accidentally bent the needle part. After all the trouble that I experienced I manage to straighten the needle very carefully.

Right now it's working fine but I need to shake it rigorously. I am planning on buying a new one because of the hassle of using it but there is also a side of me that says I should not buy a new one.

Is there any other way that I can fix my pen? It's slightly bent now but by shaking it rigorously it can still write.


texts: Latest methods for noise insulation for walls and ceilings?

texts:
All I know is for noise insulation, building a party venue for example, inner wall spacing  should be about 20cm. Though I don't see how that helps with anything but one frequency and It's harmonics. But im not buildingthe venue from scratch, so I want to sound-insultate the walls  by adding panelling internally.

There must be some good physical solutions akin to electronics high/low pass fiters?  I saw one with a layer of wood and either rubber or accoustic foam. The absorption was only 10dB.

What would be a standard modern solution to reduce noise by 40+ dB? 100hz -2khz roughly will be the biggest problem I think


texts:
I am using eccentric spacer nuts to create a tight fit between wheels and a rail of a linear sliding mechanism. (Expand the product description in the link to see a picture of it in use).

They aren't actually nuts: they have no thread. But the hexagonal part of its exterior allows the spacer's off-centre hole to be adjusted with respect to the external cylindrical section with a spanner, thereby positioning a shaft going through it relative to the structure holding them.

Are there alternative mechanisms for adjusting the distance between opposite wheels? They are very effective, but are £2 per piece from the UK, and it really adds up. They only seem to be sold by suppliers of the open-rail and v-slot systems, so I'm hoping, either:

These accent rich spacer nuts are known as something else in other systems, at a lower price, or...
There are other mechanisms that achieve the same.


texts: How to obtain the spectral reflectance of a whole object?

texts:
I am interested in the colours of an object in a natural light environment. Specifically, I am interested in obtaining spectral reflectance data (i.e. the particular light wavelength(s) reflected of an object) from an object as viewed by a biological eye. I know it is possible to obtain spectral reflectance data with a spectrophotometer. However, I am more interested in obtaining spectral reflectance data of the whole object. Theoretically, one could do this with a spectrophotometer if the spectral reflectance of the object is measured painstakingly point-by-point. Understandably, this would be a hassle, not to mention the practical problems that will need to be overcome.
Are there apparatuses or a combination of apparatuses and methods that could do this more easily?
P.s. I am not a student of engineering, so forgive my potential ignorance.


texts: How to control a roller gate using 2 motors - when one fails the other works

texts: There is a gate which is to be controlled by 2 motors, but one should work and when one fails the other should work. AND THE CONTROLLER USED IS A PLC


texts: Identification a Symbol for P&ID's Standards

texts:
i have a question regarding on PID standards ISO 14617. Below is the attached symbol graphic, i seem cannot find anywhere what actually this symbol refer to from standards that i have looked up; PIP, ISO, DIN and BS.
I would appreciate if anyone could clarify this to me and also it would be great to have a website or anything on where i could refer for more information about standards.
Thank you
so here i attached the diagram, i did lookup to https://www.edrawsoft.com/pid/images/pid-legend.pdf
it says triangle separator,
so here is the diagram that i refer to


texts:
A Spherical buoy has a diameter of 2m and weighs 3kN. It is designed to be used in a variety or circumstances by it being floated in water and anchored to the floor with a chain.
Draw the free body diagram and determine the following given thta the volume of a sphere is,

$$Volume =\frac{\pi D^3}{6}$$

The upthrust or buoyant force (Fb) in sea water.
The tension in the chain (T)

Assume at 4Degrees the specific gravity of sea water is 1.042, g = 9.81m/s^2

1.

Equation

$$Pf Vd g$$

$$Fb = PfVdg = (1.042kg/m^3)(4.188m^3)(9.81m/s^2)$$
$$ = 42.8N$$

Is this correct? Trying to learn this. I think it is correct. But wanted to check so i understand how to do it correctly.

Then i am going to find question 2.


texts:
I’m designing a machine which has an actuator on a carriage sliding on two round linear guide shafts. I got an idea of transmitting electricity to the actuator through the shafts. There would be carbon brushes on the carriage against the shafts.

The problem is the selection of the linear bearings. The carbon brushes will wear and some graphite residue will stick on to the shafts. I wonder which bearing type would be best here. There are ball circulating bearings, plastic sliding bearings and self lubricating bronze bushings.

Some self lubricating bushings use graphite as lubricant so that seems like an obvious choice but I’m not sure how they would work here. On the other hand plastic sliding bearings like Igus claim to work even with sand on the guides. The ball circulating bearings seem like the worst choice in my opinion.

So which bearing would be best in here?


texts: What "Soft PLC" platforms are there out there

texts:
The Beckhoff TwinCAT system allows me to put a box on a DIN rail which can act as  a realtime PLC controller (programmed in Ladder or SF) while allowing a Windows instance to run in the hardware at the same time.  Hence a Windows program (eg a UI written in .NET, or a comple high level algorithm) can make API calls to exchange data with the realtime PLC program.

Are there other platforms out there which offer a similar sort of facility?  And how do they compare?


texts: Drawing the shear and bending moment diagram of a 2D rigid frame

texts:
I am taking a civil engineering course that we are constantly asked to tackle questions that are not really covered in the course. I have been looking for suitable reference materials but with no success. Here is one of the questions that I am stuck at:

  Find the shear and bending moment diagram of the following rigid
  frame:

I have tried working out the forces but they seem to be wrong after checking with a free program called "2D frame analysis."

How should I approach this problem?


texts: What steel to use? What thickness and width? What angles to use?

texts: I am trying to develop my own spring steel version of a carbon fiber running blade that you might see in the paralympics.  Except mine is for someone who still has their foot/leg.  Nothing like that exists and out of necessity I am trying to develop one that is similar and I think i might be able to do it using a less expensive material too.   I really need help calculating what steel to use, thickness, width, angles, etc.  Carbon fiber is ideal but very expensive.  Would spring steel work?  Any concerns with that choice other than a bit heavier?  It would have to be formed in the shape of a "J"This would need to support a 215 pound person walking, running etc.  Any help is greatly appreciated!


texts: I don't understand sometimes what numbers actually mean in some naming conventions of many types of motors. Is there a good repository of knowledge regarding this subject except for those boring books?


texts: Recommended compressed air source and location for separate air compression system

texts:
I am investigating what would be the most appropriate compressed air source (fan/blower/compressor) for designing a separate air compressor system.

The information is as follows:

the compressed air would be supplied to the lens of an industrial sensing instrument, which is mounted onto a pipe leading into a boiler's furnace
there are 12 instruments on each row and there are four rows in total (first row starts at 20m and there is an increase of 5m per row).

Purpose:

to provide sufficient pressure in order to prevent accumulation of dust on an instrumentation's lens
to provide sufficient flow to keep the entire pipe free of contaminants in the first place

Demand requirements:

flow (800 m3/hour) for all 84 instruments (100 m3/hour for one row of instruments) (8.6 m3/hour for one instrument)
pressure (40 mbar)

I know that the pressure demand is very little, it simply needs to be slightly above the furnace pressure. However, my concern is that the fans we have been using have not been able to provide sufficient pressure. Meanwhile, the flow is quite large.

Therefore, I am contemplating between a blower (more powerful fan) or a compressor (not sure if an air receiver would be necessary).

Which one would be more suitable (for both 100 m3 per hour and 800 m3/hour)?

What are the pros and cons of either (in terms of cost and space required and efficiency).?

If a compressor, which type of compressor (positive displacement, rotary, reciprocating) would be suggested?

Also, the duty cycle is 100% (all the tube needs to be cleaned at all times). If a compressor is used, is a receiver necessary?

How many instruments could be fed with one compressor?


texts: Model Predictive Control and Numerical Integration Schemes

texts:
When simulating systems of ODEs, I'm used to always using a numerical integration scheme to propagate the equations forward in time, such as simple Euler integration or Runge-Kutta methods. However, with model predictive control (MPC), every textbook I see gives the following form for propagating a linear system forward in time:

$$x(t+1)=Ax(t)+Bu(t)$$

However, if we see how this system evolves in time using arbitrary inputs $u(t)$, the results are extremely inaccurate. I would have thought that MPC would incorporate some form of integration scheme while performing the control optimization. So, for example, if we consider Euler integration we would have,

$$\dot{x}(t)=Ax(t)+Bu(t)$$
$$\frac{x(t+1)-x(t)}{\Delta t}=Ax(t)+Bu(t)$$
and then our dynamics used as linear equality constraints in an MPC algorithm would be given by,
$$x(t+1)= x(t) + \Delta t[Ax(t)+Bu(t)]$$

However, I've never seen a form like this used before. I know I must be wrong, but I don't know what I'm missing. Any clarification of why general MPC algorithms use $x(t+1)=Ax(t)+Bu(t)$ without any integration scheme would be much appreciated.


texts:
I’m trying to understand the effects of  a bike’s trail on its steering stability. There, however, is a concept of slippage velocity of the tires during steering of which I cannot make heads or tails of.

Book- Motorcycle Dynamics

Author- Vittore Cossalter

Page no. 13-14

1st Question: Why should the final resultant velocity of the front tire be in the same initial direction of motion ? Shouldn’t it be in the plane or rotation of the front tire, now that a steering input has been given?

2nd Question: What is this slippage velocity ?

I’ve tried Google as well. But there isn’t any information on this topic in simple words.


texts: How does pressure treatment affect the mechanical properties of lumber?

texts:
Pressure treated lumber is specified for many exterior applications because of its resistance to insect damage and fungal rot. But how does it compare to untreated wood, mechanically?

For example, consider a rim joist supporting the ground floor of a residential structure with a pier and post foundation. If the joist has been damaged by rot in a location that is impractical to fully protect from exposure, I might be tempted to replace the joist with a pressure treated member of the same nominal dimension (in addition to proper flashing) for added protection in that location.

Since this is an existing structure, by far the easiest approach is to use a member with the same dimension to replace the rotted joist. However, this relies on the new member meeting the same load-bearing requirements as the old member.

Building codes should provide enough wiggle room that in this particular example, there's not much of a safety concern for the homeowner. After all, the rotted joist had not failed, and it would definitely have less strength than the member was originally rated for. In practice, treated and untreated members may be manufactured from different wood species with different mechanical properties to begin with; for the purposes of this question, assume the species is constant.

Does pressure treatment result in a member with more or less strength in tension, compression or torsion? Does it affect the durability of the wood* in ways not related to rot or insect damage?

* Not the fasteners; that's a different issue that's pretty well-covered online. See this page from Simpson, for example.


texts:
I wish to calculate the air flow in cubic meters per second of a system that is not exactly a jet engine, but seems close to it, mathematically speaking.

The data available to me is the following :

the engine rotates at 3600 rpm
the propeller is 40cm in diameter and is equipped with 16 blades, 5cm deep (but I don't know the pitch)
the propeller air inlet is 20cm in diameter and the air outlet is 9cm in diameter
normal temperature and pressure conditions (20 ° C - 1 atm).

I have only basic knowledge in maths and physics and I don't know where to start from there. As I am only looking for an indicative result, simple formulas could certainly help me.

I would be happy if someone could point me in the right direction. Thank you very much in advance.


texts:
I am making a device for measurements. I would like to measure the distance within accuracy of 1 mm. Range could be 2 cm to 15 cm . I looked at Proximity Sensors but the readings displayed by these sensors are not steady.

I wish to measure the thickness of the plate (carbon steel). The two sensors will be mounted on a structure. The sensors will give me the distance of the surface from the sensor. Then I will calculate the thickness of the plate.

What are possible types of low cost sensors I can use?


texts:
Consider we have a second order system (plant) described by the following transfer function:

$$ P(s) = \frac{b_0}{s^2+a_1*s+a_2} $$

which is controller by a PD-controller:

$$ C(s) = K_p+K_ds $$

In order to study the impact that the external noise has to the system, I have come across the so called noise sensitivity function which is described by the below equation:

$$ N(s) = \frac{C(s)}{1+P(s)C(s)} $$

However, deriving $\ N(s) $ produces an improper transfer function with degree of numerator being $\ 3 $ and of denominator being $\ 2 $. This results, for example, to the imcapability of obtaining a step response in order to study the behaviour. Is the definition of the noise sensitivity function wrong or am I missing something ?


texts: How do we solve a rigid body indeterminate structure?

texts:
In statics we consider the force deflection constraints (i.e. assuming the structure to be flexible) to generate equations in order to solve the extra degrees of indeterminacy. So, basically if we consider a rigid body that does not produce any deflection how do we get the reactions at the supports? Can they be determined? If not, basically what does it mean from an intuitive perspective?

Say, now all the 3 reactions are due to a pin support. This way, in statics we equate the deflection caused by R1 to the deflection caused by the pair of 100 pound loads. This gives us R1. But in the process we are assuming the structure to be elastic. If the body is rigid, in this case can R1, R2 and R3 assume any values as long as the body is in equilibrium? But how is it possible?


texts: Will screed on plywood do instead of beam and block, to replace a floor?

texts:
I'm gutting and redoing an older house (early 20th C, ordinary suburban terrace house, London UK).

I'd planned beam and (dense) block for the upstairs structural floor, for a few reasons, and already got structural calculations for load spreading on the old foundations for the extra load this would involve.

The beams would be supported on engineering brick in some places, or on the stiffened flanges of 203x203x46kg beams across openings.

The planned floor above would then be neoprene pads with battens resting on them, and floorboards on those (for a nice effect and also ensures space for services and exceptional acoustic isolation - almost "box within box" by design, stopping most vibration through floors and around through the terrace walls). The wider design takes care of acoustic isolation of the walls which isn't relevant here.

My reasons are a bit diverse, in no special order - beam and block guarantees no squeaking underfoot, guarantees very high quality acoustic resilience, excellent fireproofing, and makes it dead easy to support a wide (4m) span or to support battening anywhere needed. Also it's quick,cheap, and easy, no pump either, just some heavy lifting.  I know this is probably way way overkill, but I'm comfortable with that and don't consider it a factor in any decision.

The final, and perhaps most important, reason is that the building is space challenged. By which I mean, I'm fighting for every vertical cm I can save on the underfloor thickness. Every cm is a cm less of ceiling height, and also either a steeper or a larger stairwell. I can afford a couple of cm thicker for the 1st floor structure, but more than about 5-8cm would really hurt due to knock-on effects. Beam and block gets my structural floor thickness down to 150mm and nothing else except steel can do that, and I need that space badly.

So I had this all sorted out. But the job got passed to a different engineer in the same company, and he's urging a different design - engineering wood beams with 22mm plywood and 60-80mm of poured screed with mesh.

His reason is load and age. He agrees the original plan will be fine, and the work done on walls and load spreading will be ample to accommodate the extra weight both within the walls and on the original foundations, but from what I can gather its a feeling that the building was originally designed for timber floors and just wasn't designed to have this kind of extra load or structure. He also cites building cost but I think that's more like a carrot dangling on a string - its a nice thing but in the scheme of things any cost difference will be tiny and I discount it.

He agrees that screed (1800kg/m3) and full-on concrete (2400 kg/m3) are similar enough density to use the latter instead of screed if I wanted, and I feel slightly pressured, although if I say no, it will be no.

Apart from considering whether or not to accede to his desire to lighten the load, my other more serious issue is that the depth would go up a lot. The original plan's depth would be 150mm floor beams, plus pads, battens and flooring. A version done as he suggests would be 200mm engineering timber beam, 20-25mm plywood, and 60-80mm screed/concrete for a total of almost 300mm - almost 150mm more... and all to save at most 110kg/m3 (beam = 250kg/m3 max, 75mm screed = 135kg/m3 min) that we've already calculated our way around anyhow. It's just not worth it as far as I can see.

Before I say no, is there anything important here from a purely structural engineering, rather than general home improvement, perspective that I might be missing or need to take into account, when I consider this new option against the existing one they have presented?


texts: How do you calculate the chain tension required when compressing bulk material over a conveyor?

texts:
Bulk material is conveyed over a slat conveyor, and the material is leveled with overhead rollers while being transported in the conveyor to maintain an even material height. Most of these "levelers" operate at a surface speed that is much faster than the speed of the conveyor. However, one particular overhead roll serves to compress the material slightly and feed a machine downstream, and it operates with a surface speed close to the conveyor speed.

This particular roller operates at a constant speed, but the conveyor does not. As such, there are times when the roller has a faster surface speed than the conveyor, but other times when the roller operates more slowly.

Is there a way to calculate the effect of these external devices on the force or energy required to operate the conveyor? I am particularly worried about this last roller, since it seems to cause the most resistance to motion. I have been unable to find even empirical information on the effect of these rollers in standard chain pull calculation guides.


texts: Measuring the temperature of gasoline while conducting experiments over a temperature range

texts: I am building a device to heat and measure the temperature of a small vessel (double boiler) of gasoline over a range of temperatures say -10F to 120F. I will be measuring the capacitance across a homemade probe to figure out the dielectric constant over this temperature range. What would be the best way to accurately log the temperature while simultaneously measuring the capacitance. Currently, I will be using a 555 timer and microcontroller to measure the capacitance so the same microcontroller could take an analog input from a temperature probe. Would a thermistor work best in this situation? Can I put a thermistor directly into gasoline safely? Would it be better to consider a thermal imaging approach?


texts: What is the *typical* quantity (in kg) of uranium-235 present at a given moment in a nuclear plant?

texts:
What is the typical quantity (in kg) of uranium-235 present at a given moment in a working nuclear plant?
How does this compare to the typical amount of uranium-235 in a typical nuclear bomb (typically one kg of uranium-235)


texts: Does notching the corner of an angle brace member help or hurt when shear lag is present?

texts:
Does notching or cutting out the corner of an angle brace distribute stress better along the flange of a member with shear lag or reduce the stressed edge of the flange's ability to resist deformation?

Previously, user CableStay had illustrated Shear Lag concept in a bolted angle iron member very well.

My question then asks if it is possible to better distribute the stress of the uniform stress closer to the end of the member by notching or cutting the corner of it.


texts: There is a steel plate with length of 26.5cm (10.4 inch)  and width of 4cm (1.57 inch). the steel plate is attached on one end, at the other end there is a load of 30kg, what thickness should be the plate so it will not bend ?


texts:
I am looking for help on the following:
a) Given the system shown in the figure below, derive the steady flow energy equation from first principle.
b) Again using first principles, show how the energy equation would change for the case when the system is unsteady.

I am trying to learn this for upcoming exams.
But i can find nowhere on line which breaks down this sort of question. Which means i cant understand how to complete these sort of questions.
Can anyone help me complete this question please? So i can get an understanding of these types of questions.
Thanks


texts: What are the meanings of the second argument to the convolution?

texts:
I was trying to understand the convolution better and its mathematical properties and interpretations in engineering (specially in the context of computer vision). Recall the convolution:

$$ s(t) = (x * w)(t) = \int x(a) w(t-a) da$$

the first argument (to the convolution) $x$ is usually called the input but the second argument $w$ (to the convolution) is usually called the "kernel". However, in computer vision and convolutional neural networks, the second argument is usually called a "template" (maybe the image of an edge or a wheel, or some part of an object). However, in other areas, I think is signals and systems, its usually called a "filter".

As a computer software engineer, I believe that naming is extremely important because it gives us the power to think about specific concepts. Having bad names can lead to sloppy thinking. Therefore, I was assuming that these technical names probably were chosen with these ideas in mind. Does someone know or understand why these names have been used to the second argument of the convolution?

The specific names that I am aware of are:

Kernel (from pure maths?)
Filter (signals and systems?)
Template (Computer vision/ Machine Learning)

Not sure if I am missing any, but I'd like to understand these naming better and possibly (hopefully) understand intuitively better what the convolution operator does and its interpretation in engineering and mathematics.


texts: Recommendations on impermeable high temp material selection?

texts:
I'm currently looking for a tubing that can withstand 350F+, have a shore rating of less than 80A, and must be impermeable or very close to it.

I've found a tubing called "Viton" which is close but not quite impermeable; are there any other materials offered out there that fit these specifications?


texts: I'm involved in purchasing a set of mixers for a crude oil storage tank. The tank volume is around 98,500 cubic meters. The main purpose of the mixers is base sediment & water control (cleaning).  Different vendors have offered different number of mixers with different power requirements. I need to have some calculation or references to compare these offers.


texts: Chemical Engineering Process Analysis - Process Flow Calculations using linear matrices

texts:
I am doing a process flow question and trying to calculate the grams of $\text{C}_{10}\text{H}_{14}$, $\text{C}_4\text{H}_6\text{O}_3$, and $\text{C}_{12}\text{H}_{16}\text{O}$ produced during a reaction. 134 grams of $\text{C}_{10}\text{H}_{14}$ and 134g of $\text{C}_4\text{H}_6\text{O}_3$ were used as reactants. The reaction also produced 68g of acetic acid. I defined my stream variables in terms of the elements ($\text{CHO}$), since the reaction is of unknown stoichiometry. I created a system of equations as follows, where $x$ is the grams of $\text{C}_{10}\text{H}_{14}$ produced, $y$ is the grams of $\text{C}_4\text{H}_6\text{O}_3$ produced, and $z$ is the grams of $\text{C}_{12}\text{H}_{16}\text{O}$ produced.

For $\text{C}$: $12.98 = 10x/134 + 4y/102 + 12z/176$

For $\text{H}$: $17.347 = 14x/134 + 6y/102 + 16z/176$

For $\text{O}$: $1.67 = 0x + 3y/102 + z/176$

I combined these into linear matrix equation
$$\left[\begin{matrix}
\dfrac{10x}{134} & \dfrac{4y}{102} & \dfrac{12z}{176} \\
\dfrac{14x}{134} & \dfrac{6y}{102} & \dfrac{16z}{176} \\
0 & \dfrac{3y}{102} & \dfrac{1z}{176}
\end{matrix}\right]
\left[\begin{matrix}x \\ y \\ z\end{matrix}\right] =
\left[\begin{matrix}12.98 \\ 17.347 \\ 1.67\end{matrix}\right]$$

Given that $Ax=b$, and $x=A^{-1}b$, I then took the inverse matrix of $A$ and multiplied it by the matrix $b$ (in my calculator). This resulted in the solution that $x = -16.46$, $y= 18.7$, and $z=197.64$. While this does satisfy the equations, the textbook gave the answers: $x=1.6$, $y=22.9$, and $z=175.5$, which also satisfies the equations, and makes sense unlike my answer where I have a negative gram amount produced.

I believe my error has something to do with setting a basis, though I'm not sure what that means. Also, the book has the same equations in its solution that I have, but the answer comes out differently (it does not explain how the three equations were solved, other than that it was simultaneous.)

How do I get the correct answer and where is my mistake? Also if you could explain setting a basis that would be great as well.


texts:
In short, the question is: How the EPC affects an automatic transmission?

I'm planning to build an automatic transmission controller module, TCM for 4F27E Ford transmission. So far I haven't found an aftermarket transmission controller that would work for this transmission, hence this project. For now I would like to raise a discussion about EPC. I will then write a control software for the TCM based on what I learn about EPC and other solenoids.

In an automatic transmission, EPC solenoid controls the pressure in the hydraulic circuits affecting the line pressure. There is a steady state pressure, that is the amount of pressure required to hold applied clutches and bands without slipping after the shift has completed and for steady use. The line pressure controls the shift, too low pressure will cause soft and long shifts; too high will cause harsh shift.

Great theory, but...

Question: does the line pressure affects the torque converter? The 4F27E (and similar) has a dedicated solenoid to control the torque converter clutch (TCC) but normally is an on-off solenoid, is it possible achieve the increase of speed with fairly constant RPM, commonly observed in automatic transmission, by varying the EPC? (or this is purely done by the torque converter characteristics?)

Continuing the question: as the theory says, high pressure causes harsh shift. Does the TCM need to action on the EPC to reduce the line pressure to the required level before gear shift?

More: The line pressure varies with the engine RPM (or more precisely, speed of input shaft connected to the hydraulic pump). Does that means the line pressure is function of RPM x EPC x temperature, or there are other variables?

Cheers.


texts:
Recently I was thinking about home improvement, and one idea that is haunting me is that I could use some kind of refrigerator for gaming consoles and laptops.
The obvious benefit is that it maintains a constant low temperature. Also, the doors usually can be closed firmly and it won't let dust come inside, so there isn't any need to disassemble and clean hardware. That is a good thing in long term. Despite it makes airflow less intensive, according to my understanding it should not be a problem, as all that is needed for hardware is cooled air, not new air.
And whenever I get what I consider a good idea, I usually stop for a minute and ask myself a question "why doesn't this exist yet?". So there are definitely big-scale expensive enterprise servers which could possibly use the same approach to reduce maintenance effort, but that is not the case. So the disadvantages I can think of is that refrigerators are just not designed to cool a source of constant heat for a long period of time and (probably) will break quickly. Another problem that came to mind is that refrigerator boxes tend to generate condensate and it might be harmful for hardware.
Am I correct with my assumptions, or is it not that crucial and are there in fact similar solutions?


texts:
I was wondering if there are any window mounted split air conditioners in US market or anywhere else - One in which compressor and radiator hang out of the window and only evaporator is inside the room. I was able to pull up many patents from as early as 1938 with same idea but don't think a commercial product exist. Any thoughts why it could be so?

Here are some patents and more mentioned in their reference section:
https://www.google.com/patents/US6568201
https://www.google.com/patents/US2268451


texts:
I'm challenging my optical design skills by coding a ray-tracing Python script. I know that many good packages exist out there, but I'm trying not to skips steps by building everything on my own.
For simplification purposes, the inputs of the script are :

pupil specification : entrance pupil diameter or object numerical aperture
field specification : field angle or object height
shape and position of the surfaces (including the stop)
wavelengths

In order to compute the direction cosine of the rays at the object point and start tracing, we need to know the location and diameter of the entrance pupil. The entrance pupil's location is, for a given object point, where the chief ray crosses the optical axis as seen from the object.
How can I translate this in Python in order to compute the direction cosine at the object point?


texts: First principle derivation for torsional constant

texts:
For torsional constant, analytical formulas are available for some standard steel sections as shown in this wiki page.

But what about arbitrary shapes? How can I obtain the formulas for torsional constants? If no such formulas are available, are there any first principles that I can use to deduce the approximate formulas or FEM calculation for torsional constant?

Note: a related question about the FEM formulation of torsional constant is being asked here.


texts: Temperature control with interacting PID loops

texts:
I want to control the temperature of a steel mold about 300 mm square by 1000 mm high. The mold has ten electic cartridge heaters installed in it. There are ten corresponding thermo-couples, one near each heater. Each heater/thermocouple pair is a zone. The simple solution is to use ten PID loops, one for each zone.

The problem is that the zones interact, and heat from one zone's heater heats the other zones too. The closer the zones are to each other the more they affect each other. The output of each PID loop will be a disturbance to each other PID zone. The specification is to control each zone to $\pm 1 {^\circ} C$.

A control system using proportional controllers (P term only) in each zone was tried. The temperature of each zone oscillated, far exceeding the $\pm 1 {^\circ} C$ requirement. The system would never settle. This isn't suprising with strict proportional control. I expect that a PID control would work better, but I don't know what the interactions will do.

Will multiple interacting PID control zones stabilize? Is there a better approach to controlling the system?

Edit: All zone set-points are the same temperature. They all need follow a linearly increasing temperature profile from $20^\circ C$ to $180^\circ C$ over twenty hours. The internal cavity of the mold has a very irregular shape.


texts: Line balancing - How far do companies go?

texts:
I understand that the concept of line balancing is such that each station takes exactly the same amount of time to process one unit. Clearly, this is an idealization and real manufacturing plants will have bottleneck stations and underutilized stations.

I'm wondering if someone has an idea on what numbers are typical in various industries? For instance, if there is a 10% take difference between the slowest and fastest stations, is the line considered balanced enough?


texts: Why does compressed air energy storage use intercoolers?

texts:
Why do CAES systems have intercoolers after every compression stage?

Isn't it a waste of work, since the air will cool anyway in the storage cavern?


texts: Which container orientation, if any, can hold more weight?

texts:
These are cross sections of identical shipping containers, except one is rotated 45 degrees. The cross sections are squares, 3 meters to a side. I drew dashed lines to show where they're suspended by a crane.

Note also I put a cross beam inside of them, connected at the corners.

In general, which orientation can hold more weight? Does it matter?

(If you need more specifications, I can make them up. But the idea is that they're the same thing, just rotated 45 degrees, so I didn't think the exact width of the walls and beams mattered so much.)

The purpose here is to make a very heavy-duty shipping container than can hold bulk ores, which can be very dense. (Imagine lead ore, granite, etc.) That's why I put a cross beam, to help the container stay rigid. So I want to know the most efficient way of orienting the container.

Note, I don't know what tags are good for this question. I looked for something along the lines of "abstract". Feel free to help me with tags.


texts: What determines the maximum possible slope of rail transportation (without rack)?

texts:
(Disclaimer: To make things clear I'm talking about adhesion railways and excluding rack railways as those are an entirely different technology and requires specially equipped vehicles. Also I'm looking for examples as how this is engineered.)

I was surprised recently as I visited the Wutachtal railway in southern Germany. A particular section of this railway makes extremes detours with multiple viaducs and tunnels (including a circular tunnel) in order to climb 231m while having a gradient of only 1%.

According to the museum's explanation, the gradient of 1% was required because they wanted to allow heavy military freight trains to circulate on this railway. However, steeper railways are very common, including rails which allows heavy freight trains. For instance, according to German language Wikipedia:

The Gotthard railway has a max steepness of 2.8%
The Simplon railway as well as the Neuchâtel–Pontarlier railway a max steepness of 2.5%
The Arlberg railway in Austria has a steepness of 3%.

Some trains which only allows passenger train and have narrow gauge have much steeper rails:

The Uetli train in Zürich has a steepness of almost 8%
The Pöstlingbergbahn has a steepness of 11.6%, (narrow gauge)
Lisbon tramway has a steepness of 13.5%

Since the maximum allowed steepness is a major factor when designing a train line, I really wonder what factors determined it.

What kind of problems appears when the rail is too steep for a given train, is it a problem when going uphill (train slip and can't advance) or when going downhill (train slips and can't brake).
Does the weight of the train, or the power of the locomotive play a role
Did technology (i.e. more powerful motors, motors and/or braking on more wheels) allow steeper trains as time passed, or is there a hard physical limit that can't be overcome ?
Why could Switzerland and Austria allows freight trains on 3% steep tracks while Germany needed to limit itself 1% ?
When an international freight train circulates, how do we know which routes it can or cannot take due to its weight ?

EDIT: Since I asked the question, I've learn about a very interesting thing on the subject : In Geneva, 1904 a tramway line with a steepness of 11.8% was ready for usage but an accident when doing tests, where the tramway slipped and was unable to brake, cancelled the line. So apparently the major problem is being able to brake when going down. But the Lisbon tramway seems even steeper and didn't have similar accident as far as I'm aware.


texts: transient heat losses approximation, closed chamber

texts:
I want to build a small 1x1x1 m insulated (wooden) box, with the purpose of testing an internal coating (the idea is to buy 5 square meters of it instead of 60 for a full scale room). My idea was to place an electrical heating element and a small fan inside, and raise the temperature from approximately 20 to 40 degrees Celsius. Given the air conditions inside, I used the Carrier diagram to find the thermal power I would need to heat up the humid air volume in 0.5 hours. I then tried to consider transient heat losses through the walls of the chamber, of which I know the transmittance: to do so, given the relatively small temperature differences between inside (from 20 to 40 C) and outside (20 C), I figured I would reduce it to a steady state case with a constant internal temperature of 30 C (arithmetic mean between initial and final temperature).
The thermal power lost through the walls and calculated this way is then, in my ideas, to be summed to the power needed to heat up the air volume, thus obtaining the power I need from the heating element.

My questions are:

1- Is that of the average temperature a good assumption?

2- Apart from that, am I doing anything wrong?

I reckon this is quite basic stuff, I'm sorry, but I never faced this kind of issues and second opinions would be of great help.


texts: How to select a smartphone IR camera for VOC monitoring

texts:
I am currently working on a problem involving volatile organic compounds (VOC) source monitoring on some oil and gas transportation environment. I think using infrared (IR) cameras could be a straightforward approach. The core idea is that temperature gradients will indicate the points where there are emission sources.

I am currently comparing IR camera specifications. Some cameras can be literally portable as a smartphone gadget (e.g. Flir ONE) but I'm quite lost on which properties I should look for (gases' and cameras'), in order to find the most practical and cost effective solution. I've thought to start by finding out:

Which are the most frequently-occurring VOC in these environments;
What are these compounds' most interesting properties (maybe emissivity, absorptivity, transmittance, reflectivity?) Note: Please correct me if I'm wandering off here, as it's been a while since I read any Heat Transfer literature;
And how broad can the cameras be in terms of energy spectrum registering.

I am looking for guidance from anyone with practical experience using this method, especially with a gadget like the Flir ONE, or any method of inexpensive, portable VOC monitoring.


texts: How do I sense reflective tape such as on a spinning wheel?

texts:
I know that the frequency and rotational speed of a spinning shaft or wheel is measured using a device that senses a piece of reflective tape on one of the rotating components. I am thinking a laser device might be best suited but haven't been able to find the correct device. What is this device called?

This is for a fairly high rotational speed (3600 RPM).


texts: In an 12v outdoor lighting circuit, is our electrical consumption (our electrical bill) determined by the 50W 12V bulb that is connected to the transformer, or the 300W rated output of the transformer?  I have equally received two answers; i.e.....(1) our electrical usage is based upon the 50W bulb, (2) our usage is determined by the transformer making available 300W, regardless how much of the 300W we use.


texts: Why have thorium fueled nuclear reactors not been more fully developed?

texts: Why have thorium nuclear reactors not been ore fully developed?  Earth has more thorium than uranium.  Is it technical difficulties or the fact that uranium technology was developed first for military reasons?  Are there other reasons?


texts: Is the sewer outfall discharge supposed to have foul odor?

texts:
As far as I know a treatment plant's job is to treat black water to become effluent. Part of the process is removing dangerous microbes, grease and other environment damaging substances. However, is it possible that the odor remains in the effluent? Or that safe effluent can still contain odorous compounds unless scrubbed?

NOTE: I live few kms away from one that discharges into a river that has moderate odor but at that distance away from residences, I guess it doesn't matter.


texts: Correct axial force distribution between pinned ends of a member?

texts: I have a planar member pinned at both ends with compressive axial loads at 1/3 and 2/3rd position of 14.4 applied between them. Is the following axial force distribution correct? Shouldn't the section E2 carry the 14.4 kN load. Note all material properties are the same.