texts: Estimating the time required to heat a rod by a certain $\Delta T$

texts:
Consider 1D heat conduction on a rod of length L.  Assume the rod has a known density $\rho$, specific heat $c_p$ , and thermal conductivity $k$, all of which are constant with respect to temperature. Suppose that the initial temperature of the rod is constant $T_0$.  I want apply a constant heat flux $Q$ to the rod at one end, with the goal of heating this end of the rod to a desired temperature $T_{desired}$.  Assume the other end of the rod has an insulated (zero heat flux) boundary condition.

Without explicitly solving the heat equation $\rho c_pu_t=ku_{xx}$, is there a simpler formula I can use to estimate how much time it takes for the heated end of the rod to rise by a a factor of $\Delta T = T_{desired}-T_0$?  Is there a formula that only requires knowing $Q,\Delta T, L,\rho, c_p,$ and $k$ to estimate this time?


texts:
I cannot seem to be able to find which unit applies to the integral of torque over time. If you compress a bracket shaped load cell, you exercise torque on it, say 5 Nm.
Now, say you do this for 5 seconds, by integrating it you get an area of 25 .. Nms? which would be... angular impulse? can I also represent this as watts or other units of power?
Thank you!
Edit:
This shows a use case, where the load cell's angle is increased as the leg expands. We can determine the torque of the knee's angular movement. So, measuring this as a function of time, it only give you an angular impulse, but no way to determine power from this, is this correct?


texts: Calculating the Surface Temperature of a Cable with known heat flow

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I have a cable which dissipates $\dot Q_{total}$ and I need to determine the surface temperature  of the insulation $T_{ins}$ and the surface temperature of the conductor $T_{cond}$.

There is an insulating layer with the thermal resistance $R_{cond}$ and the convective thermal resistance $R_{conv}$. The radiation component is neglected. From the geometry of the insulating layer I can obtain $R_{cond}$, but for $R_{conv}$ I need to calculate the convection coefficient via the Nusselt-number. I have an empirical equation for the Nusselt-number, but the Rayleigh-number calculation requires the value of $T_{ins} - T_{ambient,air}$.

So I have the following equation:

$\dot Q_{total} = (1/R_{total}) \cdot (T_{cond} - T_{ambient,air})$

with $R_{total} = R_{cond} + R_{conv} = R_{cond} + Nu \cdot \lambda/L$.

Where $\lambda$ is the thermal conductivity and $L$ the length of the cable. There are two unknown values in this equation $T_{cond}$ and $T_{ins}$, because $Nu$ depends on $T_{ins}$ and $\dot Q_{total}$ depends on $T_{cond}$. Is there a way to calculate the temperatures or do I have to define a temperature?

Furthermore I cannot determine the film temperature because  $T_{ins}$ is unknown. At which temperature should I determine the thermodynamic properties for the Rayleigh- and Prandtl-number calculation?

Summary:
Known: heat flow $\dot Q_{total}$, $R_{conv}$ (because geometry is known), $T_{ambient,air}$ Unknown: $T_{ins}$, $T_{cond}$, film temperature $T_{f}$ and therefore also the exact values of Rayleigh, Prandtl and Nusselt-number.

I want the thermal resistance of convection to be as accurate as possible, that is why I wanted to calculate it with these dimensionless quantities


texts: Material which can be used for resistive heating and simultaneous temperature measurement

texts:
I want to embed a wire inside a plastic and heat it to specific temperatures (80$^\circ$C 100$^\circ$C 130$^\circ$C 180$^\circ$C). I want to find a material that is resistive enough for resistive heating, but also I want the wire's resistivity to vary fairly strongly with temperature - this way I can know the actual temperature that I'm getting by looking at the resistance during the heating process.

My problem is that I cannot seem to find a material with the properties I want. I tried nichrome wire and carbon fibers, and while they are resistive enough to give me heat, their resistance does not change enough (for my desired temperature ranges) to be measurable with my setup.


texts: What mechanical design will shake a gravel screen box back and forth not up and down

texts:
Looked at this gravel screen and its a different design wondering how the shaker box moves sideways directly connected to the small gas engine,
How or what mechanical connection would be involved?
https://youtu.be/BG8YXpPKhLU?t=36


texts: Is it possible to use a laser push a 100 micron diameter droplet of water through a fine mesh?

texts:
Context

I've had the thought of a printing device that uses a thin grid that has holes small enough to allow suspension of a water based ink above a sheet of paper using surface tension. I've concepted how such a device would be used to form an image, but not sure on the basic concept of use of a laser to apply a force.

Attempts at answering this myself

My initial research has revealed the following:

Lasers can be used to apply a significant force on a micro scale and below
Water can be suspended using its own surface tension

The missing information

I have no idea as to what calculations I would need to run. Using the some of the basic formulas I've seen applied in other similar applications are wildly varying and I could never join them together to make any sense. I also I am missing something not from a scientific perspective, but a engineering perspective.

The question

Is it feasible to use a low powered laser to "push" the ink though the gaps?

I am assuming the target area is approx 1000 square microns. However this fact is adjustable as I am not targeting any specific quality of print.


texts: "Micro Inverters" vs "Pure Sine Wave" for Solar Systems

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Regarding micro inverters for solar power systems:

Is there technically a difference between an inverter classified as a "micro inverter" and and inverter classified as a "pure sine wave" inverter?  Or is it simply a matter of using extra jargon to describe the size of the inverter?

Problem I'm trying to solve:

I'd like to purchase a micro inverter based solar system, where each panel has it's own dedicated inverter.  Enphase seems to have coined the term "micro inverter" for this purpose, but the reseller doesn't offer a micro inverter that is big enough for a 315 watt panel.

So I'm wondering if I can purchase a pure sine wave inverter rated at 400 watts, for each 315 watt panel.  Would those wire up the same way as the "micro inverter" solution?


texts:
I'm looking to implement a simple regenerative braking circuit in order to measure how much energy could be regenerated using a DC motor. My knowledge of electronics is very basic to say the least so I was looking for a bit of help.

I'm looking to power the motor until it reaches it maximum velocity. I'll measure the input voltage and current using a daq device across the resistor R2 in the diagram In order to energy the input power and energy.

Then using a double pole double throw switch i'm going to connect the motor to these capacitors to store the generated emf from the motor whilst measuring the generated voltage and current across R2.

Would this work? Apologies if this problem is of a trivial nature for this forum, like I said, my knowledge of electronics is pretty basic.


texts: What does "beam end release" actually mean, and how it is modeled in mathematical terms?

texts:
I am reading a document about beam end release here:

  An end release will allow either or both ends of a beam element to
  rotate about or translate along one or more of the local axes of the
  beam.

And the article continues with the following diagram:

(a) Fixed-fixed beam with a hinge point at 1 and 2.

(b) The theoretical rotation or slope of the beams. Note how the result is discontinuous at the hinge points.

The understanding I get from the above is that if we release at a beam end, then it will become hinge ( and hence the rotation at the end is not continuous)-- and that's it. Is it true?

If this is true, then I don't understand the moment released term in RISA software:

I am not even sure whether the beam end release and the moment end release are connected, and if yes, how.

How are the beam end release and moment end release modeled mathematically?


texts: How to prevent an object doing a full rotation on a shaft

texts: I basically need a block on a shaft to rotate between 90 degrees (vertical) and approximately 180 degrees (horizontal) counterclockwise on a shaft. I don't want the part to fall below 180 degrees. At 90 degrees it will clip into a stand so clockwise rotation does not need a part preventing rotation. Please advise on a way to prevent clockwise rotation after a certain angle. Thanks :)


texts: How to determine motor needed for water pump

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I can't find what i'm looking for in the engineering stack exchange because it's all way over my head.  need basic help answer the basics to get started. so maybe a link or video that helps me understand how to even ask the right question on motor needed. I'm not going to become an engineer or learn everything i simply want to understand how to solve one type of problem.

so here's my basic need:

I have a water pump bought at a store that needs to be driven by a drill. But i want to use a motor from another appliance to run the water pump so i can use my drill for other things and have the motor that runs the water pump just working on that.  I took apart a spice/ coffee grinder and rewired it and hooked it up the water pump and its simply doesn't move from lack of power ( it works fine and spins fine not attached to the water pump).  So how do i calculate the motor i need to run the water pump?

also i will need this calculation to serve other projects... I'm also going to want to make a yeast stirer and use the motor from an orange juicer to spin a magnet that will affect a stirer stick through a glass container to stir yeast for 24- 48 hours.  Not a lot of power needed but will needed to run all day and night.

so I want to understand just the very basics i need to determine how to choose a motor or how to very simply adjust or reconfigure any  motor set up (i.e. use cogs or some kind of added system of wheels to increase the motors power) to:
1) be able to run a water pump or spin anything that requires a lot of strength and can run continuously for an hour to two hours.
2) Secondly, I need to calculate and determine needs to run a motor that spins a light load but continuously for 48-72 hours without burning out.

I cant find answers on google or stack exchange because when i ask the question i get a ton of irrelevant or very complex answers. i'd like help in getting enough info to keep my projects going without having to study engineering for weeks.  i dont need to understand every single thing but enough to get these jobs done and repeat the process for similar future projects.  Thank you!


texts: Is there a way to determine the colour information of light emitted from an LED?

texts: Say you have an LED light that emits green light. Are there sensors out there that could accurately determine the colour information of the green light? Such as the relative values of red, blue and green light being emitted from the LED.


texts: What are these bent shapes on this elbow in a compressor suction pipe?

texts:
See here are the shapes which are made on the suction head of compressor,

What are these, and why are they on the suction head pipe?


texts: Mass flow rate (air and steam) through a cylindrical pipe

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I would like to determine the massflow rate of (a) steam (b) air flowing through a cylindrical pipe knowing that p_inlet = 5 bars p_outlet = 1 bar. Internal diameter is 0.5m. Length is 30m.

Surface roughness is assumed equal to 5E-05 m. Only steady state situation is necessary. Temperature at the inlet is assumed in both cases to be equal to 150°C. For derivation, one can assume adiabatic flow.

What would be the steps to determine the massflow rate ?
I assume one must first check whether the flow is compressible or not ? Then whether the flow is subsonic, sonic, supersonic ? Then also if laminar or turbulent ?
And then eventually, what would be the equation to be used to determine the massflow rate ?


texts: What does it mean by "loops and troughs"?

texts:
Actually, I've asked this question in "English Language & Usage" but someone told me ask it here!

What does it mean by "loops and troughs" in:
"Source has acquired a pattern of loops and troughs."

Here's some context including this phrase: https://books.google.com/books?id=a6LzCAAAQBAJ&pg=PA482&lpg=PA482&dq=%22loops+and+troughs%22&source=bl&ots=0M9eK7xYHc&sig=afrE7rVYxX8Zxda7_L7NDGYWzYA&hl=en&sa=X&ved=0ahUKEwjhk4Cqz8HZAhUKZ1AKHSFnBsEQ6AEIKzAB#v=onepage&q=%22loops%20and%20troughs%22&f=false


texts: External Static Pressure on Open Gallery Fan

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I routinely work on building designs that incorporate rooftop upblast fans over large industrial spaces such as this one:

When selecting these fans, as with every other fan, you need to determine the external static pressure that the fan will encounter.  I have heard opinions ranging from "negligible" to 0.15" of static pressure up to 1" without any technical basis to back the responses up.  Generally, they are exhausting a space at a slightly higher rate than the space is being supplied air in order to negatively pressurize the area relative to adjacent spaces, with an intent of maintaining 0.1" of static pressure.
What guidelines/calculations are available to allow the external static pressure for this fan configuration to be calculated?


texts: Vibration damping a bed from mechanical vibrations

texts:
Note: I understand the very nature of this question is about gross approximations on an incredibly complex topic, but even educated 'guesstimates' would be very helpful
I have already seen these two questions but i'm hoping with some provided data I can get some better insight.
I am experiencing constant mechanical vibrations in my bedroom from an unknown source somewhere in the building. They only last for 20-30mins then stop, but are an issue at night. It is the vibrations and not an actual noise causing issue. I am using vibration dampeners under my bed. I have tried 5 different products, with varying success. The current ones I am using seem to be 'styrene butadiene rubber' (medium hardness) with 'EVA polymetric foam' material' sandwiched between. Out of all the products so far, they are the softest and seem to have the best damping, although it is not enough.
However, I believe that all the products I am trying are still too hard for the frequency of the vibrations.
This idea is making me explore purchasing sorbothane disks (part numbers 0510435-30-10 or 0532350-50-10) with a 'duro' of either 30 (softer) or 50 (harder). I have found these spg and edg PDF files which show vibration damping calculations.
I am not an engineer and unfortunately I do not know the Hz of the vibrations I am experiencing. However, I can say it is akin to a washing machine near the end of a wash cycle on fast spin dry rather than a rumbling train.
The bed including myself and my partner weighs ~180 / ~200kg. The bed does not have four posts but a solid headboard and footboard which both reach the ground. This allows me to place more than 4 anti vibration pads rather than just one at each corner.
I am deciding between the two disks below (Imperial units listed);
0.25" Thickness x 2.25" Diameter (Duro 30, softer) 40lbs - 90lbs Load
6 Disks would give a max load of 244Kg (6 * (90 / 2.205))
0.50" Thickness x 2.25" Diameter (Duro 50, harder) 40lbs - 85lbs Load
6 Disks would give a max load of 231Kg (6 * (85 / 2.205))
So my main question; is a softer but thinner material better suited to absorbing high frequency vibrations than a thicker but slightly harder material?
From this answer, it implies that softer is better, but there is no mention of thickness.
And a bonus question;
Is it generally better to try 4 points of contact rather than 6? (thinner and harder, but two less points of contact) or should i actually try to increase the points of contact in order to use a softer material to dampen the vibrations?

EDIT: I have a response from one of the product development engineers from sorbothane who advises to go for a thicker part since thicker parts will have lower natural frequencies.
As to not waste the question, perhaps someone can answer why that is in either basic or technical terms.


texts:
I have encounter this notion: "Dimensionless Thickness". Does anyone have any idea how to interpret this? One can find such a term here.

My interpretation is that the name comes from the fact that the thickness alone doesn't mean too much, but it means a lot if it is related to a reference number (e.g. $ratio = t/t_{reference}$, where t is the dimensionless thickness).

If this is true, can anyone provide me with an example of such a term in the fluid-dynamics, mechanics or thermodynamics field?


texts:
I have an 4x4 which I have heavily modified, the only thing missing is mechanical differential locks. I think it wouldn't be too hard to fit a four channel abs pump from another vehicle and produce my own controller. Which would give me more or less the same ability as diff locks plus a few more features without the hefty price tag.
Features I intend to have are.

Individually locking a wheel on demand (just like fiddle brakes at the touch of a button for all 4 wheels)
Two potentiometers for automatic control of the amount of slip to allow between left and right wheels.
Automatic air stop. For detecting front wheel air (on jumps etc)to slow them to a min speed when we detect a run away difference between front and rear.(this will stop breakage of front drive components when they hit the ground).

I plan to monitor wheel speed with 4 hall effect sensors and abs rings fitted to each wheel. The control unit will be an arduino and will count pulses on interrupt.

The electronics and programming side of things I am quite proficient at.
The hydraulic side of things no so much.

I understand that these abs pumps have 4 channels and two feeds usually labelled mc1 mc2, I assume one for front and one for rear from the master cylinder.
each channel is controlled by a three way valve. This is where my knowledge runs out.

My question then is how are these valves usually controlled in terms of positions and electrical connection?

Whats the maximum / typical frequency these valves actuate at or is it variable depending on rotational speed?


texts: Is it possible to fire a ball of water that holds its shape?

texts:
Background
I participate every year in a huge water balloon battle. The clash happens between two universities so you can imagine that the commitment, at least for some people, is quite high. To give you an idea last year some 40000 (thats 40e3) water baloons were thrown, plus there were some home made war machines, namely a catapult, a trebuchet, some arquebuses running on compressed air and such. Safety is of course the primary concern and nothing more than water/water balloons has ever been thrown.
Actual Question
I want to build a water cannon and I would love some advice/ideas. What do I mean by water cannon? I mean a machine capable of throwing a lot of water, from 1 to 3 litres, at some 20 metres at least, in a shape like a cannonball rather than a stream.
Is it possible for a "blob" of water to maintain its shape after being shot in the air at some speed, at least for a limited range? I see two challenges: accelerating the water and "keeping it together" while in the air. The latter can be achieved with a plastic container (such as a balloon), while the first part may be trickier. Balloons tend to rip and explode if accelerated too much, while leaving the balloon out may make the second challenge impossible.
The design I am considering could have a huge tank connected to a smaller one that serves as the "firing chamber." You fill the firing chamber, then close the line between the tank and the firing chamber, then you open another line that launches the water out through a barrel. The idea is to use compressed air but my main concern is that the water will not maintain a "ball" form while in the air.
Constraints
The best solution for me would be one that works within the constraints for the water balloon battle.

About 100 € material cost.
No fire is allowed in the propulsion system, compressed air is fine but no electric compressor is allowed so efficiency is a must. Our arquebus could fire a lemon sized balloon some 50 m away on about 2 atm.
Safety is absolutely the primary concern. For no reason at all there can be risks for the operators or the opponents. We experimented with a firing shell with our arquebus because friction with the barrel would destroy the balloon, and the shell was secured to the barrel with many redundant wires to be sure not to fire it too.

Workforce and time are pretty unlimited if the project is cool. We have some very high manual skills and quite a lot of common and not so common tools.


texts: Is a motor failure caused by a defect bearing considered to be a failure mode or is it higher vibration and speed loss in FMEA/FMECA?

texts:
Let us assume we have a motor with a bearing which is exhibited to wear. Over time, we can observe higher vibration, increased noise and the motor speed reduces due to the bearing fault. In the end, the bearing fails and the motor is not able to provide its specified function (drive something) anymore (called failure).

My Issue: I am not sure what would be the right name of the failure mode in this case. I found a lot of sources that call this the "bearing failure mode". However, according to ISO Condition Monitoring 13372:2012 a failure mode is the "observable manifestation of a fault". So, I think in this case observable are the loss of speed, increased noise and the higher vibrations and I would call my failure mode: "higher vibratons, increased noise and speed loss". In this case, "bearing failure" would be the name of the failure cause. Furthermore, there are other causes that result in the same observalbe properties and so one failure mode can have several root causes, right?

What is right and why? I do not want to over complicate this, but I need some clearity here. It is also interesting regarding FMECA. This is a "Failure mode effects and criticality analysis" in which the concept of a potential failure mode plays a big role. Is there a good and reliable source (literature) with examples how to differentiate what a failure mode is? What is the best practice?


texts: What diameter aluminum pole do I need to lift 100 lbs vertically?

texts: I am wanting to use an aluminum pole (as a Jin Pole) to lift the mast on my sailboat into place.  My mast is about 30 ft. long and weighs between 80 – 100 lbs.  The aluminum pole would be stood upright and attached to fore and lateral stays to hold it in place vertically.  It would be fitted with a pulley near the top end with a line running down and tied around the mast (near its middle) for lifting.  The other end of the line (free end) would be run downward from the pulley thus lifting upward on the mast when pulled down.  The mast would be lifted up until high enough to set it in the mast holder at its base (about 18 ft up where the lifting line is attached to the mast).  My question is how large (diameter) aluminum pipe/tube would I need to lift the 100 lb. mast vertically if I used 3/16 in. wall thickness for the aluminum pole? (Assume it will be 6061 T6 strength aluminum).  The pole will need to be an overall length of about 19 ft. if this matters.  Distance between the lifting pulley and where the line is attached to the mast to start the lift will be about 18 ft.


texts:
In the old days there was a type of sign/light you would find in bars and restaurants which was animated.

It would be a lit scene usually of water, like a lake with a waterfall, and by some means it would animate and look like the water was flowing.

They would be used to advertise cigarettes or beer.

What was this technology called? How did it work?


texts: Magnetohydrodynamics, ionizing combustion exhaust then converting its kinetic energy to electricity

texts:
I am trying to understand how to make generation of electrical power more efficient by using Faraday's law to directly convert the kinetic energy of the ionized or easily ionizable exhaust gases of combustion (oxidation of hydrocarbons or to make things simpler just hydrogen) into electrical energy.  In this system, the only real moving parts would be the motion of the ionized or plasma exhaust gas medium through the surrounding faraday coils. We may need a fan to coax the pre-combustion gases in a linear flow. The usable current would be induced in the Faraday coils from the accelerating or decelerating ionized gas from the exhaust.

My main question is how to completely ionize the exhaust gases at the point of combustion.  My understanding is that these are already ionized at the instant of combustion but rapidly de-ionize when the oxidation reduction process is complete.


texts: Periscope camera with a mobile phone, how to make walls not visible on the camera/alternative solution?

texts:
I am trying to make like a "periscope" that i can use with a mobile camera.
I have made a very quick prototype with two mirrors and it "works" but you can see the interior of the walls so it is not a good solution. It currently looks like this

So as I said the problem is that you can see the "walls" on the interior of the periscope when i put the camera in there.
Is there anyway I can adjust this or do I need to look at an optional solution?

What i want to achieve is to make the backcamera of the phone to be like a frontcamera and have it under the camera that is vertical. (just like my current model). Can I somehow adjust the periscope (build it better, add more mirrors, maybe add a magnifying glass?) or do I need to build something else completely in order to make it work flawlessly without interior walls etc being in the way making the quality bad.

Any tips, tricks, links is very much appreciated!


texts: Drucker-Prager Model Parameters, a Proper Choice

texts:
My task is to write a code from scratch for 3D elastoplasticity, namely a DP model (see for example DeSouza Neto, et al., 2008, Chapter 8) having yield surface

$$ f(\mathbf{\sigma},c) = \sqrt{J_2(\mathbf{s(\mathbf{\sigma})})} + \eta\,p(\mathbf{\sigma}) - \xi \, c(\bar{\epsilon}^p) $$

being

the first term the square root of the second invariant of the stress tensor;
$\eta$ and $\xi$ are chosen according to the Mohr-Coulomb surface that one approximates, which in turn depend upon
the friction angle $\phi$ and dilatancy angle $\psi$, this latter used since the flow rule is not assumed to be associative, so another parameter $\bar{\eta}$ is computed
$c$ is the cohesion, which in my linear assumed model depends on the cumulated plastic strain $\bar{\epsilon}^p$. The linear functional form this one takes is $c(\bar{\epsilon}^p) = c_0 + H \, \bar{\epsilon}^p$

My question is: I know how to implement the numerical integration algorithm to solve the (rate independent) rate equations, but I couldn't find a set of parameters $G$, $K$ (shear and bulk modulus respectively, or in alternative $E$ and $\nu$, Young and Poisson moduli), $\xi$ and $\eta$ or equivalently $\phi$ and $\psi$ and lastly $c_0$ and $H$, initial cohesion and plastic modulus.

I would like to ask for some references where such parameters are available, say for granular media. This task is developing oriented, it is just intended to implement an elastoplastic constitutive model, I only need some physically plausible parameters.

Reference: E. A. de Souza Neto D. Perić D. R. J. Owen, Computational Methods for Plasticity: Theory and Applications, 2008 John Wiley & Sons, Ltd.


texts: Planes, lines and distances: looking for engineering problems

texts:
In a week from now, I am going to teach a one-time class to first-year engineering students about 3D geometry, more specifically: distances between points and lines/planes, and the common perpendicular between two skew lines.

Are there any cool engineering use cases (construction, chemistry, physics, computer science...) that I can use to illustrate some of these mathematical problems? I have looked a while on the internet, but cannot seem to find any good ones. And all textbooks I have consulted stay on the mathematical side of the spectrum, without applications.

Thanks!


texts:
There are two components given with each stress-strain curve.
Determine the component that maximise the load carrying capacity and that maximise the elastic deformation per unit applied load.

Is it right for the maximum load carrying capacity to look for the highest yield stress and for the maximum elastic deformation per unit applied load to look for the highest strain at failure?


texts: How to incorporate moment release at beam end in FEM formulation?

texts:
I have a structure with a lot of interconnecting column and beam frame elements. I want to compute the displacement, member forces/moments via Finite Element Method.

The problem now is that I don't know how to properly incorporate moment release at beam end. I understand that moment release means that at the beam's end, the bending moment is $0$, but I don't know how I can incorporate this piece of information ( as a boundary condition? Or as a form of penalty function, or...?) into my FEM model.

I know how to incorporate support into my FEM model though; I can just make the relevant appropriate stiffness terms very big. But not moment release.

Any idea how moment release can be formulated in finite element terms to achieve the desired end results?

Note:

This question is different from the one that I asked here, because that one asked about mathematical formulation ( more on conceptual level), whereas this one asks about explicit FEM formulation. These two maybe related, but to go from previous question to this one is by no means trivial, and the connection not easy to see.


texts: AutoCAD Boundary Trim with Multiple Boundaries?

texts:
So for a particular task I need to trim and remove cells from a boundary with an action macro I can accomplish this fairly simply using the following procedure.

Create unit cell (closed polylines)
Copy unit cell Change layer to temporary layer

Prevents deleting original unit cell or other completed boundaries

Create a rectangular array from the cell

Large enough to encompass the chosen boundary

Move array to boundary location
Explode rectangular array
Run a boundary trim (outside) using boundary to remove only temporary layer
Select open polylines to isolate partially trimmed cells
Delete partially trimmed cells to ensure only complete cells are allowed
Change objects back to original layer
Repeat for other boundaries (sometimes upwards of 20)

So the process is fairly straightforward but time consuming-mostly because I am unable to select multiple boundaries to apply a boundary trim. If I could select multiple boundaries I would be able to skip the layer manipulations, copy/move operations, and multiple boundary trim/select/delete operations as well. The process is depicted visually below:

I still need the objects to be countable (using a count by layer command or something similar) so I don't believe any sort of Hatch command will suit my needs but I am open to any and all suggestions to improve this task efficiency!

Thanks!


texts:
I am working on a 500 kg roller, which I want to pull using electric motor. I am considering hub motor, since it is easier to frame a basic ev with it. Now I need to know the capacity of the hub motor, I need to choose.

Roller weight = 500 kg
Frame weight + driver weight = 150 kg
speed required = 10 km/hr
Surface on which the roller is to run is predominantly flat.

Things I need to know,
 1. Torque requirement for my problem.
 2. motor wattage
 3. battery requirement, to run for 2 hours.

Being new to such design projects, I may have missed details. Please ask me for them. Help me with the calculation.


texts: Would an orthotropic cylinder subjected to torsion have warping?

texts: The situation I'm imagining is the one shown above, which is the cross section of a cylinder made of alternating layers of material. The material axes are shown where 1 and 2 are in the same plane and 3 is parallel to the stacking direction. If a cylinder composed of this material is subjected to a torque around its central axis as shown, would it be subject to axial stresses and therefore result in torsional warping? I read here and in textbooks that circular members don't have torsional warping but they are usually assumed to be made of isotropic materials. Would this be the case for this type of cylinder too?


texts:
The NSPE stresses the importance of licensing and makes several points about the seal being important.

  Only a licensed engineer may prepare, sign and seal, and submit engineering plans and drawings to a public authority for approval, or seal engineering work for public and private clients.

  https://www.nspe.org/resources/licensure/what-pe

  Only a licensed engineer, for instance, may prepare, sign, seal and submit engineering plans and drawings to an public authority for approval, or to seal engineering work for public and private clients.

  ...

  Only PEs can sign and seal engineering drawings;

  https://www.nspe.org/resources/licensure/why-get-licensed

However, I'm having trouble understanding specifically when a seal is required and who or what enforces necessary use of the seal. Is there a general approach for this across any given discipline or project?

I could imagine these sources of "rules" for using a seal.

Regulation
Legislation
Insurance requirements
Other contractual obligations

If the question is too broad and needs to be narrowed, here's an example...

I worked on an FDA regulated Class III medical device. I read the relevant titles/sections of the CFR and do not recall any mention of using the PE seal. I do not recall any of our hardware design documents or outputs being sealed. I worked on the device control software and I know that none of our software designs, design controls, or outputs were sealed.


texts: Shift of joint in kinematically indeterminate system

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Given ist the following system:

$$EI=100000\frac{\text{kN}}{\text{m}^2}$$
$$EA\to \infty$$

I'm suppossed to find the horizontal and vertical shift of joint g. My first approach was to use the principle of virtual work using $$f_i=\int_0^l\frac{M\bar{M}}{EI}dx$$. (As per syllabus, shear forces can be neglected.) In order to determine the moments I need to figure out the reaction forces. However, the system is kinematically indeterminate, despite being statically deteminate.

This can easily be seen by determining the moments around the respective bearings in each system:
$$1: G_x+G_y+24=0$$
$$2: G_x + G_y + 48=0$$

Alternatively, it can be seen that there are no conflicting moment poles.

My next approach was the principle of virtual shifts, which (unfortunately as expected) led to the same equations as above.

What is the correct way to approach this problem? Any help would be appreciated!

In case someone wants to know the solution:

$$\delta_x = 29.97\cdot10^{-3}\text{m}$$
$$\delta_y = 7.29\cdot10^{-3}\text{m}$$
$$\delta_{\text{ges}}=30.84\cdot 10^{-3}\text{m}$$


texts:
Is there a software that exists that takes a macro object for example a MacBook casing and its composition (Aluminum) and allow you to zoom between the macro scale (a fully rendered MacBook) and the atomic scale (a view of the atomic structure).

I've played around with VMD, PyMol, ASE, CAD. The first 3 are focused on the molecular level, but CAD is for designing macro scale objects. Can't seem to find a combination of both


texts: How to calculate filament deflection and force applied to teeth by toothbrush bristles?

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I am trying to get my head around the behaviour and the effectivity of the the filaments movement of a toothbrush inside your mouth. I want to know the mechanical formulas and/or properties that I need to consider in order to understand how the filament moves and bends.

The ultimate goal is to know how much it will move and bend over the time and the relation of the parameters.


texts: How do I call a kinematic assembly that converts rotary motion to sawtooth linear?

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I have in mind a device somewhere in between a firearms trigger and a clock escapement. One way it could be constructed is as follows:

A crank would displace a linearly moving slider backwards, so that it compresses a spring.
Eventually the crank would let the slider slip, so that the spring shoots it forward, where it could again be caught by the crank on its next turn.

However, this description is not essential to my question. I simply wish to deliver the idea to the reader, all because I do not have a name for it.

It is this name that I am seeking, so that I can further look it up, to hopefully find, study and re-use previously developed constructions of this kind.


texts: What is the best way to control brightness of a LED?

texts: LED brightness can be controlled using digitally controlled potentiometer such as a Microchip MCP413X or a PWM signal. In both cases the signal will be controlled/ generated from a micro-controller. Which method is better using a digitally controlled potentiometer or PWM signal? Why?


texts: Must I use viscoplastic model to fit the thermoplastic material

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I need to do the simulation with a specified material. It is known as a thermoplastic.
During the simulation, I need to define the material property.
I need to choose whether it is viscoplastic or viscoelasticity model.
I'm wondering whether the problem I want to model is truly visco-plastic (as it is thermoplastic material)
Or I can choose a viscoelastic model with considering the permanent deformation after sufficient relaxation time?


texts: How can I cut a thin (1mm) sheet of stainless steel with high precision?

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I have a circular puck of stainless steel that is 9.5 mm in diameter.  In the center, there is already a 5 um pinhole.  My objective is to basically cut the steel along the dotted line, approximately 0.5 mm from the pinhole.  Can you advise on what techniques to can make this cut precisely?

The reason I want to do this is to be able to align two of these so that I can have 2 pinholes that are ~1 mm apart from one another, as in the following image.


texts: Pressure coefficient over a cylinder without using potential flow equations

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I'm new to this site so I apologize if I'm asking a previously answered question, but I couldn't find anything anywhere. I was trying to derive the pressure coefficient over a cylinder without using inviscid potential flow derivations. So for the usual potential flow equations, we obtain, for flow on the surface of the cylinder,

at $r = R, V_{\theta} = -U(1+R^2/r^2)\sin \theta = -2U\sin \theta$

where U is the free flow velocity. After plugging into Bernoulli's equation and rearranging,

$C_p = 1 - 4\sin^2\theta$

However, let's assume we don't want to use potential flow derivations, but just resolve the free flow vector into $V_r$ and $V_{\theta}$. In that case, we get

$V_r = U\cos \theta$

$V_{\theta} = -U\sin \theta$

where does the discrepancy come from? Why does the potential flow solution give double that of a resolved vector? Where does the extra $R^2/r^2$ term come into play when we try to resolve it directly?


texts: Is the young's modulus of a braided rope stronger than the sum of its parts?

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I know that if I have a thin rope of Young's modulus Y, then getting n of these ropes and holding them in parallel gives a Young's modulus of nY.

If I was to braid/weave them, does this affect the Young's modulus?


texts:
I recently saw a wind turbine that I'm trying to identify the type or category of.

Basically, the turbine looks like two squirrel cage fans mounted side by side on a fairly tall ~40' pole.

The blades of the turbines rotate along the horizontal axis of turbine.  Essentially, they work like paddle-wheels of a steamboat.  There are shrouds in front of the blades to direct the airflow, which obscures the view of the blades themselves.

Note, rotational direction may be in the opposite direction of what's drawn.

I'd like to know name of the type or category of this type of wind turbine as I would like to research it some more.  Most of the images and types I was able to find so far have been the "windmill" style turbine with a central housing and 3 or 4 blades coming off of the center.


texts: DC brush geared motor: coast vs brake effects on motor/gearhead lifespan

texts: I'm dealing with an application in which I use small DC brush geared motors to move a robot. The motors are driven by a standard FET driver. I do have the option to coast or brake the motor after every operation. Brake would be preferable since the robot would stop directly after a "forward" or "backward" operation. What I'm wondering is: would the brake operation affect negatively the lifespan of the motor or gearhead? Or is this effect negligible?


texts: Single linear actuator lifting mechanism

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I have inherited a DIY build and I have some doubts about its design. Have a look at the following diagram:

1 is the linear actuator. It's quite beefy 2000 lbs 12" stroke. It is installed in an aluminium channel.
4- Is a carriage, essentially a box section with little rollers on all sides, so it has no play within the channel and moves quite smoothly. This is connected to the actuator's rod.
3. Is a flat steel bar that links to an identical channel (2) and carriage assembly, though this doesn't have an actuator in it.
The system is supposed to lift a max 220 lbs load that is evenly distributed along the bar.
My questions are:

While there don't seem to be any bending forces to the actuator itself, is it a safe design, as far as longevity of the components goes?
is there anything I can do in channel 2 to support the system, e.g. a spring at the bottom, etc. to address any design problems?


texts: Optimum spoke shape for wheels made of solid material

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Currently I am designing a bicycle sprocket to be laser-cut out of 3mm steel. Steel is heavy, so I want to make some lightening cut-outs, and I want to optimize the shape of the cutouts. I will probably make a "spoked" type of pattern to the cutouts.
The question is: given a certain % of material to remove from the sprocket, and ignoring cost considerations, what is the optimum geometric pattern to make the cut-outs? Consider a planar sprocket that is loaded in a planar direction with minimal side-loads.
How much material I can remove from the sprocket, while still leaving sufficient strength, is application-specific, and that can't be answered here. My question here is, is there any general optimum pattern for such wheels made out of solid material? In designing my sprocket, I may as well try to use the optimum morphology, then I can optimize the amount of material removed by testing. But I don't know what the optimum morphology is. What are the trade-offs of various patterns of lightening cut-outs, that is to say, what is the optimum "spoke pattern"? This is an extremely common engineering problem but I never learned it in school.
In the bicycle and motorcycle marketplace, we see all kinds of variations on the types of lightening holes in bike sprockets, wheels, and brake rotors. The driving force is probably aesthetics as much as engineering. There doesn't seem to be a consensus on the number of spokes or the pattern.

Sometimes there are round holes. This is probably done for economy because round holes are easy, but with laser cutting, there is no cost advantage to round holes.
Sometimes there is a spoke pattern. Maybe 4, maybe 6 spokes, maybe 10...what is the optimum number of spokes?
In the case of spoke patterns, especially for braking discs, sometimes the spokes are "swirled" in an apparent attempt to transmit torque by tension. The swirling direction is opposite between the bicycle and motorcycle markets. Does this swirling serve any purpose, or does it just add weight compared to "straight" radial spokes of the same cross-section?
Sometimes the pattern uses bifurcated spokes which branch out like tree branches from the hub to the "rim".

Since wheels and sprockets are a very common type of thing, I am hoping there is some rules of thumb on the best design (defined as stiffness vs. weight) for such spoked wheels. I heard once, in the context of car wheels, that  a supercar manufacturer did research on car wheels and found that 5 bifurcated spokes was the optimum pattern, but I have no reference. Also, car wheels are loaded laterally whereas sprockets are only loaded in-plane.
Also, it seems to me that clock gears are very similar to bike sprockets in being essentially planar and loaded in-plane, and they usually have 5 (or is it 4...) spokes in them, and the spokes are typically straight and not swirled, but for some reason, balance wheel spokes are sometimes swirled. But I don't know the engineering reasons for all of it.
Here's a bicycle brake disk, with "leading"-swept and reverse bifurcated spokes.

Here's a motorcycle brake disc, with similar spoked pattern, but the spokes are swept the opposite direction. Is there an engineering reason for sweeping the spokes opposite direction? Or sweeping at all compared to a  straight spoke pattern?

Here's a clock gear with radial spokes. This one has six spokes. Others have only 4. What is is the tradeoff for more vs. fewer spokes?

Here's a sprocket with round lightening holes.
https://images.app.goo.gl/FHiKCdeEJooJZvHGA
Here's a car wheel (slightly different case than a planar sprocket) with bifurcated spokes
https://images.app.goo.gl/FM2tgP78VHqq1M4v9
It seems common for antique cast-iron wheels to have spiral or wavy spokes. Is there a reason...maybe the wavy spokes actually are more durable for some reason?
https://images.app.goo.gl/boBemdRrjd4S2hvH9


texts: Is this railway carriage side likely made of single metal sheet?

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A neat image from Wikipedia:

Here the railway carriage side looks like it is crafted from a single sheet of metal (if we ignore the doors and the windows and some minor parts like that small thing near the carriage number) - no seams, no rivets, no anything just a 20+ meters wide and about 3 meters tall single sheet of metal.

Is it indeed possible and reasonable to craft a carriage side of such large single sheet or should I expect that there're neatly hidden seams somewhere?


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I was reading an article on the impact of jet in vanes. In this article I found that the net torque on the unsymmetrical or radially curved vanes is non zero.
But, my question is that, why the torque on the symmetrical curved vane, when jet impinges tangentially at one end, is zero.
My thoughts: As the force on the symmetrical vane, for the case described above, is in the horizontal direction only and the net force in vertical direction will be zero, if no losses are considered. Hence, the line of action of horizontal force is finite distance apart from the axis of the vane. Therefore, net troque must be finite.
Note: this picture is only meant to define the sense of horizontal and vertical directions only and the axis of the vane and not the other terms which can vary according to the user.


texts: Why is the direction of pressure always perpendicular to surface area for fluids?

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Why is the direction of pressure always perpendicular to surface area  of a body for fluids ? We also assume that it is an ideal fluid here.
So , pressure acts in all directions because fluid has a tendency to flow.
Now , in book it says that for a block in water. Pressure must only act perpendicular to the surface  area of block because otherwise , there is no friction between adjacent layers of the fluid.
Also ,pressure must act in perpendicular direction on the sides on the tub if a block  is put  inside a tub which has water contained in it.
How does pressure being perpendicular does not cause that. How can we prove that pressure always act perpendicular in this way.
Also , in real life. This law must not be valid right since it only for making calculations easy? Is that true so.


texts: What are those large poles for that are always in front of US stand-alone store buildings?

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Screenshot of a video where they are featured in the background:

They appear to have no electronics built in, such as an electric charge station, or a parking ticket dispenser or something like that.

They appear to just be large, solid metal poles that are roughly placed with one per parking space in front of the store.

Are they a safety measure? So that nobody can drive like a madman into the store? Is that really so common as to have them waste all that money on "safety poles" everywhere?

Are they meant for bicycles to lean against them? For people to hang out in that area? Resting against them? Are they purely ornamental? Are they considered aesthetically pleasing?


texts: How to derive Equivalent Static Load for irregular structure modeled with FEM?

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Building codes such as the Uniform Building Code (UBC) or International Building Code (IBC) require the determination of Equivalent Static Lateral Forces in order to compute $P-\Delta$ effect and to perform checks on the structural design.

However, all these overturning moment computations and structural checks are done (in the building code) assuming a lumped mass model (a cantilever column). But what if the structure is irregular? How can we compute the  Equivalent Static Lateral Forces in an irregular building/structure discretized by finite element?

These quantities have clear physical meaning in a cantilever column, but may not even necessarily have clear meaning/clear equivalent in an irregular building.

I am looking for the FEM way of computing equivalent static forces that act on global level. Any ideas?

To illustrate why I need FEM version of Equivalent Static Load: consider that the overturning moment is defined as $M_o=F_xh$, where $F_x$ is the lateral load at floor level, and $h$ is the distance between the top floor to the point where overturning moment is calculated.

consider $P-\Delta$ checking ratio:

$\frac{P_x\Delta}{V_xh_s}$

where

$P_x$ is the total unfactored gravity load at and above level $x$

$\Delta$ is the seismic story drift by seismic forces

$V_x$ seismic shear between level $x$ and $x-1$

$h_s$ sotry height below level $x$

Consider also accidental torsional effects ( EC8 example, section 2.5.3, pp 39)

$M_t=F_xe_y$

Where

$F_x$ is the equivalent lateral static force in $x$ direction

$e_y$ is the accidental eccentricities

Take note that all these involved quantities are evaluated on floor basis.

But if we do FEM seismic dynamic analysis, then all I get is the forces for each node, not at each floor. So we need to be able to resolve FEM seismic nodal forces into floor forces.


texts:
I have invented something and I need to have some external broaches made but I'm being asked for some dimensions I simply do not understand.

I need 4 external broaches. They all have the same major diameter 7.6 mm. They all have an angle of 90° between each spline. I do not need any radius in the root between the splines and the peaks can be sharp too. I need spline counts of 18, 20 24, and 28.

I am told by the toolmaker they cannot programme their machines until I give them numbers relating to pin diameter and a distance between pins.

I've Googled till my fingers bleed but nowhere can I find a definitive answer to the dimensions I need, how to work it out or even to describe what these things are and their relevance.

Hope the attached helps]2


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I have been trying to solve the problem below involving a concrete anchor block subject to two equal horizontal forces.
Normally I would just apply the force as a moment acting about the centroid of the concrete block which would produce a linear bearing pressure distribution at the base. Adding the self weight of the block as a compressive bearing pressure and I would then have an idea of the complete bearing pressure distribution.
Am I missing something?
taking moments about the centroid with the forces turned into vectors via the position vector and using the cross product only gets me so far.


texts: Lift-type identification - What class of lifts are ferris wheels in?

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I am looking to build a specific kind of lift for a project I'm working on but I don't know the name.  I am willing to hire a mechanical engineer to help me design and build it (or buy one if it already exists) but I'd like to do as much research as possible before deciding on the next steps.

What I have in mind is like a ferris wheel, save that it is shaped more like a stretched rubber band than a circle (i.e. it has vertical sides and a short circular path at the top and bottom).  Instead of carts that people sit in I'd just like a flat steel floor, say 4'x8', for loading cargo.

Using a switch I'd like the flat "carts" to move into a loading space, load from the front, then be sent up to make room for the next cart.  Maximum load should be about 1,000lbs per cart.

What is this type of device called?  I know similar things have been built for parking cars, but I don't want something quite so large and I'm interested in storing smaller things than cars.

I'm sorry if this isn't more descriptive, please ask if I can clarify anything and I'll be happy to.


texts: Heating the air inside a turbojet instead of combusting it

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Would an aircraft that uses propellers for movement but with a turbo jet like structure where the ignition chamber only heats the air a bit, similar to a hair dryer instead of releasing fuel and combusting it have any impact on the speed of the craft?

Would it just act like a normal propeller or will the aircraft get a little faster?


texts: Given a car configuration with a length of L and width of W. If you can give the top left wheel an angle of A to turn A degree how do you derive the angle of top right wheel for turning . I know that the bottom left angle will just be complimentary of the top left wheel and bottom right wheel is complimentary of top right wheel. This is a swerve drive system so i can control each wheel angle.


texts: When a valve under pressure is closed and creates a seperate cavity. What happens to the pressure in the seperate cavity?Will it leak out over time?

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The image below shows a common technique for working on valves in the petroleum industry. A secondary valve 2 is closed and allows servicing of Valve 3.

My question is about the blue area. What is the pressure in this area after the valve has been closed? Does it stay at 10,000 PSI? I opened Valve 3 after some time and some liquid spewed out at a safe velocity. I was told by a technician that the pressure trapped in the blue area is safe, and that it will diminish even further if you allow it to sit for more time. I though that pressure could be contained for a reasonable amount of time in such a setting. I thought that we rely on the ability to contain pressure in storage tanks for example. I thought that storage of something pressurized would be possible in a valve setting like this. The technician said it is not possible and that he know first hand from experience. Is this technician wrong? Where does the pressure go?

I have reasoned that it is related to energy and I have come up with a similar thought experiment to explain this phenomenon. I have a pipe with closed ends and many springs pushed together in series contained within the pipe. I also have a device similar to the bladelike one a magician uses when he does the magic trick to cut off peoples limbs in a box. I use a device like this and slide it into the pipe and I isolate only the last spring in the pipe. When I open the end of the pipe, only one spring comes out with limited energy. If I had opened the pipe without using the blade like isolation device, then many springs would have sprung out with incredible energy. Is this a sound comparison and understanding of the concept?


texts: Search for comprehensive term for plants with heat generation with heat storage and operating states

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My master thesis deals with systems with several operating states that generate heat and store it in a heat storage. Thereby I analyze combined heat and power plants with combustion engines, but also heat pumps.

Now I am looking for a comprehensive term for such systems in my thesis and in the title. The term "heat generators" seems a bit too simplified to me.

Are there any more specific alternatives for a comprehensive term that might also point to the heat storage tank and the limited number of operating states?


texts: Relation between links and pairs in Kinematic chain

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I came across a equation for kinematic chain (for lower pairs only) :
L = 2P-4
where L: Number of Links;
P is the number of pairs
how could this equation be derived ?
EDIT: I tried putting values in the equation.Since for the pairs to be any integer the links can only be an even number(can be verified from the formula).
FOR

L=4 ; P=4
L=6 ; P=5
L=8 ; P=6

Question 1:How to visualize kinematic chain with (6links;5 pairs) or (8L;6P)(with the help of diagram)
Question 2: Why is it the number of pairs not equal to number of links and why is it decreasing gradually from the number of links ?
Question 3: When closely observing the equation i can see that 2 pairs are neglected (P-2) and each pair has 2 links attached L =2(P-2).But why and which 2 pairs are neglected? Is this the correct way to think about this equation?


texts: Difference between Variable Speed Compressor and Variable Speed Condenser(Fan controlled)?

texts: Are these pieces of equipment independent from each other, or one requires also the other one to be in a system (chiller)?


texts: I was thinking about the relationship between water hammer and expansion waves. Pressure seems to drop across a surge wave travelling at the speed of sound in water hammer (after the fluid has been initially brought to rest by a compression). Pressure also drops across an expansion wave (e.g. a rarefaction fan). I know they are not the same, but my question is - "is the wave travelling at the speed of sound in water hammer more like an expansion rather than a compression (or is it the other way round)?"


texts: Find correct dimensions from mechanical drawing

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I'm designing an electrical component into a CAD from the manufacturer drawing. The version I'm interested to is the code 106166-1 (6 positions, last entry in the table).

I'm not sure to understand the drawing about the following dimensions:

overall width of the connector
distance between any row of pins and the case

Width of the connector
I see two different ways to calculate it:

D * 2 + 0.240'' = 0.452''
C + 0.040'' * 2 = 0.412''

But as you can see they are different values. And I don't understand what does "3 places" mean (under 0.040'', on the right of C ref).

Distance between rows and the case
I can't see any actual measure of this. Only observing the drawing it seems the inner row is placed adjacent to the case, hence the center of the pins should be at diameter / 2 (0.015'' / 2) from the case.

Would you please help me to understand the right approach to find those values?


texts: How to prototype this circuit using an Arduino and breadboard?

texts: I'm trying to build this circuit for a force transducer such that the data is logged by an Arduino Uno. I have the op-amp recommended in the schematic, but I haven't been able to get stable readings from the transducer. I've attached the schematics for the force transducer and op-amp, as well a picture of my attempt.


texts: Why do I get pushed back when I’m in a car at high speed?

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When I’m in a car at high speed , I get kind of like pushed back if I’m sitting on the cars seat. How does it happen and why ?
If I’m in a car , then I have the same speed as car and for the car , I am at rest. How is it possible I am getting pushed back which means I have some acceleration. Isn’t it wrong ?
I checked on internet and they it happens only when the car is accelerating. Even though it is accelerating , still , so is the person in the car and therefore  , he should not get pushed back.


texts: Unachievable motions because of singular Jacobian

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This is the Jacobian of a robot arm (IBB IRB 120) with already specified joint angles (0,0,0,0,0,0). This Jacobian is singular for this configuration.

J =
[       0,    17/50,    7/100, 0,      0, 0]
[ 187/500,        0,        0, 0,      0, 0]
[       0, -187/500, -187/500, 0, -9/125, 0]
[       0,        0,        0, 1,      0, 1]
[       0,        1,        1, 0,      1, 0]
[       1,        0,        0, 0,      0, 0]

What motions are unachievable with this specific configuration? How to find that out conveniently with MATLAB?


texts:
I have an STL file, all I want is to be able to measure dimension from point A to point B on the model in the file. How can I do this? I do have access to Solidworks but don't know if that the best software to do this.

Thanks


texts: Find frictional losses as box exits ramp

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I have a box traveling on a ramp just before the ramp levels out. At this point all values are known:

I want to calculate the frictional losses from this point to when the box is completely off the ramp and level. The picture below shows the box in the middle of this process and the forces I think that apply:

The problem I am facing is that the normal forces and frictional reaction forces change depending on where the box is during this process. I don't know how to write an equation that accounts for this. I am assuming this is a completely inelastic collision and that all energy is transferred horizontally.
I feel that some calculus is needed, and that an equation for both contact points would be in respect to the angle AND either the displacement along the x axis or ramp surface. I need help in creating these equations.


texts: Will multiple lines off same water main have equal pressure?

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I’m in a situation where a multi unit structure under construction will receive its water from local municipality via three metered 5/8” lines.

We’d like to combine all of the lines into a 3” horizontal main. The question is, can we assume that all three lines would have equal pressure, since they originate from the same water main? The concerb is that our volume would be reduced if any of the lines have lower pressure.

Any suggestions are appreciated.


texts: More efficient to use LED lighting than to open blinds for light and thereby lose heat when very cold outside?

texts:
Currently here it is 9 degrees Farenheit.  My home is heated by electric resistance heating (not a heat pump, just plain heating coils).  Am I correct in believing that it's more energy efficient to keep our wooden blinds and curtains closed and turn on LED lighting than to open our blinds and curtains for light?
Our windows are double-paned.  My local utility says it's better to open the windows than turn on an LED light, but I can't believe that's true under current conditions.
My belief is:
Loss of heat due to opening blinds and curtains * electricity needed to replace that heat via resistance > electricity needed to power LED lights (say 8 watts per window).
NOTE:  This is when the sun is not shining directly in thru the window.  Direct solar radiation can be very heating, as detailed in an answer below.


texts:
I am reading thermodynamics from Cengel and Boles. I am currently studying flow work. The following image contains text of the book:

The work done is calculated by considering the pressure of upstream fluid but the downstream fluid also applies pressure on it,but that is not considered why? According to me,the work done should be (P2-P1)*V where P2 is pressure of fluid upstream and P1 is pressure  downstream at the boundary of control volume.


texts: Meshing Error near Leading and Trailing edges

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I am trying to mesh the propeller geometry in the Ansys meshing tool. At the leading and trailing edges of the propeller, mesh goes out of boundary. I did a geometry check of the CAD model in SolidWorks, and I don't seem to find any error. Please have a look and suggest what changes can be done?
I have attached some screenshots.


texts: What metal thickness and/or type is needed to support 100kg load?

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I'm making a prototype that will have some load cells mounted approximately where the arrows are pointed in the image. The prototype will hold up to 100kg of load/force in the marked location thus I need to fabricate a frame with the correct strength to not bend or flex too much under load. I want to achieve this without welding and only bending 90-degree angles out of a sheet of metal to make the frame to the right in the attached image. The frame will be mounted to a wall, so the load is applied approximately 50mm or 2 inches out from the wall itself.

What grade of steel/metal and thickness do I need to achive this? Or how can I calculate this? Or maybe you guys know of a software I can use to calculate or simulate it?


texts: Why aren't driving roads also illuminated from the ground up, like airport runway lights?

texts:
Compared to its Mar 2016 article, the Nov 29 2018 article by the  Insurance Institute for Highway Safety proclaims that "headlights improve, but base models leave drivers in the dark" and are dreadfully too dim. Picture is from NPR.

Just over half of 2018 model vehicles IIHS evaluated are available with headlights that do an adequate job of lighting the road at night and limiting glare for oncoming drivers, but most good-rated headlights are optional or bundled with features that can raise the price of the vehicle.

In addition to overhead lights, why not illume (not a typo. I'm using this for it's shorter) from the ground like airport runways do?

Such outdoor lighting can be recessed into the ground, to further prevent any collision between vehicles and the light bulbs.


texts: Rocket vs aeroplane? Difference in take off?

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Although both aeroplane and rocket burn fule and eject smoke but
Why aeroplane moves and runs horizontally before take off ?why does not it takes off at its original/initial place just like rocket?


texts: How does a rodless electrical linear actuator work?

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I want to pull some weight horizontally and for that i have settled for a linear actuator.

The actuator should pull some weight as it moves back and forth as the gif shows.

There are linear actuators i could find but they are too bulky with heavy motors and a lot of lubrication and the noise they make is not music to my ears.

I found electrical actuators to be a perfect fit but i do not know how they work for instance this actuator: R4 Series


texts: Seeing through walls and noninvasive structural integrity metrics

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Walking into a building, how does one find out where the pipes are, how strong the walls are (currently) and other key structural integrity measures?

without breaking walls or utilising harmful-to-human emmissions (e.g.: strong x-rays)

Some ideas I have (mostly from geophysics and medicine):

Get floor-plan and other information from maintenance folk
Magnetometer to detect metal and current decay
Sonar—possibly infrasonic; but more likely ultrasonic; e.g.: synthetic aperture sonar—to figure out location and density of objects through the walls. (they may of changed since plan was written)

Palpation for more obvious (but less objective) measures.
Tonometry could objectively be applanated  across a larger area.
Electrical impedance tomography could be used for this also.
Alternatively some other kind of tomography


texts: What causes friction in magnetic bearings?

texts:
Magnetic bearings work by levitating a rotating shaft so that it is not in contact with its supports. This greatly reduces the friction of the system.

In all of the literature that I have seen on magnetic bearings, the bearings are described as "low friction" and not "no friction".

Wikipedia

  ... they do not suffer from wear, have low friction ...

Synchrony

  ... they do not suffer from wear, they have low friction ...

Steorn

  ... A low-friction bearing ...

Calnetix

  ... extremely low friction and wear ...

It would seem that there wouldn't be any friction since the magnets are keeping the rotating shaft from touching anything.

Where does the friction come from in magnet bearings?


texts: Understanding transformer secondary winding

texts:
I purchased a step down transformer from a junk yard. I tested the transformer and it works but I am confused as to the secondary winding.

The primary side has these markings
G 0V 100V

The secondary has these markings
37V 18V 0V 6V 0V

On the secondary the markings
37V 18V 0V are all connected.

The 6V and 0V on the right hand side are connected as well.

When I connect the transformer and try to take readings from the secondary, I get mostly 6-8V between any two points on the secondary.

Visual

      Primary
    G 0V 110V
------------------
------------------
     Secondary
 37V 18V 0V [space] 6V 0V

Anyone have any idea what's going on with this transformer?


texts: How do I correctly model this system of torsion springs?

texts:
I am currently designing a symmetric parallel mechanism that can be modeled as follows:

Here, $\tau^j$ denotes actuator moments and $k_i$ are torsion springs constants. For a specific point in the workspace of the system, the actuator moments as well as the torsion angles $\varphi_i^j$ are known. It is of interest to determine possible sets of torsion spring constants $\mathbf{k}$ that would result in the torsion angles $\boldsymbol{\varphi}$, given the actuator moments $\boldsymbol{\tau}$. The links can be assumed rigid.

In other words, I am looking for the relationship between the actuator moments, torsion spring constants and torsion angles when the mechanism is in static equilibrium.

My current approach is to look at the total energy of the system. Since the potential energy of a torsion spring is $$ U = \frac{1}{2}k\varphi^2 = \frac{1}{2}\tau\varphi, $$ the total energy of the system in static equilibrium can be written as
$$\frac{1}{2}(\tau^1\varphi_1^1 + \tau^2\varphi_1^2 + \tau^3\varphi_1^3) = \frac{1}{2}(k_1(\varphi_1^1)^2 + k_1(\varphi_1^2)^2+k_1(\varphi_1^3)^2+k_2(\varphi_2^1)^2 + k_2(\varphi_2^2)^2+k_2(\varphi_2^3)^2+k_3(\varphi_3^1)^2 + k_3(\varphi_3^2)^2+k_3(\varphi_3^3)^2)$$
or
$$ \sum_{j=1}^3\tau^j\varphi_1^j = \sum_{i=1}^3\sum_{j=1}^3k_i(\varphi_i^j)^2. $$

Is this the right way to model this system, or is my approach omitting some important observation?


texts: Does a joist have to lay "thin side" down?

texts:
As a complete novice, I have been reading about outside engineering projects such as decking and patios.

All the information I read tells me that to lay structural joists as a subframe / sleeper joists, the joist should be positioned with the thin side down, the wider side running perpendicular to the ground.

From my understanding, this makes for a stronger frame which can take more weight. My question is does it have to be this way? For example, if the goal was to create a lower deck, is it structurally sound for the joists to be laid "wide side" down?


texts:
I am trying to design something for a friend, but am struggling to come up with the mechanics. Can you help?
So imagine a long extendable pole, like a bow staff. Imagine after pulling out a "peg" the bow staff extends using springs. Now say I wanted to automatically close this extended pole. What would be a good way of doing this?
My idea is a wire/string inside the staff that runs from the top to the bottom. Pulling this wire can compress the staff. In my head, some kind of motor can wrap up the string to compress the staff. My worry is that the motor wouldn't be able to pull against the strength of the springs. Can this be solved through a gear mechanism allowing the motor to be safe from the resistance of the springs? If so, how?
My second idea is to eliminate the motor. Instead, the wire is simply pulled from the bottom to compress the staff. But I wouldn't want to pull the string the entirety of the bow staff. Potentially through some pully or gear system, a semi-short pull of the string can compress the entire staff. Like the string would only have to be pulled out half or a quarter of the distance of the bow staff, but still, compress the entire thing.
Which method is more doable? Is there a better way to automate the compression of the staff?
This is only in the planning stages so springs are not chosen, though their strength will be similar to that of the springs used inside an umbrella. Here is a picture that should provide some basic dimensions. Fully extended, each section is about 13cm. The inner diameters are 9.5mm, 6.5mm, and 3.5mm.

I look forward to hearing your answers. I don't have a lot of experience with gears which is why I am asking. Thanks!


texts:
I'm using an engineering software based on Autodesk AutoCAD 2018 OEM and I need to assign keyboard shortcuts to NumPad keys directly, without any modifier (SHIFT, CTRL, ALT).

On older version of Autocad this was possible, but now even though it's possible to assign NumPad keys directly, they do not work. According to this page on the AutoCAD LT knowledge base: "Valid modifier and key combinations include Number Pad (NUMPADn) keys containing no modifiers" and I hope the same is true for the "standard" AutoCAD (i.e. no "LT").

In fact I'm able to assign a shortcut to - for example - "Scale" function to NUMPAD(8), as in the screenshot below:

But then I'm not able to use it because if I press the NumPad 8 with Num Lock ON the AutoCAD console reads an 8:

... and if I keep the Num Lock OFF then the console picks the previous command (as it's the same that pushing the ↑).

So if this feature is documented and the cui AutoCAD command allows me to choose that keys, how are they suppose to work? How can I assign a key to speed up my work without using a modifier?


texts:
I am currently working on a huge industrial process for a student project and we need to transfer around 25MW of energy between dozens and dozens of streams, some larger and some smaller ones. Many even with gas/gas exchange, and those tend to get quite large fast.
I was wondering if there was a general rule of thumb to determine if the investment for a heat exchanger is worth it in order to save on operating costs. Something like, "don't build liquid/liquid exchangers for less than 250kW and gas/gas for less than 500kW" something along those lines. Any ideas?


texts: Heating circuit - help me understand control scheme of return temperature

texts:
I'm looking at a P&ID of a heating circuit.  The burner/boiler is non-modulating. Red is flow/hot, blue is return/cold. AFAIK the pump is fixed speed (no FI).

As far as I understand the control logic, the temperature sensor on the return line (or rather the control circuit it's a part of) will open the three way valve and mix hot water into the return, and close when the return flow temp is warm enough. The boiler delivers a constant $\Delta T$, controlling for return temperature ensures that the flow temperature is correct.

Is this control scheme likely?
Why not control for flow temp. directly?


texts: Use of sleeve bearings for linear motion

texts:
I am designing a system wherein an assembly has to be moved up and down( 4 inches) at regular intervals ( every 5 mins) using a Linear Actuator. I wanted constrain the DOF and ensure that the entire assembly moves straight up and down( 1-2 degree misalignment is acceptable). The entire assembly is a cantilever and Hence, I wanted to have some bearings to restrict the moment and ensure straight vertical motion.The weight of the entire assembly is about 50lb and the distance from the support frame (for cantilever) is about 7 inches.

Hence, is it okie to have sleeve bearings(Red color in picture below) (Ultra-Low-Friction Dry-Running Flanged Sleeve Bearings from McMaster:  http://www.mcmaster.com/#standard-sleeve-bearings/=11vp8eo ) which serves as a guide for the motion

In the above Image, the fixed frame is rigid and the moving assembly( in light pink) slides on the sleeve bearing carriages attached to the fixed frame( in dark pink color)using the guide block attached to the moving assembly( in green). However, since it is a cantilever I want to provide additional support at the other end .Cost & compactness is a factor for me in this design , so are normal sleeve bearings( in RED color- ultralow friction ) good for support the assembly at the other end .


texts: What is the difference "maximum" shear stress and shear stress

texts:
Shear stress is introduced in statics as $\frac{P}{A}$.

However, the maximum shear stress with neutral axis is different.  It is $\frac{3P}{2bh}$ (Where $b$ is width and $h$ is height)

What is the difference between these concepts?


texts: How is prestressing with losses self-balanced?

texts:
By definition, prestressing is a self-balanced load. This is because it is in fact merely an applied state of internal stresses.

This can also be demonstrated mathematically (in this case for a simple parabolic cable) via Lin's load-balancing method.

For a cable which follows the layout given by
$$ y(x) = \dfrac{4e}{L^2}x^2 $$
where $e$ is the vertical distance between the maximum and minimum points of the parabola, $L$ is the span of the cable, and $x=y=0$ is located at the minimum point of the layout, the equivalent load is
$$ q = \dfrac{8Pe}{L^2}$$
where $P$ is the prestress force.

Therefore, the total vertical load given by the distributed load is $\dfrac{8Pe}{L}$.

This force is countered by the vertical forces applied at the anchors. These are equal to $P\sin(\theta) \approx P\theta$ and $y'(x) \approx \theta$, so the forces are each equal to $Py'\left(\frac{L}{2}\right) = \dfrac{4Pe}{L}$ and combined are equal (and opposite) to the total distributed load. So the total global load applied is null.

Now, what if we consider friction losses between the cable and the duct in a post-tensioned beam? Then the combined forces at the extremities remain equal to $\dfrac{8Pe}{L}$, but the total distributed load will be reduced by the losses, implying in a non-balanced load, which is impossible.

This may be adjusted by the anchorage slip losses, but what if we assume a hypothetical anchor which doesn't slip? Is this impossible and slippage is necessary to make the load balanced?

And how are the remaining losses (elastic deformation, creep, shrinkage and relaxation) affected?


texts: How to calculate heat generation on 2D plate?

texts:
I have a 2D plate with heat source at one part and I need to calculate the heat generation. The plate is made of aluminum (k = 212 W/m°C). I have watched this example video, but I'm not sure if I can apply it to my case. Some data:

Length of the plate: 1 m
Width: 1 m
Surface being heated: 0.16 m^2
Tmax = 500 °C

The heat source is placed in the center of the plate and the boundaries of the plate are insulated.

I want to find the heat generated as in this example, equation (4). You can see Q is being divided by ρcp and thus the units of Q must be W/m3.


texts: I am having problem with the application of Saint Venant principle.I have heard that quite often we use that knowingly or unknowingly.I would be very greatful to anyone who would explain this very explicitly to me.


texts:
Consider a system made of a cylindrical column (fixed on the ground) with a mass attached on top of it (B). Both the mass of the column and the mass are not negligible. Depending on the value of the mass I could have self-buckling of the column. What I would like to compare is the natural frequency at the top of the column as a function of mass and presence of self-buckling.

1) If there isn't self buckling, then I can compute the natural frequency of the column+mass system as a cylindrical cantilever (still don't know how, but it seems standard).

2) If I have self-buckling, the column bends and I expect the system to have a natural frequency around the z-axis due to system symmetry (in red). Is that true? How can I compute that frequency?

I need help especially for "2)". Any reference/help for "1)" is appreciated.


texts: How to calculate a gas burner dimensions?

texts:
I am trying to calculate the dimesnions of a natural gas burner for a hospital. The burner will be heating water. I have calculated the thermal duty that needs to be produced and the water mass flow, but I haven't found equations that will allow me to calcuate any characteristics of the final construction.
My approach so far is treating the burner as if it was a gas CSTR. The problem is that I havent really found any literature doing the same thing, so I doubt that this apporach is right.
Does anyone know of the relative literature for my problem or has to suggest any tactic I should use?


texts: How to compare multiple data acquisition systems?

texts:
For an application of displacement measurement under 1 kHz, I have 3 options to choose from. The application is automotive. Unfortunately I don't have deep electronics knowledge and the catalogues contain so many abbreviated expressions in the names of their connectors, etc.
What table of comparison in parameters would you suggest to classify them as best and to also justify them with my needs in this frequency range?

The temperature range is up to 1000°C.
The movement range is ±50mm
Frequency : automotive range but let's say 1 kHz..
bolting can be the solution due to the temperatures.

I also have seen a table like this, but I would like to widen it to more parameters :


texts: How to distribute moment from Lateral Load Method (Static Analysis IBC for example) to Each shear wall individually?

texts:
I have used the Equivalent Lateral Load Method from the IBC code to distribute forces and moments on each storey (level) but what I need to know is how to distribute the moment on each shear wall.

This maybe a stupid question, but I'm just a student. Do I distribute the force & moment on each storey to each shear wall individually or do I distribute shear &


texts: Why were pneumatic thermostats commonly installed in buildings?

texts:
According to Wikipedia, pneumatic thermostats were invented after electric thermostats.

Yet this article claims that "at least 25 percent of U.S. commercial buildings are served by pneumatic controls, according to the U.S. Department of Energy".  I would guess that they were even more popular in the past.

This seems surprising.  Why set up an air compressor system and run pneumatic tubes through the walls?  Wouldn't an electric system be easier to set up and maintain?

What were the factors that made pneumatic thermostats so popular?


texts: What is the mathematical derivation for shear center of a beam?

texts:
For me, it's a bit hard to imagine where shear center can be, and what purpose it serves. The definition I found online is very vague:

  Shear center is defined as the point on the beam section where load is
  applied and no twisting is produced.

Given the general profile of a section, is there a proper mathematical derivation/formula that shows how the shear center is defined/derived?


texts: Is it better ASTRA 19.2°E or 28°, in central continental europe?

texts:
I'm trying to tune my satellite receiver, particularly to receive the signals of the Astra satellites, which are ASTRA 19.2E and ASTRA 2 at 28º East.

Looking at the picture the signal from ASTRA 28 should be focused on the UK (red circle which encloses Great britain) and ASTRA 19° on central europe (blue square).
What I observe in Italy, is the opposite: I receive a signal of 72% power strength from ASTRA 19 and of 92% from ASTRA 28°. How is that possible?


texts: Would the volume of water usage change if we increase water pressure using a booster pump? Not changing pipe diameter, length or viscosity

texts: This is for a clean up crew, I am wondering if we do not change our hose size, nozzle size on the sprayer.  The pressure out of the water heater would be 65psi and they want to add a booster pump to go up to 90 psi.  Would they use more water in the same amount of time with the increased pressure?  I am trying to see how to calculate to see if I need a bigger water heater/storage tank.


texts: How to find Ship Transverse Metacentic Height

texts:
I did a Civil Engineering course some years ago and from my textbook I had this question. I found that a very interesting question, but unfortunately I haven't been able to find a solution to this.
I encourage people to put comments up, but ideally I would be appreciative if the comments are related as to how you do the calculation process to get to the answer.

The half ordinates of the contour of the load water plane of a ship of 2,800 metric tons displacement, measured at intervals of 6 m, are 0.30, 3.33, 5.07, 6.18, 6.75, 6.90, 6.75, 6.18, 5.61, 4.47, 0.60 m respectively.
If the centre of gravity is 1.87 m above the centre of buoyancy, calculate the transverse metacentric height.
Sea water has a density of 1,025 kg/m^3.

Also, just wondering how you would best Explain the relation between metacentre and curve of buoyancy as vessel heals over.


texts: flexing operation fails when structure is too long

texts:
I have a linear repeat such  that for up to  11 repeats, the  flex operation works perfectly.  for 12 and  more, the operation goes haywire.  is there an alternate way of doing it that avoids this problem?
the operation  is as follows:
this is the operation for 11 repeats (works perfectly)

this is what I get for anything beyond 11 repeats:

the basic patern is as follows:   it is first linearly repeated (up to 11 times, apparently), then circular patterned around an axis, then the flex (twist) operation is applied.

edit:  it has been suggested to use weldmets.  I'm now getting the hang of this,  but it still has problems..  ..sigh..  my order of operations:


texts:
Cathode ray tubes (CRT) are analog addressing displays because you can light a point on its surface applying a continuous electric or magnetic field to deflect electrons beam. Virtually, there is no limit on the resolution that CRT can reach. On the other hand, TFT-LCD, for example, are digital displays because you can only light discrete points of its surface. Moreover, you are limited to a fixed set of points, so resolution is limited and fixed.

Are there any technologies (old and new) that allows an analog addressing of a flat panel display with no fixed resolution? For example, a thin film of electroluminescent material between two continuous (versus discrete addressing lines in common displays) electrodes that allows addressing any point of its surface with analog signal without the need of an intermediate analog-digital conversion.


texts: Can lamda sensor 4.9 be used without the special LSU-IC?

texts: I was looking into using Lambda Sensor LSU 4.9  to know the lambda value. From the datasheet, its looks though this sensors cannot be used without a special IC such as Bosch lambdatronic LT4. Can we get any information out of the sensor by connecting only 12v to the heater+ and heater-. What would be the minimum circuit to get some information from this sensors?


texts: Internal Diameter or External diameter measurement?

texts:
I would like to know if there is a definite way to understand what kind of diameter is indicated on the dwg by just looking at a dwg. I work in a job profile where I need to add inspection points to these measurements and the device used to inspect it. Most times I get confused if its an internal diameter measurement (using a gauge pin) or an external diameter (using a micrometer). Recently there was a sectional drawing with a cylindrical figure inside and there was a diameter measurement with tolerance shown. I assumed it was an external diameter measured using micrometer. But was corrected that its an internal one to be measured by a gauge pin.
Thanks,
VRij


texts: What materials that can contain water and ultrasound wave can go through

texts:
Currently, I'm studying about Ultrasound wave. My aim is set up a system that ultrasound wave can go through ( not reflect and not absorb ultrasound wave). Besides that, this material can contain liquid.
Can you give me what materials can adapt this experiment?
Best regards.


texts: Natural frequencies of an orthotropic bending beam with circular cross-section

texts:
I am trying to find an expression for the natural frequencies of an orthotropic bending beam with a circular cross-section. I have tried searching for some literature on this, but have so far been unsuccessful.

For an isotropic bending beam, I believe the natural frequencies can be written as

$$ f_n = \frac{n}{2L^2}\sqrt{\frac{EI}{m}}, $$

where $L$ is the length, $E$ is the Young's modulus, $I$ is the area moment of inertia of the cross-section about the neutral axis, and $m$ is the mass per unit length.

Is there an equivalent expression for an orthotropic beam? i.e. one that has a different Young's modulus in the $x$ and $y$ direction say. Therefore it would have different values $E_x$ and $E_y$.

The reason for this is I am considering a circular beam made out of wood. Hence, it has different values of stiffness along the grain and across the grain.

If there is an expression for the natural frequencies of a circular orthotropic beam, I want to be able to show that if $E_x$ and $E_y$ are equal, the expression should reduce to the isotropic case.


texts: Steering with a push / pull action. Is there an easier way?

texts:
Linked to my previous question Push / Pull Steering on an axle, I now have time and space to work on the full scale project. I have noticed an issue with the answer that is there, and that is, the vertical shaft is not at a 90 degree vertical, and cannot be adjusted.

Here's what the shaft looks like:

As you can see, that is not a perfect vertical, meaning that it would be near impossible to mount a push/pull motor as shown in the answer to my previous question.

Here is another picture of the front axle:

My current plan is to build a platform that leans at the same angle to the "vertical" shaft, and then use the answer from my previous question, but this would make the project rather tall and difficult to transport.

I also tried removing the lever that is connected to the axle and the shaft, and mounting the push/pull moter directly onto that, but there was not enough room to get a good angle through the gap for a good steering range.

Does anyone see a better approach than building a platform at the same angle as the "vertical" shaft?


texts: How is the drilling done along the axis for a typical synchronous motor shaft?

texts:
I was looking in google, but I did not find any information on how the drilling was done, I would appreciate it if someone who knew how it was answered. As typical it could be an axis of 200 [mm] in diameter and a hole of 24 [mm]

Thank you!


texts:
I was looking over practice problems for an upcoming exam and I am struggling with root locus. I understand how to plot the basic root locus but for some of the aspects when gain is asked to be calculated for plots I'm stumped.

I was wondering if anyone knew a good step by step method to solving something like this?


texts: How much weight has weight in fuel efficiency?

texts:
Comparing the official fuel efficiency figures for several cars, I was surprised to discover that the Smart Fortwo has a weight between 750 to 800 kg and needs 4.3 L/100 km, but the VW Polo with a weight of 1650 kg reaches 3.8 L/100 km. That is, the Smart has half the weight, but still a worse fuel efficiency.

When driving up and downhill (but not on a flat surface) does one cancel the other? That is, driving uphill with more weight costs more fuel, but you need less fuel when going downhill.

Are the major fuel efficiency improvements rather on other places, like better tires, better injection, better streamlining and hence lower weight cannot outweigh poor performance in these fields?


texts:
Usually a hinge looks like this. And pretty straightforward.

[![Example of a hinge design][1]][1]

We are trying to develop something where I add steps, and I control the angle adjustments in those steps. Lets say 15deg, and a total of 90 degrees usage.
Let's say a monitor, you can tilt it around 15-30 degrees in one dimension, similarly, the application is to basically limit the angles to 6 in the step of 15 deg. So the user decides 0,15,30,45,60,75,90 deg (max)

By adding notches like you had mentioned, would it not restrict the motion backwards?

What kind of mechanism will be used. My guess is a rachet has to be there.
But I can't seem to get the design in my head, nor any other product which has this.
Also for a tight clearance, I think 0.05mm would do, right?

Thanks to Ethan I have a name for it. Detent hinges are a viable option.
But I am afraid if it will add a lot of time to design a new one. Or if it should be picked up.

I checked a few of the designs. I did not really understand the working of it.


texts: Trasmitting data from pressure transducer to phone/web server

texts: I am creating a 24 hour blood pressure monitor that is designed to be sleek and comfortable, I have decided on The Honey Well Series NBP AN transducer (see more info here: Basic Board Mount Pressure Sensors, p13) I want to connect that to a board so that the data can be transmitted wirelessly, or by cable to a phone or computer, how would I go about doing that?


texts: I understand that the lead ions can be rendered into a precipitate with chloride ions in water treatment, but why on earth does the U.S. still use lead pipes at all when contamination poses an enormous risk?


texts:
I'm finding myself doing quite a lot of thread cutting in stainless steel lately, particularly 304 and 316, often these are moderately deep threads ~ 25 mm or so and at M12 it is becoming a bit of a chore. I'm using a decent tap wench and cutting oil with carbon steel taps (taper, second cut and finishing/plug) but I was wondering if anybody has any experience or knowledge of any ways to make this a bit easier eg by a different tap material or coating.

I'm not doing enough volume to justify any major investment in tooling as this is all prototype work but it's that difficult area of a dozen or so at a time.

Also it is specifically stainless which is the problem and these are stressed welded components so free machining stainless isn't really an option (as far as I know) and I do appreciate that this is a bit of a 'how do I have my cake and eat it' type question.

The main issue is the taps getting progressively tighter, I haven't broken any yet but they often feel like they are getting to the point where they might. I generally start the taps off in a lathe (not under power) with a sliding chuck in the tail-stock so I'm fairly confident that they are going in pretty square.


texts: How much torque do I need to lift 1,000 pounds?

texts:
So, I have a 1,000 pounds load.

What would be the required torque in inch/pounds to lift that load for a motor?

If the motor is installed at the center of the radius generating that torque, does it matter how long the radius is if the end requirement still 1,000 pounds load?

Would the answer be 1,000 in-lbs?


texts: How does ATM determine the card is inserted the right side?

texts:
Whenever I happen to try to insert the card into the slot in the ATM wrong side - be it upside down, or backwards - it goes maybe 2cm in, barely past the plastic shield, and is mechanically stopped. The ATM only "swallows" it when inserted the right way in.

This is way before the chip interface enters the slot. Maybe a centimeter of the magnetic strip enters as well - if there even is one. NFC/RFID might work with determining the end of the card, but seems unlikely to help with the side, never mind older cards with no "contactless payments" feature.

HOW does the ATM determine the orientation of the card?


texts: my team is working on a project where fluid (mostly water) need to be pushed through small channels (like small pipes) in order to reach larger reservoir. We were considering using air to push the water but we fear that the water will simply  bubble through the water. Does anyone have any advice on how to work around this to move the water through the channels?


texts: Calculating Anisotropic Thermal Conductivity for two Materials

texts:
I've been working with SC magnet quench simulations. The conductor is made from NbTi in a Cu channel with a 5:1 ratio of Cu:NbTi. Opera3d has a quench program with an example that I began working from. In a quench scenario using a solenoid made from the conductor I described above heat propagates at different speeds throughout the bulk of the solenoid. For this case, heat conduction along the conductor (azimuthal) is fastest. Axial and radial propagation are much slower, with radial being the slowest.
Opera's documentation documentation has the following description regarding the anisotropic thermal conductivity:

Nonlinear anisotropic thermal conductivity properties are defined by three expressions based on the functions Cu_Kappa(T), Bulk_Kappa_r(T), and Bulk_Kappa_z(T).
For the azimuthal thermal conductivity of the bulk material,the conductivity of copper, Cu_Kappa(T), will be scaled by the copper factor. It is assumed that this is significantly higher than the conductivity of NbTi and dominates the thermal conduction in this direction. The bulk properties radially and axially are to be taken directly from the tables of measured values. (Note that the data used in this example are fictitious, but with similar characteristics to real materials).

So, the values used in the example are claimed to be taken from measured values.
My question is this: Can I create the radial and axial thermal conductivities from the thermal conductivities of NbTi and Cu along with their proportions in the conductor?
Here is what I've done so far in trying to find the answer:

Google searches. There are many articles and web pages which describe anisotropic $\kappa$. But all the information I've found assumes you already know the $\kappa$ values.
Hand calculations. I made the following model and tried to think of the problem in terms of thermal resistivity, which I then assumed I could treat like electrical resistances, i.e. use rules for parallel and series resistance to calculate the effective resistance.

There is one more piece to this, however, and that is the insulation. Around the unit cell there is polyester insulation. It is 0.27 mm and 0.25 mm thick the edges that run in the axial and radial directions, respectively.
I am going to try accounting for this by summing the materials in their respective direction, each scaled by a packing factor.
Does this sound like a good approach? I've spent a bit of time on this already and have no idea if the answer to that approach will resemble the physical model.