texts: Controls Project: Help needed finding 3rd order system

texts:
I'm in need of help finding a third-order or higher system in which I can derive a transfer function. We have a class project in which we need to find a real-life example of the system that equates to a 3rd order system or higher.

The problem that I have is that I do not know what a third-order system looks like in real life. I can find a lot of examples of 2nd order systems (acceleration, velocity, and displacement). But no 3rd order! Help!

Project guidelines:

Step 1: Find a system of interest to you, discuss why this system is of specific interest to you and why this is a good topic for the class project;

Step 2: Model the system in three forms: differential equations, transfer function, and state-space representation. Note if the system is nonlinear, please linearize it first;

Step 3: Find and plot system output under step input and another input of your choice. Discuss the physical implications;

Step 4: Study the system stability, discuss the physical meaning of instability in your case;

Step 5: Assume a negative unity feedback system,  two possible controllers:

$\ C_1(s)=k_0 $

$\ C_2s= k_p + k_ds+k_i \frac 1s $

• Design the two controllers, so that the system is stable.

• With all your designed control parameter values, what are the feedback system’s output under step input and another input of your choice?

• What are the steady-state errors under the four cases (2 controllers, 2 inputs)?


texts: Pouring aluminum into another block of Aluminum

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I have a 120mmx120mm brushless fan with an Aluminum frame, which as you can imagine, isn't very thick. I want to thread the base, so I can mount it with a fairly large screw. For that I need to add more Aluminum so the screw has more to  grip on.

I'm thinking of creating a casting mold around the exterior side of the Aluminum frame (proof sealed) and then pouring molten Aluminum in it. I've seen videos of people pouring Aluminum and it seems to have a relatively low Heat Capacity compared to other metals (i.e. it will cool down and solidify before it melts the surface of Aluminum frame), as I've seen Anthill Art being made without so much as scorching the earth. Also, as Aluminum is a good Thermal Conductor, the heat would dissipate throughout the frame pretty quickly.

How would I alleviate the two problems of low Heat Capacity and being a good Thermal Conductor? I know that one always have to pour excess molten metal to the block being added to, but do you guys have better ideas??


texts:
I'm trying to design a small metal telescopic track (6cm x 2cm when extended) where small objects may be arbitrarily positioned inside:

In the above example, the green block jams the tracks as the bottom cannot move upward. Does anyone know of a better design such that the tracks won't be jammed? I've thought about putting a sleeve on the inside, but if it was 6cm long and covers the entire extended length, it'd overhang when retracted.

Any help will be appreciated.


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I'm trying to create an excel sheet that will use the modified sine equation above to output a 360° displacement chart when a user types in the acceleration, velocity, total distance traveled and start and stop angles. From what I've been told previously this is the equation I have to use, but my background is more on the excel side of things so I'm having trouble understanding exactly how to break this equation down into something I can use.

Could someone please explain how to solve this equation using the variables that will be available that I described above? Does this equation require any more or any less variables than what will be available?


texts: Can two-pole brushed DC motors have a ring magnet stator?

texts: Is it possible to build a brushed DC motor with a ring magnet stator, instead of a stator with gaps as shown in the GIF below?


texts: Diagrams of forces and moments of a statically determinate structure

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I'm having difficulties with calculating the distribution of forces and moments in a statically determinate structure shown below.

I'm especially confused about the arc part. Will there be only bending moments, or should we expect torque as well? Any help with approaching this problem is appreciated!


texts: Planetary gear efficiency for a variable load

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I use the Maxon planetary gear #203115 for a project. Here are its characteristics (from the datasheet):

$n=12:1$
3 stages
$C_\max=7.5 \mathrm{Nm}$
$\eta_\max=\eta(C_\max)=0.81$

Maxon precises that the efficiency depends on the torque applied but is independent but is unaffected by the motor speed. They give a schematic curve:

If I assume that the losses come only from dry friction, I find:
$$\eta(C)=\frac{C-C_{frict}}{C}$$
$$\eta_\max=\frac{C_\max-C_{frict}}{C_\max} \Rightarrow C_{frict}=C_\max(1-\eta_\max)=1,425 \mathrm{Nm}$$

Unfortunately these equations give an unrealistically low efficiency for low applied torque:

How can I model the efficiency more precisely ?


texts: Is tunnel lining the same thing as tunnel structural support? And then also there is always the initial and final lining? Are three all different things? And how do they relate to waterproofing? It seems that there are endless methods which are a combination of many materials and applications and soil and water conditions. I need some general thoughts to direct me in the right direction.


texts:
Suppose, I am trying to install a completely new manufacturing plant, so I have no previous data to help me.
I want to calculate a rough estimate of my annual maintenance cost of machinery. Is there a way possible?

Note: We have purchased reused, refurbished machinery so there is no maintenance schedule book of any kind


texts: PWM to analog RC based filter with minimum analog voltage level

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Trying to design a circuit to accomplish the following:

5V PWM signal is converted to 0-2.5V analog voltage
The analog voltage should never drop below a certain minimum voltage level, when PWM is 0 or filtered PWM signal results in a voltage level less than this minimum.

I know I can do this with a microcontroller and other IC's but looking for a simple solution. I've come up with the following. A voltage regulator produces 2.5V. An n-channel FET switched by the PWM signal produces a 2.5V PWM signal. This 2.5V PWM signal is converted via RC filter to 0 - 2.5V analog voltage.
I also have a voltage divider to feed the minimum voltage level to the capacitor through a diode. I am aware I will need to compensate for the voltage drop over the diode.

I want to keep the 2.5V voltage regulator to guarantee a 2.5V voltage level, since the 5V PWM signal may be 3.3V PWM.


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I'm trying to solve this problem in elementary Carnot cycle study:

I have two (hot and cold) heat fountains of a motor, in air, at temperatures $T_a = 1500^0$C and $T_c = 10^0$C, respectively. The work done by this motor is employed to activate a heat pump, the cold fountain of the heat pump is at $T_c = 10^0$C and the hot fountain is at $T_b = 40^0$C. Both are suppose reversible machines.

  The fraction between the heat that the motor receives of the fountain and the heat that the heat pump provides to its hot fountain is?

My attempt: We have that both, the motor and the heat pump, can be modeled by a Carnot Cicle model. The question asks: What is $Q_a^M/Q_c^T$? So we have that the work done by the fountains is

$$\tau^M = Q_a^M-Q_c^M$$

But this is the work that it is used to activate the heat pump, so we have that $$\tau^M = Q_b^T$$
Then we can manipulate this results to obtain, using that $Q_b^T/T_b = Q^T_c/T_c$

$$Q_c^T\frac{T_b}{T_c} = Q_a^M-Q_c^M = Q_a^M - Q_a^M\frac{T_c}{T_a} = Q_a^M\left(1 - \frac{T_c}{T_a}\right)$$

Then we have that

$$Q_a^M/Q_c^T = \frac{T_b}{T_c}\left(\frac{1}{1 - T_c/T_a}\right)$$

But this gives the wrong answer. The correct one is $Q_a^M/Q_c^T \approx 0,1137 =  11.37$%

Notations: $Q_{a,b,c}$ is the heat in the isotherm given by the temperatures $T_a$ or $T_b$ or $T_c$. The above indices $^M$ means that this is the heat motor and the above indices $^T$ means that it is the heat of the heat pump.


texts:
I want to engrave some letters from a 2D dxf file with single stroke fonts.

Is this easy to do in most CAM software?

I have not decided what CAM software to use yet, because the ability to do single stroke fonts is very important to me.

I have read on forums of different CAM software, that people often find this difficult. Maybe it is because single stroke fonts are not included in the software.

However I already have the font as a dxf, so all I am asking is for the machine to follow a single line, where the centre of the cutting tool follows the line.


texts: What does the sand do in a pot-in-pot refrigerator?

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The Wikipedia article Pot-in-pot refrigerator says that sand in the outer pot somehow affects the cooling efficiency of refrigerator. I don't understand what the sand does in this situation.

For example, compare filling the outer pot with water vs. filling the outer pot with both water and sand. Would these have some significant difference in cooling efficiency, meaning how fast heat is transferred between the inner pot, the middle layer and the outside air?


texts: What benefits does loopshaping have over other control design methods?

texts: I just finished my first controls course (on linear control systems) and we learned about 3 types of controllers: PID, State Space, and Frequency Response/Loopshaping. From what I understand, PID has the advantages of being really easy and it can be applied without knowing the dynamics of the system. State space provides really good responses. But loopshaping seemed very guess and check when we were doing it and kind of arbitrary. In addition, we got to actually implement the first two on a multirotor for our labs and didn't have time to do the last beyond homework. So when would it be advantageous to use loopshaping?


texts: Are solar panels placed horizontally at the equators since the solar altitude (solar window) changes direction from north to south?


texts: What are some advantages of masonry over prefab for homebuilding, or, why are prefab homes so rare in the United Kingdom?

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The United Kingdom has a housing crisis (see Financial Times, Shelter, The Independent, The Telegraph) and a housing quality crisis (killing 3000–15000 per year), due to poor insulation.
Cash-strapped local authorities aren't building.  Despite this,  new homes appear to be mostly built using traditional masonry.

I understand that prefabrication has higher quality and lower cost.  What are advantages of masonry over prefabrication?  Why would housebuilders in the UK choose the former?

New British masonry house.  Source: geograph (cc-by-sa 2.0)

Bricklayer.  Source: Wikimedia Commons (cc-by-sa 3.0)

Affordable pre-fab houses Spring Creek, Nehemiah, New York.  Source: Wikimedia Commons (cc-by-sa 3.0)

See also flatpack skyscrapers, or those apartment blocks near Reykjavík, Iceland (I don't know if the latter are prefab, but they look to me like they could be).


texts: I am trying to decide on a constant force spring to be used in a projectile launcher. The launch velocity will need to be approximately 15 m/s, which, with a barrel travel distance of 1 ft, equates to a constant force of about 20.6 Newtons (about 4.6 lbs) to reach that velocity if my calculations are correct. So my question is, where do I go from here? When I look up constant force springs, it tells me what their maximum load is, so I assume that is what the constant force will be if the spring is stretched to it's maximum length. So is it really as simple as choosing a spring with a maximum load equal to my desired launch force, or is there something more to consider? And how would I go about choosing the length and width of the constant force spring, as I'm sure it needs to be a certain distance longer than what will actually be used?


texts: Why does the yield strength of steel go up if I reduce the thickness of the specimen?

texts:
When I look at the yield of one material then you find more than one yield for different thickness.

why the yield changes with changing the thickness. is there an equation to prove this ?


texts: Why cant we provide the bars cross bent in the beam column  joint...as the cracks are all diagonal...so inorder to avoid cracks why cant we provide the bars crossed in the joint instead of providing mess of vertical and horizontal steel?


texts:
Is there a binding material that could be reinforced with woven glass fibres cloth for tensile strength, but which offers reasonable containment against high pressure when used minimally? Ie optimising for thinness.
As I see it, the challenge is how be effective in preventing the fibres of the cloth from separating enough to create a weak point which would then burst, meaning the substance needs to have reasonably high tensile strength itself.


texts: Derivation of the AASHTO formula of interior girder moment

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The interior girder moment formula for one lane loaded for the AASHTO LRFD method is:

$$\begin{align}
mg^{SI}_{moment}&=\left(1.75+\frac{S}{3.6}\right)\left(\frac{1}{L}\right)^{0.35}\left(\frac{1}{N_c}\right)^{0.45} \\
&= \left(1.75+\frac{13}{3.6}\right)\left(\frac{1}{100}\right)^{0.35}\left(\frac{1}{3}\right)^{0.45} \\
&= 0.65\ \mathrm{lane/web}
\end{align}
$$

How is this formula derived? I have not been able to find the original research paper.


texts: Motion of an object due to movement of ship

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I wanted to know how the movement of the object floating near the boat would be like. I've assumed the following scenario:

The floating object is at the location $(x, y)$. The boat starts moving from $(0, 0)$ in the y-direction with a velocity $v_s$. The water is still.

My thinking so far is as follows:

So due to the movement of the boat, there will flow of water let its velocity be $v_w$. Due to which a drag will be applied on the object which will be $C_d\rho v_w^2A/2$

After this, I'm unable to proceed further. Also, I think the object will oscillate with damping but I do not have the idea. So can I get help in how the motion of the object will be ?


texts: Would a T-800 with a gold skeleton deform under stress?

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Over in Programmers chat we were discussing whether a gold skeleton would be feasible. That got me thinking:

If I were to build a Terminator (T-800) using pure gold as the endoskeleton, would the skeleton be able to support the weight of the terminator? If so, what type of force would cause it to deform under stress? Would it be able to handle normal human tasks such as running, walking, or jumping? What about the superhuman feats of strength the terminator performs in the movies?

For the sake of this calculation, assume a T-800 weighs an extra 30% more than a human its size. Based on what Google says Arnold's size is and a rounding slightly, that assumption is 2m tall and 150kg.

The question Stacking gold Bars indicates that gold has quite a bit of strength given its reputation as a soft metal. However, that question talks about the compressive strength: also, I am not an engineer and unable to calculate the types of stresses a skeleton would undergo and whether those would be greater than the tensile strength of gold.

Finally, assume the same or similar motors and supports: there is very little information out there, but clearly this machine is capable of supporting great loads compared to humans, throwing grown men across rooms like dolls, etc. Only the skeleton is gold: motors, electronics, etc. could remain as other metals (steel, titanium, copper).


texts: How to add comments to solidworks variable file?

texts: When using an external .txt file to define global variables for SolidWorks 2021, can one add comments to this file, and what is the syntax?


texts: How to display data with three degrees of freedom on a chart?

texts: I have a collection of data obtained from calculations and I want to display it on a chart or whiz-wheel or similar, to be used "in the field" as a low-tech solution, since no computer will be available.  I have a single output variable calculated from three inputs.  What I want to avoid is making a giant book of tables or charts, and instead use something like the whiz-wheel that reloaders use for calculating propellant weight.  Are there any nifty graphical devices out there that can display three degrees of freedom on one chart?


texts:
I was reading about all types of tube drawing process and i wanted to look up some images for better understanding. When i looked at images in different sites most of them had the die ends chamfered at some angle. I tried to find out why this is done but i couldn't.

If anybody can help me that would be great ! Thanks


texts:
Cut-in, cut-out thermostats are commonly used with refrigeration devices in order to hold a consistent temperature range.

Their general operations is such that when the temperature by the probe reaches a particular temperature set as the upper limit, the thermostat cuts-in and the compressor is turned on providing cold air.
And when the temperature by the probe reaches the lower temperature set point, the thermostat cuts-out and turns off the compressor.

What materials are used in within an analog or mechanical cut-in, cut-out thermostat?  Likewise, how is the internal circuit designed such that one probe feeds both cut circuits and what control is put in place for the cut-out to override the cut-in signal?

To help scope this question: based upon the materials used in an analog cut-in, cut-out thermostat, would it be reasonable to attempt to test and adjust the set points of a thermostat by using jars of water at known temperatures and measuring the output off of the relay within the thermostat?


texts: How are point loads from studs onto a bottom plate distributed along the bottom plate?

texts: Given the reactions of studs from the loads above them, how much does the bottom plate distribute the loads over the surface the bottom plate lays on?


texts: What concerns would I need to consider for building a swimming pool of gold coins?

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If I wanted to build a gold coins swimming pool [as in DuckTales], what engineering (not security) concerns would I need to address to make such a pool feasible?  For example, since gold is much heavier than water, would I need to be concerned more about the overall weight that is supported by the base or the lateral pressures applied to the sides of the pools?

Some more details:

He had metal walls. Would steel walls be sufficient, would I need something stronger like Titanium?
Humans are, in nearly all cases, under $3$ meters tall. Even though Scrooge's depth gauge is at $90 ft$, for engineering reasons let's keep the pool to $3$ meters of depth. Note: the question originally proposed a $30m$ x $30m$ x $30m$ pool, which I am now changing to a $30m$ x $30m$ x $3m$ pool.
The density of the gold coins is near enough the density of pure gold, i.e. $19.3\frac{g}{cm^3}$
The gold coins would be as tightly packed as they would be if you expect them to get jostled around often (e.g. swimming!). They would not be in neat stacks.


texts: Stopping/reducing wobbliness in threaded rod

texts:
I am working on a 1.5-meter satellite dish with a custom receiver cantenna-like feed. The dish didn't come with feed arms, so I need a way to hold the feed into place. What I tried was using a 1-meter threaded rod. My threaded rod was 1m (length) x D=14mm (thickness). I used nuts to hold the feed in place and held the threaded rod from the little hole in the center of the dish (again, using nuts). This has the advantage of allowing me to adjust the position of the feed (focal length) so I can play around and experiment to see where my signal strength is at its peak.

Another advantage is that I don't need to use metallic arms (like many large dishes do) to keep it in place, as they can block a (small) portion of the radio waves from hitting the reflector and reduce its gain.

But there's a problem which leads me to come here and ask for help: even slightly touching the feed (or the edge of the rod) will have it wobble around for quite a while. This means that if there's a small wind, the feed will be wobbling around, which is not good.

My question is: what can I do about this? Can I use another type of rod, or make any adjustments to my current threaded rod in order to stop it from wobbling back and forth by the slightest touch? Could using a thicker threaded rod (the hole is 1 inch = 2.54 cm, but I could always drill a larger hole if needed), or would that not fix the problem?

A few pictures of the dish:

Any ideas are appreciated!


texts: Why not skip inverters and use solar power directly as dc?

texts:
To maximize efficiency and reduce cost I am contemplating using the power from solar cells directly as dc without conversion to ac.  I plan to wire and connect the solar panels in series and parallel to charge batteries and super capacitors.  And then arrange the batteries and super-capacitors to yield 115 volts dc.  This arrangement will be completely off-grid.  By skipping the inverters, I hope to gain much efficiency and lower cost.

I know direct dc wiring is used in rvs but the voltage is lower.  The 12 gauge and 14 gauge wiring in the house is already designed for 115 volts albeit rms ac.  The dc should be ok for all loads except ac motors and compressors for which I will either keep a dedicated line from the grid or use inverters just for these.

Besides possible code violations, is there any other reason to not do this?


texts: Principle behind the geometric method for constructing a regular pentagon

texts:
I want to ask about the principle or the idea that people who invented the geometric method of drawing a regular pentagon depended on. I know how to follow the steps described below to draw the pentagon but I want to know how these steps led us to a regular pentagon. They must have depended on a rule, law, idea or something so what is it?

Note: I am talking about the geometric method explained in the pictures not the divider method.


texts: I have often heard of cases where dams reduce the flow rate of rivers downstream.  This makes sense in cases where some of the water that is captured by the dam is used for irrigation and such, but in some cases, dams are built solely for hydro power and flood control, and my impression is that those dams still reduce the volume of the river downsteam.  Am I wrong in this assumption?  Otherwise, what is the mechanism by which dams that are solely used to delay rivers momentarily cause their rivers downsteam to lose water?  I could see a small increase in water loss due to evaporation that can be attributed to the increased surface area of the reservoir that the dam creates, but I would not imagine this factor to be that significant.


texts: List of materials (almost) satisfying the Cauchy relations in each symmetry class in linear elasticity

texts: There are eight symmetry classes in linear elasticity: triclinic, monoclinic, orthotropic, tetragonal, trigonal, transversely isotropic, cubic, and isotropic. I was wondering if there existed a material in each of those symmetry classes which almost satisfies the Cauchy relations: $C_{ijkl} = C_{ikjl}$ for all $i,j,k,l \in \mathbb{R}^3$ where $[C_{ijkl}]$ is the linear elasticity tensor (basically the elasticity tensor is completely symmetric). Any help would be greatly appreciated.


texts:
Why is a Non-causal PD Controller:
$C(s) = K_ds + K_p$

When a causal PD Controller is:
$C(s) = (K_ds + K_p)/(\tau s + 1)$

The difference being the denominator. $\tau$ is the time constant and is "sufficiently small and does not perturb the other poles substantially".


texts: Is there a way to calculate the heat capacity of a solid or volumetric heat capacity of a solid oxide fuel cell?

texts:
I am working on a personal project and wanted to use a solid oxide fuel cell to power up a load (I have not decided what yet), so I am trying to find a way to estimate the power I would need to heat up my fuel cell to a working temperature, so I was considering calculating the heat capacity of the fuel cell. But as it turns out the fuel cell is composed of different materials. Should it be enough to obtain the heat capacity from each material and then add each value to compute the overall energy needed?
Thanks!


texts: At what level is the Grade Beam most effective at pile cap level or at Slab-on-grade level?

texts:
The primary two functions of a Grade/Tie Beam in spread footing and/or pile caps foundation system is to support the Slab-On-Grade (S.O.G) and/or to take the moment from eccentric footing (or moment from lateral loads example wind and seismic).
While the pile cap level and depth may differ from one site and another the level of the slab-on-grade is fixed by architectural constraint.

My questions are:

What is the most suitable level for a grade/tie beam is it at the slab-on-grade level or the footing level and what will happen if the beam is at the S.O.G level and the footing is subjected to moment?
How to design such a beam, meaning what are the loads and how to calculate the lateral loads (especially shear and moment) from loads such as seismic and wind?
In what Section of the ACI and Eurocode is the Tie/Grade Beam is mentioned and is it always required (meaning for all soil types and seismic zones ...)?


texts: In the rolling process, Why should the velocity of the strip at the entry before coming in contact with roller be lesser than the velocity of the roller?


texts: What types of materials can be tested in a split Hopkinson pressure bar?

texts: A split Hopkinson pressure bar can test different types of specimens, I would like to know what types of materials that are suitable to be tested with this method?


texts: How to calculate time taken for an electric shower to reach set temperature

texts:
Can anyone give me a few pointers to calculating the time take for an electric shower to reach it's set temperature?

The set temperature is actually a power setting and a flow rate setting.

I know that with 3500 watts of heating power and a flow rate of 3.5 litres per min, I will get a 14.35 degree rise.

3.5 l/min = 58.3 g/sec
58.3 * specific heat of water 4.18 = 243.8
3500w / 243.8 = 14.35 degrees rise

So my question is, is it possible to work out the time taken to reach this temp? I assume I need to know something about the efficiency of the heat exchanger to calculate this as well as the specific heat of the materials between the heater and my measurement point?


texts: Design of a lead compensator with root locus in matlab

texts:
For the transfer function $G(s)$, I tried to design a lead compensator for the function to have a response to the step with the following specifications:

$$\%OS = 10\% \ \rightarrow \ Overshoot $$
$$ T_s = 5sec \ \rightarrow \ 2\% \ Criterion$$

When I simulate the function already with the lead compensator by the rlocus() command the system shows the desired behavior. However when I simulate with the step() function the parameters do not match.


texts: performances of a continuous flow reactor

texts:
How can we know the evolution of the oulet concentration of a perfectly well-mixed continuous flow reactor taking into account the residence time distribution function called $E(t)$? I have heard about this model

$$C_{RP} = \int_0^\infty C_{RF}(t)E(t)\text{d}t$$

where

$$\begin{align}
E(t) &= \dfrac{1}{t}\exp\left(-\dfrac{t}{\tau}\right) \\
\tau &= \dfrac{V}{q}
\end{align}$$

This equation only gives the outlet concentration at the steady-state  called $C_{SS,RP}$ (so one value). I am looking for the evolution as a function of time $C_{RP}(t)$ for the concentration in a perfectly well-mixed batch reactor.


texts: What to do first when going from Prototype to Finished Product?

texts:
When you have a working prototype based on off the shelf parts (eg. Arduino), and you want to move to designing a finished product, what is the correct order of development?

Electrical Engineering? (PCB design, program, etc)
Design?
Mechanical Engineering?
Others?

Thank you.


texts:
I have a sculpture that is designed to rotate over 3 axes at max. 30RPM and is mounted on an aluminium disc. My plan is to use 3 of these geared steppers and secure the sculpture to the Z-axis shaft, but it's not quite clear to me how to (economically) secure the motors and the load to provide 3-axis movement. I see that the maximum radial and axial loads are around 150N, and because the load is around 8kg, I could perhaps save myself from using additional bearings and just rely on the bearings in the gearboxes. Is it correct that if the load is accelerated and decelerated slowly (<1.88m/s^2), the 150N force limits won't likely be exceeded?
My current plan is to mount the Y-axis motor to the shaft of the X-axis motor using a shaft flange like this:

Similar for the Z-axis motor. However, the force figures of these flanges are usually not provided. Also there doesn't seem to be a good way to limit axial movements of the flange. I've thought about using circlips, but I'm not sure if they have sufficient strength to resist a 8kg load.
Does anyone know of a good way (or a good reference) for providing 3-axis movement to a 8kg load? Is it reasonable to expect the bearings in the gearboxes to adequately support the load, given the 150N axial and radial force ratings?
Any advice appreciated.


texts: How can energy be added at constant temprature?

texts:
In the answer to this question:

Difference between Saturated Liquid and Saturated Steam

How can energy be added with constant temperature? Isn't the energy input itself a change of temperature?

Sorry for the repeat, but I don't have enough reputation to post a comment.


texts: What are these banded earthworks near a freeway overpass for and what are they called?

texts:
The satellite view of this overpass (on Google Maps) shows some banded earthworks.

When driving by, you can see that each band is an elongated triangular shape (street view):

My guess is that these earthworks act as a wind break by making the wind turbulent, so as to minimise the force of cross winds on the overpass.

Is that what they're for? What are they called?


texts: Does the resistance of a curved rod to compression depend on the number of curves?

texts:
In The Physiology of the Joints by Kapandji, he provides a diagram on page 21

He does not formally define the concept of "resistance" but just creates this variable $R$ and claims that, if $n$ is the number of curves,

$$R = n^2 +1$$

He also references an equation called "Delmas Index"

$$DI = \frac{\text{length of vertebral column from tip to tip with curves}}{\text{length of vertebral column from tip to tip fully extended}} \times 100$$

Unfortunately, he provides no citation for any of this. Upon Googling both of these a fair amount, I have sadly found other physiology textbooks reference only this book. There doesn't seem to be any actual scientific analysis given.

There are no references given anywhere in the book.

My question is,

Does an actual quadratic relationship exist between the curves and the resistance of the rod to compression? If so, what is the real equation used in fields like continuum mechanics?


texts:
I have a few values in Newton metres and I need to make sure each value is an SI unit for calculations. However when I try to search for the units I am given, I can only find similar, but not quite the same, units.
Can someone help clear up the confusion?

I'm given the unit Nm$^{-1}$, the unit of a spring constant. As far as I can tell this is already an SI unit but I'm confused as I can only find the unit Nm online. Are Nm and Nm$^{-1}$ the same? I would say that Nm is a newton metre whereas Nm$^{-1}$ is newtons per metre, which is why I'm confused about this
Similarly, I'm given Nsm$^{-1}$ but I can only find Nsm or Nsm$^{2}$ online, leading to more confusion over whether or not I have the correct units.


texts: accurate measurements with less accurate tools

texts: Is there a good way to systematically increase the accuracy and precision of a measuring tool using only mathematical means?  For example, average 10 measurements from the same tool can create a better measurement. Or using two independent tools and average them.  I don't know if measuring theory or statistical quality control or other subject can help.


texts: Why is the gain of an op-amp 0 when it is saturated?

texts:
My initial question got raised after a statement I read in a book under negative feedback - “It is assumed that the op-amp is not saturated”. I wanted to know why.
According to my consequent research, the gain of an op-amp is 0 when it is saturated. Why is this the case? Moreover, why is this a reason for my initial question?


texts: Adding an incrementing variable on autocad script

texts:
I have the code below:
;Start of Script 1
;command
-pdfimport
;leave empty to select file
f
;file location
"C:\Users\Lenovo\Desktop\Electrical Department\samplepdfonly.pdf"
;pagenumber of pdf
4
;specify insert
0,0
;scale factor
1
;rotation
0

;End of script 1

;Start of Script 2
;command
-pdfimport
;leave empty to select file
f
;file location
"C:\Users\Lenovo\Desktop\Electrical Department\samplepdfonly.pdf"
;pagenumber of pdf
8
;specify insert
800,0
;scale factor
1
;rotation
0

;End of script 2

;Start of Script 3
;command
-pdfimport
;leave empty to select file
f
;file location
"C:\Users\Lenovo\Desktop\Electrical Department\samplepdfonly.pdf"
;pagenumber of pdf
9
;specify insert
1600,0
;scale factor
1
;rotation
0

;End of script 3

And I'm trying to make this part, automatically adjust by adding an incremental variable of +800
;specify insert
0,0

For example, it will then becomes
;specify insert
800,0

then
;specify insert
1600,0

Is it possible?
In programming it is something like
Var X as integer = 0

Then
;specify insert
x+800
x,0


texts: Does the controllability of nominal system imply the controllability of the actual uncertain system?

texts:
Given a system dynamics
\begin{equation}
\dot{x}=A(p)x+Bu,
\end{equation}

where $A(p)$ is the uncertain system state matrix with the nominal matrix being $A(p_0)$. The uncertainty in $A(p)$ satisfies the matching condition, i.e.
\begin{equation}
A(p)-A(p_0)=B\phi(p)
\end{equation}

Now from the book "Robust control design (an optimal control approach)" I encountered an exercise problem which goes as follows:

If $(A(p_0),B)$ is controllable, show that $(A(p),B)$ is also controllable for any $\phi(p)$ where $A(p)=A(p_0)+B\phi(p)$.

My approach was to use the rank condition of the controllability matrix for the nominal case and extend that result to the original system but it does not give me the result I expected. Any hint will be much appreciated.


texts: Experimental method to determine the centre of mass for 3D object

texts:
I have to determine the centre of mass for a 3D object (bounding box: approximately $0.30 \text{ m} \times 0.20 \text{ m} \times 0.10 \text { m}$) that is not regular and does not have a uniform density. I know how to determine the centre of mass for a flat object. I thought that I could try to use a similar approach for the 3D object, but the problem that I have is that I cannot determine the intersection of the planes as it is somewhere inside the object.

Then I thought I could use a balance for three directions and determine the centre of mass by finding the point of balance for all three "main directions".

  Is the last method a good method? What is the best way to determine
  the centre of mass by measurement?


texts: Enclosure temperature regulation using recirculated exhaust

texts:
I need to put a Dell PowerEdge C2100 server in a detached garage in Colorado with no HVAC.  I'm trying to figure out how to design an enclosure around the server that will recirculate hot exhaust air such that the intake temperature stays above around 60F.  When the ambient temperature in the garage is over around 60F, intake must be isolated from exhaust (no recirculation) to avoid overheating (in the summer it can get above 100F in there).  I'm thinking some arrangement of motorized damper(s) that adjust automatically based on the intake temperature.
The C2100 is a 2U chassis that draws air in the front and exhausts it out the back.  Mine uses around 285 watts.  The entire front is covered in hard drives.  Recirculated exhaust must be thoroughly mixed with ambient air before it hits the front of the server.  Freezing air entering the bottom (for example) of the server and hot air entering the top will not work.


texts: Calculating Required Motor Power for Robot

texts:
I'm building a robot that will weigh less than 75kg, and be capable of carrying people, so I need to select motors that are powerful enough to move about 166kg at a speed of 12mph, with standard 18in golf-cart wheels.

The 20s acceleration was arbitrarily chosen because it seemed reasonable.

These are my calculations:

200 lbs person is 91 kg.
Total Robot Weight: 75 kg + 91 kg = 166 kg

Calculate Required Torque:

12mph / 20s is 0.268224 m/s^2
0.268224 m/s^2 * 166 kg is 44.5N of Force
44.5N * 18in (Wheel Diameter) is 20.3 J (aka N*m) of Torque

Potential Motor:

ZY6812 250W24V (Razor E300 Motor)
Specs: 3350RPM No Load, 2750RPM Load, 0.9 N*m, 8.9A (15.4A Stall)

Motor Torque:

4x motors = 1000W @ 3.6 N*m of Torque total.
1:8 Gear Reduction -> 22.8 N*m Torque @ 418.75 RPM.

Motor Speed:

12mph with 18in wheels = 224 RPM Required Speed.
250W / 20.3J = 12.32 Hz = 739.2 RPM, so speed is possible with desired torque.
22.8 >= 20.3 and 418.75 >= 224, the motors can move 166 kg at 12mph or more and accelerate in 20s or less.

Supposedly, 4 of these 250W motors should be enough to carry the weight at twice the speed, given a 1:8 gear ratio. Are these calculations valid, or did I mess something up horribly?


texts: Could engines run on 1 cylinder while idling to save fuel? And then either each "idle" session alternate a different cylinder so wear and tear is even, or change the active cylinder periodically throughout an idle session (i.e every 1 minute idle, change the singular active cylinder). I realize that this is probably pointless with modern start / stop features on many newer engines, but why wasn't my idea possible before we came up with the tech to enable modern start / stop on engines?


texts: What mechanisms can be used to move a drum at constant speed without an electrical system?

texts:
How could I design a paper spool or drum that is moving at constant speed without electrical system? What mechanisms are available?

I know that some paper tracing system was being used in 19th century to track vibration frequency.


texts: Is there a way to add together the rotations of two spinning gears, which are spinning in opposite directions, into one rotation?

texts: Two gears are spinning is opposite directions, I would like a third gear to spin in one direction (the direction is not important), and this third gear must be the sum of the motions of the two gears. The speeds of the two gears can vary. If they were spinning at constant speed, this would be easy for me, however they are always changing.


texts:
I don't know if this is even possible or not but are there any pads that can transfer/exchange heat from one side to the other side unilaterally?
I mean that the heat could be transferred from one side to the other, but can't do the same in reverse.
If there is any confusion please comment and I will try to explain better.


texts: Beam question to find the maximum stress

texts:
I tried the question but I didn’t get the correct answer, can anyone tell me what mistake I made?

$$\begin{align}
I &= \int y^2\text{d}A \\
&= 25^2\cdot10^{-6}\cdot200\cdot50\cdot10^{-6} \\
&= 25^2\cdot10^{-8} \\
\sigma &= \dfrac{My}{I} \\
&= \dfrac{10^3\cdot25\cdot10^{-3}}{25^2\cdot10^{-8}} \\
&= 4\cdot10^6
\end{align}$$


texts: How do I choose operating parameters for input air to a methane reformer?

texts:
I'm interested in controlled oxidation of nickel in a methane reformer with diameter ~3 m and height ~1.5 m. In this reactor, CH4 is converted into H2 and CO, and CO into H2 and CO2 but for this problem, we assume that the methane and water stopped flowing in the reactor and that all these substances are not present in it during the oxidation process. So the idea for the nickel oxidation is to let some air flow in the reactor by controlling the following three parameters:

The percentage of oxygen in the air I let flow in the reactor.
Its flow rate.
The temperature of the air injected

What are the realistic values that these three parameters can take?  I've searched the internet but I could not find any information about how the air generation step (that's how it's called) works and what exactly is producing the air flow (turbine?).


texts: I might be wrong here. The solid modeling done in CAD like Catia, NX, Solidworks,etc can be taken as input in CNC and the desired shape and size of piece can be obtained.The CAD itself convert the model into G -code.So why do we need to learn CNC programming if CAD can do it? Stay safe.


texts: Which uses less energy to heat a room: central steam heat, or a ceramic space heater?

texts: My partner and I are having a friendly debate. We live in a walk-up style apartment building which has a radiator-like unit in the corner, which we believe is connected to some sort of central steam heat (ie, the steam is piped through the radiator from a central unit in the basement, which heats our house). We also have a ceramic electric space heater. We're curious which of these methods of heating our living room is more "environmentally friendly" - that is, which one will consume less energy (from the power/gas company) to increase the temperature in our living room by one degree.  We're assuming that the steam is generated by a gas boiler, and the electricity by an oil-fired power plant.


texts: Estimating the quality factor (decay properties) of an object's vibrational modes?

texts:
I am attempting to model the acoustic behaviors of a circular membrane (drum head). I know that software like ANSYS will give me the modes of vibration pretty easy from a simulation.

But what if I also want the Q (quality factors) ie. decay properties of the various modes? Is there any way to determine that? Can ANSYS do this? If so, how? If not, which software can provide it and any basic starter tips on how to get it?

Please excuse me if this is a very basic question. I am not an engineer of course but I am doing my best to figure out things as I go for my goal. Thanks.


texts: Need to generate mechanical vibrations for experiment in ISS

texts: For a school scientific experiment to be flown onboard the ISS in a few months, I need to generate mechanical waves in a cylindrical capsule made of polycarbonate filled with oil (height about 9 cm, radius about 2 cm, wall thickness a few mm) and electrically heated on one side. Objective is to study heat conduction in oil in microgravity, with and without mechanical vibrations propagating in the oil. Frequency needs to be varied and in the range 3 kHz to, say, 100 kHz. Amplitude of vibrations should be high enough to, hopefully, generate standing waves in the oil. Thought of using a ceramic heater to heat the oil, and a piezo transducer to generate the vibrations but really don't know about possible issues with these ideas. Any advice highly welcome !! Thanks !


texts: Reduce 180 degree rotation to 90 degree rotation without gears

texts:
I am actuating a small ceramic rotary valve with a cheap mg996 servo motor. The valve has a 90 degree max rotation from fully closed to fully open. Currently I have the servo shaft directly coupled to the valve shaft, and simply limit maximum rotation of the servo to 90 degrees in software.

It would be nice to have the extra resolution afforded by utilizing the servo's full range.

Is there a simple way to reduce the 180 degree rotation to 90 degrees without gears? Space is tight and complexity needs to be minimized.

A push/pull rod on an arm may be the best option, but I'm not aware of other ways to do this.

Note: I have access to a 3d printer.

Thanks!


texts: Can anyone explain calculation of net force due to pressure in a streamtube of fixed control volume and infinitesmal size

texts: I am studying derivation of bernoulli equation from FM White's fluid mechanics and in that  pressure distribution is as shown in the image 1. I am unable to understand force calculation as shown in image .


texts: Analytically determine and draw the system response to a piecewise step input for an electrical system

texts:
Picture shows the electrical system. Analytically determine and draw system response $u_2(t)$ for the step input shown (use Laplace transform) (tp>>0).

So, I know to solve RC system transfer function and get G(s)=1/(RCs+1), but I don't understand how to do this problem, we have never done it in class and professor often asks this question. If anyone could help me out, thank you!


texts: Material balance without chemical reactions

texts:
This is a practice question that I am trying. I am a student learning about material balance-

I am trying to find the mass composition of stream D.
The one written in pencil is the values that I have found in advanced-

My attempt-

I have made a material balance around separator 2 ignoring the recycle stream,

I done up a component X balance-

$1250 X + (120 \times 0.3) = (379.08 \times 0.374) + (90.92 \times 0.222) $

I solve for x $= 0.10076$

Similarly,I done up a component Y balance-

$125 Y + (120 \times 0.7) = (379.08\times0.626) + (90.92\times 0.778)$

I solve for Y $= 0.1792$

I know this is wrong as the composition of X and Y total does not add up to 1. Where did I go wrong or what must I do ?


texts:
I'm building an outdoor shelter and I'm wondering what would be:

The maximum beam span for the type of wood/material used such it can support the roof weight and not sag in the middle,
Suggestions on other materials (beams or otherwise) or construction techniques that you'd recommend I use instead.

The current beams as currently designed are two standard 2x10's sandwiched together.

The roof is 30°. The trusses are 2x6's which will have four blocking bars between each set of trusses. The roof trusses are currently 20" apart OC.

The distance I have it currently span is 9.5', but I'm interested in increasing that distance, and knowing about how far I can reasonably go.

The plan for the roof is 1/2" plywood with tar paper and shingles.

Here is a picture to help illustrate what I had in mind. (Note:  I do have plans for diagonal braces between the columns and the beams, I just didn't bother to illustrate it.)


texts: Are we capable of building bigger high pressure cylinders?

texts:
Check out this 200-300 bar cylinders:

Is it practically possible to build a bigger cylinder of say: 10m x 1m - and make it hold a pressure of 300 bar in a safe way?

I can understand that bigger cylinders might not exist due to the fact that are not needed - not practical/commercial in industry to have something bigger then a human can move around - but for what im thinking, a bigger cylinder might be needed.

Can we build it with steel and using standard practices? Or we already reached some limits and this is why we settled for this cylinders with dimensions like in the picture? Sorry if this is a stupid question. Thanks :)


texts: Creating a custom field output in ABAQUS

texts:
I want to create a custom field output in ABAQUS. For the purpose of proof on concept, I want to display the maximum shear stress as calculated from the Mohrs circle, as discussed here for a 2D shell.

I have my code below for reference:

from abaqusConstants import *
from odbAccess import *
from math import *
from copy import deepcopy
from caeModules import *
from driverUtils import executeOnCaeStartup

# ******************************************************************************
#Items in this box require student input when changing files

#must input the file path here.
odbPath = "/home/MohrsTest.odb"

odb = session.openOdb(name=odbPath, readOnly=FALSE)
odb = session.odbs[odbPath]
#this will display the instance names. Please choose one to input in line 14.
print odb.rootAssembly.instances.keys()
grout_instance = odb.rootAssembly.instances['SQUARE-1']
# ******************************************************************************
keys = odb.steps.keys()
for key in keys:
    step = odb.steps[key]
    for frame in step.frames:
        print frame.description
        Stress = frame.fieldOutputs['S']
        #try modifying scalar fields rather than creating new var element by element.
        S11=Stress.getScalarField(componentLabel="S11")
        S22=Stress.getScalarField(componentLabel="S22")
        S12=Stress.getScalarField(componentLabel="S12")
        TauMax=((S11+S22)*0.5+sqrt(power((S11-S22)/2, 2)+power(S12, 2)))-((S11+S22)*0.5-sqrt(power((S11-S22)/2, 2)+power(S12, 2)))/2
        ThetaP=(atan2(2 * S12, (S11 - S22))/2) * 180/pi
        frame.FieldOutput(name='Tau Max', description='Max Tau from Mohrs circle',field=TauMax)
        frame.FieldOutput(name='Theta P', description='Thetap as measured ccw from 0 degree',field=Thetap)
odb.save()
odb.close()
#  must re - open the output database to see the new custom field output

Abaqus throws an error immediately upon trying to calculate TauMax because of "Type Error: A float is required." However, I tried using "Tools->Field Outputs-> Create from Fields" and then created a field output in the cae for the individual frame.
If I look at the replay file for this action, I can see the following code:

s1f1_S = session.odbs['/home/MohrsTest.odb'].steps['Step-1'].frames[1].fieldOutputs['S']
tmpField = (((s1f1_S.getScalarField(componentLabel="S11")+\
    s1f1_S.getScalarField(componentLabel="S22"))*0.5+sqrt(power((
    s1f1_S.getScalarField(componentLabel="S11")-s1f1_S.getScalarField(
    componentLabel="S22"))/2, 2)+power(s1f1_S.getScalarField(
    componentLabel="S12"), 2)))-((s1f1_S.getScalarField(componentLabel="S11")+\
    s1f1_S.getScalarField(componentLabel="S22"))*0.5-sqrt(power((
    s1f1_S.getScalarField(componentLabel="S11")-s1f1_S.getScalarField(
    componentLabel="S22"))/2, 2)+power(s1f1_S.getScalarField(
    componentLabel="S12"), 2))))/2

Thus, clearly math operations on a FieldObject must be possible. Why does my code not permit this?

I am happy to provide all .odb and .cae files for reference and verification.


texts: Efficiency of TurboJet engines with nozzles

texts:
As per Bryton Cycles, most of TurboJet engines' Thermodynamic efficiency should be around 40%. Rest of energy gets rejected as waste heat in exit gases of after the turbine.

But if these hot gases from the turbine are passed through Nozzle of 95% efficiency (either Convergent or CD), then overall efficiency should be 95% Right? Because Nozzle is scavenging all the waste heat and pressure, converting it into Kinetic energy of gases.

As per my knowledge nozzles are extremely efficient devices with efficiencies above 95% (Please do comment if that's not the case). And for the sake of discussion please assume Combustion efficiency as 100% and no mechanical loss. And here I'm considering whole purpose of turbojet engine it propell the gases as fast as possible. So overall efficiency here is kinetic energy of exit gases vs chemical energy released by fuel.


texts: How does placement of a pressure gauge in a tank of fluid affect the pressure readings?

texts:
This is not a real system but rather something I made up to understand how the placement of pressure gauge in a tank takes its readings.

Here’s a diagram of it-

The pressure gauge placed in the middle of the tank. Let’s say I’m working in gage pressure.

Which point in the tank does this pressure gauge measures until ?

Does it measure till the middle point only ?

For example - pressure at the level where pressure gauge is placed -
P (vapor) + P (liquid at h=1m) = $120 + \rho g h$ = ____ kpa


texts: Spatially dependent material property in Abaqus/CAE

texts:
I am modelling a plate as 3D deformable solid. My plate has a spatially dependent isotropic thermal expansion coefficient.

I have defined this spatial distribution as a Discrete Field in a tabular form (for the mesh elements). My question is how can I link this distribution to my material definition? Or is it not possible to have spatially dependent thermal expansion in Abaqus/CAE?

Thanks!


texts:
I have the utilization rates of several machines for each week over a year. These differ per week because of the occurrence of machine failures and changes of orders. Meaning that one week a machine could be a bottleneck and the other week not. I want to rank these machines based on the utilization and so determine their criticality. However if I calculate the mean utilization, information gets lost. The same is when I count the events the utilization is bigger than a threshold. For example;

machine A has a utilization of 50% and 14 weeks the utilization > 90%
machine B has a utilization of 70% and 7 weeks the utilization > 90%
machine C has a utilization of 89% and 6 weeks the utilization > 90%

In my opinion machine A is more critical than machine B. So ranking based on a threshold value seems reasonable. However, when comparing machine B and C this is not that clear. Does anyone know a statistical/mathematical method to get a good comparison?


texts: How can I model or simulate motion caused by an internal vibrating motor?

texts:
I have a vibration motor contained in an object. The motor looks similar to this:

When the motor is running, I want to simulate the movement of the container object that results from the vibration of the motor. I'm able to model the parts/assemblies in SolidWorks. How can I model or simulate the movement of the motor and the container object?


texts: Steady Non steady and Uniform Non Uniform flow

texts: Thanks in advance, can someone explain Steady,Non steady, Uniform and Non Uniform flow and provide some example for each.


texts: Flow metrics of water at 12 bar through a 6" diameter open ended pipe 100 ft long

texts: I have a water jet pump pushing water through a 6" diameter open ended pipe 100 ft long, I need to get 12 bar gauge pressure on the pump discharge, what size (m3/hour) pump do I need ?


texts: How to derive a value from a transfer function

texts:
I have a scenario where a valve q_in(t) is pumping water into a tank of height h(t) and area A, which is then pumped out by a second valve q_out(t) that has a resistance to water flow R.

I got this transfer function:

$ \frac{H(s)}{Q_i(s)} = \frac{R}{A R s + 1} $

Where R= 1.5m(m^3/min) and A= 2m^2

I would be grateful if someone could tell me how to get the value of Rs so I can plot the transfer function in Labview!


texts: Physical principle behind suction of a piston

texts: I'm sorry if the question is trivial but for me it is not. I'm wondering what's the principle behind the suction process in a piston pump or in a piston of an internal combustion engine. I mean when the piston goes down, pressure inside lowers and air/water enters. Is it the conservation of momentum?


texts:
What FEA software is capable of simulating static studies on orthotropic materials such as wood? I must be able to define mechanical properties in X,Y and Z. I would also like to have access to failure criteria such as tsai-hill or tsai-wu and probably even other custom criteria. My company uses solid edge simulation at the moment but i have not found a way to account for orthotropic materials, I also tried solidworks simulation on my side and I was able to perform most of what i need but i want to consider any additional options before i make a recommendation to my company to shift to a new software.
Any hints or advice would be greatly appreciated.
Cheers!


texts: shifting weights and locking in place at different angles

texts: Hi i would like to ask if there's any ways i can shift weights and lock it in place at different angles (180 degree to 90 degree)  without using electronic devices- preferably using wood as the main material. I have tried using a slider to guide the weights and by pushing the rod that is holding the weights to lock it in place. However, it is not feasible as it is too complicated and the weights does not move smoothly.


texts: What is the effect of Aluminium nitriding in steel?

texts: "The most significant effect of AlN in steel is on grain size control, which directly influences hardenability, hot ductility, texture development, and mechanical properties."I have read this statement somewhere.However what I do not understand is how is grain size control a determining parameter here.A detailed explanation to this is most welcome.I feel the effect of Aluminium in alloying as far as nitrding is concerned is one of the most sought for.


texts:
I have some questions in the basics of machinery terminology

Can a spring ever be a link? Most books (eg. Ham et al. 58, Shigley pg. 5) consider links to be rigid. However, I have come across articles using springs as links.
Are joints always the same thing as kinematic pairs, or do they ever differ in any particular circumstances?
Is mechanism a subset of kinematic chain or is chain a subset of mechanism? Some books mention if there is no fixed link, then the combination cannot be called a mechanism but can be a kinematic chain.


texts: Writing a filtered derivative term of the PID controller into the C++ code

texts:
Everywhere I look, be it a PID, lead, lag control or anything else, there are Simulink schematics with transfer functions. This is all nice for system response simulation, however currently I have to implement a PID control with a filtered derivative term into a strictly certified medical device, which is controlled by a microchip with a C++ code controlling it.

Now, if we take the PID controller in its frequency domain as

$$C(s) = k_\mathrm{P} + \frac{k_\mathrm{I}}{s} + k_\mathrm{D}s = \frac{y(s)}{e(s)},$$

we can implement that as

$$y(t) = k_\mathrm{P}e(t) + k_\mathrm{I}\int_{0}^{t}e(\tau)d\tau + k_\mathrm{D}\dot{e}(t), \quad e(0) = 0,$$

which we can write into pseudo code as

integral += error*dt
derivative = (error - prevError) / dt
y = kp*error + ki*integral + kd*derivative
prevError = error

However, now we take the filtered PID control as

$$C(s) = k_\mathrm{P} + \frac{k_\mathrm{I}}{s} + k_\mathrm{D}\frac{sN}{s + N}$$

The best I can think of is to create inverse Laplace as

$$y(t) = k_\mathrm{P}e(t) + k_\mathrm{I}\int_{0}^{t}e(\tau)d\tau + k_\mathrm{D}\left( N\delta(t) - N^2e^{-Nt} \right)e(t), \quad e(0) = 0,$$

but what does that really represent? Integrating via $dt$ is one thing, but all I can see in the $e^{-Nt}$ is the fact that after few seconds, no matter what I do, I am going to have just another proportional constant. Should I reset the time at some point? And we haven't even written that into C++ yet.

What is the correct approach?


texts:
first of all i am must say that i don't know much about cad systems .

i am a software developer and i was given a task to make a webgl application that show some products in 3d .

the product is composed from multiple parts and i was given each part in a separate "STEP" file .

converting these file in other format like obj, fbx etc and showing them in 3d is not a problem
but how to position / rotate each part(file) in 3d space accordingly to other parts ?

is there any option in this cad system specification that can help on that ?

thanks


texts: Are there standard vibration and shock specs for shipment of a product?

texts: Suppose I want to ship my product via UPS, or whatever other professional carrier service. What vibration and shock forces should I design my product to withstand? And how can I effectively test my product against those forces?


texts: Significant amount of heat is lost from an engine by various means, so to recoup the energy, is it possible to increase efficiency via heating of diesel fuel prior to injection using waste engine heat in passenger cars similiar to marine diesels? Are there any recent journals or studies in this matter?


texts:
How to design a drop panel at a column in case the column above is rotated or not aligned to the below column (see image below), the code that i am using is the ACI Code if any reference for the design of such a case is available.

In another cases we usually use the drop panel to reduce the span between two columns and reduce the effects of shear on slab (especially punching shear), in case of seismic/wind resisting building is there any loads or changes to the design of these special elements and how do they affect the behavior of the building ?

Thank you in Advance.


texts: How to determine signal strength verses distance for LTE base stations?

texts:
All mobile phones have bars or some other type of indicator displaying signal strength. As mobile devices move away from the base station the signal strength becomes weak and at some point becomes out of range or establishes connections with a different tower.

Question: For a LTE base station is it possible to determine the relationship between the signal strength and distance?

Assumption: LTE base station is located in a plain field.

Back story: A cellular service provider is planning on installing a LTE base station using equipment from JMA wireless. The model number of the equipment is X7CQAP_FRO_645. Below is a H-plane pattern plot for 750MHz frequency.

Can anyone provide insight as how to interpret the above plot in relation to signal strength verses distance? Do I need more information?


texts:
I am trying to model this system but am having difficulties in setting up the equations of motion. This is a simplified model of a motorcycle suspension system, where P is the ground in the image below. In addition, the variable $u$ is the input to the system, which is the displacement from the ground (like a motorcycle going over a bump).

Consider mass $m_2$ first. Keeping $m_1$ fixed and displacing $m_2$ a bit yields the equation of motion for $m_2$ as
$$
m_2 \ddot{y} = -k_2 (y-x) -b_2 (\dot{y} - \dot{x})
$$

And similarly, for $m_1$, keeping $m_2$ and $u$ fixed and displacing $m_1$ a little bit, the equation of motion comes out to be
$$
m_1 \ddot{x} = -k_1 (x-u) -b_1(\dot{x} - \dot{u}) - k_2(x-y) - b_2(\dot{x}-\dot{y})
$$

The first two term on the RHS come from the coupling of $x$ with $u$ while the second and third come from the coupling of $m_1$ and $m_2$, or equivalently from Newton's third law. However, the textbook solution only has the first two terms, and not the interaction between $m_1$ and $m_2$ for the EOM of mass 1. I am extremely confused as to why this is the case. Is it because they are vertical and not horizontal? How would the EOM change if the scenario was all horizontal?


texts: Recycling materials like plexiglass, polycarbonate and dibond

texts:
I'm working on a project for a printing company with the main goal to reduce their waste. Paper products are not the issue but they also use materials like plexiglass, polycarbonate and dibond.

I was wondering if it is at all possible to recycle those materials and how. And if not, what happens with them?


texts: Does kettle shape affect the speed at which water boils?

texts:
Consider I have two type of cooking kettles, which the shape is just like a pure tube with the volume is 1000 cc (1 liter) with the radius and the height as below (volume=pi*r^2*h):

The first kettle: cross-section radius=5.6419cm and the height=10cm.
The second kettle: cross-section radius=3.9894cm and the height=20cm.

Those two kettles filled up with the same kind water from a same source. Consider that I have a small stove that that its flame will be enough to boil the water inside those kettles. Also consider that those kettles has enough additional height so the water will not get spilled when it start boiled. Then my questions are:

Which one will be get boiled faster (shorter time)?
When they are get boiled, which one is healthier (due to it distribute the heat uniformly to that water inside the kettle)?

Edit:
Water will be filled up from top. Say that there is a small cap to fill water into it. There is no other hole.
Flame on the stove are put the same distance for both the kettles, close enough so the flame will be effective to heat the water.


texts: Gear train using two inputs and one output. Understanding six link epicyclic gear topology - Interpreting displacement graphs

texts:
I'm interested in printing a working two degree of freedom planetary gear set. I searched around and found a paper from University of Maryland in 1988 (source). I am having difficulty translating the information into a real-world model.

The goal is to make a system that allows two independent inputs to affect the speed and torque of a single output. As the paper points out, a differential system doesn't quite make this possible.

  Although mechanical systems with multiple inputs or multiple outputs have existed for many years, generally, they have been used as a series of one-DOF devices rather than as true multi-DOF mechanisms. For example, the automotive bevel-gear differential, a two-DOF mechanism with one input and two outputs, is made-up of a one-DOF gear train in series with its gear box.

I tried analyzing a standard differential system but I don't believe you can alter it to use two independent inputs. The six link systems described in the paper seem to be the right direction, and so I would like to understand the graph.

Here is the figure from the paper:

And here is my attempt to interpret graph 6-1-1:

I think this is clearly incorrect because elements 5 and 6 have no effect on the system. Could anyone help me interpret the graph?


texts:
When bolting something like a flange or a dead/blind end to a port on a pressure vessel (lets say rated to 2 ATM), is there a good rule of thumb on how much of the threading should be engaged into the tapped hole in the vessel?

Is there an ISO standard or something and if so can someone provide a reference to the standard?


texts: Why does a radiator valve require more torque after a few turns?

texts:
I'm automating a non-thermostatic household radiator valve, by replacing the knob with a DC motor and adding some support structure. You can see the system at work here: https://www.instagram.com/p/BRQ8xS9gPPN/

The motor applies a constant torque and stops automatically when it stalls, i.e. when the valve can't turn anymore. The water flowing in the valve has a temperature of 60-62 degrees Celsius.

After a repeated stress test (fully open, wait 5s, then fully close, wait 5s, repeat), starting from a closed position and the radiator at ambient temperature, I noticed that the time required to open and close the valve had increased over time. It seemed like the valve is getting harder and harder to turn.

My strongest suspect is an effect of heat. If so, what could be happening? Is the valve opposing more resistance, or the motor providing less torque? Is it something that I have to take into account during regular use? What other causes could lead to this phenomenon?

Unfortunately I couldn't do other tests because some parts broke due to mechanical stress. Will update this post when I'll have more results.


texts: Is it possible to read a USB port directly?

texts: In Windows is it possible to write a simple program to read the binary value of a USB port without going thru a USB driver?


texts: Derivation of specific helmholtz function relationship for an ideal gas

texts:
The question is to prove the following form of helmholtz function for an ideal gas

$$f=C_v (T-T_0)-C_vT \ln \frac{T}{T_0} -RT \ln \frac{V}{V_0} -s_0(T-T_0) +f_0$$

I tried using $$df=du-Tds-sdT$$
Now $du=\frac{\partial u}{\partial T}dT +\frac{\partial u}{\partial v}dv$ we know $C_v=\frac{\partial u}{\partial T}$ and from $du=Tds-Pdv$ we get $\frac{\partial u}{\partial T}=T\frac{\partial s}{\partial v}_T-P$ which from Maxwell relationship is $\frac{\partial u}{\partial T}=T\frac{\partial p}{\partial T}_v-P$

I am unable to proceed after this.Any ideas? Thanks


texts: What is an acceptable tolerance for a non-engineering dimension

texts:
I have part that I'm dimensioning and setting tolerances on. Some of the dimensions/features have engineering requirements (e.g. press fit) and I have the tolerances set correctly (e.g. H7).
But I have some dimensions / features don't have any engineering requirements. They are usually outside dimensions or "free" surfaces that don't interact with any other parts. Technically the tolerance could be +100% of the nominal value. But this just seems "sloppy". I would like the parts to be roughly uniform. So how can I communicate on my drawings that the dimension is not critical without supplying an outrageous tolerance? Is there a  rule of thumb for this sort of thing? Say 10% of nominal dimension?


texts: What glue would be suitable for adhering a space blanket to Plywood?

texts:
I've been doing a hobby project, creating a parabolic solar reflector to heat up a pipe of flowing water.
I did this by cutting a stack of parabolas with a CNC router and secured a thin piece of plywood along the curve (imagine an extruded parabola)
I then bonded a space blanket (emergency blanket) with PVA to the plywood.

Initial tests worked very well, it was actually burning the plastic pipe I originally used so have since changed to copper.

The issue is that the space blanket seems to have deteriorated (the reflective foil has gone clear) at points where the glue has not set properly (places where there is a build up of PVA and has stayed wet)

My suspicion is that the wet PVA is somehow eating into the foil lining, so I need a new type of glue suitable for this application.
Has anyone any idea of something that is low cost and won't cause problems?

Thanks in advance!

_

Extra info from wiki on space blankets:
"The material consists of a thin sheet of plastic (often PET film) that is coated with a metallic reflecting agent, making it metallized polyethylene terephthalate (MPET)"


texts: Is dimension of angular displacement never degree?

texts: Is units of angular displacement never a degree and is always a radian ?


texts: How to add external sensor data to pictures, canon DSLR, hot shoe, electronics

texts:
Here's a challenge -

I am trying to add different sensors data (height,temperature,distance by laser) to pictures i take with a canon DSLR camera.

Would it be possible to connect different sensors through a canon DSLR "hot shoe" or other camera input?
and then add the sensor information to the picture at the precise moment the picture was taken?

for example - have a temperature sensor connected to the camera, and add the temperature data to the image stored in the camera.
same way other data that comes with taken pictures such as geo location,shutter info, etc..

i need it to be VERY precise timing wise - exactly on the time the picture was taken.

would love to hear your ideas,
Also looking for someone who can do this as paid project.

Macgyver


texts: ASTM grain size: diffusion of nickel in copper

texts:
Question:
  All other factors being equal, the diffusion rate of nickel is the highest in copper with ASTM grain size number of:
  A. 4
  B. 6
  C. 8

Honestly, the question does not appear to be very intuitive - I've searched through my notes and cannot seem to find any relatable formulae. I understand that the number of grains per square inch at 100X magnification is equatable to 2^(n-1), where n is the ASTM grain size number of the specimen.
However, given the multiple-choice nature of this question and the apparent lack of information (I suppose the copper and nickel are pure, at room temperature, etc.), I must be overlooking something simple.

Would anyone be willing to advise?


texts: Looking for advice on how to turn off a motor when there is an item blocking a sensor. I found an inductive proximity sensor that I think could work. I am trying to make a brass case annealer similar to this one


texts: Can I use loadcell for vibrating force measurement?

texts:
Is it possible to use a load cell to measure a force that is vibrating? The idea is to measure that force that is getting into the load cell in a sweep of frequencies and vibration is NOT a noise. Since most of load cell characteristics indicate static  conditions, I was doubting if load cell is not right for dynamic measurements. Alternatively, is there a special family or model of load cells that could work under vibrating conditions?
The frequency of interest is in the range of under 500 Hz ( or let's say 1K)


texts: Vertical vs Horizontal Ground Loop Heating

texts:
I'm wondering how to compare the efficiencies of vertical and horizontal ground loops for heating. [Assumptions follow, please correct if any are wrong!]

The biggest differences seem to be the higher cost of vertical loops vs the land required for horizontal loops, so therefore I'm having trouble finding any information on how to compare the energy input/output of similarly sized systems.

I'm interested comparing the two systems, so at the risk of getting off the question: in my area, average winter temp is a low of -6F/-20C, and a high of 12F/-11C, with cold snaps of -40deg. Frost gets to 70in/ 1.7m in the colder winters. If comparisons want to use that info, I would be very curious.

Thanks!


texts: Is it necessary to use PID control in my use case?

texts:
I have a workflow of two functions. Both of them aggregate the items that are receiving and only the first is adjustable. I mean that I can decide how many items to aggregate on the first function F1 in order to not exceed the capacity (bandwidth) of the channel that connects to the second function F2. In other words, I control the throughput that the second function is receiving items. If I aggregate more at F1 I decrease the throughput. If I aggregate less at F1 I increase the throughput. My goal is to tune the system for its maximum throughput while the input workload varies and I have a limited channel between F1 and `F2. This it the picture of my system:

The data stream of items (workload) that F1 receives varies along the time. I want to control the throughput output of F1 in order to not surpass the channel capacity.

I am planning to use PID control to decide how many items to aggregate on the first function before to emit the items to the second function. I am a newbie in control systems. As far as I understood I have to start with the Proportional controller (P) which is basically the current error. Then I have to decide if I will use the Integral controller (I) which is the historic cumulative value of the errors. And then I have to decide if I will use the Derivative controller (D) which is based on its current rate of change.

For me, it is not clear yet if I really need the Integral and Derivative controllers. I mean, if I find the error between the actual throughput and the desired throughput I just set the first aggregate function to aggregate items in order to have the desired throughput. In my mind this is enough, isn't it?

Something could influence is the time that I take to aggregate items on the first function. Suppose that I have a slow processor. But, in my use case what is the insight that I have to have in order to use the Integral or the Derivative controllers?

Thanks,
Felipe


texts: What is the thinnest possible depth of any given material required to display an image?

texts:
I am interested in creating a screen to display moving images (similar to moving desktop background), however I am looking for the thinnest possible material available i can use as the screen to display the image.

Ideally working in the same way as a laptop screen however much thinner (E.g only using the components necessary to display the image, no housing).  The material can be any at this stage, such as plasma, LCD, LED, etc.

My intention is to create something that works in a similar way to wallpaper, where it can be applied directly to a wall, and for it to be connected wirelessly to a transmitter in order for it to display a moving image.

Any answers would be much appreciated. Thank you


texts: What are the benefits of reducing valve duration in an engine?

texts:
From my understanding this would be beneficial if you've taken a stock engine and put a smaller, more restrictive air intake on it.
It would also be done to create more low end torque which shifts the power band down the RPM range.
What other reasons would someone reduce valve duration?


texts:
I found the following comments on direct and indirect control in "Survey on iterative learning control, repetitive control and run-to-run control." by Wang, Gao, and Doyle:

  There are two application modes to use the learning-type control. First, the learning-type control method is used to determine the control signal directly, and this kind of learning-type control is called direct learning-type control. Second, there is a local feedback controller in each cycle and the learning-type control is used to update the parameter settings of the local controller, so this kind is called indirect learning-type control. The methods that can be used for designing direct learning-type control and indirect learning-type control will be discussed in Section 4 and in Section 5, respectively.

What is the difference between direct and indirect learning control? My understanding is that in indirect control you can alter the control parameters and the input signal as opposed to just the input signal in direct control; is this correct? I also do not understand the significance of a "local" controller.


texts:
I have been trying to model a custom gear to fit on to another physical gear. I having been using this 3d model gear generator. What I know about my physical gear is that it has:

(what I believe to be a diametral) Pitch of 32
Pitch Diameter of 1.5" (38.1mm)
Outer Diameter of 1.563" (39.7002mm)
20° Pressure Angle
48 Teeth

I have access to a 3D printer and am trying to calculate a gear that will mesh with my physical gear given these specs. I printed a smaller first gear that happened to mesh perfectly with the physical gear. When I increased the number of teeth (thus increasing the PD and OD of the gear in the generator) the teeth and distance between the teeth appeared to increase as well, not meshing well with the physical gear at all.

New gear specs:

Pitch Diameter of 1.2" (30.48mm)
Outer Diameter (Auto calculated, but I think it should be) 1.2" + .063" (30.48mm + 1.6002mm)
Same Pressure Angle
*No blacklash

  Is there a way to calculate a gear that will mesh, or will I have to
  empirically derive the gear tooth and pitch by printing out gear after
  gear to see if it fits?


texts: How does energy recovery recuperator work

texts:
In a recuperator http://en.wikipedia.org/wiki/Recuperator, sensible heat can be transfered by thermal conduction through the plates, and latent heat can also be transfered when the high temperature side has some condensation.

There seems to be recuperator products in which water molecule can go through the plate from one side to another. For example in http://en.wikipedia.org/wiki/Energy_recovery_ventilation:

  Enthalpy plates were introduced 2006 by Paul, a special company for
  ventilation systems for passive houses. A crosscurrent countercurrent
  air-to-air heat exchanger built with a humidity permeable material.
  Polymer fixed-plate countercurrent energy recovery ventilators were
  introduced in 1998 by Building Performance Equipment (BPE), a
  residential, commercial, and industrial air-to-air energy recovery
  manufacturer.

How does such "humidity permeable material" work?

If what is transfered is liquid water after condensation, then draining away the condensed water on one side and supply (from water supply) some fresh water into the pipe on another side will have the same effect (if there is any effect), there is no need for the plate to be water permeable at all which will reduce the isolation.

If what is transfered is steam, then how can a material permeable to steam but not permeable to other gas like CO2?


texts: Can you change an asteroid's albedo to take it off a collision course?

texts:
The amount of light that an object reflects is called its albedo; a scale of 0-1, 0 being a black body ad 1 reflecting all light. This question is probably going to be closed [It is "subjective" ?? No idea how] so I may as well be brief.

In the 1990's some scientists were suggesting that if you changed the albedo of an asteroid then it could be hotter on one side. That would change the curve of orbit. I have heard nothing since about this idea. I imagine that various ways would exist such as spraying the asteroid with paint or putting a solar panel on it. Is this possible? [I would ask if anyone is trying to do it but the rules of stack overflow say I can only ask one question.]


texts: What Is the Different Between Single Nipple, Double Nipple, and Pipe Nipple

texts:
I just work on the engineering company that specialize in water piping. I am confuse about the term of nipple. What is the different between Single Nipple, Double Nipple, and Pipe Nipple?
Hope somebody can help.
Thanks


texts: How do you exactly measure distribution functions?

texts:
Once we study vector calculus, we are all set to describe physical fields such as velocity fields ,  electromagnetic fields etc. The study makes sense to me mathematically but I can not imagine how we would measure such quantities. How exactly do you continuously assign a number to each point in space? The amount of measurements would be way too much.
As a note, though I started with mathematics I expect an answer which describes the experimental procedures which are done.


texts: Which way should I build stairs into a creek?

texts:
I have a little creek in my back yard.  It's slow moving and safe (as safe as a slow moving creek can be.)  I'd like to build a little set of stone steps into the creek and am not sure of the best structural/engineering/least impactful way of do it.

So here's the main question:

Should the stairs be pointing up river or down river?

I've attached an image (very rough) of what I'm thinking.  i'm not sure if the top version or the bottom would be better all else considered equal.


texts: Determining σxx on a 3d system with resolved forces (stress, strain, shear strain energy)

texts:
I am having trouble conceptualizing this problem. I have attempted it but am confused about a few things, I would highly appreciate any insight or advice for this.

I know you need to resolve P into its Y and Z components and that you can move them to the end of the beam.

I understand Py causes bending in the XZ plane and Pz causes bending in the YX plane.

I thought that Pz contributed to σzz and Py contributed to  σyy.

But, my lecturer said that both Py and Pz contribute to σxx.

I'm a little confused as to how this is possible when they are orthogonal to each other.

Both cause bending on the beam (Py causes torsion) but do they not bend the beam in different planes therefore shouldn't they contribute to different stresses?


texts: Planes visible only if selected or hovered and "eye" flag ignored in Solidworks

texts:
I have created empty assembly and got all planes invisible. They are visible only if hovered or selected.
On the following picture PLANE1 is selected and Right plane is hovered, so they are visible.

Planes Front and Top are invisible despite they are flagged with "eye" icon, which is evident from blue color in a tree.
How to make planes visible?


texts:
For brushless DC motors we have hall sensors to keep track of rotor; however, for stepper motor we don't know the actual position of the rotor and therefore while changing pulses with some speed it may happen that the rotor cannot keep up with the rotating magnetic field and lags behind. Then some unexpected behaviors may occur. How do we make sure that this is not going to happen? In practice, does it happen just above some speed value, i.e. below that speed everything is ok and no such problem occurs? Or what are some other aspects to consider for avoiding such scenarios.

Thanks


texts: Most efficient orientation of exhaust vents on top plate of chassis for air flow with regard to heatsink fins?

texts:
I'm looking for some advice from an ME or anyone who understands heat transfer,convection, etc.
I'm currently laying out in Inkscape a top panel for an audio amplifier I'm building. Now, my question lies in the orientation of the exhaust fins that I will be having laser cut out of acrylic.
There is a need for these exhaust fins so the cold air from below the heatsink has a place to go.
Now, in regards to the image below, does it make more sense to have:

Situation 1, where the exhaust fins (green) are perpendicular to the heatsink fins?

or

Situation 2, where the exhaust fins are parallel to the heatsink fins?

Thank you!


texts: How fast does solid waste fall in vertical drain pipes?

texts:
Some building are really tall, if you flush the toilet and the contents go into a pipe and straight down, there could be a lot of energy, potentially enough to cause harm to the sewer pipe at the end of the fall.

I know that in my home, the pipe goes straight down and then there is just a 90 degree bend. According to Wikipedia the calculations for Terminal velocity have a lot of variables, but in essence things that are falling get to top speed quickly.

When solids are falling straight down a drain pipe in a high rise building, how fast do they fall? What is the potential for the things that are falling to damage the pipes and how is this addressed when engineering the structure?


texts: How can I achieve good diffusion from an LED light source?

texts:
I have a light fixture which is designed as three rows of LED light strips. The problem is that the LEDs appear as brilliant points of light. In the fixture I want to diffuse this light so that it appears pure and continuous. The fixture points downwards and is about 6" wide by 24" long.
I have tried frosted glass, but when the LEDs shine through the frosted glass, the individual points of light can still be clearly seen. The light is not continuous and smooth.
I notice that there are LED bulbs that give off an even light, so obviously they use some method to transmute the LED point sources to a continuous shine from the entire bulb, but I do not know how this is done or whether I can imitate it.
What are my options for diffusing the light from the light strip to make a continuous plane of light?


texts: Given a BLDC motor with one shaft, where should I attach my encoder?

texts:
I have recently purchased an ODrive servo controller made for hobby BLDC motors.  Since I had a BLDC motor at home, I did not purchase a dual shaft motor when I got the ODrive.

My question is if I am to use this BDLC motor as a servo, which side should I affix the encoder to, and which side should I affix to the axis I am planning to rotate (the load)?  I have an 8mm shaft on one side and I have a plate with 4 threaded holes on the other side, and need to choose.  I can 3d print anything needed but do not have access to any milling machine or lathe.

Here you can see the two parts of the motor, along with the 8mm shaft on one end.  The "STATOR" is on top.  The "ROTOR" is on the bottom.

Here you see the back side of the motor (the "ROTOR"), and note that the shaft does not extend sufficiently to mount something to it, but that there are 4 threaded holes where something can be fixed.

Here are a couple encoders I have access to (just as FYI, not necessarily the focus of the question).  They are a SICK industrial style and a CUI amt102-v rotary encoder:


texts: Help with simple hydraulic circuit to use for a four legged Robot

texts:
Firstly i am new to hydraulics, i want to build a hydraulic circuit that powers 4 cylinders at each leg of a Quad-Wheeled-Robot. The idea is to move the Chassis of the Robot up and down in all possible ways to avoid obstacles. I did design a system but i am not sure if it has everything i need is there anything that i need to add to it?.

Below is a picture of the simple design using only one actuator cylinder.

It has the following specs:

Dynamic Load:             4000 N bis 6000 N
Motor:                    12V BLDC 1000W (Feedback)
Pump:                     min 80 to max 150 Bar @ 3 to 5 L/min
Tank:                     5 l
Control Valve:            4x Proportional 4/3  Servo-Control Valves (closed Center)
Zylinder:                 Stroke 200mm (Piston/Bore  32mm;
Rod:16mm)
Check Valve and Unloading valve (if i need one)?
Also i have added a Cooling and Filter.

Updated Version all return lines going through Cooler


texts: What are the key properties to consider when choosing a DC electrical motor for linear movement?

texts:
I would like some help defining the specification of my motor, as I have little experience in this field. I've tried researching through Google, but the information is insufficient or unrelated.

The projects involves horizontal movement of a platform with a load of up to 10kg along at a speed of 10mm/sec. As you can see this is a large load and very low speed. The movement has to be pretty smooth. I'm unsure how to specify this when searching for motors (I think it's referred to as jitter). I have yet to decide on the sliding mechanism if it will be using wheels or just gliding on a cylindrical rail, but I'll be trying to minimise the coefficient of friction to reduce the motors force needed.

So I was wondering if anyone can help me identify the key properties of a motor so it provides very smooth movement?  Or if people have experience designing supporting components to the system and why I should focus on that aspect instead of the motor.


texts:
I actually don't know on which SE to ask this.

Since there are quite often too low bridges/tunnels, or too high trucks or trailers, why isn't there 100m ahead of those bridges, some light frames (like football goal cage) the size and height of the entrance, which isn't dramatic to destroy, allowing driver to know they won't go through, and giving them time to brake before causing damage to both tunnel/bridge, truck,... ? Or are there already?


texts: Copper is more conductive, so why use lead battery terminals?

texts: Copper is around 14 times more conductive than lead according to this source. If this is the case why are car battery terminals and connectors built using Lead? I saw both types of replacement connectors at the automotive store and am interested in the advantages of each? Thanks for any information.


texts: A question on how heat treatment is done in bogies

texts: During heat treatment of metals I find that Normalizing is done in railway bogies and tempering is done following normalizing only for the CP top and bottom. Following the tempering process quenching takes place for manganese steel. I am basically very new to the wagon industry. Hence a slightly detailed explanation about the same is very much sought out for. It would be great if someone gives me a detailed insight into these from an industry perspective.


texts:
I have encountered a type of unit that I cannot understand. The unit describes the rate of permeation through a substance:(cm^3 . mm)/m^2 . d . atm

Could someone please explain how to interpret these units? Please attempt to leave the answer in simple - to - understand terms as chemistry, not engineering, is my primary field.


texts: Efficiency of water distillation vs active Condensation Trap

texts:
I was wondering what would be more efficient means of producing clean water. The first method could be though a distillation process where by you boil contaminated water and collect the water vapor (similar to "sling shot" water purifier), the next method would be to cool plates and collect the condensation.

The first method would require you to head up a lot of water just to cool it back down again, but the second method is possible highly inefficient as you are cooling a lot of air just o get a small amount of water vapour to condensate. Any one know of any calculations or studies that have addressed this question?


texts: I saw a machine that fed a sheet of laminate through some rollers.  The motor had a pulley attached to its shaft, and a spring connected to the pulley.  Why not use a belt?  Wouldnt the spring make it too difficult to know the exact position of the load on the other side of the spring?


texts: What is the starting/stopping sequence of a traffic light

texts:
As is probably known a traffic light may be turned off in which case normal rules applies to the intersection.

While the traffic light is active then red & red+yellow means that drivers are required to stop, while green means that the drivers are allowed to drive. Yellow also means that you're allowed to drive, but cautions the driver that it will/may turn red on which the driver are required to stop.

Now by what sequence do one start/stop the traffic lights? Stopping seem quite obvious, just make sure that all are showing red (or only those that will have the right of way have green) and then just turn off the light.

But how to turn the lights on again. I think that just reversing the sequence may not be fair - if the light all the suddenly turns red you're required to stop (but may or may not have the time to stop your vehicle). On the other hand entering with green light might be dangerous.


texts: Creating Planes of Bubbles in Polymer Samples

texts:
My lab and I are looking to conduct tensile test experiments on polymer samples with integrated planes of bubbles or voids (see image). The goal of this is to see how well we can manipulate crack propagation during tensile testing with the induced bubbles by varying the angle this plane makes with the predicted crack plane.

Preparing the currently tested polymer (Ecoflex) involves mixing two liquid components together, pouring the mixture into a petri dish, putting the dish in a vacuum chamber to remove bubbles, and setting the dish out on a level surface to cure for several hours.

Our current ideas on creating this integrated bubble plane:

manually inputting bubbles in a curing solution on a petri dish using a syringe
creating a layer of polymer which we let cure without placing in a vacuum chamber. Once cured, pour another layer of uncured liquid polymer on one side of the cured (non-vacuumed) polymer, place the combined polymer in the vacuum chamber to remove bubbles from the uncured part, and allow to cure. Repeat process for the other side of the non-vacuumed part

Samples are cut from the cured polymers to achieve tensile specimens with desired orientations of the bubble plane and the initial crack is created by cutting the specimen with a razor blade.

We are still experimenting with these processes and are looking for other ideas as well. Any input on how to create this bubble/void plane would be appreciated.


texts: Do wave washers need to be on either end of bearings in double bearing induction motor

texts:
I have a typical small electric induction motor given to me in pieces.
It has two wave washers which I am told should sit between the bearing and the assembly.

I am not sure which bearing needs the wave washers.

Do I place on one wave washer before the front and rear bearings ?
Both wave washers on the rear bearing?
Both wave washers on the front bearing?

Please advise.


texts:
Adaptive suspensions with adjustment rates on the order of milliseconds are going mainstream in consumer vehicles.  Air suspensions have been common on commercial trucks and some SUVs for some time.

Why are pneumatic tires necessary or helpful on vehicles equipped with such suspensions?

I understand why a wearable tire is necessary: the friction coating on the wheels does need to be replaced.  Recent years have seen a proliferation of very low-profile tires for road vehicles, but to my knowledge they are still always pneumatic.  Why?  The downsides to inflatable tires are that they perform poorly when improperly inflated and are subject to failure, including catastrophic decompression.  What are their upsides?  For example, do they provide damping responses that can't be replicated with an air or adaptive suspension?


texts:
I am emulating a throttle handle from a locomotive. See the diagram below for what I am trying to create.

Its a throttle handle with 9 'positions' or notches (0-8 power).

The handle will probably pivot on the potentiometer.

I need some ideas on how to create mechanical notches, so it clicks into each throttle position or the user knows when they change to a different position. I cannot find much inspiration on the web, as other similar systems seem 'sealed'


texts: Please explain the meaning of this statement with close reference to Precipitation hardening,"The relative rates of nucleation and growth are controlled by temperature. The size and dispersion of the secondary phase is controlled by time, with coarsening occurring as time proceeds."What I do not understand is the difference between the usage of "growth" and "size" as different parameters. They say they are dependent on temperature and time respectively.Arent they basically the two sides of the same coin.Please explain me with close reference the the precipitation hardening in Al-4.5wt%Cu alloy.


texts: How can I save mass, inertia, joint location and part orientation data from any 3D-CAD program to a CAD file?

texts:
I would like to be able to save, for example, a SOLIDWORKS(or any 3D-CAD program) assembly in some format that includes all the joint local/global locations and the parts global location and orientation. Is there standard file format for that?

Second question is there a CAD file format that includes mass and inertia data with graphics?


texts: How to get a brighter, sharper image from a projector lens

texts:
I  am trying to make a homemade projector using my phone. Screen size 5.5 inches, focal length of lens is 20 cm, diameter of lens is 6 cm. The problems I am facing are:

the edges are distorted;
the brightness is too low.

The farther I move my phone away from the lens, the lesser the distortions but this also results in less light passing through the lens, so the brightness decreases.

Using stops to remove spherical aberration is an option but that will reduce the brightness of image. I want to preserve the little light that my phone can emit. How can I minimize these problems?


texts: Is it OK for a 2 story house not have a column or pillar

texts:
sorry for my english. I was looking to buy a house. I saw some in my hometown, which is very affordable.
but on a picture of the house they are selling I found on the net troubled me.
no pillar/column, just hollowblocks and some steel bars.
kindly look at the pic.

I found it in this site
https://fiestacommunitiesblog.wordpress.com/tag/fiesta-communities/