texts: What's the exact formula for calculating steering angles of a modern car?

texts:
I'm interested in how the steering angles of a modern car are calculated, I'm assuming it should be similar to Ackermann Steering formula.
However, the wikidepia page for Ackermann Steering mentions that "Modern cars do not use pure Ackermann steering, partly because it ignores important dynamic and compliant effects, but the principle is sound for low-speed maneuvers."


texts:
At times, the Swagelok SS Ferrules gets crimped tight into the SS pipe. In those cases, can these ferrules be forcefully removed and reused?

Or was this a result of faulty installation?


texts: How to determine data size created by sensor for calculation of signal processing and transmitting over wireless communication?

texts:
I want to build some sort of SAR sensor. Since radar works high speeds and creates loads of data this should be processed faster. I am trying to find algorithms to be used for this purpose. I am at the beginning of the project so just looking around some information. I haven't had much progress yet.

I have some values in mind such as, what frequency I will use, what bandwidth I will have, what sampling frequency will I have and how many channels etc. Then I will process them. Preferably in real-time. But I am not familiar with the way how the storage capacity and processing speed needed can be calculated for this. I want to decide whether I need to use onboard (battery powered unmanned vehicle) computation or I need to send raw data to ground-station and doing all the processing in it. If so don't know if something Nvidia Xavier would be handy or standard windows installed pc would be good for this purpose.

Example scenario like this, I have a base-band signal at 10MHz and will be swept by upconverting to RF signal and received back following to downconversion back to 10MHz. Then Quadrature mixer will allow me to find the phase shift. If I am not wrong I need to sample this data at a frequency like 50MHz. This will create 50 million samples I and Q in a second for each, thus the total of 10 million data point. This is one-dimensional data. This will be scanned in a spatial direction to yield 2D radar image which should then be processed. I don't know how big will this data be and if I will be able to process it in almost real time.

I am looking for some hints or some experienced advice.


texts: Can buckling failure at the first critical load be avoided by "instantaneous" loading?

texts:
Previously, I was told by someone I trust well that a column can avoid buckling at the first critical load by applying the load "instantaneously" with a magnitude between the first and second critical loads. Of course nothing is instantaneous, so an idealization would be applying the load as a step function. I am an undergraduate mechanical engineer with no practical background with buckling failures and was hoping someone can shed some light on this problem.

I'm sorry I have few details or sources backing this question up, I have been trying to confirm it and have been unable to find it online.

Is this true? Can buckling be avoided at the first critical load by instantaneously applying a load between the first and second critical loads?

Thank you!


texts: Will a 3-wall acoustic barrier work or will sound go around?

texts:
I have two heat pumps directly outside my house and they are noisy so I am considering the viability of using a sound barrier to block the sound. The acoustic barrier itself will definitely absorb and eliminate the sound in three directions, but the question is whether the sound will be able to go around from the open side and get into the house. Here is the basic set up:

The heat pumps are shown in blue. The proposed acoustic barrier is shown in red.

Will sound be able to go around the edges of the barrier and get back into the house or will it radiate outwards and not come back into the house?


texts: Is there any mechanical engineering solution that employs 'ankling', as per a cyclist's ankle/foot/pedal setup?

texts:
A cyclist will have the pedal spindle somewhere under the front part of their foot, usually around or just behind the ball of the foot. This means that the ankle is part of the driving movement - at a minimum, holding itself in a single position while the other muscles apply torque to the pedals, so the 'ankle muscles' are acting as a static stabilising force; or in some riders the ankle position changes throughout the pedal stroke, possibly helping to apply force around more of the pedal circle, possibly helping around the 'dead spots' where the pedals are at the 12 and 6 o'clock positions. This video illustrates it very well, from 3m08s: https://www.youtube.com/watch?v=E7K8VcBXUM4#t=3m08s
Are there any machines designed to utilise a similar mechanism? Off the top of my head something like a steam train doesn't, it uses the fewest, simplest parts to enable the linear movement of a piston to be translated to the circular movement of the wheels.
What would be the advantages/disadvantages of such a mechanical setup?


texts: Deriving the ideal equation for sluice gate problems - incompressible inviscid fluid

texts:
I'm trying to figure this problem out, i know the correct answer, and i know the method, but for some reason i'm missing something and i'm just not getting there, any help would be greatly appreciated.

Consider a Sluice Gate (lock gate) as pictured,

A brief Description is.

  A large reservour if fluid of depth $h_1$ is held stationary in $x < 0$ to the left of a vectical gate at the origin of width W. The gate is raised and fluid streams steadily through the opening between the bottom of the gate and the base of the reservoir.

  Far upstream (the left of the gate) the fluid moves with constant velocity $u_1$ in the x horizontal direction and uniformly through the depth $h_1$. far upstream,  (to the right of the gate) the fluid assumes a depth $h_2$ and moves with constant velocity $u_2$ in the horizontal x direction.

  The job is to

  Derive a relation expressing conservation of mass.
  Use Bernoulli's equation along a suitable streamline in order to show two >possible choices of $\frac{h_2}{h_1}$ are $\frac{h_2}{h_1} = 1$ and >$\frac{h_2}{h_1} =\frac{Fr^2+Fr\sqrt{Fr^2+8}}{4}$ where $Fr$ is the Froude number $Fr = \frac{u_1}{\sqrt{gh}}$
  Then finally
  Find the net force on the raised gate

So,
1. Deriving a relationship expressing conservation of mass is just understanding that as the flow empties from one side, it must rush into the other at the same rate,  and so we have
$$Q = u_1 A_1 = u_2 A_2 \implies Q = u_1 h_1W = u_2 h_2 W$$
as our relation.

this has been bugging me quite a bit, i'll come back to this.
with This question, i believe the correct method is to pick a control volume at about the sluice, then combine the above conservation of mass equation with bernoulli's equation for a steady flow. so
here i go...

We express Bernoulli's equation as
$$\frac{1}{2} \rho u^{2}_1+\rho g h_1 - \frac{1}{2}\rho u^{2}_{2}+\rho g h_2= p_{constant_1} - p_{constant_2} = P_{c}$$
where we have h is the elevation, $\rho$ the density and u is the flow velocity. we have that the pressure also cancels out. and the above equation happens because bernoulli's is a constant along any streamline in the flow.

now using this line of logic, i find myself coming up with $$F = \rho g \frac{\left(1-\frac{h_2}{h_1}\right)^3}{2\left(1+\frac{h_2}{h_1}\right)}$$ which means im missing a step as the correct answer is actually

$F_{net} = h_1^2 W\rho g \frac{\left(1-\frac{h_2}{h_1}\right)^3}{2\left(1+\frac{h_2}{h_1}\right)}$

This has been really bothering me for the last few, so any help would be greatly appreciated. Thank you for taking the time to read this.


texts: Is it possible to create a material with alternate atom-size layers of 2 different elements?

texts:
For example one layer (one-atom thick) of a superconductor, and the next layer (also one-atom thick, of an insulator, next layer again an atom-thick layer superconductor etc.. until the overall thickness of 1 mm is reached.
If so, how?


texts: Identifying affordable alternatives for low-frequency high-current DC-DC solid state relays

texts:
Please note, this is not a shopping question; this is a what type of component works best for this scenario question.

I have an induction heater circuit and a 5A max. / 24V wall wart, and I'd like to switch off / on the output of the wall wart so that I can control the power output of the induction heater.

About 7 years ago I found something by the name of SSR or SCR (or something) on digikey and that cost a reasonable amount (< 10 USD), and now I can't find it any longer.  The SSR's on there that can handle that much power cost around 50 USD, which is too much to design with.  The frequency can be low (5-100 Hz) range, since it is a relatively slow heating process.

I plan to switch the relay on/off with a raspberry pi, and will probably need a transistor in between.  I don't want a mechanical relay since the thing will probably break before even making real use of the product.

The component I found prior was upright flat-rectangular with 4 thru-hole terminals coming out of the bottom smaller side.  I found some that look like that but like I said they were in the 50 USD range.  Also, that component if I recall correctly was for switching on/off AC for a different type of heater, so maybe that's why it was cheaper?

What types of alternative components should I be considering based upon these requirements?


texts: Will stainless steel with a #3 finish corrode faster than a #4 finish?

texts:
I understand the difference between a #3 finish on a piece of stainless steel compared to a #4 finish being that the surface roughness is different.  Specifically, a #4 finish is classified as having an Ra value of less than 25 micro-inches where as a #3 finish has an Ra value of less than 40 micro-inches.

The basis of my question is if I have two cabinets made from 304 SST, one has a #3 finish, one with a #4 finish in the same outdoor environment, which will rust faster?  Are there any other concerns between the two cabinets as far as performance of the cabinet (welds, hinges, bends, etc.)? Have there been any studies conducted?


texts: Shade tree engineer needs help calculating hoop stress

texts:
I have an extruded aluminum tube. I'm trying to come up with an Excel calculator that will help me find out how much force would be exerted on the internal walls if the tube was filled with rubber, and then sent through a vulcanization process; failing that, I'd like to learn how to calculate the hoop stresses that the tube should be able to withstand, with the assumption that the structure of the tube was perfect (weld seams, free of voids, and such).
I know all of the dimensions and mechanical properties of the tube (below); however, absolutely nada! for rubber; much less vulcanized rubber. This is an extruded tube, not rolled and welded. The weld seams I mention above are solid-state welds, fused in the welding chamber of a porthole extrusion die, while under tremendous pressure and at a temperature of about 1,000f. If it makes any difference, the extrusion die has 5-ports so, there are 5 seam-welds approx. 72 degrees apart that travel the length of the tube.
Meet the victim:

6061 aluminum alloy tube produced utilizing port-hole extrusion.
Artificially aged to T6 temper
Yield Strength = 36.2 ksi
Ultimate Tensile Strength = 40.0 ksi
Length = 3.0"
Outside Diameter = 3.150", with 0.008" ovality
Wall Thickness = 0.118" with 0.004" wall spread
I'll also say that I can routinely expand the diameter by 15%+ via drift-tests

If you can help me, I'll add you to the liner-notes on my upcoming record release; it's been in the works for ten years so, we've got time.


texts: What is this kind of sewer maintenance work?

texts:
I took this photo behind my place; there was this group of workers for about an hour.

They have a small hose, from the black spool, they were pushing in and out of the manhole and a large hose that didn't seem to move at all.

The truck's engine was quite noisy, so I'm assuming they have a large pump. I'm curious what kind of truck it is and what they could be doing with it.


texts: On partial reboiler and total condenser in distillation column

texts: Why is it that a total condenser and partial reboiler are used in a distillation column and it is not the other way around?


texts: I need to determine the RPM of a rotating cylinder over which a silk thread is wound and is moving along in the fashion of a screw.

texts:
Recently I visited a sericulture facility in India and I saw that people there 'degummed' (https://www.youtube.com/watch?v=h13fctiTylI) silk in a batch process.

As a Chemical Engineer, I thought of this as an unsteady state unit operation and
I have decided to work on making this process a continuous or steady-state operation as a summer project.

So far this is my schematic

The silk thread will be pulled over a large drum and will pass over this drum a number of times in a helical fashion. This drum is immersed in a bath of boiling water with added chemicals so that the silk is degummed. The thread will come out of the other end another end of the cylinder and will be wound on another bobbin.

Now I have already determined what sort of chemicals and mass transfer I am gonna get and what should be my temperature of the bath. I am not able to work out on the residence time any part of the silk thread should spend in the bath ? for this I need to determine the RPM of the rotating drum? how do I calculate that? standard degumming time is about 60 minutes. So if I say that the length of the drum is L and its diameter is D and say it is rotating at an angular velocity of w. How do I develop a set of equations to determine my rpm so that I can change my drum dimension if the residence time is too long or too short.


texts: What is the steel used for CHC DIN912 class 12.9 exagonal bolt?

texts:
I would like to know which steel is used for CHC class 12.9 bolt DIN912 (i am looking for the young modulous & poisson ratio of the material).
Thanks a lot.
Alexandre


texts:
I was reading: https://www.tec-science.com/mechanical-power-transmission/involute-gear/geometry-of-involute-gears/
Which goes over construction of involute gears, Everything else makes sense but I am still confused on what defines the tooth width.
Does someone have an intuitive/easy explanation on how you derive the tooth width for an involute gear and why it makes sense?


texts: Standard name for "retargeting" behaviour in motor controller

texts:
Over the years I've encountered a number of motor controllers (e.g., controllers in the NI Motion series) that incorporate what I usually refer to as "retargeting" behavior.

Specifically, if the controller is told to move a motor to position A and, while moving there, is told to move the motor to position B, it will stop moving toward position A and move to position B instead.

(This is opposed to behavior where the controller simply ignores movement commands issued while the motor is moving or maintains a "target position" that can be updated during motion and gets checked upon the completion of every movement to determine if a correction movement is required.)

Is there a standard/common name for this retargeting behaviour, particularly in the context of motor control?


texts: Finding Poisson's ratio of 3D model in ANSYS

texts:
I want to find the Poisson's ratio of a 3D model, not the material but the model. How can I do this in ANSYS workbench?
I am using this formula, but I can't get it to work with different models. I am not sure what strain is the correct to use, can someone point me in the correct direction?
$$\nu=-\frac{\text{Strain in direction of load}}{\text{Strain at right angle of load}}$$
$$\nu=-\frac{\varepsilon_{lateral}}{\varepsilon_{axial}}$$


texts: I have heard that error correcting codes are used to store and retrieve data in hard-drives but are they used in the processors in common laptops? Is the information encoded before it is processed?


texts: Is "critical pipe" a proper term for a pipe used in a critically important role?

texts:
My translation:

Internal pipe diameter inspection
This kind of inspection is carried out on a by-order basis using a certified gauge (for sizes 40 mm and above) of the go/no go type, with both sides of the pipe subjected to measurement along the length specified in the regulatory documentation. Pipes intended for use in shock-absorbers are inspected using the special instrument called a bore gauge. Instrumental inspection of internal pipe diameter is carried out for critical pipes and relies on the use of ultrasonic equipment.

The original Russian phrase is "трубы ответственного назначения" and could be translated as "pipes used in critically important roles (applications)": when a malfunction may lead to injuries, deaths or major industrial accidents, or to the shutdown of the whole plant, with the resulting financial losses.
Is the phrase "critical pipes" a proper choice, or are there some other phrases to signal the same meaning? Would "critical duty pipes" fit?
The word-for-word of the original is "truby (pipes) otvetstvennogo (of high responsibility) naznacheniya (purpose)".


texts: Why are vacancies in solids called as equilibrium defects?

texts: My professor, when discussing about Random Walk model during diffusion in metals said that "Vacancies are equilibrium defects but dislocations are not". I could not understand why. Why is it so?


texts: Air compressor that doubles as a pneumatic motor?

texts:
I am working on a compressed air energy storage system. The size and weight of the system are heavily constrained; nothing should (ideally) exceed a few pounds. For this reason, I would like to store the energy (compress the gas) and extract the energy (make the gas do work) with the same mechanism in a rotary fashion.

Essentially what I need is a rotary air compressor that, when air is forced through in the opposite direction, doubles as a pneumatic motor. I'm working with fairly high pressures (I'm estimating a few hundred psi) but low volume. In my search, I have found a plethora of compact rotary air compressors and rotary pneumatic motors, but there is hardly comment on what systems would work as both.

To me, it seems very intuitive that an air compressor could have these properties, but I don't want to jump to any conclusions. I have looked at several compressors, and the most applicable to my situation seem to be:

Centrifugal compressor
Axial flow compressor
Rotary screw compressor
Rotary vane compressor

The centrifugal compressor is ideal, but it seems the least likely in my eyes to be reversible, at least with any efficiency. I also looked at pneumatic motors, of which there were fewer available. Most applicable seemed to be the:

Rotary vane motor

Other systems, such as the pietro motor, were obviously not applicable in my light weight, compact application. The correlation between the rotary vane compressor and the rotary vane motor is promising, but I would like to know about any options I have.

What rotary gas compression systems can double as motors powered by the gas they compress?

EDIT
The answer most likely lies in the similarity between a radial (centripetal) turbine and a centrifugal compressor.


texts: I found very little information about that, but it says that its technically possible, but then why it isnt used instead regular carbon fibre machining? It sounds way easier...


texts: calculating the minimum force needed to lift a rigid awning - class 3 lever problem

texts:
I am building a camper and one idea is to have an extra 4 solar panels as an awning bolted to a a rigid frame, hinged to the camper at the top.  It hangs down the side of the camper.  I will use one or two actuators to lift it to, say, a horizontal position. It will actually only hang down half way as it will be folded in half for travel, but the unfolding is not part of this problem, so it can be assumed to hang down unfolded as a rigid awning for this problem.
I want to figure out the size and power of the actuators I need. I could just guess and maybe get close or if not, just buy bigger ones through trial and error, but I'd like a sense of what I need here.
This is a class 3 lever problem, but with my limited physics background, I'm running into problems accounting for the change in angle against gravity as the awning is lifted.  The work increases as the awning reaches 90 degrees (I think), so the most work is at the (corrected) END.
In addition, the location of the anchor point for the actuator is open. Though this may be determined by the distance the actuator can extend.   For example, this is a 40" stroke, 400 lb capable actuator - https://amzn.to/3jSxIog.  Would it work?
THE AWNING WEIGHS APPROXIMATELY 200 POUNDS (4 PANELS, 45 POUNDS EACH PLUS FRAME AND HARDWARE). IT IS 80 INCHES WIDE FROM THE HINGE (FULCRUM) TO THE OUTER EDGE.
BEFORE LIFTING - AT REST
|*! = hanging awning at rest (80 inches)
| !
| !
| !
| !
| !
|
|
| = side of camper

AFTER LIFTING

|*_._._._._._. = hanging awning lifted (80 inches)
|    /
|   /
|  / = actuator that has lifted awning
| /
|
|
|
| = side of camper
```


texts: Machine design tip over safety requirement?

texts:
I am designing an automation machine. I remember that I read a document that the machine is stable if some certain amount of force to push on the top corner of the machine and the machine does not tile more than X degree then the machine is stable.

I could not find the document again. Do you see something like that online?


texts: Can I use a 1/4 inch shaft in a 6mm hole?

texts: My current 6mm shaft is a bit smaller due to tolerance issues. I was planning on getting a quarter inch shaft to try and push it into the hole. Will it be fine?


texts: Why does the standard $k-\epsilon$ model use zero equation models?

texts:
According to Hoffman, the standard $k-\epsilon$ turbulence model incorporates a two-layer approach (inner region and outer region formulations to reperesent mixing length) when it comes to regions adjacent to wall surface $(y^+ \approx 30 - 50)$.

My understanding of the $k-\epsilon$ model is that a two additional equations are added to the system of flow governing equations, one equation for kinetic turbulence energy $k$ and the other is for the turbulence energy dissipation rate $\epsilon$, and the closure problem is solved by using dimensionless groups as boundary conditions such as turbulence intensity, turbulence length scale and hydraulic diameter.

My question is why the $k-\epsilon$ model uses zero equations models (algebraic models) for regions adjacent to the wall, what advantages do zero equations models have over $k-\epsilon$ if by definition zero equations models assume that the rate of production of turbulence and the rate of dissipation are approximately equal and they do not include the convection of turbulence?


texts: Why is the friction factor in laminar flow independent of pipe roughness?

texts:
The Darcy friction factor is defined as:
$$f_D =\frac{64}{Re}$$
with $Re$ I mean Reynolds number (global).
I was wondering why Darcy in laminaire flow is independent of pipe roughness (wall roughness)?
That is not the case in turbulent and transient zone, the iterative methodes are much more complex and the friction factor is a function of wall roughness.


texts: Strength of face-nailed connection for stair steps

texts:
I'm building a loft ladder with alternating-tread steps. The stringers are 2x6 White Spruce, and I'm hoping to build the steps out of the same material.

The span for the steps is 21". Code requires handling a maximum point load of 300 pounds at the step center, or a live load of 40psf, whichever is higher.

If I've done the math right, steps made from 2x6 white spruce laid flat will  meet that requirement.

However, I'm unable to find reliable information about the connection between the steps and the stringer. I'm hoping to attach the steps with three 16d 3.5" nails on the wide side, and two 16d 3.5" nails on the narrow side.

My main concern being the limited amount of wood above the fastener in the step member causing failure.

How can I determine the maximum load the connection can bear in this configuration:


texts: Can a face gear be designed with symmetrical teeth to enable the pinon to slide inwards-outwards?

texts:
A face gear tooth is asymmetrical (designed on Kissoft) in the direction towards the center vs the rim of the face gear. .
The pinon, on the other hand, is symmetrical along its tooth length. Would it be possible to design a face gear that would be also symmetrical (yet not cause undue tooth wear) to allow the pinion to slide between outer and inner face gears, to enable the pinion to consecutively engage two concentric face gears?


texts: How to fix a shaft in position, vertically

texts:
I am doing a project where I have to mount a gear shaft with two bearings on either end (deep groove ball bearings) but I am worried that they may fall through the bearings during operation as the shafts axis is vertical.
Are there any suggestions for how I could get around this.


texts: Meaning of quarter hole color fill in drawing

texts:
In this drawing 4 of the holes have the top left quarter filled in black.
What is the meaning of that? It it some special type of hole?
The drawing is from a Waveguide and in the specs it says
Flange type FDP32 (Cover)

So I'm thinking it might be some way of mounting the cover.
Is there a standarized meaning for the  symbol?


texts:
Problem: I have been asked to help determine whether a waterwheel is able to generate enough power to run 5 x 15kW pumps in a remote location in Zambia where there is no constant power supply. I work in the mining industry so this question is a bit out of my field to say the least.

Given parameters:

The  pumps as mentioned are 15kW pulling 34 Amps (max speed is 2900RPM)

The water flow to the waterwheel is 7m3/s in a channel that is 3mW and 1mH. The maximum head from the top of the channel is 3m. Please see attached picture (left is top view right is side view)

If I have to do basic calculations to determine:
- The speed of the water wheel  (RPM)
- Dimensions of the water wheel
- Will the water wheel be able to produce that amount of power.

Can someone please guide me in any way regarding what calculations are required, where to find these calculations? What additional parameters are required if necessary?


texts:
I'm trying to design and simulate a simple knurling device.
The shaft ( blue part ) has a flat surface at the other end, where the small grey pin connect the green body to the shaft. I guess you can see it clearly in this view:

My first question is, why we do even need to give the surface such a flat shape?
I think maybe it's easier to bore a hole, but I'm far from being sure.
And is there any other flat surface on the other side ( opposite side ) or there is only one flat side ?


texts: What is basic knowledge wanted from a bachelor mechanical engineering student before joining?

texts:
At the moment, I just finished my senior school year and in a few months, I will be studying mechanical engineering as bachelor degree. However, I don’t like to waste my time and want to use this time wisely in preparing myself well before entering mechanical engineering.
What type of mathematics should I further practice apart from calculus? Should I go further in the studying of calculus, more specifically, should I go more of just the basics that are learnt in schools?
Should I learn all chapter in the book from physics including nuclear physics etc?
What about chemistry?
Please let me know what you think and don’t hesitate to give your opinion.
Thanks a lot.


texts:
Is it possible to detect specific UVB wavelength ranges using just a UVM-30A UV sensor or similar.

The sensor in consideration is GUVA-S12SD.

Seems to indicate that it generates a specific current level when sensing a specific wavelength, but because its sensing a range of wavelengths I guess you get the summation?

Is it possible to use any techniques to perform a UV spectral analysis on the output so as to detect the presence of a specific wavelength band.

It also important to determine relative intensity over time for the band. Is this anyway possible?

I'm not an engineer, but I can do any programming necessary.

Can anyone help!


texts: What is the purpose of combustor in a gas turbine

texts:
I have read online that a gas turbine converts the chemical energy in the fuel gas to mechanical energy of the turbine blades. The way I see it, because of this hot air one would have to go for heat recovery and use costlier heat resistant material in the turbine. So instead why not send the compressed air directly through the turbine blades?

As an example, in wind turbines  I understand we try to work on factors to improve the wind speed which in turn would mean more mechanical energy of the blades and in turn more electricity. I am trying to understand the purpose of the combustor similarly. Thanks for your help!


texts: Can you use the Hagen-Poiseuille equation for a pipe which radius is in the sub-millimeter region?

texts:
As this will depend on Pressure drop $\Delta p$, assume that it does not leave the range from 0 to 100 bar. The Hagen-Poiseuille equation for an incompressible fluid is defined as:

$$ \dot{V} = \frac{\pi R^4 \Delta p}{8\eta L}$$

I realize that it wont be applicable for very small (nm) diameters, so this question is in the context of microfluidics.  Fluids of interest in this case have a kinematic viscosity of 1 cSt to 10000 cSt.


texts: Strength optimization of a hollow cylinder

texts: Is it possible to improve strength of a hollow cylinder against radial load by making holes in it or converting it into scaffolding like structure without changing material, internal dia, external dia and length?


texts:
I am a graduate student trying to sharpen the direct stiffness method skills. However, I am stuck at the beginning.

The problem is given in the image.

Can someone help me to write down all the nodal and member forces with equations ?


texts: How are gyroscopes used for motion control?

texts: Is there a way to use gyroscopes to control the motion of a pen-like device? I am trying to build a device that will be able to take in a radius input and draw shapes without physically moving my hand in the shape of the shape. An example of this type of device would be the spyro-gyro toy pen.


texts: Why are rail signals overbuilt compared to road signals?

texts:
Here is a photo of a railroad crossing near a road intersection.

Traffic, Rail Lights out of Sync at Fruitvale Avenue Crossing

The road signals are mounted to slender poles (or even suspended from a cable). Maintenance workers can access the road signals with a truck-mounted boom lift. In contrast, the poles that support the rail crossing signals are built much sturdier and also support a ladder and catwalk. (Ladders and catwalks seem to be common on railway operating signals, too.)

Since there are many more signals than workers, it seems like the total cost to outfit the workers with boom lifts would be cheaper than making every signal easily accessible.

I realize that road and rail signals developed independently, but their common engineering criteria (to hold a light up in the air) should have resulted in road and rail converging on a single lowest-cost solution.


texts: Is there such thing as supreme board for international arbitrators?

texts:
My cousin is a mechanical engineer, got contacted today from someone who claimed to be working for the supreme board for international arbitrators (sbia) and ICAC in the Middle East and north Africa region.

She told him he would have to pay $300 in order to get a 1 day course, or workshop, afterwords he would become an international arbitrator for engineering issues related to his field. Full sized images here and here

My cousin and I think this is a scam, and their website is bad and there's no mention about SBIA anywhere, no results on google, no social media presence. I would like to ask you about it though, have you ever heard about it? Is this a scam?

Edit

I think they are copycatting this http://www.incodir.org/, not only that, I hope you could read arabic, on the first image, it says in parentheses

ريم الفانك

which also works in the organization I mentioned, I'm going to try to contact her somehow, either she's being impersonated in which case I'll see if we can press charges, otherwise she's part of the scam, I hope not.

Edit 2

I tried contacting president@incodir.org, the email didn't get delivered to report the case, well then I must conclude that they too are a part of the scam sadly, the rabbit hole goes deep.


texts: Confusing symbol in led labeling: How to Obtaining precision with hobby electronics?

texts:
Does anybody know what that "f" looking sign is next to the 5, left-hand bottom corner of the LED labeling?:

It Indicates the diameter of the LED package.

Summary of Conclusion: Don't seek precision unless you have the means to obtain it.

...I'm a young electronics hobbyist, who has the passion to become a robotics engineer at later stages of my maturity.

Lately I have been tinkering with my first circuit designs, simple stuff really. My first circuits were "plug-and-play", based off of rough, highly in-precise calculations, but it would get things lit like the image below:

Later, I decided to revise my scketch, adding in LED's and using a more scientific method to make more precise calculations about the circuits functionality...

Long story, but I got my circuit working. Thanks.


texts: Hollow (rectangular) sections versus solid sections

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I have an engineering competition coming up and one of the things I need to build is structure with both compression and tension members. The structure is scored based on the load held/weight ratio, and I already have the design I'm looking for but I need ways to reduce weight.
I was thinking about comparing the strength of a hollow rectangular section and a solid one with the same cross-sectional area. I think that I understand that for members under tensional stress, the strength of the two should be equal because the cross section of the two members is the same.
Would this be different for compression members? i.e., would one be able to carry more weight if one used a hollow member instead of a solid one?
EDIT: Another question: If I'm making this in a structural simulation, does the dimensions of the member matter if the cross-section is still the same? I guess you can assume here that the member is undergoing pure compression parallel to the length of the member.


texts:
Imagine you are in the mountains and it is very cold. The walls are colder than the air, so air close to the wall will lose heat to the wall, and by losing heat it might lose its humidity (water condenses to the wall). Now I know this is bad for the paint on the wall. However, in some sense, it is heating up the wall, which will lessen the cooling effect of the air. Please tell me if my logic is correct.
Also, if the walls are now wet, could they allow for more condensation? Or it is impossible because all the surface is covered in water?
PS: House without heating nor insulation.


texts:
Growing up I would have these  RC Car, they had the cover which eiher a cover of a truck or any brand of cars, I could take this cover off and then change the batteries of the rc car or just check the components.

These covers came with the car, had an elastic plastic form and were quite strong

Moving to my question.

What process are those covers made ?
molding or the other options.

I have built my own rc car and looking for a place I can order my own customized cover for the car.

The design of the cover, I made myself.

I have tried 3d printing but to be honest I am not really happy with the results, due to the fact that I have to use sandpaper to smoothen it and it is quite heavy.


texts:
I have an old casio casitone CT-310
Rating: DC 9V 8.5W
Battery 1.5V x 6
or AC adaptor AD-5

I'm looking around the house for a power supply to use.
I found the following:
Output: 9V DC 200mA
from a hand held mini vacuum cleaner charging base.

so the keyboard must demand about 945mA (8.5W / 9V) but the supply delivers only 200mA correct? What will happen if I try to use it? will it be very quiet? or do nothing? or get damaged?


texts: Heat released by gas mixtures that undergo constant pressure cooling

texts:
I'm solving this problem,

I used the formula $Q_p = mc_p\Delta T$. Since it is a mixture, I did this:
$Q_{Total} = 0.3 × 0.867 × (50-150) + 0.7 × 1.043 × (50-150 ) $
$ = -99.02 kJ/kg $
Is my solution and final answer correct? If not, where am I doing wrong? Thankss.


texts: What does high coefficient of moment mean for an aircraft?

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After designing an aircraft idea I had in XFLR5, I noticed that it had a really high coefficient of moment (Cm) compared to other wings of similar size. What does this mean?

I played around with my center of gravity and the coefficient went down, but never to the level of the other aircraft. What relation does this have with the aerodynamic center?


texts: How to quantify adulteration of urea and hydrogen per oxide in cow milk?

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I am very much new in this field and trying to get some information on adulteration of cow milk. I have searched and saw that mostly urea and hydrogen per oxide are mixed with cow milk.

I found that to quantify adulterants in milk, Fourier-transform infrared spectroscopy (FTIR) can be used. Normal cow milk contains (20-70)mg/100ml urea. So, urea content above 70mg/100ml in milk is considered as added urea.

I want to know the exact proportion/amount of urea and hydrogen per oxide are mixed in the cow milk as adulterants. I need to carry out the experiment by adding urea/hydrogen per oxide in pure cow milk to get the desired spectrum in FTIR.

Is it in between 71-100mg or more or in which range actually?

Can anyone point me out any reference? Thanks in advance.


texts:
I made a waterfall hoping to use water as a piston for suction. I'm wondering if some of you could help explain why it's not working the way I was expecting.

This is the basic design: I have a 4 inch by 2.5 foot tube with a 5/8 inch opening on each side. The top has got a hose going to a drain of a 40 gallon tank and falls free at the bottom to fall in to the 40 gallon tank. My thoughts on this was that the tube filled with water would act as a hydraulic piston, though it's sucking air backwards in to the drain of the suction tube.


texts: Is there a limit to how high a water fountain can go?

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The current world record was set by King Fahd's Fountain at about 300m, and a water speed of about 375km/h.
Would it be possible to launch water much higher? Say, by aiming a water jet cutter with a mucher higher pressure upwards?
Or are there theoretical or material science limits to this?


texts: Most of resources I've been reading don't explain the scientific reason for the existence of shear force. Most resources just teaches how to solve problems and about properties. Nothing goes deep (not even a little bit deep, sorry if I'm being unfair, for me it was just drawing diagrams and solving them).


texts: Wing as cantilever beam (beam-rod) model for aeroelasticity fluttering analysis

texts:
I recently bumbped into a rather basic but interesting question on aeroelasticity. I've learned to derive the fluttering critical speed from Pines's theory but it involves some spring stiffness like for normal spring $K_h$ and torsion spring $K_t$.

However, I want to see if I can derive the same thing if the wing is now treated as a continuous beam-rod model (i.e. torsion and bending). The equations of motion are:

$ \frac{\partial^2}{\partial y^2} \left( EI \frac{\partial^2 h}{\partial y^2} \right) + m \frac{\partial^2 h}{\partial t^2} + m x_\alpha \frac{\partial^2 \alpha}{\partial t^2}+L=0$

$ -\frac{\partial}{\partial y} \left( GJ \frac{\partial \alpha}{\partial y} \right) + I_\alpha \frac{\partial^2 \alpha}{\partial t^2} + mx_\alpha \frac{\partial^2 h}{\partial t^2} - M = 0$

For simplicity, let $h(y,t)=0$ and $\alpha=s(y)e^{pt}$ so we can focus entirely on the torsion dynamic response. Let $L=qca_0(\alpha+\alpha_0)$ and $M=qcea_0(\alpha+\alpha_0)$. But now things get out of my control as I don't know how to solve for $p$ (to let its real part positive), given $s(y)$ unsolved too.


texts: Free alternative to openinig solidwork defualt files in linux( *.sldprt & *.sldasm)?

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I migrated to Linux and don't want to use solidworks , so i need one software which could opening my already solidworks file like *.sldprt and *.sldasm .

So i have installed FREECAD but it could not opening those files.

Another question i have is this:
  could i do my modeling designing which only need to fit dimension and shape without any characteristic simulation and ... in solidworks alternative, and which one is your suggestion?

Thank A lot.


texts: How to calculate the dimensions of an ellipse in a multi-view projection

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The following image is  an example that will help to demonstrate what i am saying and this below is a blender image version of an object with a slant surface at the top.

to draw the multi view projection of this view all the necessary dimensions are given, so the top and the front will be as follows

top:
front:

i very well understand how the front and the top projections worked and here is where my question arises, as seen both from the pictorial view and the two side projection there are two thoroughly subtracted cylinders in the slant surface which means when i try to do the right side projection i will be seeing two ellipses rather than the original circles i have seen by the top view as shown below, so how could i figure out the dimensions of the major and minor axis of the ellipses.

right view:


texts:
I would like to know how to synchronize two (nearly)-identical DC motors (approx. 1 Amp/12 VDC each) with permanent magnet, while they are driving on the same surface (railroad Track).
The problem is that 2 motors of the same brand and type always have somewhat different characteristics at different speeds, resulting in (unnecessary) heating of one of the engines and its bearings.
I'd like to sync them in an elect(ron)ic way as simple as possible.
Thanks for help. A.


texts: How is a self-locking hex nut (ISO 7040) used?

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I'm interested in the usage of a self-Locking hex nut with a nylon insert (ISO 7040 or DIN 985).
How is it used correctly? Is there a prescribed usage, or a norm that describes how it should be used?


texts: Can adding stationary bades after an axial ducted fan increase efficiency?

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When searching for this online I did not seem to be able to find any examples of this, which might imply that this idea does not work (or I did not use the right search terms). I have seen the use of two counter rotating fans, but this would probably still impart rotational energy to the flow after the second fan. I think a jet engine is an example of what I mean, but I at least have not seen other applied use cases.
Intuitively I would think that adding stationary blades after the driven rotating ones could improve performance (if the total weight is not an issue). Namely those stationary blades can convert some of the rotational energy of the fluid, imparted by the rotating fan blades, into (linear) kinetic energy of the fluid. So increase the mean flow rate and/or head pressure. Also converting and thus reducing the rotational energy should also reduce friction between the fluid and the wall of the duct. Since a rotating fluid flowing through a duct has a higher velocity near the wall then a none rotating fluid.

Would (some of) these gains be counteracted by a higher torque required to keep the rotating blades spinning at the same speed? Or might the gains at typical speeds be too low?


texts: Can someone please explain what a PT1 filter is in simple terms?

texts: The context here is for determining how driveability filters are calibrated since most of them use pt1 filters to filter the torque demand.


texts: Calculating engine pressure from measureable quantities

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How can I calculate the engine pressure in units of Bars by using torque, the cylinder volume, motor efficiency, and the gear reduction ratio?

My values are as follows:

Torque = 1063 Nm
Hydraulic Motor Cylinder Volume = 2.56 ℓ [litres]
Gear Reduction = 1
Overall Efficiency = 0.76 [76%]

Q: Do I need any more values to calculate the engine pressure caused by the torque generated? If not how can I calculate the pressure in units of Bars?


texts: How to select a micro controller for a low power application?

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I am interested in a microcontroller for a low power application. I have been advise to look at MSP430 or Microchip PIC microcontrollers. I also wonder if ARM-Cortex-M0 is a good choice too.

At a high level the system will have two analog sensors, few GPIO to control LED, and actuation mechanisms. The systems is intended to be powered with standard batteries.

What are the critical parameters that warrant attention in researching for a suitable low power micro controllers?


texts:
I'd like to calculate the viscosity of a liquid in a container systematically (and feed the results back to a computer). I only have basic knowledge of physics and mechanics.

I think that a motor with a tiny "windmill" constantly turning inside the liquid would be enough because someone one could measure the current and voltage being supplied to the motor and then somehow link that back to the force which the motor is putting in. I'm hoping that there's a formula to link force and volume of liquid moved to viscosity.

Does this sound like a good approach and if not, why?

If it is a good approach, how would I go about calculating liquid viscosity from the original data and what sorts of measurements would need to be taken?


texts:
I came across this problem a while ago and I'd like to solve it, but I'm not even sure where to start. How would I start this problem and what formulas do I need? I'm not asking for a solution, but that would be awesome. Thanks!

Problem Statement

Diagram


texts: I am studying Gas dynamics and came across the lift angle approximation as based on Skelett Theorie (in german). I have done google searches on finding this theory but no luck on any information. Can anyone perhaps in Aerodynamics help? Thanks.


texts: Can graphene really be made in a modest lab at home?

texts: I have seen some resources on the Internet that claim to be able to make sheets of graphene (single atom thick lattice of hex-bonding carbon) from commercial off the shelf materials and a modest lab setup.  I have great interest in graphene and would like to attempt the manufacture but I don't want to waste my time with bunk.  Can anyone recommend a tried and proven way to manufacture without very elaborate and expensive lab?


texts: Mechanical joint that break at specific force

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I am designing a joint which I want to break at a specific force. I want to design a 2 parts connected by a joint that breaks when a certain amount of force is applied and thus prevent any damage to those individual components themselves. I also want the joint to be easily replaceable without replacing the individual parts themselves. I'm hoping to 3D Print the joint.
I have seen some petrol stations that have pipes attached such that they will break and cut-off fuel supply if they are pulled harshly(i.e. By someone who forgot to take the nozzle off their car and tried to drive away). I don't know the name of the mechanical linkage they use. But I'm hoping to achieve a similar affect.
I would appreciate if you could point me to relevant information sources and design of such type of linkages.


texts: DOE to optimize a chemical reaction with impurity forming in series

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This question contains chemistry, but the main focus is DOE design--hence posting on the engineering stack exchange.

The problem is a chemical reaction:

A + B -> Product
Product + B -> Impurity

The goals are

to minimize the impurity.
to minimize leftover A.

Reacting the mixture for a long time will get rid of A but increase the Impurity.

Reducing B will decrease the Impurity but increase leftover A.

To optimize the reaction, I'm planning a DOE with temperature, reagent amounts, and reaction time as variables.

I used software to generate a central composite design. However, the reaction time inputs for each experiment aren't physically reasonable. Look at some of the experiments:

+-------------+---------------+-------------------+
| Temperature | Reaction time | Amount of B       |
+-------------+---------------+-------------------+
| 20 C        | 4 hrs         | 1 mole equivalent |
+-------------+---------------+-------------------+
| 50 C        | 4 hrs         | 1 mole equivalent |
+-------------+---------------+-------------------+

At 20C, I think the reaction will proceed slowly enough that it won't be done after 4 hours. However, at 50C, I think the reaction will be done in less than an hour. The reaction output at 4 hours will be useless--all the B will have been long reacted (i.e. the maximum amount of impurity for that temperature/B input will have formed).

How can I handle the fact that reaction time inputs cannot be assigned randomly?


texts:
I'm planning to build up a big tipi with some friends for relaxing on nice summer evenings.  The tipi is going to be placed on the shore of a medium sized river, specifically the Wertach in Germany (Wikipedia to Wertach (German)).
We also want some electricity there, to run a small Stereo and some light which together use about 100 W.  Therefore we thought about using a waterwheel.

Is it possible to build a waterwheel generator for about 400 EUR? And if it is, how could we do that? I already read that we could use a scooter engine for that.


texts: Struggling to find solution: question 1 (Finding the maximum length possible of a rod with specific stresses in action)

texts:
Could someone please help with the problem below?

Edit 1:My guess on this question is: when I plot in the formulas, the stress rooting from the bending moment overcomes greatly over the other stresses; so if I neglect them, I will still come across a fairly accurate result, but still, please feel free to share your opinions.

Assume you have a 20 [mm] diameter 304 Stainless Steel shaft welded on a rigid surface horizontally (neglect weight). With the forces applied below, what could be the possible maximum length of this shaft?

20 [N.m] torque applied throughout the shaft
10 [kg] load is applied at the end of the shaft
50 [kg] loads of compression force is applied, again, from the end of the shaft
Factor of safety is going to be 1.5

To make things easier I have calculated both $I$ and $J$ beforehand.
$I=7.854*10^-9[kg.m^2]$
$J=1.571*10^-8[kg.m^2]$


texts: What is the thermodynamic consideration so almost all air conditioners are installed on top?

texts:
Almost all air conditioners (AC) are installed on top. For house small office use, will be like the picture. For office with central air conditioner, the blowing come from the ceiling through duct. But however, still there are few occasion where the air conditioner is installed near the floor, like once I saw in a historical cathedral church, due to esthetic's consideration.

My question, is any thermodynamic reason so almost all air conditioners are installed on top? If any, what is that?


texts: When were airfoil cross-sections first used in turbine blades? When did this become standard practice? Did people understand the connection to aircraft, or did heavier-than-air aircraft exist at all yet?


texts: Can a Plasma Cutter use for melt metals?

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Can a Plasma Cutter use for melt metals like Iron, Brass, Stainless Steel ect, ?. Particularly for molding purposes.

If can't, is there any other electric item that doesn't use gases (Acetylene, Butane, Oxygen) for melt metals ?

Edit:

I want to heat a mass of metal up to the melting point and pour that melted metal to a Plaster Parris impression cast. I want to find a electric solution to melt the metal instead of gas.


texts: Control System: offset issue with a simple valve model

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I was reading a paper about a "Controller Design for Temperature Control of Heat Exchanger" and I couldn't understand how to model the valve used in the system.

No need to read the paper as I will wrap up the whole issue:

Given:

capacity of control valve is 1.6 kg/sec
time constant is 3 sec
valve input is pressure varying from 3 to 15 psi

The resulting transfer function is:
$$G(s)=\dfrac{0.13}{3s+1}$$

It is obvious that they considered the valve as a first order transfer function.The gain $K_p$ was calculated by: $\dfrac{1.6\text{ kg/s}}{15-3\text{ psi}}=1.6/12=0.133$. Time constant = 3 seconds and that's it.

But the problem is: shouldn't a step input of 15 psi output a signal (1-exponential) with a final value of 1.6 kg/sec. But that transfer function won't actually output that. It still needs some kind of a shift. So am I missing something? Is the model wrong?

I also simulated the transfer function response with MATLAB SIMULINK along with a suggested alternative that probably solve the offset thing:

The resulting waveform:

The yellow waveform is the input step function

The blue waveform is the output of the transfer function of the valve according to the paper.

The yellow waveform is the waveform with an offset.

Problem with the blue waveform: wrong final value.

Problem with the yellow waveform: starts from a negative value (-0.4 kg/sec)

So what is the correct model?

If necessary, here's the pdf file.


texts: I've drawn an FBD of one leg of the table the picture. I've a feeling I'm missing something. Am I?


texts: Mechanical System Transfer Function - Systems Modelling

texts:
First of all my english writing is not so good, but I can read it without problems.
I've got this mechanical system and I need to get some transfer functions. We made all the force diagrams and got the respective equations, they're eight. Now  we need to get the transfer function of $\dot{x}_1\over v_1$, $x_2\over v_3$, $\ddot{x}_3\over v_4$ and $x_4\over v_7$.

Now, assuming that the equations are correct, what we were trying to do was for the first T.F clear all $X_2(s)$ from the second equation and replace it on the first equation, then we clear all $sB_1$, $B_2X_1(s)$ from the new equation that we just got from replacing $X_2(s)$, then we're trying to make $sB_1$, $B_2X_1(s)\over V_1(s)$ but there's no way to clear $V_1(s)$.

It's very difficult to understand, and I don't know if I explained myself, but if someone can tell us what we're doing wrong I'll be really grateful.


texts:
I have a wave propagation question that regards two materials impacting each other. The question asks to find the impact pressure of the impact with a tungsten carbide flyer and a steel target.

I have calculated my two particle velocities from the left and right going Hugoniot equations however I always have trouble choosing which one is the correct one to use. I know if one is negative that the other is the obvious choice but for this specific problem I have two positive particle velocities. Up to this point I have simply done the calculations with both and decided to choose a reasonable pressure.

I was hoping there was maybe a check I could use to make sure I am using the correct particle velocity.

Thank you in advance!


texts: Autonomous RC car trying to stop at a point

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I am doing a robotics project. The goal is to make an autonomous car start from one point and stop at another point around 10 +-1 meters away. I need to make a steering mechanism. I want to be as close as 3 cm away from the point, so GPS probably won't work.

My ideas:

I cannot have a physical line taped to the floor, so I can't use line following robotics code. But, could I take some sort of electronic device and hover it above the point then remove the electronic device and have the car go straight to where the electronic device was? How would I do this and what would I use?
I have already thought of rotary encoders, but I still need a way to keep the car dead straight for 10-ish meters. My current RC car veers about 20 cm either way. Could I used a gyroscope/accelerometer/imu to help keep the car on a straight line? How would I do this/are the gyro/accel sensors sensitive to notice super fine changes in angle? How will I line the car up perfectly straight?

Please let me know your thoughts!


texts: moment applied causing bending stress in beam

texts:
From the solution , it's clear that the top part of the beam undergo tension , while the lower part undergo compression .

But , i dont understand why it is so . When the moment is applied in the horizontal axis , the structure will slide become like this , right ? ( the top part will be slided into the book )
I cant imagine how the moment applied causing the top part to experience tension , while the lower part experience compression .


texts: Where to fix part in moment setup for FEA

texts:
I'm working on a project that involves supporting a distributed load on a bar that is held up by a moment at one end of a lever arm. My goal is to assess how much the bar bends under the distributed load and how much difference in displacement exists for the actuated and non-actuated lever arms. Here's the setup:

Having done only limited finite element analysis in school before, I'm not sure how best to add constraints. In reality, both lever arms will be free to rotate and will not transfer the moment load past the pivoting axis, where the dashed line is. I did a quick setup the other day where I fixed the bar, but that was more to get a feel for the software I'm using and gave inaccurate results.

Is there anywhere that can be fixed in this setup? The only place I can think of is the structure that I haven't shown in the drawing, which is what the pivot points interface with.


texts: Doubt in triaxial stress state in a notched specimen

texts:
In the book titled "Mechanical Metallurgy" written by G.E.Dieter I am having problems to understand why a notch in a material would mean a triaxial state of stress.I do well understand that notch would create stress concentrations in the material but why a triaxial state of stress is still beyond my understanding.
Somebody told me this,"Triaxial state means "the deformation tensor especially at the tip of notch can't be described by a simple uniaxial compression or tension type of deformations but also involves large shear deformations. Actually for the sharp tip associated stress tensor involves not only diagonal terms but also the off-diagonal terms, which means shear components. "However I do not understand even a part of it.A detailed answer to this is most welcome with the mathematical equations.


texts: O-rings are very common components in all kinds a machinery used to, say, keep a fluid from leaking from one side of a piston to another inside a cylinder. But why exactly are O-rings tori? Why are they not designed so that the contact side of the ring to the cylinder wall is flat? Wouldn't this give a more secure seal?


texts: Best affordable food grade hot water pump

texts:
I am currently building a pour over coffee maker(personal use), but I am having trouble sourcing a water pump to use. I am hoping to create something that performs similar to the Poursteady commercial machine. My current plan is to boil the water to a specific temperature in a kettle, then use a water pump to pump the water from the kettle into the coffee funnel containing the grounds. I'm doing all the automation using an arduino.

Requirements for the pump:

Food grade
Safe to pump ~100c water
A flow rate of >=500ml/minute
Either AC or DC is fine
The more affordable the better.
Self priming

I believe peristaltic pumps, magnetic pumps, and vibration pumps all seem to be okay options, but having zero experience with pumps, I am wondering if any of them are recommended over the other given the specific requirements.

Thanks.


texts: Building a cooling system for a kneading machine?

texts:
I wanted to modify my kneading machine. In fact it can work for at maximum 5 minutes, and then I have to let it cool for 20 minutes (it is a very cheap model), and it is a problem for me.

So I was thinking of adding a sort of cooling system, for instance a fan (like that used in motherboards).

I was thinking of removing the red "hat" of the machine and replacing it with a bigger hat, so that there will be space for the cooling system.

But I have the following questons:

1) Do you agree with me with the position of "cooling ports" from with the air will enter and exit (IN, OUT)?

2) How can I realize the bigger hat? Which material?

3) How can I connect the bigger hat to the machine?

4) I was thinking of doing this modification because it is a cheap model and because I think that the only problem of using it for more than 5 minutes is the excessive heat. So if we solve it with a proper cooling system, I can use it for instance for 20 minutes. Do you agree with me about this last statement?

No problems about the electrical supply of the fan because I will build an external supply circuit for it.


texts: Why are actions combined in this way Eurocode?

texts:
Reading here on Eurocode.
It says that when a cross section is subject to both normal force and moment their effect should be combined like this:
$$\frac{N_{Ed}}{N_{Rd}} + \frac{M_{y, Ed}}{M_{y,Rd}} + \frac{M_{z, Ed}}{M_{z, Rd}} \leq 1$$
Why this? Shouldn't we individually check that the ratio of neither design force to design resistance for force nor ratio of design moment to design resistance for moment are less than one?
Why are they summed together like this? I just don't get the mathematical reason for this.


texts: Why do we get singularities in a solutions while modelling a physical systems?

texts: I wonder why do we get some times singularities (position to be infinity or velocity to be infinity) in the solutions while modelling a real system and in spite of taking all real parameter values of the system. We might have large value(of position or velocity)but why are we getting infinity as a solution. For example, at resonance in spring-mass damper and forced oscillations, at some conditions, I will end up having infinite positon. Why is this happening? In the case of fluid dynamics while using Point vortex models I will have infinite velocity at the centre of the vortex. Why is this happening? even though we follow the proper mathematical approach and always connecting math to the physical system. Suddenly we encounter this Why?. I accept that I don't know much of mathematics or physics .I'm interested in knowing physics and how math is helping us to know physics. This question might be absurd to others for me this is kind of amazing. This puzzled me for a long time.


texts:
Greenhouse have recently caught my attention lately, which yesterday I posted in Why greenhouse's inside temperature never been infinitely hot?

From what I understand recently, greenhouse gases traps the sun heat (infrared radiation) on earth, by making it harder to dissipate back into space, reflecting most of them again. The exact same process happen in hydroponic greenhouse. If that's the case - why then, hydroponic greenhouse inner temperature don't keep increasing infinitely? I mean, if we assume the greenhouse is perfectly insulated transparent container (either by several layer glazing or gas-filled), where sun heat strike daily, and less of that amount dissipate back, Shouldn't it be increasing infinitely? (income > outcome). Because in mine, the temperature tend to be stable. It did always warmer than outer air in certain degree though. Now I assume other than inside reflection, there might also be outer reflection. So not only it retaining existing heat to go out, its also blocking the new one. That's why insulated glass commercially marketed to keep the room inside cool. But if that was the case, then why we should be worry with this greenhouse effect after all? The nature seems always be in equilibrium state no matter what; lots of greenhouse gases = less incoming heat but retain the outcome, little amount of them = more outcoming heat but always up for more incoming one. Or do I missed something?

I still wonder though, if, hypothetically, I have tasked to setup new greenhouse (or generally any container) with main objective to traps sun heat the most inside, how is the best way to do it? (means within same area of space, create hottest possible greenhouses - regardless of the shape, cost, and ambient temperature of surrounding region)
Will insulation (with glazing/gas-filling) do the job?
Or instead of transparent glass, will use black-surfaced metal do it?
I have no physics background whatsoever, so pardon for my shallow understanding of the topic. Any input is really appreciated


texts: Explain pressures created by fluid flow through small orifices

texts:
So my question is in relation to fluid flow and pressure. In my pictures below you can see that i have two similar situations. Fluid flows in from a large reservoir at a constant rate through a control orifice. It follows the red arrow and flows around a 90 degree angle into a tube. Up to this point both scenarios are relatively the same.  We have a pressure tap in both scenarios that differ in size.
Scenario #1 has a small long orifice (0.052in in diameter) that feeds another 0.040in hole in the manifold and then a small volume were the pressure is measured.
Scenario #2 has larger diameter orifice (0.1495in in diameter) that feeds the 0.040in hole into a similar small volume where pressure is measured.
Scenario #3 is the same as scenario 2 except the the drill depth is reduced so that in the inlet orifice matches scenario#1 more closely
What i would like to understand is: why is the pressure in situation #1 (P1) higher than the pressure in the situation #2 (P2) and #3? Pressure measured in #2 and #3 are equivalent.
Wouldn't opening up the holes increase the pressure in volume V1? I have literally tried this by drilling out the tap in scenario #1 to make scenario #2, but it drops the pressure. I have even found that making the orifice smaller increases the pressure. What am i missing here?
Correction: inlet flow is Q=3.876in^3/sec**

Situation #1 Small Orifice Pressure Tap

Situation #2 Large Orifice Pressure Tap

Situation #3 Reduced drill depth so the inlet matches scenario #1


texts: What kind of magnetic water conditioner can industrial sinter plant use?

texts:
As you can see in the below shematic, the magnetic water conditioners can be used for the pipes of incoming process water on sinter plants to reduce surface tension of water and get fuel consumption benefits. But I researched and couldn't find any type of this conditioners/armatures .

Look at first article about this: https://www.steeltimesint.com/contentimages/features/KumarIronMaking2.pdf
This looked unrealistic to some engineers that magnetic water conditioner is not really exist thing.

But..

Please also read: https://www.sciencedirect.com/science/article/pii/S187538921400532X/pdf?md5=3846d794d248117cceb8e706f4b1489f&pid=1-s2.0-S187538921400532X-main.pdf

The above article looks more realistic, so is this magnetic charging chute can reproduce for water as well?

Is there any industrial-scale magnetic water conditioner exist?


texts: (Un)latching component for wearable device

texts:
I'm coming from a product design background and have very modest knowledge about electrical engineering. Please bear with me...

I'm currently drawing a small wearable device and have been looking for a physical (un)latching mechanism. The mechanism does not need to be particularly fast (<1 s), strong (<1 N), nor have a large displacement (~1 mm). The mechanism will be unlocking an object within a bracelet, and will do so rarely - probably just once.

However, the component needs to be quite small (ideal max height ~6 mm), off the shelf (manufacturing aim between 1000 and 5000 units), and be confined to the limited voltage and current from the batteries on wearable things (battery not yet defined).

I've looked at miniature solenoids, geared motors, piezo stuff. But, I feel like there's some component or clever solution I'm missing..?

(I acknowledge this as a kinda non-specific question, but it's sort of a blue pill | red pill decision at this point of development.)

EDIT: adding simple sketch of desired functionality


texts:
There are Tait-Bryan angular changes $(\dot{\phi}, \dot{\theta}, \dot{\psi})$, which describe the angular change rates of the body-frame within the inertial frame (world frame).

And then there are angular change rates $(p,q,r)$ of the aircraft within its own body frame.

To convert these angular change rates between each other, a rotation matrix is needed.

$\begin{bmatrix} p \\ q \\ r \end{bmatrix} = \begin{bmatrix} 1 & 0 & -sin(\theta) \\ 0 & cos(\phi) & sin(\phi)cos(\theta) \\ 0 & -sin(\phi) & cos(\phi)cos(\theta) \end{bmatrix} \cdot \begin{bmatrix} \dot{\phi} \\ \dot{\theta} \\ \dot{\psi} \end{bmatrix}$

Why is that? Why aren't they exactly the same?


texts: What is the difference between a strain wave gearing and a Harmonic drive?

texts: I see there are two different Wikipedia pages for strain wave gearing and Harmonic drive. To my knowledge they are the same. Harmonic Drive is the trademarked name of strain wave gearing by United Shoe Machinery Corp. Am I doing any mistakes here or what?


texts: Why air compressing mechanism "Trompe" is not popular in usage?

texts:
I was amazed when I got to know that there is such a simple mechanism know as Trompe to compress air.
It has no moving parts which make it cheap to construct and do not require any servicing.
Even the air being compressed has negligible moisture and its operation makes less noise unlike the compressors used in industries.
If this system has so many positive points so why it is not used widely? Is it due to its big size?


texts: Did toasters ever make the toasted bread jump up in the air when done?

texts:
In numerous cartoons, video games, movies, etc., I've seen how a toaster makes the toasted bread jump high up in the air when done, forcing the user to catch them mid-air or pick them up after they've come back down, resting on top of the toaster.
In real life, I can't remember ever using such a toaster. The current one we have just makes the toasted bread "go up", but it requires me to manually press up the handle for them to come up to the point where my other hand can pick them up and put them on my plate (with fingers that hurt from the heat).
It sounds absolutely idiotic that it would just launch the slices of bread up into the air. I assume that this is yet another stupid thing in movies/fiction, like how those water sprinklers in the ceiling of office buildings don't all start splashing water all over the entire floor just because somebody makes a fire/smoke near one of them; it will just be that one that "goes off". Anything else would be insanity. Madness. Idiotic waste of money from ruined electronic equipment.
Then again, I also used to believe that a "flea circus" was a joke; that they used nonexistent "fleas" and the whole "show" was just created with tricks and acting by a human. But then I recently found out that they really did train (to some extent) actual fleas, or at least involved physical fleas which had to "perform" as slaves, in the 19th century.
So maybe toast bread which flies up into the air was really a thing after all? Maybe the idea was to have the air cool down the bread so it doesn't hurt your fingers, or something. Who knows? That's why I ask.


texts:
I've been wondering why most (hobby) CNC machines have two actuated linear rails like this:

Besides the extra force for moving the spindle, is there a need for both rails to be actuated? Could the rails not be designed this way:

where the red cylinders are bearings and the yellow is an actuator. Will this setup lock up?


texts: Why don't engineers put tesla valves in the airboxes of carbureted internal combustion engines?

texts:
Before I ask the full question, I want to quickly cover two common issues that come up in high performance engine design.

When intake valves close in an engine a small shockwave moves backwards through the carburetor into the air intake. At higher RPM, this shockwave becomes stronger and can cause the air intake volume to resonate causing a low pressure state when the engine valves reopen. Less charge is delivered to the combustion chamber causing a loss of power. This is referred to as fuel standoff and it normally becomes an issue at higher RPM and high load.
When an engine starts running at higher RPM, the amount of time that valves are open for becomes shorter making it more difficult to deliver a greater charge to the cylinder. Normally cam timing is set with some valve overlap to help mitigate this issue with some success.

There's a way to use the first problem as an additional solution to the second problem. If an airbox is tuned to the right resonant frequency, the airbox will be in a high pressure state when intake valves open at higher RPM. Since this is where valve intervals become short, it allows for more charge to be forced through the carburetor into the cylinder making up for the power loss.
I found some research on Numerical Simulation and Hydrodynamic Design Optimization of a Tesla-Type Valve for Micropumps and couldn't help but wonder why I've never seen a design like this in an airbox. If it's easier for air to enter a Tesla valve than it is to escape, wouldn't some of the energy resulting from the intake valves closing get trapped in the airbox, increasing airbox pressure at a wider RPM range instead of just at high RPM? I'm having trouble applying helmholtz resonance equations to this Tesla type valve because the functional length of the tube is shorter in one direction than it is in the other.
Is there a set of equations better suited to analyze this problem?


texts:
I have an aluminium bearing holder attached to one end of an aluminium plate as follows:

The bearing holder is attached to the plate by two bolts on the bottom. The intended setup is to attach a relatively heavy load to the right hand side of the shaft. To reduce stress on the two bolt holes in the plate, is it a good idea to have a lip on the plate as shown? Will it actually have any effect? Ideally I'd like to fasten the bearing holder through the lip, but I'm trying to avoid machining from the side and stay away from 4-axis machining.
Are there better ways to reduce the stress on the holes?
Any advice appreciated.


texts: Cooling Hot Nitrogen with an aluminum block

texts: I'm designing a cooling system to cool nitrogen gas stream at 300°C with a mass flow rate of 15.6 g/s moving through an undulating channel in a cylindrical aluminum ring block with external fins. How much mass of aluminum or what special feature is needed to cool 15.6 g of nitrogen moving through and exiting to 25°C EVERY SECOND. It's to be noted that the block is immersed in a large pool of water, and that should be factored in as a cooling advantage. I'll love a method of calculation that allows flexibility with variables like mass flow rate, temperature, and channel diameter.


texts:
My friend has proposed that the buildings in the images below have been sinking into the ground over time and that they're not planned with basements.

He thinks that the bottom of the building was once been at ground level and that some of them have windows and doors left from the past. I'm skeptical to this, I can't possibly think that a building can sink two floors down in the ground.

He's arguing that so many old buildings with basements have "misplaced" windows too close to ground level. I'm thinking that it's not possible to have windows or doors underground, as that would pose a risk for mold, water damage, and shattered windows, not to mention the fact that a building would sink 3 or more meters into the ground, how would the engineers not be able to design a foundation that is not able to support the weight of the building.

We really need an answer to this, we're not engineers, and can't find any information online. Please leave sources as well if possible, thanks!

Here is an image

More images can be found at https://imgur.com/a/kdk7AH0

EDIT: When doing a reverse image search for one of the images, it leads me to some conspiracy theory called mud flood, it's the most stark image of them all where it looks like the building has sunken 8 meters into the ground or more it can't have possibly been built like this. Reverse image search on google


texts: For the machine element shown, locate the X, Y and Z coordinate of the center of gravity

texts:
QUESTION:

My working: I had divided the body into 5 common shapes which are shown here:

now that I'm solving for x bar, y bar, and z bar I find it difficult in finding the x, y and z directions.

see my table of working here:


texts: Design table driven equation driven parametric curves for sketches in Solidworks

texts: Do these exist?  I suspect they don't..  Equation driven parametric curves for sketches yes, but not with their parameters set by design  table.. The closest I'll be able to get, I think, is what I'm currently doing, which is using a spline (partially parametric..) and controlling -it's- input via design table..


texts: Why did ramjet AA missiles fall out of favor over pure rockets?

texts: In the 50's and 60's, when anti aircraft missile technology was blooming, many designs used ramjet engines brought up to operating speed by rockets. This seems like a good idea, since ramjets have significantly higher specific impulse than rockets, increasing their range. Over decades however, it seems that the concept has been discarded in favor of pure rockets, with exception of anti shipping missiles. What could be the considerations that made engineers favor pure rockets?


texts: Can a wireless signal of sufficiently high energy damage a wireless transceiver?

texts: A wi-fi router works at 2.4GHz. Can a wireless signal of 2.4 GHz or any other frequency, of sufficiently high energy, damage the device?


texts: deformation / bending problem with anodized aluminium panels

texts:
I recently had a machine shop machine some aluminium panels (3mm thickness) which I then sent to an anodizing shop where the panels were bead blasted and anodized. When they came back they were seriously bent (dimensions of the panel are about 310x130mm).

I did specify 6061-T6 for the alloy but I suspect the machine shop might have used a cheaper non-tempered aluminium.

Is my thinking correct or does this problem come from the anodisation process?


texts:
I am aiming to program a quadcopter flight controller as a personal project.
To be able to do this I understand one of the  fundamentals is a PID control system . So my question is does anyone have any recommendations for books to read or will google be good enough?

I have found the following books , has anyone read these?:
"Advanced PID  control" - here
or ,
"PID Control: New Identification and Design Methods" - here


texts: Why the word "mileage" is used for vehicles, instead of efficiency?

texts:
Why is the word "mileage" used for vehicles, instead of efficiency?

Is there any difference between mileage and efficiency?


texts: Conversion of orthographic projection to isometric projection

texts:
I'm new to engineering drawing, and I am having trouble drawing isometric projection from orthographic projections.
Can someone give the steps/thought process behind this conversion?
I can upload the problem if someone needs an example of what I am trying to say.


texts: Stiff rod / tube - What material and diameter

texts:
I need a long arm which will transmit motion from a motor to a pen. It needs to be about 500mm long.

What I want to try and do is reduce the bend (i.e make it stiff) but also make it fairly light.

Question A)
In this case, am I better off going for a tube rather than a solid rod?

Question B)
Our of the materials available to me (which is carbon fibre, aluminium, steel or wood) - is there any of this which would have an obvious benefit?


texts: How do you select the correct area to consiser for first moment of area calculations?

texts:
I have just begun studying mechanics of materials and I am struggling to understand intuitively how to select the area in first moment of area calculations. I was hoping someone has a relatively easy explanation.
The problem arises when calculating the shear stress $\tau$ at a specific point in a beam due to a specified shear force. For $\tau_{xy}$ the calculations seem to be the same:

$\tau_{xy}$ due to $V(x)$ at point A requires the calculation of the first moment of area, $Q$, shaded here:

However, then the problem requires me to find $\tau_{xz}$ due to $V(x)$ at point B. The shaded area under is the area we have to use, and my question is why?

I know this is probably a very banal question for you guys, but I just really want to understand this, and browsing the web has led me nowhere.


texts: Statics and Structural Analysis: Determinacy in beams/frames

texts:
I have a question about the methods to decide whether a beam/frame is determinate or indeterminate. Typically you can count the number of reaction forces and compare them to the number of elements to determine this. The typical equation for a determinate beam is $r = 3N$, where, $r$ is the number of reaction forces and $N$, the number of elements.

My question is where does this equation come from? I understand that mathematically you have 3 available equations so you can only have 3 unknowns (without an internal hinge or something else). However, I am trying to grasp what this means physically? Is there no physical interpretation of this equation to be had, and it's all mathematical? Do the 3 available equations come from an assumption in elasticity?


texts: How can I deliver a measured amount of liquids through a tube?

texts:
I'm trying to build a device to deliver a N-drop (N * .05ML) of liquid via a tube into a container.  The liquid might change from one application to the next, so it might be water in one, and oil in another.

I've been using an electric solenoid valve that uses a gravity fed vessel into the solenoid input, and controlling the solenoid with an arduino to release a drop from the output end of the solenoid.  Depending on the viscosity of the liquid, I've been able to determine how long to open the valve for.  12.5 milliseconds for water gives me .05ML about 95% of the time, which is more than acceptable for my purposes.

The vessel which is to receive the liquid is below the solenoid,so I've been trying to use a gravity approach using plastic tubing.  The problem I'm running into is that the path is not a straight line down.  While there is always a downward slope, sometimes it is close to flat, so sometimes the drop just gets stuck in the tube.

I've tried tubing made of vinyl, silicone, of various diameters. When the N-Drop leaves the solenoid, it is released into a funnel connected to the tubing.  I use the funnel because this prevents a vacuum forming which will hold the drop with a vice like grip. With smaller diameter tubing the N-Drop forms a "plug" and makes its merry way down the tube.  When it gets stuck, another drop can push this one along.  I can prime the tube with drops, but this isn't ideal as evaporation may come into play.  With larger diameter tubing, instead of a plug, it's more like a blob inching it's way to the bottom.  Once again, on the less steep portions of the tube, the blob sometimes just gets stuck.

There's not much I can do with making the slope steeper.

Can you think of a way of ensuring that the drop makes its way through the tube 90% of the time?


texts: How can I produce two 180-degree intermittent rotations with a Geneva drive?

texts:
I would like to convert a continuous rotation into two 180° intermittent rotations. A standard Geneva drive layout can not do this, is there any variation of a Geneva drive that can do this?

Above is an example of a 4 slot Geneva drive capable of four 90° intermittent rotations.


texts: specific energy consumption vs plant load

texts: often we encounter examples where specific energy consumption of a plant(i.e energy consumption/production rate) improves just by increasing the thoroughput or by "pushing" more load through a plant. I want to understand why. Why does the energy consumption of major equipment (say columns, reboilers etc.) increase non-linearly with mass feed rates?


texts:
I have to approximate the red function with Fourier harmonics.

I am calculating complex Ck the following way.

I am not sure what to put for period - T (6 or 2pi or what?). What integral limits to use (2/6*2pi and 4/6*2pi ??)?
The way I showed on the picture gives me invalid results... so how to fix it?


texts: If you inject cold and hot air in outlets of a vortex tube, do you obtain a greater pressure at inlet?


texts: Why do they vacuum pump the carbon fiber fabric?

texts:
I have seen plenty of YouTube videos in which they use carbon fiber fabric to build various things. One such channel is Mike's Patey's channel where he makes amazing aircrafts from carbon fiber.

In these videos I usually see (but not always) that after they apply the resin to the fiber fabric, they put the structure in a kind of plastic bag and they vacuum pump it.

Why is that process? Is it hardening and giving some extra rigidity to the fiber in any way? Can this process be done by the use of pressure? (eg. a kind of mold that pressurizes the fiber from the outside so that the fiber also takes the correct shape).


texts: Torque output of transmission when accounting for moment of inertia

texts:
A cable drum is driven by 3 electric motors via a bull gear arrangement. Gear ratio, total motor inertia (including pinion gears) and total drum inertia are known. From the motor variable speed drives, the motor angular acceleration and torque are measured.

Can the following formulae be used to calculate how much torque the drum will produce? (And in turn calculate the cable tension)

$$\tau_{out} = {R\tau_{in}-\alpha(I_{motor}+{I_{drum}\over R^2}) }$$

$\tau_{out}:$ Torque out from drum, $R:$ Gear ratio, $\tau_{in}$ Torque supplied by motors, $\alpha:$ Motor angular acceleration, $I_{motor}:$ Inertia of motors and pinion gears, $I_{drum}:$ Inertia of drum and bull gear.

Note that the formulae does not account for transmission efficiency. Where in the formulae would this fit in?


texts: motion tracking (or position tracking) with tilting

texts:
I'm looking for a sensor or a tool for tracking motion on a surface similar to Ultrasound probe, for a relatively small movement, about less than 30cm, and it needs to be able to tilt.
standard computer mouse for example would work fine if I didn't need to tilt and move simuletanousely.
I know it can be done with accelerometer, but according to what I've read it is not practically useful (maybe it's outdated).


texts: Pressurizing Oxygen simply and efficiently

texts:
I am an Indian, ravaged by the Covid-19 pandemic in my country. I come from a non engineering background (Physics). I was thinking about the following.
If one has an oxygen concentrator, i.e. a device which removes impurities such as N2 and CO2 from air, to release pure oxygen (-93%) using electricity.
https://en.wikipedia.org/wiki/Oxygen_concentrator
It supplies oxygen at the rate of 5 liters / min. Can it be used to fill multiple empty oxygen cylinder, which are basically pressurized oxygen kept in cans. This way, if there are multiple patients suffering from Covid-19, they can be supplied oxygen using the multiple cylinders. Is there any simple and efficient way for one to fill the cylinders with oxygen, bear in mind the cylinders are having oxygen at very high pressure.


texts: Would not a telephone call (from the late 1950s) auto-disconnect if one of the parties "closes the handle"?

texts:
In the Alfred Hitchcock Presents episode "Togeather", S03E15, at 17:17, you see a drunk man leaving a telephone without putting it on its handle, with the person he was talking to begging him to "break the connection" because he "needs to call somebody else". The drunk man ignores the voice and seemingly forgets all about ever talking on the telephone, leaving the building. The person on the other end is stuck in a room with just a telephone and is trying to get out.

Is this not a plot hole? Would not a telephone call, now as well as back then, automatically "terminate" immediately or shortly after one of the two "puts the handle in its place"? Why would he be worried about the other side not putting on their handle? Why would that matter?

This makes me wonder. If you could truly indefinitely keep a line open for anyone who calls you, by simply not hanging up on your end, the potential for abuse is endless. I refuse to believe that this was ever the case without some really good proof.

The costs you could force upon helpless callers alone would be enough, but imagine if they need to call the cops or something really important... It simply cannot be the case.


texts:
The given problem asks for the Volume of the given figure below

You have a plane figure that somewhat forms a Two-circular base Paraboloid with radii 20 and 12 cms respectively, and an altitude of 16 cm when revolved about the y-axis. According to the book, the answer is 15,388 cubic centimeters and my answer on my first attempt was 4352pi cubic centimeters. I would like to know if this is an author's mistake or mine.

I used Pappus-Guldinus Theorem  II - The Solid of Revolution to compute manually and used the formula of a two-circular base Paraboloid to verify the answer. But I still ended up getting 4352pi cu cm.


texts: Is there yet such a thing as a "dynamic sheet of paper"?

texts:
I know about "e-ink", but I haven't heard anyone even mention that since like 2006 or something.
I'm looking for essentially a single A4 (or "Letter" size) sheet of paper which is not actually paper. That is, I wish to avoid having to frequently dig out my inkjet printer (which I don't have the physical space to keep out at all times), keep buying expensive ink for it (which likes to dry out if I don't use it often enough), and having to waste physical paper whenever I want to just show a list to somebody in the family, or have a bunch of notes handy which I have written on the computer, for example.
It would be great if I could somehow put a text document onto this "digital sheet of paper" and then it would stick on it as if it were a real sheet of paper, and preferably not require power or any kind of software/OS/booting up. I imagine that there would be some kind of USB-connected minimal wireless transmitter inserted into the PC which I can use some standardized, non-proprietary interface to send data from my machine to the "sheet of paper".
Naturally, I don't expect it to be as thin as a piece of paper, or as flexible. But I just don't want an annoying "device" which spies on me and costs a fortune and eats batteries/power and requires constant babysitting/maintenance. I definitely don't want an "iPad" or any other kind of "pad"/tablet.
Is there such a thing?


texts:
I can deduce the Forces for F1 and F2:

$$\begin{align}
F_1 &= \dfrac{1}{2}\rho g d_1^2 \\
&= \dfrac{1}{2} \cdot (1000 \cdot 9.81) \cdot d_1^2 \cdot 8 \\
\dfrac{F_1}{d_1^2} &= 39240\text{ N}
\end{align}$$

I've moved the $d_1^2$ over to left and worked out the rest.

$$\begin{align}
F_2 &= \dfrac{1}{2}\rho g \dfrac{d_2^2}{2} \cdot 8 \\
&= \dfrac{1}{2} \cdot (1000 \cdot 9.81) \cdot \dfrac{d_2^2}{2} \cdot 8 \\
2\dfrac{F_2}{d_2^2} &= 39240\text{ N}
\end{align}$$

Any ideas on solving b and c?


texts: Selecting the right DC motor for horizontal motion

texts:
I have come across a problem that for the life of me I can't seem to figure out. I'm sharing this here in the hopes that the amazing community here can help push me in the right direction.
The problem goes like this, in my project I require 4 High torque BLDC Motors each having an output torque of 105 N-m or approximately 1070 kg-cm. Due to size constraints we need to go with geared motors. The problem starts here, I have come across a 12 rpm planetary gear DC motor with encoder that has the stall torque of around 584 kg-cm with a gear ratio of 721:1. On further research I can't seem to be able to find a motor with a higher torque than this. I would love to get a guidance from experts regarding what should I do next?
Should I increase the gear ratio or order a custom DC motor more suited to my application.
N.B: Keep in mind this will be used in a vehicle with a load capacity of around 400-500kg. I have verified all calculations and need to source the DC motors now for this load capacity.
I look forward on hearing your views regarding this problem
DC Motor Link: 12V, 12RPM 8110.2oz-in HD Planetary Gearmotor
Edit Update: The project is a automated warehouse management system in which we are developing an AGV (Automated Guided Vehicle). 400-500 kg will be the weight on it after stacking bins on top.
Just like shown in the link: daifuku-logisticssolutions.com/image.jsp?id=3767
We can't go lower than 10 rpm (velocity of 0.11 m/s) since we have to cover 100 m in 15 minutes max. I'm attaching a link for related to the custom build DC motor  directindustry.com/prod/electric-motor-power-pty-ltd/…


texts: Does any know what kind of pump "Colossus" used for saving the Notre Dame Cathedral?

texts:
Does any know what kind of water pump the French Firefighting Robot Colossus used to Help Save Burning Notre Dame Cathedral?
What kind of water pumps do fire fighting vehicle use or fire fighting robots use?


texts: Why don't I see a yellow preview indicator when using the chamfer tool?

texts: I'm having problems trying to use chamfer on an edge. Typically I see yellow previews of how cuts/extrusions will appear, but this is not the case for my first time using chamfer. I have tried looking at tutorials in chamfer, I keep clicking on an edge, but the purple arrows that say flip sides only appears. On most YouTube tutorials the yellow indicators appear after; why don't I see the same thing?


texts: How to use the Ritz method with the weak form to approximate solution of differential equation

texts:
I am having trouble understanding how to approximate the solution to this problem using the Ritz method and the weak form:

$$\frac{d^2u}{dx^2} - u=0; \ \ x \in [0,1]$$
$$u(x=0)=0; \ \ \frac{du}{dx} \bigg|_{x=1} = 20$$

We multiply the strong form of the equation by a weight function $w$ and integrate over the domain by parts to get

$$ \int_0^1w\left[\frac{d^2u}{dx^2} - u \right] dx = \int_0^1 w \frac{d^2 u}{dx^2} dx - \int_0^1wu \ dx$$

$$\int_0^1 \frac{du}{dx} \frac{dw}{dx} dx - \int_0^1 wu \ dx - 20 w(1) = 0$$

which is the weak form. Now, I am confused because when I try to change this into a matrix equation, I practically try to solve

$$\int_0^1 \frac{du}{dx} \frac{dw}{dx} dx = \int_0^1 wu \ dx + 20 w(1) $$

If I try to use, say $$u\approx\hat{u}=a_1 \phi_1 + a_2 \phi_2$$

I should be able to form a linear problem $$\mathbf{K} \vec{a} = \vec{b}$$

where $\mathbf{K}$ is a $2 \times 2$ matrix obtained from the left hand side of the equation where $w \to \phi_i$ and $u \to \phi_j$ to get the entries $K_{ij}$, but this substitution would not work to obtain the components of  $\vec{b}$ since I this substitution gives me terms of $\phi_i$ and $\phi_j$ and this makes no sense since $\vec{b}$ is indexed only by one subindex. I know I am not understanding something, but this was my professor's explanation and I am confused.

Thank you so much for your help!


texts: Can wooden mold be used for blow molding?

texts:
I should have produced a custom designed bottle, but metal molds are some expensive and because we don't require too many products (we just need 100-200 piece), I need a way to reduce the cost.

So I thought that, maybe I can use wooden mold for this. But I don't have experience about that. Is there anyone who has tried/used this method or anyone who has knowledge about that? Is it correct method?

Specs:

Bottle thickens can be same as any water bottle (you can see examples in this search).
Color can be clear or white (clear is preferred)
Some inlet and outlet necks needed (so mold needs to be some complex)
Bottle will be 5 to 7 liters with the shape of like rectangular prism
Material will be derivative of polyethylene probably


texts:
Near my apartment is a building site with a tower crane; great fun to watch of course. This crane seems to have a lift / elevator / vertical-people-transporter (arrowed in the picture).

As far as I can see the lift is only used four times a day (morning-lunch(2x)-afternoon) which is no doubt very nice for the operator but this can hardly be cost-effective. I have seen the operator climb between the operator's cabin and the lift but never any other movement.

Probably there is some other reason for the lift, so what is it? Also, why doesn't the lift go higher? Currently the operator has to climb about 20m, I see no reason why the lift couldn't go 10m higher (the next floor).

PS Tagging was tricky and I don't have the rep to make a "crane" tag. Advice?

EDIT: In response to comments that it might be a climbing crane, added hi-res photos with lift down. There's also a photo with lift up on i.stack.imgur.com/yT6bn.jpg; I don't have the rep to add a link to it.


texts: Why do we ignore horizontal reactions at roller supports?

texts:
When talking about roller supports in a statics problem, we say that the roller prevents only the vertical translation of the beam, but not the rotation or the horizontal translation of it. So there is only one vertical reaction applied on the beam by the roller.

Also, we know a beam is connected to the roller using a pin, and the reaction force is the result of the pin that acts on the beam, as shown in this picture:

Now, suppose that I have a beam that is connected to a roller and I am going to push the beam in the horizontal direction (rollers don't prevent translation in the horizontal direction). What reactions should I expect?

I think that the pin is going to apply a force in the horizontal direction (due to the contact between the pin and the beam), which means that there is a reaction force in the horizontal direction. Is that true? If it is true, then why don't we consider horizontal reactions when analyzing rollers?


texts: Why does a tractor not do wheelie with a lot of weight on the trolley?

texts:
Tractor carries more than his own weight on its trolley. The linkage between the tractor and the trolley is far away from the tractor. So, the whole weight of the trolley is on the back of the tractor. But why does not a tractor do wheelie with more weight on his behind?
To make it understandable, here are some photos I designed:
Tractor with empty trolley:

Tractor with weight on its trolley must be like this but it doesn't happen.

What is the reason for that?