texts: how to filter model-free observations (e.g. Kalman filter)

texts:
Before asking a question, I have no background knowledge of engineering. So I have no idea about these issues like control or signal engineering. (Also, I'm not good at using English. sorry for that.)

I attached the picture related to my question below.
It is time series data and I want to find the black circled points.

1) these data follows Gaussian distribution.

2) The most important thing in this question is that I can't know future data at specific time point. I know only past data at specific time point. I want to recognize black circled points around local max/min points or right after local max/min points.

3) There is no model with these data. e.g. There is no equations like relations of velocity, acceleration and positions. Only these data are the only measurements.

I've got some recommendations to use Kalman filter things, and It helps to make these lines differentiable. Now I'm studying Kalman filter but It seems I do need kinds of model.

Is it possible or useful to use Kalman filter? or, do I have to another methods to filter these data?


texts: How do I know if I need a pull up or pull down resistor for a GPIO pin?

texts:
I've seen many microcontrollers use pull up or pull down resistors either as a setting for GPIO pins or as  part of the hardware.

How do I know if I need a pull up or pull down resistor for a GPIO pin and if I do, how do I know which is right for my application?


texts: How much torque is needed to mix melted marshmallow with rice krispie?

texts:
I am designing a robot to make rice krispie treats!
More specifically, I want to use a fork to mix the melted marshmallow with rice krispie. I am currently specing out the motor, and since marshmallow+rice krispie is not a typical engineering material, I am struggling to find out theoretical viscous force for my mixture, which I think is the main force that my motor needs to overcome. Alternatively, I want to create this scenario in lab and find out experimentally how much torque I need to apply and for how long in order to thoroughly mix the two. One idea I have is to set up a jig that mounts a high torque stepper motor to the fork, spin it about its tall axis, and gradually increase current to observe mixing results. But this method will take some time to set up.
Do you know a quicker and more accurate way I can figure out how much torque I need to apply in order to mix these two experimentally? Or do you know a way to figure this out theoretically without needing to build anything? Welcoming creative solutions!


texts: Pneumatic cylinder force output and impact energy

texts:
I'm designing a little tester for a project which uses a pneumatic cylinder. The pneumatic cylinder's purpose is to apply an impact on a hard surface to test for deflection of the surface. When I looked around catalogs, the pneumatic cylinders have a theoretical force output, for example 3,016 N at 0.6 MPa with an extension speed of 0.8 m/s and a stroke length of 300 mm (preliminary selection although I'm not too sure).

How do I calculate the impact energy upon collision with the hard surface, with this information I currently have? There is going to be an amount of impact energy that I need to achieve.
I understand that when it comes to energy, the formula to use is $\frac{1}{2} mv^2$. What should the mass be? Is it the mass of the cylinder or whatever is placed on the piston rod end (I intend to put some kind of bumper at the end)?
Are "impulse forces" something I should be looking at?

I can't move on to select and appropriately sized pneumatic cylinder for my tester until I understand how to calculate the force output and impact energy.


texts: Sun as water pump in underpressure water power circle

texts:
Introduction
A water storage power plant pumps water up to a reservoir when there is more power available than needed and lets the water flow down when power is needed.
For pumping water up, electricity is needed.
Concept / Idea
I'd like to create a water storage power plant, where the electric pump is replaced by the sun (see also image below):

The sun would evaporate water on the ground.
The water would rise up to a reservoir (as gas).
The water can cool down at the reservoir and becomes a fluid again.
The water is ready to flow down to produce energy.
The whole circle would take place within an vacuum (or near-vacuum) environment so water boils by the sun alone.

Question

Is something like this feasible? Where are the pitfalls?
What is the professional terminology for this concept? (it's difficult to search without one)
Are there any publications/researches regarding this concept? (hopefully some, that usual human beings can understand)


texts:
I am interested in heating coils which are heated using Ohmic/Joule/resistive heating - specifically, how the material for the heating coil is selected.
When I read about heating coil materials - nichrome, carbon fibre etc, the material quality that is mentioned most is electrical resistance (along with a high melting point and stability with changes in temperature). It is my understanding that a high resistance material is typically selected to make heating coils, but how does the thermal conductivity of a material impact the suitability of a material for use as a heating coil?
If two materials had comparable resistance but very different values for thermal conductivity - which material would be the better choice, assuming the goal was a heating coil that heated up quickly using the least amount of electrical power?


texts:
Im working on efficienxy of heavy vehicle. Since i never had any experience with this kimd of things ( cars ) i dont have so much insight in what kind of efficiencys are important in vehicle. I have following insights: Slip efficiency of a tire Motion efficiency Feul efficiency etc.

If you have data on all kinds of forces gears slip and so on of a vehicle. What is there to maximize.


texts: How to calculate added lift from ground effect

texts: I'm trying to build a hovercraft of sorts, and I thought I'd take advantage of the ground effect. I've done some searches, but I can't seem to find any guides on the actual physics. How do I go about calculating the additional lift my hovercraft will receive from the ground effect?


texts:
What key physical, chemical and mechanical properties of carbon ceramic brakes make it better compared to other brakes for example metallic brakes made of cast iron ?
I know that they are much more light weight and can handle much higher temperatures. But what other properties make them better than other brakes ?


texts: Calculating the water pressure knowing the circuit that tracks it

texts:
I'm not very good at physics, but I've got a problem that I really need to solve.

On the second picture you can see a pipe with flowing water. The point of this mechanism is to lit a LED whenever the water pressure becomes too high. We're using a comparator to track the pressure. The piston on the second picture is connected to the linear sliding potentiometer R1.

Known data:

$R2 = 5kΩ$
$R3 = 30kΩ$
Length of the potentiometer $d=50mm$
When the potentiometer slider is at its lowest position, the voltage at its ends is $U=0V$
Voltage provided to the circuit is $U=5V$ (excuse me if I'm not using the proper terminology, I'm not a native english speaker)
Water density may be assumed equal $1000\frac{kg}{m^3}$
Gravitational acceleration may be assumed equal $10\frac{m}{s^2}$

The problem is to calculate the minimum water pressure that would cause the LED to lit.

As far as I understand, the first thing to do would be to calculate the current at the negative end of the comparator. According to the Ohm's law, the current in that branch would be $I=\frac{U}{R2 + R3}=\frac{5}{35000}=\frac{1}{7000}A$. Now the voltage at the negative comparator end is $U=R2\times I=5000\times\frac{1}{7000}=\frac{5}{7}V$.

Now comes the part where I have no idea, what to do. My assumption is that if the voltage at the potentiometer's lowest point is 0V and at its highest point it is (probably) 5V, then it must become $\frac{5}{7}V$ at $\frac{1}{5}\times\frac{5}{7}=\frac{1}{7}$ its length, so $\frac{1}{7}\times50mm=\frac{50}{7}mm$. Even if these ideas are correct, I've got no idea, what to do next. I'd appreciate any help


texts: Elastic thin hard material with dog nails scratch resistant

texts:
Im looking for a an elastic thin material for hinge and running surface for a dog to glue on wood (I would just use wood but i'm afraid it will splinter)
It should be able to bend 45 deg with ease, can bond to wood and is not slipery
Any idea of what I can use?


texts: How is the number of blades on a centrifugal compressor determined?

texts: If I know the tip and hub diameter of a centrifugal compressor ,the inlet velocity and outlet velocity, how do I determine the number of blades on a centrifugal compressor?


texts: Optimum airflow for drying with heated air

texts:
I'm building something to dry glass tubes. It's raised a question which I'd like some background knowledge on before I draw up requirements for the design.

Say I want to dry something with heat alone, then obviously in a room environment (50% humidity, relatively free airflow, atmospheric pressure) heating something above 100°c would quickly evaporate fairly small amounts of water.

Similarly, a powerful enough jet of air would blast off most water, quickly evaporating any remains.

But say I use a heated airflow. Say the heater power is fixed, what would the relationship be between speed of drying and airflow? I think this is a hard question to answer without specifics, but perhaps one question in isolation could be answered:

In principle, for small amounts of water, and a fixed heater power: if airflow is doubled, then the difference in temperature between that airflow and room temperature would be halved. Similarly, if the airflow is halved, the difference in temperature would be doubled. What would the effect on rate of evaporation be?

Perhaps this is impossible to answer without more information, in which case, how might this problem be solved? A compromise would have to be established on criteria like cost of higher pressure air flow generation,  noise levels, power consumption, energy efficiency, rate of drying, surface area of objects to be dried, etc etc etc. Might this be better off just developed with experimentation?

Any level of guidance would be appreciated


texts: How to calculate gear tooth position while assembling a planet gear?

texts:
A stepped planet series gear looks like this:

Given that:

Planet gears are evenly distributed (with 120°)
Sun-gear-1 and Sun-gear-2 is lined up.
Sun gear tooth counts: nS1, nS2
Planet gear tooth counts: nFGS (first gear step), nSGS (second gear step)
Ring gear tooth count: nR1
Ring gear belongs to Sun-gear-1 and FGS
One tooth of FGS and one tooth of SGS is lined up (on the same line to the center) and marked with M.
FGS of Planet-gear-1 is touching the Ring at Mth tooth.

In order to assemble this gearbox:

Make M point of first-gear-step of Planet-gear-1 touch the Ring at Ring-tooth-0.
Make M point of first-gear-step of Planet-gear-2 touch the Ring at Ring-tooth-x.
Make M point of first-gear-step of Planet-gear-3 touch the Ring at Ring-tooth-y.
Roll the Planet-gear-2 to R1/3th tooth of the Ring.
Roll the Planet-gear-3 to R1*2/3th tooth of the Ring.

In this procedure, how do we calculate x and y values?
Example Case

Taken from http://tricolour.net/rohloff.html

I realized I needed to turn each index tooth by 2/3 of a tooth to get it to mesh.

Index tooth (M point) of the gears are marked with a black dot in the picture.


texts: Normal stress - shear stress pairs not lying on Mohrs' Circles

texts:
The three Mohr's circles depict all the possible normal stress / shear stress combinations when material is taken and rotated along one of it's axes of principal stress. Nevertheless, it is clear that rotation around just one principal axis does not yield all the possible configurations. For any point on the Mohr's circle, one of the axes is aligned with one of the principal axes by definition - however, you can rotate a block in such a way so that no axes are aligned with the principal axes.

For example, aligned the axes $x$, $y$, $z$ with the principal stresses $\sigma_1$, $\sigma_2$, $\sigma_3$.  If one rotates clockwise around $z$ by $30$ degrees giving the axes normal to the sides of the block $x'$, $y'$ and $z$, and then rotates about $x'$ by say 30 degrees to $x'$, $y''$, $z'$ none of the axes are aligned with the principal stresses anymore. Such a combination of normal and shear stresses does exist in the structure however.

My question is then: where would such a point fall on the coordinate axes of normal stress vs shear? Would it fall between Mohrs' circles? How do we know such a combination of rotations would not yeild a shear higher than that of the largest Mohr's circle?


texts: Why do cars have mirrors for rear view rather than cameras?

texts:
Despite having so much technological advancement, I wonder why cars still uses mirrors (right and left side of the driver) for the rear view. These mirrors can be easily replaced by cameras and monitors (display for the driver). I noticed such technology exists but it is restricted to only when you take the car in the reverse direction. If we use this technology while driving the car (i.e. in forward direction), I believe it will be helpful for the driver since multiple cameras installed on the rear side of the car will give consolidated view to the driver. Also it will save the hassle of monitoring both the mirrors while driving. I think this will have two benefits:

Since the mirrors will be replaced by cameras, it will reduce the wind resistance for car.
Weight of the car will be reduced negligibly assuming electronic circuits will be lighter than mirrors.

So, my questions are

Why cameras (and obviously displays) are not used instead of mirrors?
Does such technology exist? If it exists then why it is not widely used?


texts:
Has there ever been any experimental verification of the benefits of designing  a gear pair to have a "hunting tooth"?
The idea is to even out wear  by having every tooth on the pinion meshing with every tooth on the gear.
Tooth hunting can be achieved by ensuring no common factors > 1 between the pinion and gear.
Thanks


texts:
Let's say I have a large isotropic body in uniaxial tension, onto which a small rectangular piece of film is applied. Think of a strain gage on a big body, but the 'strain gage' is one single continuous isotropic layer.

Let x- and y-direction be on the surface of the big body and z-direction the normal (piercing trough the strain gage).

In the big body I get $\sigma_x = \sigma_0; \sigma_y=\sigma_z=0$.
Therefore

$$\begin{align}
\epsilon_x &= \frac{\sigma_x}{E} \\
\epsilon_y = \epsilon_z &= \frac{\sigma_x\nu}{E}
\end{align}$$

What is the strain in the small body?

My thinking was: Assuming I have an ideal boundary layer and negligible thickness of the film, the strain should be the same as in the big body. This is consistent with literature for $\epsilon_x$ and $\epsilon_y$.
But I keep reading an expression for $\epsilon_z$ in the small body involving $\nu_B$ of the big body and $\nu_s$ of the small body:

$$\epsilon_{z,smallbody}=-\frac{\nu_s(1-\nu_B)}{1-\nu_s}\sigma_x/E$$

Can someone explain how to get this result?


texts:
I recently was riding my e-bike (with a bldc hub motor) and decided to cool the motor (it -the stator- was approx 100-150 celcius I think) in the river.

The controller is on the top of the bike and definitely stayed completely dry.
The motor has cooling holes drilled in its housing through which the water can flow in.

cooling holes in motor housing:

This method was very effective for cooling but the drive train (motor/throttle/controller/battery started acting up after riding it again after cooling...)

Note: after the motor had dried/warmed up again the issues were gone (not sure what caused the issues so not sure if the water or the sudden change in temperature or something else caused the issues).

Symptoms:
-weird wining noises from motor when accelerating (much higher pitched and louder than normal)
-when the motor reaches a certain rpm (above this rpm) it appears as if the coil groups are misfiring (motor vibrates/shakes and appears to be braking rather than accelerating). The severity of this braking effect appears to be random, sometimes it's worse but not sure why..
The issue appeared to mostly start occurring when  a certain rpm was exceeded but sometimes (less often) the issue also occurred at much lower rpm.
-the issue was gone after approx 30 minutes of riding when the motor was approx 60 celcius (motor housing)(stator was probably approx 80 Celcius).

There is no temperature sensor from the motor connected to the bldc motor controller (the controller does not have this feature).

What might cause these issues?

Can the water entering the motor mess up the signals coming from the hall sensors? If so what causes this?
could the sudden temperature change cause issues similar to this? If so please explain how
Is there another explanation which I did not think of?

video:
https://www.youtube.com/watch?v=l2dHn89Dvso&feature=youtu.be

Thank you!


texts: What gives gas turbine/turbojet engines such high energy density?

texts: What is the cause of turbojets'/gas turbines' high power to weight ratio compared to piston engines? They certainly use a generally less efficient thermodynamic cycle.


texts: Is there a (sort of inverse security) valve which opens if one connected side has a pressure below a certain value?

texts:
Security valves with two connectors open if the pressure exceed a value x +/- tolerance on one side. I'd like to know if there's a mechanical valve which opens if the pressure on one side sinks below a certain value.

The use case is a system with a desired pressure d (e.g. 2 bar), but irregular pressure during operation (because it's based on bio mass fermentation) and a gas storage which stores extranous gas if the pressure is above 2 bar. This storage needs a value which can release pressure from the storage into the system if the pressure in the system sinks below the desired pressure.


texts: How to find diameter of hole for correct assembly?

texts:
I have two disks to bolt with. 4 centrally located holes on each with Pitch circle diameter P and one hole at center of disc.
If standard bolt diameter is B +/- b, what should be each hole diameter if tolerance of drilling hole is +/- h.

For the load rating I got M6 bolts. Their dimensions are 5.85+/- 0.1 mm. And PCD is 10 cm, and I have to bolt it via 4 bolts symmetrically placed and one in center. Drilling of holes on pitch circle is of tolerance 0.5 mm, while central hole tolerance is 0.1 mm. Now, what should be the hole diameters?, so as all four bolts get into and proper fitment occurs.

Thanks.


texts:
Of course, most 2-stroke engines require oil to be mixed with the fuel (I appreciate there are 2-stroke engines that don't require this). Therefore, it makes sense to me that oil will be burnt during the combustion process, given it is mixed with the fuel.

However, what doesn't make sense to me is why 4-stroke engines don't burn just as much oil. In both engines, my understanding is that the oil has to be used within the cylinders to keep them from seizing, so surely a 4-stroke engine would also be burning oil too, with the oil just being added at a different stage?

I would like to understand why 2-stroke engines burn more oil than 4-stroke engines?


texts:
In modeling a wing with the finite element method, I am asked to consider an engine (approximated as a lumped force and moment) and it's mass, inertia, prestress and gravity contributions.

So the engine contribution (in terms of mass and inertia) to the Virtual Work is:

$$\delta \mathcal{W}_{engine} = - \delta s^{T} M \ddot{s} - \delta \theta^{T} J \ddot{\theta}$$

where $s$ is the displacement of the engine.

How should I add the prestress and the pendulum-like contribution?


texts: What has changed since the 1990s that made "LED lights" possible?

texts:
I keep seeing all kinds of objects now having small but very bright LED lights in them, seemingly never burning out, requiring almost no batteries/power, and extremely durable.
I remember being a child in the 1990s and the typical flashlights you could buy were extremely crude in comparison: huge, bulky, metallic, heavy, requiring many large batteries, and requiring the light bulb in it to be replaced. And it barely made much light.
Now, they seem to be able to put a bright LED into any small object which shines way more.
How did that happen? The technology "LED lights" must have existed for many decades prior to the 1990s, even. So why is everything just recently using them?


texts: convert foot pounds of torque on a nut to sideways tons of press

texts: I am putting a tapered splined sprocket on a tapered splined shaft that requires approximately 50 tons of press to seat the sprocket on the shaft. How many foot pounds of torque will it take on the nut to achieve the desired tons of press for the sprocket? The threaded part is approximately 4 inches in diameter. The splined part starts at approximated 4.25 inches and tapers up to approximately 6 inches.


texts: volume comparison of compressed air and gas duster

texts:
I'm currently using 400ml Dust Off 67 gas dusters and want to replace them with compressed air and a blow-out gun.

In order to select the right equipment and get a better understanding I would like to compare the amount of air the gas duster contains to the compressed air solution. I know the gas duster does not actually contain compressed air, but for me it's all about the result. I know how much I can work with the gas duster and want to have a comparison.

So considerung the 400ml Dust Off 67 (see linked datasheet for additional details, I don't know what might be relevant there). If I had a gas container which I can fill up with a pressure of up to 8 bar, how much volume (in liters) would the gas container need to get the same amount of air out of it as I would get the with the gas duster?


texts: Help with determining the dimension change in the xyz direction of a component under a load?

texts:
I'm stuck on this question. I got the first part right which is to work out the dimension change in the x direction but I got the y and z directions wrong. I had to submit this online and it doesn't show what you did wrong so I'm really frustrated on why I got this wrong I was hoping someone could correct me. Since I put my answers online I left the negatives in both my y and z values which might be why I got it wrong I just wanted someone to help to see if I have actually done something wrong.

I forgot to add in my diagram the length of the x which is 200mm sorry. It's in my working though.


texts: Extract information about zeros of system from step response

texts: Is there any way to know whether or not an unknown system has positive or negative zeros just from looking at the step response? This is the step response:


texts: Mechanism to alternate between two lifting ends

texts: I'm thinking of what mechanical mechanism can be used to alternate between two different lifting heads, an adhesive and a non-adhesive side, attached to an arm, so that either head comes forward depending on the position of the arm. E.g. moving it down brings one forward, and moving it back up brings the other one forward. I have explained in detail in attached diagram.


texts:
This may be an obvious question, but here goes anyhow.

If you have two pulleys (different diameters) with infinitely strong bearings and shafts, does increasing the belt tension have any effect on the torque required to turn the system? I.e. Is a super tight belt is harder to turn than a weakly tensioned belt (assuming no belt slip in either case)?

Ignoring the cost and wear implications of doing this as increasing the tension will obviously wear out your belts and bearings significantly faster.

I've done a force balance, and it seems as though, no, everything balances out. If you increase the tension on a belt you're increasing the force on both sides and the torque on the pulley input seems to be independent of the belt tension. When the system is moving at a constant speed under a constant load, belt tension doesn't seem to factor in (again ignoring the loads on the bearings and shaft)

However from a practical point of view it seems to make intuitive sense that if you crank up the belt tension it'll be harder to turn them. Is my intuition wrong, or is there something I've over looked?


texts: How can multiple rotational joints be locked with one mechanism?

texts:
3D Positioner

Recently I used a "3D positioner" made by PMK Mess.  It is pretty awesome -- basically you move it to any position, turn the locking knob, and it stays rock solid.

How might it work internally?

I want to know how it works.  I would like to be able to answer the following questions.

How can the joints be locked in place so well using one knob in the center?
Are there canonical mechanisms that solve this sort of issue?
What are some good resources or references for designing something like this?

It consists of 2 ball joints and 1 DOF rotational joint.  Pictures of each joint are shown below.  I would take it apart, but it's not mine.

Pictures of the joints

Bottom ball joint

Center 1 DOF rotational joint

Top ball joint


texts: GD&T What is the difference between circularity and cylindricity?

texts:
Here is an image from Shigley's Mechanical Engineering Design about circularity...

Now here is another image from the same textbook about cylindricity...

If circularity applies along the entire length of the cylinder then they seem like they achieve the exact same thing. What am I missing? What is a situation where these two would not be the same?


texts: Which program should I use to find moment of inertia of complex sections?

texts:
It is an aluminium section for a mullion and transom and the autocad drawing I have is very complex and I tried using autocad mechanical but it does not work as I am not able to select the area as it is very complex. The properties say that the selection is a closed area however on going to content>calculations>moment of inertia, or using aminertia, I cannot select the enclosed area.

Please give me an application where I can find the moment of inertia and corresponding values.


texts: Derivaiton of maximum deflection of a cantilever beam with intermediate load

texts:
I am trying to derive the maximum deflection of a cantilever beam. L is the length of the beam and a is the where force is applied.
For the case 0<x<a, I use the method below and it gives me the same result of well known formulas.
$$M \left( x \right) ={\it Heaviside} \left( a-x \right) F \left( a-x
 \right)$$
$$\delta=\int_{0}^{a}\!{\frac {M \left( x \right) \partial  \left( M
 \left( x \right)  \right) }{EI\partial  \left( F \right) }}\,{\rm d}x
$$
For case a<x<L, which method should I follow?


texts: How to calculate divided irrigation discharge from a Parshall flume

texts:
How do I calculate the discharge from a Parshall flume that flow over a bulkhead (XY) into three partitions (A, B and C) divided 25%/50%/25%.  There is no restriction of flow when the pipe gates are open (the incoming volume does not exceed the capacity in any of the partitions).  The partitions A & C feed 8" pipe, while the partition B feeds a 10" pipe. When either A or B partitions are closed (using gates A1 and C1), a downstream gate (A2 and C2) can be opened to dump that partition's portion into the 10" pipe (Section C).

If gate C1 is closed (effectively shutting off the water to that pipe), and the downstream gate C2 is closed, what percentage of the water goes into Pipe A and B? (My guess is A 33% and B 66%)
If gate C1 is closed (effectively shutting off the water to that pipe), and the downstream gate C2 is open, what percentage of the water goes into Pipe A and B? (My guess is A 25% and B 75%)

Thanks, Chris


texts: Significance of asymptotes in root locus

texts: What is the significance of asymptotes in the root locus of a linear time invariant system. Does it say that for that particular pole on which it is starting doesn't have a practical pole in the closed loop if the open loop gain is taken to infinity?


texts: How to add a level to component hierarchy in Fusion 360?

texts:
Fusion 360 has the "browser" (tree structure) and timeline to represent the CAD model.

When I realize I should have created a parent component for an already existing component, how to do this?

In the picture, I wish to create a component LockBogie that would wrap the already created component Lock underneath it.

I tried this:

rewinded the timeline to prior of creation of Lock
created LockBogie there so it would be available as a parent for Lock

Then comes the dead end.

My first intuition was to edit the creation step of Lock so I could have reparented it. There's no "edit" or "reparent" option.

Second, I went to the browser. Maybe I can drag Lock to be within LockBogie (LockBogie was the active component when I tried this). Nope. Dragging is not allowed, it seems.

Adding a level of component hierarchy afterwards feels like a relatively common thing that should be no-fuss. If you have done it, please tell how you did it.

Disclaimer: This question is particular to one tool. I will likely post it in the Fusion 360 forums as well, but wanted to probe how beneficial the Engineering SO could be in coming to solutions. If the general guidance states the site is for non-tool-related questions only, I will certainly remove this. :)


texts:
I'm simulating a turbine.

The convergence of solution is monitored by checking the residuals of the numerically solved governing equations.
The "viscous-spalarat-almaras" model is used, and used air with constant density. Pressure-velocity coupled scheme and pressure based solver are selected.

According to the following figures, torque is increasing but the residual of continuity does not decrease and is almost constant. T

Click on image for a larger version of the image.

Click on image for a larger version of the image.

Is there any problem?

According to monitored torque, the solution is not converged.


texts: How can I calculate the stresses and limits for the physical lowering of in-service pipelines?

texts:
Sometimes underground pipelines are exposed due to vertical scour or lateral migration of streams (or other erosion). One option is to lower the (in-service) pipeline to a new depth that provides sufficient ground cover.

How can I determine the mechanical stresses on the pipe, and determine how much the line can be lowered? Also required is determining what length of trench will be required to accommodate the lowering. What are the relevant codes or standards?

This question is in relation to steel pipelines for both gas and liquids.


texts: How do mechanical keyboard switch mechanisms relate to the force graphs?

texts:
I'm not sure if this is the right place to ask, but I'm curious about what contributes to the asymmetry of force-distance graphs provided by keyboard switch manufacturers?

For example, it is common to see graphs that look like this online:

Accompanied by gifs of the mechanism like this:

The mechanism here and what I've seen of actual keys look symmetrical in that there's no reason for any difference between pressing the key and the return of the key. So why is there the reduced amount of force on the return?


texts: Localized stabilisation of Lunar lava tubes

texts:
A study from Purdue University suggests the Moon contains a number of wide underground lava tubes, up to 5000 m wide and about 1500 m high, in which subterranean cities could be constructed. Such tubes would protect potential residents from cosmic radiation and from the extremes of temperature on the surface.

Prior to constructing anything in such tubes the inside of the lava tubes would need to be inspected for integrity of the rock and where localized weaknesses were found these would need to be fixed. The risk of a rock or a wedge of rock dislodging from the backs/roof/ceiling or walls of the tube and falling on people, plant, equipment or buildings would need to be to mitigated.

What would be the best way to stabilize any local weak spots in the internal surface of the lava tubes?

For example, here are some common tools and techniques for adding stability to natural and engineered structures:

Tensioned cable bolts
Rock bolts
Shotcrete
Shotcrete, steel mesh and bolts
Concrete lining via form work, as opposed to shotcrete
Polymer coatings
Ceramic coatings


texts: What size aluminum beam and cable do I need?

texts: I am building a small project at work and need to figure out what size beam I need.  I am basically building a wall mounted jib crane.  The beam will be anchored to a wall on one end and will have a cable running from the end of the beam back to the wall 3 to 4 feet above where the beam is anchored.  The beam needs to support a 5 lbs per ft hose along the entire length and a 50 lbs weight at the end furthest from the wall.  The beam needs to be aluminum but the cable can be steel.  What size beam and cable do I need?  And is that enough of an angle for the cable?


texts: How does width and thickness affect the stiffness of steel plate?

texts:
I have a 2 mm thick steel plate which is 300 mm long and 30 mm wide, supported at either end. It supports a weight-bearing wheel that can roll along the plate. It currently supports the maximum weight that I expect it to support when the wheel is in the middle, but it flexes a little bit too much. Would making it wider help to support the weight and increase its stiffness, or do I need to make it thicker?

Also is there a way to calculate how the stiffness will change with the thickness (or width if that would affect it)?


texts: What is meant by "accuracy within factor of 2" in sensors?

texts:
I've spent quite some time googling the meaning of "factor of (number)" in sensor accuracy but could not find any document explaining the meaning of this expression used to describe sensor accuracy. Specifically, I'm looking for the meaning of "factor of 2" in the below sentence:

  "Detectors should respond to gamma radiation photons within any energy
  range from 60 keV to 3 MeV with a dose rate response accuracy within a
  factor of 2 over the entire range"

[Extract from NRC Regulatory Guide "Instrument for light water cooled nuclear power plants to assess plant and environs conditions during and following an accident (page 1.97-14)"][1]

I know that accuracy is usually stated like "+/- 2% over the sensor range". This, simple and straight forward expression is easy to understand. For example, if a tachometer has accuracy of +/- 5 rpm over the range of 100 to 1000 rpm and the rpm measured by the tachometer shows 500 rpm, then it can be said that the actual value is within 495 to 505 rpm.

I understand that increase/decrease by a factor of 2 means multiplication/division by 2. Am I correct to say "if the detector indicates 100 keV, the accuracy should be such that the actual value is within 50 keV to 200 keV"?


texts: 4 Gears in a Circular Pattern - Calculating the Proper Distances for Meshing

texts:
I have recently been working on a gearbox for a robot.  I have this pattern of 4 gears with each gear connected to its 2 neighbors.  It looks like this:

You will probably notice something though.  Large gear on the right and the small one in the center do not properly mesh.  I made sure that the center to center distance of the all the gears was the sum of their respective pitch radii so that is not the issue:

There only seems to be a few positions where the gears engage one another properly.  By moving things around and eyeballing it I got a set of constraints where everything appears to mesh properly but it is unlikely that it is perfect:

So my question is how do I calculate distance between the small gear in the center and the large one on the bottom so the gears will all mesh properly.  I don't like eyeballing it because I don't think the gears will mesh perfectly.
 Also, it makes it harder to improve my design if I can't make these calculations.

Thanks,
Ben

Some specs on the gears:

Large Gears:  44 tooth, 2.2" pitch diameter, 2.3" outer diameter, 14.5 deg pressure angle, 20 Diametrical Pitch.
Small Gears:  12 tooth, 0.6" pitch diameter, 0.7" outer diameter, 14.5 deg pressure angle, 20 Diametrical Pitch

A similar question that got no answer: How to find angle of timing gears


texts: Involute gear curve when root diameter falls below base diameter

texts:
The answer to a question on involute gear curve calculations shows how the gear tooth curve proceeds as an involute calculation from the base diameter.

If the pitch diameter is D = m.N where N is the number of teeth and m is the modulus (for metric gears), then the base circle diameter for a pressure angle α, most usually 20 degrees, is D.cos α and the root diameter is given by the amount the tooth falls below the pitch circle. This amount is the dedendum and is usually 1.25m. Thus the root circle diameter is D - 2.5m.

The involute is calculated in a standard way and looks like the unwinding of a string from a circle, the base circle:

The gear tooth is then described by the intersection of the involute with the root diameter (the bottom of the tooth) and the outer diameter (the top of the tooth). An issue arises if the root diameter is less than the base diameter as the involute is not defined below the base diameter (you get a math domain error in Python if you try it!).

These tooth are described as "undercut". I cannot find a description of how the curve proceeds once you "run out of involute" - ie cross the base diameter.

Is there a standard way of describing the rest of the gear tooth curve?


texts: Process changes in mechanical copper parts (stress relief)

texts:
Having some issues with assemblies, I try to explain my question with some introduction.
Let's say, there's an assembly with two parts. Copper (OF / K30) and FR4. The copper part is milled from all sides extensively.
In the process both parts are mated at several points with bolts.
Later in the process the mated assembly undergoes a baking process for 48h 24h and 80°C.
We notice some deviations, the FR4 parts are dislocated along the mating plane. Those deviations might point to strong forces during the process steps between fastening of the bolts and final checks after the baking process.
K30 having a CTE of 17.7 ppm/K is not that far from FR4 (14-17 ppm/K). For my question I make the following assumptions:

baking temperature has not crossed Tg of FR4 by accident, where CTE is known to change drastically
alloy and FR4-type have not been exchanged accidentally
fastening of the bolts have been performed properly and the parameters haven't changed

What process changes during manufacturing of the copper part can lead to a displacement of the mated parts during the heat treatment?
update
The baking process itself is under heavy scrutiny on itself. So of course I'm interested in everything what can happen during that step as well. However my question aims on everything what can happen to the copper part before assembling it with the rest.


texts: How to measure calories actually burned from exercise?

texts: I'm just an average person who questions the validity of my treadmill's claims about how many calories I've burned after an hour's worth of a cardio workout.  How can I get a more accurate measurement based on pre and post workout conditions?  I suspect the most accurate approach is to use rather sophisticated/expensive equipment (i.e. things I don't have/can't afford), but I'm also curious if there is a low cost/low tech approach to measure calories burned without relying solely on a heuristic formula?


texts: What are those large cylinder "tanks" attached to the outside of trucks for?

texts:
I've noticed this a few times, the last time today:

It's a big cylinder-shaped "tank" (for water?) outside of the front part of the truck. What's the purpose of this thing?


texts: How many kWh this turbine would generate?

texts:
My grandfather and I are running some experiments down the river, however we don't have expertise in engineering so I bring up this question to the community and hope someone could help.

How many kWh a turbine with the following features would generate?

These images are just a simple prototype which does not apply some of the following features:

Shape: Reel.

Length: 1.50m.

Diameter: 1.20m. (Including its palettes and axis which has the thickness of 20cm.)

10 Longitudinal/helical palettes with length of 1.50m., thickness of 2cm. and height of 50cm.

Total weight: 50kg. (Palettes and axis included for torque boost.)

Flow rate (amount flowing through the device): 3m³/s

River conditions:

Flow rate: 209.000 m³/s

Speed: 2 meters per second.

Depth: 40m.

It would be installed 2 meters beneath the river surface, placed horizontally.


texts: What are the hypersonic Normal shock relationships?

texts:
I am learning about hypersonic flow now and there seems to be a lot of discussion about the oblique shock relationships as the Mach tends to be very large.
I was wondering what happens to the normal shock relationships as the Mach number tends to be high and I can't seem to find anything about it. Is it because it is not possible to have a normal shock at hypersonic speeds?


texts:
I'm new to part design/mechanical engineering and I have the following question.

Blue: steel shaft, 5/8" diameter, connected to a motor
Green: aluminum disk, 10" diameter, 1/2" thick, 3" hole
Goal: the shaft should rotate the disk

The Question: I'm wondering how can the shaft be connected to the disk?

I tried searching for bushings, various forms of couplings, etc, but couldn't find anything that can connect the two.

Does this mean I would have to machine my own coupling, and there are no standard fittings/parts that would do the job?

FYI, the project needs high torque, so I'm guessing (please correct me if I'm wrong) that a coupling needs to have a large diameter as to apply the torque at a greater distance from the center.


texts: Relating internal stress of an o-ring due to thermal expansion to amount of free volume in a gland

texts:
I am trying to come up with an analytical way to determine the optimal gland size that an elastomer o-ring will sit in. The amount of free space in the gland is determined by the thickness of two backup rings that surround it. Thus, the thicker the back-ups, the less free space to allow for thermal expansion.

My first step was to determine the internal stress on the o-ring due to temperature:

Coefficient of Thermal Expansion, $\alpha = 1.6\times10^{-4}\ \mathrm{\frac{in}{in-°F}}$

Modulus, $E = 1900\ \mathrm{\frac{lbf}{in^2}}$

Temperature, $\Delta T = 400 \mathrm{°F}$

Stress: $$\begin{align}
\sigma=E\epsilon=E\alpha\Delta T &= (1900\ \mathrm{\frac{lbf}{in^2}})(1.6\times10^{-4}\ \mathrm{\frac{in}{in-°F}})(400\ \mathrm{°F}) \\
&=122\ \mathrm{\frac{lbf}{in^2}} \\
\end{align}$$

This where I am stuck relating this back to the dimensions of the gland. How can I move forward in order to relate this to the amount of free space in the gland? Assume worst case when the o-ring is fully constrained with no room for expansion.


texts: Balancing a horizontol flat surface when weight applied to one side

texts:
Thank you for taking time to assist me.  I have a rectangular surface that i want to hang from it's 4 corner points.  The corners on two sides could be joined together clipping on to a centre support beam (like in my excel drawing - sorry only software I have available) and then the support beam is hanging from a centre swivel hook which hangs from the ceiling.

My question is how would one achieving horizontal balance if a weight was placed off centre on the horizontal surface.

I can't use a vertical counter balance so have tried looking at linear counter balance.  I have found some examples online but have no idea how this would be implemented here.  I have no engineering knowledge so any assistance would be greatly appreciated.  If you could even just tell me what I should be searching for.

Thanks]1


texts: How to apply the permeability value found from an experiment?

texts:
I have done a permeability experiment on LDPE in the presence of air using a 25mm circular specimen. At 30'C, the permeability was found to be 1.846 barrer.

Now I am trying to apply this permeability value to a calculation whereby I am trying to find what the change in pressure of a dunnage bag is (it is a bag that has the shape of a pillow) after 5 minutes. I have the following info of the dunnage bag:

Volume of bag = 0.2064 m3 (This was calculated using the Paper Bag Problem)
Approximate area = 1.35 m2 (this is just a quick approximate)
Thickness of LDPE = 0.042 x 10-3 m
Time = 5 x 60 s = 300 s

Is it correct if I convert barrer to SI units in the following manner:

1 barrer = 7.5005 x 10-18 m2s-1Pa-1

By using the following formula, I was hoping to calculate the change in pressure. However, my values don't make sense at all!

$$\text{Permeability} = \dfrac{\text{Volume}\cdot\text{thickness}}{\text{Area}\cdot\text{time}\cdot\text{Change in Pressure}}$$


texts: Saturation Temperature of Binary Mixture

texts:
I have a binary mixture of water and methane. The system is at 2000kPa and I am trying to find the saturation temperature of the water in the mixture.

I know Tsat is a function of partial pressure, but cant find a formula. I do not know the ratio of water to methane in the system.

I do know that the system is currently at 100C. If I assumed that 100C is the Tsat for the water, is there a way to calculate the ratio of water to methane?


texts:
Many consumer grade pressure washers specify a minimum pressure for the supplied water, which is sometimes well above the low end of household water pressure.  Our water pressure is often low and I'm looking for a way to verify without a pressure meter that it is adequate for this purpose.

Data from the utility company isn't useful.  The pressure is very affected by the usage of other houses in the area, plus there are endless effects on the pressure between the water meter and the hose bib.  However, I can use the water at off-peak times and test it at the hose at the time I want to use it.

The formulas I've found online tend to deal with what happens inside the pipe or between one point and another.  They require all kinds of parameters that aren't really relevant to this problem.  I'm only interested in what comes out the end of the hose.

I know that for pressure washer nozzles, the area of the hole relates the flow rate to the pressure, and one factor can be calculated from the other two.  A garden hose is at a very different scale; characteristics that influence flow at high pressure on a tiny scale aren't likely to extrapolate well.  Nevertheless, the same physical laws should apply.

The end of the hose is a 3/4" hole and I can measure the GPM coming out.  Can the PSI of the system driving the water out of the hose be calculated from just those two factors?

I've looked at the standard model of a water tank with a hole in it, which would seem to represent this.  However, the results were nowhere near the same ballpark as household water pressure.


texts: Are electronic cigarette "atomizers" just evaporating the fluid?

texts:
Electronic cigarette elements that heat the fluid are usually termed "atomizers." They are usually just some nichrome wire or similar wrapped around a wick that becomes saturated with the nicotine fluid.

What is the process that "vaporizes" the fluid? Does the element just heat the fluid until it evaporates? Or something else, e.g., is the majority of fluid sort of spattered off the wick due to a smaller proportion of it violently evaporating? Or some other process/phenomenon? Is the term "atomizer" a scientific term in this context, or just something adopted for electronic cigarettes?


texts: How to prevent shorts between exposed battery terminals and racing vehicle chassis

texts:
I have a small issue that is causing a lot of problems. I'm on a Formula SAE team and our battery is consistently shorting between our positive terminal and our chassis. Our chassis is the grounding point.

Our battery is underneath our seat, our seat is made of carbon and therefore when the driver moves shorts occur. I've tried using tape, rubber covers and plastic boxes. The box cracks under the weight of the driver and the tape and covers fall off during a long race.

How can I prevent shorts with a solution that wont break, nor fall off?

In case a short does occur, we use breakers.

Below is a sketch of the position of the battery under the seat. At point one, when we are static, the seat does not touch the battery, but under high acceleration, the driver will rub on to the battery terminals. This knocks off tape and covers that are on it. In the course of a long race, eventually shorts start to occur after the tape/covers have been rubbed off. We noticed that the issues happened on tight turns and moments of high acceleration.


texts: How to strengthen existing masonry vaults and domes?

texts:
I would like to know what methods are usually used to strengthen existing masonry vaults and domes, especially the ones called Catalan Vaults, and how to design them.

Thank you in advance.


texts:
I would like to design a 3.2-inch LCD display onto a product. The best aesthetic I have seen is using a flush glass screen front face.

My product does not use touch screen. How would I go about sourcing say 4-inch glass panels? Is this sort of thing available somewhere off the shelf? Or is it something that you need to get made custom?


texts: How are three satellites sufficient to find a unique point in GPS? What happens in case of an overlap?

texts:
Consider:

Is it because the 2nd and 3rd satellites' centres are collinear? Can a satellite overlap happen? If so then how is it avoided? If not avoided then what happen to the signal that is sent from such a satellite?
This is just a 2D representation. The same concept can be applied in 3D.


texts: Electromechanically open and close a small, hinged door?

texts:
I have a chicken coop I plan on modifying to automatically open and close the door at dawn and dusk.

What sort of actuator or mechanism would be appropriate for operating the small, side-hinged door?

Constant power is not available (solar) plus it needs enough holding force to keep foxes out.


texts: Calculating pretension of a spring with an initial tension

texts:
Simple one. Some extension springs are wound with an initial tension which acts to pull the coils together, even when not under external loading.

When calculating the preload in the spring, should the initial tension be added to the spring force (e.g. initial length x spring rate)? I have seen a few examples and some people include it, others don't. Which is correct?


texts: What shape of object will roll down the fastest through the decline piece of wood on Earth?

texts:
What shape of object will roll down the fastest through the decline piece of wood if travelling  with a straight line assuming there are frictionless ramp to stop them from going to the side given the same amount of material with their smoothness being the same? Could it be sphere or a partial sphere with cross section trimmed off? Please also including the distribution of the mass. Is the mass focused in the center given much faster velocity to roll down? What about the 3D shape generate from other curve for example, elliptical or hyperbola, etc...

Please show your math formulation...

In addition, I know that a hollow cylinder will roll down slower a solid-centered cylinder.

interesting video: https://www.youtube.com/watch?v=cB8GNQuyMPc

Interesting thing to learn from this video is that the density doesn't matter, bigger cylinder VS smaller cylinder are the same, even the weight doesn't matter in his experiments...


texts: Why can we extend the derivation of delta(S mix) to ideal solution from ideal gas behavior?

texts: The formula for change in enthalpy for ideal gas is derived using ideal-gas law which cannot be extended to ideal solutions (my intuition). Then why can we extend the formula of delta S mix to ideal solutions from ideal gas.


texts: What type of engineer/professional designs hydroponic farms?

texts:
What kind of professional/architect/engineer builds agricultural systems, specifically automated hydroponic systems?

Things such as growing, cultivation, lighting, plumbing, harvesting, processing and packaging systems, all in one facility, much like a factory.

For example, if I wanted to setup such a facility, who would I have to consult?


texts: I'm interested in locating a database containing the elastic constants (the tensor matrix) for a variety of materials (preferably for a variety of symmetry classes). I don't have a particular material in mind, so just some general list would be very helpful. If someone knows of a good resource I'd appreciate it. Thanks in advance.


texts: Clarification on specific heat of materials

texts: At a temperature of 25 °C, the heat required to raise the temperature of 1 kg of water by 1 K is 4179.6 joules, meaning that the specific heat of water is 4179.6 J·kg−1·K−1. Does this also mean that to reduce temperature of 1 kg of water by 1 K, 4179.6 joule heat has to be removed?


texts:
There's a simple way to lift a platform a short distance:

Identical discs are mounted on a frame at the four corners of a
platform such that front pair of discs' axes of rotation are
colinear, as are those of the back pair.  The front and back axes
are parallel.
Each corner of the platform (at rest) is mounted to its disc at the same offset (and angle) from the disc's center.

When you lift one end of the platform, all of the discs have to turn identically, so the platform rises parallel to its at-rest position.

What is the formal name (e.g. crank-slider) of this mechanism?

I've been searching the Internet for parts and keep coming up with harrows and cultivators (farm equipment for plowing).

EDIT I'm building a rack to store eight snowmobiles in two rows - one above the other.  I have maybe an inch to spare width-wise, so the solution has to be fairly thin, and the ceiling is already too low.  Fortunately, the top row can sit below the tallest bits of the bottom row (the windshields and handlebar loops can project into the upper level without being run over).  But the back halves of the upper decks need to lift 4-8" to allow sleds to move into the lower level.  Discs are not only thin, but their rotation when the deck is fully lowered could be at an angle where raising the deck could combine pushing with lifting, rather than just pure lifting.  When raised, their rotation would be just past 12o'clock so they are "locked" by gravity, and "unlocked" with a slight pull.  (The decks would be unloaded when raised and lowered, else they would require power and vertical clearance that I don't have.)

I'd rather find a manufactured thin-disc-on-a-thin-bearing but I have no idea what it would be called.

Thanks for any help.


texts: How do I properly store lead-acid batteries?

texts:
I am working on an off-grid solar project, and I need to store the energy my solar panels produce in batteries. I will use sealed lead acid batteries because they require little maintenance and are less expensive than lithium batteries.
Lead acid batteries perform optimally at a temperature of 25 Degrees Celsius. To save money, I will build an enclosure for my batteries using wood. Since I am off the grid, I do not have a HVAC system installed. I will have a fan and a space heater, but these heat and cool unevenly.
How should I go about storing my batteries so that they do not experience temperature extremes and are properly ventilated?
After accounting for losses due to inefficiency, to meet my energy requirements, I will use 12 Crown 6CRV220 batteries. I will 3 sets of 4 batteries in series and wire all 3 sets in parallel. The entire battery bank will be 24 V and 660 Ah.


texts: Stopping Force of Irregularly Shaped Object

texts:
I have a quick question about the force needed to accelerate/decelerate an irregular object.

Lets say I have a 3D object with the following general shape,

This system is in general a gripper (gray) holding a load (yellow) and fixed onto a translating horizontal beam (blue).

I was thinking, to calculate the stopping force of the load and gripper, I just would need to find the center of mass of the load and gripper and apply Newton's Second Law with the expected acceleration/deceleration?

Or does using a center of mass calculation with Newton's Second Law result in a large error from the actual system behavior?


texts: identify shackle or swivel tensioner mechanism

texts:
What is this called? I would say it is a shackle or I suppose, a turnbuckle, but it appears to have a right threaded rod on both sides and right threaded free nuts inside.

I would just say it's a shackle or maybe a swivel, but there are some really important design properties that aren't specified by that.  I want to say something that is usually about 5 to 1 length width aspect ratio, has a hole in both ends, has a wide berth for inserting and tightening free nuts and seems to have some kind of in the field bending and maneuverability capability.


texts: What do I call this "cogwheel" that feeds tin cans to a specific position?

texts:
This is an above view of a system in which tin cans arrive via conveyor (1) to a "feeding star" ("подающая звезда" in Russian; No. 5) and are placed firmly in slot 4. (source in Russian)

What does one call this "feeding star" in English?
I'm actually translating a text about a pharmaceutical filling-and-capping line, in which there is a "feeding star" and a "stoppering star". My text comes with no drawings, but I googled and found out that these "stars" are basically star-like cogwheels that take something from a moving conveyor system and position it precisely for further use. In my text, this "feeding star" probably passes drug-filled vials to the "stoppering star" which is part of the vacuum-operated automatic stoppering unit.


texts: In Control Systems Engineering, why do imaginary poles and zeros on the LHP indicate stability?

texts: I understand that poles on the left hand complex plane (LHP) make a continuous linear dynamic system stable. What's so significant about imaginary poles on the LHP that make a system stable? What does it mean to have poles and zeros on the LHP verses the right hand plane (RHP)?


texts: derivation of Young's modulus experiment formula

texts:
In an experiment used to find the Young's modulus of a steel bar, the formula for change in height is given as follows:
$$\delta_x=\frac{Fx^2}{6EI}(3L-x)$$
$$I=\frac{bh^3}{12}$$
where:
    $δ$- the change in height of the steel bar under load at a distance L

$δ_x$- the change in height of the steel bar under load at the point where deflection is measured

$L$- the distance between the point of application of the load and the end support

$x$- the distance between the point at which deflection is measured and the end support

$E$- Young’s modulus

$F$- applied load

$I$- second moment of area of the cross- section

$b$- the width of the beam

$h$- the height of the beam

$w$- the weight of each value in the weighted mean

$m$- the mass hung from the bar

The problem is outlined below:

The problem is that I do not understand how they have derived this top formula. Thanks in advance.


texts:
How do i calculate the load of a glass facade and is it placed uniformly on the edge of the slab or should i place a point load on each edge of the panel of the facade?
And Can anyone give me a link on an example on how to calculate the load and how to place it.
Thank you in advance,


texts: The variation in efficiency of hydraulic machines

texts: Why does the efficiency of all hydraulic machines increase initially with increase in discharge and then decrease on further increase in discharge?


texts: I Say To myself:"I Am An Engineer!"...How Do I Arrive At That Point?

texts:
"Ponder the path of your feet, and let all your ways be established." Proverbs 4:26

Over the last two years I have had a strong will to become an inventor within the field of
computer-technology/robotics,a field where I have many visions and concepts for projects,
and have been persistent and consistent in my ways, so that I may reach a point that I
can assume the title of engineer.

I'm currently working full-time(lot's of over-time as a laborer), yet with all my free time I try to mold myself
into the man that can execute these projects I visualized. I'm currently trying to design and develop my first project, and I wasted a lot of time picking different books
up, not knowing where to start my research and discipline.

Should I have started with programming? Electronics? Mechanics? Eventually I realized that I had a strong
apptitude for mathematics, and decided to order a used college algebra book from online, and I have been making
progress ever since(would be done with the txtbook if it wasn't for the amount of hours I worked every week.)
    Electronics was a path that I always felt was on this path that I am becoming aware of, and in different periods
of my life I would find myself picking up Eectronics books and for reasons beyond my understanding I would never get far.

Yet now that I have developed a solid foundation of mathematics, I am beginning to understand and comprehend Electronics
theory, and I am confident that I can now begin to progress to tinkering with components.
    I have also decided that maybe it would be a good thing not to try to discipline myself so much, so I
have enrolled into a computer science degree program, and my long term educational goal Is to become a computer engineer.

With all this being stated, what is the path? We all have a journey, we all have a point in space-time that we
have visualized, but how do you arrive at that point? How do I arrive at the point where I have designed and developed
my first robotics project?

I'm seeking feedback from the community so that I may arrive at this point as efficiently as possible. Thank you.

**P.S.: Excuse me for my lack of formatting, this is only my second post on Stack-Exchange, and it is a learning curve for me.


texts: Do concealed door closers exacerbate wear on a door's hinges?

texts:
Not being of an engineering background, I was first inclined to think that a door closer would reduce horizontal load on all hinges and not contribute any support in the vertical dimension.

However, bearing rotational mechanics in mind, is this necessarily true?

I think, on any normal door:

The upper hinge would be under horizontal tension.
The lower hinge would be under horizontal compression.

If a concealed door closer (similar to the model in the lower image) is installed into the frame below the center of mass of the door, would it exacerbate load on the hinges rather than protect them?

Concealed door closer, mounted in the jamb, providing constant spring-loaded compressive force.

Would it contribute anything to the vertical load on the hinges?


texts: What does 'Analysis Model Value' in NASTRAN optimization mean?

texts:
I am new to MSC NASTRAN and PATRAN.
I am running a simulation on composite laminate optimization. While creating the design variables for the study, I noticed that there is a parameter called 'Analysis Model Value'. I am unable to understand the physical significance of this term. I searched the documentation provided by MSC but I am still unable to come up with a solution.


texts: How to professionally mount an air duct through a core hole in limestone brickwork

texts:
We need to add ventilation holes to an existing building. The holes will be core-hole drilled through a limestone brick wall. The bricks have crevices. The contractor is acting stupid and obstructive or I would ask them. How would one mount a short (24 cm lond, D= 300mm) piece of round air duct into the core hole? Simply put in? Sikaflex all around? How about risk of moisture creeping in?

My first idea is to let the duct sick out 1 cm on both sides, and to grout the wedge with sikaflex. Criticisms? Better ideas?


texts:
Is it possible to define any camera without "flash" (sensible to any band of radio wave) as a passive radar?

If so, where could I find references to that? I've been looking all over the place and nothing has come up.

If anyone has any sources or comments, please let me know.
Thanks!

Edit: The idea of camera is merely a device that captures light in any range (visible light, infrared, ultraviolet).
This is close in meaning to a passive radar, which is sensible to the electromagnetic waves coming from a target.


texts: Unable to install Actuators to a LABVIEW based Engineering Test System

texts:
I need to install an actuators to LABVIEW base test system because the old actuators are defective. We cannot purchase the old actuators because they are obsolete. The old actuators communicated using the COM ports 1 and 8. The COM port are hard coded in the LABVIEW program. The new actuators communicate via a USB interface. But COM ports 1 & 8 not available. The systems states that they are "in use".

The LABVIEW based test systems is running on a Window 7 machine. Is there a way to point the new actuator USB interfaces to COM port 1 and 8?


texts: How to measure the pressure inside a bottle rocket?

texts: I'm making a pressurized bottle rocket out of a plastic bottle, vinegar, baking soda and a cork.  When the vinegar & baking soda react in the closed bottle, the pressure builds up but i want to measure how high this pressure is.  Ideally, i'd like to use a small, light weight gauge so that it does not affect the rocket's launch dynamics significantly.   I hope that i can also mount the instrument to the inside of the bottle so that i can measure the pressure entirely from within the bottle. Is there a small, lightweight instrument i can use to measure the pressure build-up from inside the bottle?


texts: How to obtain sensor failure probabilities?

texts:
I'm a computer science student doing research in wireless sensor networks (WSN) optimization. Based on past research works, sensors are capable of failing due to a number of factors such as harsh environmental conditions, communication errors, and malicious attacks. According to this source, it is possible to assign a failure probability to each sensor. The source states that initially, it can be set by the manufacturer; however, many factors such as weather, accidents, interferences can affect the sensor failure probability.

Given that the network topology is known (the location and therefore environment is known) and that I have access to some hazard maps, how do I assign failure probabilities to each sensor? For example, if sensors in flood-prone areas are more likely to fail, how do I set the exact values of the failure probabilities? Is it acceptable to just assign arbitrarily higher values to sensors in harsher environments? Is there a way quantify this from an engineering perspective?

Thanks and any insight would be extremely helpful.


texts: Finding the displacement in a truss using energy method Question

texts:
I've been trying to revise for an upcoming final so I am solving problems from the previous chapters.I've been wracking my head on this for a while (about 1-2hrs) but I just can't seem to get it.
For some stupid reason I can't figure out why Member CE is 0 in the virtual loading, shouldn't that pin at C have a vertical reaction of 1. That would mean the summation of the vertical forces at joint C would be something like this Fy=1-FCEsin(26.565)=0. Failing at method of joints is very depressing to think about with the upcoming finals :/. Of course, the solution manual is no help it already assumes any scrub can solve method of joints. Can you help me out :|


texts: How to create RBE2 between the end edges of a cylinder and end nodes of a beam element in ANSYS APDL?

texts: I have a cylinder with shell mesh. on its axis I have a beam with the same length of the cylinder. I want to create an RBE2 between each end edge nodes of the cylinder and the corresponding end node of the beam. how is this possible using APDL ?


texts:
I have seen in many data sheets of Hydraulic Gear motor a spec called : "Minimum Speed = 450 RPM" ( 450 is an example)
here is a capture from the linked datasheet below :

In your experience or theoretical knowledge what happens If I run the motor slightly below this speed (say 150 RPM ) by reducing the flow of Oil.

Does it lose torque/or any other spec but stay running normally ?

Does it stop moving smoothly? ( I have seen this "discontinuity effect" in real life when flow is too low the motor speed was around 10RPM)

note: what I mean by discontinuity is that the motor moves a push then stops as if it is gathering oil then move a push again.
Datasheet


texts:
Elevators were invented several centuries ago. How is it possible that in the 21st century, there are still a number of cases of people getting stuck in elevators? I have gotten stuck in an elevator myself before, and have anxiety about entering an elevator ever since.

So I would like to know, what causes elevators to get stuck to the point that it requires outside intervention?

Why can't (or shouldn't) it automatically recalibrate itself?

Is it more of a mechanical issues or electrical issue?

Does an elevator getting stuck indicate a serious issue with the elevator that require maintenance, or is it something that can happen to even newly installed elevators?

Will we ever be able to fully prevent elevators from getting stuck?

Additional Questions:

Occasionally, I may hear a loud bang when riding on an elevator. Although luckily the elevator does not get stuck. Why does that happen?
In some elevators, a person stepping into the elevator will occasionally cause it to wobble up and down, as if it is trying to realign itself with the floor. This tends to happen more often if the person is heavy in their footsteps. Is there a reason to worry in this situation?
Some times, an elevator will start beeping even though it did not exceed capacity. After the door closes, the beeping stops and it proceeds as normal. Why does this happen?
In what case (if any) would getting stuck in an elevator be life threatening? (Assuming the person remains perfectly calm and will only attempt to leave the elevator under the guidance of trained personnel)


texts: I have been looking a lot into shape memory polymers and alloys recently and have been wondering wether they have an application in headphones. By this I mean that when plugged into the phone the warming current is sufficient to ‘untangle’ them back to their original, straight shape, avoiding the time consuming process of manually untangling the knot. Would this be possible, or is the current provided by the headphone jack insufficient. Any ideas would be appreciated.


texts: Two intersecting prisms (typed and with diagrams)

texts:
Case 1
The development of Case 1 of this problem in which the axes of the prisms intersect at right angles, is shown in Diagram 1. Note that interedge lines are required for the development of both solids, their positions being found by projectors drawn from the different views of the drawing to the full view of the end.

Case 2
Case 2 of the problem in which the axes intersect at 45°, is developed in a similar manner. The projections for this are shown on the plate at Fig 1(a). In order to avoid confusion of lines, projectors are sometimesdrawn as shown on this plate, that is, only rheir starting points are indicated, as between the two views of the octagonal prism in this drawing. First, reproduce the projections. Next, develop the strechouts for the solids on the lines MN and M'N', and draw edge and interedge lines through their respective points. The positions of the interedge lines are found by projecting the point A in the plan across to the full view, as shown in (d) afterwards locating the points x and y at x' and y' in (d'); then they are projected to the elevation and carried to the development in the usual manner, the resulting figures at (b) and (c) completing the development of the solids.

What I need to know is, should both drawings be drawn in an elevation and plan way? And where exactly is the problem in both cases that should be developed?


texts: How can I setup a controller simulator in excel?

texts:
Is there a good excel program somewhere or basic breakdown of how to implement a control loop in excel if trying to simulate the performance of a circuit?  I have data from an operating plant and am trying to simulate the control loop but I'm not getting the correct outputs for the loop inputs.

Update:   I think what i'm missing is basic. I have cv, mv, and sp and I'm trying to simulate the controller. I have the PID settings for the controller as well (I think it was Siemens). Gain is 0.8, Integral time is 15 seconds and i have data on a 2 second sample time (I realize this is low resolution). The issue i'm having is i'm looking at output between t1 and t2 and trying to pull the appropriate data to estimate the PID output but i am consistently getting a different delta and i think I'm just setting it up wrong mathematically.


texts:
I'm a Junior computer engineer working on a project involving a 3d printer. It is a mobile printer with the print head attached to wheels which move along the x,y axis of the surface it is printing on. The wheel movements may be off by less than a millimeter as the printer is moving. This causes a serious problem after printing a few layers as each layer does not land on top of the other.

I am in the process of implementing a sensor to detect the location of the print head with respect to some arbitrary reference point. My task is to implement a feedback control loop to correct the printer's movements and have the object printed properly.

I have an idea of how I want to solve this; using the sensor to detect the current location, then read the code to check what is the desired location, I then implement code to move the difference.

My question is where does the concept of PID control even fit in? The following equations were taken from wikipedia for time/frequency domains.

I am confused about the values of t and s in the above equations. I have numeric values for input, output, error and the K constants. None of the values are functions so I don't understand what happens with the derivative and integration involved. Sorry if this seems like a dumb question but I am a complete novice to control theory and have been learning from online articles.


texts: With the "plain old telephone system", would two neighbors be able to call each other privately?

texts:
Suppose that Joe and Sue are neighbors out on the country. The year is 1950. But it could also be 1975. Or even 1999. Even though they live next to each other, and can see each other through the windows, there is still a non-trivial distance between them, especially in winter time with lots of snow and coldness. They don't fancy constantly putting on clothes and walking over to knock on the other's door to ask something.

So, they have a habit of calling each other on the telephone for convenience when they need to ask something and don't feel like going outside for whatever reason. They did consider using two tincans with a string between the houses, but they thought it looked too childish, and they couldn't figure out a good way to signal for the other person to pick up their tincan. So they use the normal telephone.

Regardless of the year, they are using the "POTS" (Plain Old Telephone System).

When Joe calls Sue or Sue calls Joe, being neighbors, would the signal first travel down to some telephone company far away, and then back to the other person? Or would they get a direct connection going straight through the telephone wire right to the other house and into their telephone?

I've tried to understand how telephones work all my life, but never quite managed, so I really don't know if this is a stupid question.

It sounds reasonable to me that, given the extremely short distance between the two parties, the signal will travel instantly between them, not triggering any kind of "log" at the telephone company's equipment (thus being free of charge) and also won't allow anyone to tap into this call remotely, unless they are right there between their houses with a physical thing hooked onto the telephone poles' wire.

Is this a correct assumption by me? Would it be free and private due to the extreme proximity? And if so, when would it stop being free and private? How many houses or what distance triggers a different "route" and the ability for remote wiretapping?

Again, please note that I'm not talking about whatever digital system is in place now, but what used to be the case with the old telephone system.


texts: Pressure beneath the Ocean with Neglect to Compressibility

texts:
For a National Board Exam Review:

  What is the pressure 7000ft below the water surface of the ocean?
  Neglect compressibility.

Answer is 512000psf

$${ P_2 = P_1 + \gamma h }$$
$${ 14.7 \frac{lb_f}{in^2} * (\frac{ 12in }{ 1 ft})^2 = P_1 + (62.4 \frac{lb_f}{ft^3}) 7000ft }$$

I get: 434683.2 psf

Am I using right formula? Is there better approach?


texts:
I am establishing a MatLab FEA code for determining the stiffness of a structure. Diagram of the structure is added below.
I have established a code for determining the stiffness of the structure, but I am unsure of how to treat node B. Element AC is one continuous beam with element BD connected to it through a pin connection. That is, element BD will only experience axial forces (= no angular displace), while element AC at node B will experience axial forces AND bending moment, causing angular displacement.
So how do I treat this node? I can not say angular displacement is 0, because it is not for element AC. But if I say it is different from zero, the connection will act as if it was welded together.
Please let me know if you need more information.
Regards


texts: Ceramic pressure measurement - piezoelectrical or capacitive?

texts:
Context: I'm writing about an old industrial training facility used for a petrochemical process.
In this training facility, there is a 3-phase separator. On that separator is a pressure measurement. My teacher, having limited knowledge of the facility in question, told me that the sensor was "ceramic".
I searched for ceramic pressure measurement sensors and found two principles. At least, I think they are two different principles, however I suspect they may be the same principle but explained differently.
My current (mis)understanding:

The capacitive principle: A ceramic membrane is exposed to the process pressure. This process pressure will cause it to bend, which will increase its capacitance (probably due to an increase of proximity to an electrical contact?). The higher the pressure, the thicker the membrane needs to be, lest it break. Due to the increasing thickness requirements, this measurement principle only gets less and less accurate as the pressures get higher.
The piezoelectrical principle: A ceramic membrane is exposed to the process pressure. This pressure causes it generate a small but measurable voltage, due to its molecular structure. The voltage's magnitude is translated into a measure of the pressure's magnitude.

Now, I suspect that these two principles may actually be talking about the same principle, though perhaps focusing on different aspects of the principle. The reason for my suspicion is that I don't know a lot about electricity, and it seems unlikely to me that people would be using ceramic materials for pressure measurement for a while without noticing that the material had a piezoelectrical property that could make it usable for presumably better pressure measurement.
Now, my teacher said that it is most likely the capacitive principle being used in the facility in question, but he said the piezoelectrical principle is most common nowadays (the facility is quite old). So, it seems like my teacher thinks the two principles are distinct, but I'm a bit unsure.


texts: Determining required pressure drop for choked flow conditions to be met

texts:
I have pipework system with an inlet pressure, $P_0$, which passes from a pipeline of fixed diameter, $D_0$, through a tee with reducer to a smaller diameter pipe, $D_1$, before returning to another pipeline (same diameter, $D_0$) of lower but unknown pressure, $P_1$, through another tee and reducer arrangement.

I am attempting to determine the pressure drop required for natural gas flowing through the system to meet choked flow conditions (Mach 1).

I have used the following equation to calculate a critical pressure ratio:

$$\dfrac{p^*}{p_0} = \left(\dfrac{2}{n+1}\right)^{n/(n-1)}$$

Which works out as 0.542 assuming ideal gas condition using $n = 1.32$, natural gas ratio of specific heats ($k$). Therefore a local pressure drop of approximately $P_0/2$ would be required to meet choked flow conditions.

However, I am concerned that this is overly simplifying the problem.


texts: A sphere of radius R, made from material of specific gravity, SG is submerged in a tank of water

texts:
... The sphere is placed over a hole, of radius a, in the tank bottom. Develop a general expression for the range of specific gravities for which the sphere will float to the surface.

I've attached the diagram for the problem.

As an attempt at the solution, I've summed the forces on the sphere, or the buoyant force $F_b$ - the weight of the sphere. Buoyant force is equal to the weight of the displaced water by the sphere, $\frac{4}{3}\pi R^3\rho_{water}\times32\frac{ft}{s^2}$. The weight of the sphere is $\frac{4}{3}\pi R^3\rho_{sphere}\times32\frac{ft}{s^2}$. Based on force equation, in order for the ball to float the buoyant force would have to be greater than the weight of the sphere, or $F_b-W>0$. After some algebra you can say that the specific gravity of the sphere has to be $<1$, which seems too simple to be the actual answer.

I'm sure I'd have to take the hole that the sphere is resting atop into consideration, but I'm not sure how to go about that. My only ideas on how to include that would be to include the force from the ambient pressure on the bottom of the ball pushing upward in the force equation, but even if that effects the specific gravity at which the ball will float, once it started to float and that force was no longer there, the ball would simply sink again, unless $S.G.<1$. My other thought was that I would have to consider the volume of the sphere not submerged due to the hole and thus not contributing to the buoyant force, but I have no idea how to calculate what that volume would be.

Is my first solution correct, that $S.G.<1$ would cause the ball to float? That again feels too simple for the given parameters.

Any direction would be appreciated.


texts: Fusion360 - How do I fill these sketch planes into a body?

texts:
How do I make this highlighted part of drawing a solid body so that I can than boolean / subtract it later?

All of these faces / planes are connected.


texts: Verify assigning of material to all parts in a assembly

texts: is there any provision in SolidWorks to check if all parts in an assembly is assigned material, rather than individually checking each part under the design tree? It becomes tedious to check individually when there are too many parts


texts: Difference in Diameter calculation using Solidworks and manually

texts:
When I try to create a flat form of a archimedes screw using Solidworks it gives me a diameter different from what is calculated manually basically using a Pythagoras Theorem. Can anyone explain the reason as to what is used by any 3D Software in order to calculate the diameter and essentially what factors am I assuming when I calculate using the pythagoras theorem only.

I tried to calculate a screw with pitch- 400mm, OD - 400mm and Id - 268mm
Using Pythagoras theorem gives me a OD - 430mm and ID - 297mm circle
whereas Solidworks gives a OD - 450mm and ID - 318mm circle.


texts: Discrete Control System Process Sampling Rate

texts:
In digital or discrete control, instead of continuous analog-type variables, a controller samples a process variable signal at regular discrete time intervals. So, effectively, the process variable does not change as far as the system is concerned between those samples, or if it does, the change won’t be detected until the next sample. And it will be abrupt if it changes at all.

One would think that the faster the sampling rate (the more samples in the same time interval, or shorter times between samples), the more closely the discrete control would emulate ideal continuous control. Apparently that is not the case. In fact, as I understand it, increasing the sampling rate past some critical point can actually make a discrete time or digital control system unstable, as it can push the transfer function poles out close to and even outside the unit circle of stability.

This seems to be counter intuitive, at least to me. Is there a simple explanation for this that I’m missing here?


texts: How to enforce 0 yaw in (6DOF) system described by Euler angles

texts:
I am attempting to reduce the equations:
$\ddot{\alpha} = T^{-1}(\dot{w} - \dot{T}\dot{\psi})$
$I_{xx}\dot{\omega}_x = (I_{yy}-I_{zz})\omega_y\omega_z +M_x$
$I_{yy}\dot{\omega}_y = (I_{xx}-I_{zz})\omega_x\omega_z +M_y$
$I_{zz}\dot{\omega}_z = (I_{xx}-I_{yy})\omega_x\omega_y +M_z$
To a system where the body rate about z is 0 and the euler yaw is 0, however so far I have been unable to. Euler angles roll pitch and yaw: $\psi, \theta, \phi$. -- $\alpha = \begin{bmatrix}\psi & \theta & \phi\end{bmatrix}^T$. $M_x, M_y, M_z \in \mathcal{R}$
$T  = \begin{bmatrix}1 & 0 & -sin(\theta)\\
0 & cos(\psi) & sin(\psi)cos(\theta)\\
0 & -sin(\psi) & cos(\psi)cos(\theta)\end{bmatrix}$
This was obtain a 4DOF model of a quad-copter from which I could develop a Lyapunov controller.
My methodology was set $\omega_z, \dot{\omega}_z = 0$ Then construct $\ddot{\alpha}$ using the 4 equations. However, when I do so, I still end up with
$\ddot{\phi} = (\dot{\psi}\dot{\theta} + \dot{\omega}_ysin(\psi))sec(\theta)$.
$M_z = (I_{yy} - I_{xx})\omega_x\omega_y$
If I were to set $M_y$ such that $\ddot{\phi} = 0$, the other dynamics would be fixed too.
Is it possible to enforce both the euler yaw and the yaw body rate to both be 0, without also affecting the other dynamics? Have I made a mistake or is it simply impossible.


texts: Aluminium brazing instructions: heat thoroughly to "open the pores" before tinning with rod

texts:
I have instructions for using aluminium brazing rod "HTS-2000".

It says:

  Clean the area to be worked with a wire brush. Heat the work surface until it is hot enough to melt the rod. Open the pores of the work surface so the rod can penetrate the surface.

I have never heard of metal having "pores".

What exactly is this opening of pores? And is there some minimum/maximum temperature/duration for this heating? (Obviously lower temperature than melting point of the base metal, and higher than the filler rod)


texts:
I want to ask about the torque experienced by a axial flow turbine, in relation to the pitch angle or angle of attack.
If you can suggest an equation, will greatly help.

(I'm new to technical terms, please bear with me)


texts: Use of Cast Acrylic sheets as glazing in a Flat Plate Collector for domestic water heating

texts:
I am designing a FPC for heating water. I was wondering about the feasibility of replacing the usual Low-iron tempered glass with Cast Acrylic sheets [owing to non-availability of the former where Im from].
I am concerned however, about its structural integrity under thermal loads. Will its optical performance remain satisfactory at the higher temperatures expected during service, or would it deform, or even melt.
If it would melt, I was considering adding 5mm ordinary glass glazing above the Absorber plate, and then add the acrylic after an air gap for protection, and added insulation. However this arrangement would lead to added costs and reduced transmittivity [and thus efficiency].
I'd appreciate any input regarding the problem, and suggestions regarding the design.


texts: Reading a value off a screen with a camera

texts:
I'm looking to log some information on a piece of equipment I have running at home. It displays the information I want - operating rpm and some other settings - on seven-segment displays. In an ideal world, I'd like to log the value of this setting continuously, or at intervals.

The obvious thing to do would be to open it up and interface with the onboard electronics somehow, but I don't have much experience with this and am worried about breaking something.

A non-invasive solution a friend suggested was to use a camera to read the value off the screen. They figured if a camera were to be placed adjacent to the display and either recorded video or took pictures of the display periodically, these video/images could be automatically analysed for the values of the seven-segment displays and the results logged.

I have some experience with image analysis and reckon analysing brightness of certain pixels corresponding to active sections of the display relative to its background could be used to find the value from the display, as long as the camera/display were in a fixed position.

This idea sounds pretty good to me but based on some google research I can't find much information on similar schemes. Has anyone tried something similar, and have any pointers? Would something like this be possible? Is there a better way of implementing it?


texts: Where to put the booster pump at customer substation in a district heating system?

texts:
In a district heating system, one of the houses in the distribution net is not getting the desired heat into their house. This is because the pipes of this customer which connects them to the distribution system, are smaller than required; which leads to sudden pressure drop.

The solutions I can see are either to replace this customer`s supply pipe with the bigger one, or setting up a booster pump system at the customer. If I were to decide on putting a pump system, where should I put the pump; on the customer supply pipe or return pipe?


texts: Searching for a High Speed Actuator for a simulator

texts:
I am currently planing to build a consrtuction for a simulator.
My simulator seat should be able to fall like 30cm and afterwards move to the starting position .

The falling should be as natural as possible. For that my actuator has to be really fast.
I am searching for a good soultion to lift up the seat with a person like up to 100kg.

I was thinking about a linear actuator or a linear motor.

About the linear monitor I know it is really fast and would probably provide a fast motion.
I wasn't sure, whether it can hold a heavy person at one position.

Any ideas, suggestion and solution or links to good linear motor or linear actuator would be really hepful.
Thanks in advance :-)


texts: Why do train cars have unevenly spaced axles?

texts:
Every train car I can remember has its axles arranged like the photo. Two are put very close together in one chassey, and two more the same way at the other end.

But why do that? If you want 4 axles, isn't it better to spread them out evenly like I drew? Or if you just want axles at the ends, why not just have 2 total instead of 4 unevenly spaced ones?

So why are there unevenly spaced axles? If you want only 2 pivot points, why not just have 2 axles total (which would be spread evenly if they are equal distances from the ends of the car)? If you want 4 axles (presumably for load bearing), why not spread the axles evenly?

I could not find this answer via googling. It might help if I knew the exact terminology of that chassey holding two axles.


texts:
I solved this problem by doing a mass balance for the mixing chamber and an energy balance for the water heater and the mixing chamber as follows:

$\dot{m}_{\text{mix}}=\dot{m}_{\text{Tank}}+\dot{m}_{\text{Cold}}\\
\\
\dot{m}_{\text{mix}}\hat{H}_{\text{mix}}=\dot{m}_{\text{Tank}}\hat{H}_{\text{tank}}+\dot{m}_{\text{Cold}}\hat{H}_{\text{cold}}\\
\\
\frac{m_{\text{water in tank}}C_{\text{v}}\left ( T_2-T_1 \right )}{\Delta t}=\dot{W}_{\text{e}}+\dot{m}_{\text{Cold}}\hat{H}_{\text{cold}}-\dot{m}_{\text{Tank}}\hat{H}_{\text{tank}}$

resulting in:

$\dot{m}_{\text{Tank}}=0.05838 \text{ kg/s}\\
{T}_{\text{shower}}=44.67 \text{ °C}$

and my results are in agreement with the solutions manual. But, if I do a mass balance in the water heater I obtain

$\dot{m}_{\text{water heater}}=\dot{m}_{\text{Cold}}-\dot{m}_{\text{TanK}}$

and if I replace the value that I have obtained previously, I do not obtain a zero mass flow for the tank. So, ¿Is my answer or mass balance wrong, or I misunderstand something in the problem statement?

Regards


texts: Stress strain curve stress and resilience

texts:
When calculating 0.2% offset from stress strain curve please,
do I take 0.2% of the original length and then, divide this by original length to get strain and plot this please?
And for resilience, is it integration from 0 strain to 0.2% offset strain of the yield stress with respect to strain please?
Thank you


texts: Finding final CFM with a proposed stack height increase

texts:
The EPA has come to our facility and has required us to raise 60 of our exhaust stacks to a given height.

I am wondering with initial data how i can get final CFM.

So for example. We have a stack with a current height of 41.92'. Height required is 66.58' which is an increase of 24.66'. The stack system has been designed such that there is 36' of stack height that starts at a furnace exit (which is decoupled) and goes up to rooftop height and ties inline with an exhaust fan which in turn has additional stack height inline above it. We'll be replacing the 5.92' of stack above the fan with a 30.58' stack which will get us to our goal of 66.58'. I don't want to overdraft nor under draft the furnace with the stack height modification.

If I'm not mistaken, as long as final CFM doesn't change or at least stays within a tolerance of initial CFM the additional stack height will not over-draft nor under-draft the furnace.

Again all that is changing is stack height.

Inner duct diameter is the same at 1.33FT. Temperature is 112 F. Initial SCFM is 2684 before modification. I believe the static pressure for the specific duct is .4inwc per 100ft.

Fan details: design CFM -  3570. Design Static Pressure - 2.5inwc. Fan RPM 1518 and designed max RPM is 2026.

I need help finding a formula or something to get final CFM.


texts: FEA: Changes in initial geometry cause divergence of solution

texts:
In this previous quesiton I posted, alephzero kindly noted that many of the convergence problems I was having were due to extremely high slenderness ratios that NASTRAN did not feel comfortable executing. This is all well and good, and while the accepted answer to the question indicates I may need a change in either my model or my software, I seem to have found an interesting quirk about my structure.

Consider the following two images. The following is true about both:

The left single beam has an extremely high stiffness
The right single rod has an area of $10^{-7}$ m$^2$
The bottom beams are composed of $1000$ elements
The left-most two nodes are fixed in 123456
An angular velocity of $18 \frac{\text{rad}}{\text{sec}}$ was applied

Just because I have a thousand elements does mean I necessarily fixed the slenderness problem, but I might have made a dent in it.

In the first image, the $1000$ elements are lined horizontally and the maximum deflection is on the order of a millimeter, with a curved shape that agrees with my expectation (right-most node tries to move to the right, the rod it's connected to is too stiff to extend, moves in an arc upward keeping the rod the same length, rest of the elements conform to this new curve).

However, with almost none of the parameters changed in the second image, I get deflections of about one kilometer. All that changed was the initial geometric state, where I start with a curve instead of a horizontal line.

Does this seem like normal behavior? Naively, I would expect that changing the initial geometry slightly (the right-most node moved up $30$ cm or something from the first to the second image) shouldn't cause massive fluctuations in the deflection, so is there some modeling error I'm not considering here?

The .f06 file does complain about a few of the rightward nodes having problems in the second translational direction, and this is clear looking at the deflection, but I don't know why these nodes are having problems.


texts: Emerging beam from PPLN waveguide not behaving well through optics

texts:
We have a pump laser beam that is coming out of a single mode fiber and butt coupled into a PPLN waveguide crystal. We are capturing the beam at the output of the crystal with the focusing lens in an attempt to collimate it into a beam. The emerging beam does not appear to be Gaussian however and also does not seem to be behaving well through the optics.  Namely, it will not collimate. More specifically, we see the following “window blind” diffraction pattern far from the crystal, image attached to this question.  Can anyone shed any light into

why the emerging beam is not Gaussian
why the beam cannot be collimated?  Our beam diameter coming out of the single-mode fiber (25 um) is larger than the waveguide itself (5 um), perhaps this is a factor?


texts: Mirror an entire part in solidworks to create a new part

texts:
I have a pretty complicated part in solidworks that I need to 3D print. The part is designed to be a support, holding up a gauge on the side of a small pump.
On the other side of the pump, I would like to have the same part but in the opposite orientation to hold up another gauge. Rather than going through the tedious process of building the mirrored part from scratch, it would be easier to mirror the entire part about the relevant face. Is this possible in solidworks?


texts: How to prevent vibration loosening whilst maintaining adjustability?

texts:
I have some height-adjustment nuts screwed onto vertical threads to support my print-bed for a 3D printer. They are domed nuts and the aluminium build-plate sits on top of the domes, three holes in the plate align with the domes to hold the plate in place.

How can I protect these nuts from vibration loosening without using thread-locker or similar, so that they remain adjustable?