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12
votes
3answers
430 views

Exploiting fluid dynamics for the optimal design for gas mixing in a furnace

Background This is the standard design for a thermal furnace used in the Clauss process, which converts H2S to SO2. The main problem with the furnace is that gas mixing is rather poor and results in ...
12
votes
1answer
5k views

At what point does an I-beam becomes a H-beam?

According to BS5950, a beam section can be classified as plastic, semi-compact, compact or slender. For the same section area, a H-beam can take axial compression (without buckling) better than an I-...
12
votes
1answer
450 views

What causes the sound coming from electrical vehicles?

All the electrical vehicles I've ever ride make that humming sound (either cars or trains). What exactly causes that sound? Is it drag force in the gears? Is it a fan? Or is it because of the coils (...
12
votes
2answers
8k views

How long does it take for dust to settle out of the air?

In order to make this a manageable question, let's add a few simplifications. The dust particles can be well described as uniform spheres of radius $R$ and density $\rho$. The space is enclosed ...
12
votes
4answers
5k views

How do I calculate the forces on a desk and its legs?

I have a design for a desk, and I'd like to not just guess at how strong it'll be, but I can't find an explanation on how to figure out all the forces involved that doesn't assume I already know a lot ...
12
votes
2answers
1k views

What is the difference between aeronautical and aerospace engineering?

Every time I search for "aeronautical engineering" on Google I see a few results about aerospace engineering. So they must be similar, but what is different about these careers?
12
votes
2answers
426 views

Does a Faraday cage effectively act as a notch filter?

In reading about Faraday cages, I have found that most "real world" designs incorporate multiple layers of mesh. For example, this article from the National High Magnetic Field Lab discusses several ...
12
votes
3answers
2k views

Schematic Diagrams for Mechanical Systems

Is there some sort of equivalent standardized schematical (topological) diagram -such as Piping and Instrumentation Diagram, Electrical Schematics, Process Flow Diagrams, etc.- for the realm of ...
12
votes
1answer
2k views

Detailed dimensions of an aircraft engine compressor blade

I am working on rub-induced vibrations in compressor stages of aircraft engines. The work is carried out in partnership with a company, therefore there is a limited amount of it that could be ...
12
votes
1answer
281 views

Replace mercury with silicone oil in diffusion pump

We have obtained an old mercury-vapor diffusion pump for high vacuum. However, we do not want to operate it with mercury in our lab due to health concerns (which is presumably the reason it was ...
12
votes
1answer
398 views

Is steel relaxation plastic?

Hooke's Law defines a linear-elastic relationship between stress and strain. $$ \sigma = E\epsilon $$ Steel behaves very much like a linear-elastic material, following Hooke's Law closely. It does, ...
12
votes
1answer
2k views

Insufficiently constrained structural model in Ansys

I want to analyze this model that is stressed and deformed. I fixed the lowest of points in the x, y, and z directions, and I pulled top of points upward (y direction). When I run the model in Ansys I ...
11
votes
3answers
4k views

Why would a bearing plate that further concentrates load onto small surface be used?

Here's a photo of a bearing plate where a bridge reinforced concrete beam meets the earthfill The bridge span is about 20 meters long and consists of two reinforced concrete beams each resting on two ...
11
votes
7answers
14k views

Why do we use multiple reinforcing bars instead of one bar with a big diameter in reinforced concrete?

Why do we use multiple reinforcing bars instead of one with a big diameter in reinforced concrete? Does increasing the number of reinforcing bars means that the reinforced concrete will have a higher ...
11
votes
3answers
12k views

Defining the heap and stack size for an ARM Cortex-M4 microcontroller?

I have been working on and off on small embedded systems project on and off. Some of these projects used an ARM Cortex-M4 base processor. In the project folder there is a startup.s file. Inside that ...
11
votes
5answers
3k views

Practical setup to measure angular velocity

I have got a spinning top from a Canadian manufacturer, and I am deeply amazed by how neatly it spins. My interest in physics has led me to try to find out at what top speed I can spin the top and ...
11
votes
2answers
2k views

What is the mechanical element that holds a worm gear shaft in place called?

Here is an image of a worm gear. What is english word for mechanical element (two of them will be necessary for a worm gear) in which the worm shaft will "lie" and rotate? Here is one photo of the ...
11
votes
2answers
965 views

Would a “lifting body” design be useful for a train car?

Lifting Body The idea of a lifting body design is to shape a vehicle's body in such a way as to produce lift without wings. Research has shown that this can be an efficient method of reducing drag ...
11
votes
3answers
1k views

Thermoelectric Technology to Harvest Energy from Internal Combustions Engines

Background: In an automobile, only 1/3 of the potential energy in the fuel is converted into mechanical energy and significant portion of the energy is lost as heat. There have been previous ...
11
votes
5answers
5k views

How is lift related to airspeed?

Lift produced by an airplane wing is related to airspeed - this much is clear; a plane moving too slowly will stall. But what is that relation? Linear? Quadratic? Exponential? I don't need the exact ...
11
votes
3answers
5k views

What makes the material travel through Archimedes' Screw?

...or in other words, why doesn't the material just stick to the screw, rotating in place, without progressing along its length? In the simplest case, the answer is obvious: gravity. If it's a ...
11
votes
3answers
2k views

At what temperature do I risk altering the structure of steel?

If I have structural or tool steel that has been treated to some standard (ASTM, SAE, ISO -- e.g., for hardness) but I don't know the details of the treatment, is there a "safe" temperature below ...
11
votes
2answers
3k views

Why was a coil chosen over a straight for this overbridge?

I saw this meme on Facebook showing a coiled railway overbridge and an alternative plan. I replied that straightening that overbridge will force it to start at the other side of the road, and you need ...
11
votes
4answers
2k views

Why does column buckling occur when the load is parallel to the column?

I'm studying Euler's work on structural engineering from a book out of curiosity and it is mentioned that he developed a mathematical theory describing the buckling of columns under a parallel load (...
11
votes
2answers
3k views

Buckling: Do buckling mode shapes of n > 1 occur in reality?

In the buckling of columns we know that: $$P = \dfrac{n^2\pi^2EI}{L^2}$$ The smallest value of P occurs when $n=1$ which gives a simple buckling shape (one wave): $$P_{cr} = \dfrac{\pi^2EI}{L^2}$$ ...
11
votes
2answers
4k views

Why are tremors of an earthquake felt more on upper floors?

Why are tremors of an earthquake felt most on the upper floors of a building in comparison to lower floors? Does this have something to do with a third class lever?
11
votes
3answers
1k views

Why do beverage can tabs break when bent?

Most people have had the experience of moving the tab of an aluminum can back and forth until it breaks off. It usually only takes a few complete back and forth motions before the tab breaks off. ...
11
votes
2answers
4k views

Do structural engineers carry insurance for catastrophic errors?

A friend of mine is a structural engineer and he often complains to me about how little sleep he gets at night worrying over whether or not he accounted for all the little details involved in his ...
11
votes
2answers
4k views

What does the steel grade “11SMn30” mean?

I am starting to use steel in some of my designs, and while trying to learn more about this material and its properties I have realized that there is so much more to it than I thought. How does the ...
11
votes
2answers
363 views

Is a chair with N+1 wheels ever less stable than a chair with N wheels?

My workplace has a policy to provide standing desks upon request, but no policy to provide chairs of matching height. (I work for the government...) We can buy our own, or build our own. However ...
11
votes
3answers
542 views

How different is using styrofoam rather than empty cans when pouring concrete?

In the recent 6.4 earthquake that hit Taiwan, it was seen in a newswire photograph of rubble that metal cans were embedded in the concrete. The quote from an official regarding this practice: For ...
11
votes
1answer
605 views

Avoid snapping an electric cable from too much rotation

I recently built the basic construction for a crane out of lightweight material. Basically the head of the crane contains an electric servo motor which spins the head of the crane by pushing itself ...
11
votes
4answers
1k views

Determining Drill Speed

How are spindle speeds calculated for a drill bit? I've seen dozens of charts that highlight the rpm that should be used for specific drill bit types, bit diameter, and material. However, what if my ...
11
votes
3answers
38k views

How to determine the characteristic length in reynolds number calculations in general?

I understand that the reynolds number is given by the expression $Re=\frac{\rho v L}{\mu}$, where $\rho$ is the density, $v$ is the fluid velocity and $\mu$ is the dynamic viscosity. For any given ...
11
votes
1answer
807 views

How can Pareto Analysis help solve engineering problems?

Attach is a Pareto Diagram with Number of Defects in Y-axis vs Causes in X-axis for an engine overheating problem. How can this Pareto diagram help an engineer solve the engine overheating problem? ...
11
votes
1answer
5k views

How do Thumb instructions compare to ARM instructions for performance?

A colleague mentioned that Thumb instructions were significantly slower than ARM instructions (this was for an AT91SAM7S32 processor). Is this true? What are the performance benefits of one ...
11
votes
1answer
997 views

How does a microbolometer (IR camera) work?

I am currently doing a project which has led me to my first encounter with IR cameras, and I am therefore quite curious as to how they operate. Specifically, I would like to know the following How is ...
11
votes
3answers
1k views

What kind of protection should I give structural steel in a natatorium (swiming pool) environment?

What would be the best type of steel to specify? Would a heavy galvanization suffice? Are there specialty paints/coatings available for this particular application? If so, how long do they last?
11
votes
2answers
217 views

How accurately are moveable span bridges balanced?

Movable span bridges (bascule and lift) typically employ a counterweight to help reduce the amount of energy and size of motor required to move the span. Due to variations in the the construction of ...
11
votes
4answers
3k views

Would an object at the bottom of the sea still experience buoyancy? [closed]

So I understand that buoyancy happens because the fluid exerts larger amounts of pressure from beneath an object compared to above, like in this picture So my question is, what if the object is ...
11
votes
3answers
415 views

Why are mass-produced metal parts machined by rotating the part against a stationary tool?

There's a TV programme called "How It's Made" which often shows automation of mass-produced machined parts. Very often, it seems that metal parts are machined (especially drilled) by rotating the part ...
11
votes
1answer
187 views

Has a specific type of alternative intersection been shown to reduce congestion & accidents?

Localities in the US have different road layout and setups. For example the Michigan Left, Jersey Left/Jug Handle, vs a standard 4 way stop with left turns at the intersection. Have any of them come ...
11
votes
2answers
101k views

Calculation of Clamping force from bolt torque

I'm trying to calculate the clamping force resulting from torquing a nut and bolt to a particular level. I have found this formula in various forms in a lot of places. $$T = KDP$$ $T$ = Torque (in-...
11
votes
1answer
670 views

How fast should I sample with a logic analyzer?

If I have a 10 MHz digital signal, how fast do I need to sample with a logic analyzer to avoid any bit errors? Does the minimum sample rate increase if I want to attach a protocol decoder (e.g. SPI)? ...
11
votes
3answers
3k views

Should I reject a concrete mix design for having too high of a compressive strength?

I usually design precast concrete members for the common concrete strength of f'c=4,000 psi at 28 days. Occasionally, a mix design will be submitted that has a very high strength. In one case, the mix ...
11
votes
1answer
912 views

How to determine the lateral earth pressure in a double-walled cofferdam?

The design of a retaining wall commonly involves determining the lateral earth pressure using either Rankine theory or Coulomb theory. Both theories involve mobilising the shear resistance of a ...
11
votes
2answers
816 views

How are wind tunnel models used when designing supersonic aircraft?

There are two things involved: wave drag and boundary layer separation. The wave drag depends on the Mach number while the latter depends on the Reynolds number of the flow. It's easy to maintain the ...
11
votes
2answers
267 views

How do I solve an optimal control problem where the law of motion depends on some function of the state vector?

A typical optimal control problem with state vector x(t) and control vector y(t) can be expressed as: $$\max_{x(t), y(t)} \int_0^{t_1} f(t,x(t), y(t)) dt$$ subject to $x'(t)= g(t, x(t), y(t))$ and ...
11
votes
2answers
413 views

Foiling vortex traps around buildings

I have had three houses with right angles in the layout, and in each one that configuration causes vortices to form that suck in leaves, snow, and any debris blowing by and keep it in the nook of the ...
11
votes
1answer
1k views

How to calculate Power of motor when used as a generator?

How can you calculate how much power can be generated by a motor when used as a generator (like a motor used in a wind turbine)? Does the power depend on how fast the magnet is rotated? If so, is ...

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